In Vitro Investigation of Marginal & Internal Adaptation of Two Screw-Retained Implant Supported Crowns: A Comparative Analysis of Direct Optical & Subtractive Reverse Engineering Techniques.

Objectives: The aim of this in-vitro study was to investigate the marginal and internal adaptation of two screw-retained crowns; lithium disilicate and BioHPP using direct optical and subtractive reverse engineering techniques and to calculate the degree of agreement between them. Materials & Methods: Twenty-eight implant analogs were embedded perpendicularly in an auto-polymerizing resin. Implant-supported restorations were designed then milled with CAD wax and divided into 2 groups according to material (n=14): Lithium disilicate and BioHPP. Each group was pressed according to the manufacturer’s instructions. The marginal and internal adaptation of the specimens were analyzed using DOT & subtractive RET. Data were explored for normality using Shapiro-Wilk’s and Levene’s tests and were analyzed using independent and paired t-test for inter and intragroup comparisons respectively with a significance level of p<0.05. Agreement analysis was done using intraclass correlation coefficient (ICC). Results: BioHPP screw-retained implant-supported crowns showed higher marginal gap than lithium disilicate, yet the difference was non-significant when measured using DOT, while it was significant when measured using sRET. Calculated agreement between the two techniques at the marginal level showed that there was a statistically significant moderate agreement between both methods. Regarding internal adpatation, BioHPP had a statistically significant higher internal gap than lithium disilicate group. Conclusions: Supra-structure material affected marginal and internal adaptation of implant-supported restorations. Pressed lithium disilicate crowns showed better marginal and internal adaptation than BioHPP crowns, however, both groups showed clinically acceptable results. DOT and RET were both relevant and showed moderate agreement between them.