List of Abstracts

Alumina (Al₂O₃) is a widely used advanced ceramic due to its exceptional thermal stability, mechanical strength, and chemical resistance; however, traditional subtractive manufacturing of complex, near-net-shape dense alumina parts remains challenging and costly. Direct Ink Writing (DIW), also known as robocasting, has emerged as a prominent additive manufacturing technique that relies on the extrusion of highly loaded colloidal suspensions, offering precise control over geometry while minimizing material waste [1]. The purpose of this comprehensive review is to synthesize current advancements in the fabrication of fully dense, defect-free alumina structures using DIW. Specifically, this paper evaluates the critical transition from ink formulation to the final sintered component, aiming to establish clear correlations between processing parameters and material performance. Methodologically, this review aggregates and systematically analyzes recent peer-reviewed literature focusing on rheological optimization of aqueous alumina inks, the mechanics of micro-extrusion, and the effects of varying post-printing sintering profiles, including as two-step and vacuum sintering, on microstructural densification [2]. The reviewed literature demonstrates that formulating highly loaded aqueous alumina suspensions with tailored pseudo-plastic behavior and optimal yield stress is essential to prevent structural slumping and ensure rapid shape retention upon deposition [3]. Furthermore, the collected studies indicate that optimized sintering processes successfully mitigate abnormal grain growth, consistently yielding dense Al₂O₃ ceramics with relative density greater than 98% and mechanical properties comparable to conventionally pressed counterparts [4,5]. Ultimately, this review concludes that while DIW is a highly viable and scalable method for manufacturing robust alumina components for advanced structural applications, future research must address persisting challenges related to green-body drying stresses and the standardization of multi-material printing protocols.

Zirconia (ZrO₂) is a highly demanded advanced ceramic due to its exceptional fracture toughness, biocompatibility, and high wear resistance, making it ideal for structural and biomedical applications such as dental restorations [1]. However, traditional subtractive manufacturing of fully dense zirconia often results in significant material waste, high tool wear, and difficult to manufacturing products with intricate geometries. Direct Ink Writing (DIW), an extrusion-based additive manufacturing technique, offers a compelling solution by enabling the precise, layer-by-layer deposition of highly loaded ceramic pastes. The primary purpose of this review is to present a comprehensively evaluate of the current state of DIW technologies applied to dense zirconia processing, among ink formulation, micro extrusion mechanics, and post-printing sintering protocols. Methodologically, this paper systematically analyzes recent peer-reviewed literature to investigate the rheological requirements of aqueous and non-aqueous zirconia suspensions, highlighting the precisely controlling dispersant and binder ratios [2]. The review examines the impact of various debinding and sintering cycles on final microstructural densification, alongside innovative hybrid techniques, such as UV-curing-assisted DIW, developed to mitigate persistent challenges, such as drying-induced warping and cracking [3]. The review showed that precise control of zirconia ink rheology is essential for fabricating complex green bodies with excellent shape retention. Subsequent optimized high-temperature sintering yields defect-free components that frequently exceed 98% relative density and exhibit mechanical properties, such as flexural strength and fracture toughness, comparable to or even superior to those of conventionally pressed ceramics [4]. Even multi-material and/or compositional gradient prints are possible, as demonstrated by the development of bilayer zirconia ceramic blocks with 3Y-TZP and 4Y-PSZ layers through double extrusion 3D printing [5]. Ultimately, this review concludes that while DIW is a robust and scalable method for manufacturing fully dense zirconia, future research must continue to standardize defect-mitigation strategies and explore multi-material integration to unlock its full industrial and clinical potential.

Several procedures are used in the development of biomaterials for dentistry applications. The aesthetic quality of the biomaterial has been a concern. However, alterations to biomaterial composition must be carried out carefully to avoid deleterious effects on the environment when the materials are discarded after use. The incorporation of metallic nanoparticles into dental materials has emerged as a promising strategy to enhance functional properties. This procedure has potential aesthetic effects that remain a critical concern in orthodontic applications. This study aimed to evaluate the influence of copper nanoparticles (CuNPs) on the color properties of a resin-based composite used for orthodontic attachments. Small amounts of nanoparticles were added to the resin. Different concentrations of CuNPs and specimen thicknesses were analyzed. Disc-shaped specimens were prepared using a commercial resin composite modified with CuNPs at concentrations of 0.05% and 0.075% (wt%). The control group was a sample without nanoparticles. Samples were fabricated with thicknesses of 1.0 mm and 2.0 mm to analyze the influence of optical properties. Color measurements were performed using a spectrophotometer based on the CIE Lab* system, and color differences (ΔE) were calculated. The results demonstrated that the incorporation of CuNPs led to measurable color changes compared to the control group, with higher concentrations promoting greater ΔE values. This behavior can be attributed to the intrinsic optical properties of copper nanoparticles, including increased light absorption and scattering within the resin matrix. Additionally, specimen thickness significantly influenced color outcomes, with 2 mm samples exhibiting higher opacity and greater color variation due to increased light attenuation along the optical path. These results indicate that both nanoparticle concentration and material thickness play a key role in determining the optical performance of resin composites. Although copper nanoparticles offer potential functional benefits, their impact on color must be carefully controlled to ensure aesthetic acceptability in dental applications and to avoid environmental impact upon disposal after use.

Oropharyngeal squamous cell carcinoma (OSCC) exhibits a rising global incidence, particularly driven by human papillomavirus (HPV) infection, which acts as a distinct etiologic agent with specific genotypic heterogeneity influencing tumor biology and clinical outcomes. This study prospectively investigates HPV-positive and HPV-negative OSCC patients at Brazilian Cancer Hospital I/INCA, Rio de Janeiro. The aim is to correlate specific HPV genotypes with cytopathic effects—such as koilocytosis, nuclear hyperchromasia, and multinucleation—across different tumor stages. We evaluate the efficacy of exfoliative cytology combined with an expanded molecular genotyping approach (Multi HPV Flow Chip, XGEN®) capable of detecting 35 HPV genotypes. This methodology represents a significant advancement over conventional programs limited to types 16 and 18, potentially reducing false negatives and enhancing diagnostic precision. Samples are collected using sterile brushes for the preparation of smears, which are subsequently fixed in 96% ethanol and submitted to Papanicolaou staining for cytological analysis. In addition to the brushes, oropharyngeal swabs are collected for genotyping. Molecular detection is performed via PCR and reverse hybridization. Preliminary analysis of eleven samples has already identified morphological changes consistent with viral cytopathic effects. We anticipate that high-risk genotypes (notably HPV-16 and 18) will predominate, while also addressing the role of multiple subtype coinfections in tumor behavior. The validation of these cytological findings through specific genotyping highlights exfoliative cytology as a minimally invasive, cost-effective, and precise tool for early OSCC detection. This research provides crucial insights for targeted surveillance strategies and personalized therapeutic management, ultimately aiming to improve patient prognosis and quality of life in the context of public health oncology.

Some cutting instruments used in various surgical, medical, and dental procedures can be reused. Professionals should analyze disposal methods and the possibilities of reusing instruments without compromising the procedure, thus minimizing environmental impact. It is essential to analyze the type, shape, and application of surgical instruments to assess their feasibility for reuse. Surgical instruments, such as forceps, scalpels, bone chisels, scrapers, and surgical drills, are commonly reused. There is a protocol for handling, cleaning, and sterilization of these instruments to prevent the transmission of pathogens and infections between patients. Single-use instrument kits have a greater environmental impact than reusable ones. Environmental impacts encompass greenhouse gas emissions, water consumption, and the use of natural resources. In the present work, the possibility of reusing a cutting instrument named Micro Blade Tunnel [1], commonly used in periodontal plastic surgeries, and drills used to prepare the site for dental implant placement was analyzed [2]. The instruments were to be properly cleaned, decontaminated, and inspected before each use. The naked-eye analysis showed no changes in the instruments' physical integrity after multiple uses. The analysis of all instruments using a scanning electron microscope revealed only slight wear and surface-roughness modification. Naked-eye inspection is an inadequate procedure for identifying small defects on the instrument's reused surface. During osteotomy to prepare the site for dental implant placement, bone heating can occur, compromising osseointegration. During dental implant insertion site preparation, the surgeon must control the drill rotation speed, the compression force, the irrigation, and the instrument's cutting capacity to avoid overheating the bone. The electron microscopy analysis showed that the drill, after up to 48 uses and sterilizations, did not exhibit signs of wear, corrosion, or heating at temperatures considered critical for inducing bone necrosis. It is possible to conclude that the Micro Blade Tunnel can be safely reused up to three times. Drills can be used up to 40 times without compromising the surgical procedure. It is concluded that environmental considerations are relevant when making decisions about materials and devices used in dental and medical surgery practice.

ABSTRACT

Facial bones, especially the zygomatic bone, play a fundamental role in protecting stomatognathic structures against impacts and in dispersing masticatory forces [5]This work aims to analyze the mechanical properties and structures of cortical bone as an inspirational model for the development of sustainable, high-toughness-tenacity biomaterials. Bone is a hierarchical composite with good mechanical properties and fracture toughness, whice are enhanced, in part, by hindering the nucleation and propagation of cracks. [6][8] The literature indicates that the bone fracture toughness is high due to its anisotropic structure and characteristics. Bone has transverse orientations that increase resistance to crack growth by about five times compared to longitudinal orientation. Osteons increase crack deflections. [8] These biological characteristics can be used as strategies for the mimicry and development of ceramic and polymeric materials, as well as scaffolds. Osteons absorb the energy of the crack, thereby increasing fracture toughness. [4] In addition, the application of functional gradients in bio-inspired laminates allows for the optimization of material use, reducing waste without compromising resilience in critical impact directions. [10] It is concluded that based on the concepts of fracture toughness and the structure of facial bone, it is possible to develop materials for clinical use to replace the use of natural bone in cases requiring grafting.

Resin composites are the gold standard for direct dental restorations, and their market has expanded to encompass conventional (micro-hybrid, nanohybrid, and nanoparticulate), flowable, and bulk-fill categories. Pre-heating of resin composites prior to cavity insertion has gained clinical popularity, as elevated temperature is thought to reduce material viscosity and enhance monomer conversion during photoactivation, theoretically improving mechanical performance. However, the literature lacks systematic, multi-brand comparative studies that rigorously assess the impact of pre-heating across different commercial formulations and simultaneously benchmark modern flowable composites against conventional resins under identical test conditions. The assumption that thermal pre-conditioning universally improves mechanical properties has not been adequately challenged.

This study aimed to evaluate and compare the flexural strength and degree of conversion (DC) of three conventional resin composites: Empress Direct (Ivoclar Vivadent), Palfique LX5 (Tokuyama Dental), and Tetric N-Ceram (Ivoclar Vivadent), and three flowable resin composites: Tetric N Flow (Ivoclar Vivadent), Beautifil Injectable XSL (Shofu), and Grandioso Flow (VOCO),  investigating the effect of a standardized pre-heating protocol (69°C, 15 min) on the conventional resins. The central hypothesis was that the thermal effect is brand-specific rather than universal, and that modern flowable composites are mechanically competitive with pre-heated conventional resins.

Ninety bar-shaped specimens (25 × 2 × 2 mm; n = 10/group) were fabricated according to ISO 4049:2009 and divided into nine experimental groups: three conventional resins at room temperature (control), three pre-heated conventional resins, and three flowable resins. Pre-heating was performed using a wax-heating device maintained at 69°C for 15 minutes immediately before specimen preparation. Photoactivation was performed with a high-power LED unit (Bluephase, Ivoclar Vivadent; 1200 mW/cm²). Specimens were stored in distilled water at 37°C for 24 hours prior to testing. Flexural strength was assessed by three-point bending (Instron 5560; 0.5 mm/min crosshead speed). Degree of conversion was determined by Fourier-Transform Infrared Spectroscopy (FTIR; Spectrum 100, PerkinElmer), monitoring the aliphatic C=C peak at ~1636 cm⁻¹ relative to the aromatic reference at ~1608 cm⁻¹. Statistical analysis employed Two-Way ANOVA (brand × heating interaction) for conventional resins and One-Way ANOVA for flowable resins, with Tukey post-hoc test (α = 0.05). Pearson correlation was used to assess the DC–flexural strength relationship.

Pre-heating produced significant, brand-specific effects on flexural strength, confirmed by a significant brand × heating interaction (Two-Way ANOVA, p = 0.0234). Tetric N-Ceram showed the greatest response (+31.3% increase in flexural strength; +20.6% in DC), Empress Direct demonstrated a moderate response (+16.4%; +25.5% DC), while Palfique LX5 exhibited minimal change (+4.5%; +4.4% DC), suggesting its formulation is already optimized at room temperature. Pre-heated Tetric N-Ceram achieved the highest overall flexural strength (176.26 ± 7.49 MPa). Flowable resins showed mechanical performance statistically equivalent to pre-heated conventional resins (p = 0.6358) and superior mean DC (66.0 ± 5.2%), challenging the traditional paradigm of their mechanical inferiority. A positive, significant, though moderate correlation was found between DC and flexural strength (Pearson r = 0.3312; p = 0.0014), with DC accounting for approximately 11% of flexural variance, indicating that matrix composition, filler type, and inorganic load fraction are equally or more influential determinants of mechanical performance. These findings refute universal pre-heating protocols and support evidence-based, brand-specific material selection strategies.

The success of endodontic treatment depends on the effectiveness and safety of the chemomechanical preparation of the root canal. A key factor that significantly enhances safety during instrumentation is the use of the glide path methodology (the creation of a free, safe, and anatomical pathway from the coronal orifice to the apical foramen), as it promotes controlled progression of instruments within the root canal. In this context, cutting ability is a relevant property, as it is directly related to preparation efficiency. Endodontic instruments that exhibit favorable mechanical properties, such as flexibility, fatigue resistance, and buckling resistance, allow clinicians to operate with greater predictability and a higher likelihood of clinical success. Additionally, the type of kinematics—whether continuous rotary or reciprocating motion—directly influences preparation efficiency and the reduction of risks such as instrument fracture or deformation during root canal instrumentation.

The thermal treatment of nickel-titanium (NiTi) alloys significantly affects their mechanical properties and should therefore be considered an important variable when evaluating the performance of endodontic instruments. The aim of the present study was to assess the mechanical, structural, and surface properties of NiTi endodontic instruments. Tests conducted included surface roughness, bending, buckling, fatigue resistance, cutting ability, and thermal characterization using Differential Scanning Calorimetry.

The results obtained indicate that the performance of the evaluated instruments is directly related to the interaction between surface morphology, geometry, metallurgical characteristics, and motion kinematics.

Commercially pure titanium (CP-Ti) has been widely accepted as a prominent metallic standard for dental implants and protheses. Indeed, decades of research and practical applications demonstrated that CP-Ti has remarkable biocompatibility associated with the ability to osseointegration as well as resistance to corrosion due to mouth fluids [1]. CP-Ti is preferred over other titanium alloys in many situations because it lacks elements like aluminum and vanadium related to potential cytotoxicity as well neurotoxicity. This work presents an updated review of research works and relevant technological results on the advantages of using CP-Ti as dental replacements and substructures. It also disclose possible difficulties. In particular, the role played by existing impurities in the titanium matrix, such as carbon, is evaluated and a comparison with other metallic alloys is discussed [2]. A final prediction of future advances and eventual restrictions regarding the use of CP-Ti in dental implants and protheses is proposed.

Peri-implantitis is an inflammatory disease associated with bacterial colonization and biofilm formation around dental implants and prosthesis, potentially leading to progressive bone loss and implant failure. Biomaterials capable of preventing bacterial adhesion while maintaining biocompatibility are of growing interest in implant dentistry. Sodium alginate-based formulations have attracted attention for this application. The mixture of alginate with molybdenum trioxide (MoO₃) has demonstrated promising antibacterial activity. This study aimed to develop and characterize an experimental sodium alginate-based varnish containing molybdenum trioxide nanoparticles for potential application on the implant collar as a strategy to prevent and manage peri-implantitis. Additionally, the influence of hydroxypropyl methyl cellulose (HPMC) on the formulation's physicochemical properties was investigated. Three formulations were prepared: a control varnish, a varnish containing MoO₃ nanoparticles (S1), and a varnish containing both MoO₃ and HPMC (S2). Preliminary characterization included rheological analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD), and surface roughness assessment on Grade V titanium discs coated with the formulations. Future studies will include bacterium adhesion testing in accordance with ASTM D870 and ASTM D3359, contact angle measurements, and cytotoxicity evaluation in accordance with ISO 10993-5:2009. Rheological analysis demonstrated shear-thinning behavior for all formulations. The incorporation of MoO₃ reduced viscosity and improved reproducibility, whereas HPMC increased viscosity and structural stability. SEM analysis revealed a homogeneous coating for the control group, while MoO₃-containing formulations exhibited localized accumulations and increased surface irregularities, particularly in the presence of HPMC. XRD analysis confirmed the crystalline structure of the titanium substrate and identified MoO₃, although its peaks were limited, suggesting a low concentration or partial amorphous dispersion within the varnish matrix. Surface roughness measurements indicated a reduction in roughness parameters after varnish application, which may contribute to decreasing bacterial adhesion and biofilm formation. These preliminary findings suggest that sodium alginate-based varnishes containing MoO₃ represent a promising strategy for implant surface protection, although further optimization and biological validation are required.

The increasing disposal of textile waste has stimulated research focused on the development of sustainable materials for biomedical applications, particularly polymer composites intended for orthopedic engineering. In this context, recycled fabrics incorporated into epoxy matrices have attracted considerable interest due to their combination of low density, mechanical strength, and reduced environmental impact. Recent studies have demonstrated the applicability of natural fibers and textile waste in structural composites for prosthetic devices [1–4].

Oleiwi et al. [1] investigated laminated composites for prosthetic sockets reinforced with flax and cotton fibers in a polymer matrix. Stochioiu et al. [2] evaluated the mechanical behavior of flax fiber-reinforced epoxy composites subjected to cyclic loading and creep recovery. Alves et al. [3] explored the valorization of textile waste in nonwoven structures and sustainable composites, while Kitila and Wolla [4] developed hybrid flax- and sisal-fiber-reinforced epoxy composites for prosthetic socket applications.

The present study aims to evaluate the mechanical feasibility of epoxy matrix composites reinforced with a single layer of denim or linen fabric for eco-friendly orthopedic applications. Composite laminates will be manufactured with the individual incorporation of each fabric as structural reinforcement. Compression tests will be conducted using an Instron universal testing machine in accordance with ASTM D695 to determine the compressive strength, maximum strain, and elastic modulus of the developed materials.

Following mechanical characterization, it is expected that the composites reinforced with denim and linen fabrics will demonstrate potential for the reuse of textile waste as reinforcement in polymer matrices, enabling future applications in sustainable orthopedic prostheses. Furthermore, the results may contribute to the valorization of textile residues and support the development of lightweight, mechanically resistant, and environmentally sustainable composite materials.

The demand for lightweight, durable, and high-performance materials has increased significantly in the sports equipment industry, particularly for eyewear applications where comfort, impact resistance, and dimensional stability are essential [1]. Conventional sports eyewear frames are commonly manufactured from engineering polymers using injection molding processes, which often involve high tooling costs and limited design flexibility [2]. In this context, additive manufacturing has emerged as a promising alternative to producing customized components with complex geometries and reduced material waste [3]. Among thermoplastic polymers, polypropylene (PP) stands out due to its low density, chemical resistance, flexibility, fatigue resistance, and low cost, making it an attractive material for sports applications [4].

This study aims to evaluate the feasibility of using polypropylene for the manufacture of high-performance sports eyewear frames through Fused Deposition Modeling (FDM). The objective is to investigate the mechanical behavior and structural suitability of 3D-printed PP components, considering the requirements of lightweight sporting products subjected to repeated mechanical loading and daily use.

The methodology consisted of processing polypropylene into filaments compatible with FDM technology, followed by the manufacture of eyewear frame prototypes using optimized printing parameters. Mechanical characterization included tensile testing according to ASTM D638 and hardness evaluation to determine the material's structural performance. The printed components were also assessed regarding dimensional stability, flexibility, weight reduction, and manufacturing feasibility. The results were compared with values reported in the literature for polymers commonly employed in sports eyewear applications.

The experimental results demonstrated that polypropylene exhibited a favorable combination of low density and mechanical performance, producing lightweight structures capable of withstanding the stresses typically encountered during sporting activities. The material showed adequate flexibility, reducing the likelihood of brittle failure during impact or accidental deformation. In addition, the low density of polypropylene contributed to significant weight reduction, improving user comfort during prolonged use. The FDM process enabled the fabrication of customized geometries while maintaining satisfactory dimensional quality and structural integrity.

The findings indicate that polypropylene is a promising material for the manufacture of high-performance sports eyewear through additive manufacturing. Its combination of lightweight characteristics, mechanical resistance, flexibility, and processability makes it suitable for customized sporting products. Furthermore, the adoption of polypropylene in additive manufacturing may contribute to reducing production costs and expanding design possibilities while supporting sustainable manufacturing strategies. Therefore, the use of PP-based structures represents a viable alternative for the development of next-generation sports eyewear with enhanced performance and user comfort [4-5].

Tranexamic acid (TXA) is widely used as an antifibrinolytic agent in surgical procedures, promoting hemostasis and potentially influencing the tissue repair process. This study aimed to evaluate the effect of TXA on bone repair in an experimental model of a critical-size defect in rat calvaria. Twenty male Wistar rats were divided into two groups (Control and TXA) and two evaluation periods, 14 and 28 days. Bone defects measuring 5 mm in diameter were created in the calvaria and treated with a blood clot (control group) or a clot soaked in TXA 25 mg/mL (TXA group); all defects were covered with a collagen membrane. Histomorphometric analysis was performed to quantify the area of new bone formation (µm² × 10⁵). The results revealed that the TXA group showed a smaller area of newly formed bone compared to the control group, especially at 28 days (p<0.05), indicating an inhibitory effect of the drug on bone regeneration. In the Clot group, a significant increase in bone formation was observed over time (p = 0.0065), which was not observed in the TXA group. Histological analysis confirmed these findings, showing less defect filling and reduced trabecular organization in TXA-treated specimens, as well as the presence of intense inflammatory infiltrate. It is concluded that, despite its hemostatic properties, topical use of TXA may negatively affect the bone repair process in critical defects, probably by interfering with the physiological dynamics of fibrinolysis and with cellular events essential for new bone formation.

The decommissioning of oil and gas infrastructure generates significant quantities of polymeric materials that are often underutilized at the end of their service life. Among these materials, Polyamide 11 (PA11) is widely employed in flexible pipes, umbilicals, and offshore components due to its excellent mechanical properties, chemical resistance, low moisture absorption, and long-term durability under severe operating conditions. As a high-value engineering thermoplastic derived from renewable castor oil feedstocks, PA11 represents an attractive candidate for mechanical recycling and reintegration into industrial value chains. However, the effects of repeated processing on its mechanical performance must be evaluated to determine its potential for reuse in engineering applications [1–3].

This study aims to assess the feasibility of reusing decommissioned PA11 recovered from the oil and gas industry through mechanical recycling. The primary objective is to investigate the influence of successive processing cycles on the tensile properties of the material and to determine whether the recycled polymer retains sufficient performance for future industrial applications. By evaluating the recyclability of decommissioned PA11, this work seeks to contribute to sustainable waste management practices and support circular economy strategies within the energy and polymer sectors [2,4]

The methodology consisted of collecting and preparing PA11 obtained from decommissioned oil and gas components, followed by successive extrusion cycles to simulate repeated mechanical recycling. Tensile tests were performed after each processing stage to evaluate tensile strength, elastic modulus, and elongation at break. The results obtained from the different processing cycles were compared to identify possible degradation mechanisms and assess the retention of mechanical properties throughout the recycling process.

The experimental results demonstrated that the recycled PA11 maintained satisfactory mechanical performance after successive processing cycles, indicating good resistance to thermal and mechanical degradation during reprocessing. Although variations in tensile properties were observed with increasing numbers of recycling cycles, the material retained characteristics compatible with engineering applications and further processing. Similar behavior has been reported for recycled engineering thermoplastics, which often maintain adequate structural performance even after multiple reprocessing stages [4].

It can be concluded that PA11 recovered from decommissioned oil and gas infrastructure presents significant potential for mechanical recycling. The material exhibited adequate retention of tensile properties after repeated processing, supporting its use as a secondary raw material for the manufacture of new products. These findings reinforce the importance of developing sustainable recycling routes for high-performance engineering polymers and contribute to advancing circular economy practices, reducing industrial waste, and promoting resource efficiency in the oil and gas sector [5].

The increasing use of disposable plastic consumables in research laboratories, hospitals, and diagnostic centers has led to a significant rise in plastic waste generation, particularly from PCR microtubes and biological sample storage tubes. Most of these consumables are manufactured from polypropylene (PP), a thermoplastic polymer widely recognized for its chemical resistance, thermal stability, and cost-effectiveness. Despite its high recyclability, a substantial portion of this material is currently disposed of through landfilling or incineration, resulting in environmental impacts and the loss of valuable polymeric resources [1,2].

This study aims to evaluate the technical feasibility of reusing polypropylene PCR microtubes and biological sample tubes as a raw material source to produce recycled composites and filaments for Fused Deposition Modeling (FDM) additive manufacturing. The research seeks to determine whether these laboratory wastes can be integrated into a circular economy framework, promoting waste valorization while reducing the demand for virgin polymer feedstocks.

The proposed methodology includes selective collection of the residues, decontamination according to biosafety protocols, grinding, characterization, and extrusion processing. The recycled materials will be characterized by Fourier Transform Infrared Spectroscopy (FTIR) to identify possible chemical degradation and polymer stability after reprocessing. Mechanical characterization will include tensile testing to determine tensile strength, elastic modulus, and elongation at break, as well as Shore hardness and Barcol hardness tests to evaluate surface resistance and mechanical integrity of the recycled materials. The processed polypropylene will subsequently be extruded into filaments for 3D printing, and the printed specimens will be evaluated regarding dimensional stability, printability, and mechanical performance.

Recent studies have demonstrated that recycled polypropylene presents significant potential for additive manufacturing and sustainable composite applications when appropriate cleaning, sorting, and reprocessing procedures are adopted [3,4]. In addition, polymeric waste generated by specialized sectors has been recognized as a promising source for high-value-added materials, contributing to waste reduction and the implementation of circular economy strategies [5].

Based on the literature and the intrinsic characteristics of polypropylene, it is expected that the recycled laboratory waste investigated in this study will exhibit suitable mechanical and structural properties for conversion into composite materials and FDM filaments. The incorporation of tensile, Shore hardness, Barcol hardness, and FTIR analyses will provide a broader understanding of the effects of recycling on material performance and structural integrity. Therefore, this feasibility study may contribute to reducing the environmental impact associated with laboratory plastic waste while supporting the development of sustainable polymeric materials for additive manufacturing applications

Hyaluronic acid (HA) is a linear glycosaminoglycan of significant biological and technological relevance, widely distributed in the extracellular matrix and recognized for its biocompatibility, hydrophilicity, and water-retention capacity. This literature review aims to discuss the evolution of hyaluronic acid from its initial methods of production to the most recent advances in filler development, with an emphasis on aspects related to materials science and engineering. Initially obtained from animal sources, HA is now produced predominantly through microbial fermentation, representing a significant advancement in terms of purity, reproducibility, molecular weight control, and biological safety. After purification, the polymer can undergo chemical crosslinking to form hydrogels with adjustable mechanical and rheological properties, enabling greater resistance to degradation and improved clinical performance. In this context, parameters such as storage modulus, loss modulus, cohesivity, and swelling factor play a central role in the characterization of fillers, as they directly influence their structural support capacity, tissue integration, and response to stresses exerted by surrounding tissues. In addition to enzymatic degradation mediated by hyaluronidases, oxidative degradation induced by reactive species is also noteworthy, as it can compromise the integrity of the polymer network and reduce the longevity of the biomaterial after implantation. Recent literature demonstrates that HA fillers are moving toward a new generation of more stable, bioactive, and multifunctional formulations, including hybrid systems, advanced crosslinking technologies, and the incorporation of agents capable of modulating degradation and biological response. From this perspective, approaches that combine HA with bioactive and antioxidant phases stand out, with the potential to provide mechanical support, bioactivity, and greater resistance to oxidative stress. The evolution of HA fillers highlights the transition from a material that is essentially volumizing to a promising functional platform in dentistry, aesthetics, and regenerative medicine.

Rehabilitation of severely atrophic tissues remains a major challenge across multiple surgical disciplines, including implant dentistry, orthopedics, and reconstructive surgery, particularly due to limited vascularization and reduced regenerative capacity of host tissues. Conventional biomaterials, such as bone substitutes and barrier membranes, provide structural support but often lack the biological activity necessary for optimal integration. This limitation has led to the development of hybrid regenerative approaches that combine structural biomaterials with biologically active components.

The purpose of this study is to evaluate the role of adipose-derived tissue as a bioactive adjunct in combination with conventional biomaterials for implant-based and reconstructive procedures. Adipose tissue, rich in stromal vascular fraction (SVF) and adipose-derived stem cells (ADSCs), exhibits angiogenic and immunomodulatory properties that may enhance tissue healing and integration.

A translational approach was employed, integrating current literature from oral and maxillofacial surgery, orthopedics, and plastic surgery with clinical regenerative strategies involving the association of adipose-derived grafts with bone substitutes, platelet concentrates, and barrier membranes. Emphasis was placed on understanding how adipose-derived components influence vascularization, cellular recruitment, and biomaterial performance.

The histological  findings indicate that hybrid strategies incorporating adipose-derived tissue improve the biological environment of grafted areas, promoting enhanced vascularization, faster integration, and improved tissue quality. These effects appear consistent across different anatomical sites and surgical applications.

In conclusion, the combination of adipose-derived grafts with conventional biomaterials represents a promising multidisciplinary strategy. Rather than replacing existing materials, adipose tissue acts as a biological enhancer, supporting a shift toward biologically driven regenerative approaches in modern surgery.

Hydroxyapatite (HA or HAp) has emerged as one of the most promising calcium phosphates in materials science and is widely employed as a biomaterial due to its remarkable chemical and structural similarity to the mineral phase of natural bone tissue. Chemically represented by the formula Ca₁₀(PO₄)₆(OH)₂ or Ca₅(PO₄)₃OH, its crystalline structure is organized through calcium ions and phosphate groups in a highly ordered lattice [1,2,4]. In biological systems, apatite found in human bone is characterized as nanocrystalline, carbonated, and structurally defective, features that provide higher solubility and biological reactivity compared with conventional synthetic hydroxyapatite [2,3]. The incorporation of carbonate ions (CO₃²⁻) into phosphate sites, known as type-B substitution, plays a fundamental role in reducing crystallinity and crystal size while simultaneously increasing the surface area of the material. These microstructural modifications are essential for enhancing bioactivity, osteoconduction, and cellular integration, and may be further improved through doping with magnesium (Mg²⁺), strontium (Sr²⁺), and zinc (Zn²⁺), which promote osteogenicity [2,3,4,5].

As a high-performance biomaterial, nanometric hydroxyapatite (nHA) is indicated for the repair of complex bone defects, acting both as an implantable material and as a coating due to its ability to be gradually resorbed and replaced by newly formed bone tissue [1,5]. The development of these nanomaterials requires rigorous control of synthesis routes and the selection of calcium and phosphorus precursors, variables that directly determine the final physicochemical properties.

This study aims to provide a literature review of the conventional methodologies currently employed for hydroxyapatite synthesis. Coprecipitation stands out as a simultaneous ion precipitation technique in solution, frequently using calcium hydroxide (Ca(OH)₂) and tricalcium phosphate (Ca₃(PO₄)₂) as calcium and phosphorus sources [2,5]. Although effective, this method may present challenges regarding stoichiometric control and crystal aspect ratio regulation [1,2]. Alternatively, the sol-gel route enables the production of highly homogeneous materials at relatively low temperatures (below 400 °C), employing calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O) and phosphorus pentoxide (P₂O₅), followed by thermal treatment to adjust crystallinity [1]. Among the methods involving high-pressure and high-temperature conditions, hydrothermal synthesis has demonstrated high efficiency in producing crystals with controlled morphology, using precursors such as calcium oxide (CaO) and phosphorus pentoxide (P₂O₅) in stoichiometric concentrations [1–4].

The wet mechanochemical technique offers high stoichiometric control through the application of mechanical energy during the coprecipitation of Ca₃(PO₄)₂ and Ca(OH)₂, followed by calcination at high temperatures (1000–1200 °C) for structural purification [2,5]. Another relevant approach is rapid precipitation, which aims to limit crystal growth in order to obtain uniform nanoparticles or nanorods, also employing sources such as CaO and P₂O₅ [1,2]. Regardless of the selected synthesis route, maintaining the Ca/P molar ratio close to the ideal value of 1.67 is critical, since significant deviations may result in the formation of undesirable secondary phases, such as calcium oxide or beta-tricalcium phosphate (β-TCP), compromising both the mechanical stability and biological predictability of the material. Therefore, the careful selection of processing parameters and additives for agglomeration control is essential to ensure a balance between structural stability and biological resorption, which is necessary for clinical success [1,2,3,5].

For athletes involved in contact and collision sports, the use of a mouthguard is essential for minimizing the occurrence and severity of orofacial injuries. Mouthguards can absorb and dissipate impact energy, reducing stress concentration in dental and bone structures during traumatic events[1-2]. This protective function becomes even more important for patients rehabilitated with implant-supported prostheses, since implant-abutment-crown systems present biomechanical behavior that differs from natural teeth due to the absence of periodontal ligament cushioning[3-4]. Consequently, individuals rehabilitated with dental implants who return to sports activities may be more susceptible to mechanical complications, including prosthetic crown fracture, abutment damage, implant overload, and stress transmission to the surrounding cortical bone. In this context, the development of digitally manufactured mouthguards using additive manufacturing technologies represents an innovative alternative to conventional thermoformed devices, allowing greater customization, reproducibility, and control over material properties[3-5].This study aimed to evaluate the mechanical behavior of a maxillary region containing an implant-abutment-crown complex subjected to impact conditions, as well as to investigate the protective effect of a custom mouthguard produced through additive manufacturing. A three-dimensional model of the maxilla, implant system, and surrounding bone structures was obtained from computed tomography images and converted into separate finite element meshes for numerical simulation. The implant-supported rehabilitation consisted of a titanium implant, prosthetic abutment, and ceramic crown positioned in the anterior maxillary region. A mouthguard geometry was digitally designed to cover the dental surfaces and adjacent structures. The device was manufactured using thermoplastic polyurethane (TPU) filament through fused deposition modeling (FDM) technology with a Bambu Lab 3D printer, aiming to provide flexibility and energy absorption capacity during impact loading. To simulate traumatic conditions commonly observed in sports activities, a steel sphere with an initial velocity of 1 m/s was used as the impact object in the computational analysis. Stress distribution and mechanical response were evaluated individually for the implant, abutment, prosthetic crown, and surrounding bone tissue. In addition to the numerical simulations, experimental validation was performed using a pendulum impact system with impact angulations of 45°, 60°, and 90°, reproducing different directions and intensities of force application. These tests were conducted to validate the biomechanical behavior observed in the finite element analysis and to assess the efficiency of the TPU mouthguard under dynamic loading conditions. The results demonstrated that the presence of the mouthguard significantly reduced stress concentration in the implant-abutment-crown complex and surrounding cortical bone. Furthermore, the device minimized the transmission of impact forces to the prosthetic crown, contributing to the prevention of mechanical failures and structural damage. The TPU material exhibited satisfactory flexibility and impact absorption behavior, indicating its potential application in the fabrication of customized protective devices for athletes rehabilitated with implant-supported prostheses. The experimental pendulum validation showed behavior consistent with the computational analysis, reinforcing the reliability of the proposed methodology. 

The objective of this work was to review the results of studies describing the structure of healthy dental enamel, its composition and mechanical properties, this literature review aimed, and correlate them with the effects of erosive and bleaching agents. The methodology was based on a detailed analysis of 10 scientific articles, encompassing in vitro studies, reviews, and methodological evaluations. The results indicate that the mechanical properties (hardness, modulus of elasticity, and toughness) are heterogeneous and anisotropic, and dependent on the structure, the size of the nanocrystals (following the Hall-Petch model), and the presence of organic and aqueous phases, which increase fracture toughness. This anisotropy increases the fracture toughness of the dentin enamel. It was found that the erosive potential of different acids does not correlate directly with pH or acidity, but with the type of acid and its molecular interaction. Regarding dental bleaching, the effects on microhardness are controversial. Some researchers cite an immediate reduction in hardness (in ~51% of cases). Although an immediate reduction is frequently reported in vitro, this is often reversible in vivo by the action of saliva and fluoride. It is concluded that enamel is an optimized material, acid erosion represents a complex chemical risk, and the mechanical and chemical effects of bleaching, although detectable in vitro, appear to be clinically transient due to remineralization mechanisms.

Guided bone regeneration (GBR) relies on barrier membranes to maintain space and prevent soft tissue invasion during bone healing. Among available biomaterials, resorbable synthetic membranes based on polydioxanone (PDO) have gained attention due to their biocompatibility and predictable degradation profile. However, the influence of membrane thickness on the physicochemical behavior of PDO over time remains insufficiently understood.

This study aimed to evaluate the effect of membrane thickness on mass variation and pH changes of PDO membranes during in vitro degradation. Membrane samples with two different thicknesses (0.25 mm and 0.50 mm) were immersed in phosphate-buffered saline (PBS) and maintained at 37 °C. Analyses were performed at 8, 18, 39, 55, and 99 days. Mass variation was determined using an analytical balance after controlled dehydration, and pH values were measured in the immersion medium. 

Both membrane groups exhibited a significant reduction in mass over time (p<0.05). Thicker membranes (0.50 mm) consistently showed higher mass values at all time points, indicating a slower degradation profile. A progressive decrease in pH was observed throughout the experimental period, with significantly lower pH values in the thicker membranes from day 8 onward (p<0.05). These findings suggest that increased membrane thickness reduces water diffusion and delays the release of degradation byproducts, influencing local physicochemical conditions.

Within the limitations of this in vitro study, membrane thickness significantly affects the degradation behavior of PDO, impacting both mass loss and pH variation over time. These factors may influence membrane stability and performance in GBR procedures, particularly in clinical scenarios requiring prolonged barrier function.

The oral cavity is a complex ecosystem in which interactions between microorganisms and surfaces, whether natural tissues or restorative and surgical materials, are crucial for oral health and the development of pathologies such as caries and periodontitis.[1][3] This study aims to analyze how the physicochemical characteristics of surfaces, such as roughness, surface charge, hydrophobicity, and topography, influence microbial adhesion and the maturation of intraoral biofilms.[2][6] Studies indicate that surfaces with high roughness (Ra) facilitate microbial colonization by offering niches protected against shear forces and increasing the contact area.[2] Hydrophobicity also plays a critical hydrophobic surfaces tend to favor initial adhesion, whereas the transition to
more hydrophilic surfaces, via coatings such as HPMC-ZnO, results in a significant reduction in bacterial adhesion.[6] Furthermore, the electrostatic charge of the surface interacts with the negative charge of the cell membranes of pathogens such as S. mutans and C. albicans, mediating the adhesion process.[6] Analysis of suture materials reveals that multifilament and porous structures are more prone to biofilm formation than smooth and compact surfaces. It is concluded that modifying surface properties, especially through nanotechnology incorporating silver nanoparticles (AgNPs) and zinc oxide (ZnO), represents an effective strategy to create anti-adhesive and antimicrobial surfaces, thereby reducing the risk of opportunistic infections in the oral environment.

Hydroxyapatite (HAp) is a bioceramic widely used in bone grafts due to its excellent bioactivity. However, conventional high-temperature sintering can compromise its biological reactivity. This study investigated the structural integrity and chemical stability of non-sintered HAp pellets subjected to immersion in PA methanol. Samples were produced via wet-route precipitation and shaped by uniaxial pressing (1 ton). The integrity test consisted of immersing the pellets in methanol for 17 hours, followed by mass variation analysis, Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The results revealed negligible mass variation (< 0.2%), indicating high physical stability. SEM micrographs confirmed the absence of cracks or surface degradation, while EDS demonstrated the maintenance of the stoichiometric Ca/P ratio (~1.67). In addition, the samples preserved their morphological characteristics throughout the experimental procedure. It is concluded that non-sintered HAp maintains its structural integrity in an organic medium, validating its potential for biomedical applications without the need for prior heat treatment.

Titanium and its alloys are extensively employed in dental and orthopedic implants due to their excellent mechanical strength, corrosion resistance, and biocompatibility [1]. Nevertheless, conventional alloys still face limitations related to elastic modulus mismatch with bone tissue and limited intrinsic bioactivity, which may compromise long-term implant performance [2]. In this context, the development of β-type titanium alloys stabilized with non-toxic elements such as Nb and Mo has emerged as a promising approach to achieve improved mechanical compatibility and enhanced biological response [3]. In this study, metastable β-type titanium alloys were produced by arc melting followed by homogenization treatments, aiming to control phase stability and microstructural features. Structural and microstructural characterization using XRD, SEM, EBSD, and TEM revealed a predominantly β-phase matrix with nanoscale heterogeneities and the presence of metastable phases, such as ω, which are known to influence mechanical behavior and elastic modulus. These characteristics are particularly relevant for dental and orthopedic implants, where mechanical compatibility with surrounding bone is critical to reduce stress shielding effects. To further enhance biological performance, micro-arc oxidation (MAO) surface modification was applied to the alloys [4]. The process enabled the formation of porous TiO₂ coatings with controlled morphology and chemistry. Increasing the current density during MAO treatment resulted in higher surface roughness, improved hydrophilicity, and the formation of rutile phases, all of which are favorable for cell adhesion and osseointegration. In addition, incorporating copper into the coatings can confer antibacterial properties, particularly important in dental applications where infection control is a major concern [5]. The combination of optimized bulk microstructure and tailored surface properties provides a synergistic strategy for improving both mechanical and biological performance of titanium-based implants. In dental applications, these materials can accelerate osseointegration, improve implant stability, and reduce the risk of peri-implant infections. In broader biomedical contexts, these advances support the development of multifunctional implants that interact more effectively with the physiological environment. Overall, this study highlights the potential of integrating β-type alloy design with advanced surface engineering techniques to develop next-generation titanium biomaterials. These materials represent a significant step toward more efficient, durable, and biologically active implants for dental and medical applications. (Financial support: CNPq, grants #314.810/2021-8 and #421.677/2023-6, and FAPESP, grant #2024/01.132-2).

The clinical longevity of Titanium dental implants relies on the chemical and mechanical stability of their interface with the oral environment. This narrative literature review analyzes the phenomenon of tribocorrosion, a synergistic degradation process resulting from the interaction between mechanical wear and electrochemical corrosion. Evidence shows that micromovements at the implant-abutment interface frequently disrupt the passive Titanium oxide layer, a process exacerbated by occlusal loads and parafunctional habits. Factors such as the presence of fluorides, acidity from bacterial biofilms, and metabolites like lipopolysaccharide (LPS) significantly accelerate metal degradation. Consequently, metallic debris in micro- and nano-scales, along with metal ions, are released into peri-implant tissues. These degradation products activate macrophages and stimulate the release of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α), altering the RANKL/OPG balance and inducing aseptic osteolysis or aggravating peri-implantitis. Mitigation strategies, including Morse taper connections, the platform switching concept, and anodization surface treatments, have shown efficacy in reducing tribocorrosion byproducts. In conclusion, a profound understanding of tribocorrosion is essential for developing biomaterials with extended clinical service life and reduced biological reactivity.

Hydroxyapatite (Hap) is the main inorganic component of human bone and dental tissues. HAp (PO₄)₆(OH)₂) is approximately 65% ​​of bone mass and up to 96% of dental enamel [1]. Due to its similarity in composition and crystalline structure to natural bone, this material exhibits high biocompatibility, bioactivity, and osteoconductivity. HAp favors the adhesion and proliferation of osteoblastic cells [2].
For clinical applications, it is important to understand the thermal behavior and structural stability of hydroxyapatite. In this work, differential scanning calorimetry (DSC) was used to characterize HAp. DSC allows the identification of thermal events, such as phase transformations and decomposition processes, from the variations in heat flow associated with the sample [3]. Three samples of the commercial biomaterial (Blue Bone ® ) manufactured by Regener Biomateriais (Curitiba, Brazil) were analyzed. Blue Bone ® is composed of nanohydroxyapatite and β-tricalcium phosphate (β-TCP), in an approximate ratio of 80/20 [4]. The analyses were performed in a Shimadzu DSC 60 calorimeter (Shimadzu, Kyoto, Japan). Each sample, with a mass of approximately 4 mg, was placed in aluminum crucibles and subjected to a heating ramp from 25 to 550°C, at a rate of 5 °C/minute. The results obtained showed the presence of a few thermal events throughout the analyzed temperature range. This behavior indicates that the material exhibits good thermal stability, with a predominance of well-defined crystalline phases and a significant absence of volatile compounds or organic residues.
Furthermore, the combination of hydroxyapatite and β-TCP phases is relevant from a biological point of view: while β-TCP exhibits greater solubility and can contribute to the release of calcium and phosphate ions, hydroxyapatite tends to ensure greater structural stability to the material [5]. The results of the DSC analysis indicate that the Blue Bone ® biomaterial exhibits thermal behavior compatible with materials already processed and intended for biomedical applications. The absence of multiple complex thermal peaks suggests that the material possesses good quality and stability, important characteristics for its use in bone regeneration procedures. The biphasic hydroxyapatite is a suitable biomaterial for clinical applications, especially in situations requiring structural support combined with bioactivity, and aligns with more sustainable practices in biomaterial development.

The increasing adoption of additive manufacturing technologies has generated significant quantities of thermoplastic waste, particularly Polyethylene Terephthalate Glycol (PETG), which is widely used due to its excellent printability, toughness, and dimensional stability [1]. Mechanical recycling of PETG represents a sustainable alternative for reducing waste generation and promoting circular economy principles within the additive manufacturing sector [2]. However, the performance of recycled PETG components is strongly influenced by processing parameters, which directly affect interlayer adhesion, internal defects, and mechanical behavior [3].

This study aims to optimize Fused Deposition Modeling (FDM) parameters to produce components manufactured from recycled PETG filament. The objective is to evaluate the influence of layer thickness, printing speed, and extrusion temperature on the impact resistance of printed specimens, identifying the processing conditions that maximize mechanical performance.

Recycled PETG filament with a nominal diameter of 1.75 mm was produced through the mechanical recycling of discarded parts generated by a local 3D printing company. The waste material was collected, sorted, ground, and re-extruded into new filaments. Test specimens were manufactured using a factorial experimental design involving three-layer thicknesses (0.08, 0.12, and 0.20 mm), three printing speeds (60, 80, and 100 mm/s), and three extrusion temperatures (200, 210, and 220 °C). The mechanical performance of the printed specimens was evaluated through Izod impact testing, allowing the influence of processing parameters on energy absorption and fracture resistance to be determined.

The results demonstrated that all evaluated parameters significantly influenced the impact behavior of recycled PETG specimens. Lower layer thickness promoted improved interlayer bonding and reduced internal void formation, resulting in higher impact strength. Intermediate printing speeds produced more consistent mechanical performance, whereas excessively high speeds tended to reduce layer adhesion and increase structural defects. Extrusion temperature also played a critical role, with higher temperatures generally improving polymer diffusion between adjacent layers and enhancing impact resistance. The combination of reduced layer thickness and elevated extrusion temperature resulted in the highest Izod impact values, indicating superior structural integrity and energy absorption capability.

The findings indicate that the mechanical performance of recycled PETG can be substantially improved through appropriate process parameter selection. Optimized printing conditions promoted stronger interlayer adhesion and reduced manufacturing defects, enabling the production of components with enhanced impact resistance. Therefore, the combination of mechanical recycling and process optimization represents a viable strategy for producing sustainable, high-performance PETG components through additive manufacturing, while simultaneously reducing waste generation and raw material consumption [4-5].

Lip repositioning techniques associated with myotomy have demonstrated consistent results in reducing gingival display in patients with gummy smile. However, long-term stability remains a significant clinical challenge, mainly due to the capacity for reorganization of intradermal muscle fibers during the healing process. This phenomenon is directly associated with the partial relapse observed in some cases, even when the surgical technique is properly executed.

In this context, modulation of the healing process emerges as a key factor for therapeutic success. The use of non-resorbable biomaterials, such as polyester sutures, inserted in a delayed post-operative phase, has been proposed as a therapeutic approach to interfere with muscle reorganization and induce controlled fibrosis, acting as a physical barrier against relapse. This approach represents a shift in paradigm, moving the focus from the surgical intervention itself to the active control of the healing process.

Clinical outcomes observed with this strategy demonstrate improved stability of results over medium-term follow-up, reducing the need for retreatment and, consequently, the cumulative consumption of clinical materials and interventions. From this perspective, stability can also be understood as a component of sustainability in healthcare, as longer-lasting treatments imply a lower use of resources throughout the therapeutic cycle.

Despite these promising results, the clinical application of the technique still presents relevant challenges. The insertion of the sutures, as well as the definition of the ideal number and thickness of the material, depend on operator skill and present variability. Furthermore, the creation of a functional barrier using autogenous tissues remains limited in terms of predictability and volumetric stability, reinforcing the need for alternative solutions.

These limitations open space for the development of new biomaterials capable of acting not only as structural elements but also as functional modulators of the healing process. Ideally, such materials should combine adequate mechanical performance, biological integration, and reduced environmental impact, aligning clinical efficiency with sustainability principles.

Therefore, the present work not only introduces a therapeutic approach for relapse control but also proposes a new perspective on healing modulation as a central strategy for achieving stable, predictable, and sustainable outcomes in esthetic periodontal surgery.

Bone tissue loss resulting from trauma, disease, or surgical procedures remains a major challenge for regenerative medicine, as the organism is often unable to restore damaged areas through natural healing alone. Guided Tissue Regeneration (GTR) employs semipermeable membrane barriers to create conditions favourable for new bone formation [1]. This study proposes the development of a composite biomaterial from pirarucu (Arapaima gigas) fish scales — a sustainable by-product of Amazonian aquaculture — integrating both hydroxyapatite (HAp) and type I collagen extracted from the same biological source.

Pirarucu scales present a hierarchical architecture comprising an outer mineralized layer of carbonated apatite and an inner lamellar collagen matrix. This dual composition makes them a unique raw material for the simultaneous production of two complementary biomaterials: a biogenic hydroxyapatite and a collagen membrane, both aligned with the structural requirements of GTR [2]. The experimental strategy was based on controlled demineralisation of scales using HCl (0.6 mol L⁻¹, 24 h and 5 days) and EDTA (0.5 mol L⁻¹, 72–96 h), followed by thermal conversion (calcination at 550°C) of the mineral fraction. Collagen membranes were obtained from demineralised scales and shaped by pressing between glass slides. Scaffolds were produced from HAp powder dispersed in sodium alginate (70:30 HAp:NaAlg) and cross-linked in CaCl₂ solution. Samples were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and thermogravimetric analysis (TGA).

XRD analysis confirmed the presence of a highly pure hydroxyapatite, with diffraction peaks at 2θ = 25.9°, 31.8°, 32.2°, and 39.9° matching the JCPDS 09-0432 reference pattern. The absence of secondary phases (β-TCP or CaO) validated the efficiency of the calcination route. A secondary signal near 29° indicated the presence of type-B carbonated apatite, a feature desirable for enhanced bioactivity and osseointegration [3]. EDS analysis yielded a Ca/P ratio of approximately 1.66, consistent with stoichiometric HAp. FTIR spectra confirmed phosphate bands (ν₃ PO₄³⁻ at 1040–1090 cm⁻¹; ν₄ PO₄³⁻ at 560–603 cm⁻¹), hydroxyl groups (3570 cm⁻¹), and carbonate substituents (1420, 875 cm⁻¹). SEM micrographs of untreated scales showed a dense, lamellar, highly mineralised surface. After HCl treatment, progressive demineralisation exposed the fibrillar collagen network, while EDTA treatment preserved the collagen triple-helix structure with minimal fibrillar disruption, as evidenced by well-defined amide I, II, and III bands in FTIR. The combined results demonstrate the complementarity of both demineralisation strategies: HCl efficiently isolates pure mineral phases, while EDTA is superior for producing structurally intact collagen membranes.

The results confirm the technical and scientific viability of pirarucu scales as a dual-source platform for bioceramic and collagen-based biomaterials. The biogenic HAp exhibits composition, crystallinity, and purity comparable to commercial synthetic analogues, with the advantage of retaining physiological trace ions (Na⁺, Mg²⁺, Sr²⁺) that enhance intrinsic bioactivity without external doping. The collagen membranes obtained via EDTA show structural integrity suitable for use as selective barriers in GTR. This approach integrates circular bioeconomy principles, valorising a low-cost fishery by-product while generating high-value biomaterials for dentistry, orthopaedics, and tissue engineering.

With advances in regenerative dental treatments, platelet- and leukocyte-rich fibrin (PRF) membranes have become widely used tools in tissue engineering for their ability to enhance bone grafts, promote the regeneration of hard and soft tissues, stimulate angiogenesis, and modulate cellular differentiation and migration. The present study aimed to quantify insulin-like growth factor 1 (IGF-1) in PRF membranes from smokers and non-smokers, in accordance with the U.S. Preventive Services Task Force (USPSTF) guidelines. The sample consisted of 28 individuals, including 14 smokers and 14 non-smokers. Six venous blood samples (10 mL each) were collected and placed in silica-coated plastic tubes, which were allowed to rest for five minutes to enable matrix organization and fibrin clot formation. The samples were then centrifuged at 2700 rpm (408 g) for 12 minutes at room temperature to obtain the PRF membranes. After membrane processing, IGF-1 quantification was performed using an enzyme-linked immunosorbent assay (ELISA). Data were subjected to the Student's t-test with a significance level of 5%. The results demonstrated no statistically significant difference in IGF-1 levels between PRF membranes derived from smokers and non-smokers (p = 0.258), with mean values of 1.82 ng/mL in the control group and 1.62 ng/mL in the smoker group. It was concluded that smoking did not have a significant influence on IGF-1 concentration in the evaluated PRF membranes.

Hydroxyapatite (HA), a calcium phosphate with a composition similar to that of the mineral phase of human bone, has been widely used as a bone graft material due to its bioactive, osteoconductive, and biocompatible properties. Recently, technological advances and clinical demands have driven new approaches to its use, revealing promising trends. In particular, growing interest has been directed toward nanohydroxyapatite (nHA), which exhibits a high specific surface area, resulting in enhanced bioactivity and bone integration compared with conventional porous HA. This nanostructured form has also been incorporated into hydrogel composites, forming biomimetic matrices with tunable properties for bone regeneration. Another research direction involves the modulation of HA-containing scaffold porosity, with particular emphasis on nanopores. These structures favor the adsorption of proteins and growth factors, such as BMP-2 and VEGF, influence macrophage behavior through differentiated immunological microenvironments, and promote osteoblast recruitment and differentiation. In parallel, increasing interest has been devoted to obtaining natural HA from biological sources, such as crab shells (Portunus pelagicus), fish bones, and bovine bones, since these represent sustainable and low-cost alternatives with a chemical composition closer to that of human bone tissue. Furthermore, innovative approaches have explored hybrid scaffolds based on biopolymers and HA. Among these, the development of wool-derived keratin scaffolds incorporating HA as the inorganic phase and crosslinked with hydroxypropyl methylcellulose (HPMC), obtained by freeze-drying, is noteworthy. These scaffolds exhibited an interconnected porous architecture, average pore sizes of 108 µm, and a total porosity of 79.6%, in addition to structural stability and in vitro cytocompatibility. EDX analysis confirmed a Ca/P molar ratio of 1.6, and the compressive strength was approximately 0.84 MPa, making these materials promising candidates for alveolar bone regeneration.  Additive manufacturing, such as 3D printing, has also been applied to the production of customized HA-containing scaffolds, including polyglycolic acid/HA composites. This technique enables the fabrication of structures with precise architecture and the integration of multiple materials, thereby expanding their clinical potential. Another relevant approach is the doping of HA with ions such as Cu²⁺, Sr²⁺, and CO₃²⁻, which imparts antimicrobial and osteogenic properties and improves mechanical performance. Inspired by the microstructure of natural bone, biomimetic composites containing one-dimensional HA doped with Cu and Sr have been developed. These composites exhibit compressive and tensile strength, elastic modulus, and toughness comparable to those of cortical bone, while also promoting controlled release of dopant ions, induced mineralization, and collagen fiber orientation by mesenchymal stem cells. These advances represent a significant step toward the development of bioactive synthetic bone grafts.

Hyaluronic acid-based gel is widely used for facial rejuvenation due to its biocompatibility and viscoelastic properties. The disadvantage of hyaluronic acid is the
lower clinical durability due to enzymatic and oxidative degradation. The addition of hydroxyapatite (HA) and glutathione to hyaluronic acid can improve the gel's properties. The HA provides structural support and biostimulatory potential. Glutathione may act as an antioxidant, delaying oxidative degradation of the gel and preserving its mechanical integrity. This study aimed to analyze whether the addition of hydroxyapatite and glutathione changes the rheological behavior of a crosslinked hyaluronic acid dermal filler. The new composite was compared with the pure hyaluronic acid. Tests were performed using oscillatory rheometry with a parallel-plate geometry, including an amplitude sweep to identify the linear viscoelastic property and a frequency sweep to evaluate the material's dynamic response. The pure gel exhibited a storage modulus of approximately 600-750 Pa. The composite reached values of 1300-1400 Pa, demonstrating increased stiffness, cohesiveness, and lifting capacity. In both formulations, G’ remained higher than G”, confirming predominantly elastic behavior. The modified composite exhibited rheological behavior comparable to that of highly elastic structural fillers. It is possible to conclude that the addition of hydroxyapatite and glutathione significantly alters the hyaluronic acid's rheology, increasing its potential for use in deep planes and facial areas requiring greater structural support.

Hydroxyapatite (HAp) is one of the most widely studied ceramic biomaterials for biomedical applications due to its high biocompatibility, chemical similarity to the mineral phase of bone tissue, and potential use in grafts, coatings, and scaffolds. However, conventional sintering of HAp typically requires high temperatures, which may promote excessive grain growth, phase degradation, and increased energy consumption [1]. Cold sintering emerges as an ultra-low-energy processing route, as it enables material consolidation at significantly lower temperatures by combining uniaxial pressure with the presence of a transient liquid phase [2]. This approach is particularly innovative for biomaterials, as it can better preserve desirable microstructural features while reducing thermal processing costs.

In this study, hydroxyapatite was obtained via a sol-gel route, following a methodology similar to that described in [3]. After synthesis, the material was subjected to cold sintering using water as the transient liquid phase. Processing was carried out under different temperature and pressure conditions, allowing the evaluation of their influence on material densification. The investigated temperatures were 175 °C, 200 °C, and 225 °C, while the applied pressures were 300, 400, and 500 MPa, depending on the experimental condition of each group. The processing efficiency was assessed based on densification values calculated using the theoretical density of 3.16 g/cm³, considering mean values and their respective standard deviations for comparison.

The results show that cold sintering was capable of producing bodies with relatively high densification for a ceramic processed at low temperature, with average values ranging approximately from 79.55% to 85.91%. The lowest average densification was observed for the condition of 300 MPa and 175 °C, with a mean of 79.55% and a standard deviation of 6.10, indicating not only lower consolidation efficiency but also greater dispersion among the samples. In contrast, samples processed at 400 MPa exhibited the best overall performance. At 200 °C, the average densification was 83.57%, with a standard deviation of only 0.67, suggesting high experimental reproducibility. At 175 °C and 400 MPa, the mean was 84.35% with a standard deviation of 2.72, while the condition of 225 °C and 400 MPa showed the highest average result, reaching 85.91% densification with a standard deviation of 2.05.

For samples processed at 500 MPa, a less uniform behavior was observed. At 200 °C, the average densification was 81.74%, accompanied by a high standard deviation of 7.99, indicating significant variability among the obtained bodies. On the other hand, the condition of 500 MPa and 175 °C presented a mean of 84.20% and a standard deviation of 2.24, showing more consistent performance. Overall, the data suggest that increasing pressure does not necessarily result in higher densification or improved process stability. Among the evaluated conditions, 400 MPa stood out as the most favorable range, especially when combined with temperatures between 175 °C and 225 °C. Thus, the results indicate that cold sintering is a technically viable route for consolidating sol-gel-derived hydroxyapatite, with potential for obtaining relatively dense bodies under mild processing conditions.

This work aimed to analyse the feasibility of fabricating lithium disilicate (Li₂O₅Si₂) ceramic structures using robocasting, an additive manufacturing technique, and compared their mechanical, chemical, and microstructural properties with those produced by conventional subtractive manufacturing. It was hypothesized that lithium disilicate could be successfully processed via robocasting and that the resulting structures would demonstrate mechanical performance comparable to those obtained through traditional methods.

Specimens were divided into two groups: subtractive manufacturing (SM) and additive manufacturing via robocasting (AR). For the AR group, Li₂O₅Si₂ powder was blended with ammonium polyacrylate, hydroxypropyl methylcellulose, and a polyelectrolyte to produce a printable colloidal gel. Disc-shaped were made using a custom-built direct ink writing (DIW) 3D printer. In the SM group, samples were milled from pre-crystallized ceramic blocks to match the dimensions of the AR specimens. All samples were subsequently crystallized at 840 °C.

Mechanical properties were determined through biaxial flexural strength (BFS) testing and Vickers hardness measurements. Microstructural and compositional analyses were performed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), At the same time, chemical bonding and phase composition were evaluated using FTIR-ATR and X-ray diffraction (XRD), respectively.

The AR group exhibited lower biaxial flexural strength (110.05 MPa ±33.91) and hardness (3.87 GPa ±0.30) compared to the SM group (295.09 MPa ±63.98 and 5.53 GPa ±0.14, respectively). EDS results indicated comparable elemental composition between groups. However, FTIR-ATR spectra revealed more pronounced crystalline-related peaks in the SM samples, and XRD analysis suggested reduced conversion of lithium metasilicate to lithium disilicate in the AR group. SEM observations demonstrated a more porous microstructure in the 3D-printed specimens.

Overall, the results confirm that lithium disilicate ceramics can be fabricated via robocasting. Nevertheless, the superior mechanical performance observed in the subtractive manufacturing group highlights current limitations of the additive approach. These differences are likely associated with incomplete phase transformation and increased porosity in the printed structures. Despite these challenges, the findings provide valuable insights into advancing sustainable and efficient ceramic fabrication strategies for biomedical and dental applications.

Clear Aligner Therapy (CAT) has seen rapid global adoption, with over 14 million patients treated to date. This growth entails a substantial environmental footprint, generating an estimated 1,456 tons of plastic waste from aligners and nearly 11,000 tons from non-recyclable 3D-printed resin models. The traditional thermoforming process is inherently inefficient, with up to 80% of the thermoplastic sheet becoming waste. Furthermore, each patient's dental treatment can require up to 100 aligners. During aligner manufacturing, significant material loss occurs if treatment plans are refined and unused trays are discarded. Environmental concerns extend beyond bulk waste to include microplastic and nanoplastic pollution. Studies indicate that aligners release approximately 11 microparticles per day into the oral cavity during use. The disposal of aligners and leftover manufacturing materials is a major challenge and difficult to solve. This problem is similar to the disposal of contaminated medical waste. One solution to avoid discarding aligners into the environment is incineration. However, this incineration process releases toxic compounds such as benzene and tetrahydrofuran, exacerbating the problem. To mitigate these impacts, the industry is adopting the "4R" framework (Reduce, Reuse, Recycle, Rethink). Key innovations include staged production to prevent oversupply and direct 3D printing, which eliminates the need for physical molds. Emerging research into biodegradable bioplastics and specialized recycling partnerships represents an essential step toward a circular economy in orthodontics.

Tooth loss triggers progressive alveolar bone resorption, reducing ridge volume by up to 60% within the first six months post-extraction and compromising future implant-supported rehabilitation. This review aims to evaluate the clinical, radiographic, and histological efficacy of crushed autologous dentin matrix in post-extraction alveolar socket preservation. A bibliographic search was conducted in PubMed, Scopus, and Google Scholar using the descriptors "autologous dentin graft", "socket preservation", and "demineralized dentin matrix", encompassing controlled clinical trials, histomorphometric studies, and radiographic analyses published within the last ten years. Results indicated that autologous dentin exhibits significant osteoconductive and osteoinductive properties, mediated by endogenous type I collagen and bone morphogenetic proteins preserved within its organic matrix. Histologically, biomaterial resorption occurs synchronously with vital bone apposition of high density and structural quality. Radiographically, dimensional maintenance of the alveolar ridge was statistically equivalent to that of commercial xenogeneic grafts, with consistent biocompatibility and no reported immunological rejection.  Autologous dentin represents a biologically robust, cost-effective, and environmentally sustainable alternative for socket preservation, reducing dependence on animal-derived biomaterials and converting biological waste into a high-value therapeutic resource thas aligns with circular economy principles.

Hydroxyapatite (HAp) is the main inorganic constituent of bone and dental tissues, providing rigidity and mechanical resistance. Due to its composition and crystalline structure, which are like those of natural bone mineral, this biomaterial exhibits excellent biocompatibility, bioactivity, and osteoconductivity. These characteristics make HAp the most widely researched bioceramic for use in hard tissue repair and tissue engineering [1]. This work aims to present a literature review of synthesis methodologies and clinical applications of hydroxyapatite in regenerative procedures. HAp synthesis methodologies define their final properties and can be divided into three categories: wet routes, dry routes, and biogenic extraction. Wet routes, such as chemical precipitation, the sol-gel method, and hydrothermal synthesis, are the most versatile and allow precise control over nanocrystal morphology and size [4]. The hydrothermal method, conducted under controlled pressure and temperature, allows the production of high-purity crystals. In this case, organic modifiers are used to produce needle- or rod-shaped particles. With dry routes in the solid state, thermal or mechanical energy is used
via milling to promote the reactions. Dry routes are preferred for large-scale production, although they offer less control over grain uniformity. In biogenic extraction, natural materials such as crustaceans, eggshells, and bovine bones are used. This route has sustainable and low-cost characteristics [5]. The applications of HAp in dentistry and medicine are vast, ranging from filling critical bone defects to coating metallic implants to accelerate osseointegration. In dentistry, HAp is used to treat dentin hypersensitivity, promote enamel remineralization, and prevent caries. As a platform for controlled drug release, its porous structure enables the adsorption of hydrophilic and hydrophobic molecules, and it is being investigated for the delivery of antibiotics and chemotherapeutic agents in osteosarcoma treatment [2]. Recent advances explore ionic doping of HAp with elements such as strontium, zinc, or magnesium to mimic the properties of human bone, improve mechanical resistance, and enhance the biomaterial's antibacterial properties. With additive manufacturing, such as 3D printing, it is possible to create customized scaffolds with controlled porosity for each clinical need [3]. Based on the literature, it is possible to conclude that hydroxyapatite is well established for clinical use and indispensable in regenerative surgeries. The evolution of synthesis techniques enables fine-tuning of their properties. Integration with technologies such as ion doping and 3D printing reduces the gap between synthetic substitutes and the complex functionality of bone tissue.

The growing production of synthetic textile materials has heightened environmental concerns, particularly due to the release of microplastics from nonwovens. In this context, agro-industrial waste such as chicken feathers stands out as a promising renewable source due to its high β-keratin content. This work investigates the production of nanostructured nonwovens by electrospinning from hydrolyzed keratin extracted from chicken feathers combined with cellulose acetate. The process enables transforming low-value-added waste into functional nanofibers with high surface area and adjustable properties. Polymer solutions containing different concentrations of keratin were prepared in an acetic acid/water solvent system and electrospun to obtain micro- and nanofibers. The materials produced were characterized by thermal analysis (TG/DTG, DTA, and DSC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The formulation containing 5% keratin showed greater uniformity and fewer structural defects. The results demonstrate that keratin acts as a natural additive that can partially replace synthetic polymers in nonwovens. In addition to reducing environmental impact, the developed material showed potential applications in the textile and biomedical, contributing to the valorization of poultry industry waste and to sustainable strategies aligned with the circular economy.

The success of oral rehabilitations with titanium (Ti) dental implants is intrinsically dependent on osseointegration, the biological mechanism that enables functional stability at the bone-implant interface [1]. This process is defined as the direct structural and functional connection between living bone and the surface of a functional loaded implant. However, long-term clinical success and accelerated biological response intrinsically depend on the biomaterial's surface properties [2]. This narrative literature review critically analyzes the state of the art of surface modification techniques in titanium dental implants, focusing on the evolution of topographical and physicochemical approaches, the transition to biofunctionalized surfaces, and the emerging role of nanotechnology. The review encompasses subtractive techniques such as sandblasting and acid etching (SLA), which enhance bone-implant contact (BIC) by up to 30%, as well as additive and bioactive coating methods that incorporate mineral components directly into the titanium oxide layer. Surface properties including roughness, wettability, surface charge, and zeta potential are examined as critical modulators of protein adsorption and cellular behavior. Special attention is given to the synergy between titanium, nanoscale hydroxyapatite, and bioactive peptide functionalization, a triad representing the current frontier in the quest for ideal osseointegration [4] [5]. This integrated approach aims to simultaneously promote osseointegration and prevent bacterial biofilm formation, addressing current clinical challenges in implant dentistry, particularly in patients with compromised bone quality or immunological conditions.

Osseointegrated dental implants made of commercially pure titanium are used to restore masticatory function and improve patients' aesthetics. Their performance depends on factors such as material, surgical technique, surface morphology, and insertion site. To increase initial stability, favor cellular interaction, and reduce osseointegration time, different surface treatments have been developed, making the process of bone integration more efficient and accelerating dental treatment [1,2].

The enhancement of chemical bonding at the interfaces between titanium implant surfaces and bone tissue has been widely investigated through surface modifications capable of partially mimicking the mineral composition of bone tissue. In this context, coatings based on silicon-doped hydroxyapatite show high bioactive potential, since the incorporation of silicate ions into the apatite lattice can favor cellular responses associated with osteoblastic adhesion, proliferation, and differentiation, contributing to tissue regeneration at the implant-bone interface [3]. 

The use of chemical deposition methods to obtain these coatings allows greater control over the morphology, composition, and stoichiometry of the formed layer, overcoming limitations frequently associated with conventional thermal processes, which may compromise the mechanical stability and adhesion of the coating to the metallic substrate [4]. This study contributes to the discussion on the development of biofunctional surfaces applied to orthopedic and dental implants, with emphasis on biomaterials engineering aimed at improving biological integration and functional durability.

The bioactive coating was produced on titanium substrates by chemical deposition, using samples of hydroxyapatite (HA) and hydroxyapatite partially substituted with silicon (HASi) under controlled conditions of atmosphere and precursor concentration, with immersion periods of 1, 3, and 5 days, aiming to ensure the homogeneity of the formed layer. Scanning electron microscopy analyses revealed a modified surface morphology in HASi compared with HA; energy-dispersive spectroscopy (EDS) detected silicon in the HASi samples; and X-ray diffraction results corroborated the presence of a crystalline phase associated with doped hydroxyapatite. Regarding the sessile-drop wettability test, the 3-day HASi sample showed a contact angle of 55.48°, lower than 90°, indicating hydrophilic behavior. In the roughness test, the mean Ra values for the HASi samples were 0.521 µm after 1 day, 0.287 µm after 3 days, and 0.135 µm after 5 days. In the bioactivity analysis, surface modification was observed, indicating probable bioactivity. 

It is concluded that titanium coating with hydroxyapatite partially substituted with silicon has potential to improve the surface bioactivity of osseointegrated implants. The presence of silicon, the formation of a stable crystalline phase, the morphological modification of the surface, the hydrophilic behavior, and the alterations observed after the bioactivity assay indicate that HASi may favor the interaction between the implant and bone tissue, contributing to more functional surfaces for dental and orthopedic applications.

The growing adoption of vat photopolymerization technologies in engineering, biomedical, and industrial applications has increased the demand for UV-curable resins with improved mechanical performance. Although commercial photopolymer resins offer excellent dimensional accuracy and surface quality, their limited toughness and torsional resistance remain significant challenges for structural applications. Recent studies have demonstrated that modifying resin formulations through the incorporation of secondary phases or reinforcing additives can improve mechanical behavior and expand their range of applications [1–3].

Torque resistance is a critical property for photopolymer resins employed in prototyping and functional component development. Although additive manufacturing is frequently used for visual models and dimensional validation, an increasing number of applications require prototypes to withstand rotational loads, assembly operations, threaded connections, and mechanical testing during product development. Insufficient torsional strength may lead to premature failure, cracking, or deformation, compromising the reliability of prototypes and limiting their use in engineering, medical, automotive, and industrial applications. Therefore, improving the torque resistance of UV-curable resins has become an important research objective, enabling the production of components with enhanced structural performance while maintaining the advantages of high-resolution additive manufacturing [2–3].

This study aimed to evaluate the feasibility of improving the torque resistance of UV-cured resins through the incorporation of different additive contents. Formulations containing 0%, 5%, 7%, 10%, and 20% additive concentrations were prepared and compared to investigate the influence of composition on hardness and torsional performance. The objective was to identify an optimal formulation capable of enhancing structural efficiency while maintaining processability and mechanical integrity.

The experimental methodology consisted of preparing resin blends with different additive concentrations followed by UV curing under controlled conditions. Torque resistance tests were performed to determine the maximum torsional load supported by each formulation. In addition, Shore D hardness measurements were conducted to evaluate surface rigidity and correlate stiffness with torsional performance. The mechanical efficiency of the materials was assessed through specific torque analysis, which normalizes the failure torque by the cross-sectional area of the specimens.

The results demonstrated a progressive improvement in hardness and torsional behavior as the additive content increased. The neat resin exhibited the lowest hardness values, while formulations containing 5%, 7%, and 10% additive showed gradual increases in rigidity. The 20% formulation achieved the highest Shore D hardness and exhibited the greatest torque resistance among all tested groups, indicating a significant improvement in load-transfer capability and structural performance. The specific torque analysis further confirmed that the 20% formulation provided the highest mechanical efficiency, demonstrating superior torsional strength relative to its cross-sectional area. These findings suggest that the incorporation of moderate additive concentrations promotes a more effective load distribution within the polymer network, resulting in enhanced mechanical performance.

It can be concluded that the addition of reinforcing phases to UV-curable resins significantly improves their torque resistance and hardness. Among the investigated formulations, the 20% additive content provided the best balance between stiffness and torsional performance, representing a promising approach for the development of photopolymer composites intended for structural and functional applications. The results indicate that controlled modification of UV resin systems can contribute to the development of stronger and more reliable materials for advanced additive manufacturing technologies [4–5].

This study evaluates the potential of biphasic calcium phosphate (BCP) scaffolds fabricated by 3D printing via robocasting for the regeneration of critical-sized defects in long bones. The scaffolds were engineered with an interconnected porous architecture to enhance osteoconductive properties. Physicochemical characterization included density and porosity measurements obtained through helium pycnometry, revealing a density of 2.98 ± 0.01 g/cm³ and a porosity of 48.5 ± 1.5%. Mechanical performance was assessed by uniaxial compression testing, demonstrating that the scaffolds possess sufficient compressive strength for load-bearing applications. Surface morphology and elemental composition were investigated using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), confirming the presence of a well-defined porous structure and the expected elemental constituents. X-ray Diffraction (XRD) analysis verified the crystalline phases of BCP. Overall, the findings indicate that the developed scaffolds exhibit biocompatibility and osteoconductivity, supporting guided bone regeneration and remodeling in critical defects of long bones. The combination of suitable mechanical properties and favorable surface characteristics highlights their potential for clinical translation in the treatment of extensive bone defects.