Titanium tetrafluoride incorporated into a two-step self-etching adhesive system: physico-mechanical characterization and bonding stability

Objectives: To evaluate the influence of TiF4 incorporated into the primer (P) or bond (B) of a self-etching adhesive system on long-term dentin bonding, and evaluate the physico-mechanical properties of TiF4-containing adhesives. Methods: Dentin surfaces received the following treatments (n = 8): CL (Clearfil SE Bond); TiF4CL (dentin pretreatment with TiF4 aqueous solution + CL); TiF4P (TiF4 incorporated into the P); TiF4B (TiF4 incorporated into the B). Microtensile bond strength (mu TBS) and failure mode evaluations were performed after 24 h, 6 months and one year, respectively. Degree of conversion (DC) and flexural strength (FS) were evaluated to determine whether TiF4 influenced adhesive properties. Particle size (PS), polydispersity index (PI) and zeta potential (ZP) of TiF4-containing adhesives were measured using dynamic light scattering. Two-way ANOVA for repeated measures was applied to mu TBS data, and one-way ANOVA and Tukey tests to DC and FS results. Results: There was no difference in mu TBS among the groups (p = 0.818) regardless of time; the TBS in each group was not significantly affected over time (p = 0.061). TiF4P and TiF4B significantly affected FS (p = 0.004). The DC for TiF4P was not significantly different from that of CL, and higher than that of TiF4B. Lower average particle size was observed for TiF4P at baseline. TiF4 aqueous solution showed a tendency to agglomerate. Conclusions: TiF4-containing adhesives did not influence mu TBS or failure mode to dentin over time, although FS and DC were affected, especially when TiF4 was incorporated into the B. TiF4P presented excellent stability over time.