PURPOSE: . The purpose of this in vitro study was to evaluate how variations in scan body geometry, specifically body height and the length of the flat indexing surface (FIS), affect linear and angular accuracy when combined with truncated or full-geometry library files. MATERIALS AND METHODS: . Nine scan body geometries were fabricated by combining three body heights (4, 5, and 6 mm) with three FIS lengths (1, 2, and 3 mm). Digital impressions were superimposed onto truncated or full-geometry library files. Linear deviation (ΔD) and angular deviation (ΔA) were calculated by comparing aligned scan bodies with coordinate measuring machine references. Linear and angular deviations were compared between library types using the Mann–Whitney U test, and differences among body heights and FIS lengths were evaluated using the Kruskal–Wallis test with Dunn’s post-hoc test (α = .05). RESULTS: . Linear deviation remained within a comparable range, and most geometry–library comparisons did not show a significant difference from body height, FIS length, or library morphology (P > .05). Angular deviation demonstrated geometry-dependent behavior, increasing only in the 4-mm body paired with larger FIS lengths, particularly when fullgeometry libraries were used. No significant angular differences were observed in the 5-mm or 6-mm body groups. CONCLUSION . Digital implant registration remained stable across most configurations. Shortened scan bodies performed reliably when FIS dimensions were preserved. Angular accuracy was more sensitive to geometry-library interactions, with truncated libraries improving stability.

PURPOSE: . The purpose of this study was to evaluate the interrelationships among the determinants of Hanau’s Quint — condylar guidance, occlusal plane, compensating curve, incisal guidance, and cusp height — according to the laws of articulation, using a novel digital method. MATERIALS AND METHODS: . Fully edentulous casts with 9 sets of occlusion rims (7, 8, and 9 inches curvature; standard, +5°, and -5° inclination) were mounted on a semiadjustable articulator to simulate analog experimental conditions (AECs).The same settings were reproduced in a 2-dimensional virtual articulator in a lateral view (Adobe Photoshop), with the addition of cusp height as a variable, to generate digital experimental conditions (DECs). Whenever an increase in one determinant produced occlusal disharmony, other factors were modified until bilateral balanced occlusion (BBO) was reestablished. The results were compared with Hanau’s predicted interactions. RESULTS: . Both analog and digital methods demonstrated consistent interrelationships among the occlusal plane, compensating curve, condylar guidance, and incisal guidance, as described in Hanau’s Quint. Cusp height, tested digitally, showed a predictable compensatory role. CONCLUSION . The interrelationships among the determinants of Hanau’s Quint in achieving BBO were validated digitally using a simple and reproducible digital methodology confirmed by an analog articulator. This study may help clinicians better understand BBO and Hanau’s principles in complete denture treatment planning.

PURPOSE: . This study aimed to evaluate the influence of implant placement depth on the accuracy of five full-arch digital impression techniques: 2 photogrammetry systems (Imetric [PGI] and Oxo Core [PGO]) and 3 intraoral scanning (IOS) routes (standard IOS, IOS with crown-shaped [IOS+C], and IOS with laterally-extending [IOS+LE] scanning aids). MATERIALS AND METHODS: . Three master models including 5 implants with 2-, 4-, and 6-mm subgingival implant depths were fabricated. Implant positions were recorded using each of the 5 techniques (n = 15). The resultant scans were compared to reference data generated by a laboratory scanner. Deviations were 3-dimensionally assessed using root mean square values to quantify both trueness and precision. Angular deviations (AD) were calculated to provide a detailed assessment of spatial inconsistencies. Data were statistically analyzed (α = 0.05). RESULTS: . Implant depth and impression technique, as well as their interaction, significantly affected trueness, precision, and angular deviation values (P < .001). PGI demonstrated the highest accuracy, with the lowest mean AD values across all implant positions (0.24 – 0.32°) and the highest trueness (26.57 μm) and precision (7.72 μm). IOS exhibited the largest distortions, with AD values up to 1.77° and trueness values of 74.84 μm. Precision of both photogrammetry systems were not influenced by implant depth. CONCLUSION . Implant depth significantly impacts the accuracy metrics of full-arch digital impressions. The Imetric system outperformed the other groups. Since laterally-extending scanning aids effectively improved accuracy, it may be recommended as a clinically viable alternative to standard IOS.

PURPOSE: . This study evaluated the fracture resistance of premolar screwretained implant-supported hybrid abutment crowns (HACs) fabricated from different monolithic restorative materials following artificial aging. MATERIALS AND METHODS: . Forty-four titanium implant analogs were restored with HACs fabricated from four materials: 5 mol% yttria-partially stabilized monolithic zirconia (ST), strength-gradient multilayered zirconia (YM), lithium disilicate ceramic (LD), and resin composite containing dispersed nanoparticles (CM) (n = 11 per group). All specimens were subjected to thermocycling (10,000 cycles) and mechanical loading (1.2 million cycles) to simulate 5 years of clinical service.Fracture resistance was evaluated under compressive loading, and failure modes were analyzed using optical microscopy and scanning electron microscopy.Statistical analysis was performed using the Kruskal-Wallis and Steel-Dwass tests (α = 0.05). RESULTS: . Significant differences were found among all groups (P = 0.00033-0.0022). The YM group exhibited the highest median fracture resistance (2.06 kN, IQR: 2.00 – 2.60 kN), followed by ST (1.74 kN, IQR: 1.69 – 1.80 kN), LD (1.29 kN, IQR: 1.14 – 1.41 kN), and CM (0.87 kN, IQR: 0.79 – 0.92 kN). All specimens survived the artificial aging protocols. Distinct fracture patterns were observed depending on the restorative material, with zirconia-based groups showing more favorable resistance than resin composite. CONCLUSION . All tested HACs exhibited fracture resistance values exceeding maximum bite forces, supporting their clinical applicability. Strength-gradient multilayered zirconia demonstrated superior reliability after simulated 5-year aging, emphasizing its structural advantage and broader safety margin compared with other restorative materials.

PURPOSE: . This study aimed to compare the wear depth and volume loss of 3D-printed resin denture teeth with prefabricated and milled acrylic denture teeth under chewing simulation. MATERIALS AND METHODS: . Four groups of denture teeth (n = 9) were evaluated: prefabricated acrylic teeth (PT), milled acrylic teeth (MT), 3D-printed methacrylate-based resin teeth (3DT), and glazed 3D-printed resin teeth (3DT+G). Samples were embedded in self-curing resin, and antagonists were fabricated from the same materials. A chewing simulator was utilized to apply a cyclic occlusal load of 49.05 N (5 kg) for 120,000 cycles in distilled water. Wear depth (μm) and volume loss (mm3 ) were measured using a 3D laser profilometer. Surface morphology was qualitatively analyzed via scanning electron microscopy (SEM). Data normality was verified, and statistical significance was determined using one-way ANOVA followed by Tukey’s HSD test (α=0.05). RESULTS: . Significant differences in wear depth and volume loss were observed among the groups (P < .05). No significant differences were found between PT and MT, or between 3DT and 3DT+G. However, the 3DT and 3DT+G groups exhibited significantly lower wear depth and volume loss compared to the PT and MT groups (P < .05). SEM analysis revealed that the PT group displayed a more uniform and homogenous surface morphology compared to the other groups, while 3DT+G showed evidence of glaze depletion within the wear facets. CONCLUSION . 3D-printed resin denture teeth demonstrated superior wear resistance compared to prefabricated and milled alternatives under simulated chewing conditions. Furthermore, the application of a 50 µm surface glaze did not significantly enhance wear resistance of the 3D-printed resin.

PURPOSE: . This study aims to evaluate how the fit between implant-abutment connection surfaces and the proximal contact tightness of crowns affect abutment screw loosening. MATERIALS AND METHODS: . Forty implants with internal hex connections were placed in stainless steel models in the maxillary right first molar region. Monolithic zirconia crowns with standard and 15 µm reduced proximal contacts were used with abutments with standard and 25µm horizontally reduced hex connections. After cementation, four groups of specimens—standard abutment/standard proximal contact (control), reduced fit abutment/standard proximal contact (RS), standard abutment/reduced proximal contact (SR), and reduced fit abutment/reduced proximal contact (RR)—were subjected to simultaneous thermocycling (± 5 ‒ 55°C) and chewing cycles (100N, 1.6 Hz, 40 mm/sec lateral and vertical speed, lateral movement: 6 mm, vertical movement: 0.5 mm). Removal torque values (RTVs) were measured using a digital torque meter. Data were analyzed using two-way ANOVA and the Bonferroni test (α = .05). RESULTS: . All groups exhibited statistically significant differences compared to each other and the control group (P < .05). The RR group had the lowest removal torque values (RTVs) (21.70 ± 0.99 N·cm), while the control group had the highest (26.82 ± 0.70 N·cm). The RS group (24.78 ± 0.89 N·cm) had lower RTVs than the SR group (25.51 ± 0.52 N·cm). CONCLUSION . The findings indicate that inadequate proximal contacts and horizontal misfit of the implant-abutment connection may lead to torque loss and screw loosening.

PURPOSE: The location of the edentulous area in the dental arch can influence the design of the bridge prosthesis in the surrounding region and the forces it will encounter. This study assessed the fracture strength of restorations with various geometric designs produced using different additive and subtractive manufacturing methods. MATERIALS AND METHODS: Co-Cr metal and zirconia fixed partial denture (FPD) frameworks were designed in both linear and curved geometries. The Co-Cr metal frameworks were produced through casting (C) and laser sintering (L), while the zirconia (Z) frameworks were obtained through milling (n = 10). After veneering the frameworks, a four-point bending test was conducted on the specimens to assess their fracture strength. All obtained values were statistically analyzed (P < .05). RESULTS: In both linear and curved groups, Z group showed the lowest fracture resistance values followed by C and L groups and the differences between the groups were found statistically significant (P < .05). In L group, curved FPDs showed statistically significantly higher fracture resistance values than linear FPDs (P < .05). In both Z and C groups, curved FPDs showed statistically significantly lower fracture resistance values than linear FPDs (P < .05). CONCLUSION The geometric configuration of the restoration and manufacturing technique affects the fracture resistance of different framework materials in FPDs.

PURPOSE: This study aimed to analyze the relationship between self-perceived dental esthetics and the selected esthetic mathematical proportions. MATERIALS AND METHODS: Descriptive cross-sectional study was conducted among 48 dental students who fit into the inclusion criteria. The subjects rated their self-perceived dental esthetics based on the given Likert scale. Standardized portrait photographs of each subject were taken and the mesiodistal measurements of the maxillary anterior teeth were measured using a graphic editing software. The golden proportion, golden percentage and RED proportion in maxillary anterior teeth were then calculated. RESULTS: Most subjects were pleased with the size, form, and color of their maxillary anterior teeth. Only 2.1% of the maxillary canines and 10.4% of the left maxillary lateral incisors complied with the golden proportion. The maxillary lateral incisors demonstrated its occurrence to golden percentage. For the RED proportion, 29.2% of the left maxillary teeth and 16.7% of the contralateral teeth complied with the proportion. Self-perceived dental esthetics and the occurrence these mathematical proportions have no association. CONCLUSION Within the limitations of the study, it can be concluded that most subjects were satisfied with their self-perceived dental esthetics. Only a small percentage of the subjects having their natural dentition coincide with the golden proportion, golden percentage and RED proportion with a higher percentage occurring on the RED proportion. Hence, the mathematical proportions do not represent the naturally occurring dentition. These mathematical proportions can serve as a guide and the perceived teeth width can be customized accordingly.

PURPOSE: Digitalization in dentistry has increased interest in the use of intraoral scanners (IOs) in clinical practice. However, knowledge of implant digitalization is primarily limited to in vitro studies. This study aimed to compare implant-supported fixed dental prostheses (FDP) fabricated following complete digital workflow using various implant scan bodies (SB) in treatment of short-span partial edentulism. MATERIALS AND METHODS: Patients with 25 short-span posterior edentulous sites, each receiving two implants to support a fixed restoration, were included. Digital implant records were made consecutively with original, non-original, and generic SBs using IOs. A practitioner implemented a two-stage full-arch scanning protocol, beginning with continuous arch scanning, followed by individual scanning of SBs. For clinical evaluation, each site received screw-retained full-contour restorations to qualify the connection fit to the implants and contacts to the adjacent and antagonist teeth. For analytical comparison, implant axes calculated from SB scans were quantified using reverse engineering software to compare the differences three-dimensionally. Restorative outcomes and implant axes records were statistically analyzed using the chi-square test and generalized estimating equations, respectively. RESULTS: Clinical delivery conditions did not differ significantly among the three intraoral SBs (P > .05). The analytical implant-position calculations for non-original and generic SBs did not present significant differences compared to original SBs (P > .05). CONCLUSION SBs with different hardware and software characteristics for an implant system are clinically acceptable for fabricating screw-retained short-span implant-supported FDPs using a complete digital workflow.