The conventional method of teeth whitening, office bleaching, uses high concentrations of hydrogen peroxide (H₂O₂), which might have adverse effects on enamel, dentin and oral mucosae. The objective of this research was to evaluate and compare the effect on enamel surfaces of PYRENEES®(PYR), which shows bleaching effects by mixing titanium dioxide that has photocatalytic effects in the visible light range with about 1/10 the usual concentration of H₂O₂, and Hi Lite™ (HI) using a high concentration of H₂O₂. Three groups of five samples each of mirror-surface polished bovine enamel were prepared: the untreated (Cont) group, PYR group and HI group. The samples were treated with PYR or HI every week for 3 weeks using the whitening methods specified by the manufacturers. The samples were stored in distilled water between the whitening treatments. After completion of the treatment, the surface texture of the treated enamel surface was observed using a scanning confocal laser microscope and a scanning electron microscope and the arithmetic mean roughness was also measured. A point area analysis of calcium on the cross-sectional surface of the whitened enamel was performed using an electron probe microanalyzer. The surface free energy was calculated using a contact angle meter. The surface of the PYR group samples was smooth and similar to that of the Cont group. However, the surface of the HI samples was significantly rougher than that of the Cont group and appeared to be decalcified. In the calcium analysis, the PYR group showed the same results as the Cont group, but decalcification to a depth of about 30μm from the enamel surface was observed in the HI group. The contact angle with distilled water in the PYR group and HI group was significantly lower than that in the Cont group, while the contact angle with diiodomethane was significantly higher; the surface energy was also significantly higher. These results showed that the PYR-treated enamel surface was not associated with substrate changes and the surface was more hydrophilic due to the action of titanium dioxide. These observations suggest that the tooth surface immediately after PYR application is able to inhibit deposits such as plaque and stains.

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Mechanical stress and periodontopathogenic bacteria induce the production of inflammatory cytokines in human periodontal ligament cells. These cytokines cause periodontitis and influence periodontal tissue including the periodontal ligament. Recently, although it is reported that β-cryptoxanthin (β-cryptoxanthin; β-cry) containing Citrus unshiu inhibits alveolar bone absorption, there has been no report showing that it influences inflammation in the periodontal ligament as periodontal tissue that includes alveolar bone. In the present study, we investigated whether β-cryptoxanthin influences the cytokine production of human periodontal ligament in response to mechanical stress caused by pressure during physiological occlusion or Porphyromonas gingivalis. The hPDL cells were obtained from a healthy erupted maxillary third molar. Cells were cultured in DMEM supplemented with 10% FBS and seeded onto Petri dishes at a concentration of 1×10⁵cells/ml. β-cry was added to the Petri dishes (1×10^-7mol/l) and stimulated with mechanical stress (1 or 6MPa) (MS group) or P. gingivalis (1×10⁷CFU/ml) (bacteria group). IL-1β, IL-6, IL-8 and TNF-α were analyzed by RT-PCR and ELISA. Morphologic changes of hPDL cells were observed using an inverted optical microscope. The Ethics Committee of Kyoto Prefectural University of Medicine approved this experimental procedure. Regardless of the presence of β-cry, expressions of all inflammatory cytokines were detected, and the amounts of IL-6 and IL-8 were increased in the MS group and bacteria group. Furthermore, the amounts of IL-6 and IL-8 in the bacteria group were higher than those in the MS group. However, with the addition of β-cry to the medium, the amounts of IL-6 and IL-8 decreased in the MS group and bacteria group. Moreover, the ratio of change in cytokine production based on the addition/non-addition of β-cry was lower in the MS group than in the bacteria group. The morphology of hPDL cells did not change. These findings indicate that mechanical stress caused by pressure during physiological occlusion has a locally injurious property, and this property was weaker in the MS group than in the bacteria group. β-cry inhibited cytokine production in response to mechanical stress and periodontopathogenic bacteria in the periodontal ligament and mechanical stress has a stronger anti-inflammatory influence than periodontopathogenic bacteria. Ingestion of β-cry is usually useful for health maintenance and promotion, and it is possible that the anti-inflammatory properties of β-cry could be useful for drug development.

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It is well known that volatile sulfur compounds (VSC) are the major cause of oral halitosis. There are many deodorizing agents for bad breath, but there have been few reports on the effectiveness of each agent for suppressing VSCs. We used 99% mercaptoethanol as a source of the VSCs, and examined the effectiveness of the deodorizing agent Pancil®, which is a compound of persimmon tannin and trehalose, for decreasing oral malodor in vitro. Gas chromatography could detect the VSCs containing hydrogen sulfide, methyl mercaptan, and mercaptoethanol. The VSCs originating from mercaptoethanol decreased as the concentration of Pancil increased. In the 4% Pancil group, the concentration of VSCs was only 0.61% of that of the distilled water control group (p<0.01). It was clearly shown that Pancil strongly suppresses VSCs originating from mercaptoethanol.

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An in vitro study of the efficiency of conventional root canal irrigation using needle and syringe was carried out. Glass models with an artificial root canal (10mm long with apical diameter of 0.4 or 1.0mm) were used for visualization and recording with a high-speed imaging technique. Fluid movement was investigated by using glassbeads as a tracer. From the results, it was concluded that in the open-ended flat needles, it is necessary to modify the pushing-out speed depending on the needle-insertion depth and needle size to reduce the risk of irrigant extrusion. That is, a flat-ended needle (25G) should be placed 5mm from the apex for safe and efficient irrigation. On the other hand, in the side-vented needles, the direction of the aperture should be changed several times for effective irrigation. Fluid flow analysis using glass-beads and high-speed camera might be promising for evaluating the efficiency of root canal irrigation.

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Knowledge of circadian variations has led to a better understanding of the time-of-day dependent results of clinical tests for various diseases and the effects of medications. The highest intensity of a toothache associated with acute pulpitis tends to occur at night, but little is known about the relationship between biological rhythms and pulp sensitivity associated with acute pulpitis. This study investigated the circadian variation of pulp sensitivity associated with acute pulpitis. The sex, age, dentition, pain features, time of onset and daily routines (hour of rising, meal times, time of shower or bathing, and hour of going to bed) in 73 patients with toothache caused by acute pulpitis were determined by interview after they provided informed consent. The chi-square test and a regression analysis were used for statistical analysis. The majority of the patients with acute pulpitis experienced painful onset of the toothache during the period from evening to midnight and from 7:00 AM to 8:00 AM. No correlation was found between the time of onset and the daily routine in the patients that experienced onset of toothache between evening to midnight, while there was an interesting correlation between the onset of pain and the hour of rising in patients with onset of toothache from 7:00 AM to 8:00 AM. On the other hand, there were no correlations with sex, age and dentition in any of the patients with acute pulpitis. These results suggest that there is a circadian variation in patients diagnosed as acute pulpitis.

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The mechanism of the wear behavior of resin composites is complex and many studies have been conducted to clarify this phenomenon. Manufacturers have focused on filler loading, filler type, filler size, filler distribution and filler surface treatment in order to improve the wear resistance of resin composites. Recently, newly developed resin composites including nanofiller particles have been introduced in the market, but their wear behavior is not yet fully understood. The purpose of this study was to elucidate the wear behavior of nanofilled resin composites by using tooth brushing abrasion and impact-sliding wear testing. The results were as follows: 1. Filler loading, filler type and filler size of the tested materials were different, and they were classified into nanohybrid resin composites and nanofill resin composites. 2. From the results of the tooth brushing abrasion test, nanohybrid resin composites showed a significantly lower abrasion rate than nanofill composites. However, changes in the surface texture and surface roughness of nanohybrid resin composites significantly increased after the brushing test. 3. From the results of the impact-sliding wear test, nanohybrid resin composites showed a significantly lower wear rate than nanofill resin composites. From observations of the surface texture of antagonist, small scratches were found in the nanohybrid resin composites group.

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The purpose of this clinical study was to evaluate the effect and safety of a new in-office bleaching material containing visible light activating titanium oxide photocatalyst (TiON in Office, GC). Anterior teeth of 72 patients were selected at the University Hospital of Dentistry, Tokyo Medical and Dental University or Aichi Gakuin University Dental Hospital with the permission of each Institutional Review Board. After informed consent, teeth were bleached with TiON in Office by three times of application and photo activation according to the manufacturer's instructions. The lightness of the tooth before and after bleaching was measured by a visual assessment using the Vitapan Classical Shade Guide (Vita, Germany). One of the teeth of each patient was selected as being representative for the evaluation. The obtained data was statistically analyzed by the Wilcoxon signed-rank test (p<0.05). Every adverse event during and after the bleaching procedure was recorded. Although the bleaching effects varied among the patients, the lightness of the bleached tooth was improved in all patients and a statistical difference was found between before and after bleaching. Thirteen adverse events were observed: 11 were whiteness of marginal gingival by accidental contact with the bleaching gel, which was not accompanied by any patient discomfort and had recovered by the time of the next visit; one was gingivitis which seemed to have no relationship with the bleaching procedure; and one was a slight disorder of the upper lip after bleaching, which could have been a side effect of the testing material. Spontaneous pain or postoperative sensitivity was not found during and after bleaching. It was concluded that TiON in Office is safe and effective for vital tooth bleaching.

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The purposes of this study were to produce prototypes of new chemo-mechanical caries removal reagents that contained bromelain and orange oil and to evaluate their effectiveness and quality for caries removal and the influence on resin filling after caries removal. Sixty extracted human permanent teeth with cervical dentinal caries were used in this study. BO reagent I containing 10% bromelain and 10% orange oil and BO reagent II containing 10% bromelain and 20% orange oil were produced for this study. All specimens were classified into three groups and for each group either BO reagents or Carisolv were used to remove caries. After caries removal, all specimens in each group were divided into 5 non-EDTA and 15 EDTA treatment teeth. The cavity surfaces of 5 non-EDTA and 5 EDTA treatment teeth were observed by stereomicroscopy and scanning electron microscopy (SEM). Other specimens were filled with resin composite and 5 teeth were selected in each group, and then a micro-leakage test was performed. After the micro-leakage test, all samples were longitudinally bisected with a diamond saw disc, and observed by stereomicroscopy and SEM. Five residual teeth in each group were immersed in 4 N HCL to resolve dentin and the condition of their resin tag was observed by SEM. No significant difference in surface structure was found among the three groups. The surfaces of non-EDTA treatment cavities showed a remaining smear layer in all groups, while the smear layer had been completely removed after EDTA treatment. The results of the micro-leakage test of each group were also equivalent. Sufficient bonding between resin composite and dentin was confirmed in all groups by SEM. The time required for caries removal by treatment with BO reagents was shorter than that by Carisolv treatment where BO reagent II showed the statistically shortest time. The presence of resin tags was confirmed by SEM in all groups. These results indicated that BO reagents can remove caries and do not influence the bonding between resin composite and dentin. In conclusion, the new reagent, especially BO reagent II, is expected to be an effective agent for caries removal.

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