Effect of flash-free polymeric adhesive on enamel surface after orthodontic bracket debonding under simulated cariogenic and gastric acid conditions

Introduction Enamel demineralization during orthodontic treatment may occur due to changes in the oral environments. This study aimed to assess the influence of flash-free polymeric adhesive systems on debonding behavior and subsurface enamel hardness under erosive and cariogenic conditions, compared with conventional orthodontic adhesives. Methods Sixty premolars ( n = 60) were randomly divided into two groups ( n = 30 each): Group C, consisting of uncoated brackets, and Group F, comprising flash-free adhesive precoated brackets. Each group was further subdivided into three subgroups ( n = 10) based on the storage medium used. In the artificial saliva subgroup (control group), specimens were stored in artificial saliva for 24 h. In the artificial cariogenic subgroup, specimens were alternately exposed to an artificial cariogenic solution and artificial saliva for 28 days. In the gastric acid subgroup, specimens were subjected to simulated gastric acid (pH = 1.2) by immersion for 2 min, six times daily, over a period of 9 days. All specimens underwent adhesive remnant index (ARI) testing and cross-sectional microhardness evaluation. Two-way ANOVA and Tukey's test were conducted to analyze cross-sectional microhardness. The chi-square test was used to analyze ARI scores. Results Across all storage media, conventional brackets demonstrated higher frequencies of ARI score 1, whereas flash-free brackets consistently showed higher frequencies of ARI score 2. Across all storage media, the flash-free bracket system exhibited significantly higher overall microhardness (323.8 HV) compared with the conventional adhesive system (293.06 HV) ( p < 0.05), indicating superior enamel protection under all tested conditions. Conclusions Under cariogenic and erosive conditions, flash-free brackets demonstrated higher enamel cross-sectional microhardness and distinct adhesive remnant patterns. These findings suggest that flash-free polymeric adhesive systems may offer enhanced enamel protection during orthodontic treatment, particularly in patients exposed to cariogenic or gastric acid challenges.