A Comparative Evaluation of Dimensional Accuracy and Surface Detail Reproduction for Polyvinyl Siloxane and Vinyl Siloxane Ether under Dry and Moist Conditions-An In-vitro Study

Introduction: The conventional impression procedure plays a major role in prosthodontics inspite of advancement in intraoral scanning devices and 3D imaging procedures. Dimensional accuracy and surface detail reproduction are important for recording an impression. Aim: The study evaluated and compared the dimensional accuracy and surface detail reproduction of Polyvinyl Siloxane (PVS) and vinyl siloxane ether impression materials when used under dry and moist conditions. Materials and Methods: An in-vitro study was conducted in the Department of Prosthodontics, Rural Dental College, Pravara Institute of Medical Sciences, Loni, Ahmednagar, Maharashtra, India, for a period of two years from October 2018 to September 2020. A total of 60 impressions were made with PVS (Group A) and vinyl siloxane ether (Group B) under dry (A1, B1) and moist (A2, B2) conditions of stainless steel dies which had lines engraved on superior surface of the die. Using a Harloc's Tool maker's microscope, dimensional accuracy was measured by comparing the width of line Y in each impression. Surface detail reproduction was evaluated by American Dental Association (ADA) specification no. 19 where it stated continuous replication of at least any two lines out of the three lines inscribed on the die. Data analysis processing was performed in the SYSTAT version 12 (made by Crane's software, Bangalore). Student's unpaired t-test and Chi-square test were performed to determine statistical difference between PVS and vinyl siloxane ether where the level of significance was set at 5% and 1%. Results: The mean dimensional change and SD values for PVS under dry condition ranged from 21.93 +/- 2.46 to 22.40 +/- 2.89 (in mm). The mean dimensional change and SD values for PVS under moist condition ranged from 22.87 +/- 3.20 to 23.33 +/- 3.42. The mean dimensional change and SD values for vinyl siloxane ether under dry condition ranged from 21.93 +/- 3.61 to 24.73 +/- 5.20. The mean dimensional change and SD values for vinyl siloxane ether under moist condition ranged from 21.93 +/- 4.48 to 22.87 +/- 4.15. No statistical difference was found under dry and moist conditions within 2 hours and after 24 hours for both the materials. Conclusion: The study revealed no significant difference between dimensional accuracy and surface detail reproduction for PVS and vinyl siloxane ether. Both the materials can reproduce the details under dry and moist conditions satisfactorily and remained dimensionally stable till 24 hours after impression making.