Conventional dual-cure versus self-adhesive resin cements in dentin bond integrity

During post preparation, the root canal is exposed to the oral cavity, and endodontic treatment may fail because of coronal leakage, bacterial infection and sealing inability of the luting cement. OBJECTIVE: this study quantified the interfacial continuity produced with conventional dual-cure and self-adhesive resin cements in the cervical (C), medium (M) and apical (A) thirds of the root. MATERIAL AND METHODS: Forty single-rooted human teeth were restored using Reforpost # 01 conical glass-fiber posts and different materials (N=10 per group): group AC=Adper™ ScotchBond™ Multi-purpose Plus + AllCem; group ARC=Adper™ ScotchBond™ Multi-purpose Plus + RelyX ARC; group U100=RelyX U100; and group MXC=Maxcem Elite. After being kept in 100 percent humidity at 37°C for 72 hours, the samples were sectioned parallel to their longitudinal axis and positive epoxy resin replicas were made. The scanning electron micrographs of each third section of the teeth were combined using Image Analyst software and measured with AutoCAD-2002. We obtained percentage values of the interfacial continuity. RESULTS: Interfacial continuity was similar in the apical, medium and cervical thirds of the roots within the groups (Friedman test, p>0.05). Comparison of the different cements in a same root third showed that interfacial continuity was lower in MXC (C=45.5 percent; M=48.5 percent; A=47.3 percent) than in AC (C=85.9 percent, M=81.8 percent and A=76.0 percent), ARC (C=83.8 percent, M=82.4 percent and A=75.0 percent) and U100 (C=84.1 percent, M=82.4 percent and A=77.3 percent) (Kruskal-Wallis test, p<0.05). CONCLUSIONS: Allcem, Rely X ARC and U100 provide the best cementation; cementation was similar among root portions; in practical terms, U100 is the best resin because it combines good cementation and easy application and none of the cements provides complete interfacial continuity.

Adaptação à dentina de materiais forradores sob restauração de resina composta / Liner adaptation to dentin under composite resin restoration

Introdução: Um dos principais problemas na utilização de resina composta é a sua contração de polimerização e consequente tensão transmitida às paredes aderidas e ao material forrador. Foi analisada a adaptação de agentes protetores à dentina associadosà restauração de resina composta fotopolimerizável. Material e Métodos - CavidadesClasse I oclusal foram confeccionadas com profundidade 1,5 mm, em molares humanos hígidos (n=40). Os dentes foram divididos em 4 grupos, segundo o material de forramento utilizado: FF - resina de baixa viscosidade (Fill Magic Flow), HP - cimento de hidróxidode cálcio fotopolimerizável (Hi-Cal Photo), VLC: cimento de ionômero de vidro fotopolimerizável (Vitro Fill LC), VB: cimento de ionômero de vidro fotopolimerizável(Vitrebond). As cavidades foram restauradas com resina composta (Adper Single Bond2/Filtek Z250), inserida em incrementos oblíquos. Após armazenamento em ambiente úmido a 37°C por 7 dias, os molares foram seccionados no longo eixo do dente e obtidas réplicas em negativo de polivinilsiloxana Adsil e em positivo com resina epóxica. Foi utilizada microscopia óptica para mensuração da porcentagem de adaptação linear domaterial forrador e a parede pulpar. Resultados - Os testes de Kruskal-Wallis e Dunnapontaram diferença estatisticamente significante (p<0,05) entre VB (97,7±1,30) e FF(59,3±33,7), e entre HP (5,3±4,9) e VLC (44,3±24,2). Conclusões - A tensão de contração da resina composta causada à interface adesiva durante sua fotoativação provoca fendas entre o material forrador e a parede pulpar, em magnitudes distintas, mesmo quando ainserção da resina se dá por incrementos. O cimento de ionômero de vidro fotoativado Vitrebond obteve a melhor adaptação.

Introduction: One of the main problems when using composite resin is its polymerization shrinkage and resultant stress transmitted to the adhered walls and to the cavity lining material. This work analyzed the adaptation of protective agents to the dentin associated to the composite resin restoration. Material and Methods - Class I occlusalcavities − 1.5 mm deep − were performed in healthy human molars (n=40). The teethwere divided into four groups according to the lining material used: FF – flowable resin(Fill-Magic Flow); HP – light-cured calcium hydroxide cement (Hi-Cal Photo); VLC –resin-modified glass-ionomer liner (Vitro Fill LC); and VB – resin-modified glass-ionomer liner (Vitrebond). The cavities were restored with composite resin (Adper Single Bond2/Filtek Z250) inserted into oblique increments. After storage in a humid environmentat 37°C for seven days, the molars were sectioned to the long axis of the tooth. Negative replicas were obtained through polyvinyl siloxane (Adsil), and positive ones by epoxyresin. Optical microscopy was used for measuring the percentage of linear adaptationof the cavity liner to the pulp wall. Results - Kruskal-Wallis and Dunn tests showed a statistically significant difference (p<0,05) between VB (97,7 ± 1,30) and FF (59,3 ±33,7), and between HP (5,3 ± 4,9) and VLC (44,3 ± 24,2).Conclusions - The shrinkage stress of the composite resin polymerization causes gaps between the cavity liner and the pulp wall even when restored in increments, in distinct magnitude. The resin-modified glass-ionomer liner Vitrebond proved to have the best adaptability.