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Statement of Problem: Bioglasses are a series of biocompatible dental materials, which are considered as light conducting inserts in resin composite restorations. Consequently, their chemical stability is more essential when they are used in conjunction with resin composite. Objectives: The aim of this study was to evaluate and compare the chemical stability of Bioglass with dental porcelain and resin composite by determining the amount of released K+, Na+, Ca2+ ions and silicone elements from these materials as a result of exposure to tested solutions with different pH levels including: Sodium Bicarbonate [SB, (pH=9.2)], Sodium Buffer Lactate [SBL, (pH=2.4)], Acetic Acid [AA, (pH=2.4)], and Distilled Water [DW, (pH=6.2)]. Materials and Methods: In this experimental study, forty 2.0 × 4.0 cylindrical rods for each tested material group (Dental porcelain, Resin composite and Bioglass) were prepared. They were divided into four subgroups of 10 rods each, which immersed in one of the four testing solutions in a designated container. The containers were stored at 50°C and 100% humidity for one week. The released ions were measured by using a spectrophotometer (µg/cm2/ml). The data were statistically analyzed by nonparametric Kruskal-Wallis H test. Results: It was observed that the tested materials released ions at different levels of concentration. The significant amounts of Sodium, Calcium, and Silicon ions release were measured in Bioglass subgroups in all the tested solutions (p < 0.001). Potassium ion release from dental porcelain was the largest in all solutions except for AA in which Bioglass had the greatest potassium ion release (p < 0.001). Conclusions: A greater structural instability was observed for Biogalss group than dental porcelain and resin composite in testing solutions with different pH .levels

Purpose: This study aimed to investigate the tensile bond strength between soft relining materials and different denture base materials., Materials and Methods: The study was conducted in accordance with ISO 23401:2023. A total of 288 rectangular specimens (10L × 10H × 20W mm) were fabricated from various denture base materials, including a heat-compression polymethylmethacrylate (PMMA), two types of milled PMAA, and three types of 3D-printed resins, with bonding using two chairside soft reline materials (Coe-Soft and Lynal). Specimens were placed in distilled water for 24 h before applying tensile force at a 5 mm/min crosshead speed. The tensile bond strength values (MPa) were calculated at maximum tensile force (N) before failure. Two-way ANOVA and post hoc multiple comparison tests were used to assess the effect of denture base and soft reline materials on the tensile bond strength (α = 0.05)., Results: A significant difference in the tensile bond strength was found among the different types of denture base materials (p < 0.001), regardless of relining material type. Lynal-relined milled IvoBase demonstrated the highest tensile bond strength (0.5 ± 0.06 MPa), followed by Lynal-relined milled Lucitone (0.44 ± 0.03 MPa), both of which are clinically acceptable as they are equal or greater 0.44 MPa. The lowest tensile bond strength was detected in Lynal-relined 3D printed FotoDent (0.09 ± 0.02 MPa). Lynal exhibited significantly higher tensile bond strength (p < 0.05) than Coe-Soft soft reline material when bonded to PMMA bases; however, there was no significant difference between Lynal and Coe-Soft when bonded to 3D-printed base materials (p > 0.05)., Conclusions: The tensile bond strength between soft relining materials and denture bases is material-dependent, influenced by both the type of denture base material and the type of soft relining material used., (© 2024 by the American College of Prosthodontists.)

Statement of Problem: The impact of thermal cycling on the flexure strength of contemporary denture base materials remains inadequately understood despite its crucial role in determining the long-term performance of complete dentures., Purpose: The purpose of this in vitro study was to evaluate the flexural strength of different CAD-CAM denture base materials and the effects of thermal cycling., Material and Methods: A total of 120 rectangular specimens were fabricated from 6 denture base materials according to the International Organization for Standardization (ISO) 20795-1:2013 standard: a heat-compressed PMMA ([Lucitone 199 [C-L199]), 2 brands of milled material (Ivotion Base [M-IB] and Lucitone Digital Fit [M-LDF]), and 3 types of 3- dimensionally (3D) printed material (Lucitone Digital Print [P-LDP], Flexcera Base [P-FB], and FotoDent Dentures [P-FD]). Specimens were divided into 2 subgroups of 10; half underwent thermocycling, half did not. Thermally cycled specimens were immersed in distilled water at 37 °C for 2 days, followed by 5000 thermal cycles at 5 and 55 ºC, with a dwell time of 30 seconds. They were then subjected to a 3-point flexural strength test. Two-way ANOVA, followed by post hoc Tukey multiple comparison tests were used to assess the effect of material type and the thermal cycling process on the flexural strength of denture base materials (α=.05)., Results: All materials met the ISO standard of 65 MPa flexural strength, except for thermal cycled P-FB. A significant difference (P<.05) in flexure strength value was found among various denture base materials without thermal cycling (M-LDF>M-IB≈P-FD≈P-LDP>C-L199≈ P-FB) and with thermal cycling (M-LDF> M-IB≈P-FD>P-LDP≈C-L199>P-FB). The flexural strength of tested materials was reduced significantly (P<.05) with thermal cycling., Conclusions: Three-dimensionally printed denture base materials have a flexural strength value similar to or less than that of milled denture base materials. Thermal cycling impacts the flexural strength of denture base materials., (Copyright © 2024 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: This study compared the fracture strength of single lithium disilicate implant-supported crowns fabricated on two-piece abutments with various materials: ceramic-reinforced PEEK, zirconia, and lithium disilicate., Materials and Methods: Thirty-six implants were embedded in acrylic cylinders. A two-piece abutment and a crown were designed following a pre-operation scan for a maxillary left central incisor. The designed crown was used to fabricate 36 lithium disilicate crowns. The designed abutment was used to manufacture 36 abutments from 3 materials, 12 each: (A) zirconia; (B) lithium disilicate; and (C) ceramic-reinforced PEEK. Abutments were surface treated and bonded on the titanium base abutments with resin cement. Then, lithium disilicate crowns were bonded on the assigned abutments. Specimens were then subjected to dynamic loading for 1,200,000 cycles. The fracture strength (N) of the assembly was assessed using a universal testing machine. One-way ANOVA followed by multiple comparison tests was used to evaluate the effect of abutment material on the fracture strength of single implant-supported restorations at a significance of .05., Results: The average fracture strength for the groups with zirconia, PEEK, and lithium disilicate two-piece abutments were 1362N ± 218N, 1235N ± 115N, and 1472N ± 171N, respectively. There was a significant (p < 0.05) difference in fracture strength among the groups. The lithium disilicate group had significantly higher fracture strength (p = 0.0058) than the group with PEEK; however, there was no significant (p > 0.05) difference between the other groups., Conclusions: Two-piece abutments restored with lithium disilicate crowns investigated in the study have the potential to withstand the average physiological occlusal forces in the anterior region., (© 2024 by the American College of Prosthodontists.)

Purpose: This study evaluated the fracture resistance of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate crown, onlay, and non-anatomical occlusal veneer (A-OV) with and without margin fabricated., Materials and Methods: Sixty-four CAD-CAM lithium disilicate restorations were designed as (1) complete coverage crown (CCC); (2) A-OV with margin; (3) non-A-OV with margin (NA-OV-M); and (4) non-A-OV without margin (NA-OV-NM), 16 of each. Restorations were crystallized and adhesively luted to resin dies using resin cement. Specimens were then subjected to 400,000 cycles of chewing in a mastication simulator. A universal testing machine was used to apply a compressive load at a crosshead speed of 1 mm/min to the long axis of the tooth with a stainless-steel sphere until fracture occurred. One-way ANOVA followed by post hoc tests were used to assess the impact of preparation design on the fracture load of CAD-CAM lithium disilicate restorations., Results: The highest fracture load was recorded for CAD-CAM lithium disilicate indirect restorations for non-A-OVs preparation with margin (2549 ± 428 N) and onlay (2549 ± 293 N) and the lowest fracture load was recorded for CCCs (2389 ± 428 N); however, there was no significant (p = 0.640) between groups., Conclusions: CAD-CAM lithium disilicate restorations fabricated for anatomical and non-A-OV preparation display a fracture resistance similar to CCCs. Conservative partial coverage restorations may be considered an acceptable approach for posterior teeth., (© 2024 by the American College of Prosthodontists.)

Purpose: This study aimed to assess the fracture resistance of monolithic zirconia-reinforced lithium silicate laminate veneers (LVs) fabricated on various incisal preparation designs., Materials and Methods: Sixty maxillary central incisors with various preparation designs were 3D-printed, 15 each, including preparation for: (1) LV with feathered-edge design; (2) LV with butt-joint design; (3) LV with palatal chamfer; and (4) full-coverage crown. Restorations were then designed and manufactured from zirconia-reinforced lithium silicate (ZLS) following the contour of a pre-operation scan. Restorations were bonded to the assigned preparation using resin cement and following the manufacturer's instructions. Specimens were then subjected to 10,000 thermocycles at 5 to 55°C with a dwell time of 30 s. The fracture strength of specimens was then assessed using a universal testing machine at a crosshead speed of 1.0 mm/min. One-way ANOVA and Bonferroni correction multiple comparisons were used to assess the fracture strength differences between the test groups (α = 0.001). Descriptive fractographic analysis of specimens was carried out with scanning electron microscopy images., Results: Complete coverage crown and LV with palatal chamfer design had the highest fracture resistance values (781.4 ± 151.4 and 618.2 ± 112.6 N, respectively). Single crown and LV with palatal chamfer had no significant difference in fracture strength (p > 05). LV with feathered-edge and butt-joint designs provided significantly (p < 05) lower fracture resistance than complete coverage crown and LV with palatal chamfer design., Conclusion: The fracture resistance of chairside milled ZLS veneers was significantly influenced by the incisal preparation designs tested. Within the limitation of this study, when excessive occlusal forces are expected, LV with palatal chamfer display is the most conservative method of fabricating an indirect restoration., (© 2023 by the American College of Prosthodontists.)

Purpose: This in vitro study evaluated the fracture strength of screw-retained zirconia crowns connected to zirconia (Zr) and titanium (Ti) implants after undergoing a simulation of 5 years of clinical use., Materials and Methods: Forty-eight screw-retained zirconia crowns were fabricated and assembled on four implant systems, with 12 in each group: (1) Zr implant (pure ceramic; Straumann AG) (PZr); (2) Zr implant (NobelPearl; Nobel Biocare) (NPZr); (3) Ti-Zr implant (Bone Level Roxolid; Straumann AG) (RSTiZr); (4) Ti implant (Conical Connection PMC; Nobel Biocare) (NRTi). Crowns were luted to their associated abutments using resin cement and then torqued to their assigned implants at the recommended torque value. Specimens were subjected to dynamic loading for 1,200,000 loading cycles. Fracture strength, measured in Newtons (N), was tested under static compression load using a universal testing machine at an angle of 30°. One-way ANOVA and Tukey's multiple comparisons post hoc test were used to compare the mean fracture values between the groups at a significance level of 0.05., Results: The average fracture strengths for the RSTiZr and NRTi groups were 1207 ± 202 and 1073 ± 217 N, respectively, which was significantly (p < 0.0001) higher than the PZr and NPZr groups (712 ± 76 and 571.6 ± 167 N, respectively). However, no significant difference was found between the fracture strength value of RSTiZr and NRTi (p = 0.260) or PZr and NPZr (p = 0.256) groups., Conclusions: Zirconia crowns connected to Zr implants have the potential to withstand the average physiological occlusal forces which occur in the anterior and premolar regions., (© 2023 by the American College of Prosthodontists.)

Purpose: To assess the shade match ability of four varieties of all-ceramic crowns to a neighboring bilayered lithium disilicate crown., Material and Methods: A dentiform was used to fabricate a bilayered lithium disilicate crown on the maxillary right central incisor, following the anatomy and shade of a selected natural tooth. Two crowns (one full-contour, one cutback) were then designed on a prepared maxillary left central incisor, following the contour of the neighboring crown. The designed crowns were used to manufacture monolithic lithium disilicate, bilayered lithium disilicate, bilayered zirconia, and monolithic zirconia crowns, 10 each. An intraoral scanner and a spectrophotometer were used to assess the frequency of matched shades and to calculate the color difference (ΔE) between the two central incisors at the incisal, middle, and cervical thirds. Kruskal-Wallis and two-way ANOVA were used to compare the frequency of matched shades and ΔE values, respectively (α = 0.05)., Results: There was no significant (p > 0.05) difference in frequencies of matched shades for each group at the three sites; except bilayered lithium disilicate crowns. Bilayered lithium disilicate crowns had significantly (p < 0.05) higher match frequency than monolithic zirconia at the middle third. The ΔE value was not significantly (p > 0.05) different among the groups at the cervical third. However, monolithic zirconia had significantly (p < 0.05) higher ΔE values than bilayered lithium disilicate and zirconia at the incisal and middle thirds., Conclusions: Bilayered lithium disilicate and zirconia appeared to most closely match the shade of an existing bilayered lithium disilicate crown., (© 2023 by the American College of Prosthodontists.)

Purpose: To evaluate fracture load values of five types of interim CAD/CAM crowns with and without thermocycling., Materials and Methods: A complete coverage crown was designed on a mandibular first molar with a uniform 1.5-mm axial and occlusal reduction, and the STL file was exported to manufacture 100 crowns using five materials (20 crowns per material): ZCAD Temp Esthetic (SM-ZCAD; Harvest Dental); Telio CAD (SM-TCAD); P pro Crown and Bridge (AM-PPRO); E-Dent 400 C&B MHF (AM-EDENT); and DENTCA Crown & Bridge (AM-DENTCA). Each group was then divided into two subgroups: before and after thermocycling (10 cornws per subgroup). The STL file of the mandibular first molar die was used to manufacture 100 resin dies. Each die was assigned to one interim crown. Interim crowns were then luted to their assigned die using a temporary luting agent. The fracture strength of crowns was then assessed using a universal testing machine at a crosshead speed of 2 mm/minute. Two-way ANOVA followed by Tukey multiple comparations post-hoc tests were used to assess the effect of material choice and thermocycling process on the fracture strength of interim crowns (α = .05)., Results: Material choice and the thermocycling process exerted a significant (P < .001) impact on the fracture strength of interim crowns. However, the interaction between these two factors did not yield a statistically significant effect (P = .176)., Conclusions: Within the limitations of this study, the type of interim materials and thermocycling process have a significant impact on the fracture strength of interim crowns.

Purpose: This in vitro study aimed to compare flexural strength, surface roughness, and biofilm formation of ceramic-reinforced polyetheretherketone (PEEK) with conventionally heat-compressed and milled polymethylmethacrylate (PMMA) denture base materials., Materials and Methods: Thirty strips (6.4 mm × 10 mm × 3 mm) and 30 discs (10 mm × 1 mm) were fabricated from a heat-compressed PMMA, milled PMMA, and ceramic-reinforced PEEK, 10 each. One surface of each sample was polished to mimic the laboratory procedure for denture base materials. Strips were then subjected to a three-point bend test using a universal testing machine at a crosshead speed of 5.0 mm/min. An optical profilometer was used to assess the Ra value (mm) of the discs on polished and unpolished sides. Biofilm formation behavior was analyzed by measuring the colony-forming unit (CFU)/mL of Candida albicans on the unpolished surface of the discs. One-way ANOVA followed by Tukey multiple comparison tests were used to compare the flexural strength, Ra value, and biofilm formation of the studied materials (a = 0.05)., Results: Ceramic-reinforced PEEK showed significantly higher flexural strength (178.2 ± 3.2 MPa) than milled PMMA (89.6 ± 0.8 MPa; p < 0.001) and heat-compressed PMMA (67.3 ± 5.3 MPa; p < 0.001). Ceramic-reinforced PEEK exhibited a significantly higher Ra value than the other groups on unpolished sides; however, the polishing process significantly reduced the Ra values of all studied groups (p < 0.05). There was no significant difference in C. albicans adhesion among the groups (p < 0.05)., Conclusion: The flexural strength of tested materials was within acceptable limits for clinical use as a denture base material. Ceramic-reinforced PEEK had the highest surface roughness; however, its similarity in biofilm formation to other groups indicates its clinical acceptability as denture base material., (© 2023 by the American College of Prosthodontists.)

Purpose: Gaining knowledge on the extent of digital technology implementation in dental education and the barriers to it will help inform future directions to promote the use of such technology and will enhance dental education. This study aimed to investigate the utilization of digitally fabricated removable prostheses and the potential obstacles to implementing such technology in US dental schools., Methods: A survey was developed and distributed to the restorative dentistry department chairs and postdoctoral prosthodontic program directors. The survey delivery protocol included follow-up emails 1 week, 3 weeks, and 4 weeks after the initial email. The collected data were analyzed descriptively., Results: The response rate was 85% and 45% for predoctoral and postdoctoral prosthodontic programs, respectively. The results showed that 88.06% of the predoctoral programs and 95.65% of the postdoctoral prosthodontic programs implement digital complete dentures in the curriculum; however, the digital removable partial dentures implementation rate was recorded at 70.77% in predoctoral programs and 61.9% in postdoctoral prosthodontic programs., Conclusions: Dental schools are challenged by cost, design software limitations, IT and laboratory support, and faculty training. Multifaceted support is instrumental in further implementing digital removable prosthodontics into dental education., (© 2023 The Authors. Journal of Dental Education published by Wiley Periodicals LLC on behalf of American Dental Education Association.)

Statement of Problem: Custom-made angled LOCATOR abutments have been used to compensate for the angulation of implants placed to support removable prostheses; however, their retention forces and the impact of mastication loading on retention have yet to be well addressed., Purpose: The purpose of this in vitro study was to evaluate the retention force of custom-made LOCATOR abutments for implants placed at 0-, 15-, and 30-degree angulations with prefabricated abutments and to investigate the effect of mastication load on retention., Material and Methods: Implant analogs were placed at the first molars of 40 maxillary typodonts, and 40 LOCATOR abutments were fabricated. Twenty implant analogs were placed at 0 degrees, 10 of which received prefabricated LOCATOR abutments and 10 of which received custom abutments. The remaining 20 implant analogs were placed at 15- and 30-degree angulations (n=10), and custom LOCATOR abutments were fabricated on them. A denture analog was digitally designed and manufactured from polymethyl methacrylate (PMMA) billets. Metal housings were then picked up using PMMA. The specimens were subjected to 2 rounds of 120 000 cycles of mastication loading. Retention force was assessed before and after each round of mastication loading using a universal testing machine. The wear of nylon inserts before and after mastication loading was accessed with a digital stereomicroscope. A 2-way ANOVA followed by the Tukey HSD test was used to determine the impacts of LOCATOR abutment type and times of mastication loading on the retention forces of the denture base (α=.05)., Results: No significant difference in retention forces was found between prefabricated LOCATOR and custom abutments (placed at 0-, 15-, and 30-degree angulations) regardless of mastication loading (P>.05). The retentive force values of all groups increased significantly after the first round of mastication loading and decreased significantly to the initial level after the second round of mastication loading (P<.05)., Conclusions: Mastication loading impacted the retention force of both prefabricated and custom LOCATOR abutments; however, no significant difference in retention forces was found among various types of abutments., (Copyright © 2023 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Novel 3-dimensionally printed resin and milled polymethyl methacrylate materials have been marketed for computer-aided design and computer-aided manufacturing (CAD-CAM) denture base fabrication. However, information on the flexural strength of digitally fabricated denture base material is limited, and little is known about how they are affected by a hard-reline procedure., Purpose: The purpose of this in vitro study was to assess the flexural strength of 6 digitally manufactured denture base materials and to assess the effect of a hard-reline procedure on their flexural strength., Material and Methods: A total of 140 strips of denture base material were fabricated from a conventional heat-polymerized polymethyl methacrylate (L199), 3 brands of milled polymethyl methacrylate (IBC, DSL, and ADH), and 3 brands of 3D-printed resin (DFD, ADB, and DrFD) (n=20). Ten specimens in each group did not receive any treatment, and 10 were relined with a hard-reline material (ProBase Cold Trial Kit). Specimens were then subjected to a 3-point flexural strength test using a universal testing machine at a crosshead speed of 5.0 mm/min. A 1-way ANOVA test followed by the Tukey multiple comparison test was used to detect the difference in flexural strength and the strain at fracture of the different types of denture base materials (α=.05). The comparison of flexural strength between with and without hard-reline was analyzed using an unpaired t test (α=.05)., Results: All materials, with or without the hard-reline, met the International Organization for Standardization (ISO) 20 795-1:2013 standard for flexural strength (65 MPa). The milled materials (DSL>IBC≈ADH) showed higher flexural strength than the 3D-printed or conventional materials (DrFD>DFD≈ADB≈L199) without a hard-reline. No statistical difference in flexural strength was found among the hard-relined denture base materials (P=.164). All 3 milled materials showed reduced flexural strength after relining, while the relined conventional (L199) and 3D-printed materials (DFD and ADB) showed notably higher flexural strength; printed DrFD showed no significant difference (P=.066). In terms of strain at fracture, the milled materials displayed higher values than those of the conventional or 3D-printed materials (P<.05)., Conclusions: All digitally fabricated denture base materials were within acceptable limits for clinical use, even after hard relining. Flexural strength was highly dependent on the type of material. Hard relining affected the flexural strength of most of the digitally fabricated denture base materials., (Copyright © 2023 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Introduction: The continual evolution of dental education, dental practice and the delivery of optimal oral health care is rooted in the practice of leadership. This paper explores opportunities and challenges facing dental education with a specific focus on incorporating the use of artificial intelligence (AI)., Methods: Using the model in Bolman and Deal's Reframing Organizations, the Four Frames model serves as a road map for building infrastructure within dental schools for the adoption of AI., Conclusion: AI can complement and boost human tasks and have a far-reaching impact in academia and health care. Its adoption could enhance educational experiences and the delivery of care, and support current functions and future innovation. The framework suggested in this paper, while specific to AI, could be adapted and applied to a myriad of innovations and new organizational ideals and goals within institutions of dental education., (© 2022 The Authors. Journal of Dental Education published by Wiley Periodicals LLC on behalf of American Dental Education Association.)

This report describes the rehabilitation of worn dentition by using a complete digital workflow on a nonhinged simulated patient. A dentiform was used to represent an individual with loss of occlusal vertical dimension. Interim restorations were designed following the simulated patient's midline, interpupillary line, and ala-tragus line and a defined central incisal edge position, posterior maxillary teeth central groove, and buccal cusp position of posterior maxillary teeth. The definitive restorations were then designed and fabricated by following the contour of the interim restorations., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: The bond between resin cement and zirconia is essential to the long-term retention of a zirconia crown. However, it is unclear if the existing methods provide a long-term bond between resin cement and zirconia., Purpose: The purpose of this in vitro study was to evaluate the effects of a zirconia etching solution on the shear bond strength between zirconia and resin cement., Material and Methods: Sixty yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) disks (Ø8×5 mm) were divided into 4 groups (n=15). Each group was then treated with 1 of the following methods: airborne-particle abraded with 50-μm Al 2 O 3 (AA); etched with zirconia etching solution (ZES); airborne-particle abraded with 50-μm Al 2 O 3 and then etched with ZES (AA-ZES); etched with ZES and then airborne-particle abraded with 50-μm Al 2 O 3 (ZES-AA). Sixty composite resin cylinders (Ø2.3×2.4 mm) were luted to the zirconia disks with a self-adhesive resin cement under constant load and then light-polymerized for 40 seconds. Specimens were stored in a 37 °C incubator in distilled water for 24 hours and then thermocycled for 1000 cycles between 5 °C and 55 °C. A universal testing machine with a crosshead speed of 0.5 mm/min was used to measure the shear force (N). The shear bond strength (MPa) was then calculated. One-way ANOVA was used to compare the mean shear bond strength among the groups (α=.05). The failure mode was evaluated by using light microscopy at ×90 magnification and categorized as an adhesive, cohesive, or mixed failure., Results: Mean ±standard deviation shear bond strength for AA, ZES, AA-ZES, and ZES-AA groups were 9.9 ±2.6, 8.9 ±2.9, 9.6 ±3.9, and 11.0 ±2.3 MPa, respectively. There was no significant difference among the treatment groups (P>.05)., Conclusions: A zirconia etching solution did not significantly improve the shear bond strength between zirconia and resin cement compared with airborne-particle abrasion with Al 2 O 3 ., (Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: The purpose of this study was to determine how students perceived the use of a 3D video microscope (3D VM), in comparison to conventional methods, for providing instruction on fixed prosthodontics procedures and issuing feedback on student performance., Methods: From May until December of 2020, University at Buffalo School of Dental Medicine's second-year students were introduced to fixed prosthodontics. During May and June, a 3D VM was used to live-stream psychomotor skill demonstrations via a web-based software. After each procedure, students were asked to complete a short survey regarding their experience with the training. From August until December 2020, students received feedback via: 1. The conventional method, in which faculty use magnification loupes to assess student's perfromance. 2. A 3D VM. Irrespective of the method used, feedback was given following the same defined rubrics. At the conclusion of the semester, students completed a survey comparing their experiences in receiving instruction and feedback. The data were gathered and analyzed descriptively. The chi-square test (α = .05) was used to gauge if students' gender had an impact on their perception of feedback methods., Results: More than 94% of students participated in the surveys. The majority of students had a positive reaction toward the use of the 3D VM for live web-based training. In regard to receiving feedback, 63% opined that the 3D VM was more effective than the conventional method. Additionally, 80% of students felt that the 3D VM was effective in maintaining physical distance during skill evaluations., Conclusion: This study examined the use of a 3D VM for teaching psychomotor skills and providing student feedback and compared it to the conventional method. It was found that the use of the 3D VM was perceived positively by students. Gender had no significant impact on students' attitudes toward the teaching and feedback methods., (© 2021 American Dental Education Association.)

Purpose:  To compare the fracture strength of three-unit provisional partial fixed dental prostheses (FDPs) fabricated by an indirect-direct technique from poly(methylmethacrylate) (PMMA) through digital and conventional workflows, and FDPs fabricated by a direct technique using Bisacryl (BisA) and externally reinforced BisA., Materials and Methods:  Forty partially edentulous typodonts with a missing mandibular left first molar and standard preparations on mandibular left second premolar and molar were used to fabricate three-unit provisional FDPs. Two materials and two techniques were used to fabricate a total of forty provisional FDPs: (1) BisA; (2) BisA reinforced with glass fiber strips [BisA-GFR]; (3) conventionally fabricated PMMA shell relined with PMMA [C-PMMA]; (4) CAD/CAM fabricated PMMA shell relined with PMMA [CAD/CAM-PMMA]. Provisional FDPs were then luted onto the preparations using a temporary cement. Specimens were mounted onto a chewing simulator; 20,000 cycles of 70 N forces were applied under 25°C distilled water. Specimens were then loaded to fracture using a universal testing machine (The Dillion Quantrol TC2i; Mecmesin) with a crosshead speed of 2 mm/min. One-way ANOVA, followed by Tukey post hoc test, was used to assess the effect of production technique on the fracture strength of the provisional FPDs (α = 0.5)., Results:  Mean fracture strengths recorded for the CAD/CAM-PMMA, C-PMMA, BisA, and BisA-GFR groups were 520 N, 448 N, 245 N, and 169 N, respectively. PMMA groups had significantly (p < 0.0001; F = 24.40) higher fracture strength compared to Bisacryl groups., Conclusion:  When high occlusal forces are expected, provisional FDPs fabricated with PMMA using the indirect-direct technique are recommended, irrespective of CAD/CAM or conventional workflow., (© 2021 by the American College of Prosthodontists.)

Purpose: The objective of this study was to assess the quality of posterior teeth prepared for monolithic zirconia crowns., Materials and Methods: A total of 392 STL-files of posterior preparations for monolithic zirconia crowns were evaluated in this study. Three-dimensional (3D) images were evaluated using a software (3D Viewer; 3Shape A/S, Copenhagen, Denmark) for finish line design, finish line width, occluso-cervical dimension, total occlusal convergence (TOC), intercuspal angulation, finish line quality, line angle form, and presence or absence of undercut at the axial wall and unsupported lip of enamel. The assessment was performed by two calibrated evaluators. Then, data were descriptively analyzed. Data for occluso-cervical dimension and TOC were descriptively analyzed according to their location., Results: Thirty-nine percent of premolars, 77% of first molars, and 91% of second molars had an average occluso-cervical dimension of less than 3 mm (premolars) and 4 mm (molars), with most of the preparations having a TOC of more than 20 degrees. More than 50% of preparations had undercut, unsupported enamel and/or unacceptable finish line quality., Conclusions: The quality of tooth preparation including finish line quality, absence of unsupported enamel and undercut at the axial wall should be evaluated when preparing monolithic zirconia crowns.

Purpose: The purpose of the study was to assess participants' and presenters' perceptions of a live web-based lecture series in comparison to traditional in-person lectures., Materials and Methods: A virtual lecture series was organized by the---from March 25th until June 3rd of 2020. Twenty-five postgraduate prosthodontics programs and 81 presenters participated. Two surveys were developed and distributed to the audience (N = 330) and the presenters (N = 81). Follow-up emails were sent one week, three weeks, and four weeks after the initial email survey to encourage its completion. The data were analyzed descriptively. One-way ANOVA (p = 0.05), followed by a post hoc test, were used to compare the response percentages among the different generations of presenters and participants., Results: Fifty-two percent of participants, and 65% of presenters, completed the survey. More than 96% of participants and presenters were satisfied with the lecture series. Seventy-nine percent of audience members felt that the live web-based lectures were as effective as traditional classroom lectures, or more effective; 32% of presenters agreed. Millennial audience members had significantly (p = 0.0028) more negative responses than the other generations., Conclusion: Participants have more positive perceptions of web-based lectures than presenters., (© 2020 by the American College of Prosthodontists.)

The purpose of this study was to compare biofilm formation on materials used for the fabrication of implant-supported dental prostheses. Twenty discs (D=15 mm, H=3 mm) were fabricated from one of the following restorative materials: yttria tetragonal zirconia polycrystal (Y-TZP); commercially pure titanium (CP-Ti); or heat-cured polymethyl methacrylate (PMMA). Specimens were polished following standard protocols. A non-contact profilometer (NPFLEX, Bruker, UK) was used to assess the surface roughness of each disk; results were reported as Ra (µm). Five strains of Gram-negative bacteria frequently associated with peri-implantitis, Aggregatibacter actinomycetemcomitans, Candida. albicans, Porphyromonas gingivalis, Prevotella intermedia, and Tannerella forsythia, were cultured on hand-polished discs fabricated from heat-cured PMMA, Y-TZP, or CP-Ti to compare biofilm formation on each type of material. The results were reported as colony-forming units per milliliter (CFU/mL). One-way ANOVA and post hoc tests were used to compare surface roughness and bacterial colonization on the respective materials. Statistical significance was set at a = 0.05. Discs fabricated from Y-TZP had a significantly higher Ra value (350 ± 30 µm) than either PMMA, or CP-Ti discs. Discs fabricated from either Y-TZP and CP-Ti may exhibit less colonization by bacteria associated with peri-mucositis and peri-implantitis. Y-TZP and CP-Ti are suggested materials for fabrication of implant-supported prostheses, considering biofilm formation.

Purpose: Modification of intercuspal angulation (ICA) influences the amount of tooth structure removal, which may impact the retention and resistance form of the preparation. This study evaluated the impact of ICA on the marginal gap of CAD/CAM crowns and the influence that tooth structure removal, caused by variation of ICA, has on the resistance and retention form of the preparation., Materials and Methods: Sixty ivorine molars were manufactured with various ICAs (100°, 110°, 120°, 140°, 160°, and 180°; 10 per group). The preparations were digitized using an intraoral scanner, and the crowns were designed using a design software. The designed crowns were then manufactured from lithium disilicate using a 3-axis milling machine, with the "detailed mode" selected for the manufacturing. The marginal gap of each crown was evaluated using a stereomicroscope at 20× magnification. Then, the marginal integrity and the resistance form of the preparation were assessed by tactile-visual evaluation, and they were given a categorical score. Crowns were then secured on their associated preparations using a temporary luting agent, and retention force was measured on a universal testing machine under tension with a 0.5 mm/min crosshead speed. Wilcoxon test followed by post-hoc tests (α = 0.05) were used to evaluate the impact of the ICA on the marginal gap and the retention form of the preparation. Fisher's exact test followed by post-hoc tests (α = 0.05) were used to assess the impact of the occlusal preparation design on the marginal integrity and the resistance form of the preparation., Results: The marginal gap was significantly larger for ICA-180 preparations (72 μm), compared to the other groups (ICA-180 vs ICA-100, ICA-110, ICA-120, and ICA-160 p = 0.0001; ICA-180 vs. ICA-140 p = 0.0017). None of the crowns for ICA-180 preparations had clinically acceptable resistance form. Preparations with ICAs of 100°, 110°, and 120° had a significantly higher value of retention than the other groups (ICA-100 vs. ICA-120 p = 0.0119; ICA-100 vs. ICA-140, ICA-160, and ICA-180 p < 0.0001; ICA-110 vs. ICA-140, ICA-160, and ICA-180 p = 0.0001; ICA-120 vs. ICA-180 p = 0.0017)., Conclusions: Crowns fabricated for preparations with various ICAs had clinically acceptable marginal adaptation. Variation in ICA impacts the loss of tooth structure. This loss of tooth structure may influence the resistance and retention form of the preparation., (© 2019 by the American College of Prosthodontists.)

The aim of this study was to evaluate teeth prepared for computer-aided design/computer-aided manufacturing (CAD/CAM) restorations by senior dental students using recently developed rubrics. The rubrics used evaluation criteria based on four factors: retention or resistance form; marginal or internal adaption or manufacturing process; biology, esthetics, or durability of restorative material; and intraoral scanner impression. In academic year 2018-19, four faculty members used the rubrics to assess 111 first maxillary right premolars (tooth no. 4) prepared for lithium disilicate crowns and 223 second maxillary right premolars (tooth no. 5) and first maxillary right molars (tooth no. 3) prepared for monolithic zirconia partial fixed dental prostheses. The preparations had been performed on typodont teeth. The most common errors identified for tooth preparations were in the finish line quality (136 errors in 223 prostheses), a criterion that is crucial for quality CAD/CAM restorations. To prevent poorly fit CAD/CAM restoration preparations that result from an unacceptable finish line quality, students need to understand the rationale used to develop detailed rubrics and adhere to the defined critera., (© 2019 American Dental Education Association.)

Statement of Problem: Comparative assessment of the effectiveness of computer-aided design and computer-aided manufacturing (CAD-CAM) technologies used to fabricate complete-coverage restorations is needed. A quantitative assessment requires precise documentation of the marginal adaptation and external surface contour of fabricated restorations. Limited information is currently available regarding the effects of milling mode on marginal adaptation and reproduction of the external surface contour for CAD-CAM-fabricated restorations., Purpose: The purpose of this in vitro study was to evaluate the outcomes for 3 different digital workflows on the marginal gap and the external surface contour reproducibility of CAD-CAM-fabricated lithium disilicate complete-coverage restorations., Material and Methods: Twelve Ivorine molars were prepared to receive lithium disilicate crowns. The preparations were digitally recorded using 2 intraoral scanners (TRIOS 3; 3Shape A/S and Planmeca PlanScan; E4D Technologies), and the restorations were designed using their associated design software with reference to the anatomy of an unprepared tooth. The designed restorations were then manufactured from lithium disilicate blocks using a 3-axis milling machine. Twelve restorations were manufactured using the detailed mode (Planmeca PlanScan detailed mode [PPD-D]), and 12 using the standard mode for the Planmeca system (Planmeca PlanScan standard mode [PPD-S]). Restorations from the 3Shape system were fabricated using the detailed mode (TRIOS 3Shape detailed mode [T3S-D]). The restorations were secured on their associated preparation with an elastomeric material. The marginal gap of each restoration was then measured in the ImageJ software using images captured by a stereo microscope at ×20 magnification. External surface reproducibility was evaluated by measuring undercut at 4-line angles using a dental surveyor. Differences in the marginal gaps of restorations fabricated using the 3 different workflows were compared by Brown-Forsythe robust ANOVA, followed by a post hoc test (α=.05). Chi-square analysis (α=.05) was used to evaluate differences in the contours of the external surface of the restorations, resistance form, and marginal integrity produced using the 3 workflows., Results: The mean marginal gap for restorations fabricated using the T3S-D workflow was 60 μm, a distance significantly lower (P<.05) than that of PPD-D and PPD-S workflows, which yielded a marginal gap of 95 μm for the detailed mode and 124 μm for the standard mode of milling. Restorations fabricated using PPD-D and PPD-S workflows produced a significantly more reproducible external surface contour than those fabricated using the T3S-D workflow., Conclusions: Restorations fabricated using the T3S-D workflow produced the smallest marginal gap. However, reproducibility of the external surface contour for this workflow was the worst of the three workflows analyzed., (Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the impact of fabrication technique on the marginal fit and resistance of lithium disilicate crowns., Materials and Methods: Twelve ivorine molars were prepared to receive lithium disilicate crowns. The preparations were digitally recorded using an intraoral scanner, and the crowns were designed following the anatomy of an unprepared tooth using a design software. The designed crowns were fabricated using 3 techniques: (1) milling from lithium disilicate blocks using a 3-axis milling machine (3XM), (2) milling from lithium disilicate blocks using a 5-axis milling machine (5XM), and (3) milling from resin-wax billet using a 5-axis milling machine, followed by heat-pressing the pattern into lithium disilicate (5XWP). For the control group, the wax patterns were fabricated by one lab technician, and the crowns were fabricated by heat-pressing the pattern into lithium disilicate (CWP). After sintering, the crowns were secured on their associated preparations using an elastomeric material. The marginal gap of each crown was then measured at 14 defined locations through analyses of 20× images captured with a stereomicroscope. The marginal integrity and resistance to rotation of each crown were assessed by 2 calibrated practitioners. Differences in outcomes by fabrication technique were assessed using Wilcoxon, Kruskal Wallis, and Fisher's exact tests, as appropriate (α = 0.05)., Results: Crowns fabricated using digital workflows (3XM, 5XM, 5XWP) had significantly smaller mean marginal gaps compared to the CWP group (p = 0.0001, p = 0.0002, p = 0.0001, respectively); however, 3XM group was the only group to exhibit significantly better marginal integrity than the CWP group (p = 0.0004). No significant difference (p = 0.6004) in the resistance to rotation of crowns was observed between groups., Conclusions: Choice of fabrication technique and instrument may impact the marginal discrepancy of lithium disilicate crowns; however, all fabrication techniques analyzed produced crowns with acceptable marginal discrepancies., (© 2019 by the American College of Prosthodontists.)

The aim of this study was to evaluate the impact of a contemporary preclinical technique skills course on early dental student performance in a preclinical operative course. Ivorine teeth prepared for Class I resin restorations by the Classes of 2020 and 2021 in one U.S. dental school were evaluated in this study (N=184). Ivorine teeth were prepared during the first practical exam of the operative dentistry course. Students in the Class of 2021 had been enrolled in a contemporary technique skills course a semester prior to the operative dentistry course, while students in the Class of 2020 were not. The preparations were randomly evaluated by three calibrated and blinded faculty members using magnification loupes, an explorer, and a periodontal probe to evaluate external outline form, internal form, depth, and margin following an established rubric. The results showed that students in the Class of 2021 (who had taken the technique skills course) performed significantly better than students in the Class of 2020 for all criteria evaluated (p<0.05). In this study, incorporation of the preclinical technique skills course improved student performance in the subsequent operative dentistry course.

The aim of this retrospective study was to assess agreement between faculty and virtual assessment software in depth evaluation of rounded rectangular preparations in non-anatomical teeth prepared by second-year dental students. A total of 184 non-anatomical ivorine mandibular first molars prepared by second-year students were retrospectively evaluated in 2018. Each tooth was prepared to a depth of 1.5 mm within a laser-marked outline using a 330 bur, as detailed in the technique skills course syllabus. Preparations were recorded using an intraoral scanner. Then, virtual assessment software was used to superimpose a three-dimensional (3D) image of each preparation on a 3D image of a standard preparation produced by a faculty member. The software was used to calculate percentage comparison (%Comparison) values at 200 μm tolerance. Values of %Comparison ≥72% were considered satisfactory. In addition, each preparation depth was evaluated by two calibrated faculty members using a periodontal probe and a 330 bur. The preparation depth was considered satisfactory when more than 50% of the tooth preparation had a depth of 1.5 mm. The results showed almost perfect agreement (0.81 < kappa < 0.99) between faculty assessment and %Comparison value. The findings suggest that %Comparison values may be used to assess the tooth preparation depth of rounded rectangular preparations in non-anatomical teeth when prepared in a laser-marked outline.

The aim of this study was to evaluate the effects of dental faculty-student interactions, virtual assessment software, and associated rubrics on student performance by assessing tooth preparations generated during the students' final practical exam. The study, conducted in 2017 and 2018, compared teeth prepared for preclinical fixed prosthodontics competency exams by two subsequent classes of second-year dental students trained using different methods. Class A was trained for nine months prior to the exam using feedback via student-faculty interactions and conventional rubrics. Class B was trained for five and half months prior to the exam via contemporary rubrics that incorporated feedback from both faculty and virtual assessment software. Two blinded, independent, and calibrated faculty members randomly evaluated the tooth preparations and graded them as excellent, standard, or standard not met for occlusal reduction, axial/lingual reduction, contour/long axis/axial wall height, finish line location, finish line quality, and finish of the preparation. The interrater agreement was slight to fair (0.01 < Kappa < 0.4) for evaluation of preparations. The teaching method did not have a significant impact (p>0.05) on student performance for the assessed criteria. These results suggest that, with the use of virtual assessment software, a course director may be able to shorten a course and obtain the same results as a nine-month course.

This report describes the complete mouth rehabilitation of worn dentition by using a digital workflow on a non-hinge simulated patient. A dentiform was used to simulate a patient with loss of occlusal vertical dimension. Physical diagnostic waxing along with a digital workflow was then used to re-establish the occlusal vertical dimension at the interim and definitive restoration stages., (Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

The purpose of this study was to determine the effectiveness of virtual assessment software as a means of immediate feedback for preclinical fixed prosthodontics course. The subjects of the study were second year dental students with no previous training in fixed prosthodontics. Nine students participated in the study. Participants completed 2 days of didactic training focused on the principles of tooth preparation and the use of intraoral scanners and virtual assessment software. Didactic training was followed by 12 sessions of practical exercises. Students were randomly assigned to one of three groups for training in the preparation of tooth no. 46 for a complete cast crown. Students received feedback from (a) faculty interaction only; (b) interactions with both faculty and virtual assessment software; or (c) interactions with only virtual assessment software. During Sessions 5, 10, and 12, students prepared tooth no. 46 for complete cast crown independently and without any immediate feedback to simulate a practical exam. Prepared teeth were collected at Sessions 5, 10, and 12, and two blinded faculty members assessed the teeth following an established rubric. Results from Session 12 showed that preparations that one of three students and two of three students respectively for student-faculty interaction and student-faculty-Compare software interaction groups did not meet acceptable standards. However, the students in student-Compare software interaction group generated acceptable preparations at week 12. These data suggest that immediate feedback via virtual assessment software may be as effective as one-on-one faculty instruction for dental students in fixed prosthodontics.

Statement of Problem: Different techniques are used to fabricate complete coverage restorations. Each fabrication technique requires a specific preparation design that may violate a principle of tooth preparation, that is, conservation of tooth structure., Purpose: The purpose of this in vitro study was to compare the volume of loss of mandibular first molar structure associated with a preparation for computer-aided design and computer-aided manufacturing (CAD-CAM) versus conventionally fabricated complete coverage restorations., Materials and Methods: Fifty artificial mandibular right first molars were weighed before and after preparation for complete coverage restorations of the following types: complete cast, monolithic zirconia, monolithic pressed lithium disilicate, monolithic milled lithium disilicate, and metal-ceramic crowns (n=10 per method). Tooth mass loss was measured by subtracting the mass after preparation from the mass before the preparation, and tooth volume loss was calculated by dividing the mass by the density of the material. A robust analysis of variance (ANOVA), followed by a post hoc test, was used to compare the volume of tooth loss (α=.01)., Results: Mean tooth volume losses were 255.6 mm 3 , 270.0 mm 3 , 312.7 mm 3 , 331.7 mm 3 , and 309.9 mm 3 for complete cast, monolithic zirconia, monolithic pressed lithium disilicate, monolithic milled lithium disilicate, and metal-ceramic crowns, respectively. Teeth prepared for monolithic CAD-CAM zirconia and lithium disilicate crowns did not exhibit a significantly lower (P>.01) decrease in volume loss than with complete cast and monolithic pressed lithium crowns., Conclusions: Preparation of teeth for monolithic CAD-CAM complete coverage restorations is not associated with a significantly higher volume of tooth loss than their conventionally fabricated counterpart preparations., (Copyright © 2018 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

The aims of this study were 1) to determine whether the Compare software Comparison% score provided appropriate feedback for preparation depth on a non-anatomical tooth and 2) to define an acceptable tolerance for use in calculating the Comparison% for virtual assessment of cavity depth on a non-anatomical mandibular first molar. Forty-six non-anatomical ivorine teeth with laser-marked outlines on their occlusal surfaces were used for this study. One tooth was prepared at a 1.5 mm depth, approved by participating faculty at a U.S. dental school, and served as the standard preparation. The remaining teeth were divided into three groups (n=15 per group) for cavity preparation depths of 1 mm, 1.5 mm, and 2 mm in the laser-engraved external outline. Teeth were prepared using an electric handpiece with a 330 bur and a hatchet. Virtual images of the standard and experimental tooth preparations were recorded using an intraoral scanner. Virtual comparison software was then used to superimpose a three-dimensional (3D) image of each experimental preparation on the 3D image of the standard preparation. The software calculated comparison surface percentage values (Comparison%) at a 100 and 200 micron tolerance for each specimen. Two-way mixed linear models (α=0.01) were adopted to compare outcomes for the two levels of tolerance for teeth with different depths of preparation. Using a tolerance level of 200 μm, Comparison% scores for the acceptable preparation depth of 1.5 mm were found to be significantly different (p<0.01) from those of the unacceptable 1 mm and 2 mm depth preparations. These findings suggest that virtual comparison software may be used to assess an acceptable depth for cavity preparation within a defined external outline.

The purpose of this study was to evaluate interrater agreement between faculty and virtual assessments of preparations for complete coverage restorations in preclinical fixed prosthodontics. Teeth prepared during preclinical fixed prosthodontics practical exams at the University at Buffalo School of Dental Medicine were used in this study. Teeth were prepared for fabrication of complete cast, metal ceramic, and all ceramic crowns. The specimens were digitized using an intraoral scanner. Then, they were virtually superimposed on the corresponding standard preparations using Compare software. The software was used to quantify comparison percentages, average finish line widths, and average axial wall heights. Two calibrated faculty members assessed preparations for occlusal/incisal reduction, finish line location, axial wall height, and finish line width using traditional assessment forms. Cohen's kappa coefficient was used to measure interrater agreement between faculty and virtual assessments. Kappa interrater agreement scores ranged between 0.83 and 0.88 for virtually assessed comparison percentages and sums of faculty-assessed occlusal/incisal reduction and finish line location. Kappa interrater agreement score ranges were 0.64-0.94 and 0.74-0.89 for comparisons of virtual and faculty assessments for axial wall height and finish line width, respectively. Virtual assessments are similar to faculty assessments for occlusal/incisal reduction, finish line location, axial wall height, and finish line width in fixed prosthodontics and can be used as equivalent evaluations of student performance for these criteria.

The purpose of this study was to develop an assessment strategy for preclinical foxed prosthodontics using a virtual assessment software. This descriptive study examined 80 collected ivory teeth from previous classes prepared during preclinical fixed prosthodontics course. Ivory teeth prepared for the complete cast (tooth no. 46), metal ceramic (teeth nos 24 and 46), and all ceramic (tooth no. 21) crowns were scanned and superimposed with their respective standard preparations. Differences between these teeth and standard teeth prepared by faculty were computed using Compare software to generate comparison percentages. In addition, average finish line width, average total occlusal convergence, average axial wall height, and undercut presence/absence were quantified for student preparations using the software. Software-generated values were then descriptively compared with faculty assessments. Comparison percentages aligned with faculty assessments for the amount of occlusal/incisal reduction and finish line location. The average axial wall height and finish line width calculated by Compare software were grouped based on their respective faculty assessment criteria. Software-generated comparison percentages may be used to assess the amount of occlusal/incisal reduction and finish line location in student preparations. Additionally, averages extracted from Compare software could be used to assess student performance for axial wall height and finish line width.

This report describes the prosthetic management of a fractured Dolder bar on a transmandibular implant system. The patient declined surgical removal of the implants. Therefore, to repair the superstructure, a cast Dolder bar was fabricated and luted onto the existing transmandibular implants. An implant-retained bar overdenture was then fabricated to rehabilitate the mandibular arch., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Although osseointegrated dental implants have become a predictable and effective modality for the treatment of single or multiple missing teeth, their use is associated with clinical complications. Such complications can be biologic, technical, mechanical, or esthetic and may compromise implant outcomes to various degrees. This article presents prosthetic complications accompanied with implant-supported single and partial fixed dental prostheses., (Published by Elsevier Inc.)

Statement of Problem: Information about the influence of zirconia crown surface treatment and cement type on the retention of zirconia crowns is limited. It is unclear whether zirconia crowns require surface treatment to enhance their retention., Purpose: The purpose of this in vitro study was to evaluate the effect of surface treatment on the retention of zirconia crowns cemented with 3 different adhesive resin cements after artificial aging., Material and Methods: Ninety extracted human molars were prepared for ceramic crowns (approximately 20-degree taper, approximately 4-mm axial length) and were divided into 3 groups (n=30). Computer-aided design and computer-aided manufacturing zirconia copings were fabricated. Three surface treatments were applied to the intaglio surface of the copings. The control group received no treatment, the second group was airborne-particle abraded with 50 μm Al2O3, and the third group was treated with 30 μm silica-modified Al2O3, The copings were luted with a self-etch (RelyX Unicem 2), a total-etch (Duo-Link), or a self-etch primer (Panavia F 2.0) adhesive cement. They were stored for 24 hours at 37°C before being artificially aged with 5000 (5°C-55°C) thermal cycles and 100,000 cycles of 70 N dynamic loading. Retention was measured on a universal testing machine under tension, with a crosshead speed of 0.5 mm/min. Statistical analysis was performed with 1-way and 2-way ANOVA., Results: Mean retention values ranged from 0.72 to 3.7 MPa. Surface treatment increased crown retention, but the difference was not statistically significant (P>.05), except for the Duo-Link cement group (P<.05). Analysis of the adhesives revealed that the Duo-Link cement resulted in significantly lower crown retention (P<.05) than the other 2 cements., Conclusion: For zirconia crowns, retention seems to be dependent on cement type rather than surface treatment., (Copyright © 2014 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

An implant-supported prosthesis is a successful treatment option for edentulous patients. This article reports on a case that has not been documented in the literature involving complications in a maxillary implant-supported bar overdenture, followed by the management of the complications.

This article introduces a procedure that allows the clinician to verify the 3-dimensional spatial orientations of implant analogs in the definitive cast for a cement-retained, implant-supported prosthesis with engaging abutments. Multiple interlocking puzzle pieces are used with engaging interim abutments to verify the accuracy of the impression., (Copyright © 2013 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)