Effect of cement space settings on the marginal and internal fit of 3D-printed definitive resin crowns

Abstract

Statement of problem The cement gap setting affects the marginal and internal fits depending on the crown material and manufacturing method (subtractive or additive manufacturing). However, information on the effects of cement space settings in the computer-aided design (CAD) software program, which is used to aid the manufacturing with 3-dimensional (3D) printing-type resin material, is lacking, and recommendations for optimal marginal and internal fit are needed.

Purpose The purpose of this in vitro study was to evaluate how cement gap settings affect the marginal and internal fit of a 3D-printed definitive resin crown.

Material and methods After scanning a prepared typodont left maxillary first molar, a crown was designed with cement spaces of 35, 50, 70, and 100 μm by using a CAD software program. A total of 14 specimens per group were 3D printed from definitive 3D-printing resin. By using the replica technique, the intaglio surface of the crown was duplicated, and the duplicated specimen was sectioned in the buccolingual and mesiodistal directions. Statistical analyses were performed using the Kruskal–Wallis and the Mann–Whitney post hoc tests (α=.05).

Results Although the median values of the marginal gaps were within the clinically acceptable limit (<120 μm) for all the groups, the smallest marginal gaps were obtained with the 70-μm setting. For the axial gaps, there was no observed difference in the 35-, 50-, and 70-μm groups, and the 100-μm group showed the largest gap. The smallest axio-occlusal and occlusal gaps were obtained with the 70-μm setting.

Conclusions Based on the findings of this in vitro study, a 70-μm cement gap setting is recommended for optimal marginal and internal fit of 3D-printed resin crowns.