EFFECT OF THREE VENEERING TECHNIQUES ON MARGINAL ACCURACY AND FRACTURE RESISTANCE OF ZIRCONIA BASE FIXED RESTORATION (IN-VITRO STUDY).

Statement of the problem. Veneered zirconia restorations are frequently used for esthetic demands , however marginal accuracy and fracture resistance are among the critical factors that determine longevity and success of these restorations. These two items may be affected by veneering procedures. Purpose. The aim of this systematic review was to identify from in vitro studies the effect of veneering techniques on the marginal accuracy and fracture resistance of zirconia restorations. Materials and methods. The articles identified were screened by two reviewers according to inclusion and exclusion criteria. The reference lists of articles advanced to second round screening were hand searched to identify additional potential articles. Sources: An electronic search was conducted on PubMed/Medline, Cochrane, Google scholar, Sciencedirect and Springerlinnk databases with no limitations. Results . Study selection: 387 articles were identified, of which, nine met the inclusion criteria and formed the basis of this systematic review. Factors investigated in the selected articles included the sample size, type of restoration , die material ,preparation criteria , veneering technique , cementation , method of measuring fracture resistance , method of measuring marginal accuracy , results of fracture and results of marginal accuracy. Conclusions.Based on the currently available scientific evidence, The zirconia veneering technique significantly influences the fracture resistance of zirconia-based crowns, the layering veneering technique crowns recorded the highest failure loads, while the digital veneering technique crowns recorded the lowest failure loads, the combination of the CAD ?CAM and the press-over techniques for the veneering process improves thestability after artificial ageing relative to the layeringtechnique, Anatomical framework design increased the fracture resistance when alayering veneering technique was employed , No articles were found studying effect of veneering technique on marginal accuracy of zirconia restorations. Recommendations.Before they can be recommended for daily application, the effect of newly introduced veneering techniques on the long-term stability of Y-TZP-based zirconia fixed dental prosthesis must be verified in well-designed, randomized clinical trials. Further studies should study effect of veneering technique on marginal accuracy of zirconia restorations.