Evaluation of Effect of Different Cooling Methods on Denture Base Adaptation of Rapid Heat Cured Acrylic Using a Three Dimensional Superimposition Technique

Abstract

Background: There are several factors affecting the adaptability of prosthesis. These factors include nature of the acrylic resin used in denture fabrication, type of the curing cycle used and the process of water uptake. Type of procedure employed for cooling of the flasks during the acrylization process is another vital factor in the preservation of precision of dimensions of the dentures. Prolonged cooling helps in reducing the lingering interior stress in the flasks developed due to heat activated process. As a result there is minimum damage to the denture while deflasking.

Aim: This study was conducted with an ambition to analyse the effect of various methods of cooling over the adaptation of denture base of 2 fast setting heat activated polymethyl methacrylate denture base materials easily available in market using three dimensional superimposition technique. 

Materials and Methods: Sixty stone models were prepared. Type IV dental stone was used for pouring of the duplication mould. These sixty study models were divided into five categories X1, X2, X3, X4, X5 with each category consisting of 12 study models according to the method of cooling and material used. A pattern of wax was prepared througout the cast of reference. Then there was superimposition of STL file of every intaglio surface of the denture base with the corresponding STL file of the master cast. This was carried out to analyse the degree of of adaptation of denture base in each specimen.  Four anatomical landmarks were choosen for matching in the superimposition of denture base scanned image over the master cast scanned image

Results: Broad area of green colour in the palate was observed in the specimens of X1, X2 and X3 categories. Specimens belonging to X4 and X5 categories showed greater red coloured areas at the location of post dam area and palate area. On the basis of statistical analysis it was found that there were no statistical significant differences between group X1 and X2 specimens. It reflected that there was similarity in the accuracy of both X1 specimens and X2 specimens. It was also observed that differences were statistically significant between specimens of X2 category and X3 category. Besides there was a significant difference between X2 and X5 specimens.

Conclusion: From these results it was inferred that specimens which underwent bench cooling showed better dimensional accuracy in comparison with the rapidly cooling techniques used in the study.