Comparison of posterior indirect adhesive restorations (PIAR) with different preparations designs according to the adhesthetics classification. 
Part 2: Effects on marginal quality

Aim: To investigate whether different restoration designs, overlay types, and full crowns in posterior teeth have similarly acceptable marginal sealing and quality. Materials and methods: For Part 1 of the present study (investigation of fracture resistance), 70 extracted molars were divided into five groups (N = 14), prepared with four different posterior indirect adhesive restoration (PIAR) overlay design types, according to the adhesthetics classification. The groups were: 1. Butt Joint; 2. Full Bevel; 3. Shoulder; 4. Full Crown; 5. Sound Tooth. For Part 2 of the study (present article; marginal quality), there was no group 5, and only 56 of the 70 extracted molars were used. Seven expert dentists performed all the preparation and cementation phases with codified protocols. A CAD/CAM workflow was used to realize the 56 monolithic lithium disilicate restorations. The samples were tested with thermomechanical loading (TML) and the marginal quality evaluated. The data relating to fracture resistance are presented in Part 1 of this study (Int J Esthet Dent 2021;16:2-17). Results and conclusions: In terms of marginal quality after TML, within the limitations of the present study, in molar teeth (without endodontic treatments) restored with different monolithic ceramic lithium disilicate PIAR designs, it is possible to present the following conclusions.