A Comparison of Dimensional Accuracy of Addition Silicone of Different Consistencies with Two Different Spacer Designs - In-vitro Study

Abstract

Introduction: Dimensional accuracy of impression materials is crucial for the production of working casts in Fixed Prosthodontics. The accurate replication of tooth preparations and their arch position requires impression materials that exhibit limited distortion.

Methods: This study was conducted to comparatively evaluate the dimensional accuracy of additional silicones by comparing two different techniques and spacer designs, by measuring the linear changes in interpreparation distance. The impressions were made from a stainless steel master die simulating a three unit bridge. A total 80 die stone (type IV, Ultrarock) models were obtained from the impressions made using two different parameters. The two different parameters are Multimix and Monophasic technique and different spacer designs.

Result: The interpreparation distance of the abutments in the casts was measured using a travelling microscope. Each sample was measured thrice and the mean value was calculated. The results obtained were statistically analysed and the values fall within the clinically acceptable range.

Conclusion: The most accurate combination is multimix technique with spacer design which uses less bulk of impression material.

Keywords: Dimensional accuracy; Fixed partial denture; Polyvinyl siloxane.

[Table/Fig-1a]:

Pictorial representation of stainless steel die model depicting all the dimensions of three unit bridge Distance between abutment preparation–10.5 mm, Gingival width of molar dies–10.5 mm, Gingival width of premolar dies–7.5 mm, Occluso gingival height of the dies–9.5 mm Platform thickness–5 mm, Distance between reorientation grooves & abutments–7 mm, Angle of convergence of abutments–6 degree

[Table/Fig-1b]:

The stainless steel die model representing a three unit bridge

[Table/Fig-2a]:

Spacer 1 without covering edentulous area

[Table/Fig-2b]:

Spacer 2 covering the edentulous area

[Table/Fig-3]:

Impressions taken by multimix technique

[Table/Fig-4]:

Impressions taken by monophasic technique

[Table/Fig-5,6]:

The casts retrieved by both the techniques and spacer designs

[Table/Fig-7]:

Mean of the interpreparation distance between two impression techniques i.e. multimix and monophasic technique (N=40)

[Table/Fig-8]:

Mean of the interpreparation distance between two spacer designs i.e. spacer 1 and spacer 2 (N=40)