Purpose: After root canal treatment, the tooth is restored with an abutment, for which core build-up resins providing adhesiveness have come into use. This study examined the effect of the thickness ratio of the composite resin used for construction and the thickness of the root dentin on the strength of the construction.

 Methods: This research used four core build-up resins: 1) Clearfil DC Core Automix ONE (DC), 2) BeautiCore Post Paste (BC), 3) Filtek Fill and Core Flowable Restorative Plus (FT), and 4) Estecore (EC). First, 164 experimental specimens of 2.0 mm×2.0 mm×14.0 mm, with dentin thicknesses of 0.5 (D0.5), 1.0 (D1.0), 1.5 (D1.5), and 2.0 mm (D2.0), were prepared from bovine teeth, which were subjected to a three-point bending test in a universal testing machine, and the fracture load was recorded. Second, 40 extracted human single-root teeth were used to perform compressive strength tests of dentin-resin composites. The root side of the tooth was cut to a length of 15 mm from the root apex, and root dentin with the post space of 1/3 width (1/3 P), which is a standard post formation, was used as the control group. Root dentin widths of 2/3 (2/3 P), 3/4 (3/4 P), and 4/5 (4/5 P), and human extracted teeth without core build-up (S) were used as the experimental groups. A universal testing machine was used to apply a static load in the tooth axial direction at a crosshead speed of 1.0 mm/min, and the fracture load was recorded.

 Results: The bending strength of FT was significantly lower than those of BC and EC in the D0.5 group (p<0.05). The bending strength of FT was significantly lower than that of EC in the D1.0 and D1.5 groups (p<0.05).

 The bending strengths of the four core build-up resin groups were significantly greater than that of the S group, which only underwent root canal shaping.

 The highest force required for fracture among the four groups was 41.1±10.6 MPa in the 3/4 P group. This was followed by 39.1±8.8 MPa in the 1/3 P group, 37.5±9.5 MPa in the 4/5 P group, 33.4±4.1 MPa in the 2/3 P group, and 15.3±7.3 MPa in the S group.

 Conclusion: It is suggested that construction using a core build-up resin offers similar compressive strength as conventional abutment construction based on 1/3 width, even if the remaining tooth root is thinner.

 Purpose: Sodium copper chlorophyllin (SCCP) is known to have various effects such as antiallergic and tissue-activating effects, and in recent years is expected to be effectively used in the medical field. Moreover, in the field of dentistry, it is used for treating periodontal disease and trauma. Although there are many reports on the effects of SCCP, few reports have examined how it works. In this study, to elucidate the effects of SCCP on periodontal tissue, we studied physiological changes in vitro in human gingival fibroblasts (HGF) exposed to SCCP.

 Methods: Human gingival fibroblasts were cultured in 15% FBS-containing DMEM. The cells were exposed to SCCP (5 nM, 10 nM, 100 nM, 1 μM, 10 μM), and cell proliferation and mitogens were examined.

 Results: Cell proliferation increased significantly with 100 nM SCCP, and an increase in mitotic factors that promoted cell proliferation was observed.

 Conclusion: The results suggested that 100 nM SCCP stimulates cell division factors of human gingival fibroblasts and promotes cell proliferation, thereby promoting wound healing.

 Purpose: Bioceramics-based root canal sealers are becoming essential in modern endodontics worldwide and are currently being used in Japan; however, there have been no follow-up studies on teeth treated using these sealers. The purpose of this study was to retrospectively evaluate 3-year follow-up data pertaining to teeth treated with a bioceramics-based root canal sealer.

 Methods: Patients treated at the Division of Tooth Therapy (Endodontics and Restorative Dentistry) of Kyushu Dental University Hospital and a private dental clinic were recruited, and 127 teeth that were obturated with a bioactive glass-based root canal sealer were followed up for 3 years. The rates and incidence of functionally surviving and extracted teeth were analyzed. Additionally, 56 teeth with 3-year follow-up radiographs were assessed using the periapical index (PAI) score.

 Results: One hundred and fifteen teeth (91%) survived functionally, and 12 teeth (9%) were extracted during the 3 years. The 12 extracted teeth were initially diagnosed as non-preservable by the dentist because of root cracks or fractures and extensive bone defects, but were endodontically treated in accordance with the patients’ strong requests. There were significant associations between functional surviving and extracted teeth and tooth type, subjective symptoms, initial treatment/re-treatment, and cracks/fractures. In contrast, there was no significant difference between surviving and extracted teeth according to the root canal obturation technique, pain immediately after root canal obturation, and overfilling of the root canal. In the comparison according to PAI scores, the rates of scores 1 and 2 increased, whereas those of scores 3 and 4 decreased.

 Conclusion: This 3-year retrospective follow-up study of root canal-obturated cases revealed that the bioactive glass-based root canal sealer evaluated herein, a bioceramics-based sealer, can be applied to achieve favorable outcomes in endodontic therapy.

 Purpose: Fiber posts with resin cores have been widely used as direct build-up materials for the restoration of endodontically treated teeth. However, the influence of light irradiation mode, including the irradiation intensity and time, on resin polymerization in the apical root canal remains an open research problem. This in vitro study investigated the influence of light irradiation mode on the polymerization of different light-curing resins with and without a fiber post.

 Methods: A translucent fiber post, namely i-TFC Luminous fiber, was used in combination with five commercial light-curing resins: i-TFC System Universal (UN), i-TFC System Blue (BL), i-TFC Luminous core LC flow (LC), Filtek U (FU), and MI core LC flow (MI). Each resin was filled into an artificial root canal model (diameter: 3 mm, depth: 15 mm) with or without the fiber and light-cured using a handy light-curing unit in two irradiation modes: mode-F3: 2,000 mW/cm² for 3 s, and mode-10: 1,200 mW/cm² for 10 s×3. The cured resins were characterized by their polymerization ratios, depths, and optical transmittances.

 Results: The polymerization ratio of each resin was significantly higher in mode-10 than in mode-F3 with and without the fiber post. In the fiber-post groups with mode-10, the polymerization ratio was over 96% for each resin. In the fiber-post groups with mode-F3, the polymerization ratio of each resin was relatively low: 90.5±3.6 for UN, 92.8±4.8 for BL, 85.2±3.7 for LC, 92.7±2.3 for FU, and 75.1±5.2 for MI. The polymerization depth of each resin with the fiber post reached 15 mm for each mode. The LC resin produced the highest optical transmittance, followed by the UN, BL, MI, and FU resins.

 Conclusion: Longer light irradiation and the use of a fiber post were found to be essential to achieve sufficient resin polymerization in the apical root canal.

 Purpose: Surface pre-reacted glass-ionomer (S-PRG) fillers possess properties of releasing ions such as fluoride, strontium, and borate ions, and exhibit bioactive effects. In this study, we assessed the in vivo preclinical effect of a sealer containing S-PRG filler (S-PRG sealer). Specifically, we evaluated the inflammatory response of periapical tissues to the use of S-PRG sealer in root filling, compared to that of sealers with other main components (mineral trioxide aggregate (MTA), resin, and noneugenol-zinc oxide (ZO) ).

 Materials and Methods: Under general and local anesthesia, premolar pulpectomies were performed in 10-month-old beagle dogs. After root canal preparation, cleaning, and drying, root filling was performed by applying various sealers with gutta-percha master points. Periapical lucency was analyzed radiographically, and the area of inflammatory cell infiltration with bone resorption was analyzed histologically. The inflammatory response of periapical tissues to S-PRG sealer was compared to those of clinically used sealers including MTA (Pro Root MTA), resin (AH Plus), and ZO (Canals N). Tissue specimens were prepared at 1 month and 6 months after obturation.

 Results: Periapical lucency was observed at 1 month in all groups. However, at 6 months, periapical lucency persisted with Canals N, but was infrequent with the other three fillers. In histological sections at 1 month, all groups showed similar levels of infiltration of inflammatory cells into the periodontal tissues adjacent to the root apical foramen. After 6 months, inflammation of the periodontal tissues was significantly improved (p<0.05) for all sealers except for Canals N.

 Conclusion: The inflammatory response to S-PRG sealer at periapical tissues was milder than that to Canals N. The S-PRG sealer may provide biocompatibility comparable with that of commonly and clinically used Pro Root MTA and AH Plus in the healing of the periapical region.

 Purpose: Oral malodor, which concerns many people, is associated with volatile sulfur compounds (VSCs) produced by periodontopathic bacteria such as Porphyromonas gingivalis. Maillard products are used in the food industry to decrease hydrogen sulfide (H₂S), which disturbs the flavor and taste of food. In the present study, we planned to apply Maillard reaction products for reducing VSCs to meet the needs demand of patients who want to rapidly decrease oral malodor.

 Methods: The effect of maple sugar solution (a Maillard reaction product) on VSC decrease was examined by adding it to sonicated extract of P. gingivalis. Next, the rare sugar allulose was used for the Maillard reaction (to generate Maillard-allulose), because allulose has no calories and does not cause dental caries. The effect of Maillard-allulose on VSC decrease was examined by adding it to P. gingivalis-derived and chemically-prepared H₂S. After 1 min, headspace air was collected and the concentration of H₂S was measured using the Oral Chroma portable gas chromatography system. Separately, headspace air from a mixture of sodium mono-hydrogen sulfide and Maillard-allulose was analyzed by a solid phase micro extraction method with gas chromatography-mass spectrometry.

 Results: Both maple sugar and Maillard-allulose decreased bacteria-derived and chemically-prepared H₂S. New material seemed to be generated after mixing sodium mono-hydrogen sulfide and Maillard-allulose, indicating that H₂S may have bound to a component of Maillard-allulose, resulting in loss of volatility of H₂S.

 Conclusion: Both maple sugar and Maillard-allulose had H₂S-decreasing activity. Maillard-allulose is not associated with dental caries and obesity, so it may be a good candidate for use in foods for decreasing oral malodor.

 Purpose: In recent years, there have been reports on the application of Nd: YAG laser (the laser) combined with titanium dioxide (TiO₂), a photoreactive agent, to dental treatment, but there have been no reports on its use for dentin hypersensitivity for the purpose of high reactive level laser therapy. In this study, to investigate the transmittance of the laser combined with TiO₂ through dentin, the transmitted energy of the laser was measured. Furthermore, to investigate the sealing ability of the laser on dentinal tubules, Nd: YAG laser combined with TiO₂ was irradiated to a model dentin affected with hypersensitivity, and the dentin permeability inhibition ratio (permeability inhibition ratio) was measured.

 Methods: STREAK-1 (ALTECH) was used as the laser system. Human extracted teeth were used as test teeth, and dentin disc specimens of 1.0 mm in thickness were prepared.

 Experiment 1: Examination of laser penetration through dentin

 The irradiation conditions were 50 μs-50 mJ-10 pps, 100 μs-100 mJ-5 pps, and 200 μs-300 mJ-5 pps, and the irradiation time 5 seconds. The laser was irradiated through one to five dentin discs, and the transmittance was calculated. In the same way, the laser was irradiated together with TiO₂ solution, and the transmittance was calculated for a single dentin disc.

 Experiment 2: Examination of dentinal tubule sealing ability of laser combined with TiO₂ solution

 The irradiation conditions were 50 μs-50 mJ-50 pps, 100 μs-100 mJ-20 pps, 100 μs-100 mJ-99 pps, and 200 μs-300 mJ-20 pps, and the irradiation time was set to 10 s, 20 s, and 30 s. The specimens were connected to the measuring device and laser was irradiated with TiO₂ solution. The permeability inhibition ratio was measured, and the dentin disc surface was observed by SEM.

 Results: Laser transmittance into dentin significantly decreased with increasing dentin thickness under all the conditions. In addition, the transmittance of the laser significantly decreased under all the conditions when the TiO₂ solution was combined.

 Regarding the sealing ability of the laser combined with TiO₂ solution on dentinal tubules, the permeability inhibition ratio increased significantly with increasing irradiation time at 50 μs-50 mJ-50 pps and 100 μs-100 mJ-20 pps. No significant difference was observed in the permeability inhibition ratio at 100 μs-100 mJ-99 pps and 200 μs-300 mJ-20 pps. SEM observation of the surface of the specimens showed that the dentinal tubules were sealed by cohesive structures under all the conditions.

 Conclusion: The investigation indicates that Irradiation with Nd: YAG laser combined with TiO₂, a photoreactive agent, attenuates the penetration of the laser into dentin and it is effective for sealing dentinal tubules.

 Introduction: We have been studying the effectiveness of the intraoral scanner (IOS) as a tool for dental health guidance. We have confirmed the possibility of scanning the gingiva with high precision and of capturing gingival changes quantitatively and visually by aligning the scan data. In the present study, we investigated whether the shape changes of marginal gingiva generated experimentally by inserting a gingival retraction cord into the gingival sulcus could be quantified and visualized by using IOS recording. In addition, we also studied the improvement of accuracy by alignment method. In other words, the objective of this study was to quantify and visualize the clinical shape changes of the gingiva with high precision by IOS, and to connect them to clinical applications.

 Subjects and methods: The subjects were three faculty members of the Faculty of Health Sciences, Osaka Dental University. First, the oral cavity was scanned three times repeatedly. Then, gingival retraction cords were inserted into the gingival sulcus of four teeth, two in the maxilla and two in the mandible, for each study subject. The data was saved for IOS and as exported data in Standard Triangulated Language (STL) format. The STL data before and after gingival retraction were compared using three-dimensional inspection software.

 Results: In the prealignment, which is the aligning of the scanned whole before and after gingival retraction, the deviation on the tooth surface was within ±0.5 mm in the interquartile range (IQR) for most of the measurement points. The deviation on the gingiva was slightly more variable than that on the tooth surface. For the local best-fit alignment on all tooth surfaces, the deviation on the tooth surface was smaller and less varied than that for the prealignment. On the other hand, the deviation at the gingiva in the local best-fit alignment on all tooth surfaces was larger and more varied than that in the prealignment. As for marginal gingival changes, 97.7% had bulging marginal gingiva and 89.4% had depressed gingival sulcus in the prealignment. In the local best-fit alignment on all tooth surfaces, 98.1% had distended marginal gingiva and 89.4% had depressed gingival sulcus. In the local best-fit alignment on the gingival retracted tooth surface, 97.7% had bulging marginal gingiva and 88.4% had depressed gingival sulcus.

 Conclusions: The following conclusions were drawn from these results: 1. There was little difference in quantification or visualization between prealignment, which optimally aligned both tooth and gingival surfaces, and alignment, which optimally aligned all tooth surfaces in the dentition. 2. Although there is an error in the scanning of the oral cavity by IOS, it is precise enough to be used for dental health guidance. 3. Intraoral scans by IOS allow quantification and visualization of gingival changes.