Master of Science
David R. Burns
Purpose: This study evaluated microleakage associated with cast restorations that were luted with a resin-modified glass ionomer cement (RelyX) following obturation of the dentinal tubules with either a desensitizing agent (Gluma Desensitizer) or an adhesive system (Scotchbond Multipurpose Dental Adhesive). The effect of acid etching on the removal of the smear layer and its influence on the extent of microleakage associated with the adhesive system was also evaluated.
Materials and Methods: Extracted mandibular premolars (N = 48) were prepared for complete cast restorations and divided into 4 groups (N = 12). In group A ( control), neither a desensitizing agent or a component of the adhesive system was applied prior to luting. In group B, Gluma Desensitizer was used to obturate the dentinal tubules. In group C, Scotchbond Multipurpose Dental Adhesive System was applied to tooth preparations according to the manufacturer's instructions. Tooth preparations in group D received the same dentin surface treatment as in group C, but no acid etching was performed. Cast restorations in all 4 groups were then luted with the resin-modified glass ionomer luting cement RelyX. All specimens were subjected to thermocycling between 8° and 55°C for 500 cycles in water baths, placed in a solution of 0.5% basic fuchsin dye for 24 hours, and then sectioned twice longitudinally, once mesiodistally and then buccolingually. All specimens were examined at X30 magnification with a stereomicroscope equipped with a digital camera. Photographs of all sections were made and the extent of microleakage along the tooth-cement interface was measured in millimeters using an image analysis software. Microleakage was perceived to have occurred along a segment of the tooth-luting cement interface when dye penetration from that segment into the dentinal tubules was detected. One-way analysis of variance (α = 0.05) was performed to identify differences in mean microleakage among the luting groups, followed by Tukey's Honestly Significant Difference Test for pairwise comparisons.
Results: Large standard deviations were found in all 4 groups. No statistically significant difference was found among the control (0.64 ± 0.50 mm), Gluma Desensitizer (0.42 ± 0.24 mm), and Scotchbond Multipurpose without etching (0.67 ± 0.40 mm) groups. However, a statistically significant difference was found between the Scotchbond Multipurpose with etching (1.51 ± 0.92 mm) group and each of the other groups.
Conclusions: The large standard deviations obtained implied a marked amount of variability in microleakage within each group, which might be the result of the small sample size used. The increase in microleakage when 35% phosphoric acid was used prior to dentin bonding is difficult to explain. Within the limitations of the study, the results suggest that the use of a nonpolymerizing, resin-based (Gluma Desensitizer) material or a photopolymerizing, resin-based (Scotchbond Multipurpose) system without etching had no effect on microleakage under cast restorations luted with the resin-modified glass ionomer luting cement RelyX. The increase in microleakage when etching with 35% phosphoric acid was preformed might be explained by the phenomenon known as nanoleakage, but further investigation is recommended in this area.
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