The purpose of this study was to evaluate the correlation between bond strength and cavity wall adaptation. Cylindrical cavities, 1mm deep and 3mm in diameter (C-factor=2.3) were prepared on flat bovine dentin surfaces. The teeth were restored with the Clearfil SE Bond (Kuraray Medical) adhesive system followed by Photo Clearfil Bright (PB, Kuraray Medical) hybrid composite or Filtek Flow(FF, 3M ESPE) flowable composite. The resins were light-cured with 600mW/cm² for 40s. After storage for 24h, the teeth were sectioned to a thickness of about 1mm. The remaining dentin thickness (RDT) was measured. The slabs were trimmed (ca. 1mm²) at the adhesive-dentin interface for the micro-tensile bond strength (μ-TBS) test. The trimmed specimens were mounted on a testing apparatus, and stressed to failure under tension at 1mm/min in an EZ test machine. Bond strength and RDT data were analyzed using one-way ANOVA and Fisher's PLSD test. The dye penetration test was carried out on the cut surface. Dye penetration length was calculated as a percentage of the total cavity wall length. Dye penetration scores were analyzed using the Kruskal-Wallis test and Mann-Whitney U test. The flowable composite significantly improved resin composite adaptation to the cavity wall (p<0.05). However, the tensile bond strength of the flowable composite to the dentin cavity floor was significantly decreased (p<0.05). There was no correlation between resin composite bond strength and cavity wall adaptation for the dentin cavity.

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Ammonium hexafluorosilicate (SiF: (NH₄)₂SiF₆) was prepared in order to overcome the tooth discoloration caused by diamine silver fluoride (Saforide®). In our previous study, a constant concentration of SiF solution (9,000ppm) was used to compare its fluoridation effect with that of acidulated phosphate fluoride (APF). Therefore, the effects of the concentration of SiF solution on the occlusion of dentin tubules and composition of the precipitate remain unclear. Thus, the aim of this study was to evaluate the effects of changing the concentration of SiF on its clinical application as a dentin hypersensitivity treatment. Several SiF solution concentrations (from 100 to 19,400ppm) were prepared. Occlusion after treatment with these SiF solutions was evaluated using human dentin disks. The surface of dentin disks was observed using scanning electron microscopy (SEM). Also, the composition of the precipitate formed in dentin tubules after being treated with the SiF solutions was analyzed with energy dispersive X-ray microanalysis (EDXA). SEM observation showed that open dentin tubules were completely occluded irrespective of the concentration of SiF solution. EDXA analysis showed that the Ca/P molar ratio of the precipitate formed in the dentin tubules after SiF treatment gradually increased from 1.5 (100ppm SiF solution) to 2.1 (19,400ppm SiF solution) with the concentration of SiF solution. It was concluded that the occlusion of dentin tubules upon SiF treatment was the same irrespective of the concentration of the SiF solution. However, the composition of the precipitate formed in dentin tubules was governed by the concentration of the SiF solution.

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The purpose of this basic study using models of intracanal broken instruments was to evaluate the time for removal of broken file pieces depending on the output strength of the ultrasonic device, the lengths or sizes of broken files, and the presence or absence of water coolant. After enlarging the root canals in transparent resin blocks using Peeso reamers at root canal areas and files at apical areas, cut K-files as broken files were pushed into resin blocks, and models of intracanal broken instruments were reproduced. In the experiment on the relation of output strength of the ultrasonic device, the frequencies of 28.8 (strength 1), 29.6, and 30.4kHz were used for removing #30 broken files of 3mm length. In the experiment on the relation of broken piece lengths, the ultrasonic device with strength 1 was used for removing #30 broken files of 3, 5, or 7mm length. In the experiment on the relation of sizes of broken pieces, the ultrasonic device with strength 1 was used for removing #20, 30, or 40 broken files of 3mm length. In the experiment on the relation with or without water coolant, the ultrasonic device with strength 1 was used for removing #30 broken files of 5mm length. All times to remove broken files were compared and discussed. Regarding the output strength of the ultrasonic device, stronger output power was more effective for removing broken files. Regarding the lengths of broken files, longer lengths were more difficult to remove. Regarding the sizes of broken files, bigger pieces were more difficult to remove. Regarding the presence or absence of water coolant, the presence of water coolant was more effective. It was suggested that removal of broken pieces closely depended on the conditions or status, because the times to remove broken files varied reasonably closely with the conditions or status of the ultrasonic device using transparent resin blocks.

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Sonic and ultrasonic scalers are frequently used for periodontal debridement. It is well known that the shapes of scaler tips, applied pressure, and amplitude range affect the roughness of the tooth surface after scaling. Nowadays, sonic scalers with tunable output power are also available. The clinical technique employed for calculus removal using these sonic scalers also affects the roughness of the tooth surface and the removal of calculus. The purpose of this study was to examine how the shapes of scaler tips and the manner in which this new sonic scaler is used affect the morphology of root surfaces and the removal of calculus. First, flat and smooth dentin specimens (3×3mm) were prepared from extracted teeth, and scaling was performed for 30 seconds under 16 conditions using Air Solfy (J. Morita) and a hand scaler. The control was left untreated. After scaling, the roughness of the specimens was measured with a profilometer, and the morphology of the specimens was examined by SEM. Then, 3×3mm specimens were prepared from extracted teeth with a similar amount of calculus; scaling was performed with two Air Solfy scalers having different tips under three combinations until the test surface appeared smooth and clean on visual inspection, and the instrumentation time was recorded. The following results were obtained: (1) The degree of surface roughness was significantly higher when the tip of the scaler was spherical. (2) The power setting had no effect on the degree of surface roughness when the applied pressure was low; when the power setting was high, however, the surface roughness increased. (3) The degree of surface roughness after scaling with Air Solfy was lower than that after scaling with a hand scaler under most conditions. (4) SEM micrographs revealed that smooth and rough surfaces were intermingled after scaling with Air Solfy. (5) The time required for removal of calculus varied considerably according to the shapes of the scaler tips and the application conditions (p<0.05). Thus, we conclude that Air Solfy can be used to remove calculus with high efficiency and at minimum risk of root damage when the power setting and the applied pressure are high using the spherical tip for removing large amount of calculus, and when the power setting and the applied pressure are low using the straight tip for root planning.

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Caries detector differentiation of partially demineralized affected dentin: the action of organic acids of certain cariogenic bacteria-in vivo physiological remineralization occurs with time. Some reports suggest that certain bio-active adhesives may stimulate remineralization as well as provide long-term bonding durability. In this study, artificial lesions were restored with a bio-active ion-releasing agent and physiological remineralization of the resin-dentin interface below the in vitro carious lesions were measured for nano-hardness, compositional changes and SEM at 1 and 12 weeks. Class I cavities were placed throughout the teeth of six extracted human third molars. Each cavity was subjected to lactic acid and cariogenic bacteria (Streptococcus mutans). The in vitro caries was removed with a low speed round bur and the cavity was restored with one of two materials. Bio-active restorative materials Fluoro Bond Shake One and Beautifil Flow F02 including S-PRG (Surface reaction type Pre-Reacted Glass-ionomer) filler (SO) while Clearfil Mega Bond and Clearfil Majesty LV served as the MB-control. All materials were placed according to manufacturer's directions. After restoration, a hydrostatic Ringer's solution at a fluid pressure of 15cm H₂O was maintained to the pulp chamber of each tooth and stored at 37℃ in 100% relative humidity for either 1 week (1w) or 12 weeks (12w). After storage, each specimen was cut perpendicular to the resin-dentin interface and each half surface was polished. The nano-hardness site of each resin-dentin interface was measured using a 1mN load at each site at 5μm pitch from the cavity floor to 100μm and 100μm pitch from 100μm to 500μm. Each site was determined at 10 points in a horizontal direction with 3 measurements for each specimen. Nano-hardness compared t-test and one-way ANOVA, Tukey's test (α=0.05). The other cut half was assayed for its compositional elements using energy dispersive X-ray (EDX) and FE-SEM ultrastructural analysis. Nano-hardness of the resin-dentin interface compared SO to MB-control at 12w, from the interface to the 100μm, SO showed an increased hardness values against the MB-control. Additionally, we compared the SO resin-dentin interface at 1w and 12w, from the interface to the 100μm, 12w showed higher hardness values than 1w. EDX data indicates the rate of Ca and P of the MB-control was less than SO at 1w and 12w. Sr was found subjacent to the SO restorations, suggesting dentin remineralization of the in vitro lesion under the bio-active with S-PRG filler.

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The purpose of this study was to investigate the current status of minimal intervention dentistry (MID) in clinical practice. We surveyed 133 dentists working at Kyushu University Dental Hospital about MID. The questionnaire included color illustrations of two carious cavities: a small distal carious cavity in a mandibular second premolar (Case 1, an example of a vital tooth) and a large mesio-occlusal-distal cavity in a mandibular first molar (Case 2, an example of a non-vital tooth after root canal filling). The questionnaire asked: 1. Do you know about MID? 2. Do you intend to use MID to restore decayed teeth? 3. What kinds of restorations would you apply in cases 1 and 2, and why? Eighty-seven percent of respondents (116) had knowledge of MID; 69% and 27% of these respondents intended to use MID for vital and non-vital teeth, respectively. Of all 133 respondents, 59% and 23% selected restorations based on MID (MI restorations) for Cases 1 and 2, respectively. There was a positive relationship between the selection of MI restorations and MID recognition, and between the selection of MI restorations and the intention to use MID (p<0.05), except for the former relationship in non-vital teeth. The reasons respondents did not use MI restorations for vital teeth include: They were accustomed to treatment procedures for conventional restorations (restorations based on GV Black's concept) and prevention of recurrent caries and acquiring retention force. The reasons for non-vital teeth were prevention of tooth fracture and acquiring retention force. These results indicate that, in clinical practice, MID is used much less in non-vital teeth than in vital teeth. It was also suggested that MID recognition did not result in an increase in the clinical use of MID for non-vital teeth, but did so for cases of vital teeth. Therefore, further study is required to clarify the factors limiting the increased clinical use of MID for non-vital teeth.

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The aim of this study was to investigate the effects of Emdogain® gel on the wound healing of periapical tissues. Rat experimental periapical lesions were induced by opening the pulp chambers of the mandibular first molars and filing the distal root canals with #25 K-file. Exposed teeth were kept open to the oral environment for 7 days. Then, we irrigated the distal root canals and divided them into two groups. One was the EMD-treated group, and the other was the Propylene glycol alginate-treated group as the positive control, which was a carrier of Emdogain. The rats were sacrificed 7, 14 and 28 days after treatment and prepared for histochemical examination. In the EMD-treatment group, macrophages positive for TGF-β1 or BMP-2 rapidly increased in number at 7 days after treatment, then regeneration of cementum and bone tissues were observed around the root apex at 14 days after the treatment. Conversely, in the PGA-treated group, there were few macrophages positive for TGF-β1 or BMP-2, and recovery of apical periodontal tissues were rarely witnessed within the periapical lesions throughout the experimental period. These results suggest that reparative macrophages may be positive for TGF-β1 or BMP-2, and play an important role in the wound healing of apical periodontal tissue following the application of EMD.

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This article describes the endodontic treatments of two cases of chronic apical periodontitis with a root fracture or perforation, using an intracanal endoscope, which enabled a more accurate diagnosis. In addition, the combined use of an Er:YAG laser under endoscopic observation allowed a minimally invasive therapy. The intracanal endoscope might be a useful device in resolving endodontic problems, in combination with a cone beam computed tomography and operating microscope.

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The aim of this study was to evaluate final canal shape and total preparation time of ProTaper® rotary instrumentation on simulated S-shape canals using a crown-down preparation technique. Sixty root canals were prepared by six operators who had no experience of instrumentation with ProTaper®. The canals were instrumented with a #15K file and four ProTaper® instruments (SX, S1, S2, and F1). Pre- and post-instrumentation images were recorded with a microscope, and the canal shape was assessed by means of computer image analysis. The total canal preparation time was also measured. More material was removed on the inner wall than outer wall at the coronal and apical curvature, and the S-shape root canal curvature was shaped into a smoothly flared form. As the number of root canals prepared increased, preparation time was gradually decreased and after preparation of five root canals, it took less than 5 minutes. Five files were separated, and five cases of ledge formation occurred. ProTaper® instruments prepared curved canals rapidly and were relatively safe. These instruments may be effective for practice teaching sessions.

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Dentists usually remove cast restorations to prolong the life of the tooth by conservative treatment. However, as the removal of cast restorations is difficult and involves risks (tooth fracture or root fracture), it is necessary to remove cast restorations "speedily" and "surely", and to minimize the stress for patients in order to offer dental treatment "safely" ("3S"). Therefore, this study clinically investigated the methods of removing cast restorations which might attain the 3S. The subjects were patients who have visited Ouki Dental Clinic from May 21 to July 31 in 2009, and their cast restorations were removed by one of the following methods. We then evaluated the time taken to remove the cast restoration, tooth (root) fracture, spontaneous or percussion pain and so on. 1. Metal Crown: The tooth was grooved in the center of the buccal and occlusal side lengthwise by a #1/2 carbide bar for FG, then the tip of a flat-head driver was inserted into this groove and twisted slowly and gently, finally the metal crown was removed with Inlay and Crown Remover (CR, YDM). 2. Metal Inlay/Onlay: The tooth was grooved in the circumferential metal margin by a #1/2 carbide bar for FG, then the tip of an excavator was inserted into this groove and twisted slowly and gently for removal of the metal inlay/onlay. 3. Cast Post: The tooth was grooved at two locations, one on the buccal side and the other on the lingual side, on the metal core margin by a #1970 carbide bar for FG, then the two tips of Post and Core Remover (PR, YDM) were inserted into these locations and the cast post was slowly removed by gently clasping force of the PR. Almost all cast restorations were removed within 5 minutes [metal crown: 25/26, metal inlay/onlay 18/18, cast post: 18/18 (unit: piece)]. The average time for removing cast restorations was 133±82 (metal crown), 78±62 (metal inlay/onlay), and 103±77 (cast post) (unit: second); the removal time for metal inlay/onlay was significantly shorter than that for metal crown (Mann-Whitney U test, p<0.05). The average time for removing cast posts was 88±64 (front teeth), 93±78 (premolar teeth), and 133±91 (molar teeth) (unit: second), and the removal time classified by part was not significantly different (Mann-Whitney U test, p≧0.05). Using a #1/2 or #1970 narrow carbide bar for FG might decrease tooth matter minimally. Furthermore, using the PR for removing cast posts is unlikely to cause root fracture, spontaneous pain, percussion pain, periodontal pocket deepening and tooth mobility after removal. In particular, percussion pain, periodontal pockets (probing pocket depth) and tooth mobility more than one month after removing cast posts were significantly improved compared with before removal (Wilcoxon signed rank test, p<0.05). These results indicated that cast restorations might be removed speedily, surely and safely (3S).

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The efficacy of three newly developed toothbrushes with triangular, square, and round-shaped extremely tapered-end filaments were compared with a conventional round bristles toothbrush (Control: Cont.) on the stiffness of the tufted area of the toothbrushes as well as the influence on their clinical effectiveness for removal of plaque accumulation. A stiffness test was performed using an EZ Graph. The test was repeated five times for each toothbrush to determine whether the shape of the extremely tapered-end filaments of the bristles influences its stiffness. Five subjects participated in the clinical plaque removal study. The subjects then used a newly developed toothbrush at home for a week for familiarization purposes. The subjects were not instructed on how to brush, and refrained from brushing for 8 hours, followed by an assessment of dental plaque on a modification of the O'Leary plaque control record before and after each episode of brushing. The plaque removal efficacy was determined by the percentage of plaque score reduction in a single toothbrushing. As results, the average stiffness measurement was found to be 15.3N (triangular), 14.1N (square), 12.2N (round), and 46.0N (Cont.). The extremely tapered-end filaments of the bristles (triangular, square, round) showed no significant difference statistically. The mean for total plaque reduction for whole teeth was ranked 44.2% (triangular)>42.9%(square)>39.0%(Cont.)>21.5%(round). The triangular and square bristles resulted in improved plaque reduction compared to the Cont. design bristles. Further study is required to determine the efficacy of plaque removal by triangular and square bristles.

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Phosphoryl Oligosaccharides of Calcium (POs-Ca), which are produced by enzymatic digestion of potato starch, have been compounded into a dental gum (POs-Ca®, Ezaki Glico) for remineralization of enamel subsurface lesions because of its high solubility in water. However, there are few reports about the remineralization effects by POs-Ca in vivo. The aim of this study was to clinically evaluate the effect of chewing gum containing POs-Ca on remineralization and the micro-level structure change of enamel subsurface lesions in a human in situ model. The study utilized a double-blind, randomized design with two treatments: (i) gum containing 2.5% of POs-Ca, and (ii) gum containing no POs-Ca as the control. Twenty subjects wore removable oral appliances with insets of bovine enamel blocks containing demineralized subsurface lesions and chewed the gum for 20 minutes 3 times per day for 14 days. After each treatment the enamel blocks were removed, embedded, sectioned, and subjected to microradiography for measurement of the level of remineralization, as well as X-ray microbeam diffraction for measurement of the level of hydroxyapatite crystallites. The data was analyzed by t-test at a level of significance 0.05. The gum containing POs-Ca significantly facilitated the restoration of crystal content in comparison with POs-Ca free gum. Moreover, the hydroxyapatite crystallites of the restored region have the same orientation as the sound enamel. These results suggest that chewing gum that contains POs-Ca facilitates the restoration of early caries by remineralization, and further by recrystallization to a sound structure, which is refilled with uniquely oriented hydroxyapatite crystallites.

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