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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

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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Objective: investigation of the microshear bond strength between lithium disilicate with preheated viscous composite, flowable composite and resin cement by comparison of their microshear bond strength.Material and method: forty-five samples were prepared and divided into three groups; preheated viscous composite, flowable composite and resin cement. Materials were injected into plastic transparent molds (2 mm height, 2 mm diameter) on the surface of lithium disilicate discs previously surface treated with ceramic etchant (hydrofluoric acid 4.5%) and ceramic primer (silane coupling agent). Microshear bond strength test was performed samples by universal testing machine.Results: highest microshear bond strength was recorded for preheated viscous composite.Conclusions: preheated viscous composite is an excellent material in cementation of lithium disilicate ceramic restorations.