The purpose of this study was to compare the adhesiveness of chewing gum to acrylic resin, cobalt-chromium alloy, and zirconia. Test specimens were fabricated using acrylic resin (resin), cobalt-chromium alloy (Co-Cr), and Ceria stabilized tetragonal zirconia polycrystal-based nanostructured zirconia/alumina composite (zirconia). Specimens of each material were attached to the upper and lower terminals of a digital force gauge. The operator masticated chewing gum, wiped off any saliva, and placed the gum on the lower specimen. The gum was compressed to a thickness of 1 mm between the upper and lower specimens. Thereafter, traction was applied to the upper specimen at a cross-head speed of 100 mm/min under 3 different conditions (dry, wet with distilled water, and wet with artificial saliva) to determine the maximum adhesive strength of the chewing gum. The statistical analysis was performed using the Bonferroni test after a one-way analysis of variance (α=0.05). Under dry conditions, adhesive force was 14.8±6.8 N for resin, 14.0±4.8 N for Co-Cr, and 4.3±2.3 N for zirconia. Significant differences were noted between resin and zirconia, and between Co-Cr and zirconia. When distilled water was applied to the specimen surface, the adhesive strength was 16.8±1.7 N for resin, 8.3±2.1 N for Co-Cr, and 2.7±0.8 N for zirconia. Significant differences were noted between resin and Co-Cr, resin and zirconia, and Co-Cr and zirconia. When artificial saliva was applied to the specimen surface, the adhesive force was 18.5±2.8 N for resin, 5.3±0.8 N for Co-Cr, and 3.0±1.7 N for zirconia. Significant differences were noted between resin and Co-Cr, and resin and zirconia. Chewing gum adhered less strongly to zirconia than to acrylic resin or cobalt-chromium alloy.

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Application of nitrous oxide during anesthesia causes an increase in tracheal tube cuff pressure over time. The purpose of this study was to investigate the effect of an increase in cuff pressure on 3 types of tube (the Portex, Mallinckrodt, and Parker) commonly used for nasotracheal intubation. A cylindrical vessel was used to simulate a trachea. Cuff pressure was set at 0 cmH₂O (R0) or 20 cmH₂O (R20) at room temperature, or at 20 cmH₂O (H20), 40 cmH₂O (H40), 60 cmH₂O (H60), or 80 cmH₂O (H80) in 38°C hot water and pressure applied for 30 min. The value obtained at R0 was used as a reference (100%) and the rate of change under each condition determined. No change was observed at R20 in any of the 3 groups. In 38°C hot water, internal diameter in the Portex group decreased by 5.4% at H20 and 7.3% at H40, while that in the Mallinckrodt group decreased by 6% at H40. No significant change was observed in internal diameter in the Parker group, even when cuff pressure was increased. The internal diameter in the Portex group was the smallest at all cuff pressures in hot water. When the nasotracheal intubation tubes selected were placed in a simulated trachea and cuff pressure increased, internal diameter in the Portex and Mallinckrodt groups decreased.

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The aim of this retrospective study was to compare number of teeth lost among regular attenders (RAs), irregular attenders (IRAs), and problem-oriented attenders (POAs) at dental offices over a 10-yr observation period. Information on tooth loss was obtained from general practitioners. Patients were divided into 3 groups based on appointment adherence. A total of 1,886 teeth were lost in 1,400 patients. The mean number of teeth lost in men was 2.2±2.6 per patient over 10 yr in POAs, 1.2±1.7 in IRAs, and 1.5±1.5 in RAs. This number was significantly lower in IRAs (p = 0.011) or RAs (p=0.012) than in POAs. When the dependent variable was defined as “a patient with at least 2 or more extracted teeth”, the independent variables showed the following correlations with tooth loss: IRAs (OR: 0.54; 95%CI: 0.35–0.84), RAs (OR: 0.65; 95%CI: 0.47–0.89), man (OR: 1.43; 95%CI: 1.11–1.83), hypertension (OR: 1.38; 95%CI: 1.04–1.85), 20–25 present teeth (OR: 2.41; 95%CI: 1.81–3.22), and 1–19 present teeth (OR: 3.75; 95%CI: 2.73–5.16). The risk of tooth loss showed a 0.65-fold increase in RAs undergoing maintenance compared with POAs. Motivating patients to visit the dentist more regularly and undergo maintenance is important. The present results may be of use to dental professionals in providing patients with detailed information on potential tooth loss and associated risk factors with the aim of achieving such a change in behavior.

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Proper cleaning of the root canal is key to the success of endodontic treatment as it allows more effective diffusion of medication throughout the dentinal tubules. The aim of this in vitro study was to investigate the efficacy of 17% ethylenediaminetetraacetic acid (EDTA) in enhancing diffusion of hydroxyl (OH⁻) and calcium ions (Ca²⁺) throughout the root canal in primary teeth. The canals of 25 primary tooth roots were cleaned with endodontic files and 1% sodium hypochlorite. Three groups (G) were then established: GI, in which final irrigation was performed with 1% sodium hypochlorite; GII, in which 17% EDTA was used; and GIII, in which no irrigation was performed. The roots canals in GI and GII were filled with a calcium hydroxide-based paste labeled with the radioisotope calcium-45. Diffusion of OH⁻ was detected with pH strips and Ca²⁺ analyzed by measuring radioactivity in counts per min. Group II differed statistically from the other groups in diffusion of OH⁻ at 24 hr (p<0.05), but no significant difference among groups was found at the day 7 evaluation; GII also differed statistically from the other groups in diffusion of Ca²⁺ at 24 hr (p<0.05). These results suggest that application of 17% EDTA in primary tooth enhances diffusion of OH⁻ and Ca²⁺.

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The purpose of this study was to compare post-treatment stability in Angle Class III cases grouped by treatment modality into extraction, non-extraction, or surgical. Twenty-seven Angle Class III patients (9 men, 18 women) were selected from among the records of qualified retention cases treated at the Department of Orthodontics, Tokyo Dental College. The patients were divided into the following groups: Group 1, extraction (n=10); Group 2, non-extraction (n=9); and Group 3, surgery (n=8). Lateral cephalograms, panoramic X-rays, and study casts were obtained at baseline (T0), after active treatment (T1), and after retention (T2). The ABO Model Grading System (ABO) and Gottlieb’s Grading Analysis (GGA) were used as indices of occlusion, and the scores at each stage and differences in scores at T1 and T2 (|T1–T2|), defined as post-retention stability, recorded. Little’s Irregularity Index (IRI) from the study casts and the ANB from lateral cephalograms at T0, T1, and T2 were also recorded to assess post-treatment stability from a different perspective. The Kruskal-Wallis test was performed for statistical comparisons. Mean ranking according to the ABO and Kruskal-Wallis test at T1, T2, and |T1–T2| was lowest in Group 1 and highest in Group 3, and the mean amount of change in the ABO score after active treatment was also the same. This suggests that post-treatment stability is highest in non-extraction cases and lowest in surgical cases. This result correlated with change in the ANB from T0 to T1. This indicates that amount of change in the ANB affects post-treatment stability and that relapse will tend to be greater in surgical cases. However, the amount of change in IRI after active treatment was highest in Group 2 and lowest in Group 3, suggesting that relapse of the lower incisors is greatest in non-extraction cases.

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Multiple canals in the root are part of the normal morphology of the tooth. A canal may sometimes be overlooked, however, and this may lead to failure of treatment. The first step in successful endodontic treatment, therefore, is gaining access to the pulp chamber and locating all the canals. In order to achieve this goal, practitioners need to be familiar with all possible variations in root canal morphology, and should thoroughly explore roots to ensure that all canals are identified, debrided, and obturated. Here, we report the diagnosis, treatment planning, and endodontic management of a maxillary first molar with five root canals, including two distobuccal root canals, in a 22-year-old woman.

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Remarkable technological advances have been made in the field of medicine in recent years, one result of which is that a prenatal diagnosis of cleft lip and/or cleft palate (CL/P) is now possible. In this situation, it is extremely important to provide the parents with mental care from the moment they are informed. Here, we describe cases of CL/P treated at our hospital and how such a diagnosis and prenatal counseling are handled. A survey was carried out on 4 cases seen at our department between April 2013 and March 2014. Patients are referred to our department from local or our own obstetrics clinics on a prenatal diagnosis of CL/P based on findings from ultrasonography. If the case is a referral from outside, the patient will first be seen at our own obstetrics department. Our department may then be subsequently requested to provide the parents with prenatal counseling. Effort is made to reassure the parents that postnatal support will be provided, right from the start. Next, the multidisciplinary nature of the treatment process is explained. However, only the essential outline is given at first so as to avoid inducing unnecessary anxiety. A response is also given to any questions the parents may have. Our experience of giving such care leads us to believe that improvements are required in the way that explanations and assistance are provided. The number of cases in which prenatal counseling is required is expected to increase in future.

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