EVALUATION OF EFFECT OF VARIOUS COOLING PROCEDURES ON DIMENSIONAL ACCURACY AND FLEXURAL STRENGTH OF HEAT CURE DENTURE BASE RESINS: AN IN VITRO STUDY

Devshree Maibram*, Ravi Madan, Swatantra Agarwal, Sukanya Das and Ragini Pandey

ABSTRACT

Purpose:- Heat activated PMMA resins remains the most preferred material for fabrication of denture prosthesis. However, dimensional changes are unavoidable as it undergoes processing shrinkage. Denture bases undergo repeated stress during mastication over time and may crack intraorally while in use because of fatigue, therefore, a high flexural strength is required for the success of a denture. Besides the curing cycle of the denture, the cooling regimen that follows is of significance to determine the properties of heat cure denture base resin. The aim of this study is to investigate the effect of various cooling procedures on dimensional accuracy and flexural strength of heat cure denture base resins. Materials and Method:- A total of 96 samples were fabricated which were divided into two groups with 48 samples each. Group A: dimensional accuracy and Group B: flexural strength. Each group were further subdivided into three groups according to the different cooling procedures- Subgroup 1: bench cool for 30 min and then immersed in cool tap water for 15 min, Subgroup 2: cooled under running water for 20 min and Subgroup 3: flask cooled overnight in water bath. The subgroups were again divided into 2 groups each for the two materials used- conventional (TREVALON) and high impact (TREVALON HI). Dimensional accuracy was checked using an Electron microscope by measuring the distance between the grooves. Flexural strength was measured by using Universal testing machine. Results: Highest dimensional change was seen in samples cooled directly under running water for 20 min and least changes were seen in samples that were cooled overnight in water bath. Samples cooled in water bath for overnight showed highest flexural strength. Conclusion: Fast cooling should be discouraged as it has shown to result in significant dimensional change. Cooling procedures does have a significant effect on the flexural strength of heat cure denture base resin where slow cooling resulted in a higher flexural strength in comparison with the fast cooling method.

Keywords: Heat cure denture base resin, Cooling procedures, Dimensional accuracy, Flexural strength.