Effect of interim cement application on bond strength between resin cements and dentin: Immediate and delayed dentin sealing.

STATEMENT OF PROBLEM: Despite the advances in materials and techniques, adhesion to dentin is challenging because of the complex composition of dentin's mineral, organic, and fluid phases. PURPOSE: The purpose of this in vitro study was to evaluate the bond strength of 2 different resin cements (conventional and self-adhesive) with or without previous dentin sealing and the effect of interim cement. MATERIAL AND METHODS: Forty-five molars were embedded into acrylic resin blocks and a flat dentin surface was exposed. Twenty teeth (n=5 per group) were treated with the conventional resin cement associated with etch-and-rinse or self-etch adhesive approaches, applied before (immediate dentin sealing) or after (delayed dentin sealing) the application/removal of interim cement. Another 25 teeth (n=5, per group) were treated with self-adhesive resin cement with (self-etch mode [immediate dentin sealing or delayed dentin sealing]) or without adhesive application. Furthermore, in the self-adhesive resin cement group, the application of polyacrylic acid for dentin etching before cementation was evaluated. Composite resin blocks were cemented onto flat, treated dentin surfaces, and the assemblies were sectioned into bar-shaped specimens for microtensile bond strength testing. The data were subjected to 1-way ANOVA followed by the post-hoc Tukey test (α=.05). The failure patterns were classified as cohesive, adhesive, or mixed. RESULTS: The application of adhesive before interim cement (immediate dental sealing) promoted the highest values of bond strength for both resin cements (P<.001). For self-adhesive resin cement, polyacrylic acid-enhanced bond strength after the application of interim cement. CONCLUSIONS: The application of dental adhesive immediately after tooth preparation (immediate dentin sealing) and before the use of an interim cement promoted the highest values of bond strength to dentin with the resin cements tested.

Chemical-physical properties of experimental root canal sealers based on butyl ethylene glycol disalicylate and MTA.

OBJECTIVE: The aim of this study was to evaluate the calcium release, pH, flow, solubility, water absorption, setting and working time of three experimental root canal sealers based on mineral trioxide aggregate (MTA) and two forms of calcium phosphates (CaP). METHODS: The materials were composed of a base and a catalyst pastes mixed in a 1:1. The base paste was made by 60% bismuth oxide and 40% butyl ethylene glycol disalicylate. Three different catalyst pastes were formulated containing 60% MTA or 40% MTA+20% CaP (hydroxyapatite HA or dibasic calcium phosphate dehydrate DCPD), 39% Resimpol 8% and 1% titanium dioxide. MTA Fillapex was used as control. The release of calcium and hydroxyl ions, solubility and water absorption were measured on regular intervals for 28 days. The working time and flow were tested according to ISO 6876:2001 and the setting time according to ASTM C266. The data were analyzed using 1-way ANOVA with Tukey's test (p<.01). RESULTS: All the cements showed basifying activity and released calcium ions. MTA Fillapex showed the highest values of flow (p<.01) and working/setting times (p<.01) and the smallest values of solubility (p<.01) and water absorption (p<.01). SIGNIFICANCE: All experimental materials showed satisfactory physical-chemical properties to be used as endodontic sealers in clinical practice.