|Support type:||Scholarships in Brazil - Doctorate|
|Effective date (Start):||August 01, 2010|
|Effective date (End):||February 28, 2013|
|Field of knowledge:||Health Sciences - Dentistry - Dental Materials|
|Principal Investigator:||Regina Maria Puppin Rontani|
|Grantee:||Ana Rosa Costa Correr|
|Home Institution:||Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil|
The aim of this study is to evaluate the effect of 2% chlorhexidine digluconate (CHX) and 100% ethanol (E) on the degradation of the adhesive system bond strength to sound or artificial caries-affected dentin (microbiological challenge), considering storage time using the microtensile bond strength (µTBS) and analysis of the bonding interface (SEM). The sound teeth (n=72) will be divided into 3 groups (n=24), according to dentin substrates: sound dentin, caries affected dentin (partial removal of caries) and total removal of caries. Forty-eight non-carious human third molars (n=48) will have their occlusal enamel removed with a slow speed diamond saw, under copious water-cooling to expose a flat-surfaced sound dentin, which will be submitted to the microbiological challenge (S. mutans) for the development of artificial caries. Scaling will be used to remove total and partial caries lesion, the latter of which be submitted to a caries detector and will have part of their tissue preserved. Forthwith, the teeth will be assigned into 3 subgroups (n=8) according to surface treatment: control (untreated), and CHX and 100% ethanol application. The substrate will be etched with 35% phosphoric acid gel for 15 s, rinsed for 30 s with tap water and dried with oil/water-free air, continued of the application of the 100% ethanol for 60 s or the dentin substrates will be re-hydrated with deionized water for 60 s (control group). The application of the CHX will be 30 s before of the etched with 35% phosphoric acid gel and after of the etched for time of 60 s. After a dwell time of 30 s or 60 s, excess solution will be removed with absorbent paper, except the ethanol group. Afterwards, the dentin surfaces will be then bond with the adhesive systems Adper Single Bond 2 (3M ESPE) according to manufacturer's instructions. A 6 mm thickness block of composite resin Z350 (3M ESPE) will be bonded to the tooth and each thickness with 1,5 mm will be cured for 15 s and stored in phosphate-buffered saline (PBS, pH 7.4) at 37ºC for 7 days. After this period, the restored teeth will be longitudinally sectioned across the bonded interface to produce a series of 1.0 mm2 beams. Part of those specimens will be immediately subjected to a microtensile test. The remaining specimens were stored in PBS at 37 C for six months and one year later tested in tension under the same protocol. For analyzing the interface bonding (n=2) will be accomplished following the same adhesion protocol earlier described, divided into 3 groups according to storage time: immediate, 6 months and 1 year. The teeth will be considered as unit experimental. For the dates analysis the medium values of the shear bond of the beams each teeth will be considerate. The dates will be submitted to ANOVA and Tukey's test (± = 0.05).