Effects of curing modes on depth of cure and microtensile bond strength of bulk fill composites to dentin

Objectives: To compare the microtensile bond strength (µTBS) and depth of cure (DOC) of bulk-fill composites cured by monowave (MW) and polywave (PW) LED units using different curing times. Methodology: Three composites were tested: Tetric EvoCeram Bulk Fill (TBF), Filtek Bulk Fill (FBF), and Tetric EvoCeram (T; control). Flat dentin surfaces treated with adhesive (AdheSE Universal®, Ivoclar Vivadent) were bonded with 4 mm cylindrical samples of each bulk-fill composite material (n=6) and cured with monowave (Satelec) or polywave (Bluephase Style) curing units for 10 or 20 seconds. After 24 hours, teeth were sectioned into individual 0.9 mm2 beams and tested for µTBS. Failure modes were analysed. Moreover, the DOC scrape test (IOS 4090) was completed (n=5) following the same curing protocols. Two-way ANOVA (a=0.05) was performed, isolating light-curing units. Results: For samples cured with the MW light-curing unit, no significant effects were observed in the µTBS results between any of the resin composite brands and the curing times. Conversely, when resins were cured with a PW light unit, a significant effect was observed for TBF resin. In general, bulk-fill composites presented greater DOC and longer curing time resulted in higher DOC for all composites. Conclusion: The µTBS of the composites to dentin was not affected by the curing mode of the resins, except for TBF cured with PW light unit. Bulk-fill composites exhibit greater DOC than conventional resin-based composites

Effect of an additional hydrophilic versus hydrophobic coat on the quality of dentinal sealing provided by two-step etchand-rinse adhesives

OBJECTIVE: To test the hypothesis that the quality of the dentinal sealing provided by two-step etch-and-rinse adhesives cannot be altered by the addition of an extra layer of the respective adhesive or the application of a more hydrophobic, non-solvated resin. MATERIAL AND METHODS: full-crown preparations were acid-etched with phosphoric acid for 15 s and bonded with Adper Single Bond (3M ESPE), Excite DSC (Ivoclar/Vivadent) or Prime & Bond NT (Dentsply). The adhesives were used according to the manufacturers' instructions (control groups) or after application to dentin they were a) covered with an extra coat of each respective system or b) coated with a non-solvated bonding agent (Adper Scotchbond Multi-Purpose Adhesive, 3M ESPE). Fluid flow rate was measured before and after dentin surfaces were acid-etched and bonded with adhesives. RESULTS: None of the adhesives or experimental treatments was capable to block completely the fluid transudation across the treated dentin. Application of an extra coat of the adhesive did not reduce the fluid flow rate of adhesive-bonded dentin (p>0.05). Conversely, the application of a more hydrophobic non-solvated resin resulted in significant reductions in the fluid flow rate (p<0.05) for all tested adhesives. CONCLUSIONS: The quality of the dentinal sealing provided by etch-and-rinse adhesives can be significantly improved by the application of a more hydrophobic, non-solvated bonding agent

Evaluation of the adjunctive use of chlorhexidine and ethanol on the durability of resin dentin bonds

A degradação do adesivo e colágeno é considerada uma das principais causas de falhas nos processos adesivos à dentina. A completa infiltração de resinas hidrofóbas facilitada pelo etanol, associada à presença de inibidores de metaloproteinases presentes na dentina, poderia construir a união ideal, resistente à hidrólise e atividades enzimáticas. Este estudo examinou os benefícios do uso combinado de clorexidina como inibidor de metaloproteinases e etanol, na durabilidade de uniões resina-dentina. Foram utilizados 48 terceiros molares hígidos para obter superfícies planas de dentina que foram condicionadas com ácido fosfórico a 32% por 15 segundos, lavadas por 30 segundos, e secas com papel absorvente. Imediatamente após, uma das seguintes soluções foi aplicada por 30 segundos: água (A); etanol (E); solução aquosa de clorexidina a 1% (CA); solução alcoólica de clorexidina a 1% (CE). O excesso foi removido com papel absorvente e um dos adesivos, All Bond 3 (AB3) ou Excite (EX), foi aplicado à superfície sob agitação por 15 segundos, seguido por um jato de ar por igual tempo, e fotoativado por 20 segundos. Uma coroa de aproximadamente 4 mm foi construída incrementalmente em resina composta e os dentes foram armazenados por 24 horas em água destilada à 370C. A seguir foram cortados em paralelogramos para o teste de microtração. Um terço dos corpos de prova foi ensaiado imediatamente e os demais permaneceram armazenados por 6 ou 15 meses. Os efeitos dos tratamentos e períodos de armazenagem foram analisados para cada adesivo. Os resultados não demonstraram interação entre os fatores para ambos os adesivos. AB3 foi significantemente afetado pela armazenagem, mas não pelos tratamentos. EX foi significantemente afetado pelo tratamento, mas não pela armazenagem. Concluiu-se que o uso de clorexidina/etanol não melhorou a estabilidade da união após 15 meses. AB3 quando tratado com A ou CA, e EX com todos os tratamentos não foram afetados pela armazenagem.Both adhesive and collagen degradation have been regarded as major causes of resin-dentin bonds failures over time. Complete infiltration of hydrophobic resins facilitated by ethanol, and the presence of MMPs inhibitors within the hybrid layer would build the ideal interface, resistant to hydrolysis and enzymatic activities. This study examined the benefits of the adjunctive use of chlorhexidine and ethanol on the durability of resin dentin bonds. Forty-eight flat dentin surfaces were etched (32% phosphoric acid), rinsed (30s) and blot-dried with absorbent paper. The surfaces were re-wetted with either water (Water); 1% chlorhexidine diacetate in water (CHX/Water); 100% ethanol (Ethanol); and 1% chlorhexidine diacetate in ethanol (CHX/Ethanol) solutions for 30s. They were then bonded with All Bond 3 (AB3, Bisco) or Excite (EX, Ivoclar- Vivadent) using a smooth, continuous rubbing application (15s), followed by 15s gentle air dry. The adhesives were light-cured (20s) and resin build-ups constructed incrementally for the microtensile method. Bonded beams were obtained and tested after 24-hours, 6-months, and 15- months water storage at 370C. Effects of treatment and testing periods were analyzed (ANOVA, Holm-Sidak, p<0.05) for each adhesive. There were no interactions between factors for both adhesives. AB3 was significantly affected by storage, but not by treatments. Excite was significantly affected by treatments, but not by storage. Adjunctive use of ethanol/chlorhexidine did not improve bond stability after 15 months. AB3 treated either with ethanol or CHX/ethanol resulted in reduced bond strengths after 15 months. AB3 treated with water or CHX/water and all treatments for Excite were not affected by storage

Effect of conditioning solutions containing ferric chloride on dentin bond strength and collagen degradation

To investigate the effects of conditioning solutions containing ferric chloride (FeCl3) on resin–dentin bond strength; on protection of dentin collagen against enzymatic degradation and on cathepsin-K (CT-K) activity. Conditioning solutions were prepared combining citric acid (CA) and anhydrous ferric chloride (FeCl3) in different concentrations. The solutions were applied to etch flat dentin surfaces followed by bonding with adhesive resin. Phosphoric acid (PA) gel etchant was used as control. The microtensile bond strength (μTBS) was tested after 24 h of storage in water and after 9 months of storage in phosphate buffer saline. Dentin slabs were demineralized in 0.5 M EDTA, pre-treated or not with FeCl3 and incubated with CT-K. The collagenase activity on dentin collagen matrix was examined and characterized by SEM. Additional demineralized dentin slabs were treated with the conditioning solutions, and the amount of Fe bound to collagen was determined by EDX. The activity of CT-K in the presence of FeCl3 was monitored fluorimetrically. Data were analyzed by ANOVA followed by post-hoc tests as required (α = 5%). Slightly higher bond strengths were obtained when dentin was conditioned with 5% CA/0.6% FeCl3 and 5% CA–1.8%FeCl3 regardless of storage time. Bond strengths reduced significantly for all tested conditioners after 9 months of storage. Treating dentin with 1.8% FeCl3 was effective to preserve the structure of collagen against CT-K. EDX analysis revealed binding of Fe-ions to dentin collagen after 15 s immersion of demineralized dentin slabs into FeCl3 solutions. FeCl3 at concentration of 0.08% was able to suppress CT-K activity. This study shows that FeCl3 binds to collagen and offers protection against Cat-K degradation. Mixed solutions of CA and FeCl3 may be used as alternative to PA to etch dentin in resin–dentin bonding with the benefits of preventing collagen degradation.331010931102CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES30217-2014-01777-2014; 99999010