PurposeTo compare the marginal discrepancy between milled interim crowns fabricated using intraoral digital scans acquired at different scanning distances.Materials and methodsTen acrylic typodont teeth were prepared for interim crowns. Three different resin frames of 2.5‐, 5‐, and 7.5‐mm heights were fabricated and attached to an intraoral scanner (Omnicam). Three groups were created based on the different scanning distances tested: 2.5 mm (Group A), 5 mm (Group B), and 7.5 mm (Group C). Intraoral digital scans were performed on four tooth surfaces: mesial, distal, buccal, and lingual (n = 10). Each experimental scan was used to design and fabricate a milled polymethylmethacrylate anatomically contoured crown. Vinyl polyether silicone was used three times to assess the marginal discrepancy of the specimens by measuring five marginal points on digital photographs. One‐way analysis of variance test was used to analyze the data, followed by Tukey's honestly significant difference test (α = 0.05).ResultsThe mean marginal discrepancy values in Group C were significantly higher than those in Groups A (p ≤ 0.000) and B (p = 0.001). There was no significant difference between Groups A and B (p = 0.702). There were no significant differences among the four surfaces in any of the scanning distance groups (p1 = 0.583, p2 = 0.390, and p3 = 0.135; p > 0.05).ConclusionsThe interim crowns fabricated with a scanning distance of 7.5 mm showed the greatest marginal discrepancy when compared with crowns fabricated using 2.5‐ and 5‐mm scanning distances.

Background Short-time sintering may offer advantages including saving time and energy but there is limited evidence on the effect that altering sintering time has on the accuracy of monolithic zirconia crowns. The purpose of this in vitro study was to investigate the effect of shortened sintering time on the marginal and internal fit of 3Y-TZP (three mol% yttria-stabilized tetragonal zirconia polycrystal) and 4Y-TZP (four mol% yttria-stabilized tetragonal zirconia polycrystal) monolithic crowns. Methods Sixty monolithic zirconia crowns were fabricated for the maxillary first molar tooth on the prefabricated implant abutment. Groups were created according to the material composition: 3Y-TZP Generation 1 (alumina wt; ≤0.5%, < 15% cubic phase), 3Y-TZP Generation 2 (alumina wt; ≤0.05%, < 15% cubic phase) and 4Y-TZP (alumina wt; ≤0.05%, > 25% cubic phase). Two different sintering protocols were performed: same final sintering temperature (1500°C) and various rates of heating (10°C/min and 40°C/min), cooling down speed (-10°C/min and − 40°C/min), holding time (45 and 120 minutes), and total sintering time (approximately 2 and 7 hours, respectively). The marginal and internal fit of the crowns were determined using the silicone replica technique. Comparisons between groups and sintering times were analyzed using two-way ANOVA. Pairwise multiple comparisons were performed using the t-test (p < 0.05). Results The mean marginal gap values of 4Y-TZP zirconia revealed statistically significant increase for the speed sintering protocol (p < 0.0001), while no difference was observed between the sintering protocols for the mean marginal gap values of 3Y-TZP groups. Conclusions Although all groups showed clinically acceptable gap values (<120 µm), altering the sintering time had an effect on the marginal fit of the crowns manufactured from 4Y-TZP zirconia. Shortening the sintering time may lead to differences within clinically acceptable limits. The manufacturer's recommendations according to material composition should be implemented with care.

Objectives: Although spectrophotometers are commonly used in shade analysis in dentistry; digital cameras, photographic lighting systems, computer programs and photographs have also become the part of this field. The aim of this study was to compare the success of spectrophotometer and calibrated digital photography on shade selection. Materials and Methods: 3D-Master toothguide (VITA) with 29 tabs was used for the analyses. L, a, b values were determined by a spectrophotometer (Minolta CM-2300D, Konica) and these values were matched with digital photographic measurements. Photographs were transferred to an image analyzing software (Adobe Photoshop CC). Results: There were significant differences between L* values of the spectrophotometric analyses and digital measurements in 3 different regions of the tab (p&lt;0.05). For the evaluation of ΔE values, Post hoc Bonferroni analysis which was performed between the 3 regions of shade tabs revealed significant difference between the middle (21.92 ± 2.31), incisal (13.67 ± 1.69) and cervical (19.57 ± 2.47) region of the tabs (p&lt;0.05). Conclusion: Spectrophotometer was found to be a more accurate shade determination technique compared to calibrated digital photography.

Background Short-term sintering may offer advantages including saving time and energy but there is limited evidence on the effect that altering sintering time has on the accuracy of monolithic zirconia crowns. The purpose of this in vitro study was to investigate the effect of shortened sintering time on the marginal and internal fit of 3Y-TZP and 4Y-TZP monolithic crowns. Methods Sixty monolithic zirconia crowns were fabricated for the maxillary first molar tooth on the prefabricated implant abutment. Groups were created according to the material composition: 3Y-TZP Generation 1, 3Y-TZP Generation 2 and 4Y-TZP. Two different sintering protocols were performed: same final sintering temperature (1500 °C) and various rates of heating (10 °C/min and 40 °C/min), cooling down speed (− 10 °C/min and − 40 °C/min), holding time (45 and 120 minutes), and total sintering time (approximately 2 and 7 hours, respectively). The marginal and internal fit of the crowns were determined using the silicone replica technique. Comparisons between groups were analyzed using two-way ANOVA. Pairwise multiple comparisons were performed using t-test (p < 0.05). Results The mean marginal gap values of 4Y-TZP zirconia revealed statistically significant increase for the short-term sintering protocol (p < 0.0001), while no difference was observed between the sintering protocols for the mean marginal gap values of 3Y-TZP groups. Although all groups showed clinically acceptable gap values, altering the sintering time had an effect on marginal fit of the crowns manufactured from 4Y-TZP zirconia. Conclusions Shortening the sintering time may lead to differences within clinically acceptable limits. The manufacturer’s recommendations according to material composition should be implemented with care.