Master of Science (M.S.) in Dentistry
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College of Dental Medicine
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Nova Southeastern University
Tagreed Alohali. 2016. Evaluating Conventional and Digital Impressions of Single Unit Restorations, and Conventional vs. Digital Impressions from the Laboratory Technicians’ Perspective. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, College of Dental Medicine. (113)
Objectives: To Evaluate the quality of Digital Impressions and Conventional Impressions sent to commercial dental labs and to compare Conventional impressions vs. Digital impressions from the Laboratory Technicians’ Perspective. Background: The literature lacks studies that evaluate the quality of final impressions of indirect restorations, particularly in the USA, additionally there is a direct relation between impressions accuracy and produced restoration quality, which makes it impossible to produce high quality restoration from poor impression. Methods: 259 PVS impressions were evaluated for their quality by a calibrated examiner using a specific evaluation form. Type of tray, arch and required restoration were recorded. Impressions were evaluated for the following: defects related to prepared tooth and finish line (i.e. bubbles, voids, tears, clarity of finish line, and retraction cord left in impression) also, defects in material setting and distortion. Quality of tooth preparation was not assessed. Impressions were then ranked using 3-point Likert scale: Satisfactory, Questionable, and Unsatisfactory. Similarly, 74 Digital impressions were evaluated using a specific evaluation form by a calibrated examiner. Digital system brand, arch and required restoration were recorded. Impressions were evaluated for the following: inadequate scanned data, unclear margins, improper moisture control, improper powder application, improper occlusal registration, and presence of obstructions. Impressions were ranked using a 2-point Likert scale: Satisfactory or Unsatisfactory. Data was analyzed using Chi Square and Fisher’s exact test. Furthermore, a comparison between Conventional impressions and Digital impressions sent to lab was done through a survey answered by dental lab technicians’. Results: A total of 57.9% Conventional impressions were satisfactory and a significant difference was noted between tray type groups and impression ranking c2(4, n= 257)=17.36, p < 0.001. A total of 78.4% of Digital impressions were satisfactory. Most frequent types of errors in Conventional impressions were the existence of tears, bubbles, and voids at the finish line resulting in unclear preparation margins at 36.3%, where the most frequent error in Digital impressions was inadequate scanned data at 18.9%. Regarding the Survey, 57.69% of technicians determined that number of errors in Digital impressions are less than Conventional impressions, and that the frequency of remakes in Digital impressions are also less than Conventional impressions by 63.46%. The results indicated that a total of 51.92% of the lab technicians advised for a shift to Digital impressions. The study concludes that Digital impression is a better option than Conventional impressions as a measure of its reduced errors and ease of use. Conclusion: Within the limitations of this study, when it comes to single unit restorations, dentists have to reconsider their impression taking methods and techniques.
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