Introduction: Heat-polymerized acrylic resin is the most basic denture material used. One of the mechanical properties of an acrylic resin is its transverse strength. The transverse strength test provides an overview of the material's durability in accepting the load at mastication. Consumption of tea, especially black tea in the world placed the second most consumed. The purpose of this study was to determine the effect of black tea on the transverse strength of heat-polymerized acrylic resin. Methods: This research was an experimental laboratory with 24 samples of heat-polymerized acrylic resin plate with the size of 65x10x2.5 mm. The sample was divided into 6 groups, each consisted of 4 samples. The first, second, and the third groups were immersed in aquadest for consecutively 1, 4, and 20 days. The fourth, fifth, and sixth groups were immersed in the black tea for consecutively 1, 4, and 20 days. The transverse strength was tested using the three-point bending method with the Universal Testing Machine. The results of the transverse strength measurement were then analyzed statistically by the One-way ANOVA test and Holm's sequential Bonferroni posthoc test as an advanced test. Results: The results of the statistical test showed that p<0.05 (p=0.000) which means that the six groups have a significant difference in the average value of the transverse strength. Conclusion: The conclusion of this research was the black tea immersion duration was affecting the transverse strength differences of the heatpolymerized acrylic resin.

Heat-polymerized  acrylic  resins  is  the  most  used  denture  base  material  in  prosthodontics.  One  of  mechanical properties of acrylic resins is transverse strength. It represents the masticatory pressure that is applied to denture base. Black tea is the second largest consumed beverage in the world. The aim of this study was to investigate the effect of black tea beverage on transverse strength of heat-polymerized acrylic resins. A total of 24 heat-polymerized acrylic resin plates (65×10×2,5 mm) were immersed in black tea beverage for 1, 4, and 20 days as treatment group and in aquadest for 1, 4, and 20 days as control group. The transverse strength of  acrylic samples were measured by three–point bending test by universal testing machine. Data were statistically analyzed using Independent t test. The transverse strength values of acrylic resin immersed in black tea beverage had no significant differences to the transverse strength values of acrylic resin immersed in aquadest with similar immersion time (p>0,05). There was no effect of black tea beverage on transverse strength of heat-polymerized acrylic resins. Immersion time decrease the transverse strength of heat-polymerized acrylic resins due to water sorption. Keywords: Heat-polymerized acrylic resins, black tea, transverse strength