Bond strengths of a 1-step self-etching system to caries-affected and normal dentin.

This study was designed to evaluate the bond strengths of a 1-step self-etching system and a 2-step "etch and rinse" adhesive system to caries-affected dentin and normal dentin. In addition, the micromorphology of the adhesive interfaces was analyzed using scanning electron microscopy (SEM). Extracted human molars with occlusal caries that had been stored frozen were ground in order to expose the caries-affected dentin and surrounding normal dentin. The teeth were then bonded using either Adper Prompt L-Pop or Single Bond (3M ESPE) and restored with Filtek Z250 (3MESPE). After storage in water for 24 hours at 37 degrees C, the teeth were sectioned, prepared for microtensile bond strength test and tested in tension at a crosshead speed of 1-mm/minute. After debonding of the interfaces, microhardness of the dentin underlying the interface of all specimens was measured. The thickness of the hybrid layers was observed under SEM. The results of this study indicate that the bond strength of Adper Prompt L-Pop adhesive was significantly higher to normal dentin than to caries-affected dentin (p<0.05) and that the bond strength of Single Bond to both normal and caries-affected dentin was not significantly different (p>0.05). Additionally, the thickness of the hybrid layers produced by both adhesive systems was thicker for caries-affected dentin.

Effects of flowable resin on bond strength and gap formation in Class I restorations.

OBJECTIVES: This study measured resin/dentin bond strengths and evaluated gap formation at the pulpal floor of occlusal composite restorations using a flowable resin as a liner with either bulk or incremental placement of the restorative composite. METHODS: Class I occlusal preparations were made in 16 extracted molars, and were randomly divided into two groups for restoration using either One-Step adhesive (OS, BISCO) and Renew composite (RW, BISCO) or OptiBond SOLO adhesive (SOLO, Kerr) and Herculite XRV composite (XRV, Kerr). A flowable resin [AEliteFlo (AE, BISCO) or Revolution (RV, Kerr)] was applied as a liner in half of the specimens of each group. The lined and unlined groups were restored with composite cured in bulk, or cured in 1.5 mm increments. After 24 h in water, the teeth were sectioned into 0.7-mm thick slabs and were examined with an optical microscope (400 x) to determine the presence of internal resin-dentin gaps. The gap-free specimens were trimmed and were subjected to microtensile bond strength testing. Specimens that contained gaps had Knoop hardness of the restorative material measured. RESULTS: All incrementally filled restorations were well adapted to the pulpal floor but nearly all bulk-cured specimens had gaps between the flowable and the hybrid composites. The use of a flowable resin increased the bond strength of OS, but not SOLO. SIGNIFICANCE: The incremental technique prevented gap formation regardless of the use of a flowable resin. In contrast, the use of a flowable composite did not guarantee gap-free restorations or improved bond strength of resin to dentin in bulk-filled restorations.

Fracture resistance of endodontically treated teeth restored with three different prefabricated esthetic posts.

PURPOSE: This study was undertaken to evaluate the role of composition of prefabricated esthetic posts in fracture resistance of endodontically treated teeth in vitro. MATERIALS AND METHODS: Thirty human, single-rooted teeth (maxillary central incisors and canines) with similar root dimensions, extracted for therapeutic reasons, were used in this study. The crowns were removed below the cementoenamel junction to obtain a standard root length of 17 mm. The roots were endodontically treated following the conventional manual technique and randomly assigned to three groups (n = 10) according to the post used: Aestheti-Post, Bisco, Schaumberg, Illinois; FibreKor Post, Jeneric/Pentron, Wallingford, Connecticut; and CosmoPost, Ivoclar Vivadent, Schaan, Liechtenstein. The root canals were rendered patent, and the root preparations were standardized through flaring with the manufacturers' drills included in the respective kits. The posts were cemented with an adhesive system and a resin cement (All-Bond 2 and C&B, Bisco, respectively), according to the manufacturers' directions. Composite resin (Tetric Ceram, Ivoclar Vivadent) crowns were built up using a preformed polyester matrix, and the specimens were mounted in metallic rings with cold-cure acrylic resin and kept in saline solution at 4 degrees C for 24 hours. Fracture resistance was then determined using an EMIC DL-2000 universal testing machine. The crosshead speed was 0.5 mm/min with the 45-degree compressing load at the middle third of the crown. Data were analyzed using one-way analysis of variance and Tukey's test (p < or = .001). RESULTS: Mean fracture resistance was as follows: Aestheti-Post, 83.5 kgf; FibreKor Post, 85.7 kgf; and CosmoPost, 36.5 kgf. The fracture strength of CosmoPost was significantly lower than that of the other posts. Teeth restored with CosmoPost had post fractures, and in three specimens, those were associated with root fractures. Teeth restored with the other two posts presented fractures on the composite crowns.

Effect of acid-etching on the enamel bond of two self-etching systems.

PURPOSE: To evaluate enamel bond strengths of self-etching primer systems with and without the use of phosphoric acid etching. MATERIALS AND METHODS: The enamel of sixteen bovine incisors was ground with wet 600-grit SiC paper, and specimens were divided into seven groups. Group SE and group ABF were bonded with Clearfil SE Bond (Kuraray) and an experimental self-etching primer system ABF (Kuraray) in accordance with the manufacturer's instructions. The enamel of groups SE+AC and ABF+AC was acid-etched (AC) prior to application of the primers. The enamel of groups AC+SE-P and AC+ABF-P was acid-etched and the bonding resin was applied without primer. All of these groups were restored with Clearfil AP-X (Kuraray). For the control group (SB), enamel was etched and bonded with Single Bond (3M) according to manufacturer's instructions and restored with Z-250 (3M). After 24 h of water storage, the teeth were sectioned into 0.7-mm-thick slabs, trimmed for microtensile bond testing and subjected to tensile forces at a cross-head speed of 1 mm/min. After testing, all samples were analyzed with SEM. Data were evaluated by one-way ANOVA and Fisher's PLSD (alpha = 0.05). RESULTS: Acid etching prior to application of the self-etching primer produced higher bond strengths to enamel than self-etching priming only. Omission of the primer step provided bond strengths similar to the other acid-etched groups. SEM analysis revealed that when the acid was applied prior to the self-etching primers, an increase in failure within enamel occurred. CONCLUSION: Since high bond strength to enamel is critical for good margins and seal of the restorations, applying the etching step should be considered in case of restorations that rely mainly on enamel bonding.