Effects of oxalate on dentin bond after 3-month simulated pulpal pressure

Objectives: Application of an acidic oxalate solution forms calcium oxalate within dentinal tubules and has been used to desensitize dentin and may also improve performance by reducing internal dentin wetness during bonding. The hypothesis tested was that oxalate restriction of dentinal fluid transudation when using an etch-and-rinse two-step adhesive will improve microtensile bond strength (μTBS) and reduce nanoleakage. Methods: Occlusal dentin of 60 human molars were bonded (Adper Single Bond Plus, 3M ESPE) while one-half of each tooth received either a liquid (SuperSeal, Phoenix Dental) or gel (BisBlock, Bisco) oxalate treatment after acid etching. The restored teeth were placed under pulpal pressure for 3 months before forming cylindrical dumbbell specimens for μTBS and failure pathway determination. Additional teeth were prepared and stored in a similar manner for transmission electron microscopy (TEM) examination of nanoleakage after tracer immersion. Results: The mean bond strength in the group with oxalate liquid and the control group was 27.06 ± 7.14 and 36.18 ± 9.07 MPa, respectively, and for the gel form of oxalate was 25.34 ± 13.09 and 33.09 ± 14.25 MPa, respectively. The control groups were significantly stronger than either oxalate group using t-tests (liquid p < 0.00001; gel p = 0.0032) or Weibull (liquid p = 0.0002; gel p = 0.0029) statistics. Oxalate groups also demonstrated more adhesive failure modes and nanoleakage. Conclusions: Under the conditions of this study, the application of oxalate with an etch-and-rinse two-step bonding system produced significantly lower long-term μTBS and enhanced nanoleakage.