Evaluation of Fit of a Single Crown and Three - Unit Fixed Dental Prostheses Fabricated From Conventional and Digital Impressions in Nairobi, Kenya

Abstract

Background: There’s hardly much evidence regarding the marginal fit of fixed partial denture restorations fabricated with digital impressions and computer-aided manufacturing and design technology as compared to conventional techniques. Objective: To evaluate the fit of single crown and three-unit fixed dental prostheses fabricated from digital and conventional impressions. Study design: A laboratory-based, analytical cross-sectional design. Study setting: Prime Dental Studios, a private dental laboratory in Nairobi, Kenya. Study population: Seventy-five zirconia restorations produced from a typodont model with tooth preparations for 25 single crowns and 25 three-unit fixed dental prostheses. Polyether impressions and four digital impressions – Dental Wings (DW), Carestream 3600 (CS), Medit i700 (M700) and Medit i500 (M500). Materials and methods: On the maxillary typodont model, tooth preparation for a conventional all ceramic crowns was done on the left central incisor (single unit). Another preparation was made on the left first premolar and first molar for a three-unit fixed dental prosthesis to replace a missing second premolar. In the digital impression group, the crowns were fabricated by using simulated intraoral scans and CAD/CAM technologies without definitive casts. In the conventional group, impressions were taken using polyether mono-phase impression material in a special tray. The impressions were then used to fabricate stone casts that were scanned using an intra oral scanner. The stereolithography (STL) files were exported to a computer connected to the scanner as the conventional group. The STL files were used to produce zirconia FDP frameworks with CAD-CAM. These frameworks were placed on the standard model and evaluated for marginal fit. Six measurement sites were evaluated five times for each prostheses unit, thus 90 observations for each of five impression techniques, resulting in a sample size of 450. Data analysis: Quantitative data was entered into Microsoft excel sheet. Data was cleaned and analyzed using STATA, version 16 (Stata Corp LLC College Station, Texas 77845 USA). Descriptively, marginal fit determined by marginal gap measurements were summarized as means and their corresponding standard deviations, and medians and interquartile range. Independent student t-test, One Way Analysis of Variance (ANOVA), Kruskal Wallis test followed by Tukey’s and Dunn’s post hoc tests respectively, were performed for inferential statistical analysis and hypothesis testing. A p-value of <0.05 was considered significant...