The purpose of this study was to evaluate the adhesion mechanism of a self-etching primer (Teeth Primer, Sun Medical) supplied with 4-META/MMA-TBB resin (Super-Bond, Sun Medical) to enamel. Teeth Primer and 60-65% phosphoric acid (Red Activator, Sun Medical) were used as the surface treatment agents. Ground surfaces of human enamel were obtained. The surfaces were treated with one of the agents and covered with Super-Bond. The bonded specimens were analyzed using the following devices: scanning electron microscope (SEM), field emission scanning electron microscope (FE-SEM), high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM), electron energy loss spectroscope (EELS), energy dispersive X-ray spectrometer (EDS), and micro-Raman spectroscope (Raman spectroscopy). In the SEM images, the specimen treated with phosphoric acid exhibited demineralized enamel and the formation of resin tags, whereas the specimen treated with Teeth Primer apparently did not exhibit enamel demineralization. By contrast, in the observations by FESEM, HAADF-STEM and EELS, the specimen treated with Teeth Primer exhibited nano-level demineralized enamel and closely impregnated resin. Furthermore, the EDS and Raman spectroscopic analyses revealed that in the specimen treated with Teeth Primer, resin had penetrated into the enamel to a depth of several tens of micrometers. The results suggest that the nano-level demineralization of enamel and improvement of monomer penetration into enamel with Teeth Primer treatment contribute to the bond strength.

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Aim: Root canal filling with adhesive resin sealer is more likely to increase the resistance to vertical root fracture. The aim of this study was to compare the vertical fracture resistance of teeth whose root canals were filled with resin-based sealer in combination with resin point or gutta-percha point. Materials and Methods: Extracted bovine root canals were prepared to size #140. After preparation, root canals were filled with the following: (1) group R: Single resin point and 4-META/MMA-TBB resin-based sealer (SBS), (2) group G: Single gutta-percha point and SBS, or (3) group C: No filling. The resin points consisted of 4-META/ MMA-TBB resin and were the same shape as #140 point. A test of the tensile strength in the bucco-lingual direction was performed. As a result, the average tensile strength in group R (112.0±20.5 N) was significantly higher than that of group C (53.6 ±7.7 N) and group G (55.9±11.3 N) (p<0.05). There was no significant difference between group C and Group G. Therefore, it is suggested that root canal filling with resin-based sealer and resin point is effective for increasing the resistance to vertical root fracture.

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A self-etching adhesive system, Peak SE, was released by Ultradent Co. in 2013. The purpose of this study was to observe the bonded interfaces between Peak SE and enamel/dentin under SEM by means of the Ar-ion beam etching technique. An extracted human molar was cut perpendicularly to the tooth axis, and the surfaces of enamel and dentin were finished with #1,000 SiC paper. The surfaces were treated with Peak SE and light-cured, and Amelogen Plus was placed on them and light-cured according to the manufacturer’s instruction. In the routine technique, the specimen was cut in half and embedded in epoxy resin. After being polished with SiC paper and diamond paste, the specimens were subjected to Ar-ion beam etching for 30 seconds, and then observed under SEM. The SEM observation revealed that the bonding interfaces of Amelogen Plus to enamel/dentin with the bonding agent were tight. Peak SE showed satisfactory adhesion to tooth tissues and restoratives, and was thought to be a promising self-etching adhesive system.

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