Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 19 0 2022 08 10 4152 4152 Parnian Alizadeh Oskoee Dental and Periodontal Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Siavash Savadi Oskoee Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran Fatemeh Pournaghi-Azar Department of Operative Dentistry, Faculty of Dentistry, Tabriz University of Medical Sciences, Tabriz, Iran Sana Dibazar Department of Operative Dentistry, Faculty of Dentistry, Tabriz university of Medical Sciences, Tabriz, Iran Mehdi Esmaeili Department of Orthodontics, Faculty of Dentistry, Tabriz Azad University of Medical Sciences, Tabriz, Iran 2021 08 02 2022 03 16 Objectives: The present study aimed to investigate the effect of preheating on the color stability and surface roughness of a silorane-based composite resin. Materials and Methods: A total of 44 Filtek P90 composite resin disks, (10mm×1mm), were fabricated using plastic molds and were divided into two groups. In group 2, the composite resin syringes were placed in a thermostatically controlled water bath at 55‒60°C before preparing the disks. After polishing the samples with silicon carbide papers, they were stored in distilled water for 48 hours. Roughness and color parameters were then measured in two stages: immediately after retrieval from distilled water and after 40 days of storage in tea solution. Finally, the differences in roughness and color parameters were recorded. Independent sample t-test and regression analysis were used at a significance level of P<0.05. Results: Based on the findings of the present study, there was no significant difference among the mean ∆E values (P=0.4); however, a significant difference in mean surface roughness (P=0.01) was found between the two groups. Regression analysis showed a significant relationship between the study groups in terms of surface roughness and ΔE values​ (preheated: r2 = 0.73; non-preheated: r2= 0.76). Conclusion: Filtek P90 silorane-base composite showed ΔE>3.3 and surface roughness above 0.2µ under preheated and non-preheated conditions and discoloration increased following preheating.   https://fid.tums.ac.ir/index.php/fid/article/view/4152