Effect of Cariogenic Challenge on the Degradation of Adhesive-Dentin Interfaces.

The aim was to evaluate, in vitro, the influence of pH cycling on microtensile bond strength (µTBS) and percentage of nanoleakage (%NL) in the dentin-adhesive interface. Flat dentin surfaces were obtained in 56 extracted third molars. The teeth were randomly divided into four groups (n=14): G1- Single Bond Universal (etch-and-rinse mode); G2- Single Bond Universal (self-etch mode); G3- Scotchbond Multi-Purpose; G4- Clearfil SE Bond. A block of composite was built on the adhesive area. Eight tooth/resin sets were cut parallel to the tooth's long axis to obtain 48 beams (0.8 mm2) for each group. Half of the beams were submitted to four cycles of pH cycling (demineralizing solution for 6 h and remineralizing solution for 18 h). The samples were submitted to µTBS test in a universal testing machine. Six tooth/resin sets were cut parallel to the tooth's long axis to obtain three slices of the central region (1.0 mm thickness). Half of the slices were submitted to pH cycling. The nanoleakage methodology was applied to obtain the %NL at the adhesive interfaces. According to two-way ANOVA, the interaction between factors (adhesive system x storage) was significant (p=0.0001) for µTBS and %NL. After pH cycling, there was a significant decrease in µTBS and a significant increase in %NL for all adhesives. The adhesives applied in the self-etch mode obtained lower %NL, differing significantly from the etch-and-rinse adhesives. It was concluded that the pH cycling negatively influenced the µTBS and %NL for all adhesives evaluated. However, self-etch adhesives allowed less %NL.

Effect of cariogenic challenge on the degradation of adhesive-dentin interfaces

Abstract The aim was to evaluate, in vitro, the influence of pH cycling on microtensile bond strength (µTBS) and percentage of nanoleakage (%NL) in the dentin-adhesive interface. Flat dentin surfaces were obtained in 56 extracted third molars. The teeth were randomly divided into four groups (n=14): G1- Single Bond Universal (etch-and-rinse mode); G2- Single Bond Universal (self-etch mode); G3- Scotchbond Multi-Purpose; G4- Clearfil SE Bond. A block of composite was built on the adhesive area. Eight tooth/resin sets were cut parallel to the tooth's long axis to obtain 48 beams (0.8 mm2) for each group. Half of the beams were submitted to four cycles of pH cycling (demineralizing solution for 6 h and remineralizing solution for 18 h). The samples were submitted to µTBS test in a universal testing machine. Six tooth/resin sets were cut parallel to the tooth's long axis to obtain three slices of the central region (1.0 mm thickness). Half of the slices were submitted to pH cycling. The nanoleakage methodology was applied to obtain the %NL at the adhesive interfaces. According to two-way ANOVA, the interaction between factors (adhesive system x storage) was significant (p=0.0001) for µTBS and %NL. After pH cycling, there was a significant decrease in µTBS and a significant increase in %NL for all adhesives. The adhesives applied in the self-etch mode obtained lower %NL, differing significantly from the etch-and-rinse adhesives. It was concluded that the pH cycling negatively influenced the µTBS and %NL for all adhesives evaluated. However, self-etch adhesives allowed less %NL.

Resumo O objetivo foi avaliar, in vitro, a influência da ciclagem de pH na resistência de união à microtração (RUµT) e na porcentagem de nanoinfiltração (%NI) na interface dentina-adesivo. Superfícies planas em dentina foram obtidas em 56 terceiros molares. Os dentes foram aleatoriamente divididos em quatro grupos (n=14): G1- Single Bond Universal (condicionamento ácido prévio); G2- Single Bond Universal (autocondicionante); G3- Scotchbond Multi-Purpose; G4- Clearfil SE Bond. Bloco de resina composta foi construído sobre o adesivo. Oito conjuntos dente/resina foram cortados paralelamente ao longo eixo do dente para obter 48 palitos (0,8 mm2) para cada grupo. Metade dos palitos foi submetida a quatro ciclos de ciclagem de pH (solução desmineralizadora por 6 h e solução remineralizadora por 18 h). As amostras foram submetidas ao teste de RUµT em máquina de ensaio universal. Seis conjuntos dente/resina foram cortados paralelamente ao longo eixo para obter três fatias da região central (1,0 mm de espessura). Metade das fatias foi submetida à ciclagem de pH. A metodologia de nanoinfitração foi aplicada para obter a %NI nas interfaces. De acordo com ANOVA de duas vias, interação entre os fatores (adesivo x armazenamento) foi significativa (p=0.0001) para for RUµT e %NI. Após ciclagem de pH, houve redução significativa na RUµT e aumento significativo na %NI para todos adesivos. Os adesivos aplicados na técnica autocondicionante obtiveram menor %NI, diferindo significativamente dos adesivos com condicionamento ácido prévio. Concluiu-se que a ciclagem de pH influenciou negativamente a RUµT e a %NI para todos adesivos. Contudo, adesivos autocondicionantes permitiram menor %NI.

Prototype to measure bracket debonding force in vivo.

INTRODUCTION: Material biodegradation that occurs in the mouth may interfere in the bonding strength between the bracket and the enamel, causing lower bond strength values in vivo, in comparison with in vitro studies. OBJECTIVE: To develop a prototype to measure bracket debonding force in vivo and to evaluate, in vitro, the bond strength obtained with the prototype. METHODS: A original plier (3M Unitek) was modified by adding one strain gauge directly connected to its claw. An electronic circuit performed the reading of the strain gauge, and the software installed in a computer recorded the values of the bracket debonding force, in kgf. Orthodontic brackets were bonded to the facial surface of 30 bovine incisors with adhesive materials. In Group 1 (n = 15), debonding was carried out with the prototype, while tensile bond strength testing was performed in Group 2 (n = 15). A universal testing machine was used for the second group. The adhesive remnant index (ARI) was recorded. RESULTS: According to Student's t test (α = 0.05), Group 1 (2.96 MPa) and Group 2 (3.08 MPa) were not significantly different. ARI score of 3 was predominant in the two groups. CONCLUSION: The prototype proved to be reliable for obtaining in vivo bond strength values for orthodontic brackets.

Prototype to measure bracket debonding force in vivo

ABSTRACT Introduction: Material biodegradation that occurs in the mouth may interfere in the bonding strength between the bracket and the enamel, causing lower bond strength values in vivo, in comparison with in vitro studies. Objective: To develop a prototype to measure bracket debonding force in vivo and to evaluate, in vitro, the bond strength obtained with the prototype. Methods: A original plier (3M Unitek) was modified by adding one strain gauge directly connected to its claw. An electronic circuit performed the reading of the strain gauge, and the software installed in a computer recorded the values of the bracket debonding force, in kgf. Orthodontic brackets were bonded to the facial surface of 30 bovine incisors with adhesive materials. In Group 1 (n = 15), debonding was carried out with the prototype, while tensile bond strength testing was performed in Group 2 (n = 15). A universal testing machine was used for the second group. The adhesive remnant index (ARI) was recorded. Results: According to Student’s t test (α = 0.05), Group 1 (2.96 MPa) and Group 2 (3.08 MPa) were not significantly different. ARI score of 3 was predominant in the two groups. Conclusion: The prototype proved to be reliable for obtaining in vivo bond strength values for orthodontic brackets.

RESUMO Introdução: a biodegradação de materiais que ocorre na cavidade bucal pode interferir na resistência de união entre o braquete e o esmalte, causando baixos valores de resistência de união in vivo, em comparação aos valores in vitro. Objetivo: o objetivo do presente estudo foi desenvolver um protótipo para mensurar, in vivo, a força de descolagem de braquetes e avaliar, in vitro, a resistência de união obtida com o uso do protótipo. Métodos: um alicate (3M Unitek) foi modificado por meio da adição de um extensômetro diretamente conectado à garra do alicate. Um circuito eletrônico realizou a leitura do extensômetro, e um software instalado em um computador registrou os valores de força de descolagem do braquete em kgf. Os braquetes ortodônticos foram colados com material adesivo na face vestibular de 30 dentes incisivos bovinos. No Grupo 1 (n = 15), a descolagem foi realizada com o protótipo, enquanto no Grupo 2 (n = 15) foi realizado teste de resistência de união à tração, utilizando-se uma máquina universal de ensaios. O índice de adesivo remanescente (ARI) foi analisado. Resultados: de acordo com o teste de t de Student (α = 0,05), os grupos 1 (2,96 MPa) e 2 (3,08 MPa) não foram estatisticamente diferentes. O escore 3 do ARI foi predominante nos dois grupos. Conclusão: o protótipo mostrou-se confiável para se obter, in vivo, os valores de resistência de união dos braquetes ortodônticos.

Bond Strength of a Novel One Bottle Multi-mode Adhesive to Human Dentin After Six Months of Storage.

OBJECTIVE: The aim of the study was to evaluate the microtensile bond strength (µTBS) of Scotchbond Universal to dentin using the etch-and-rinse or the self-etch technique after 24 h and 6 months of storage. MATERIALS AND METHODS: Flat dentin surfaces were obtained in 24 third molars. The teeth were divided into four groups: G1 - Scotchbond Universal applied in the etch-and-rinse mode; G2 - Scotchbond Universal applied in the self-etch mode; G3 - Scotchbond Multi-Purpose; G4 - Clearfil SE Bond. A block of composite was built on the adhesive area. The tooth/resin sets were cut parallel to the long axis to obtain 40 beams (~0.8 mm(2)) for each group. Twenty specimens were immediately submitted to the µTBS test, and the remaining 20 were stored in water for 6 months. Failures and the adhesive interface were analyzed by SEM. RESULTS: According to two-way ANOVA, the interaction between adhesive and storage time was significant (p=0.015).The µTBS (MPa) means were the following: 24 h - G1 (39.37±10.82), G2 (31.02±13.76), G3 (35.09±14.03) and G4 (35.84±11.06); 6 months - G1 (36.99±8.78), G2 (40.58±8.07), G3 (32.44±6.07) and G4 (41.75±8.25). Most failures were mixed. Evidence of hybrid layer and numerous resin tags were noted for Scotchbond Universal applied with the etch-and-rinse mode and Scotchbond Multi-Purpose. A thinner hybrid layer and fewer resin tags were noted for Scotchbond Universal applied in the self-etch mode and Clearfil SE Bond. CONCLUSION: The results indicate that the µTBS for Scotchbond Universal is comparable to the gold-standard adhesives. Scotchbond Universal applied in the self-etch mode and Clearfil SE Bond revealed higher bond stability compared to the etch-and-rinse mode.

Clinical Evaluation of Indirect Composite Resin Restorations Cemented with Different Resin Cements.

PURPOSE: To clinically evaluate the performance of indirect composite resin restorations cemented with conventional and self-adhesive resin cements over a 12-month period. MATERIALS AND METHODS: Ten patients fulfilled all the inclusion criteria. Twenty-four composite resin restorations were performed using an indirect technique and cemented with a resin cement (RelyX ARC) or a self-adhesive resin cement (RelyX U100). Two independent evaluators analyzed the restorations using modified USPHS criteria after periods of two weeks and 6 and 12 months. Statistical significance between the cements at each timepoint was evaluated with the Wilcoxon test and between timepoints with the Mann-Whitney test, both at a significance level of 5%. Fisher's exact test was used to assess the occurrence of absolute failures. RESULTS: No statistically significant differences were found between the groups at the same timepoint nor between groups at different timepoints. The only significant difference was found for color match for both groups after 12 months. CONCLUSION: After 12 months, indirect composite resin restorations cemented with self-adhesive resin cement performed similarly to those cemented with conventional resin cement.

Microhardness and roughness of enamel bleached with 10% carbamide peroxide and brushed with different toothpastes: an in situ study.

BACKGROUND: This in situ study evaluated the roughness and microhardness of enamel bleached with 10% carbamide peroxide (PC10) and brushed with different toothpastes. MATERIALS AND METHODS: Two groups of volunteers received PC10 and placebo agents for 21 days in two phases in a crossover 2 × 3 study. Fragments of human enamel were distributed among intraoral removable appliances (IRA). Nine fragments, divided into three triplets, were used in each IRA, and these were brushed with toothpastes R (Colgate), W (Colgate Total 12 Whiteness Gel) or BS (Colgate Whitening Oxygen Bubbles Fluoride). Treatments agents were applied for 8 h overnight. After brushing, the volunteers used the IRA for about 16 h/day. After a washout period, new IRAs were distributed and the volunteers were crossed over to the alternate agent for 21 days. Roughness and microhardness were measured before and after each phase. RESULTS: According to the paired Student's t-test, roughness of enamel increased and microhardness decreased (P < 0.05). According to analysis of variance generalized linear models, only the toothpaste factor was significant (P = 0.037) for roughness. CONCLUSION: Enamel microhardness and surface roughness are altered when PC10 bleaching is associated with tooth brushing using toothpastes BS, R, and W.