Can surface protection prevent the loss of hardness on dentin and composite resin surfaces exposed to erosive challenges? / ¿Puede la protección de la superficie prevenir la pérdida de dureza en las superficies de dentina y resina compuesta expuestas a erosión?

Objective: This study investigated the effect of endogenous erosion on the microhardness of dentine and a nanofilled composite resin. Procedures for preventing erosion were also studied. Materials and Methods: 90 bovine dentine specimens were divided into three groups in accordance with the method for preventing: negative control, topical application of fluoride and resin-modified glass ionomer varnish. 120 composite resin specimens were distributed into four groups, which also included a resin sealant, among the preventive procedures. Specimens were then randomly divided into three sub-groups according to the exposure to simulate gastric acid solution and subsequent remineralization: negative control, 9 and 18 cycles. Surface analysis was carried out by measuring the Knoop hardness. The data obtained were statistically analyzed using 2-way ANOVA and Tukey test. Result: The mean hardness of dentine and of the composite specimens resin exhibited lower hardness after 18 cycles. However, the resin-modified glass ionomer varnish resulted in greater values compared to the other preventive procedures. Conclusion: A resin-modified glass ionomer varnish seems to be a promising method for minimizing the damage caused by endogenous acid, but its protection can be reduced depending on the intensity of the erosive challenge.

Objetivo: Este estudio investigó el efecto de la erosión endógena sobre la microdureza de la dentina y una resina compuesta de nanorrelleno. También se estudiaron los procedimientos para prevenir la erosión. Materiales and Métodos:90 muestras de dentina bovina se dividieron en tres grupos de acuerdo con el método para prevenir: control negativo, aplicación tópica de fluoruro y barniz de ionómero de vidrio modificado con resina. Se distribuyeron 120 muestras de resina compuesta en cuatro grupos, que también incluían un sellador de resina, entre los procedimientos preventivos. Las muestras se dividieron al azar en tres subgrupos de acuerdo con la exposición para simular la solución de ácido gástrico y la remineralización posterior: control negativo, 9 y 18 ciclos. El análisis de la superficie se realizó midiendo la dureza Knoop. Los datos obtenidos se analizaron estadísticamente mediante ANOVA de 2 vías y prueba de Tukey. Resultados: La dureza media de la dentina y de la resina de muestras compuestas exhibió una dureza más baja después de 18 ciclos. Sin embargo, el barniz de ionómero de vidrio modificado con resina resultó en valores mayores en comparación con los otros procedimientos preventivos. Conclusión: Un barniz de ionómero de vidrio modificado con resina parece ser un método prometedor para minimizar el daño causado por el ácido endógeno, pero su protección puede reducirse dependiendo de la intensidad del desafío erosivo.

Efficacy of Protaper Next Compared to Wave One in Intraradicular Dentin Wear in Flattened Root Canals

Objective: To compare the degree of intraradicular wear in flat channels with mechanized instrumentation. Material and Methods: A total of 48 dental units were selected of central and lateral lower incisors, divided into two groups of 24 units each according to the type of instrumentation system: G1 - Protaper Next Group; G2 -Wave One Group. Teeth were exposed to room temperature for seven days for drying. After this exposure, the initial weighing (P0) of the roots in analytical balance was carried out. After instrumentation, the specimens were again exposed at room temperature for another seven days and then the second weighing (P1) was performed. The difference found between the values attributed to the two weighings of each specimen represented the wear of the dentin walls in order to compare the degree of wear between the study groups. Statistical tests were performed for analysis of variance (ANOVA), using a significance level of 5%. Results: Comparison between rotational and reciprocating systems showed that reciprocating files significantly promoted (p<0.05) increased intraradicular dentin wear in relation to rotating files. Conclusion: The use of Wave One Reciprocating Files was considered more effective in the wear of flattened root canals, thus presenting better cleaning ability in the treatment of inflammatory and/or infectious canal processes.