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The aim of this report was to digitize traditional denture relining using a digital duplication method, in addition to assessing the wear resistance of three‐dimensional (3D) printed denture teeth. A complete denture was relined using light body impression. The denture with impression was scanned yielding a standard tessellation language file that was designed to print the denture base and teeth. The printed teeth were fitted into the sockets of the printed denture base and then bonded using auto‐polymerized acrylic resins, followed by finishing and polishing. Dentures were inserted and fit and occlusion were adjusted as needed, and the patient was scheduled for follow‐up appointments at one week, three months, and six months. At each follow‐up visit, dentures were scanned using a 3Shape E3 desktop scanner and scans were superimposed. The occlusal wear was assessed in reference to the first scan after the denture insertion visit. The accuracy of the intaglio surface of dentures was within clinically acceptable limits. The clinical evaluation of inserted dentures in terms of retention, occlusion, esthetic, and patient satisfaction was encouraging. Using digital duplication, conventional dentures could be relined. The advantages of digital records include eliminating polymerization dimensional changes, and reducing cost and clinical time by minimizing the number of visits, which is particularly helpful with geriatric patients. [ABSTRACT FROM AUTHOR]

Aim: Radiotherapy is associated with cell depletion and loss of blood supply, which are linked to compromised bone healing. However, the molecular events underlying these effects at the tissue–implant interface have not been fully elucidated. This study aimed to determine the major molecular mediators associated with compromised osseointegration due to previous exposure to radiation. Materials and Methods: Titanium implants were placed in rat tibiae with or without pre‐exposure to 20 Gy irradiation. Histomorphometric, biomechanical, quantitative polymerase chain reaction (qPCR) and enzyme‐linked immunosorbent assay analyses were performed at 1 and 4 weeks after implantation. Results: The detrimental effects of irradiation were characterized by reduced bone–implant contact and removal torque. Furthermore, pre‐exposure to radiation induced different molecular dysfunctions such as (i) increased expression of pro‐inflammatory (Tnf) and osteoclastic (Ctsk) genes and decreased expression of the bone formation (Alpl) gene in implant‐adherent cells; (ii) increased expression of bone formation (Alpl and Bglap) genes in peri‐implant bone; and (iii) increased expression of pro‐inflammatory (Tnf) and pro‐fibrotic (Tgfb1) genes in peri‐implant soft tissue. The serum levels of pro‐inflammatory, bone formation and bone resorption proteins were greater in the irradiated rats. Conclusions: Irradiation causes the dysregulation of multiple biological activities, among which perturbed inflammation seems to play a common role in hindering osseointegration. [ABSTRACT FROM AUTHOR]

Purpose: To compare flexural strength, elastic modulus, and surface hardness of computer aided design and computer aided manufacturing CAD‐CAM milled, 3D‐printed, and heat‐polymerized denture base resins. Materials and methods: A total of 120 specimens were fabricated from heat‐polymerized acrylic resin (HP), milled resin (Avadent and IvoCad), and 3D‐printed resin (ASIGA, FormLabs, and NextDent). The specimens were divided into 6 groups according to the type of denture base material (n = 20/material) (10/flexural properties and 10/hardness). Flexural strength and elastic modulus of the specimens were evaluated by 3‐point bending test and surface hardness by Vickers hardness test. To test flexural properties, the specimens were fabricated according to ISO 20795‐1:2013 standards (64 × 10 × 3.3 ± 0.2 mm). The dimensions for hardness test were 15 × 10 × 2.5 ± 0.2 mm. Scanning electron microscope was used to evaluate the surface morphology of the fractured specimens. The means and standard deviations were calculated, followed by one‐way ANOVA and Tukey post‐hoc test (α = 0.05). Results: Milled resins showed significantly higher values for flexural strength, elastic modulus, and surface hardness, followed by HP and then 3D‐printed resins (p < 0.001). Within milled groups, flexural strength of AvaDent was significantly higher than IvoCad (p < 0.001), while elastic modulus and hardness didn't show significant difference. Within 3D‐printed resins, ASIGA showed the highest flexural strength and elastic modulus, insignificantly with FormLabs (p = 0.595) and significantly with NextDent (p = 0.008). ASIGA also showed significantly the highest hardness among the 3D‐printed groups. No significant difference was found between FormLabs and NextDent in flexural strength (p = 0.357), elastic modulus (p = 1.00), or surface hardness (p = 0.987). Conclusion: CAD‐CAM milled resins had greater flexural properties and hardness compared to heat‐polymerized acrylic resin and 3D‐printed resins. Although 3D‐printed samples showed the lowest values of tested properties, the flexural strength and modulus were above clinically acceptable values. [ABSTRACT FROM AUTHOR]

Purpose: The longevity of removable prostheses is mostly influenced by the properties of the used materials. The ability of the material to withstand high occlusal loads without deformation can enhance patient satisfaction and quality of life. This in vitro study aimed to investigate the wear and fracture resistance of three‐dimensional (3D)‐printed teeth compared with commercially available acrylic resin teeth. Materials and methods: A total of 40 prefabricated acrylic teeth and 40 3D‐printed teeth were prepared in two forms: anatomical for fracture resistance or flat for wear resistance (n = 10). For wear evaluation, specimens were scanned at baseline and then subjected to thermal cycling (10,000 cycles). This was followed by a chewing simulator (60,000 cycles) against either metal or natural tooth. Then, the specimens were scanned again. Wear analysis was performed by superimposing the standard tessellation language (STL) files from baseline and the final scans with the aid of GOM Inspect 2020 software. Fracture resistance was assessed with a universal testing machine at a crosshead speed of 0.5 mm/min before and after thermal cycling. Data were analyzed with two‐independent t‐test and two‐way ANOVA (α = 0.05). Results: The 3D‐printed teeth showed significantly lower wear resistance than the prefabricated ones with both antagonists (metal, p = 0.049; natural tooth, p = 0.021). The fracture resistance of the 3D‐printed teeth was significantly higher than that of the prefabricated teeth before thermocycling (p = 0.042). After thermal cycling, the fracture resistance of both groups was decreased with no significant differences between them (p = 0.266). Conclusions: The 3D‐printed teeth showed lower wear resistance and higher fracture resistance than the prefabricated ones. Thermal cycling negatively affected the fracture resistance of 3D‐printed teeth. [ABSTRACT FROM AUTHOR]

PURPOSE. This study aimed to evaluate the effect of incorporating zirconium oxide nanoparticles (nano-ZrO2) in polymethylmethacrylate (PMMA) denture base resin on flexural properties at different material thicknesses. MATERIALS AND METHODS. Heat polymerized acrylic resin specimens (N = 120) were fabricated and divided into 4 groups according to denture base thickness (2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm). Each group was subdivided into 3 subgroups (n = 10) according to nano-ZrO2 concentration (0%, 2.5%, and 5%). Flexural strength and elastic modulus were evaluated using a three-point bending test. One-way ANOVA, Tukey's post hoc, and two-way ANOVA were used for data analysis (a = .05). Scanning electron microscopy (SEM) was used for fracture surface analysis and nanoparticles distributions. RESULTS. Groups with 0% nano-ZrO2 showed no significant difference in the flexural strength as thickness decreased (P = .153). The addition of nano-zirconia significantly increased the flexural strength (P < .001). The highest value was with 5% nano-ZrO2 and 2 mm-thickness (125.4 ± 18.3 MPa), followed by 5% nano-ZrO2 and 1.5 mm-thickness (110.3 ± 8.5 MPa). Moreover, the effect of various concentration levels on elastic modulus was statistically significant for 2 mm thickness (P = .001), but the combined effect of thickness and concentration on elastic modulus was insignificant (P = .10). CONCLUSION. Reinforcement of denture base material with nano-ZrO2 significantly increased flexural strength and modulus of elasticity. Reducing material thickness did not decrease flexural strength when nano-ZrO2 was incorporated. In clinical practice, when low thickness of denture base material is indicated, PMMA/nano-ZrO2 could be used with minimum acceptable thickness of 1.5 mm. [ABSTRACT FROM AUTHOR]

Purpose: To compare the strength, surface roughness, and hardness of newly introduced permanent three-dimensional (3D)-printed resin in comparison with computer-aided design and computer-aided manufacturing (CAD-CAM) milled materials., Materials and Methods: Three 3D-printed resins (NextDent C&B, Formlabs Permanent Crown, and VarseoSmile Crown plus) and two CAD-CAM milled (IPS e.max ZirCAD LT and VITA Enamic) resins were used to fabricate discs specimens. A total of 200 disc specimens were fabricated according to manufacturer recommendations. Within each group, half of the specimens were subjected to thermal cycling (5°C-55°C, the 30 s, 5000 cycles). Aged and nonaged specimens were evaluated for biaxial flexural strength (BFS), surface roughness, and hardness. Results were statistically analyzed using analysis of variance (ANOVA) and t-tests (α = 0.05)., Results: Significant differences (p < 0.05) were observed in the BFS, surface roughness, and hardness between the 3D-printed and milled groups, before and after thermal aging. Overall, the CAD-CAM milled ceramic group had superior strength, surface roughness, and hardness when compared to all other groups (p < 0.001), except for surface roughness after thermal aging, which was similar in all groups (p = 0.063). Within each group, there was no significant difference (p > 0.05) in surface roughness after thermal aging. BFS values of 3D-printed materials were statistically similar. In terms of surface roughness, Formlabs specimens displayed the highest value before and after thermal cycling, when compared to other 3D-printed materials. Regarding hardness, the VarseoSmile Crown plus group demonstrated the highest values compared to other 3D-printed materials, before and after thermal cycling., Conclusion: Permanent 3D-printed resins have lower strength than CAD-CAM milled materials. 3D-printed permanent resin materials exhibited high roughness and comparable hardness to CAD-CAM materials. Thermal aging negatively affected the properties of 3D-printed permanent crowns. Owing to the low strength of 3D-printed permanent resins, they may not be recommended for clinical practice until further improvements in flexural strength are made to meet clinical standards., (© 2024 by the American College of Prosthodontists.)

Purpose: The aim of the study was to investigate the effect of surface treatment and repair materials on the flexural strength of repaired 3D-printed denture base resins after thermal aging., Materials and Methods: Bar-shape specimens (64 × 10 × 3.3 mm) were designed as intact (control) specimens while repair specimens were printed in sections with 2.5 mm space for repair material. Printing was performed with either ASIGA or NextDent denture base material. In each material, one group received no surface treatment, while other repair groups were subjected to one of three surface treatments: (1) monomer application, (2) aluminium oxide particles-abrasion, or (3) both methods (aluminum oxide particles-abrasion and monomer application). Pairs were fixed in a customized mold then repaired with either autopolymerizing acrylic resin or flowable composite (n = 9). Repaired specimens were incubated for 48 h at 37°C in distilled water and then subjected to thermal cycling (5000 cycles). A 3-point bending test was used to evaluate the flexural strength using a universal testing machine, and mode of failure determined followed by fractured surface analysis using scanning electron microscope. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05)., Results: Both resin materials showed a significant decrease in the flexural strength of repaired specimens when compared to control ones (p < 0.001). Groups with no surface treatment had significantly lower flexural strength than those with surface treatment (p < 0.001). Groups treated with monomer application, and with aluminum oxide particles abrasion plus monomer application had similar flexural strength values (p > 0.05), which were higher than those treated with aluminum oxide particles abrasion alone (p < 0.001). Specimens repaired with composite resin showed higher flexural strength than those repaired with auto-polymerized resin (p < 0.05) however, specimens treated with aluminum oxide particles abrasion alone had similar values for both repair materials (p = 0.95). Adhesive failure was dominant in all repaired groups with auto-polymerized while cohesive and mixed were dominant with composite repair groups., Conclusion: Surface treatment improved the repair strength of 3D-printed denture base resins. Using composite resin for repair shows better strength with dominant cohesive and mixed failure suggesting that surface treatment and composite repair are suitable procedures for 3D-printed denture base repair., (© 2024 by the American College of Prosthodontists.)

Purpose: This study aimed to evaluate the effect of incorporating zirconium oxide nanoparticles (nano-ZrO 2 ) in polymethylmethacrylate (PMMA) denture base resin on flexural properties at different material thicknesses., Materials and Methods: Heat polymerized acrylic resin specimens (N = 120) were fabricated and divided into 4 groups according to denture base thickness (2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm). Each group was subdivided into 3 subgroups (n = 10) according to nano-ZrO 2 concentration (0%, 2.5%, and 5%). Flexural strength and elastic modulus were evaluated using a three-point bending test. One-way ANOVA, Tukey's post hoc, and two-way ANOVA were used for data analysis (α = .05). Scanning electron microscopy (SEM) was used for fracture surface analysis and nanoparticles distributions., Results: Groups with 0% nano-ZrO 2 showed no significant difference in the flexural strength as thickness decreased ( P = .153). The addition of nano-zirconia significantly increased the flexural strength ( P < .001). The highest value was with 5% nano-ZrO 2 and 2 mm-thickness (125.4 ± 18.3 MPa), followed by 5% nano-ZrO 2 and 1.5 mm-thickness (110.3 ± 8.5 MPa). Moreover, the effect of various concentration levels on elastic modulus was statistically significant for 2 mm thickness ( P = .001), but the combined effect of thickness and concentration on elastic modulus was insignificant ( P = .10)., Conclusion: Reinforcement of denture base material with nano-ZrO 2 significantly increased flexural strength and modulus of elasticity. Reducing material thickness did not decrease flexural strength when nano-ZrO 2 was incorporated. In clinical practice, when low thickness of denture base material is indicated, PMMA/nano-ZrO 2 could be used with minimum acceptable thickness of 1.5 mm., (© 2021 The Korean Academy of Prosthodontics.)