Objective:The purpose of the study was to compare the fracture resistance of ceramic veneers and composite resin veneers with and without dental preparation.Materials and Methods:Forty freshly extracted mandibular premolars were selected and randomly assigned into four groups (n = 10): Group NPR = no dental preparation and direct veneer with 0.2 mm thick composite resin (Amelogen Plus, Ultradent); Group NPC = no dental preparation and 0.2 mm thick lithium disilicate ceramic veneer (IPS e.max Press, Ivoclar Vivadent); Group P2C = Tooth preparation of 0.2 mm and 0.2 mm thick ceramic veneer (IPS e.max Press); and Group P5C = Tooth preparation of 0.5 mm and 0.5 mm-thick ceramic veneer (IPS e.max Press). In all groups, the restorations covered 1 mm of the occlusal surface of the buccal cusp, and the thickness of this area was the same of the buccal area (0.2 mm or 0.5 mm). After the luting procedure, all groups were thermocycled (10,000 cycles, 5°C–55°C) and subjected to fracture resistance test under compression (Instron 4444 with a crosshead speed of 0.5 mm/min). The mode of failure analysis was performed under a ×10 magnification. Data were subjected to one-way ANOVA and Duncan's post hoc test (P < 0.05).Results:The mean fracture resistance (men ± standard deviation) was NPR = 690.33 ± 233, NPC = 790.52 ± 408, P2C = 1131.34 ± 341, and P5C = 983.56 ± 202. There were significant differences of the fracture resistance values between all groups (P = 0.013). NPR and NPC groups showed mean values of fracture resistance significantly lower than P2C. However, P5C presented intermediate values without a significant difference from the other groups. The mode of failure for all groups was mixed (60%), cohesive failures (20%), root failures (15%), and adhesive failures (5%).Conclusion:Minimally invasive tooth preparation (0.2-mm) allowed to achieve higher fracture resistance in premolars restored with lithium disilicate ceramic veneers. Attention should be given to the 0.5 mm preparation since catastrophic fractures only happened when this preparation depth was performed.

Objectives. The purpose of this clinical trial was to evaluate the influence of in-office dental bleaching on the pulp oxygen saturation (SpO2p) reading. Material and Methods. SpO2p was measured using a pulse oximeter in 112 upper and lower anterior teeth (canines and incisors) of patients submitted to bleaching. Whitegold Office 35% (WGO) (upper and lower left hemiarch) and Whiteness HP Auto Mixx 35% (WHP) (upper and lower right hemiarch) bleaching agents were used. SpO2 measurements (teeth and index finger) were taken before and after each of the three application sessions of the agents. In the 4th session, in which no bleaching gel was used, only SpO2 was measured. Before and after the bleaching sessions, a colorimetric device performed the teeth color reading. The waiting time between sessions was 7 days. Data were analyzed by the Friedman, Kruskal–Wallis, and Mann–Whitney U tests (α = 0.05). Color change (ΔE) data were correlated (Spearman’s Rho test) with the SpO2p levels. Results. Neither of the two bleaching agents showed significant differences between the readings when evaluated individually (WGO, P = 0.780 , and WHP, P = 0.494 ). When taken together, the results showed significant difference between the readings performed, with higher median values after bleaching sessions: before (97.3) and after (98.6) 1st session; before (98.3) and after (98.3) 2nd session; before (98.3) and after (99.0) 3rd session; and after 1 week (98.3). The dental groups formed by maxillary lateral incisors ( P = 0.012 ) and mandibular incisors ( P < 0.001 ) showed a significant difference. Spearman’s Rho test showed a nonsignificant and weak correlation between ΔE and SpO2p in most comparisons. Conclusions. The in-office dental bleaching influenced the SpO2p reading, regardless of the dental group evaluated or the bleaching agent used. Clinical Relevance. This study provides information about the influence of in-office tooth whitening on the pulp SpO2p levels. The observation of pulp vitality during and after the use of bleaching agents is important for the follow-up of patients undergoing tooth whitening. The use of a pulse oximeter may be a viable and painless alternative to perform this monitoring. The clinical trial was registered with the Brazilian Registry of Clinical Trials (ReBEC; registration number: https://clinicaltrials.gov/ct2/show/RBR-68xbth).

The cavity preparation weakens the remaining tooth structure; however, its resistance could be partially restored using direct adhesive restorations.

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