Effects of Boric Acid and Chlorhexidine as Cavity Disinfectants on Microleakage and Microshear Bond Strength in Primary Teeth

<b>Background:</b> Cavity disinfection is commonly performed in pediatric restorative dentistry to reduce residual bacterial contamination. Although boric acid has been proposed as a potential antimicrobial agent, its effect on marginal integrity and adhesive performance in primary teeth remains unclear. This study evaluated the effects of 3% and 5% boric acid, compared with 2% chlorhexidine (CHX), on microleakage and microshear bond strength of composite restorations in primary teeth bonded with a two-step self-etch adhesive system. <b>Methods:</b> Seventy-two extracted primary second molars were allocated to four groups (n = 18) for microleakage assessment: control, 2% CHX, 3% boric acid, and 5% boric acid. Standardized Class V cavities were prepared, disinfectants were applied for 60 s, and restorations were completed using Clearfil SE Bond and resin composite. Microleakage at occlusal and gingival margins was evaluated using dye penetration. For microshear bond strength testing, 60 primary molars (n = 15 per group) were treated similarly, and shear force was applied to bonded composite microcylinders. Data were analyzed at the <i>p</i> < 0.05 significance level. <b>Results:</b> Both boric acid groups showed significantly higher occlusal and gingival microleakage than the control and CHX groups (<i>p</i> < 0.05). Gingival microleakage was greater than occlusal microleakage in the boric acid groups (<i>p</i> < 0.05). Microshear bond strength was significantly reduced in the boric acid groups compared with the control (<i>p</i> < 0.05), whereas CHX had no significant effect. Failure modes did not differ significantly. <b>Conclusions:</b> While 2% CHX did not adversely affect adhesive performance, 3% and 5% boric acid increased microleakage and reduced bond strength. Caution is advised when using boric acid with self-etch adhesive systems in primary teeth.