Purpose:The purpose of this study was to compare marginal fit of Zirconia and Polyetheretherketone (PEEK) inlay retained fixed partial dentures (IRFPD) fabricated by using a computer-aided design and computer-aided manufacturing (CAD-CAM) system. Materials and Methods: Sound Mandibular second premolar and mandibular second molar were selected to simulate a clinical situation of a missing mandibular first molar and embedded in an epoxy resin (master model). Both teeth received a standard preparation of IRFPD with respect to all-ceramic preparation design parameters. The master model was duplicated into 18 epoxy resin models for standardization during testing procedure, and 18 IRFPDs were fabricated with CAD-CAM system and divided into 2 groups according to materials type (n=9); Group 1: 3-mol yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), Group 2: PEEK. Marginal Discrepancy of all bridges was tested before and after cementation with RelyX U200 self-adhesive resin cement (SARC) by using an optical digital microscope with the aid of an image analysis system. Results: Significantly lower marginal gap values were obtained in Zirconia group before and after cementation in comparison to PEEK group. There was also a significant increase of marginal gap after cementation in both groups, with higher mean in Zirconia group. Conclusion: The margins of IRFPDs performed well with recommended bonding protocols for both materials and present a viable treatment option for replacing a missing single posterior tooth. Both materials presented clinically accepted results of marginal discrepancy less than 120 µm. Further studies simulating clinical conditions are needed to understand how they perform in function.

Purpose:The aim of this study was to assess the fracture resistance of PEEK endocrowns and post-retained PEEK crowns with two preparation designs (ferrule and without ferrule). Materials and methods: Eighty sound human mandibular first premolars were selected. Teeth were divided into 4 main groups (n= 20): Group1: Were assigned for endocrown preparation with Butt joint. Group 2: Were assigned for endocrown preparation with Shoulder finish line. Group 3: Were assigned for PEEK post & core preparation without ferrule. Group 4: Were assigned for PEEK post & core preparation with ferrule. Endocrowns of both Group 1 and Group 2 were made of PEEK material veneered with composite. Both Group 3 and Group 4 were covered with PEEK crowns veneered with composite. All Restorations either PEEK post & cores or endocrowns and final crowns were sandblasted with 110 Mm aluminium oxide. Finally, cemented with self-adhesive resin cement (G-Cem cement). Results: The highest mean value was recorded in Post & core with ferrule (above CEJ) (1262.29±65.02), followed by Endocrown with Butt Joint (1101.44 ± 81.7), then Endocrown with Shoulder finish line (890.99±75.42), with the least value recorded in Post & core without ferrule (below CEJ) (726.03±71.26). Statistically, ANOVA test showed a considerable difference between groups (p=0.00). Tukey's post hoc test showed a considerable difference between each 2 groups. Conclusion: It was concluded that the mandibular premolars that were restored by PEEK Post-cores covered with crowns which designed with ferrule recorded the highest fracture resistance load.

Purpose: This study examined the effect of change in sintering time on the optical properties of monolithic zirconia crowns using ZirCAD Prime. Materials and methods: A Sound premolar was scanned using optical oral scanner. The scanned premolar was digitally prepared to receive zirconia restoration using Exocad software following standard preparation guidelines for ceramic restorations. 3D printed resin master die was produced. An impression was made for the 3D printed master die using polyvinylsiloxane impression material then poured using epoxy resin. The procedure was repeated to obtain 16 epoxy resin models. Sixteen crowns were produced by CAD-CAM system from ZirCAD Prime blank shade A2 with 16 mm thickness. Samples were divided into two groups according to sintering time (n=8). Group (A): crowns were sintered using normal sintering cycle for 9h and 50 min. Group (B): crowns were sintered using speed sintering cycle for 2h and 26 min. After sintering the internal surfaces of both groups were abraded with 50 μm Al 2 O 3 particles. Optical properties including Translucency Parameter (TP) and change in color (ΔE) of samples were determined using spectrophotometer. Obtained values were statistically analyzed. Results: Regarding change of color evaluation mean ∆E values were below 3.0 which is considered "clinically imperceptible". There was also no significant difference in translucency parameter between both groups. Conclusion: ZirCAD Prime speed sintering cycle will have no perceived effect on color and translucency of the final restoration.

Purpose: This study was designed to evaluate the effect of the size of occlusal contact areas of single implant supported restoration on occlusal load distribution on adjacent premolars using a digital occlusal analyzer (T-Scan). Material and Methods:Twenty four patients with missed lower first molar were received delayed dental implants, where they divided into 2 main groups according to the presence or absence of adjacent lower second molar (n=12). Group (Ι): Patients with missing mandibular first molar with the presence of adjacent second molar and premolar teeth,while group (ΙΙ): Patients with missing mandibular first molar tooth with the presence of adjacent premolars and absence of adjacent distal molars.Two occlusal schemes were followed during superstructure construction, dividing each group into two subgroups, (n=6).Patients were evaluated for occlusal load distribution before and after cementation of the crown, and after 3 and 6 months using T-scan system (9.1). Results: Regarding second premolar; the occlusal load distribution % in the different groups was statistically insignificant. Regarding first premolar; occlusal scheme 1 in both groups showed statistically significantly higher median occlusal load distribution % on the lower first premolar than occlusal scheme 2 in both groups. Conclusion: The size of occlusal contact area of the implant supported crown is an important factor affecting occlusal load distribution on adjacent premolars. Decreasing the size of occlusal contact area of the implant supported crown will increase the force on adjacent premolars.