Polymerization shrinkage of bulk fill composites and its correlation with bond strength

Abstract The present study aimed to evaluates polymerization shrinkage (PS) using microcomputed tomography (μCT) and microtensile bond strength (μTBS) in bulk fill composites (BFC) and conventional class I restorations as well as the correlation between these factors. Class I cavities (4 x 5 x 4 mm), factor-C = 4.2, were created in third molars that were free of caries, which were randomly divided in 4 groups (n = 6): XTI (Filtek Supreme XTE: incremental technique); XTB (Filtek Supreme XTE: single fill technique); TBF (Tetric Bulk Fill); and SF (SonicFill). Each tooth was scanned twice in μCT: T0 was after filling the cavity with composite, and T1 was after light curing. The data were analyzed by subtracting the composite volume for each time (T1 - T0). After 1 week, the teeth were sectioned crosswise in the buccolingual and mesiodistal directions to obtain specimens with approximately 1 mm² thickness and fixed in a universal testing machine to perform μTBS. The Kruskal-Wallis and Dunn tests showed a statistically significant difference for shrinkage in µCT among the XTI and XTB and between the SF and XTB. Regarding the μTBS, all the groups differed from XTB. Bulk fill composites type presents a PS similar to that of the conventional nanoparticulate composite inserted using the incremental technique, but the bond strength was higher for the incremental group, which presented a lower number of pre-test failures when compared to BFC. No correlation was observed between the polymerization shrinkage and bond strength in the studied composites.

Resumo O presente estudo teve por objetivo avaliar a contração de polimerização (CP) usando microtomografia computadorizada (µCT) e a resistência de união por microtração (µTBS) em restaurações classe I de compósitos bulk fill (CBF) e convencional, assim como a correlação entre esses fatores. Cavidades classe I (4 x 5 x 4 mm), fator C=4,2, foram feitas em terceiros molares livres de cárie que foram randomizados e divididos em 4 grupos (n = 6): XTI (Filtek Supreme XTE: técnica incremental); XTB (Filtek Supreme XTE: técnica de preenchimento único); TBF (Tetric Bulk Fill); E SF (SonicFill). Cada dente foi escaneado duas vezes em μCT: T0 -após o preenchimento da cavidade com compósito, e T1 - após a cura à luz. Os dados foram analisados subtraindo o volume do compósito para cada tempo (T1 - T0). Após 1 semana, os dentes foram seccionados transversalmente no sentido vestíbulo-palatino e mesio-distal para obter espécimes com aproximadamente 1 mm² de espessura e fixados em uma máquina de ensaio universal para teste de μTBS. Os testes de Kruskal-Wallis e Dunn mostraram diferença estatisticamente significante para a contração em μCT entre XTI e XTB, e entre SF e XTB. Em relação à μTBS, todos os grupos diferiram do XTB. Compósitos do tipo bulk fill apresentam uma CP similar ao compósito convencional nanoparticulado inserido usando a técnica incremental, porém a resistência de união foi maior para o grupo incremental, que apresentou um menor número de falhas pré-teste quando comparado aos CBF. Não foi observada correlação entre a contração de polimerização e a resistência de união nos compósitos estudados.

Par?metros de influ?ncia no ensaio de microtra??o de sistemas adesivos / Parameters that influence microtensile bond testing of adhesivesystems

The aim of this study was to provide a critical review of the literature regarding factors that can interfere with microtensile test results for enamel and dentin adhesive systems. Primarily, reports in English, Spanish, or Portuguese that were published between July 1994 and September 2009 and are catalogued in MEDLINE and BBO were used. Additionally, we compiled relevant articles found in the references of these articles anddissertations and theses available in electronic databases of Brazilian universities that examined factors that can influence implementationof the microtensile test at each stage. The search strategy included searching for the following key term groups: microtensile and test;microtensile and assay; microtensile and test and parameters; microtensile and test and factors; microtensile and specimen; microtracc?n andespecimen. We reviewed 25 selected articles and found that they showed that even after adjustment of test parameters, changes found in thedentin could be responsible for variations observed amongst results. This influence could potentially be reduced by using the cohesive strengthvalue of dentin adjacent to the adhesive interface as a standard for comparison, but more studies are needed to confirm whether such anapproach would be reliable. Data analysis methodology should be taken into account when comparing studies.

O objetivo deste estudo foi realizar uma revis?o cr?tica da literatura sobre os fatores que podem interferir nos resultados do teste de microtra??ode sistemas adesivos ao esmalte ou dentina. Foram utilizados trabalhos publicados nas bases de dados eletr?nicas MEDLINE e BBO, em ingl?s,espanhol ou portugu?s, entre julho de 1994 e setembro de 2009, refer?ncias destes artigos, al?m de disserta??es e teses dispon?veis em bancos de dados eletr?nicos de universidades brasileiras enfocando o estudo das vari?veis que podem influenciar cada fase da execu??o do ensaio de microtra??o. A estrat?gia de busca incluiu os termos: microtra??o e teste; microtra??o e ensaio; microtensile e test e parameters; microtensile e test e factors; microtensile e specimen; microtracci?n e esp?cimen. Os 25 artigos selecionados demonstraram que mesmo ap?s a padroniza??o de par?metros do ensaio, as altera??es encontradas na dentina podem ser respons?veis pela varia??o do resultado. Uma maneira de reduzir esta influ?ncia seria utilizar os valores de resist?ncia coesiva da dentina adjacente ? interface adesiva como padr?o de compara??o, por?m mais estudos s?o necess?rios. Aspectos relativos ? an?lise dos dados devem ser levados em considera??o quando se compara os estudos.

Salivary retention after application of fluoride gel using toothbrush or tray: a crossover trial

Currently, there are no studies in the literature evaluating salivary fluoride retention after small amounts of fluoride gel are applied to children's teeth. Therefore, the objective of the present study was to compare salivary retention after gel application using a toothbrush or by traditional application with trays. In this crossover study, children with active caries (n = 10) were randomized into one of the following treatment groups: a) application of fluoride gel using a tray (control), or b) application of fluoride gel with a toothbrush (treatment). After a 7-day washout period, the treatments were inverted. Unstimulated saliva samples were collected at baseline and 0.5, 5, 15, 30, 60 and 120 minutes after acidulated phosphate fluoride (APF) gel application in order to analyze fluoride retention in saliva. The area under the curve (AUC) was also calculated. There were no differences in fluoride retention after application of small amounts of APF with a toothbrush compared to traditional gel application using trays at all time points studied, and no differences in AUC were observed (Student t-test, p > 0.05). These results suggest that application of fluoride gel in children using a toothbrush can be utilized as an option rather than traditional trays, since the same salivary retention of fluoride is obtained using a lower dose.

Condicionamento ácido total nas restauraçöes: avaliaçäo clínica de restauraçöes adesivas diretas com sistema de condicionamento ácido total e resina híbrida: um ano de atividade clínica / Total acid etching in dental restorations: clinical analysis of direct adhesive restorations with total acid etching and hybrid resin: a year of clinical activity

Análise clínica do comportamento de restauraçöes adesivas em dentes permanentes vitais. Avaliam-se clinicamente, após um período de um ano, vinte dentes restaurados com o sistema adesivo Scotchbond Multi-Uso/Z-100. Verificaram-se a vitalidade pulpar, ausência de descoloraçäo marginal e retençäo aceitáveis clinicamente