Effects of 2.5% TiF4 on microtensile bond strength: Influence of application method and degree of dentin mineralization

Abstract Objectives The aims of this study were to evaluate the effects of: (a) the application method of a 2.5% titanium tetrafluoride aqueous solution (TiF4) to dentin on the microtensile bond strength of a two-step self-etching adhesive system and (b) dentin pretreatment with 2.5% TiF4 on the microtensile bond strength of a two-step self-etching adhesive system to sound and demineralized dentin. Materials and methods Thirty-two third molars were selected to evaluate the application method for dentin pretreatment with TiF4 (Study 1). The occlusal enamel surfaces were removed, the superficial dentin flattened and the teeth divided into four groups according to the application method (n=8): NO—no dentin pretreatment with TiF4; 60A—active application of TiF4 for 60 s; 30A—active application of TiF4 for 30 s; 60P—passive application of TiF4 for 60 s. Twenty-four teeth were used to evaluate the effects of TiF4 on sound and demineralized dentin (Study 2). The occlusal enamel of the teeth was removed and flattened. They were then divided into four groups according to the degree of dentin mineralization (sound or demineralized) and the presence or absence of dentin pretreatment with TiF4 (n=6). For dentin demineralization, the teeth were immersed in demineralizing solution for 1 h and in remineralizing solution for 23 h for 3 days. Dentin pretreatment with 2.5% TiF4 was performed actively for 1 min in Study 2. For Studies 1 and 2, after application of a two-step self-etching adhesive system (Clearfil SE Bond/Kuraray), a composite resin block was built up on the tooth. The tooth-resin samples were cut to obtain specimens with a bonding area of approximately 1 mm2. Microtensile bond strength testing was performed 24 h later. The fractured test specimens were visually examined to classify the failure mode. Photomicrographs of the tooth/restoration interface were taken using scanning electron microscopy. Results For Study 1, ANOVA demonstrated no difference between application methods (p=0.784). For Study 2, ANOVA revealed no significant difference in mean bond strength values between sound and demineralized dentin (p=0.1982), or between the presence or absence of TiF4 (p=0.1789). In addition, no significant interaction between the factors (p=0.4284) was observed. The commonnest failure mode for both studies was adhesive. Hybrid layer formation was observed in all TiF4 application methods and degrees of dentin mineralization; however, the use of TiF4, independently of the application method, reduced the number and the extent of resin tags in the hybrid layer. Conclusions Microtensile bond strength of a self-etching adhesive system to dentin was not influenced by the application method of TiF4. Dentin pretreatment with TiF4 had no influence on the bond strength of the two-step self-etching adhesive system to sound or demineralized dentin, despite the changes in hybrid layer micromorphology.