Accuracy of Elastomeric Impression Made with Standard and Dual Arch Tray: An In-vitro Study

Abstract

Introduction: The dual-arch impression techniques utilise special stock impression trays of various designs. These trays are made of plastic or metal with fabric or mesh material placed across the occlusal surfaces of the teeth connecting their buccal and lingual flanges. These special trays register the impression of the opposing segments of the dentition. The dual arch impression technique is used in dentistry effectively since many decades but there is very little evidence published regarding the effect of different tray design on the accuracy of impression. Aim: To evaluate the accuracy of inter-abutment distance in dies obtained from different dual-arch trays and with those obtained from stock metal trays. Materials and Methods: This in-vitro study was carried out in the Department of Prosthodontics, M.M. College Of Dental Sciences and Research, Mullana, Haryana, India between June 2016 to November 2017. A total of 70 elastomeric impression using heavy and light body addition silicone impression material were made, of the prepared typodont teeth of right mandibular first premolar and first molar for thee- unit fixed partial denture. impressions were grouped into four groups, based on the type of tray used i.e. Group A consisted of impressions obtained from plastic dual-arch trays (n=20), Group B- plastic reinforced with metal dual-arch trays (n=20), Group C- metal dual-arch trays (n=20) and Group D-full stock metal trays (n=10). Group A, B and C were further divided into Subgroup I (working side poured first) (n=10) and Subgroup II (non-working side poured first) (n=10) depending upon the sequence of pouring. The measurements were obtained using travelling microscope and statistical analysis was done using one-way Analysis of Variance (ANOVA) test which was then followed by a post-hoc test. Results: The inter-abutment distance showed a decreased value in all the groups when compared to the master model (p-value >0.05). Percentage decrease in inter-abutment distance was between 0.006% - 0.48%. The results indicated statistical insignificant difference when full arch metal stock tray impression is compared to all dual arch trays impression. There was insignificant difference between the inter-abutment distance obtained using dual arch trays which were poured with working or non working side first. Conclusion: The impressions obtained with both dual arch trays and stock tray, produced dies with distortion in a clinically relevant range. Thus, dual arch trays can be recommended for making impressions of short span fixed partial dentures, and can be considered to be an alternative to the conventional method.