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Statement of the problem: Monolithic hybrid and glass ceramics are indicated for intracoronal and extracoronal ceramic restorations. Available data regarding selection of the appropriate ceramic type for each preparation design and its influence on fracture resistance of tooth restoration complex is still scarce. Purpose:The purpose of this study was to evaluate in vitro the fracture resistance and investigate failure mode of two restoration designs (crowns and inlays) made from lithium disilicate glass ceramic and hybrid ceramic constructed by the CAD /CAM technique. Materials and Methods:A total of twenty ceramic restorations restoring lower molars were designed and fabricated in this study. The restorations were divided into two groups; Group 1: Ten full coverage crowns and Group 2: Ten inlays. Each of the previous groups was further subdivided into two equal subgroups; Subgroup 1: Five restorations constructed from lithium disilicate glass ceramics (e.max CAD) and Subgroup 2: Five restorations constructed from hybrid ceramic (VITA ENAMIC) by the CAD/CAM technology. Two ivorine teeth were prepared following the guidelines for full coverage and inlay ceramic restorations, they were duplicated into stone dies followed by scanning, designing and milling of restorations. The stone dies were duplicated into epoxy dies where the restorations were adhesively cemented on them. All cemented samples were exposed to 2000 thermal cycles (5°C and 55°C in water) with a dwell time of 25 seconds in a computer controlled thermocycler. All specimens were loaded in a universal testing machine where fracture test was done by compressive mode of load applied occlusally using a metallic rod with round tip at cross-head speed of 1mm/min until fracture occurred. Fracture resistance values were recorded in Newtons then they were statistically evaluated and failure modes were analyzed. Results:For group 1 representing crown restorations, a statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.05) where the highest mean value of maximum load was found in (VITA ENAMIC

Statement of the problem The increased thickness of ceramic laminate veneer with butt joint design at the incisal edge reduce the amount of light reaching the cement layer and therefore compromise photo-activation of the luting material However, an adequate cure of the resin-based cement is an important prerequisite for the stability and biocompatibility of the restoration. 57 Dual-cure resin-based cements have been recommended for luting ceramic laminate veneers to compensate for the attenuation of the curing light effected by the thickness of restoration and to allow complete polymerization of the luting material even at the incisal area of laminate veneers where access for the curing light is limited, but the yellowish discoloration due to ageing of conventional dual-cure resin based cement was the problem. Purpose : The aim of this study was to evaluate color stability of e-max CAD veneers cemented with light cure and dual cure amine free adhesive resin cement (Base line), (After 2 months), (After 4 months), (After 6 months),(After 8 m) Materials and methods: A total of 22 ceramic laminate veneers restorations(11 e.max cad cemented with light cure adhesive resin cement and 11 e.maxcad cemented with dual cure adhesive resin cement) were included in the study and completed by one operator (the researcher) who followed a meticulous clinical procedure and the ceramic laminate veneers were fabricated by one experienced dental technician. The operator followed the five phases of laminate veneers fabrication: diagnosis, preparation design, provisionalization , construction of the material and bonding ,Follow up sessions were done every two month for each patient using operator vision to evaluated change in color and then confirmed with easyshade in the baseline, 24 hours post cementation and in the postoperative follow-up according to the modified USPHS (United States Public Health Service) criteria. This was performed by an experienced, blinded investigator. Data were recorded, tabulated, and statistically analyzed using the Chi-square test and the significance level was set at P ≤ 0.05. Results: There was no statistically significant difference between (Group I) and (Group II) where (p=1) as both groups showed (100%) Alpha in all time periods. Conclusion: Both E.max CAD laminate veneers cemented with light cure and E.max CAD laminate veneers cemented with dual cure amine free adhesive resin cement revealed high successful survival rate in terms of the stability of the color.

Aim:The aim of the present study was to assess the shade difference between zirconia strengthened lithium silicate ceramic (Celtra Press) VS lithium disilicate glass ceramics (e.max) in reference to the natural tooth optical properties to determine which monolithic material will replicate the exact shade and optical properties of the corresponding natural tooth structure.Materials and Methods: 20 teeth esthetic zone requiring full coverage crown -with their adjacent/contralateral are sound and not severely discolored -were selected to receive a ceramic crown and divided into 2 groups: Group 1: Teeth prepared to receive crowns fabricated from IPS e.max press (Ivoclar Vivadent) Group 2: Teeth prepared to receive crowns fabricated from Celtra Press (Dentsply Sirona). The patient satisfaction values of the two groups was evaluated using Visual Analogue Scale (VAS) of satisfied or unsatisfied documented in a chart. Color difference in reference to the natural tooth was evaluated by 3 experienced evaluators using modified United States public health service (USPHS) criteria as Alpha(excellent), Bravo (acceptable), Charlie(acceptable but alterations required) and Delta(unacceptable). The color difference ΔE (perceptibility threshold) was measured using intraoral spectrophotometer and evaluated for each group.Results: Regarding patient satisfaction, there was no statistically significant difference between (Group I) and (Group II) where (p=1) as both groups showed (100%) Alpha satisfied. Concerning shade matching, there was no statistically significant difference between (Group I) and (Group II) where (p=1) as both groups showed (100%) Alpha. Conclusions:Within the limitations of this clinical study, Celtra Press and Emax press materials when used for full coverage restorations resulted in excellent patient satisfaction and color matching results. This dictates that both materials have clinical acceptable shade matching and patient satisfaction.

Aim:The study was conducted to evaluate the internal fit and marginal adaptation of custommade Pressable compared to CAD/CAM PEEK post and core at three levels.Methodology: Twenty-eight extracted maxillary central incisors were prepared for custom post and cores. Acrylic resin patterns were fabricated and divided into two groups: CAD/CAM group: The resin patterns were directly scanned and milled from modified PEEK blocks and Press group: Patterns were pressed with PEEK granules. The cement thickness was measured at four standardized points and the vertical marginal discrepancy was measured at twelve points using scanning electron microscope. One Way-ANOVA and Tukey`s post hoc test were performed to compare between the sections of each group; while Independent T-test was performed to compare between the two groups at different sections.Results: Regarding CAD/CAM group, the mean cement thickness was the highest in the coronal section (85.57±17.81) followed by the middle (72.87±18.57) then the apical (45.92±18.73). While for Press group, the middle section showed the highest mean cement thickness (50.99±15.98), followed by the coronal section (39.70±18.16), the apical section (21.37±4.30). Comparing the two groups, CAD/CAM group had a significantly higher internal gap in all sections (P=0.0001). Among cores marginal adaptation, no significant difference in means of all surfaces was revealed between the CAD/CAM (98.83±13.90) and press (95.08±13.91) groups (P=0.54) Conclusion: Within the limitations of this study, pressed PEEK post and cores achieved superior internal fit compared to CAD/CAM. Neither CAD/CAM nor pressing technique influenced the marginal adaptation of PEEK cores and both were within the clinical acceptance range.