Effects of different fabrication techniques on the marginal gap of interim crowns as assessed by optical coherence tomography: An in vitro study.

Abstract

Statement of problem: Studies on the assessment of the marginal fit of interim crowns with optical coherence tomography (OCT) are lacking.

Purpose: The purpose of this in vitro study was to apply OCT to evaluate and to compare the impact of conventional and computer-aided design and computer-aided manufacturing (CAD-CAM) fabrication methods and different materials, including bis-acryl, conventional polymethyl-methacrylate (PMMA), and CAD-CAM PMMA, on the marginal fit of interim crowns.

Material and methods: Thirty crown specimens were fabricated, with 20 PMMA crowns divided into 2 groups based on the fabrication method: the conventional method (Group Jet, n=10) and the CAD-CAM method (Group CAD-CAM PMMA, n=10). An additional 10 bis-acryl crowns were fabricated using the conventional method (Group Protemp, n=10). The marginal gap was assessed at 8 specific points using swept-source OCT. Comparisons between the fabrication methods of PMMA crowns and different materials of conventionally made crown were done using an independent t test (α=.05).

Results: Group CAD-CAM PMMA recorded statistically significant lower total mean vertical marginal gap values (22.2 ±4.7 µm) compared with group Jet (62.6 ±2.2 µm) (P<.001). Among the conventional interim material, Group Protemp showed significantly lower values (57.6 ±5.2 µm) compared with group Jet (62.6 ±2.2 µm) (P=.02).

Conclusions: The CAD-CAM fabrication method presented smaller marginal gaps. Among the conventional interim crown materials, bis-acryl showed smaller marginal gaps than PMMA.