Study on the Sealing Ability of a New High-penetration Resin Material for Enamel Cracks and Dentinal Tubules

Abstract

 Purpose: In line with the increasing number of remaining teeth per person, the incidence of noncariogenic hard tissue diseases other than dental caries and periodontal disease has been increasing. Among noncariogenic diseases, micro cracks of enamel (enamel cracks) may be a cause of hypersensitivity with no substance defect. Furthermore, exposed dentin is a cause of dentin hypersensitivity to transient cold water and abrasion pain. A new high-penetration resin material for tooth substrates having high flowability, hydrophilicity and wettability also has high penetrability for enamel cracks and dentinal tubules. Considering the sealing of enamel cracks and dentinal tubules with resin-based dentin desensitizers, we measured the permeability inhibition rate using a tooth model of hypersensitivity.

 Methods: Enamel crack specimens and dentin disc specimens were prepared using healthy human teeth with no dental caries. Using a device prepared following the method reported by Pashley et al., the specimen was connected to the device and the inner pressure was set at 25 mmHg. The materials used in the experiment were the new high-penetration resin material for tooth substrates (KE, Kuraray Noritake Dental) and resin-based desensitizers G-Premio BOND (GP; GC) and Scotchbond Universal Adhesive (SU; 3M ESPE). After application of each desensitizer, the enamel crack and dentinal tubule permeability inhibition rate was measured. The surface and longitudinal cross-sectional surface in the enamel crack specimens and dentin disc specimens were observed under SEM, and the penetration depth of resin in enamel cracks was measured.

 Results: The permeability inhibition rate of the enamel cracks in the KE, GP and SU groups was 96.0, 96.3 and 94.0%, respectively. The permeability inhibition rate of the dentinal tubules in the KE, GP and SU groups was 90.0, 94.2 and 93.7%, respectively. There was no significant difference in the permeability inhibition rate of the enamel cracks and dentinal tubules between the KE, GP and SU groups, and the permeability inhibition rates of all groups were high. SEM images showed that the superficial layer of the enamel cracks and dentin was covered with a resin coating in all the groups, and that the longitudinal cross-sectional surface of the enamel cracks was sealed with resin in all the groups. The penetration depth of resin in the enamel cracks was significantly higher in the KE group than in the GP and SU groups. On the longitudinal cross-sectional surface of the KE group, we observed long resin tags which penetrated into the dentinal tubules. However, we did not observe any resin tags penetrating the dentinal tubules in the GP group, and observed resin tags that penetrated slightly into the dentinal tubules in the SU group.

 Conclusion: It is considered that the new high-penetration resin material for tooth substrates delivered a better sealing ability than conventional resin-based desensitizers for enamel cracks and dentinal tubules.