Factors that influence the quality of final impressions for fixed dental prostheses in Nairobi, Kenya

Abstract

Background:Good quality dental impressions free of air bubbles, voids, steps, drags, streaks and tears are a pre-requisite for the fabrication of well-fitting fixed dental prostheses (FDP). The quality of impressions is dependent on clinician and material factors.Aim:To evaluate factors that influence the quality of final impressions for FDP in Nairobi, Kenya. Methods:In this cross-sectional study, 234 impressions received by five dental laboratories were analyzed. The study collected information on the type of tray, impression material, technique, type of prostheses, and clinically detectable errors, including voids, inadequate material at margins, tears, steps, drags, and streaks. Impression quality was the outcome assessed as good, fair, or poor by two investigators. The independent variables influencing impression quality included clinician specialty, experience, impression material, technique, and tray type.Results: Inter-rater agreement was 96.8% (p<0.001). Clinician experience ranged between 1-45yrs, median 13.5yrs and mean 8.39±11.96yrs. The majority were GPs, 80.8% while restorative dentists were 11.5% and other specialists, 7.7%. Most impressions were non-aqueouselastomers, 97.9% employing dual-viscosity technique, 75.6%. Impression trays included stock metal, 60.3%, stock plastic, 34.2%, and custom, 5.5%. Impression quality was good, 24.8%, fair, 37.2% or poor, 38.0%. Cumulatively, 74.5% impressions hadbubbles/voids, 53.0% tears and 43.2% poor margins. Clarity of margins was associated with clinician specialty, (Fisher’s exact=9.372, p=0.047), and impression technique with impression quality, (Pearson’s χ2 = 6.385, p=0.041). Compared to restorative specialists, estimated odds of other specialists producing poor margins was 5.71, 95%CI 1.55,21.06, Wald χ2=5.24, p=0.009 while for GPs, the estimated odds was 2.19, 95%CI 0.88, 5.43, Wald χ2 = 2.86, p=0.09. Compared to dual viscosity, estimated odds of monophase giving a poor-quality impression was 1.52, 95%CI 0.83,2.78, Wald χ2 = 1.52, p=0.18.Conclusion:Most impressions were good or fair hence acceptable. Quality of impressions was influenced by clinician specialty and impression technique

Marginal Fit of Single-Crown and Three-unit Fixed Dental Prostheses Fabricated from Digital and Conventional Impressions: A cross-sectional study

“…Polyvinyl siloxane and polyether are presently the recommended conventional impression materials for prosthodontic treatment due to their accuracy, ne detail reproduction and dimensional stability. Polyether has the additional advantage of being hydrophilic and hence ideal in the moist oral environment [11,26,27]. The acceptable marginal gap measurements of restorations produced from polyether in this study con rmed the suitability of polyether as a control for comparison with newer digital systems.…”

“…One of the main factors affecting the longevity of a dental restoration is marginal adaptation or how well it ts around the tooth [10,11]. Improperly tting FDPs can result in plaque accumulation, microleakage and subsequent endodontic pathology.…”

“…Improperly tting FDPs can result in plaque accumulation, microleakage and subsequent endodontic pathology. The marginal t of a restoration is determined by various factors, such as the fabrication technique used, the number of units in the substructure, the tooth location and quality of preparation, the rigidity of the impression material, and the type and thickness of the luting agent [1,11]. An accurate impression is fundamental to a successful outcome in prosthodontics.…”

“…The accuracy of the impression affects the accuracy of the working cast, and an accurate working cast is essential for the fabrication of a clinically acceptable prosthesis. Impression and cast accuracy are in uenced by the selection of impression materials, impression technique, operator skill, attention given to detail, and production process of the working cast [6,11]. The goal of taking impressions is to achieve an accurate three-dimensional reproduction of the abutment tooth surface in relation to other oral structures [11,12].…”

“…Impression and cast accuracy are in uenced by the selection of impression materials, impression technique, operator skill, attention given to detail, and production process of the working cast [6,11]. The goal of taking impressions is to achieve an accurate three-dimensional reproduction of the abutment tooth surface in relation to other oral structures [11,12]. Impressions for crowns and xed partial dentures present unique challenges to restorative dentists, and errors can be introduced in many ways.…”