Effect of magnification during post space preparation on root cleanness and fiber post bond strength

Abstract The aim of this study was to evaluate the effect of magnification during post space preparation on root cleanness and on fiber post bond strength. Methods: Thirty human central upper incisors with similar root canal in size and shape were selected, decoronated to 15 mm and endodontically filled. The teeth were assigned into 3 groups (n=10), according to the method of magnification during post space preparation inspection: Control, using naked eye; loupe, using a dental surgical 3x magnifying glass; surgical microscope, using a 6x surgical microscope. The roots were scanned by using micro-CT before and after post space preparation for residue remnants evaluation. Fiber posts were cemented using self-adhesive resin cement (Rely X U200, 3M-ESPE). Two 1-mm-thick slices from the cervical, medium and apical thirds were submitted to a push-out test (PBS). Failures modes were classified. PBS data were analyzed by using two-way ANOVA with repeated measurement and the Tukey test. The significance level was set at 5%. The method of visualization had no effect on PBS (p=0.556). The cervical region had higher values than apical region irrespective of the inspection method (p=0.012). Adhesive failure between the resin cement and dentin was the prevalent failure mode for all groups. Micro-CT analysis showed no difference on root cleanness into the root canal after post space preparation. The use of magnification devices as loupe and microscope while performing post space do not improve the PBS and did not affect sealer remain of decoronated anterior teeth.

Resumo Avaliar o efeito do método de visualização durante o preparo do espaço do pino sobre o remanescente de material obturador endodôntico e sobre a resistência adesiva do pino de fibra de vidro. Trinta incisivos centrais superiores humanos com canal radicular circular foram selecionados, foram desobstruídos a 15 mm e obturados. Os dentes foram divididos em 3 grupos (n=10), de acordo com o método de ampliação utilizado para inspeção do preparo: Controle, usando olho nu; lupa, usando uma lupa cirúrgica 3x cirúrgica; microscópio cirúrgico, usando um microscópio cirúrgico 6x. As raízes foram digitalizadas usando micro-CT antes e após a preparação do espaço para avaliação de resíduos remanescentes. Os pinos de fibra foram cimentados com cimento resinoso autoadesivo (RelyX U200, 3M-ESPE). Duas fatias de 1 mm de espessura dos terços cervical, médio e apical foram submetidas ao teste push-out (PBS). Os padrões de falhas foram classificados. Os dados de PBS foram analisados ​​usando análise de variância em dois fatores com medição repetida e o teste de Tukey. O nível de significância foi estabelecido em 5%. Resultados: O método de visualização não teve efeito no PBS (p=0,556). A região cervical apresentou valores maiores que a região apical, independentemente do método de inspeção (p=0,012). A falha adesiva entre o cimento resinoso e a dentina foi o modo de falha prevalente para todos os grupos. A análise de micro-CT não mostrou diferença na limpeza da raiz no canal radicular após a preparação do espaço do pino. Conclusão: O uso de dispositivos de ampliação como lupas e microscópios durante a realização de preparo não melhora o PBS e não afetou a permanência do material obturador remanescente de dentes anteriores.

Medición de la capa híbrida resultante del uso de cementos autograbadores de un paso y dos pasos / Hybrid layer measurement after using one-step and two-step self-etching cements

Antecedentes: La formación de la capa híbrida debe ser proporcional a la capacidad de los cementos para retener con éxito postes de fibra de vidrio en el interior del conducto preparado endodónticamente. Objetivo: Medir el espesor de la capa híbrida en los tercios coronal y apical as usar cementos autograbadores de uno y dos pasos. Métodos: Se realizó un estudio experimental con 30 premolares humanos que se trataron endodónticamente y se asignaron a tres grupos. Se cementaron postes de fibra de vidrio con tres cementos siguiendo las instrucciones de los fabricantes. Se realizaron cortes coronales y apicales y se cuantificó el grosor de la capa híbrida por microscopía electrónica de barrido. Los datos se analizaron con las pruebas estadísticas H de Kruskal-Wallis y U de Mann-Whitney (p<0,05). Resultados: El promedio del grosor de la capa híbrida fue de 0,74 mm con Multilink N® (grupo 1), 0,24 mm con RelyX Ultimate® (grupo 2) y 0,03 mm con RelyX U200® (grupo 3) (p = 0,0092). Los promedios en los tercios coronal y apical fueron: 1,29 mm y 0,19 mm para el grupo 1; 0,33 mm y 0,14 mm para el grupo 2 y 0,26 mm y 0,23 mm para el grupo 3, diferencias que fueron estadísticamente significativas (p = 0,043). Conclusiones: El espesor de la capa híbrida formada con el uso de los cementos de dos pasos fue mayor que con el cemento de un solo paso, especialmente en la porción coronal.

Background: Hybrid layer formation should be proportional to cement properties to successfully retain fiberglass posts into root canals. Purpose: To measure of hybrid layer thickness in coronal and apical thirds after using one-step and two-step self-etching cements. Methods: This experimental study used 30 human premolars with root-canal treatments, which were assigned into three groups. Fiberglass posts were cemented with three types of self-etching cements following manufacturers' instructions. Roots were cut in the coronal and apical thirds and hybrid layer thickness was quantified through scanning electron microscopy. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests (p < 0.05). Results: Average thickness of the hybrid layer was 0.74 µm with Multilink N™ (group 1), 0.24 µm with RelyX Ultimate™ (group 2), and 0.03 µm with RelyX U200™ (group 3) (p = 0.0092). Average thickness in coronal and apical thirds were: 1.29 µm and 0.19 µm for group 1; 0.33 µm and 0.14 µm for group 2; and 0.26 µm and 0.23 µm for group 3, differences that were statistically significant (p = 0.043). Conclusions: The thickness of the hybrid layer formed after suing two-step cements was greater than that of one-step cement, especially in the tooth coronal third.