Bonding agents require sufficient strength for stable bonding in the mouth. Particularly, composite resin is often used even in the posterior region, so greater strength is needed. Bonding agents commonly consist of filler, resin monomer, catalyst, and other substances, but different bonding agents differ in composition and details of the composition are not published. Therefore, it is difficult to compare the correlation between the composition and strength and no method for evaluating the mechanical properties of different bonding agents has been established. Thus, the present study examined the mechanical properties of various bonding agents. The tensile bonding strength and fracture pattern in enamel and dentin for 15 commercial bonding agents were observed. In addition, for the different bonding agents in the same bonding system, the following were determined to examine the relationship among them: the content of inorganic filler; chemical composition analysis; indentation hardness; and thin-film adhesion strength (scratch test). As a result, the tensile bond strength of the bonding agents on the enamel ranged from 4.5 to 13.2 MPa, and those on the dentin ranged from 5.8 to 13.2 MPa. The inorganic filler content of the bonding agents ranged from 0.0 to 43.5Wt%. Si, P and Al were the main components of the inorganic fillers, however, the bonding agents contained different kinds of inorganic fillers. These elements have high and low atomic numbers. The indentation hardness of the bonding agents ranged from 2.6 to 20.7, while those of the enamel and dentin were 83.8 and 44.8 respectively. The thin-film adhesive strength of the bonding agents ranged from 1.4 to 4.3N. Also the recurrence coefficients showed significant correlations (r=0.51, 0.58 and 0.49) with the tensile bond strength (dentin) and the inorganic filler content; the tensile bond strength (enamel) and the thin-film adhesion strength; the tensile bond strength (dentin) and the thin-film adhesion strength. These results suggested that the tensile bond strength of the bonding agents on the enamel and dentin depended on the strength of the bonding agents.

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After caries removal and cavity preparation for an adhesive restoration, large areas of the cavity floor are composed of caries-affected dentin, however previous studies have reported that the bond strength to caries-affected dentin was lower than that to normal dentin. The physical and chemical characteristics of caries-affected dentin are very different from those of normal dentin, due to a loss of mineral content during the carious process. Also, the characteristics of smear layers of normal and caries-affected dentin differ because the composition of a smear layer is generally similar to the originating tissue; thus, it is assumed that the smear layer in caries-affected dentin is enriched with organic phase, resulting from the loss of minerals. Sodium hypochlorite (NaOCl) is a nonspecific proteolytic agent that effectively removes organic compounds at room temperature. Therefore, pre-treatment of the smear layer with NaOCl could eliminate the collagen phase. The aim of this study was to evaluate the effect of pre-treatment of NaOCl with or without a reducing agent on the microtensile bond strength to normal and caries-affected dentin. Twenty extracted human molars with occlusal caries were used. The occlusal dentin surface was ground flat to expose normal and caries-affected dentin using #600 SiC paper under running water. The dentin surface including caries-affected dentin was treated with 6% NaOCl solution for 30s followed by application with or without aromatic sulfinate solution (Accel®, SunMedical) for 10 and 30s, or none (control). After rinsing off, the treated dentin surface was applied with Clearfil Mega Bond FA® (Kuraray Medical) according to the manufacturer's instructions and the crown was built up with resin composite. After storage in water for 24 hours, the bonded specimens were serially sectioned into 0.7 mm-thick slabs and trimmed to an hour-glass shape with 1mm² cross-section isolated by normal or caries-affected dentin, and then subjected to a micro-tensile bond test. Data were analyzed by one and two-way ANOVA, and post hoc test(Dunnett T3 and T-test, p<0.05). For the control group, caries-affected dentin showed a significantly lower bond strength of the self-etch system than normal dentin. However, NaOCl treatment of the dentin surface followed by application of a reducing agent before the bonding procedure improved the bond strength to caries-affected dentin, in which there was no significant difference between bond strength of normal and caries-affected dentin. The effect of the reducing agent on bonding to caries-affected dentin treated with NaOCl depended upon the application time.

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Intentional replantation has been performed for avulsed teeth caused by trauma, but can also be used to treat accidents such as perforations or refractory apical periodontitis that is unresponsive to conventional root canal treatment. We investigated changes in symptoms for patients who did not respond to conventional root canal treatment and received intentional replantation. The subjects were 30 patients with a mean age of 41 years (range, 13-68 years) who visited the Departments of Operative Dentistry or General Dentistry at Tokyo Dental College Chiba Hospital or Suidobashi Hospital, were diagnosed with chronic apical periodontitis, and did not respond to conventional root canal treatment. After obtaining informed consent, intentional replantation with apicoectomy was performed. The mean number of root canal treatments prior to the intentional replantation was 6.3, and root canal dressings such as phenol, formaldehyde, calcium hydroxide and calcium hydroxide/iodoform were used. Intentional replantation was performed as follows: after performing root canal filling by lateral condensation using gutta-percha points and hydroxyapatite root canal sealer, the affected tooth was removed, and about 1 mm of the apex was sectioned. In many patients, replantation was performed by subjecting gutta-percha on the cut surface to cold varnish. In 4 patients, after sectioning the apex, retrofilling was performed using cyanoacrylate resin cement followed by replantation. Shifts in postoperative symptoms were analyzed. All 30 patients complained of occlusal pain, percussion pain and apical discomfort before and during surgery. Symptoms improved postoperatively in 28 patients, and these patients remained asymptomatic once restorations were placed. In 2 patients, no changes in symptoms were seen before and after surgery, and the cause of symptoms may have been neurogenic rather than in the apex. Based on these findings, intentional replantation appears highly useful in patients diagnosed with chronic apical periodontitis unresponsive to conventional root canal treatment where the cause of pain is in the apex.

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In response to the demand for opaque resin for esthetic restorations in recent years, various kinds of opaque resin have become available. However, because an opaque resin itself has many kinds of color and various colorations tend to be produced due to some combination with the subsequently layered composite resin, it is difficult to decide the optimal combination for restoration instantly in the clinical practice. Since such difficulty may be avoided by developing an opaque resin with reduced coloration, we have investigated such vesins by using TP values as an index of background color shielding and permeability. In this experiment, the color of dentin in an abutment tooth which was prepared for full veneer crown of vital tooth was first determined and the shade was examined in order to obtain the standard color of opaque resin. An opaque resin of the standard color was prepared by adding three kinds of paint to a composite resin of which the filling rate of zirconia filler was changed. Onto these opaque resins, composite resin samples of Shade A1, A2, A3, A3.5, A4, B1, B2, B3, B4, C2 and C3 were placed and their TP values were determined by using a colorimeter of the contact-type tristimulus value direct reading style in order to obtain a unique opaque resin with minimum content of zirconia filler and the background color was shielded successfully. As a result, the following conclusions were drawn: 1. As for the dentin color of vital tooth, 4 out of 7 teeth examined showed A 3.5 in Vita shade. 2. The background color shielding effect of the opaque resin sample was increased in response to the increased filling rate of zirconia filler. 3. As for the background color shielding effect of layered samples, TP value of 2.0 or below was confirmed for all layered composite resins, provided that the opaque resin sample had A3.5 shade and 6% filling rate of zirconia filler. 4. Concerning the prediction of TP values for layered samples, it was suggested that TP values determined at different times during the course of layering could be predicted from TP values of opaque resin and composite resin samples.

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Bleaching methods for vital tooth currently performed in dental clinics can be roughly divided into three approaches including office, combination and home bleaching manipulations. The present study was performed in order to compare not only the bleaching effectiveness of different conventional techniques generally employed in dental practices on brown eggshell, but also to examine the influence of these techniques on the human dental enamel surface. Concerning the bleaching effectiveness, ΔL* was calculated from L* values obtained before and at arbitrary times after bleaching by means of a colorimeter that read the contact-type tristimulus directly for comparison. Furthermore, ΔE*ab was also calculated from L*a*b* values similarly obtained in order to examine a possible correlation between ΔE*ab and ΔL* and to propose a simplified method of expressing the bleaching effectiveness. As for the influence on the enamel surface, the surface roughness before and after bleaching was measured by a scanning probe microscope, using a human extracted tooth-derived enamel, and the influence of individual bleaching techniques on the enamel surface was then examined based on the ΔRa thus calculated. As a result, the following conclusions were drawn: 1. The macroscopic bleaching effect was found to be greater in the following order of office, combination and home bleaching. 2. Concerning ΔL* obtained from different bleaching techniques, the value was approx. 17.7 after one treatment and approx. 24.9 after 3 treatments in the case of office bleaching. In the case of combination the bleaching, ΔL* value was approx. 17.6 after one treatment, increased with repeated application of home bleaching, and finally reached approx. 19.4 after 14 treatments. As for the home bleaching, ΔL* increased gradually with repeated application but still remained around 6.5 even after 14 treatments. 3. A distinct correlation between ΔL* and ΔE*ab was confirmed at γ=0.90 or more for all bleaching techniques examined. 4. When the surface roughness expressed as ΔRa was examined by using a human extracted tooth-derived enamel, the value for office bleaching manipulation was significantly larger than those for combination and home bleaching manipulations. No significant difference was, however, observed between combination and home bleaching manipulations.

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Prevention and control of nosocomial infection by blood-borne infectious diseases has become an important issue in general dental clinics and the dental division of general hospitals to ensure the safety of medical services. Therefore, we have investigated the present circumstances on prevention and control of nosocomial infection for the dental association members. The purpose of this study was to investigate variation in understanding of "Standard Precautions" (SP) among the dental association member populations defined by responses to the questionnaire items. A questionnaire survey on prevention and control of nosocomial infection was conducted for 760 dentists, namely, all members of the dental association in Yamaguchi Prefecture. The questionnaire included 22 question items: an age of objective dentists, prevention and control of nosocomial infection in daily dental practice and dental office management, and so on. The collected data were statistically analyzed using Principal Component Analysis on Variance/Covariance Matrix (PCA), one-way ANOVA, and Student's t-test. The major outcomes were as follows: 1. The percentage of responses to the whole questionnaire was 25.5% (194 dentists out of 760). 2. The one-way ANOVA analyses demonstrated significant differences in understanding about SP among the subgroups defined by the principal component variables comprising four question items for practicing clinical methods of SP (p<0.05). Similar observations were obtained when we adopted other sets of four question items for understanding of blood-borne infectious diseases, method of sterilizing or disinfecting dental tools after use, and managing and operating the dental office as the variables for group definition (p<0.05). However, significant differences were hardly observed in the set of four question items for other countermeasures on infection control (p≧0.05). 3. The Student's t-test analyses demonstrated that the respondent subgroups indicating careful practices of infection control and younger generation for variables with the highest PCA scores in the first principal component, such as "wearing and exchanging gloves","treating patients with AIDS or tuberculosis","disinfecting impressions, cast models and wax bites","educating dental staff on prevention and control of nosocomial infection", and "an age of objective dentists", were significantly deeper understanding about SP (p<0.05). These results suggest that there were close relations between understanding of SP among dentists and practicing prevention and control of nosocomial infection, and that dentists who have a deeper understanding of the concept of SP might provide better prevention and control of nosocomial infection in daily dental practice and dental office management.

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External forces generate stress on teeth, but the shapes and sizes of stresses differ depending on the position. Stress is known to be large, especially on a cervical tooth surface. In this study, standardized box cavities were prepared at the cervical area of extracted human upper canines, and stress on the cavities was examined. The dimensions of the cavities were apico-gingival height 3.0 mm, mesio-distal width 5.0 mm, and depth 2.0 mm. A cavity of the same dimensions was prepared in the crown as a crown cavity, at the root as a root cavity, and at the cement enamel junction as a cervical cavity. The root of the experimental tooth was buried in a fixing ring using selfcuring resin, until the distance from the anatomical cervical line to the surface of the resin became 6.5 mm. The cavity was filled with light cured glass ionomer cement and the cement surface was coated with a layer of varnish. Four strain gauges were placed adjacent to the cavity margin (mesial, distal, gingival, incisal). A force of 3 kgf was loaded on the apex of the tooth at angles of 90 degrees and 45 degrees to the long axis of the tooth. The stress was measured before and after cavity preparation and also after glass ionomer cement restoration. The following conclusions were obtained. 1. The stress with the load at 45 degrees was greater than that at 90 degrees. 2. The stress with the load at dentin was greater than that at enamel. 3. All the stresses before the cavity preparation were compressive stress. 4. The crown cavity showed tensile stress on the gingival wall, regardless of the load direction, before and after cavity preparation and after filling with glass ionomer cement. 5. The cervical cavity showed tensile stress on the gingival wall, regardless of the load direction, after cavity preparation. 6. On the gingival and incisal walls, stress after cavity preparation was smaller than that before cavity preparation. Stress after filling with glass ionomer approximated the value before cavity preparation. 7. On the mesial and distal walls, stress after cavity preparation was greater than that before cavity preparation. Stress after filling with glass ionomer was approximately equal to that before cavity preparation.

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There are two divisions in our Department of Dentistry and Oral Surgery in Hyogo College of Medicine, namely the dentistry division and the oral surgery division. In this study, we examined trends of patients referred to the dentistry division. We made a detailed analysis of the trends by letters of medical information in fiscal 2006. The results were as follows: 1. The numbers of referred patients were 88 patients, 33 males (37.5%) and 55 females (62.5%). 2. 63 patients (71.6%) came from general practitioner clinics. 3. 36 patients (40.9%) had systemic disease. 4. 37 patients (42%) were endodontic difficult cases, and 13 patients (14.8%) had a diagnosis of unknown pain. 5. The males of 50 years old or over and females of 60 years old or over had a number of medical histories. 6. The major medical histories were allergic diseases (30 cases, 17.4%), cardiovascular diseases (27 cases, 15.7%), and digestive system diseases (18 cases, 10.5% ). 7. The prevalence among those aged 50 or over was 100% both in males and females. 8. The 14 patients (53.1%) out of 27 patients with cardiovascular diseases were 70 years old or over.

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A second mesiobuccal canal in maxillary molars is rarely identified in daily clinical practice, although reports have revealed a high incidence in nature. We report the identification of a second mesiobuccal canal in a maxillary first molar that was difficult to determine by the naked eye. In this case, the combined use of an operative microscope and an ultrasonic tip was useful to find the second mesiobuccal canal, whose orifice was found to be deeper than the original mesiobuccal canal orifice. Cleaning and shaping of this second mesiobuccal canal immediately induced the disappearance of the fistula. This confirmed that disinfection of the root canal system is essential to induce favorable healing. It should be noted that root canal treatment relying on the operator's experience using the naked eye and tactile sensation has limitations. For reliable root canal treatment, appropriate devices, such as an operative microscope for an enlarged field of view with a sufficient light source, and ultrasonic tips for efficient removal of calcified tissues in the canal, are indispensable.

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Drug-induced gingival overgrowth is a side effect observed in patients taking calcium channel blockers, anti-epileptic drugs or immunosuppressant drugs. Some reports had showed different mechanisms for the incidence of gingival overgrowth, and we recently showed that gingival overgrowth was caused by collagen accumulation via drug-induced inhibition of α2 integrin expression and collagen phagocytosis in gingival fibroblasts. However, the reason for the difference in the incidence of gingival overgrowth in the reports was unclear. Single polymorphism (SNP) is known to be a hereditary factor associated with the incidence of some diseases. We showed that α2 integrin +807C/T polymorphism was correlated to the incidence of gingival overgrowth, but was not directly related to that induction because +807C/T polymorphism does not result in the change of amino acid sequence, suggesting that other SNP near the +807 site may cooperatively affect the incidence of gingival overgrowth. In the present study, we investigated the association between incidence of gingival overgrowth and α2 integrin +1648 G/A polymorphism, which is a linkage disequilibrium for +807C/T. The subjects were 98 patients who took calcium channel blockers, phenytoin or cyclosporin A. Gingival overgrowth was evaluated by the standard of McGaw et al.. Peripheral blood samples were collected from 45 subjects with gingival overgrowth (case group) and 53 subjects without it (control group). Genome DNA was extracted from blood and the α2 integrin +1648 site was analyzed by sequencing. The genotype distribution of the +1648 G/A polymorphism showed that GG genotype was highly present in 95.6% and 88.7% of the case and control groups, respectively, and GA genotype was 4.4% and 9.4%, respectively, and AA genotype occurred in only one subject in the control group. The frequency of the +1648 G allele was 97.8% and 94.7% in the case and control groups, respectively, and that of the +1648 A allele was 2.2% and 5.3%. Significant differences were not observed between the two groups. This result suggests that the incidence of drug-induced gingival overgrowth is not associated with human α2 integrin +1648 G/A polymorphism, but may be associated with a cooperation of +807C/T and other than + 1648 G/A polymorphism.

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【Purpose】Recently, oral health has been reported to be related to ischemic heart disease, infective endocarditis, preterm low birth weight and pneumonia. We examined the relationship between oral health and heart disease by the panorama index (P.I.). 【Materials and methods】We performed oral examination and orthopantomography in 204 persons who consulted the dental department of Kyoto Prefectural University of Medicine between January 2003 and December 2007. We defined the experimental group as patients with a history of heart disease and the control group as patients without any disease. P.I. is the sum of CPI records and signs of dental infection, which is the number of caries, periapical radiolucencies, pericoronitis and root remnants. Comparisons between groups were made using the Mann-Whitney U-test. Differences were considered significant at p<0.05. 【Results】The experimental group consisted of 88 patients with an average age of 64.7±9.2 years old, whereas the control group consisted of 116 persons with an average age of 56.0±10.2 years old. The average P.I. of the experimental group was 6.8±0.2 and that of the control group was 6.0±0.2. Regarding P.I., the experimental group showed a higher index than the control group at all ages. Especially, the index was higher for patients in their 50's. 【Conclusion】We concluded that the P.I. might be useful for evaluating the risk of contracting heart disease.

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