Bonding of contemporary glass ionomer cements to different tooth substrates; microshear bond strength and scanning electron microscope study.

OBJECTIVE: This study was conducted to evaluate the microshear bond strength (µSBS) and ultramorphological characterization of glass ionomer (GI) cements; conventional GI cement (Fuji IX, CGI), resin modified GI (Fuji II LC, RMGI) and nano-ionomer (Ketac N100, NI) to enamel, dentin and cementum substrates. MATERIALS AND METHODS: Forty-five lower molars were sectioned above the cemento-enamel junction. The occlusal surfaces were ground flat to obtain enamel and dentin substrates, meanwhile the cervical one-third of the root portion were utilized to evaluate the bonding efficacy to cementum substrate. Each substrate received microcylinders from the three tested materials; which were applied according to manufacturer instructions. µSBS was assessed using a universal testing machine. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey's post-hoc test. Modes of failure were examined using stereomicroscope at ×25 magnification. Interfacial analysis of the bonded specimens was carried out using environmental field emission scanning electron microscope. RESULTS: Two-way ANOVA revealed that materials, substrates and their interaction had a statistically significant effect on the mean µSBS values at P values; ˂0.0001, 0.0108 and 0.0037 respectively. RMGI showed statistically significant the highest µSBS values to all examined tooth substrates. CGI and RMGI show substrate independent bonding efficiency, meanwhile; NI showed higher µSBS values to dentin and cementum compared to enamel. CONCLUSION: Despite technological development of GI materials, mainly the nano-particles use, better results have not been achieved for both investigations, when compared to RMGI, independent of tooth substrate.

Effect of re-etching oxalate-occluded dentin and enamel on bonding effectiveness of etch-and-rinse adhesives.

PURPOSE: To determine whether or not re-etching of oxalate-treated dentin and enamel increases microshear bond strength (µSBS) and improves hybridization. MATERIALS AND METHODS: Two single-bottle etch-and-rinse adhesives, SingleBond (3M/ESPE) and OptiBond S (Kerr), were bonded to deep occlusal dentin and enamel after perfusion under 20 mmHg simulated intrapulpal pressure. For each adhesive tested, the experimental groups were: G1: bonding according to manufacturer's instructions (control); G2: application of oxalate desensitizer (D/Sense Crystal, Centrix) to acid-etched substrate followed by 60 s water rinsing prior to bonding; G3: same as G2, but with a further 15-s re-etching with 35% phosphoric acid before bonding. The microshear bond strength (µSBS) to dentin and enamel was tested (n = 15); a scanning electron microscopic (SEM) analysis of surface topography (n = 2), interface (n = 2), and failure mode was also performed. The data were statistically analyzed using ANOVA and Tukey's tests at p ≤ 0.05. RESULTS: In enamel, both adhesives showed no significant difference in µSBS among groups. In dentin, the highest statistically µSBS for both adhesives was recorded for G1, followed by G2, with the lowest values revealed remnants of calcium oxalate crystals that were removed only from enamel surfaces after re-etching. SEM images of the interface revealed inadequate dentin hybridization in G2 and G3 compared to G1. CONCLUSION: Re-etching after oxalate treatment compromises bonding of single-bottle etch-and-rinse adhesives to dentin and provides no added benefits to enamel bonding.

Microshear bond strength and interfacial morphology of etch-and-rinse and self-etch adhesive systems to superficial and deep dentin.

OBJECTIVE: To compare microshear bond strength (uSBS) of two pairs of etch-and-rinse and self-etch adhesives to superficial and deep dentin. METHOD AND MATERIALS: Occlusal surfaces of 40 sound extracted noncarious human molars were ground to obtain flat dentin surfaces (20 superficial and 20 deep dentin). Twenty-four teeth were used for uSBS test and 16 for scanning electron microscopic examination. Each dentin group was randomly assigned into four groups, according to the adhesive system tested. An etch-and-rinse and a self-etch adhesive from the same manufacturer were utilized: Scotchbond-MultiPurpose and Adper-Scotchbond SE and XP Bond and Xeno IV. CeramX was used for composite microcylinder construction (0.9 mm in diameter and 0.7 mm in height). Five composite microcylinders were constructed on each dentin surface (n = 15 per group). A Lloyd universal testing machine was used to test uSBS at a crosshead speed of 0.5 mm/min. Fractographic analysis of the failure site was performed using a stereomicroscope and measured by image-analysis software. Data were statistically analyzed using ANOVA and Duncan tests. RESULTS: In superficial dentin, Xeno IV showed significantly the highest uSBS, while in deep dentin, XP Bond showed the highest uSBS. The lowest uSBS values in both dentin depths were recorded for Adper-Scotchbond SE. Etch-and-rinse systems bonded better to deep than to superficial dentin, while self-etching systems showed similar performance at both dentin depths. CONCLUSION: Bond strength to dentin is both adhesive- and substrate-dependent. Contemporary adhesive systems may produce variable bonding results to superficial and deep dentin due to variations in their composition rather than their bonding approach or application technique.

Tubular occlusion of simulated hypersensitive dentin by the combined use of ozone and desensitizing agents.

OBJECTIVE: Ozone was suggested for treatment of hypersensitive dentin. The purpose of this study was to investigate the effect of ozone, with or without the use of desensitizing agents, on patency and occlusion of simulated hypersensitive dentin. MATERIALS AND METHODS: Sixty standardized dentin slabs were randomly divided into six groups: distilled water (Control), ozone treatment, fluoride desensitizer (ALLSolutions, Dentsply), oxalate desensitizer (D/Sense Crystal, Centrix), combined use of ozone/fluoride and combined use of ozone/oxalate. Ozone gas was delivered from OzonyTronX (Mymed). Specimens were evaluated using a scanning electron microscope and digital image analysis before and after treatment. RESULTS: Statistical analysis using ANOVA and Mann-Whitney U-tests revealed significantly lower percentage of tubular occlusion with ozone treatment than distilled water at p ≤ 0.05. Scanning electron microscope photomicrographs of oxalate desensitizer specimens revealed a thick homogenous precipitate with significantly higher percentage of tubular occlusion than fluoride desensitizer and distilled water. Combined use of ozone/fluoride resulted in a significantly higher percentage of tubular occlusion than fluoride desensitizer alone. However, no significant difference was found between oxalate desensitizer and combined use of ozone/oxalate. CONCLUSIONS: The use of ozone gas is a viable adjunct to fluoride-containing desensitizers in enhancing tubular occlusion, but is not effective with oxalate desensitizers.