Influência de estratégias de biomodificação dentinária nas propriedades físico-químicas de sistemas adesivos

Abstract

Provide greater durability to the bonding procedures when performed on the dentin is considered a challenge. Therefore, the use of bioactive agents may be a promising strategy to preserve the hybrid layer . Thus, this thesis consisted of five chapters that aimed, respectively : 1) To evaluate the effect of sodium fluoride on the resin - dentin bond strength of a self - etch adhesive after thermal cycles ; 2) T o evaluate the effectiveness of dentin biomodification with epigallocatechin - 3 - gallate (EGCG) on the resin - dentin bonds overtime ; 3) T o evaluate the influence of EGCG incorporation on the physicochemical properties of a methacrylate - based dental adhesive ; 4) To develop and characterize of poly (lactide - co - glycolide) acid (PLGA) micropartciles for controlled release of epigallocatechin - 3 - galate (EGCG), using two types of PLGA; 5) To evaluate the EGCG - load PLGA microparticules incorporation on the physicochemical properties of a two - step etch - and - rinse adhesive s ystem, and the release rate of EGCG. As methodolog ical approaches were perform ed 5 in vitro studies. In the Article 1, dentin surface of 18 teeth were treated with distilled water, 2% chlorhexidine digluconate solution (CHX) or 1.23% sodium fluoride solution (NaF). Bonded sticks were obtained and submitted to bond strength test (μTB S), after 24 h and 60.000 thermal cycles . In Article 2, dentin surface of 27 teeth were treated with distilled water , or EGCG, or CHX. Bonded sticks were obtained and submitted to bond strength test (μTBS), after 24 h, 6 and 12 months of storage. To Articl e 3, EGCG was added to one - step self - etch adhesive , except in control group, to obtain concentrations of 0.01% w/w and 0.1% w/w of EGCG - doped adhesives . Then, water sorption (WS) , solubility (SL) , degree of conversion (DC) and flexural strength (FS) tests were performed. To Article 4, microparticles were developed from a spray drying technique and then were determined size and particle morphology, yield , effic a cy of encapsulation , drug loading and and EGCG release. Finally, in Article 5 , beyond the concentrations of 0.01% w/w and 0.1% w/w of EGCG - doped adhesives , were also incorporated EGCG - load polymeric microparticles at 1%. Then, DC, FS, elastic modulus (E), WS, SL, DC, μTBS and EGCG release. D ata were submitted to ANOVA and any statistical differ ences were analyzed by Holm - Sidak test. The significance level was 5%. The results showed that the NaF maintained bond strength after thermocycling (p = 0.336) (Chapter 1). G roups treated with EGCG and CHX did not affect the bond strength after 24 h (p> 0. 05), and maintained the bond strength after 6 and 12 months (p <0.05) (Chapter 2). There was no statistical difference between the WS, GC and RF values when the groups were compared (p> 0.05). However, the incorporation of EGCG reduced SL values (p <0.05) (Chapter 3). There was no significant difference in the DC, E, WS SL and μTBS values among all groups (p>0.05). FS values were significantly increased by incorporating polymer microparticles loaded with EGCG at 1% (p<0.05). The microparticles made from PLG A 50:50 and 75:25 PLGA showed a pattern of pulsatile release (Chapter 4). Polymeric microparticles had the highest EGCG release rates, when co mpared with other groups (p<0.05) (Chapter 5 ). Therefore, it is conclu ded that the dentin biomodification strategi es besides not impair the physical properties of the adhesive systems may also maintain more stable bonding interface over time.