Effect of acid etching time and technique on interfacial characteristics of the adhesive–dentin bond using differential staining

Abstract

Dentin bonding using the total-etch method has been claimed to be technique-sensitive. The aim of this study is to examine the effect of acid-etch variations on the dentin demineralization and interfacial structure of the adhesive-dentin bond using a differential staining technique. Single Bond adhesive with 35% phosphoric acid gel was used. The occlusal one-third of the crown was removed from 60 extracted, unerupted human third molars. Smear layers were created by abrading the dentin with 600 grit SiC under water for 30 s. The prepared teeth were randomly assigned to four groups according to etching time (Group 1, 10 s; Group 2, 15 s; Group 3, 30 s; Group 4, 60 s). In each group, the etching gel was: (i) applied and spread to the dentin surface and left to stand undisturbed; (ii) applied and gently agitated during etching; (iii) applied without using dispensing tips for the syringe and left for the same period as above. After rinsing, the etched dentin was then treated with the adhesive per manufacturers' instructions. 3-5 micro m thin sections of the adhesive/dentin (a/d) interface were cut with a microtome and stained with Goldner's trichrome. Stained, thin sections from each prepared tooth were imaged with light microscopy. The depth and extent of dentin demineralization, and the a/d interdiffusion zone were clearly visible by this differential staining microtechnique. The thickness of the interdiffusion zone increased as a function of etching time. However, the etchant gel application methods have a significant influence on dentin demineralization. Although agitating acid gel facilitates the penetration and etching into dentin, it should not be recommended, especially for longer etching time. These results indicated that the etching technique has a large effect on the profile of both dentin demineralization and interfacial structure.

Influência da marca do condicionador ácido na resistência de união da resina composta à dentina

“…Todos os condicionadores ácidos utilizados apresentaram ácido fosfórico em concentrações que variavam de 30 a 40%, quantidade que se tem demonstrado efetiva na produção de padrão adequado de condicionamento da dentina 6,13,14 . Além da concentração do condicionador ácido, o tempo de condicionamento também teve importante papel sobre o padrão de condicionamento da dentina 15 , sendo que o tempo de 15 segundos parece ser o ideal 13,16 . Assim, uma vez que o tempo de condicionamento foi similar (15 segundos), poder-se-iam esperar resultados semelhantes em padrões de condicionamento, se apenas esses parâmetros (concentração e tempo) fossem observados.…”

“…Em relação à viscosidade dos condicionadores ácidos, tem sido demonstrado que a utilização da ponta da seringa aplicadora é fundamental para um efetivo condicionamento dentinário no tempo preconizado de 15 segundos 13,19 . A pressão exercida pelo êmbolo da seringa contra a entrada, de menor área, da ponta aplicadora provoca uma redução da viscosidade do condicionador (efeito shear thinning) 13 .…”

“…A pressão exercida pelo êmbolo da seringa contra a entrada, de menor área, da ponta aplicadora provoca uma redução da viscosidade do condicionador (efeito shear thinning) 13 . Isso resultada em maior molhamento da dentina pelo condicionador e mais efetivo condicionamento.…”

Clinical application of adhesive systems - a critical review: biomimetic approach

“…When more promising studies began to find evidence of improvements in the results of bonding to dentin, due to acid etching and noting that significant alterations were not found in the pulp tissue, a new obstacle came along for researchers in this area: the technical sensitivity of this procedure [4][5] . Unlike with enamel, several factors have to be checked in detail to obtain correct adhesion to dentin: Analysis of the depth of the cavity and proximity to the pulp 7,19 , duration of acid etching 43 , maintaining adequate humidity after etching 2,17 , length of time required to apply the adhesive materials 19,[34][35] , chemical attributes of these materials 4-5,36 and adequate polymerization 10 are just some of the factors that can significantly influence bonding to dentin. The advances made in adhesive system research have sought to simplify as much as possible the clinical steps which could be influenced by the operator.…”

“…In another study conducted in 2005, the same author showed the presence of demineralized zones not infiltrated by adhesive monomers with various singlestep self-etching systems 42 . The duration of the acid etching was assessed by Wang & Spencer 43 suggesting that the application should be passive, for 15 seconds on the dentin with the Adper Single Bond (3M ESPE, St. Paul, MN, USA) adhesive system.…”