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Abstract The success of dental implants has changed treatment planning for patients with edentulous areas dramatically. A critical determinant for placement of an implant is the height and width of bone available in the edentate sites. The clinician also needs to evaluate the angulations of the ridge before placing the implant. Ideally, implants should be placed parallel to each other and to adjacent teeth. Titanium is a metal, and suffers corrosion. Corrosion, the gradual degradation of materials by electrochemical attack is a concern particularly when a metallic implant is placed in the hostile electrolytic environment provided by the human body. The improvements in new ceramic materials made it possible on 2000 to have the abutment part made of ceramic. This material was commonly known to be more tissue friendly than titanium. Conventional titanium abutments are widely used as the trans- gingival components of dental implants. 1 In recent years, in order to achieve a final implant-supported prosthesis indistinguishable from the adjacent natural teeth, zirconium abutments have been favored for their aesthetic benefits, especially in the anterior zone. 2, 3 Zirconia has an excellent resistance to corrosion, biocompatibility, and high levels of loading capacity.4 Dental implants have been used as a successful restoration treatment for tooth replacement over the last few decades. Nevertheless, there is some controversy regarding the clinical procedures or materials. The method for connecting the prosthesis to an implant is one of the most important topics.5,6,7, 8 Cement-retained prostheses allow a passive fit, and have the advantage of simplicity in fabrication, better esthetics and occlusion. In addition, reduced chair time is needed compared to screw retained prostheses. Therefore, cement-retained prostheses are more economical and effective.5 Such advantages account for the recent increase in clinical use but clinicians often face difficulties due to the inconvenient retrieval.6,9,10 Esthetic dentistry, driven by a high demand for esthetically appealing and naturally looking restorations (especially all-ceramic restorations) has become a segment of dentistry which has experienced tremendous improvements in recent years 11,12. The drawbacks of metal- ceramic restorations have prompted the development of new all-ceramic systems that do not require metal, yet have the high strength, precision fit, superior esthetics and optical properties not seen in metal-ceramics systems13,14. Ivoclar Vivadent patented lithium disilicate material, which exhibits superior esthetics and durability combined with satisfactory physical properties to replicate natural tooth structure for aesthetically pleasing and undetectable restorations. When fabricated to full-contour, the monolithic structure is the most robust ceramic system tested to date 15. Furthermore, due to a demand for posterior segment all-ceramic restorations, Yttrium Tetragonal Zirconia Polycrystal(Y-TZP) based systems are a recent addition to the high-strength all ceramic systems used for crowns and fixed partial dentures2. CAD/ CAM-produced, Y-TZP- based systems are in considerable demand in esthetic and stress-bearing regions 16. The esthetic nature of zirconia, coupled with its superior physical properties and biocompatibility have resulted in restorative systems that meet the demands of today’s patients. All ceramic restorations benefit from technologies that automate aspects of their fabrication 17. Automation implies less reliance on the skill of the individual ceramist, as well as greater homogeneity and lower probability of defects within the material itself . |