Efficacy of four lining materials in sandwich technique to reduce microleakage in class II composite resin restorations.

OBJECTIVES: The aim of the present study was to evaluate the effect of four different sandwich techniques on gingival microleakage of Class II direct composite resin restorations. MATERIALS AND METHODS: Fifty sound human premolars were selected and randomly divided into five groups (n=10). Class II box only cavities were prepared in one of the proximal surfaces of each tooth with a gingival margin located approximately 0.5 mm below the cemento-enamel junction. Group A (control) was restored incrementally with composite resin (Tetric Ceram). Groups B, C, D, and E were restored with the sandwich technique using a compomer (Compoglass F), flowable composite resin (Tetric Flow), self-cure composite resin (Degufill SC), or resin modified glass ionomer (Fuji II LC), respectively. After thermal-load cycling, the specimens were immersed in 0.5% basic fuschin for 24 hours. Dye penetration (10(-1) mm) was detected using a sectioning technique. Data were analyzed with repeated measurements and Duncan test at α=0.05. RESULTS: The least amount of microleakage was detected in the incremental group (1.28 ± 0.98). The sandwich technique using resin modified glass ionomer (7.99 ± 9.57) or compomer (4.36 ± 1.78) resulted in significantly more leakage than did the sandwich technique using flowable (1.50 ± 1.97) or self-cure composite (2.26 ± 1.52). CONCLUSION: According to the results of this study, none of the four sandwich technique composite resin restorations used in this study could reduce gingival microleakage to a greater degree than the incremental technique.

Comparison of enamel and dentin shear bond strengths of current dental bonding adhesives from three bond generations.

OBJECTIVE: Durability is still a major challenge in adhesive dentistry. One of the biggest areas of development has been to simplify the bonding process by using all-in-one adhesives. The aim of this study was to compare the shear bond strength (SBS) to dentin and enamel of nine dental bonding agents (DBAs) from three generations after simulated aging. METHODS AND MATERIALS: For this study, 108 sound extracted human molars were randomly assigned to nine groups (n=12). The sample teeth were mounted in self-cure acrylic resin sectioned to provide paired enamel and dentin samples. All samples were polished with 240 and 600-grit silicon carbide sandpaper and randomly grouped according to the product and substrates (enamel or dentin). Herculite Ultra resin composite cylinders were bonded on each test surface, stored in 100% humidity at 37°C for 24 hours, and then thermocyled for 1,000 cycles at 5°C and 55°C. SBS testing was performed using an Ultratester at a crosshead speed of 0.5 mm/min. Statistical analysis included two-factor analysis of variance, one-sample Wilcoxon and Kruskal-Wallis tests, and the Scheffe post hoc test at an alpha level of 0.05 using SAS version 9.2. RESULTS: Significant differences in SBS were observed between the sixth- and seventh-generation DBAs (p=0.002) but not between the sixth- and fourth-generation DBAs. Scheffe post hoc tests for the sixth-generation DBAs showed that some DBAs yielded significantly higher enamel SBS than others, but not as much as dentin SBS. As for the seventh-generation DBAs, similar post hoc tests showed significant variations in SBS between substrates (enamel and dentin) and DBAs tested. Significant main effects were also found for the different substrates for the fourth-generation (F[1,96]=10.532; p=0.003) and seventh-generation (F[1,96]=22.254; p<0.001) DBAs, but not for the sixth-generation DBAs (F[1,96]=1.895, p=0.172). The SBS was higher on dentin than enamel for the fourth- and seventh-generation DBAs. CONCLUSION: As expected, fourth- and sixth-generation DBAs generally showed stronger SBS values than the seventh-generation all-in-one DBAs. The new sixth-generation DBA OptiBond XTR (Kerr) showed strong SBS values to both substrates and performed well in comparison to the other DBAs tested.

The effect of surface defects in early caries assessment using quantitative light-induced fluorescence (QLF) and micro-digital-photography (MDP).

OBJECTIVES: The purpose of this study was to consider the impact of surface defects on quantitative light-induced fluorescence (QLF) and micro-digital-photography (MDP) measures, in relationship to lesion depth. METHODS: Simulated enamel carious lesions were developed on 45 extracted human teeth. Images of each tooth were captured with both QLF and MDP. The teeth were sectioned and lesion depth was measured with polarized light microscopy (PLM). Pearson correlations were computed using data from the 27 lesions which did not have surface loss, and then separately based upon the 18 lesions which did display surface loss. MDP variables ΔR and ΔX measure reflected light, whereas QLF variables ΔF and ΔQ measure fluorescence. RESULTS: A strong correlation was identified between lesion depth and ΔF (r=-0.765, p<0.0001), and ΔQ (r=-0.827, p<0.0001) on intact lesions while a weak but suggestive, although non-significant, correlation was identified between average lesion depth and ΔR (r=0.369, p=0.059) and ΔX (r=0.595, p=0.0011). However, the corresponding correlation was not statistically significant, when lesions with surface loss were considered for QLF and MDP measures. CONCLUSIONS: QLF measures ΔF and ΔQ were strongly correlated with lesion depth in lab-simulated lesions with no surface loss, but not among lesions with surface defects. The two MDP-associated measures, ΔR and ΔX, could not be said to differ significantly when lesions with and without surface defects were compared with lesion depth. Because intact lesions can be remineralized, accurate assessment of their status is imperative for caries treatment. CLINICAL SIGNIFICANCE: Dental caries is still widely prevalent today. We now know that with early stage detection, remineralization can be accomplished. Being able to identify dental caries in its reversible stage (before physical surface loss) is paramount for the clinician to be able to treat the disease non-invasively.