Influência da viscosidade do condicionador ácido na dentina radicular sobre a resistência de união de um sistema de cimentação adesivo. Avaliação por teste de push-out e MEV

Actually different alternatives to restored teeth with endodontical treatment are propose, otherwise with the advented of adhesive systems their use as luting endodontical cements and bonding resin cement for fiber posts are common. However the inherent characteristics behavior of these materials and the different variances presented at root canal, turns them sensible to failure. The aime of the study was to evaluated: a) the influence of two luting cements: containing eugenol (Endofill) and containing resin materials (Ahplus) on dentin bonding strength using push-out test at cervical, medium and apical root dentin regions, using two different 37% phosphoric acid viscosities: gel and liquid: b) the effect of the total-etching acid process on the pattern observed of the conditioned dentine substrate, c) Characterize the dentinal surface at different root regions d) Classify the fracture patterns between the substrate and the resin cement at three root regions. One hundred and four uniradicular teeth without caries lesions, extracted by orthodontics or periodontal reasons, with 7mm of diameter and 14mm of length were selected, disinfected in 0,5% chloramine and storage in distillated water at 5ºC. Endodontical canal treatments were performed using the Step-back technique and obturated with Endofill and AHplus. The preparation of the post space was 11mm depth using standardized rotary instruments. The total-etching with the gel and liquid acid were performed. The fiber posts were marked at the same depth, cuted, dry and silanized. Then two coats of Prime&bond 2,1 previously mixed with the self-cure activator, were applied at the post surface and into de root canal, after 1 minute the post were photocured (halogen light intensity of 450mW). The resin cement was mixed and placed into de canal using a lentuloespiral instrument. The posts were placed and a static force of 5kg for 10 minutes were applied, after words both adhesive and cement were photocured for 40 seconds, storage for 24 h in 37ºC, and embedded in a poliestyren resin. Cross-sectional cuts were obtained for the push-out test. The test were performed at a crosshead speed of 0,5mm/min, and a plane 20 cylindrical point was applied at the post centre. The maxim load was calculated in Mpa. The adhesive area was calculated using a tapered-cone shaped formula. The results were subjected to statistical analysis using a ANOVA test for multiple variables and a Pos Doc test(p<0,05) Statistically significant differences were detected between all the evaluated criterias: acids, cements and regions, and when they were inter-relationated between them. It was concluded that the use of 37% of phosphoric acid in a liquid form, allows a better penetration into the root canal, a uniform decalcification, consequently enhancing the bonding strength of the root dentine, particularly at apical region.Actualmente diversos tipos de alternativas para restaurar dentes submetidos a tratamento endodontico são propostos, dentre estes, sistemas adesivos resinosos cimentantes para uso endodontico e pinos de fibra. No entanto as carateristicas inerentes apresentadas por estes materiais e as diversas variáveis presentes em nível radicular os fazem sensíveis a falhas. O objetivo deste trabalho foi avaliar a influência do tipo de cimento endodôntico e da viscosidade do ácido sobre a resistência de união de um sistema adesivo utilizando pinos de fibra de vidro, mediante o teste push-out e MEV em três níveis radiculares: cervical, médio e apical. Foram selecionados 104 dentes uniradiculares sem cárie, extraídos por motivos periodontais ou ortodônticos. Os dentes foram desinfectados em cloramina 0,5% e armazenados em água destilada a 5ºC. Os tratamentos endodônticos foram padronizados com a técnica step-back, obturando-se com Ahplus ou com Endofill. Os preparos para os pinos foram de 11mm padronizando os instrumentos. O condicionamento com o ácido fosfórico a 37%, em gel ou em líquido, foi realizado em ambos grupos. Os pinos de vidro foram seccionados em 11 mm,, silanizados, cobertos com duas camadas de Prime&bond 2.1 misturado previamente com o ativador de autopolimerização. O cimento resinoso Enforce (Dentsply) foi misturado e aplicado no canal utilizando lentulo. O pino era inserido e aplicava-se uma força padronizada de 5kg durante 10 min e sendo polimerizados por 40 seg, e armazenados por 24 horas a 37ºC, incluídos em resina de polietileno, cortados em 6 discos transversais de 1,5mm e lixados. O teste de push-out foi com uma velocidade de 0,5 mm/min, a ponta ativa cilíndrica plana (0,9 mm de diâmetro) era aplicada no centro do pino. A carga máxima foi convertida em MPa.. As diferenças entre os grupos foram determinadas mediante a análise de variância de ANOVA de três critérios, teste de Post Hoc (p