Background: Despite the fact that preliminary clinical results of conservative partial coverage restorations (PCRs) are promising, the clinical behavior of different PCR ceramic materials is rarely investigated in clinical trials. This study aimed to evaluate the clinical outcomes of partial coverage restorations (PCR) fabricated with zirconia-reinforced lithium silicate ceramic system compared to partial coverage restorations fabricated with lithium disilicate ceramic system. Methods: 46 vital premolars and molars of 14 patients were restored with PCRs (23 Vita Suprinity and 23 IPS e.max CAD). PCRs were CAD/CAM fabricated in the lab and adhesively luted with dual-polymerizing resin cement (Duolink. BISCO, USA). Clinical evaluation of PCRs was performed according to the Modified United States Public Health Service (USPHS) at baseline, 6 and 12 months post-insertion. Absolute failure was demonstrated by Kaplan-Meier survival rate analysis. Results: After 12 months observation, all PCRs of both ceramic groups demonstrated 100% survival rate. Non-significant decrease in Alpha ratings for marginal adaptation (p = 0.1560) and marginal discoloration (p = 0.6078) in e-max group. While in the Suprinity group, PCRs demonstrated 100% Alpha ratings for marginal adaptation and only one Bravo rating (p= 0.3625) for marginal discoloration after 12 month observation. Conclusions: Both Vita-Suprinity and e.max CAD partial coverage restorations are considered reliable treatment options for restoring larger defects in posterior dentition. Trial registration: ClinicalTrials.gov NCT02861729 04/08/2016

Background: Treatment of patients with severe tooth wear is complex. Treatments involving more tooth structure removal may be inappropriate for patients who have already lost a significant amount of dental tissue due to erosion. The aim of this study was to evaluate the effect of two modified occlusal veneer preparations on the fatigue resistance and stress distribution of bonded occlusal veneers, in comparison to the conventional preparation design. Methods: A total of 54 human mandibular molars were distributed into three equal groups of n=18 teeth each, according to the occlusal veneer preparation design, where group I (conventional design) received Planar occlusal veneer preparation, group II (occlusal veneer with circumferential finish line) and group III (occlusal veneer with intracoronal cavity extension). For the manufacture of all the veneers using machinable zirconium lithium silicate glass ceramic blocks, a computer aided design/manufacturing system was used. A dual cure, adhesive resin cement was used to bond all occlusal veneers to corresponding prepared teeth. After storage in water for one week, step-stress (accelerated life testing was performed for all samples. Finite element analysis was carried out as well to evaluate the distribution of stresses. Results: The highest values (mean±SD) were recorded for group II (890.57±211.53 N) followed by Group I values (883.54±135.91 N), while the lowest values were recorded for Group III (875.57±143.52 N). The difference between groups was statistically non-significant as indicated by ANOVA (P=0.9814>0.05). The stress values were generally found to be low and their distribution differed among groups. Conclusion: Group I and II showed comparable fatigue resistance and more favourable failure behaviour when compared to Group III based on the fractographic and 3D finite element analyses.

Statement of problem: marginal inaccuracy causes a space between restoration and prepared tooth, which accelerates cement dissolution, leading to secondary caries, pulpal lesions, postoperative sensitivity, periodontal disease and marginal discoloration. Marginal gap should be less than 120µm. Aim: to evaluate vertical marginal gap of PEEK (Bio-HPP) veneered with CAD/CAM composite veneer (HIPC) as compared to zirconia veneered with CAD-On lithium disilicate glass ceramic. And the effect of ageing on the gap of both restorations. Material and methods: 40 extracted molars were prepared, divided into two groups, control group (ZR) (n=20), teeth restored with IPS e.max ZirCAD copings veneered with IPS e.max CAD and intervention group (PEEK) (n=20), teeth restored with breCAM BioHPP copings veneered with BreCAM.HIPC. Each specimen was photographed using Leica S8 APO stereomicroscope under magnification 32X and image analysis was done. Measurements were taken twice before and after thermomechanical cycling. Results: PEEK group recorded higher gap mean values (49.88±7.97um) than zirconia (18.39±3.1um). This was significantly (p < 0.05) as confirmed by Mann-Whitney test, but all measurements were clinically acceptable. And Thermo-mechanical cycling had no effect of on both groups. Conclusion: PEEK veneered with composite can be used intra orally for single crown restorations.

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