Localized mechanics of dentin self-etching adhesive system

Rodolfo Bruniera Anchieta,Eduardo Passos Rocha,Renato Herman Sundfeld,Carlos Marcelo Archangelo,Manoel Martin Junior,Ching-Chang Ko

doi:10.1590/s1678-77572007000400015

Rodolfo Bruniera Anchieta, Eduardo Passos Rocha + Show 4 more

Open Access

https://doi.org/10.1590/s1678-77572007000400015

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Abstract

The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 microm), two TAG lengths (13 or 17 microm) and two loading conditions (perpendicular and oblique-25 degrees) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 microm) were constructed: M1 - no HL and no TAG; M2 - 3 microm of HL and 13 microm of TAG; M3 - 3 microm of HL and 17 microm of TAG; M4 - 6 microm of HL and 13 microm of TAG; and M5 - 6 microm of HL and 17 microm of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25 masculine). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys, Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (sigma(vM)) and maximum principal stress (sigma(max)) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased sigma(vM) and sigma(max) in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the sigma(vM) and sigma(max) than TAG length. The peritubular dentin and its adjacent structures showed the highest sigma(vM) and sigma(max), mainly in the oblique loading.

Highlights

The bond of the composite resin to the dental substrate has been improved with the development of the adhesive resin systems
The peak of σvM was higher for L2 than that for L1 and it was located on the lateral surface of the peritubular dentin in contact with the TAG in all groups. (Figure 4)
The hybrid layer (HL) thickness and TAG length revealed no substantial influence in L1 for all groups

Summary

Introduction

The bond of the composite resin to the dental substrate has been improved with the development of the adhesive resin systems This should promote a better clinical performance of the restorative material, keeping the integrity and health of the tooth structures[6]. The retention is obtained after etching the dentin with phosphoric acid for 20 seconds, in an etch-and-rinse protocol. This procedure removes the smear layer and smear plugs, exposing the dentinal tubules, and removes the mineral content of the superficial dentin, thereby exposing the type I collagen fibers from the dentin matrix. To reduce the failure at the dentin/ adhesive interface (d/a interface), the adhesive resin infiltration should be complete with no void incorporation, otherwise the stress level in the HL will be increased[5]

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