Abstract
Aims: To determine the effect of thermal cycling on the fitness accuracy of modified heat cured acrylic resin maxillary denture base. Materials and Methods: One hundred samples of heat cured acrylic resin maxillary denture base (Major base 2) were prepared and divided into two groups; Thermal cycling group and without thermal cycling group, each group contain; Control samples (10 samples of heat cured acrylic resin without additives) and modified samples (40 samples of heat cured acrylic resin with additives: 1% Chlorohexidine gluconate , 1.5% Nigella oil , 1.5% Thyme oil and 20% Plasticizer& caramel ). The thermal cycling employed in this study was 10 cycle per day at (5-55C°). The fitness accuracy measured after 70,300,900,1800 cycle at immersion periods of (1 week, 1,3,6 months) respectively. For fitness accuracy measurement , the surface area of the gap occurred between the posterior border of the maxillary denture base and the posterior margin of the stone cast were recorded by digital camera and measured with AutoCAD program . The collected data of fitness accuracy were subjected to the descriptive analysis(mean and standard deviation) , one way analysis of variance (ANOVA), 2 sample t-test and Duncan Multiple range test. Results: The fitness accuracy of thermal cycling group was less than that of without thermal cycling. For thermal cycling group, the highest value of fitness was achieved after 6 month of immersion for modified samples, while for control samples the highest value was achieved before immersion. Conclusion: Thermal cycling adversely affect the fitness accuracy of control and modified samples. The fitness accuracy of modified samples was better than that of control samples either with or without thermal cycling
