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%.

Effect of water storage and hydrophobic adhesive layer application on the bond strength of allll-in-one adhesives

Introduction: To prevent the rate of water absorption and degradation of exposed collagen and the resin matrix on the hybrid layers, the use of an additional layer of hydrophobic resin on all-in-one adhesives is one of the approaches to improve the bond strength and infiltration of monomers in demineralized dentin. Objectives: To compare the microshear bond strength of different self-etching adhesive systems, and to evaluate the effect of the application of a hydrophobic adhesive layer on all-in-one adhesive systems after a storage period of 48 h and 30 days in distilled water at 37oC. Material and methods: Bovine incisor crowns were polished to expose flat dentin surfaces. The crowns were randomly distributed into 14 groups (n = 12) according to the adhesive system [Clearfil SE Bond (CSEB), AdheSE (ASE), Adper Scotchbond SE (SSE), Adper Easy Bond (EB), and Go! (GO)], and storage time. In two groups (indicated as GO+B and EB+B), a layer of a hydrophobic adhesive was applied on all-in-one adhesive systems. After 48h and 30 days of storage in distilled water at 37oC, microshear bond strength was determined. The data were statistically analyzed by ANOVA and Tukey's test (α = 5%). Results: After 48h, EB, EB+B, CSEB, and GO+B showed higher bond strength values. The application of a hydrophobic layer did not influence EB and increased GO bond strength values. After 30 days, CSEB, SSE, and EB+B showed the highest bond strength values. Comparing groups of all-in-one adhesives with and without a hydrophobic adhesive-resin layer, the bond strength values showed no significant difference. Conclusion: The application of a hydrophobic adhesive-resin layer increased bond strength values only at 48h. With respect to bond degradation over time, only EB showed a statistically significant decrease of bond strength after 30 days.

Comparative evaluation of the accuracy of pick up transfer impressions performed with two different types of trays

Introduction: The success of implant-supported prostheses is related to the passive union between the prostheses’ connections and the implants, so it is necessary to obtain an accurate working cast. Objective: To evaluate the accuracy of the transfer impressions of implants performed with individual acrylic resin trays and conventional trays using polyvinyl siloxane. Material and methods: To carry out the transfer impressions, a master cast with four external hexagon implants parallel to each other was used. Five impressions were made with individual acrylic resin trays and five other impressions with modified conventional trays, opened in the region of the implants. The linear measurements between the implants were made with a digital caliper with an accuracy of 0.01 mm and the results were statistically evaluated (alpha = %). Results: For the points AB and BC, the measurements obtained with the individual trays were statistically similar to the master cast. For the points CD and DA no statistical differences among the three groups were observed. Conclusion: Given the obtained results and the methodology used, it can be concluded that the impressions performed with individual trays presented higher accuracy compared to the ones obtained with conventional trays.

Avaliação histológica da laserterapia de baixa intensidade na cicatrização de tecidos epitelial, conjuntivo e ósseo: estudo experimental em ratos / Histological evaluation of the effects of LLLT on the epithelial, connective and osseous tissue healing: experimental study in rats

A cicatrização é um processo fisiológico que ocorre diante de injúrias causadas em tecidos vivos. Muitas pesquisas estão sendo realizadas visando à estimulação do reparo tecidual. O objetivo deste artigo foi avaliar histologicamente a resposta de tecidos epitelial, conjuntivo e ósseo submetidos à laserterapia de baixa intensidade (LBI) em um modelo experimental de reprodução alveolar. Como metodologia, foram realizadas aplicações de LBI em quatro grupo de cinco ratos, nos seguintes parâmetros: 10mW potência única e 660 nm - 7,5 J/cm2; 660 nm - 15 J/cm2; 780 nm - 7,5 J/cm2; e 780 nm - 15 J/cm2. Os tempos experimentais foram 3, 7, 14, 21 e 28 dias. Como resultado, os tecidos epitelial e conjuntivo mostraram renovação celular atípica e acelerada durante o período de irradiação; o tecido ósseo teve sua neoformação acelerada, porém de igual padrão ao grupo controle. Concluiu-se que os tecidos epitelial e conjuntivo reagiram à estimulação de LBI com renovação celular constante. No tecido ósseo houve uma aceleração da neoformação e reparação óssea, dentro dos padrões de normalidade

Wound healing is a physiological process of live tissues. Researches have been made in order to improve this process and establish a fast patient rehabilitation. The aim of this study was to evaluate the histological effects of LLLT AsGaAl (λ = 660nm, 780nm; W = 10mW; , = 7,5; 15J/cm2; t = 5 min) on the epithelial, connective and bone tissue healing, on an alveolar model. Rats were submitted to the surgical creation of an alveolus between the lower incisor and the first mandibular molar, on both sides. After LLLT application, they were sacrificed on 3, 7, 14, 21, and 28 days. The results showed epithelial and connective tissues with accelerated growth during LLLT application; osseous tissue with accelerated neoformation, however following normal patterns. Thus, epithelial and connective tissues responded to LLLT by means of steady cellular renewal; osseous tissue showed accelerated healing, similar to the normal growth patterns