effect of lactic acid on microleakage of class v low-shrinkage composite restorations

objectives: to assess the effect of lactic acid (la) on microleakage of silorane-based composite restorations and methacrylate-based composites with self-etch and etch-and-rinse bonding systems. materials and methods: class v cavities were prepared in 120 extracted human teeth, divided into four groups and restored as follows: 1. silorane-based composite+p90 adhesive system (p90); 2. filtek z250+se bond (z250se); 3. filtek z350+se bond (z350se) and 4. filtek z250+single bond (z250sb). half of the samples in each group were immersed in la and the other half in distilled water (dw) for seven days. degree of microleakage was determined by dye penetration. data were analyzed using kruskal wallis and mann whitney-u tests (type 1 error was considered 0.05 for primary and 0.017 for post-hoc tests). results: no significant difference was found in microleakage between la and dw groups. the difference among groups in gingival margin microleakage was significant (p<0.05). the highest degree of microleakage was seen in z250sb; which was significantly higher than z250se (dw: p=0.012 and la: p=0.002) and z350se (dw: p=0.002 and la: p=0.014). microleakage was not significantly different between z250se and z350se (dw: p=0.683 and la: p=0.533). the degree of microleakage of p90 in both media was lower than z250sb and higher than that of z250se and z350se; but these differences were not significant. conclusions: immersion in la has no effect on microleakage of class v composite restorations regardless of the type of composite and adhesive system. at gingival margins, the highest microleakage occurred in z250sb followed by p90 and self-etch groups.