With the improved dentin adhesiveness of composite resin, the concept of traditional restoration treatment has been reconsidered, leading to the possibility of treatment without persisting with the cavity form. These improvements have also influenced the methods of cavity preparation, and various tooth abrading methods in addition to those using an air turbine and electric engine have been selected. Clinical applications of laser with less discomfort during tooth abrading or an approach by means of airbrasive have also been attempted in recent years. In the airbrasive method, the abrading of enamel, dentin and decalcified tooth structure is efficiently performed by changing the powder used and thus various powder preparations have been tried. Although alumina powder can quickly abrade not only dentin but also enamel owing to its excellent tooth abrading capacity, selective abrading of the affected tooth is difficult because of its superior abrading effect mainly on sound teeth but scarcely on decalcified tooth structure. In addition, alumina powder is a hard and chemically stable material and thus the scattered powder may affect the patient's, operator's or co-operator's health or the surrounding apparatus. In order to improve the efficacy of abrading decalcified tooth structure and the bio-safety of scattered powder, we conducted an experiment using sodium sulfite powder(S-01), a kind of food additive. In the experiment, the abraded depth obtained when alumina or S-01 powder was used for abrading sound or decalcified teeth was compared by using bovine teeth. As a result, S-01 powder seemed unsuitable for abrading sound teeth but suitable for selectively abrading decalcified enamel or dentin, suggesting its clinical usefulness. For clinical use, although it is difficult to remove the softened dentin under a full cast crown without grinding the margin of the crown, the airbrasive method using S-01 powder is suitable for such cases.

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The purpose of this study was to compare post-operative healing between sulcular triangular flap and Luebke-Ochsenbein(L-O)flap for apicoectomy with respect to marginal gingiva recession and scar tissue formation. The surgical areas of 51 teeth were recorded using an intra-oral camera to observe soft tissue healing at 1-, 3- and 6- month recalls. The marginal gingiva recession and scar tissue formation of the surgical areas were evaluated on postoperative photographs compared with pre-operative ones. The sulcular triangular flap design showed significantly more marginal gingiva recession than the L-O flap design(p<0.05). While the L-O flap design showed more scar tissue formation than the sulcular triangular flap design in horizontal incision(p<0.05), there was no significant difference between them in vertical incision. Scar tissue formation by the L-O flap and marginal gingiva recession by the sulcular triangular flap could occur after apicoectomy.

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Today, the dental microscope is recognized as one of the most useful tools for endodontic treatment, while lasers have been used for various purposes in dentistry. Laser irradiation under the dental microscope might enable more delicate endodontic procedures, however, the safety of using a laser under the dental microscope has not been sufficiently investigated. This study investigated the safety of laser use under the dental microscope. Nd:YAG laser, Er:YAG laser, and diode laser were irradiated at a power meter through laser eye protectors or a microscope, and transmitted laser energy was measured with the power meter. Laser irradiation (200mJ,10pps) was performed with an optical fiber or a contact tip (diameter=400μm) for 10sec. In the control experiment, three lasers were irradiated directly or through the eye protectors at the power meter positioned at a distance of 5cm from the fiber tip or the contact tip. In the main experiment, the fiber tip or the contact tip was positioned at a distance of 5cm from the objective lens surface of the microscope. The power meter was placed behind the eyepieces. Matched eye protectors for each laser were placed in front of the objective lens or between the eyepieces and the power meter. Laser energy transmitted through the microscope with or without the eye protectors was measured with the power meter. In each experiment, permeable energies were measured three times. The results obtained were as follows: 1. No transmitted laser energy was detected when matched eye protectors were used. 2. Mismatched eye protectors did not effectively shut out laser energy, especially for Nd:YAG and diode lasers. 3. Little or no transmitted laser energy was detected through the microscope even when no eye protectors were used. It was concluded that lasers could be used safely under the dental microscope. However, wearing matched eye protectors is indispensable to protect the eyes against accidental exposure to laser.

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The aim of the present study was to assess the efficacy of a sonic toothbrush(Sonicare® Elite)on plaque removal using different types of bristles. The subjects were 20 staff members with clinically normal gingiva without restorative materials or carious teeth. They were asked to stop all oral hygiene 48 hours before initiation of the study. The same subject brushed using each toothbrush(manual toothbrush:MT group, standard brush of Sonicare® Elite:SB group, minibrush of Sonicare® Elite:MB group)for two minutes a total of three times. Supragingival plaque was evaluated by means of O'Leary's plaque control record(PCR). The plaque removal rate was evaluated by the reduction rate of PCR score. Results showed that both the standard head and minibrush of the sonic toothbrush removed more plaque than the manual toothbrush, although the difference was not statistically significant. The standard brush head removed more plaque than the minibrush with no statistical difference. The standard brush head removed more plaque than the manual toothbrush especially in the upper jaw, lower incisors, and interproximal area. Both the standard brush head and minibrush removed more plaque in the upper molar area than the manual toothbrush. These results indicated that the sonic toothbrush has better plaque removal ability than the manual toothbrush, although no statistical difference was recognized between the standard brush and minibrush.

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Nowadays, the demand for esthetic dental treatment has become common amongst patients, especially for those cases of discolored teeth, in which bleaching is usually the first treatment choice. However, polymer-based tooth surface coating materials have recently been developed as an alternative to bleaching. The purpose of this study was to evaluate the optical characteristics of two tooth surface coating materials. The materials evaluated were WhiteCoat™(Kuraray Medical)and the experimental material SIR20209(Shofu). Each specimen was prepared with 1mm thickness and two different diameters, 5 and 10mm, respectively. The light transmittance, intensity distribution of the transmitted light, ΔE^*ab values between white and black background(translucency parameter, TP)and the contrast ratio were also measured. In addition, the specimens were observed under a scanning electron microscope(SEM). The findings of this study showed that SIR20209 had the highest translucency, whereas the opaque shade of WhiteCoat™ presented the lowest values of light transmittance, TP and contrast ratio. Moreover, the light transmittances of various shades of WhiteCoat™ were significantly lower than those presented by SIR20209. The intensity distribution of transmitted light showed a distinctive specular and diffuse transmission amongst the specimens. The Yellowish, Reddish, Whitish, Natural-0, BW0, and BW1 shades of SIR20209, and the enamel shade of WhiteCoat™, showed a strong component of light transmittance around 0 degrees. Some inorganic filler particles were observed with SEM in the surfaces of WhiteCoat™ and SIR20209.

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Recently, nosocomial infection has been regarded as one of the most crucial administrative issues in general dental clinics and the dental division of general hospitals. In the present study, we investigated the conscious ness of dental practitioners on the prevention and control of nosocomial infection in daily dental care. A questionnaire survey on the prevention and control of nosocomial infection was conducted on 744 dentists, namely, the members of the dental association in Yamaguchi Prefecture. The contents of a questionnaire were 12 question items: an age of objective dentists, the prevention and control of nosocomial infection in daily dental practice, and so on. The response data were collected and statistically analyzed using Spearman's ρ-test for the correlations among the responses for all question items. The major outcomes were as follows: 1. The response rate to the whole questionnaire was 24.2%. Followings were the alternatives with majority votes for the representative question items: Intelligibility of Universal (Standard) Precautions was "Unknowing"(43%), and wearing a cap and plastic apron was "Hardly wear"(62%). Thus, these data revealed that a number of dentists might not completely practice infection control when treating their patients. 2. As for hand washing, "Social hand washing and hygienic hand washing" were practiced by most of the respondents(61%), and in dental treatment for patients suffering from viral hepatitis, the most common response was "Performed"(95%). Thus, comparatively, most of the dentists seemed to understand the importance of infection control in daily dental practice. 3. However, the results of the correlation analyses demonstrated that younger dentists were negative toward wearing a cap and plastic apron, but were positive toward wearing and exchanging gloves, in case of practicing dental treatment for patients suffering from viral hepatitis. Furthermore, dentists with a clear perception about the importance of Universal(Standard)Precautions were generally positive toward wearing and exchanging gloves, and wearing a cap and plastic apron. These dentists were involved in treating patients with AIDS or tuberculosis, and were concerned about controlling aerosol and dust in the dental treatment environment. These results indicate that further enlightenment and training opportunities for dentists in the prevention and control of nosocomial infection, as shown in the FDI statement and CDC guidelines, might help improve the environment in general dental offices.

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The present study evaluated the effect of a calculus scaling gel on time in a double-blind, split-mouth clinical study of 21 subjects. The Volpe-Manhold calculus index was used to quantify the distribution and amount of calculus deposition on the lingual aspect of the mandibular 6 anterior teeth at baseline. The test or placebo gels were applied directly to calculus for 7 min and then washed off. After 1 week, the calculus index was recorded again and the time taken to complete the removal of supragingival calculus was recorded. The mean±S.D. V-M calculus index on the test gel side was 0.95±0.06 at baseline and 0.80±0.13 at the time of treatment. The mean±S.D. time taken to complete scaling was 32.4±3.69 seconds on the test side and 45.2±4.50 seconds on the placebo side. Using the Wilcoxon test, the V-M calculus index on the test gel side was significantly decreased at the time of treatment compared with at baseline. The mean time taken to complete scaling was statistically significantly different (p=0.049) between the test gel and placebo gel by the Mann-Whitney U-test The results of this study support the use of our calculus scaling gel as an adjunct to supragingival scaling.

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For the assessment of bleaching effect on vital teeth, various approaches have been performed in the clinical practice including subjective assessments before and after operation or objective ones using a measuring tool, and a number of reports have examined its clinical efficacies. However, it seems difficult to apply the clinical efficacy thus obtained solely as an index for evaluating the bleaching effect because of potential individual variations and/or differences in the degree of coloring. Even in the in vitro experimental model for bleaching, it was difficult to have evenly colored enamel with no individual variation within a relatively short time due to the structural property of enamel. Therefore, an alternative sample which can be used as a standard for evaluating the bleaching effect is desired. We have searched for a material capable of assessing the bleaching effect on vital teeth simply and distinctly. The present study examined whether or not brown eggshell is suitable as an index for evaluating the bleaching effect through examinations on the structure of brown eggshell, its altered colors in response to the use of ethanol or acetone, potential individual differences in the color of an eggshell, and altered colors in response to the state of eggshell or those with times. Altered colors before and after application were assessed on a color measuring scale by using an office bleaching agent. In consequence, it was confirmed that an eggshell usually has both good and poor light-permeable portions with individual variations irrespective of the kind of egg used. It was also suggested that the color shows no change in response to the use of ethanol or acetone and the color of an individual egg which was selected after light-permeable check was relatively homogeneous except for both apical sites. In addition, it was found that the determined color score differs according to the state of the eggshell, that is, moistened or dried state, and the color of the eggshell changes with time elapsed. However, a relatively stable result could be obtained by preserving the shell in a thermostatic chamber for one day after boiling. In an actual experiment using an office bleaching agent, a distinct difference was observed macroscopically and the L*a*b* values showed characteristic changes. In summary, it is suggested that a brown eggshell can be applied as a bleaching standard for evaluating the effect of vital tooth bleaching agent.

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We have developed a new root canal irrigation system: intracanal aspiration technique(IAT), where irrigants are aspirated through a needle positioned near the apical canal end. The application of IAT was limited to wide canals because 24G standard needles were used. The aim of this study was to develop newly designed aspiration needles for narrower canals in IAT. In Study 1, two types of newly designed aspiration needles with a tip diameter of 27G were used. The size of the basal part of Type 1 and 2 needles was equivalent to 21 and 23G, respectively. Twenty-one root canals were instrumented to #35 file size, and divided into three groups(Groups 1-3)of 7 teeth each. Seven root canals(Group 4) were instrumented to #50 file size. The roots were fixed in a plastic case and surrounded with normal saline agar colored by 1% acid red solution. In Groups 1, 2 and 4, each root canal was irrigated using IAT with aspiration needle of Type 1, 2 and 24G, respectively. Each needle was connected to a Root ZX™® and positioned 2 mm from the apical root end. In Group 3, root canals were irrigated conventionally. Each canal was irrigated with 9ml of 14% EDTA for 3 minutes, and then with 6ml of 6% NaClO for 2 minutes. The meter value of Root ZX™® during irrigation and the discolored area of agar around the apical root end were measured. In Study 2, the flow rate at -20kPa was measured with newly designed aspiration needles of 24G and 27G. In Study 1, indicated meter values of Root ZX™® for Groups 1, 2 and 4 were significantly closer to the apex than those of Group 3(p<0.05). Discolored areas in Groups 1, 2 and 4 were significantly smaller than those of Group 3 (p<0.05). The results of Study 2 suggested that the optimal needle for IAT may consist of a 23G basal part of 32.5 mm in length and 27G tip part of 5mm in length. It was concluded that the newly designed aspiration needles for IAT could be effective in the canal with the small apical diameter of 0.35mm.

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The purpose of this study was to evaluate the chronological color changes of adhesive resins. Four kinds of two-step self-etch adhesive systems (Clearfil Mega Bond, Mac Bond II, UniFil Bond, Imperva Fluoro Bond) and four singleapplication self-etch adhesive systems (Adper Prompt L-Pop, Fluoro Bond Shake-One, One-up Bond F and One-up Bond F Plus) were used. These adhesive resins were placed in a Teflon mold (6mm in diameter, 2mm thickness) and light irradiated for 20 sec. After curing, the specimens were stored in 37℃ distilled water for 30 days, then subjected to thermal cycling. Color change was measured using a spectro photometer and evaluated by the CIE L*a*b*. Evaluations were performed before irradiation, after irradiation, and after storage in water for 1, 7, 30 days and after thermal cycling. The results were as follows: 1. After light irradiation, b^* values decreased and L* and a* values produced the lowest color changes. 2. For Mac Bond II, UniFil Bond and Adper Prompt L-Pop, L* values changed after storage in 37℃ distilled water. 3. For Adper Prompt L-Pop and One-up Bond F, a* values changed after storage in 37℃ distilled water. 4. For Clearfil Mega Bond and Adper Prompt L-Pop, b* values changed after storage in 37℃ distilled water.

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During whitening procedures, not only teeth but also the restorative materials and periodontal tissue in the oral environment are exposed to the whitening agents. Although there have been several reports on the influence of whitening agents on restorative materials, controversial conclusions have been drawn. The purpose of this study was to investigate the effect of 30% hydrogen peroxide on color changes of three light-cured resin composites, Gradia Direct (GC), Filtek Supreme (3M ESPE)and Estelite Σ (Tokuyama Dental). Stained bovine teeth were prepared and resin composites were filled into the cavity. Resin composite columns were made as references. Then the specimens were soaked in 30% hydrogen peroxide, and color changes were evaluated using a Spectro-Photo Meter (CMS-35FS/c, Murakami Shikisai). From the results of this study, L* values of the filled resin composites as well as stained teeth increased significantly. It was concluded that the color changes of resin composites filled into the cavity depended on color changes of background teeth.

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If a lost molar due to periodontitis is left with no adequate prosthetic treatment and the lost time of vertical stop is further prolonged, a traumatic occlusion may be induced with a decreased amount of residual periodontal tissue and involved an easy movement of the tooth due to infraocclusion. When the dental condition is further progressed to occlusion collapse with a flare-out covering multiple teeth, a prosthetic treatment for lost teeth may become hardly performed in some cases in addition to the decreased esthetics. In such a case, an attempt of using an osseointegrated implant is often effective not only for restoring the occlusive function but also for reducing the excessive burden to a residual tooth. The patient was a 43-year-old housewife who had first visited our Meikai University hospital with a main complaint of unsuitable partial denture on June 9, 1999. At admission, she had 12 residual teeth with poor plaque control due to the failed treatment for 10 years or more. Her partial denture was considerably worn down with markedly decreased height. The diagnosis of chronic periodontitis with occlusion collapse was then made. While her occlusal function was attempted to recover by implant prosthesis, her oral esthetics was also improved by comprehensive periodontal treatment including periodontal plastic surgery.

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Pro Taper nickel-titanium rotary instruments may cause outer canal widening when used to prepare curved canals, which might affect the quality of root canal fillings. The purpose of this study was to compare the apical density of four obturation techniques when used in ProTaper-prepared simulated curved canals. Forty simulated canals with a 30-degree curvature in clear resin blocks were divided into 2 groups (n=20, each) and were prepared with the ProTaper system to a size #25/.08 taper (F2) or #30/.09 taper (F3). The canals in both groups were further divided into four groups (n=5, each) and filled using one of the four different gutta-percha root filling techniques: Thermafil (TF), single-cone obturation with a ProTaper point (PT) or a .06 taper point (06), and lateral condensation (LC) using a .02 taper master point. The blocks were sectioned horizontally at 0-, 1-, 2-, 3- and 5-mm levels from the working length, and the percentage of gutta-percha-filled area was measured in each cross-section with image analysis software. Data were analyzed statistically using analysis of variance and the Bonferroni Dunn test. Results demonstrated that: (1) TF showed a significantly higher percentage compared with all other techniques at the 5-mm level in both groups and 1- to 3-mm levels in the F3 group (p<0.05); (2) values for LC were significantly lower than those for PT and 06 at the majority of the levels in the canal (p<0.05); and (3) PT showed significantly higher values than 06 only at the 0-mm level in the F2 group (p<0.05). It was concluded that, under the conditions of the study, TF produced the largest percentage of gutta-percha-filled area followed by PT and 06, and LC yielded the smallest percentage.

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In the present study, we compared two thermomechanical compaction methods using low-temperature softened gutta-percha with regard to the frequency of periapical overfilling. 608 root canals of 578 teeth were endodontically treated and obturated by two thermomechanical compaction methods: low-temperature softened gutta-percha only (stand-alone method), or combination of the cold gutta-percha point with low-temperature softened guttapercha (combination method). Periapical lesions visualized in X-ray films of post-obturated teeth were classified according to their lesion size and lesion type, and the relationships between the frequency of the periapical overfilling and the size or the type were analyzed. There was no relationship between the lesion size and the frequency of the periapical overfilling, whereas a significant relationship was observed between the type of lesion and the frequency of the periapical overfilling. The rate of periapical overfilling in cases obturated by the combination method was significantly lower than in cases obturated by the stand-alone method. These results suggest that the condition, not the size, of the periapical lesion may be a major factor related to the periapical overfilling of obturation materials, and the obturation method with the combination of lateral condensation with low-temperature softened gutta-percha was efficient regarding the condition of periapical lesions.

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The so-called gutter shaped roots were described for the first time in the literature of Japan by Nakayama (1941). The reported incidences of such teeth were 28.9% in the mandibular second molars and 10% in the mandibular third molars. The root configurations of these teeth are represented by fusion of the mesial and distal roots at the buccal aspect, and a deep furcation groove on the lingual root surface. In some of these teeth, the root canal system has complex morphology. The C-shaped canals are the most common, and may be difficult to debride and fill properly. According to Lowman et al. (1973), the incidence of accessory canals in the coronal and the middle third of the root surface was 55 % in maxillary molars and 63 % in mandibular molars. The existence of inflamed lateral or accessory canals often complicates the progress and treatment of pulpperiodontal disease. In the literature, the presence of accessory canals in the furcation areas of gutter shaped teeth has not been studied well. This study investigated the presence and morphology of furcation accessory canals in the interconnection between the mesial and distal roots using microfocus X-ray CT(SMX-100CT, Shimadzu). A total of ten extracted adult human teeth (9 mandibular second molars and 1 mandibular third molar) with gutter shaped roots were prepared. The teeth had been stored in 10% formalin solution. The age, sex of the patients and reasons for extraction were not recorded. Micro-CT findings revealed that accessory foramina extending from the pulpal floor to the interradicular region of the teeth were not located in the furcation of the roots. The present results suggested that a noticeable intermediate furcation ridge between each root of the interradicular area might not be seen at all and the so-called lateral canals might most often extend from the middle and apical region of the roots to a major root canal on 3D reconstruction.

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