Date of Award

Spring 4-29-2021

Degree Type

Thesis

Degree Name

MSOB (Master of Science in Oral Biology)

Primary Advisor

Julian Conejo

Abstract

Statement of problem: Studies on previous generations of chair-side Computer Aided Design/Computer Aided Manufacturing (CAD/CAM) systems concluded that preparation quality has an impact on marginal fit of milled restorations. However, as chair-side CAD/CAM technology improves, and newer systems and materials are released, it remains unclear if preparation quality still impacts marginal adaptation of milled restoration.

Purpose: This in vitro study evaluated the marginal adaptation of ceramic crowns fabricated with a chair-side CAD/CAM system on preparations completed with and without surface finishing to identify if finishing preparation protocols affect the marginal fit. The null hypothesis was that there was no difference in the mean marginal adaptation of ceramic restorations between the two finishing protocols.

Materials and Methods: A total of 10 maxillary right central incisor acrylic teeth were screwed into precision restorative typodont with soft gum and attached to a portable bench mount. Teeth were divided into two groups (Control group CG, Finished group FG) and prepared for all ceramic crowns with medium only/and fine grit burs under dental loupes with 4.5x magnification. The CG was prepared using the medium grit bur only, while the FG was prepared using the medium grit bur and then refined with the fine grit bur for two minutes. Preparations were scanned with an intraoral scanner and hybrid ceramic crowns were designed, milled and hand polished following the manufacturer’s recommendations. The hybrid ceramic crowns were cemented on the prepared teeth using a dual cure resin cement system. Design, milling and cementation were made by the same operator. To measure the vertical marginal gap between the margin of the crown and the finish line of the acrylic tooth, scanning electron microscope (SEM) images were made (Singh Center for Nanotechnology, University of Pennsylvania) with magnification of ×100. A total of 50 measurements were made per tooth: 25 mid-facial margin area and 25 mid-palatal margin area. The data were analyzed with Mann-Whitney Rank Sum Test to determine differences between the groups. A statistical software program was used for the analysis.

Results: The FG resulted in a significant decrease in the overall mean marginal gap of CAD/CAM all ceramic crowns compared to the CG (p<0.001).

Conclusion: Crown preparation finishing with fine grit bur has a significant impact on the marginal gap of all ceramic restorations.

Available for download on Wednesday, June 01, 2022

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