Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 22 0 2025 12 09 5373 5373 Zahra Jowkar Jowkar . Oral and Dental Disease Research Center, Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Fereshteh Shafiei Oral and Dental Disease Research Center, Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Zahra Lotfhaghpanah Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Zahra Sajedianfard Department of Operative Dentistry, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran Seyed Ahmadreza Hamidi Department of Oral and Maxillofacial Surgery, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran 2024 10 02 2025 11 12 Objectives: The objective of this study was to investigate how various surface treatments impact the microshear bond strength (μSBS) of a self-adhesive bulk-fill composite resin to cut and uncut enamel. Materials and Methods: Eighty sound human third molars were collected in this in vitro study. Forty were prepared to create cut enamel surfaces, and 40 were left uncut. Each group was randomly divided into four subgroups (n=10) according to the type of surface treatment: no treatment (control), 18% ethylenediaminetetraacetic acid (EDTA), All-Bond Universal adhesive in etch-and-rinse (E&R) mode, and All-Bond Universal adhesive in self-etch (SE) mode. Surefil One self-adhesive bulk-fill composite resin was bonded to enamel, and μSBS was measured after 24 hours. Data were analyzed by two-way ANOVA and Tukey’s HSD post-hoc test (alpha=0.05). Results: Two-way ANOVA showed significant main effects of enamel preparation (P<0.001) and surface pretreatment (P<0.001), as well as their significant interaction effect (P=0.005) on μSBS. Cut enamel exhibited a higher mean μSBS (7.12±2.66MPa) than uncut enamel (5.88±2.70MPa; P=0.019). Universal adhesive application in E&R mode yielded the highest μSBS, followed by the SE mode; whereas, EDTA and no-treatment groups showed the lowest μSBS values. Conclusion: Cut enamel samples exhibited a greater μSBS in comparison to uncut samples. The highest μSBS values were observed when both cut and uncut enamel surfaces received pretreatment with a universal adhesive applied in E&R mode. https://fid.tums.ac.ir/index.php/fid/article/view/5373 https://fid.tums.ac.ir/index.php/fid/article/download/5373/2189