Purpose: The purpose of infected root canal treatment is to eliminate bacteria invading the root canal and to remove necrosis pulp debris remaining in the root canal. However, it is often difficult to remove such substances with chemicals or mechanical cleaning, and so the use of root canal medication is indispensable for improving the therapeutic effects of infected root canal treatments. S-PRG filler is used in many dental materials for the sustained release of various types of ions. It is known that ions released by S-PRG filler possess antimicrobial activities and promote mineralization of hard tissues. In this study, we investigated the effects of a prototype root canal treatment paste containing S-PRG filler on the outside of the root apex.

 Methods: In this experiment, a root canal paste containing S-PRG filler (S-PRG, SHOFU Corp) was used as an experimental material. We enlarged root canals with root cutting instruments and filled the root canals with the S-PRG paste. We subsequently determined the pH around the root apex by measuring the pH of the buffer in which the apex was immersed and fixed. Concentrations of eluted ions from the root apex and dentinal tubules were also measured. As a control material, a root canal medication made of calcium hydroxide (CA) was used.

 Results: The pH measured around the root apex increased after 12 hours when S-PRG paste was applied in the root canal. The pH continued to rise to the maximum value of 7.7±0.3 after 5 days. Si, Al, Sr, B, Na and F were detected around the root apex when the S-PRG paste was used in the canal. Only Si, B, Na were detected from the dentinal tubules when the S-PRG paste was used. There was no significant decrease in the concentration of B eluted even with increasing the thickness of dentin. When the buffer surrounding the apex was set to be initially acidic, the pH was increased after 12 hours and reached 6.3±0.2 1 week following the application of the S-PRG paste.

 Conclusion: We found that the S-PRG paste when used as a root canal medication increased the pH around the apex, and that ions eluted from the paste were released to the outside of the root canal via the apex and dentinal tubules. It was thus suggested that S-PRG filler may have biological activities such as sterilization of the root apex and induction of mineralization of stem cells.

 Purpose: The purpose of this study was to evaluate the effect of silane coupling treatment on the color stability and surface texture of resin composites.

 Materials and Methods: Two types of experimental light-cured resin composite containing silica particles that were silane coupling treated (SC (+)) or untreated (SC (−)) were used in this study. Each composite material was packed into a ring-shaped stainless-steel mold and photopolymerized. A total of 40 SC (+) specimens and 40 SC (−) specimens were fabricated. The specimens were polished with #600, #1000, #1500, and #4000 silicon carbide paper, and finished with an alumina suspension. Half the SC (+) and SC (−) specimens (20 of each) were thermocycled in rhodamine B solution for 1,000 or 10,000 cycles. The other half were immersed in rhodamine B solution for 24 h, 48 h, 72 h, or 7 days. Opacity value, ΔE^*ab, surface roughness, and water absorption were measured after thermocycling or immersion. The surface texture of the specimens was observed by scanning electron microscopy.

 Results: ΔE^*ab, surface roughness, and water absorption were significantly higher in SC (−) than in SC (+). There was no significant difference between the opacity values of SC (−) and SC (+) after immersion, but a significant difference was observed after thermocycling in both. SC (−) showed a significant increase in opacity value as the repetition number of thermal cycles increased.

 Conclusion: In SC (−), during thermocycling, gaps formed between the resin matrix and filler due to the deterioration of incomplete adhesion. Water absorption into the gap allowed the dye to penetrate the interior of the composite, as well as the surface, causing discoloration of the bulk composite. Our results suggested that silane coupling treatment of the filler surface is related to the color stability of the resin composite.

 Purpose: An abfraction lesion is a type of non-carious cervical lesion (NCCL) that presents as a sharp defect on the cervical part of a tooth, and arises from occlusal forces. Occlusal forces lead to stress on the cervical part of the tooth, resulting in disruption of the cervical enamel. There is complexity associated with the mechanical or chemical processes in the creation of abfraction lesions: erosion, abrasion, and attrition have all been associated with the formation of these lesions. Cervical micro-cracks predispose the surface to erosion and abrasion. This study aimed to analyze mineral density and micro-cracks in extracted teeth with NCCL after demineralization, using micro-computed tomography (micro-CT).

 Methods: Eight premolars with NCCL were immersed in a demineralization solution (pH 4.5) for 14 days. After 0, 7, and 14 days of demineralization, the specimens were non-destructively scanned by micro-CT set to a resolution of 9.98 μm/voxel, with X-rays at 100 kV and 30 μA, 0.5-mm Al filter, and beam-hardening corrections. Grayscale values were converted to mineral density values using phantoms and 3D analysis software. Thin sections at the same positions were then prepared for scanning electron microscopy (SEM) examination. The changes in maximum crack width (μm) in the enamel surface were measured at each time point.

 Results: Based on the results obtained from micro-CT images of the whole teeth after demineralization, the mineral density of the enamel at the cervical region was smaller than that at the occlusal region after 14 days of demineralization. Micro-CT images around the cementoenamel junction showed destruction of the enamel layer after demineralization. The changes in crack width in the enamel were approximately 37.3±23.7 μm after 14 days of demineralization. Comparisons of the micro-CT and SEM images revealed that the lines of the cracks were at the same positions.

 Conclusions: Within the limitations of this study, micro-cracks on the cervical surface of human premolars with NCCL were detected by micro-CT. Demineralization of the cervical region progressed along the micro-cracks. Quantitative assessment by micro-CT can be used as a non-destructive measurement for examination of abfraction lesions.

 Purpose: For endodontic treatment, biocompatibility of root canal filling sealer is essential. In the present study, we examined the effects of a newly developed bioactive glass based sealer (BG based sealer) on cell migration ability and viability to clarify the biocompatibility of this sealer.

 Methods: Human periodontal ligament cells (HPDLC) and osteoblast-like cells (MC3T3-E1) were respectively cultured in 24-well Transwell plates. Transwell culture inserts including sealers (eugenol based, non-eugenol based, or BG based sealers) were inserted into the wells, then cell migration ability and viability were analyzed by wound healing assay and trypan blue staining.

 Results: In the wound healing assay, migration ability of HPDLC under eugenol based sealer was not analyzed because of cell death. Under eugenol based sealer (quick), non-eugenol based sealer, or BG based sealer, HPDLC showed migration ability, but the ability was suppressed compared with the control. MC3T3-E1 under eugenol based sealer showed cell survival but not migration. Under eugenol based sealer (quick), non-eugenol based sealer, or BG based sealer, MC3T3-E1 showed no significant difference of cell migration in comparison with the control. In trypan blue staining, eugenol based sealers significantly suppressed the viability of both cells, while non-eugenol based and BG based sealers showed no effects on the viability of both cells, and they increased time-dependently.

 Conclusion: BG based sealer showed suppressive effects but did not inhibit the migration ability of HPDLC, and showed no significant inhibitory effects on the viabilities of both cells, suggesting that BG based sealer has high biocompatibility.