RESUMEN
Objective To study the effect of adhesive overflow grooves on the marginal and internal adaptation of a molar zirconia full crown.Methods A three-dimensional model of a mandibular first molar was established.Four crown preparations (A-D) were designed:a was a conventional full crown design,and B,C,and D included 1,2,and 4 adhesive overflow grooves,respectively,designed on the basis of A.Five resin preparations were created for each group using three-dimensional (3D) printing.According to the a design data,20 CAD/ CAM zirconia crowns were prepared and randomly divided into four groups.The tooth,preparations,and crowns underwent 3D scanning for 3D deviation analysis and 3D wall thickness analysis.The gap between the crown and the preparation was replicated with silicone rubber,and then observed with a metallographic microscope and measured.Data were statistically analyzed with SPSS 17.0.Results Among the groups,marginal and internal clearance was A＞B＞C＞D.The comparison between every two groups was statistically different (P ＜ 0.05).Conclusion Increases in the number of overflow grooves result in significant increases in the marginal adaptation and internal adaptation of a full crown.