Effect of Chlorhexidine on Dentin Bond Strength of Two Adhesive Systems after Storage in Different Media

The aim of this study was to evaluate the effect of 2% chlorhexidine (CHX) application during the bonding protocol on microshear bond strength of two adhesive systems, after storage in different media. Seventy-two human molars had their crowns cut in half and embedded in PVC cylinders with acrylic resin. The specimens were randomly divided into experimental groups (n=12) according to the adhesive system (Ambar and Single Bond 2), use of CHX in the bonding protocol, and time interval (24 h and 15 days) in the storage media (distilled water, mineral oil and 1% sodium hypochlorite - NaOCl). Adhesive systems were applied in accordance to manufacturers' recommendations, with or without the use of CHX, and resin composite (Z350 XT) cylinders were placed on the hybridized dentin. After photoactivation, the specimens were stored in distilled water, mineral oil and 1% NaOCl for 24 h and 15 days. Microshear bond strength was determined at a crosshead speed of 0.5 mm/min until fracture. The bond strength data were analyzed statistically by 4-way ANOVA and Tukey's test (α=5%). Use of CHX in the bonding protocol did not cause loss of bond strength in any of the evaluated situations, irrespective of time and storage medium. The storage medium had no influence on bond strength values after 15 days when the bond protocol without CHX application was used. However, the use of CHX in the protocol influenced negatively the bond strength values for Single Bond 2 after 15 days storage in distilled water and 1% NaOCl.

Resumo O objetivo deste trabalho foi avaliar o efeito da aplicação de clorexidina 2% (CHX) na resistência de união (RU) ao microcisalhamento de dois sistemas adesivos após armazenagem em diferentes meios. Setenta e duas coroas de molares humanos foram cortadas e incluídas em cilindros de PVC. Os espécimes foram distribuídos aleatoriamente nos grupos (n=12), segundo o sistema adesivo (Ambar e Single Bond 2), uso ou não de CHX e o tempo (24 h e 15 dias) e meio de armazenamento (água destilada, óleo mineral e hipoclorito de sódio 1% - NaOCl). Os sistemas adesivos foram aplicados de acordo com as recomendações do fabricante, com e sem o uso de CHX, e cilindros de resina composta (Z350 XT) foram colocados sobre a dentina já hibridizada. Após a fotoativação, os espécimes foram armazenados em um dos três meios (água destilada, óleo mineral e NaOCl a 1%) a 37 ºC por 24 h e 15 dias. RU foi determinada pelo ensaio de microcisalhamento, com velocidade de 0,5 mm/min. Os dados foram analisados por ANOVA a quatro fatores e teste de Tukey (α=5%). O uso da CHX não provocou perda de RU em nenhuma das situações avaliadas, independentemente do tempo e meio de armazenamento. Não houve influência do meio de armazenamento na RU após 15 dias quando foi utilizado o protocolo adesivo sem a aplicação de CHX. Porém, a utilização de CHX influenciou negativamente os valores de RU para o Single Bond 2 após 15 dias de armazenamento em água destilada e NaOCl a 1%.

Degree of conversion of a flowable composite light-activated through ceramics of different shades and thicknesses

Abstract The cementation of thin ceramic veneers employing fluid light-activated resin-based materials is a common procedure in the dental practice. Aim: To evaluate the influence of ceramic thickness and shade on the degree of conversion (DC) of a flowable light-activated material. Methods: flowable resin composite (Tetric N-Flow - shade A1) was light-activated through ceramic discs of two shades (IPS Classic - A1 and A3) in three thicknesses (0.5, 0.7 and 1.0 mm). For control, the resin composite was light-activated without ceramic interposition. DC was evaluated by FTIR (n=5). Data were analyzed by one-way ANOVA and Dunnett's T3 test (α=0.05). Results: Statistically significant differences between groups were observed (p<0.001). Control group (without the interposition of ceramic) showed the highest mean for DC (71.9± 1.7). Considering the interposed ceramic disc groups, the highest DC values were obtained when 0.5 and 0.7 mm A1 ceramics were used (64.6±1.2 and 64.4 5.0, respectively) and the lowest DC values were obtained for 0.7 and 1 mm A3 ceramics (61.74±0.9 and 62.0±1.9, respectively). Conclusions: No flowable resin composite group with interposing ceramics reached a DC similar to the control group.