Comparative evaluation of linear dimensional accuracy of impressions made with different elastomeric impression materials (Polyether and Polyvinyl siloxane) in angulated and parallel implants-An invitro study

To date no technique has been proven to guarantee a completely passive fit of implant supported prosthesis framework. Several clinical variables such as angulation of implants, impression material and technique used may affect the precision of impressions. Hence, this study is designed to evaluate and compare the dimensional accuracy of the resultant casts made from open tray implant level impressions with two different impression materials (polyvinyl siloxane and polyether) in parallel and angulated implants. The study consisted of two control groups; master model –1with parallel implants and master model –2 with angulated implants. From master model 1and master model 2, total 40 implant level open tray impressions were made using PVS and polyether impression material and impressions were poured to obtain 40 study casts. The resultant casts were divided into 4 groups (10 casts in each group), according to the impression material used (PVS or Polyether) and implant’s orientation (parallel or angulated) in the casts. All casts were evaluated for the positional accuracy of the implant by using four reference distances with the help of a profile projector. These measurements were compared to the measurements calculated on the master model, which served as a control. The variations of the mean distance values with respective control values within a group were analyzed with one samples’ t’ test at 0.05 significance level. Further the mean distance variations between the groups were analyzed with independent samples ‘t’ test to evaluate group mean variations.The impressions made in the presence of angulated implants were significantly less accurate than the ones made with parallel implants. Regarding impression material the tested polyether resulted advantageous over polivinylsiloxane impression material in terms of recording positional accuracy of implants.