A comparative evaluation of Accuracy between Vinyl Polyether Silicone and Addition Silicone using Monophase Impression Technique in Fixed Partial Denture

Elastomeric impression is used for making final impression in fixed partial denture and for various different purposes in Prosthodontics. Addition Silicone is commonly used material which has various advantages and some limitations when evaluating accuracy especially when it is in contact with patients saliva, blood and room temperature. Recently Vinyl Poly Ether Silicone (VPES) have been stated to overcome the limitations as they are having different properties in evaluating accuracy in patients even after delayed pouring(after 7days). However, literature lacks in prospective randomised controlled trials in this topic to define the accuracy of both materials using monophase impression technique**.** Here in this study is to compare whether the impressions made from Vinyl polyether silicone (VPES) and Addition Silicone have maintained accuracy between 1st day and 7th day .

In this parallel group randomised controlled trial 64 impressions were made in partially edentulous patients who were selected based on inclusion and exclusion criteria and were randomly assigned to two groups 1 and 2 through simple randomization. Impressions were made using group 1(VPES) and group 2(Addition Silicone) in same patient using monophase impression technique. After making final impressions, tear and voids (presence/ absence  of tear and voids) was evaluated using magnification loupes(3x).64 impressions were poured immediately as per manufacturer instructions and in same impressions cast were poured after 7 days of storage in humid lock safety pouches. 128 casts obtained on day 1 and day 7 from two groups were evaluated using Vernier Caliper (linear dimensional accuracy – AB,BC,CA that is two anteroposterior and one cross arch measurements) and also using stereomicroscope in dies of distal abutment (accuracy of dies –BL and MD that is buccolingual and mesiodistal measurements). Stereomicroscope measurements were evaluated using axio vision rel.48 software. These measurements were evaluated for both the groups by two different independent (blinded) observers who knew to operate the instrument. The observations obtained were tabulated and statistical analysis was done.

Primary objective

To compare the linear dimensional accuracy of the impressions from first day to seventh day by measuring the casts obtained from the impressions in 3 planes: AB,BC,CA- anteroposteriorly two planes and cross arch using digital vernier caliper.

To compare  the dimensional accuracy of dies of the impression from first day to seventh day by measuring the distal abutment in dies obtained from the impressions the buccolingual and mesiodistal dimensions of the dies using stereomicroscope and

Secondary objective

To compare the tear and voids (or air bubbles) of the impressions made from Vinyl polyether silicone(VPES)  and Addition Silicone  using  magnification loupes(3X).