Kazuhiro Tsuga

Prevalence of Torus Mandibularis in Young Healthy Dentate Adults

PURPOSEnThere have been only a few reports on the prevalence of torus mandibularis (TM) in young adult patients, and TM can have various adverse effects on oral and occlusal states in middle-age patients. This study was designed to determine the association between TM status and oral and occlusal states in young healthy dentate adults.nnnMATERIALS AND METHODSnThis was a cross-sectional study; the sample population included students at Hiroshima University (Hiroshima, Japan) who participated for practical education. The predictor variables in this study included oral symptoms (temporomandibular joint noise, tooth clenching and grinding, buccal mucosa ridging, dental attrition, and tongue habit), oral anatomy (occlusal vertical dimension), and oral function (average occlusal pressure, occlusal contact area, and maximum voluntary tongue pressure). The outcome variable was TM status (present or absent). Additional variables were demographic in nature and included age, number of residual teeth, body weight, and gender. These variables were compared among participants with and without TM using univariate analysis and multiple logistic regression analysis. Statistical analyses were carried out using SPSS Statistics 19 for Windows (IBM Corp, Armonk, NY); a P value less than .05 was considered significant.nnnRESULTSnOf 204 participants included in the study, 50% were men and 50% were women. The mean age was 22.4xa0±xa02.7xa0years. TM was present in 119 (58.3%). Multiple logistic regression analysis showed that TM status was associated with dental attrition and occlusal contact area (Pxa0<xa0.05).nnnCONCLUSIONSnThis study showed that TM was present in more than half the young healthy dentate participants and was closely associated with dental attrition and occlusal contact area. This study will provide readers with useful information to help prevent the development of TM before middle age.

Effect of laser groove treatment on shear bond strength of resin-based luting agent to polyetheretherketone (PEEK)

PURPOSEnThe mechanical properties of polyetheretherketone (PEEK) are ideally suited for fixed dental prostheses. However, PEEK typically has low adhesion strength to resin-based luting agent. This study assessed the shear bond strength between laser groove treated PEEK and resin-based luting agent.nnnMETHODSnA total of 230 specimens were randomly divided into five groups (n=46): no-treatment, air abrasion treatment, 100μm-deep, 150μm-deep, and 200μm-deep laser groove treatments. The surface roughness was measured, scanning electron microscopy was used to observe the specimen surfaces, and X-ray photoelectron spectroscopy (XPS) was used to analyze the surfaces. Each group was divided into four resin-based luting agent subgroups: Panavia V5, RelyX Ultimate Resin Cement, G-CEM Link Force, and Super-Bond C&B. After the resin-based luting agent was bonded to the specimens, the bond strength was measured using shear tests and the failure modes were assessed by stereomicroscopy. The surfaces were also observed by scanning electron microscopy (SEM) after the shear bond strength measurements. The data were statistically analyzed using a two-way analysis of variance and Tukeys honest significant difference test (α=0.05).nnnRESULTSnThe PEEK surface after laser groove treatment groups exhibited the highest mean Ra values. In the XPS analysis, the laser treated PEEK surface exhibited an effective surface composition for bonding with resin-based luting agent. The shear bond strengths for the laser groove treated samples were significantly higher (p<0.05) than those of the no-treatment and air abrasion treatment groups.nnnCONCLUSIONSnThe shear bond strength between PEEK and resin-based luting agent was substantially improved by laser groove treatment.

Effect of polymerization temperature on the properties of autopolymerizing resin

Statement of problem. The polymerization conditions of an autopolymerizing resin affect its physical properties, and at chairside, 3 different methods are commonly used: cooling in cold water, warming in warm water, and heating in hot water. However, the effects of polymerization temperature on the physicomechanical properties of autopolymerizing resin are unclear. Purpose. The purpose of this in vitro study was to determine the effect of polymerization temperature on the physicomechanical properties of autopolymerizing resin, including shrinkage, water absorption, surface roughness, amount of residual monomer, and flexural strength. Material and methods. The experiment was designed to simulate a direct technique commonly used for the fabrication of interim crowns. Autopolymerizing resin specimens were made according to the powder‐to‐liquid ratio recommended by the manufacturer and soaked in water at 13°C, 37°C, or 60°C for 2 minutes to mold the resin until polymerization was completed 4 minutes after mixing. Shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength were measured immediately after polymerization and after 1, 3, and 7 days in distilled water at 37°C. Differences among these properties among the 3 different temperatures groups were statistically analyzed by using 1‐way ANOVA and the Tukey honest significant difference test (&agr;=.05). Results. Shrinkage tests showed that the 13°C group had significantly lower shrinkage (P=.004 for 37°C and P<.001 for 60°C) than the other groups immediately after specimen preparation. The 13°C group had significantly higher surface roughness after 0 (P<.001 for 37°C and P<.001 for 60°C), 1 (P=.025 for 37°C and P=.012 for 60°C), 3 (P<.001 for 37°C and P<.001 for 60°C), and 7 days (P<.001 for 37°C and P<.001 for 60°C) than those in the other groups and significantly higher water absorption rates (P=.033 for 37°C and P<.001 for 60°C) than the other groups during the 7 days after fabrication. However, the 13°C group showed significantly higher weight percentage of residual monomers than the 60°C group at 0 (P<.001) and 1 day (P<.001). Finally, 3‐point bend tests showed that the 13°C group had significantly lower flexural strength at 0 (P<.001), 1 (P<.001), 3 (P<.001), and 7 days (P<.001) than the other groups. Conclusions. The temperature environment during dental chairside polymerization of the autopolymerizing resin affected the physicomechanical properties of shrinkage, water absorption rate, surface roughness, residual monomer, and flexural strength.

Change of Oral Conditions after Combined Use of a Tongue Brush and Toothbrush: A Pilot Study

Introduction: This pilot study compared the effect of tongue cleaning by using a tongue brush alone and the one of combined using a tongue brush and toothbrush. Materials and Methods: 20 healthy young men were studied. The effect of tongue cleaning was assessed according to the following three criteria, including a tongue coating index, H2S concentration and oral bacterial count. These criteria were applied after tooth brushing combined with tongue brushing and then compared with the data by using a tongue brush alone. To evaluate the need for ongoing combined oral cleaning, its effect was evaluated on the day after a 7-day cleaning regimen’s completion, and we compared it and the data obtained on the day before the study. Results: After using a tongue brush alone, the tongue coating index improved and the oral bacterial count decreased (p < 0.05). After combined oral cleaning with both a tongue brush and toothbrush, significant improvements were revealed for the three criteria (p < 0.01).While, no significant difference was observed in the tongue coating index, H2S concentration, and oral bacterial count between on the first day before cleaning and on the next day after the 7-day cleaning regimen completion. Conclusion: This study indicated that oral cleaning by using a tongue brush alone resulted in a minimal decrease in the oral bacterial count, but significant improvement was achieved by combined use with a toothbrush. The results also suggested the necessity of daily combined use of a tongue brush and toothbrush for maintenance of a healthy oral cavity. *Corresponding author: Mineka Yoshikawa, DDS PhD, Associate professor, Hiroshima University Institute of Biomedical and Health Sciences, Department of Advanced Prosthodontics, Kasumi 1-2-3, Minami-ku, Hiroshima, 734-8553, Japan, Tel: +81-82257-5677; Fax +81-82-257-5679; E-mail: mineka@hiroshima-u.ac.jp

A development of functional rehabilitation method for impaired mandibular movement. 1. Effects of repeated opening movements.

顎運動の不調を訴える顎口腔機能異常患者の一部には, 運動負荷を伴った訓練によるリハビリテーションやストレッチを応用することが有用である可能性がある.本研究は, 習慣的開口路および限界運動路における下顎運動の短期的な反復動作が, 運動範囲に与える影響を明らかにすることを目的として, 天然歯列を有する男性歯科医師8名を対象に選び, 習慣的最大開口, 矢状面内限界運動, 左右側方限界運動を反復して行わせた際の下顎切歯点, 顆頭点の運動軌跡を6自由度下顎運動測定器MM-JI-Eを用いて観察した.その結果, 習慣的開口路での最大開口量は運動の反復に伴って増加する傾向にあり, 最大開口量の増加する被験者では, 習慣的開口路での顆頭点の最大変位量が, 最大開口量の増加に伴って片側あるいは両側でわずかに増加する傾向がみられた.さらに, 切歯点における後方蝶番運動経路は被験者8名中5名で拡大し, 矢状面内限界運動領域も拡大がみられた.側方運動で作業側顆頭の後方変位量の増加は明らかではなかった.