Hydrofluoric acid on dentin should be avoided

Hydrofluoric acid can be used for intra-oral repair of restorations. Contamination of tooth substrate with hydrofluoric acid cannot always be avoided.ObjectivesTo investigate the bonding effectiveness to hydrofluoric acid contaminated dentin by, micro-tensile bond strength testing, SEM and TEM.MethodsFor this study, 15 molar teeth were used of which dentin surfaces were subjected to five, different etching procedures. Group A, 37.5% phosphoric acid (Kerr Gel) (control group); group B, 37.5% phosphoric acid followed by 3% hydrofluoric acid (DenMat); group C, 37.5% phosphoric acid, followed by 9.6% hydrofluoric acid (Pulpdent); group D, 3% hydrofluoric acid followed by 37.5%, phosphoric acid; group E, 9.6% hydrofluoric acid followed by 37.5% phosphoric acid. After the bonding procedure (OptiBond FL, Kerr) a composite resin build-up (Clearfil AP-X, Kuraray), was made. After 1 week storage, specimens were prepared for micro-tensile bond testing, SEM- and, TEM-analysis. Data were analyzed using ANOVA and post hoc Tukey's HSD (p < 0.05).ResultsIn the control group (solely phosphoric acid), the mean μTBS was 53.4 ± 10.6 MPa, which was, significantly higher than any hydrofluoric acid prepared group (group A versus groups B–E, p < 0.001). No, significant differences in μTBS were found between the 3% and 9.6% hydrofluoric acid groups: group B versus group C (13.5 ± 5.5 MPa and 18.7 ± 4.3 MPa, respectively) or group D versus group E (19.9 ± 6.8 MPa and 20.3 ± 4.1 MPa, respectively).SignificanceDue to its adverse effect on the bond strength of composite to dentin, contact of hydrofluoric acid to dentin should be avoided.