Effect of the thickness of the resin cement on the bond integrity and strength of glass fiber fiber-reinforced composite post / Efeito da espessura da camada de cimento na integridade e resistência adesiva de pinos de resina reforçados por fibra de vidro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Debonding is the most common cause of failure reported for glass fiberreinforced composite posts and occurs frequently along the adhesive interface between the resin cement and the root dentin. The ideal thickness of the resin cement to preserve the continuity along the cement-dentin interface and to increase the retention of the post is unknown. The purpose of this study was to evaluate the influence of the thickness of the resin cement on the bond integrity and strength of two resin cements used for glass fiber-reinforced composite posts cementation. 30 human maxillary incisors with similar root dimensions were selected, sectioned at the amelocemental junction and endodontically treated. The roots were randomly divided into six groups (n=5), and the post spaces were prepared 8 mm deep using one of the three burs with different diameters: Largo bur nℵ 3 for the control group (L3 1- mm); Largo bur nℵ 4 (L4 1,25-mm) e Largo bur nℵ 5 (L5 1,5-mm) for the experimental groups. Fiber-reinforced composite posts (Fibrekor post, Jeneric Pentron), 1-mm diameter, were cemented to post spaces by using the dual-cure (Duolink, Bisco) or self-cure system (C&B Cement, Bisco). The portion of each specimen that contained the bonded fiber post was sectioned into three 2-mm thick serial slices (cervical, middle, apical) with the Isomet saw under water cooling. The slices were polished and ultrasonicated in deionized water. Polyvinyl siloxane impressions of the observable surfaces were taken and the surfaces replicated with epoxy resin for measuring of the thickness of the resin cement and the bond integrity by using MEV. The slices were stored in physiologic solution at 37o C for one week, and then submitted to the push-out test at a crosshead speed of 0.5 mm/min-1. The maximum force required to dislocate each post was registered (N). Data were analyzed by one-way ANOVA, Tukey test and t test (α=0,05). The correlation between bond integrity, bond strength and thickness of the resin cement was also determined by correlation test (α=0,05). The multiple comparison test between the experimental conditions for each resin cement showed that the mean values of bond integrity (%) and strength (MPa) of the fiber posts cemented with Duolink were significantly higher at the control group (L3: 61.79 ± 18.06 and 11.32 ± 4.66) than those obtained for the experimental groups with the thicker layer cement (L5: 38.91 ± 5.75 and 4.68 ± 2.16) (p=0.018 and p=0.035), respectively. Although there was no significant difference on the bond integrity between the different thicknesses evaluated for C&B Cement (p>0.05), the group with thicker layer (L5: 10.67 ± 4.59) was significantly more retentive than the control group (L3: 4.01 ± 0.76) (p=0.014). The comparison between cements for each experimental condition has showed that Duolink was more retentive than C&B Cement at the control group (11.32 ± 4,66 and 4.01 ± 0,76, p=0.008), whereas C&B Cement was more retentive than Duolink at L5 group (4.68 ± 2.19 and 10.67 ± 4.59, p=0.030), respectively. Only the comparison between the L4 experimental group and the others groups was not significant for both resin cements and tests conducted. The increase of the thickness of the cement significantly reduced the bond integrity (r=-0.5901; p=0.021) and strength (r=-0,5387; p=0.038) for Duolink. Bond integrity positively correlated with bond strength for this type of resin cement (r=0.6855; p=0.005). On the other hand, there was no significant correlation between the thickness of the cement and the bond integrity (r=0.153; p=0.586) and neither between the bond integrity and strength (r=0.2969; p=0.283) registered for C&B Cement. However, the increase of the thickness of this type of resin cement has significantly increased the retention of the post (r=0.6576; p=0.008). Data suggested that the thickness of resin cements affected both the bond integrity and strength of fiber posts. For the Duolink resin cement selected, the higher values of bond integrity and strength were obtained when the thinner layer was tested (L3). However, C&B Cement has showed higher retention when the thickness of the cement increased excessively (L5), though the thickness of the cement has not played a role on the bond integrity of the cement-dentin interface for this resin cement.

ASSUNTO(S)

microscopy electron cimentos de resina microscopia eletrônica post and core techinique pinos de retenção dentária resin cements

ACESSO AO ARTIGO

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