Effect of magnifying loupes on tooth preparation of complete coverage crown: A quantitative assessment using a digital approach.

OBJECTIVE: The purpose of this study was to evaluate the use of magnifying loupes (×2.5) on the quality of tooth preparation for complete coverage crowns; performed by predoctoral students using an objective and quantitative digital method. MATERIALS AND METHODS: Forty-two predoctoral students were randomly assigned into 2 groups to perform tooth preparation for a complete coverage crown on a mandibular first molar in a manikin, with and without the use of magnifying loupes. All preparations were digitally evaluated by PrepCheck 3.0 (Dentsply Sirona). Parameters including tooth reduction, total occlusal convergence (TOC), undercut, margin quality and surface quality were assessed. Continuous data were analysed using Paired t-tests or Wilcoxon Signed Ranks tests. Ordinal data were analysed by McNemer's tests. To further detect the majority pattern ( > 50%) in each group (with and without loupes), one-sample t-test or one-sample Wilcoxon Signed Rank test was performed. The level of significance was set at p = .001 after Bonferroni adjustments for multiple testing. RESULTS: No significant differences in the measured outcomes were found between the groups with or without the use of magnifying loupes (p > .002). The majority (>50%) of both groups had no undercuts (99.3% and 99.4% both p < .001) and the preparation type was within tolerance (81.6% and 85.3%, both p < .001) with acceptable margin (86.4% and 86.3%, both p < .001) and acceptable surface quality (99.0% and 99.1%, both p < .001). However, the majority of both groups underprepared occlusally (96.0% and 95.4%, both p < .001) and axially (65.3% and 67%, both p < .001). Only 30.0%-42.1% of the participants achieved the TOC within 0-20°. CONCLUSIONS: Within the limitations of this study, the use of magnification loupes does not appear to significantly improve the quality of tooth preparation for complete coverage crown. The TOC was also found to be overprepared and occlusally underprepared.

Assessing Enamel Wear of Monolithic Ceramics With Micro-CT and Intra-oral Scanner.

OBJECTIVE: This in vitro study aimed to investigate enamel wear against 3 monolithic ceramics using 2 methods of measurement. METHODS: Three groups of standard flat monolithic ceramic specimens including zirconia-reinforced lithium silicate glass (Vita Suprinity, VITA Zahnfabrik), yttria-stabilised tetragonal zirconia (Lava Esthetic Zirconia), and lithium disilicate glass (IPS e.max Press, Ivoclar Vivadent) were prepared, with human enamel used as the control group. Each specimen was subjected to the 2-body wear test at 49 N for 250,000 cycles. Enamel antagonists were evaluated with micro-computed tomography (CT) and intra-oral scanner, allowing 3-dimensional images of vertical wear and volumetric loss of enamel antagonists to be calculated. One-way analysis of variance followed by Student-Newman-Keuls post hoc tests were used to examine the differences in vertical wear/volumetric loss amongst the groups. Paired t tests and intra-class correlations were used to compare vertical wear/volumetric loss between the micro-CT and intra-oral scanner groups. RESULTS: No significant difference in vertical wear was found amongst all groups. More volumetric loss was found in all test groups than in the control group (P < .001), but no significant difference was found amongst the test groups. There was a moderate positive correlation (r = 0.535, P = .033) between the vertical wear and volumetric loss. No significant difference between the 2 methods of measurement was found. CONCLUSIONS: Monolithic ceramics induce more enamel wear than natural teeth. Both micro-CT and intra-oral scanners can be used for measuring tooth wear with similar performance.

The Influence of Surface Roughening and Polishing on Microbial Biofilm Development on Different Ceramic Materials.

PURPOSE: To test the hypothesis that surface roughening and polishing of ceramics have no effect on their surface roughness and biofilm adhesion. MATERIALS AND METHODS: Feldspathic ceramic Vitablocks™ TriLuxe forte (VTF), lithium disilicate glass IPS e.max Press™ (IPS) and zirconia reinforced lithium silicate Vita Suprinity™ (VS) ceramic blocks (n = 27 per group) were prepared from sintered CAD blocks using a water-cooled saw. They were further subdivided into 3 subgroups according to the surface treatment protocols (n = 9): as prepared, roughened and polished. The surface roughness of the ceramic blocks was measured using an electro-mechanical profilometer. The ceramic sections were inoculated with Streptococcus mutans and incubated for 48 hours to form a biofilm. The ceramic surfaces with the biofilms were analyzed using Confocal Laser Scanning Microscopy to calculate the percentage of live bacteria and substratum coverage by the biofilm, and further visualized using scanning electron microscopy. Statistical analysis was done with SPSS software using two-way ANOVA, followed by post hoc Bonferroni test to identify significant differences between the groups. The level of significance was set at p = 0.05. RESULTS: As prepared VTF showed significantly higher mean surface roughness values than as prepared IPS and VS. The mean percentage of live bacteria and biofilm coverage of the substrate were significantly higher in the roughened ceramic blocks than the as prepared and polished blocks for all three ceramic types (p < 0.05). Polished specimens of VS significantly lower percentage of biofilm coverage than the other groups (p < 0.05). CONCLUSIONS: This study sheds new light that adjustments of ceramic restorations prior to cementation increases the likelihood for formation and adhesion of microbial biofilms on the surface. Polished zirconia reinforced lithium disilicate ceramics demonstrated the lowest bacterial adhesion among the evaluated ceramics.

'Evaluation of the introduction of a dental virtual simulator on the performance of undergraduate dental students in the pre-clinical operative dentistry course'.

INTRODUCTION: Virtual reality-based platforms are becoming increasingly popular in education. The aim of this study was to evaluate the performance of undergraduate dental students with the introduction of the Moog Simodont dental trainer (VR) within the pre-clinical curriculum in the direct restoration module of the operative dentistry course using manual and digital methods. METHODS: Thirty-two randomly selected year 2 undergraduate students were divided into two groups: group 1, exposed to the Moog Simodont dental trainer (VR) and group 2, no exposure to VR. All students were then evaluated in carrying out a Class I preparation in a single-blinded fashion. All preparations were evaluated by three assessors using a traditional manual approach and a digital software. Statistical analysis of the data was performed using chi-square test (alpha = 0.05). RESULTS: The number of students who performed satisfactory preparations was more in group 1 (12/16), compared to group 2 (7/16). The percentage of satisfactory domains was significantly higher in group 1, compared to group 2, both in the manual evaluation (83.9% (94/112) and 59.8% (67/112) in groups 1 and 2, respectively) and in the digital evaluation (85.7% (96/112) and 55.4% (62/112) in groups 1 and 2, respectively) (P < .05). There was no significant difference between the manual and digital methods of evaluation with regard to the percentage of satisfactory or unsatisfactory preparations (P > .05). CONCLUSIONS: The use of the Moog Simodont dental trainer (VR) significantly improved the satisfactory performance of students. The virtual reality simulator may be a valuable adjunct in the undergraduate direct restorations course and for remedial student.