In situ evaluation of caries lesions inhibition at the interface tooth/restoration and in vitro evaluation of the longevity of dentin bond after dentin pretreatment with titanium tetrafluoride and self-etching adhesive systems

Abstract

The aim of this study will be evaluate the effect of a dentin pretreatment with titanium tetrafluoride 2,5% (TiF4) followed by the application of a two-step (CLE - Clearfil SE Bond/ Kuraray Medical Inc.) or one-step (SBU - Single Bond Universal/ 3M ESPE) self-etching adhesive system regarding the potential of inhibiting the development of caries lesions in enamel and dentin in situ and to investigate its influence on the longevity of dentin bond in vitro. For in situ potential of inhibiting the development of caries lesions in enamel and dentin, 64 cavities in enamel/dentin junction will be prepared in dental blocks obtained from the buccal or lingual surfaces of 32 third molars randomly distributed among treatments (n=8): TiF4 + CLE - dentin pretreatment with TiF4 followed by the application of two-step self-etching adhesive system; CLE - application of two-step self-etching adhesive system; TiF4 + SBU - dentin pretreatment with TiF4 followed by the application of one-step self-etching adhesive system; SBU - application of one-step adhesive system. Then, the cavities will be restored with composite (Filtek Z350 XT/ 3M ESPE), and one specimen of each treatment will be placed in intraoral palatal acrylic devices to be used by 16 volunteers. Each participant will use a sucrose solution 20% to be applied on the specimens, eight times a day, with a mean interval of 2 hours between each application, for a period of 21 days, to induce in situ caries. After this period, the dental blocks will be removed from the device, sectioned, embedded and planned for microhardness testing to assess the presence of demineralization around restorations. Nine measurements will be made around the margins of restorations in enamel and dentin in nine different distances and depths. For in vitro assessment of the influence of TiF4 on th longevity of dentin bond strength, 32 human third molars will be used. Flat dentin surface of each tooth will be exposed. After planning, the teeth will be separated among the groups for the application or not of the dentin pre-treatment with TiF4 and the respective adhesive systems (n = 8), as described above. A block of composite resin with 5.0 mm height and 5.0 mm width will be made on dentin. The specimens will be taken to the metallographic cutter to obtain sticks with interface área of 1mm2, approximately. The sticks will be stored in distilled water within 37º C for different storage times: 24 hours, 180 days and 360 days. It will be submitted to the microtensile bond strength test according to the storage time. One to two slices obtained from each tooth will be separated to perform scanning electron microscopy of tooth/ restoration interface. Furthermore, the surfaces of fractured specimens will be visually examined in a stereomicroscope to classify the type of fracture occurred. Statistical analyzes will be performed according to homogeneous or nonhomogeneous distribution, using parametric or nonparametric tests, respectively, adopting a significance level of 5%. (AU)