Oval versus circular-shaped root canals: bond strength reached with varying post techniques

Abstract The aim of this study was to compare the bond strength (BS) of glass fiber posts (GFP) luted to oval and circular-shaped root canals rehabilitated using varying post techniques, at different intraradicular levels. Ninety 16-mm-long roots of human mandibular premolars, classified either as having oval or circular-shaped canals, were endodontically treated and prepared for restoration using one of three different post techniques (n=15): 1) single GFP; 2) resin-relined GFP; 3) main GFP associated with accessory posts. GFPs were luted with a dual polymerizing resin cement (RelyX ARC) after the canal had been treated with a 3-step etch-and-rinse adhesive system (Adper Scothbond Multipurpose). The samples were sectioned into three 1-mm-thick sections, which were differentiated by the root level (cervical, middle and apical) and tested for push-out BS. Assessment of failure mode was made under a stereomicroscope. Data were analyzed using repeated measures three-way ANOVA and Tukey's test. The root canal cross-section had a significant influence on BS (p<0.001), with the lowest values being observed in oval-shaped canals. The post technique also significantly affected the BS (p=0.018), with the resin-relined GFPs providing the highest BS values in both oval and circular-shaped canals. Irrespective of the cross-section of the root canal and post technique, there was no significant difference in BS in the cervical, middle and apical third of the root canal (p=0.084). In oval-shaped canals, the BS to intraradicular dentin at cervical, middle or apical level could be increased when the GFPs posts were relined.

Resumo O objetivo deste estudo foi comparar a resistência de união (RU) de pinos de fibra de vidro (PFV), cimentados a condutos com secção transversal ovalada ou circular reabilitados com diferentes técnicas de restauração com PFVs, em função do nível intrarradicular. Noventa raízes de pré-molares inferiores humanos, com 16 mm de altura, classificadas como possuindo canais ovais ou circulares, foram tratadas endodonticamente e preparadas para serem reabilitadas com uma das três técnicas de restauração com PFVs (n=15): 1) PFV único, 2) PFV reembasado com resina composta, e 3) PFV principal associado a pinos acessórios. Os PFVs foram cimentados com um agente resinoso de polimerização dupla (RelyX ARC), após o canal ter sido tratado com um sistema adesivo de condicionamento total de três passos (Adper Scothbond Multiuso). As amostras foram seccionadas em três fatias de 1 mm de espessura, de acordo com o nível da raiz (cervical, médio e apical)e foram submetidas ao teste de RU por push-out. A análise do modo de falha foi realizada com auxílio de um estereomicroscópio. Os dados foram analisados utilizando-se a ANOVA a três critérios para medidas repetidas e o teste de Tukey. A secção do conduto apresentou influência na RU (p<0,001), com os menores valores sendo observados nos condutos ovalados. A técnica de restauração com PFVs afetou significativamente a RU (p=0,018), tendo o PFV reembasado proporcionado os maiores valores de RU, tanto em condutos ovais quanto circulares. Independentemente da secção transversal do conduto radicular e da técnica de restauração com PFV, não houve diferença significativa na RU nos terços cervical, médio e apical (p=0,084). Nos canais de secção transversal ovalada, a RU à dentina intrarradicular nos níveis cervical, médio ou apical aumentou com o emprego de PFVs reembasados.

Effect of titanium and stainless steel posts in detection of vertical root fractures using NewTom VG cone beam computed tomography system

PURPOSE: Vertical root fracture (VRF) is a common complication in endodontically treated teeth. Considering the poor prognosis of VRF, a reliable and valid detection method is necessary. Cone beam computed tomography (CBCT) has been reported to be a reliable tool for the detection of VRF; however, the presence of metallic intracanal posts can decrease the diagnostic values of CBCT systems. This study evaluated and compared the effects of intracanal stainless steel or titanium posts on the sensitivity, specificity, and accuracy of VRF detection using a NewTom VG CBCT system. MATERIALS AND METHODS: Eighty extracted single-rooted teeth were selected and sectioned at the cemento-enamel junction. The roots were divided into two groups of 40. Root fracture was induced in the test group by using an Instron machine, while the control group was kept intact. Roots were randomly embedded in acrylic blocks and radiographed with the NewTom VG, both with titanium and stainless steel posts and also without posts. Sensitivity, specificity, and accuracy values were calculated as compared to the gold standard. RESULTS: The sensitivity, specificity, and accuracy of VRF diagnosis were significantly lower in teeth with stainless steel and titanium posts than in those without posts. Interobserver agreement was the highest in teeth without posts, followed by stainless steel posts, and then titanium posts. CONCLUSION: Intracanal posts significantly decreased the VRF diagnostic values of CBCT. The stainless steel posts decreased the diagnostic values more than the titanium posts.