Purpose: Treatment based on the minimal intervention (MI) concept is now widely performed, and the use of restoration treatment using composite resin (CR) has increased. In the molar regions, CR restoration is widely applied to ClassⅡ cavities. However, in these cavities, a septum, such as a sectional matrix, is attached corresponding to the anatomical morphology of the tooth, simultaneously with the formation of a cavity with a narrow width minimizing tooth grinding for MI, through which light for polymerization is unlikely to reach the gingival side wall in the deepest region of the cavity. In this study, using halogen-type and light-emitting diode (LED) curing units, we measured the tensile bond strength at various irradiation distances and light intensities to investigate the influence of the irradiation energy of the curing units on the bond strength of CR restorations.
 Methods: A frozen extracted bovine tooth was thawed under running water. The labial side of the crown was cut using a model trimmer to flatten the dentin surface, and then polished with waterproof #600 abrasive paper. A metal mold with a 3-mm inner diameter and 2-mm height was fixed to the adherend surface with double-sided adhesive tape. The irradiators used in this study consisted of a halogen-type curing unit, Curing Light XL3000 (“XL” ; 3M ESPE) and LED-type curing units, Elipar S10 (“S10” ; 3M ESPE) and PENCURE 2000 (“PC” ; J. Morita MFG.). Light irradiation using PC was used in the normal mode (PC-N) and high-power mode (PC-H).
 Results: When light was irradiated at 60° from the lingual direction to the occlusal surface, the light intensity decreased significantly compared with that at an irradiation angle of 90°. When the irradiation distance was increased from 2 to 7, 12, and 22 mm, the light intensity decreased, and the bond strength also decreased. When the light intensity of the curing units was increased from 100 to 200, 400, and 600 mW/cm², the bond strength improved. When the light intensity of the curing units was set at 100, 200, 400, and 600 mW/cm² and the irradiation time was prolonged so as to obtain a uniform amount of light energy, the adhesive strength at the light intensity of 100 and 200 mW/cm² decreased significantly compared with that of 600 mW/cm² even though the irradiation time was increased.
 Conclusion: When the irradiation distance was increased from 2 to 7, 12, and 22 mm, the adhesive strength also decreased, and when the light intensity of the irradiators was increased from 100 to 200, 400, and 600 mW/cm², the adhesive strength improved.

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 Purpose: Freezing electrolyzed functional water with no convection limits contact with oxygen. Precipitation of substances dissolved in the water limits the amount of those substances in the water. This helps to protect components in the water and allows prolonged storage with little loss of antimicrobial potency. Functional water with various properties was generated and preserved by freezing under various conditions to ascertain changes in those properties after thawing.
 Materials and Methods: A 2-chamber functional water generator and storage tank was fabricated. Electrolysis of a saline solution yielded acidic water and alkaline water. Ten ml of each aqueous solution was collected when water was generated, and each solution’s pH, ORP (mV), and residual chlorine concentration (ppm) were measured. Sixty ml of each aqueous solution was injected into a container (80 ml) and then frozen at −17°C for 24 and 168 hrs. The container was then thawed at room temperature (23°C) for about 2 hrs. The solution’s properties were then measured again. Conditions for this experiment were: addition of 3 amounts of sodium chloride (factor A): 0.3, 0.6, and 0.9 wt%; 2 electrolytic currents (factor B): 2 and 4 A; 2 methods of storage (factor C): closed or open container; and 2 freezing times (factor D). Conditions were randomly varied and 3 repetitions were performed. Conditions were analyzed using 4-way analysis of variance, and the same data were subjected to Welch’s t-test to examine the method and duration of freezing and storage. The properties of functional water immediately after generation were subjected to regression analysis using the equation for a line describing the same solution’s properties after thawing.
 Results: Analysis revealed that a thawed solution of acidic electrolyzed water retained its acidity (a pH of less than 2.2). Its ORP was 1,100 mV or greater. After preservation by freezing, the chlorine concentration (ppm) in the solution decreased over time from 263 ppm. Addition of a large amount of sodium chloride and use of a high electrolytic current preserved the chlorine concentration when the container was closed. When a solution was frozen for 168 hrs in a closed container and thawed, y=0.5251x−36.212 (r=0.919^**). Solutions that were preserved in an open container and then thawed had properties similar to those of a hypochlorite solution as defined in pharmaceutical legislation. If alkaline water was generated with a high electrolytic current, the thawed solution tended to be slightly alkaline. The ORP of a thawed solution changed from −849.2 to +224.94-301 mV.
 Conclusion: Acidic electrolyzed water that was frozen in an open container for 168 hrs retained sufficient antimicrobial potency. A frozen solution of alkaline electrolyzed water that was thawed had properties similar to those of alkaline water for cleaning.

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 Purpose: One step self-etching adhesives are becoming increasingly popular in clinical situations due to their convenience. Recently, so-called universal-type bonding agents, which are designed to adhere to not only dentin but also dental materials, have been developed. However, there have been only a few studies that compared the bonding ability of conventional one-step bonding agents and universal agents. This study investigated the bonding ability to dentin of a universal type of bonding agent that contains a newly-developed thiophosphoric acid ester monomer by means of transmission electron microscope (TEM) and micro tensile bond strength (μTBS) testing. The data of bond strength were analyzed by Student’s t-test.
 Methods: Twenty caries-free human third molars were used in this study. The tested bonding agents were G-BOND PLUS (GPL, GC), which is a conventional type, and G-Premio BOND (GPR, GC), which is a new universal type. We applied them on the flat dentin and built up Protect liner F (Kuraray Noritake Dental) for TEM samples and Clearfil AP-X for μTBS samples. The samples were subjected to TEM observation and μTBS testing respectively after 24 h water storage.
 Results: TEM images of both GPL and GPR showed a typical good interface between dentin and resin without any gap. There was no significant difference in μTBS between GPL (41.35±15.24 MPa) and GPR (44.09±12.84 MPa).
 Conclusion: The newly-developed universal bonding agent had no significant difference compared to the conventional one, and so provides adequate performance for clinical treatment.

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 Purpose: This study comprehensively assessed the mirror-polished surface characteristics of the various latest composites, examining the correlation between surface roughness, glossiness, color change and contact angle, and evaluating the bonding state between fillers and matrix resin under alkaline conditions.
 Methods: The following seven composites were used: Clearfil AP-X (AP), Estelite Σ Quick (EQ), Clearfil Majesty ES-2 (ES), MI Gracefil (GF), Filtek Supreme Ultra (FS), Clearfil Majesty ES Flow (ESf) and MI Fil (MF). The surface roughness (Ra), glossiness (%), color change (ΔE^*ab) and contact angle (θ) of the mirror-polished surface of each composite were examined, and the correlations between them were assessed (Tukey’s HSD test, Pearson’s correlation test, α=0.05). These composites with a mirror-polished surface were immersed in 0.1 N NaOH solution (60°C, pH 12.7) for 3 days. The deteriorated surface and cross-section were examined by SEM focusing on the structural changes.
 Results: EQ and MF exhibited lower surface roughness than ES and FS. The lowest glossiness was observed in AP and the highest change of color in FS (p<0.05) compared with the other composites. Surface roughness and glossiness, and surface roughness and color change, exhibited significant correlations (p<0.05). The alkaline deterioration test demonstrated small gap formation between filler particles and matrix resin, and exfoliation and falling of filler particles. These structural changes were observed with varying degrees depending on each composite.
 Conclusion: This study revealed that both the mirror-polished surface characteristics and the alkaline deterioration behavior of the various latest composites might be closely associated with type of filler, particle size and its distribution.

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 Purpose: Even if pulpectomy and infected root canal treatment have been performed carefully, retreatment may be necessary. In cases requiring retreatment, it is necessary to completely remove the root canal filling materials. Various instruments are used to remove such filling materials in the clinic. The purpose of this study was to evaluate the efficiency of instruments for removing these materials.
 Materials and Methods: GPR (2S, MANI), Reciproc (R50, VDW, Germany) and ultrasonic chip (ST21, OSADA) were used in this study. Thirty transparent root canal models (S1-U1) were prepared up to #60 at a working length of 18 mm. The condensed root canal fillings were treated using #60 gutta-percha point and root canal sealer. Root canal filling models were kept at a relative humidity of 100% and 37°C for more than one week. Prior to removal, root canal fillings were observed with standard images from four directions, then the root canals were masked. The root canal filling models were randomly divided into three groups, each with 10 models. Two operators removed root canal filling materials for five models in each group at a working length of 16 mm using each instrument. Completion of removal was confirmed when a #50 K file could be easily inserted to a depth of 16 mm. The times required for completely removing the filling materials from all models were measured. After removing the masking on the models, standard images were taken in the same manner as in pre-treatment. Removal rates for the filling materials on the root canal wall were calculated from the standard images. For each group, the time required for removal and the removal rate were compared using Student’s t-test, two-way analysis of variance and Scheffé’s F test.
 Results: The time required to remove the root canal filling materials using GPR was significantly shorter compared to Reciproc and ST21. A statistically significant difference was observed between GPR and both Reciproc and ST21 (p<0.05). There was no significant difference in the removal rate for root canal filling materials on the root canal wall between the experimental instruments.
 Conclusion: GPR efficiently removed the root canal filling materials during root canal retreatment compared to Reciproc and ST21.

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 Objective: Currently, major dental diseases include caries and periodontal disease. Periodontal disease affects about 80% of adults, and is the biggest factor for tooth loss in adults aged≥40 years. In order to recover lost tissues, it is necessary to obtain space to reconstruct healthy tissues, which has been performed by a barrier membrane technique. The barrier membrane technique is a therapy that allows the periodontium and the alveolar bone to regenerate in the space prepared with a membrane. This barrier membrane requires sufficient strength and biocompatibility for making the space, but a conventional polymer membrane is 200μm thick and has the drawbacks of being vulnerable and tending to cause bacterial infections. Thus, we conceived the development of a novel titanium barrier membrane that not only actively acts on cells to induce proliferation and differentiation but also reduces the risk of bacterial infections; we then compared the capacity to induce proliferation and differentiation of cultured cells of this membrane with that of a conventional membrane.
 Materials and Methods: An osteoblast-like cell line (MC3T3-E1) and HPL were sub-cultured for 3 to 5 passages for use in the experiment. Titanium with only 20μm through holes was used as a novel titanium barrier membrane; FRIOS was used as a reference. In the present study, cells were seeded on each sample to observe osteopontin (OPN) positive cells by fluorescent staining, measurement of cell proliferation, and observation with a scanning electron microscope (SEM).
 Results: By fluorescent staining, many OPN antibody-positive cells were observed in the novel titanium barrier membrane. Also, cell proliferation was significantly enhanced in the novel titanium barrier membrane compared with FRIOS. In SEM observation of the novel titanium barrier membrane, images showing that cells were gathered and incorporated into the through holes were observed in samples cultured for 1 week.
 Conclusions: In the novel titanium barrier membrane with through-holes at 50-μm intervals that was used in this study, expression of osteopontin, which is an index of cell differentiation, was observed. Based on the cell proliferation capacity, the novel titanium barrier membrane was considered to be superior to conventional FRIOS in terms of the capacity to induce cell proliferation and differentiation. Further investigation of the in vivo effect and strength of the novel titanium barrier membrane will be needed.

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 Purpose: Periodontitis is a chronic inflammatory disease caused by oral bacterial infection. In particular, Porphyromonas gingivalis is one of the principal bacteria involved in chronic periodontitis even though it does not have the ability to adhere firmly to tooth surfaces. On the other hand, Streptococcus mutans has the ability to adhere to tooth surfaces and colonize. The prevalence, progression, and severity of periodontitis all increase in individuals with diabetes mellitus. However, the effects of glucose on S. mutans and P. gingivalis have not yet been clearly evaluated. This study aimed to evaluate the effect of glucose on individuals and combinations of these bacteria involved in dental colony formation.
 Materials and methods: S. mutans was precultured on brain-heart infusion medium, and P. gingivalis was precultured on Trypticase Soy Broth supplemented with vitamin K, hemin, and dried yeast extract and grown at 37°C under anaerobic conditions. After preculture, S. mutans, P. gingivalis, and both strains (cocultivation) were diluted to an OD₆₀₀ of 0.3 in brain-heart infusion supplemented with glucose (5.5, 8, 12 or 24 mmol/l) for 48 h at 37°C under anaerobic conditions. The pH of the culture medium and the bacterial growth were analyzed.
 Results: High environmental glucose concentration led to a decrease in the culture pH and an increase in S. mutans growth. Under cocultivation, the total growth of S. mutans and P. gingivalis was greater than when either species was cultured individually, but the total decreased at higher glucose concentrations.
 Conclusion: The study suggested that high glucose concentration increased the growth of carious bacteria involved in initial colony formation. However, the periodontal pathogenic bacteria were not affected. Thus, many types of oral bacteria might not show increased growth and P. gingivalis growth is decreased by glucose concentration in severely diabetic patients. In summary, it is suggested that chronic periodontal disease in patients with severe diabetes mellitus depends more on the contribution of host factors than bacterial factors.

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