Bond Strengths of a 1-Step Self-etching System to Caries-affected and Normal Dentin

Abstract

©Operative Dentistry, 2006, 31-6, 677-681 PNR Pereira • MF Nunes PA Miguez • EJ Swift Jr Clinical RelevanceThe 1-step self-etching adhesive had significantly higher mean bond strength to normal dentin than to caries-affected dentin. Although Single Bond had a similar tendency, bonds to normal dentin and caries-affected dentin were not significantly different. SUMMARYThis study was designed to evaluate the bond strengths of a 1-step self-etching system and a 2-step "etch and rinse" adhesive system to cariesaffected dentin and normal dentin. In addition, the micromorphology of the adhesive interfaces was analyzed using scanning electron microscopy (SEM). Extracted human molars with occlusal caries that had been stored frozen were ground in order to expose the caries-affected dentin and surrounding normal dentin. The teeth were then bonded using either Adper Prompt LPop or Single Bond (3M ESPE) and restored with Filtek Z250 (3M ESPE). After storage in water for 24 hours at 37°C, the teeth were sectioned, prepared for microtensile bond strength test and tested in tension at a crosshead speed of 1-mm/minute. After debonding of the interfaces, microhardness of the dentin underlying the interface of all specimens was measured. The thickness of the hybrid layers was observed under SEM. The results of this study indicate that the bond strength of Adper Prompt L-Pop adhesive was significantly higher to normal dentin than to caries-affected dentin (p<0.05) and that the bond strength of Single Bond to both normal and caries-affected dentin was not significantly different (p>0.05). Additionally, the thickness of the hybrid layers produced by both adhesive systems was thicker for caries-affected dentin.

Penetration of amalgam constituents into dentine

“…It is not known which are the effects of elements from amalgam in dentin in relation to adhesive restorative procedures. As several authors have shown that caries affected dentin renders lower bond strengths to adhesive restorations, [3][4][5][6][7] caution should be exercised in applying adhesive techniques on darkened dentin after amalgam removal. Indeed…”

“…ZnSn(OH) 6 appeared after a few days, whilst CuSn(OH) 6 appeared later, probably due to the initial high dissolution rate of Zn compared to Cu. The small amounts of Zn in the zinc-containing amalgams play a sacrificing role in corrosion processes in dental amalgam, thereby protecting the γ 2 phase as well as the η' phase from early attack.…”

“…23,32 Cu was detected in marginal seals of high and medium copper amalgams, but also in some seals of low-copper amalgams. 32 Sutow et al 35 identified SnO, Sn 4 (OH) 6 Cl and Cu 2 O in conventional amalgam interfaces, and in high-Cu amalgams they found CuCl and Cu 2 O. Also Ca and P have been detected as a component of marginal seals in some studies.…”

“…Corrosion of Zn is supposed to delay corrosion of Sn 8 Hg (γ 2 phase) and Cu 6 Sn 5 (η' phase). 52,53 Zn has been identified as the major corrosion product released in saliva and ZnSn(OH) 6 has been detected on Zn-containing amalgams. 49,50,51,54 On both Zn-free conventional and Zn-free Cu-rich amalgams, CuSn(OH) 6 was found.…”

“…2 Several studies have shown lower bond strengths to caries affected and caries infected dentin. [3][4][5][6][7] Furthermore, it is a very common observation that dentin underneath previous amalgam restorations shows extensive black discoloration (Fig. 1).…”