Effect of oxalate under adhesive restorations. An “in vivo” study

Objective: To test if the application of oxalate after demineralization of dentin and before the application of adhesive system does not decrease the bond strength. Methods: Fifteen human premolars were used in this study. The vestibular surface was ground flat to remove the enamel and expose middle dentin. The teeth were randomly assigned in tree treatment sequences: Group 1 (control)– 37% Phosphoric acid gel + Single-Bond (3M ESPE) adhesive system. Group 2 – 37% Phosphoric acid gel + 3% Potassium oxalate gel (Oxa-Gel) and Single-Bond (3M ESPE) adhesive system. Group 3 – 37% Phosphoric acid gel + Experimental 3% Potassium oxalate gel and Single-Bond (3M ESPE) adhesive system. After the bonding procedures, resin composite (Z-250 3M ESPE) crowns were built-up over the adhesive. The teeth were extracted immediately and stored in water at 37oC for 24 h. Each tooth was then vertically sectioned with an Isomet saw through the composite crowns and the dentin at 1-mm increments to produce a series of a 1-mm-thick slabs. Each slab was then sectioned vertically into 1x1x8 mm sticks with an Isomet saw. Thus, all specimens were subjected to micro-tensile bond testing. Approximately twenty sticks were tested for group. Bond strength data were subjected to one-way ANOVA and Tukey test at the 95% level of confidence. Results: Group 1 (control) showed the highest bond strength (23.2 Mpa) compared with others groups (group 2: 23.1 Mpa and group 3: 18.6 MPa). There was no statistical difference between the groups. When visually inspected, most specimens showed interfacial adhesive failure. This was confirmed by light microscopic examination (40X). Conclusion: The application of oxalate after demineralization of dentin and before the application of adhesive system not decreased the bond strength.