Endocrowns represent a conservative and esthetic restorative alternative to full coverage crowns. They can be constructed using various CAD/CAM materials that can provide a modulus of elasticity similar to that of teeth. The ability to use of such materials in composite blocks that can be easily repaired is also an advantage, provided appropriate bonding performance is ensured. This study, therefore, evaluated the marginal gap and fracture resistance of two CAD/CAM endocrown materials using two bonding protocols. Thirty-two mandibular molars were evaluated in two groups based on the material type: a Cerasmart group (GC America Inc; n ¼ 16) acting as the control and a Ceramill COMP group (Amann Girrbach, Germany; n ¼ 16). These groups were then classified according to the bonding protocol used: a total-etch bonding protocol (n ¼ 8) and a self-etch bonding protocol (n ¼ 8) implemented using RelyX ultimate adhesive resin cement (3M ESPE). The samples were then subjected to aging by simulating a 1-year thermomechanical process. The marginal gap results were statistically insignificant across the material and bonding protocol groups before thermo-mechanical aging. Thermo-mechanical aging significantly reduced the marginal gap distance for Ceramill COMP endocrowns cemented using the total-etch protocol (p ¼ 0.002). No statistically significant difference was recorded for the fracture resistance in either the material or bonding protocol groups (p ! 0.05). Both materials and bonding protocols can, therefore, be used in the posterior region providing conservative treatment, adequate marginal gap and fracture resistance.

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Objective: To evaluate the wear behavior of human enamel and chipping of veneered and monolithic zirconia for posterior full coverage restorations. Material and methods: Thirty-four zirconia full coverage restorations (seventeen in each group) were fabricated. The patients were divided into two groups according to the type of zirconia used; group 1 (comparator group) veneered zirconia crowns and group 2 (intervention group) monolithic zirconia single crowns. All crowns were lab fabricated and polished. For opposing teeth wear measurements 3D non-contact profilometer was used where epoxy resin replicas were constructed for opposing arch immediately after crowns cementation, three, six and twelve months. Restoration chipping was measured using modified United States Public Health Services (USPHS) criteria. Results: All restorations were reported as alpha with no chipping. There was no statistically significant difference between (Group 1) and (Group 2) for wear test. Conclusion: Both monolithic and veneered restorations revealed satisfactory mechanical properties with no chipping after one year of clinical use. Wear of opposing enamel was clinically acceptable for both materials. Keywords Ceramics; Chipping; Monolithic zirconia; Veneered zirconia; Wear.

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Statement of the problem: The rehabilitation of severely damaged coronal hard tissue and endodontically treated teeth has always been a challenge in reconstructive dentistry. These teeth have been shown to exhibit a significantly shorter service life and an increased failure rate when compared with vital teeth. Objective: This study evaluated the vertical marginal gap distance and retention of bonded CAD/CAM Ceramic Endocrowns as a conservative alternative in endodontically treated molar teeth following thermal cycling and fatigue loading compared to post and core supported Ceramic crowns. Methods: Ninty caries free human molar teeth were selected and mounted in epoxy resin blocks. For vertical marginal gap distance test, sixty teeth were assigned into six groups (n=10) according to type of restoration as follows; GroupI: Endodontically treated teeth incorporating 1mm ferrule restored with IPS Empress CAD endocrowns. Group II: Endodontically treated teeth incorporating 1mm ferrule restored with IPS e.max CAD endocrowns. Group III: Endodontically treated teeth without incorporating ferrule restored with IPS Empress CAD endocrowns. Group IV: Endodontically treated teeth without incorporating ferrule restored with IPS e.max CAD endocrowns. Group V: Endodontically treated teeth incorporating 1mm ferrule restored with glassfiber posts, composite cores and IPS Empress CAD crowns serving as a control group. Group IV:Endodontically treated teeth incorporating 1mm ferrule restored with glass-fiber posts, composite cores and IPS e.max crowns serving as another control group. For retention test, thirty teeth were divided into six groups (n=5). Same designs and types of restorations for the previous test were used for the retention test. All teeth were sectioned perpendicular to the long axis 2mm coronal to the proximal CEJ and then subjected to a standard endodontic treatment. A special milling machine was used for teeth preparation. All-Ceramic endocrowns and crowns were constructed using the Cerec InLab system and cemented with Rely x ARC dual cure adhesive resin cement. The vertical marginal gap distance was measured after cementation using a stereomicroscope. Measurements