Job shadowing for early undergraduate dental students: Validation of educational effectiveness using structural equation modeling

This study aimed to evaluate and validate the educational effectiveness of a job shadowing class as a dental teaching programme for preclinical dental students through a questionnaire that assessed related student perceptions. A total of 124 preclinical (second year) dental students at Tokushima University participated in job shadowing placements from 2017 to 2019. Each student observed dental practice or surgery for 1 day in the university hospital. After shadowing, the students were requested to fill out a nine-item questionnaire based on a five-point scale. The first analysis was performed to calculate the correlation for each item. Furthermore, regression analysis for the categorical data was performed to show the relationship between eight questions (Items 1-8) and one question (Item 9: comprehensive evaluation). Next, factor analysis was performed to determine students' perceptions regarding the shadowing class. Ninety-eight students (response rate: 79%) completed the questionnaire. There was a strong relationship amongst Items 1, 8 and 9 ("interested in dentistry as a job," "learning motivation" and "comprehensive evaluation" respectively) based on the results of the correlation and regression analysis. The factor analysis led to three student perceptions as latent factors, namely, "Interesting," "Self-awareness" and "Future Goal," which had a relatively close inter-factor correlation (0.465-0.772). The finding suggests that job shadowing may increase a students' interest in a dentistry career at an early stage of their education and learning motivation, along with generating self-awareness. This programme may present possible educational effectiveness in dental education.


Sleep Quality and Comfort Reported by Sleep Bruxism Individuals Wearing the Occlusal Splint and Mandibular Advancement Splint: Revisiting Two Crossover Studies

To assess (1) whether the occlusal splint (OS) or mandibular advancement splint (MAS) allowed the best quality of sleep and was most comfortable; and (2) the relationship of sleep quality and comfort with the reduction in rhythmic masticatory muscle activity (RMMA) related to sleep bruxism (SB). Polysomnographic data of 21 SB subjects (25.6 ± 4.5 years), collected in two previous studies, were compared. Morning self-report data on sleep quality and comfort of the oral device, polysomnographic data, and RMMA index data from no-device nights were compared to data from nights using an OS or MAS. The reduction ratio of the RMMA index was calculated with the OS and the MAS. A responder to the oral device was identified when the RMMA index was less than 2, and when there was a reduction of at least 50% from the no-device night. Sleep quality reports on comfort of the oral device showed a mild advantage to the OS when compared to the MAS (r = 0.47, r = 0.32: P .01, respectively). The MAS induced a greater reduction on the RMMA index (P = .03) than the OS in responders. In the short term, the comfort of an oral device seemed to influence sleep quality in SB individuals. Despite the slightly higher degree of comfort offered by the OS, the MAS induced a greater effect on RMMA index.

The International Journal of Prosthodontics


Possibility and Future of Intraoral Scanner Application to Change the Method of Taking Impressions


Orthodontic Treatment Does Not Affect Frontal Sinus Development in Female Adults: A Clinical Study

Frontal sinus growth is gradual and lasts until post-puberty. However, the influence of biomechanical stimuli, such as orthodontic treatment, on frontal sinus development after the growth period has ended remains unclear. This study was designed to elucidate the impact of orthodontic treatment on the frontal sinus morphology of adult females. Sixty women were included and divided into three groups, based on the Frankfort mandibular plane angle. All participants underwent computed tomography and lateral cephalometry before and after treatment. Although two participants exhibited frontal sinus agenesis, most exhibited a bilaterally symmetric frontal sinus without fusion. The frontal sinus width and height were almost similar, irrespective of the vertical skeletal pattern, where the frontal sinus depth was significantly larger in the average mandibular plane angle group than in the low- and high-angle groups. Furthermore, the sinus volume in the low-angle group was likely smaller than that in the average and high-angle groups. On comparing pre-treatment and post-treatment measurements, minimal or no changes to the frontal sinus dimension were detected after treatment. In conclusion, orthodontic treatment did not affect frontal sinus development after the end of growth.


Relationship between oral parafunctional and postural habits and the symptoms of temporomandibular disorders: A survey-based cross-sectional cohort study using propensity score matching analysis

Temporomandibular disorders (TMDs) are a multifactorial joint disease of the masticatory system. The possible etiological factors involved in the onset and progression of TMDs include oral parafunctional habits (OPFHs) and postural habits (PHs). However, little information is available on the association between OPFHs and PHs and a predisposition to TMDs. Thus, to investigate whether the presence of OPFH and PH predisposes individuals to TMDs, a survey-based cross-sectional cohort study of self-reported TMD was performed. A total of 2292 patients with TMD were recruited for the survey. Through one-to-one propensity score matching, 166 patients with and without sleep bruxism (SB) were selected. The SB group had a significantly higher risk of masticatory muscular pain or fatigue than the non-SB group ( = 0.018). Furthermore, the SB group without other OFPHs and PHs did not show a significantly higher risk of TMD symptoms than the non-SB group. Diurnal clenching and bad posture also affect the stomatognathic system, causing pain or fatigue; however, it did not result in TMDs in patients without any OPFHs and PHs. This implies that OPFHs and PHs may increase the risk of TMD symptoms in coexistence with other habits.


Development of the Sphenoid Sinus in Japanese Children: A Retrospective Longitudinal Study Using Three-Dimensional Computed Tomography

The sphenoid sinus (SS) is located close to vital structures, such as the pituitary gland, and it has significant clinical relevance. This study aimed to clarify the growth pattern of the SS in Japanese children using three-dimensional computed tomography (CT). Seventy-eight participants with congenital, acquired, or external auditory canal cholesteatoma were recruited and underwent CT more than twice during their treatment. Using the volume-rendered images, the size and volume of the SS were measured. Furthermore, on the scout image, the morphological measurements of the cranial base were determined. The size and volume of the SS increased with age, and peaked at the mean age of 15 years. For males, the volume of the SS was smaller than that of females aged <5 years. The growth rate of the SS was significantly higher in males than in females. The maximum growth rate was detected at the age of 12 years for males and 10 years for females. For females, the increase in the length of the anterior cranial base ceased at approximately 10 years of age and remained constant thereafter. In contrast, for males, the length of the anterior cranial base increased gradually until 15 years of age. Considering the similarity of the periods between the adolescent growth spurt and the maximum growth rate of the SS, changes in the size of the SS may be used as an indicator of the physical growth spurt.


Volumetric Assessment of the Frontal Sinus in Female Adolescents and Its Relationship with Craniofacial Morphology and Orthodontic Treatment: A Pilot Study

International Journal of Environmental Research and Public Health


Oral appliances reduce masticatory muscle activity-sleep bruxism metrics independently of changes in heart rate variability.

Sleep bruxism (SB) is associated with physiological activities including sympathetic autonomic system dominance and sleep micro-arousal. While oral appliances (OA) are used to prevent SB harmful effects, the influence of OAs physiological mechanisms during sleep is unknown. The aim of this study is to assess whether heart rate variability (HRV) changes, as a marker of autonomic nervous system activity, would be associated with the OA mechanism of action on SB using occlusal splint (OS) and mandibular advancement splint (MAS). A retrospective analysis, from data previously collected in 21 participants with SB (25.6 ± 4.5 years) with polysomnographic recordings, was done. HRV data were compared between a reference night (no-device) and ones during which OS or MAS was used in a crossover study design. Rhythmic masticatory muscle activity (RMMA) index was compared between nights. HRV was evaluated using autoregressive model analysis for three sections: baseline (distance from RMMA), immediately before, and after RMMA period. A significant reduction in RMMA index, when wearing OA during sleep, was observed (P < 0.01), but was not associated with HRV parameters change. HRV significantly changed after RMMA onset for nights with OA during non-REM sleep in comparison with baseline (P < 0.02). The usage of OAs for SB participants reduced RMMA, but most likely independently of changes in HRV linked to the mechanism associated with SB genesis. Wearing OA seems to reduce grinding noise and protect from dental injuries but does not seem to influence SB genesis.


Longitudinal Morphological Changes in the Adenoids and Tonsils in Japanese School Children.

The adenoid (Ad) and tonsil (Ts), located in the upper airway, play an important role in immunological protection. These lymphoid tissues grow rapidly, reach a peak of growth at the age of 6-8 years, and decrease in their size thereafter. However, little information is available on the longitudinal growth patterns of Ad and Ts in the general population. This study aimed to evaluate the individual growth of Ad and Ts during childhood using lateral cephalograms taken longitudinally from the same individuals at the ages of 8-12 years. Our results showed that the cross-sectional areas of the Ad, nasopharynx (Np), and oropharynx (Op) significantly increased with age while small changes in the size of Ts were present throughout the study period. In addition, the values of Ad/Np and Ts/Op decreased significantly with age in the elementary school. Furthermore, there was a strong and significant correlation between the Ad/Np ratio and upper airway resistance, indicating the narrowest distance in the upper airway. In conclusion, the airway occupation in Np and Op increased with age due to the increase in the sizes of Np and Op but not the decrease in the sizes of Ad and Ts.


Immediate Effect of Masticatory Muscle Activity with Transcutaneous Electrical Nerve Stimulation in Muscle Pain of Temporomandibular Disorders Patients

Transcutaneous electrical nerve stimulation (TENS) is a non-invasive treatment modality for acute and chronic pain. However, little information for muscle activity is available on the immediate effects of TENS in masticatory muscle pain related to temporomandibular disorders (TMDs). The present study aimed to evaluate the immediate effects of TENS treatment on TMD-related muscle pain. Thirty-six patients with TMD-related muscle pain and 39 healthy subjects served as TMD and control groups, respectively. For objective evaluations, maximum mouth opening, and maximum bite force were measured before and after TENS. The pain intensity was assessed according to a 100-mm visual analog scale (VAS). TENS was applied to painful muscles for 20 min with frequencies of 100-200 Hz. The treatment outcome was evaluated using Global Rating of Change (GRC) scales. In the TMD group, VAS values significantly decreased after TENS. Although there was significant increase in the maximum mouth opening after TENS for only TMD group, the maximum bite force of both groups was significantly greater after TENS. According to GRC scales, one patient with TMD-related muscle pain expressed negative feelings after TENS. Conclusively, TENS treatment might quickly relieve pain in masticatory muscles and improve masticatory functions in patients with TMD-related muscle pain.


Evaluation of the measurement precision and accuracy in the dental CAD/CAM system

The purpose of this study is to investigate the precision and trueness of the occlusal contact record obtained with a dental CAD/CAM device (ARCTICA). Sandblasted spherical steel balls with diameters of 10-20 mm were measured using ARCTICA and a three-dimensional measurement device (FN503). The radius of each steel ball was calculated from the measured value and the difference between the measured and nominal values was obtained. Upper/lower dental arch casts were measured and processed for occlusal contact image creation using both devices. The graphical images of the occlusal contacts at the intercuspal position obtained from both systems and an occlusal analysis device (BE-1) were compared with the occlusal contact area. Excellent correlation was observed between the measurement results of ARCTICA and FN503 (p<0.001, R: 0.99). The occlusal contact areas were 186.0 mm (ARCTICA), 192.8 mm (FN503), and 196.1 mm (BE-1). This study showed that ARCTICA is capable of conducting highly accurate measurements and generating a graphical image of occlusal contacts with good reliability.


一次性および二次性舌痛症患者における睡眠障害の検討—睡眠質問票を用いた調査—

一次性および二次性舌痛症患者における睡眠障害の検討—睡眠質問票を用いた調査—


Quality of life and job satisfaction among female dentists in Japan


Investigation of behavioural factors which vary occlusal contact in Japanese dental students

The Journal of Japanese Society of Stomatognathic Function


Educational effects using a robot patient simulation system for development of clinical attitude

The aim of this study was to assess the effectiveness of improving the attitude of dental students towards the use of a full-body patient simulation system (SIMROID) compared to the traditional mannequin (CLINSIM) for dental clinical education. The participants were 10 male undergraduate dental students who had finished clinical training in the university hospital 1 year before this study started. They performed a crown preparation on an upper pre-molar tooth using SIMROID and CLINSIM as the practical clinical trials. The elapsed time for preparation was recorded. The taper of the abutment teeth was measured using a 3-dimensional shape-measuring device after this trial. In addition, a self-reported questionnaire was collected that included physical pain, treatment safety and maintaining a clean area for each simulator. Qualitative data analysis of a free format report about SIMROID was performed using text mining analysis. This trial was performed twice at 1-month intervals. The students considered physical pain, treatment safety and a clean area for SIMROID significantly better than that for CLINSIM (P < .01). The elapsed time of preparation in the second practical clinical trial was significantly lower than in the first for SIMROID and CLINSIM (P < .01). However, there were no significant differences between the abutment tapers for both systems. For the text mining analysis, most of the students wrote that SIMROID was similar to real patients. The use of SIMROID was proven to be effective in improving the attitude of students towards patients, thereby giving importance to considerations for actual patients during dental treatment.


Relationship between Frontal/Lateral Mandibular Translations and Masticatory Movement Based on Evaluation of Occlusal Surface Motion

Objective: This study aimed to clarify whether crown restorations with adjusted occlusal surfaces that were formed using frontal/lateral mandibular translations, functioned without interference during mastication.
Materials and Methods: In 10 adult volunteers who had healthy normal dentition, frontal and lateral border movement was measured during unilateral mastication and free mastication, using an ultrasound digital mandibular measuring system (ARCUS digma2). Additionally, precise impressions of the upper and lower dental arch were taken, and dental casts were made. These casts were measured using a CAD/CAM scanning system (ARCTICA). For the fabrication of crown restorations, the functionally generated path technique (FGP technique) was used on the monitor for the lower first and second molar. The movement of the opposite teeth on the occlusal surface during frontal and lateral border movement, during unilateral mastication, and during free mastication was considered the functional occlusal surface. The data of the functional occlusal surface generated by frontal/lateral mandibular translations and that of each of the masticatory functional occlusal surfaces were superimposed using three-dimensional data evaluation software (GOM). The difference between these surfaces was evaluated to determine the interference area, maximum interference difference, and average interference difference.
Results: Interference was present for all functional occlusal surfaces created by mastication as well as those determined by frontal/lateral mandibular translations. The average interference values, in order of free masticatory movement, habitual masticatory side, and non-habitual masticatory side, were as follows. Interference area: 167.5 ± 20.8 mm2, 121.9 ± 28.5 mm2, 144.6 ± 28.0 mm2; maximum interference distance: 345.0 ± 43.1 m, 189.0 ± 39.9 m, 309.0 ± 46.8 m; average interference distance: 130.0 ± 15.7 m, 64.0 ± 10.6 m, 130.0 ± 21.9 m. Statistically significant differences were found for the maximum interference distance and average interference distance (both p < 0.05).
Conclusions: The functional occlusal surfaces for each form of mastication demonstrated interference with the functional surface of frontal/lateral mandibular translations. Thus, crown restorations of which the occlusal surfaces were adjusted and formed by frontal/lateral mandibular translations may interfere with mastication.


咬合違和感の診断と対処法

咬合違和感の診断と対処法


Evaluation of School Dental Checkups in the Tokushima University Hospital Training Curriculum : Results of Questionnaire Survey for 10 Years

臨床研修プログラムにおける学校歯科健康診断研修の評価 10年間のアンケート結果から

The Journal of Japanese Dental Education Association

日本歯科医学教育学会雑誌


Mandibular movement during sleep bruxism associated with current tooth attrition

Observation of attrition patterns suggests that mandibular movement in sleep bruxism (SB) may be associated with current tooth attrition. The aim of this study was to confirm this phenomenon by investigating mandibular movement and masseter muscle activity. The subject was a healthy 21-year-old Japanese male. We recorded biological signals including mandibular movement and masseter electromyograms (EMGs) with a polysomnograph. Based on the EMG using Okura's criteria, SB events were classified into clenching, grinding and mixed types according to mandibular movement criteria. The close-open mandibular movement cycles (CO-cycles) during grinding and mixed type events were selected based on mandibular movement trajectories. Fifty-eight CO-cycles were selected in seven grinding and three mixed types. We found that SB mandibular movements associated with current tooth attrition. Excessive lateral movements (ELM) beyond the canine edge-to-edge position were observed in the closing (10.3%) and opening (13.8%) phases of the CO-cycle. Total masseter muscle activity was significantly higher during voluntary grinding (VGR) than during CO-cycle including ELM (working side: P=0.036, balancing side: P=0.025). However, in the middle and late parts of the opening phase, working side masseter muscle activity was significantly higher during CO-cycle including ELM than during VGR (P=0.012). In the early part of the closing phase, balancing side masseter muscle activity was significantly higher during CO-cycle including ELM than during VGR (P=0.017). These findings suggest that excessive forceful grinding during ongoing SB events may have caused canine attrition in this patient.


The effect of splints on sleep bruxism : a preliminary study

スプリントによる睡眠時ブラキシズムに対する治療効果 : 予備的検討

The Journal of Japan Association of Oral Rehabilitation

日本口腔リハビリテーション学会雑誌


A Retrospective Clinical Evaluation of the Survival of Dental Implants in Combination with Sinus Floor Elevation at 3 Years

上顎洞底挙上術を併用したインプラントの3年経過後の臨床的評価

The purpose of this study was to evaluate the risk factors for the loss of implants with sinus floor elevation. We statistically carried out a clinical examination on 49 cases, 80 implants at 3 years after the fitting of implant-anchored fixed prostheses.
The results are summarized as follows:
1. Two implants failed in 80 implants, indicating survival rates of 97.5%.
2. There was no statistically significant difference between implant placement timing, initial bone height, sinus membrane thickness, type, diameter, primary stability of implants and graft materials used for sinus floor elevation.
3. The length of implant affected the survival of implants used for sinus floor elevation.

Journal of Japanese Society of Oral Implantology

日本口腔インプラント学会誌


インプラント体の表面性状の違いが周囲骨吸収に及ぼす影響:埋入後5年経過時の同一患者の隣接するインプラント体により比較

日本口腔インプラント学会誌


Durability of Bond Strength Between Titanium and two PMMAs

Reserach & Reviews: A Journal of Dentistry


Sleep bruxism and oromandibular myoclonus in rapid eye movement sleep behavior disorder: a preliminary report.

In the presence of a high frequency of rhythmic masticatory muscle activity during REM sleep, RBD may be suspected and further neurologic assessment is recommended.

The rhythmic masticatory muscle activity index was significantly higher during REM sleep in iRBD subjects compared to controls (P<.01) and was significantly higher during non-REM (NREM) sleep in both subject groups compared to controls (P⩽.03). A positive sleep laboratory diagnosis of sleep bruxism was made in 25% of all patients. In iRBD, patients had more OMM during REM sleep than controls (2.4 times higher; P=.01).


Sleep less and bite more: Sleep disorders associated with occlusal loads during sleep.

Occlusal overload during sleep is a significant clinical issue that has negative impacts on the maintenance of teeth and the longevity of dental prostheses. Sleep is usually viewed as an 'out-of-functional' mode for masticatory muscles. However, orodental structures and prostheses are not free from occlusal loads during sleep since masticatory muscles can be activated at a low level within normal sleep continuity. Thus, an increase in masticatory muscle contractions, by whatever the cause, can be associated with a risk of increased occlusal loads during sleep. Among such conditions, sleep bruxism (SB) is a type of sleep-related movement disorders with potential load challenge to the tooth and orofacial structures. Patients with SB usually report frequent tooth grinding noises during sleep and there is a consecutive increase in number and strength of rhythmic masticatory muscle activity (RMMA). Other types of masticatory muscle contractions can be non-specifically activated during sleep, such as brief contractions with tooth tapping, sleep talking, non-rhythmic contractions related to non-specific body movements, etc.; these occur more frequently in sleep disorders. Studies have shown that clinical signs and symptoms of SB can be found in patients with sleep disorders. In addition, sleep becomes compromised with aging process, and a prevalence of most sleep disorders is high in the elderly populations, in which prosthodontic rehabilitations are more required. Therefore, the recognition and understanding of the role of sleep disorders can provide a comprehensive vision for prosthodontic rehabilitations when prosthodontists manage complex orodental cases needing interdisciplinary collaborations between dentistry and sleep medicine.


A case of occulsal recontraction that enabled the release of temporomandibular joint noise and masticatory disturbance

咬合再構成により顎関節雑音を消失させ咀嚼障害が改善した症例

Patient: A 60-year-old male complained of reciprocal clicking on the bilateral temporomandibularjoint (TMJ) and masticatory disturbance. A treatment denture was fabricated for the missing mandibular right molars. This denture was inserted to improve occlusal vertical dimension and for protrusive repositioning of the mandibular position. After improving the main complaint and a follow-up, we planned occlusal reconstruction with fixed prostheses and removal denture for the final prosthetic treatment.Discussion: The provided occlusal reconstruction could release masticatory disturbance with temporomandibular joint disk displacement. In this case, a modification of the mandibular position with a prosthetic appliance was effective treatment.Conclusion: Occlusal reconstruction and bite rising were applied to the patient with reciprocal clicking of the TMJ. Although he made satisfactory progress, long time follow-up with periodic and prosthodontic examination will be required in the future.

症例の概要:患者は60歳の男性で，両側の顎関節雑音と咀嚼障害を主訴に来院した．下顎右側大臼歯欠損部の補綴治療と下顎前方整位および咬合挙上を目的とした治療用義歯を作製した．主訴の改善を確認し，経過観察を行った後，歯冠補綴と部分床義歯による咬合再構成を行なった．考察:食事に支障をきたしていた復位性関節円板前方転位症例に対して，下顎前方位での咬合再構成を行い良好な治療経過が得られた．本症例に対する咬合再構成は治療法として適切な選択であったといえる．結論:両側性の相反性顎関節雑音症例に対し，咬合挙上と下顎前方位での咬合再構成により，症状が改善した．今後さらに十分な経過観察が必要である．


Stress analysis in human temporomandibular joint affected by anterior disc displacement during prolonged clenching.

Parafunctional habits, such as prolonged clenching and bruxism, have been associated with dysfunctional overloading in the temporomandibular joint (TMJ). In this study, stress distributions in the TMJ were analysed during prolonged clenching, using three-dimensional finite element (FE) models of the TMJ with and without disc displacement. The aim of this study was to investigate stress distribution of the cartilaginous tissues in the TMJ with and without disc displacement. Finite element models were developed on the basis of magnetic resonance images from two subjects with and without anterior disc displacement. Condylar movements recorded during a 5-min clenching were used as the loading condition for stress analysis. In the asymptomatic model, the highest von Mises stresses were located in the lateral area (4·91 MPa) of the disc surfaces, and after 5-min clenching, the higher stresses were still located at the lateral area (3·65 MPa). In all the cartilaginous tissues, 30-50% of stress reduction occurred during 5-min clenching. In contrast, the von Mises stress in the cartilaginous tissues of the symptomatic model with disc displacement was markedly lower, compared with the asymptomatic model. However, in the condylar cartilage, stress relaxation during clenching was not recognised. Furthermore, relatively high stresses were observed in the retrodiscal tissues throughout clenching. The present results indicate that disc position could be involved in the stress distribution of the TMJ components during prolonged clenching.


Females with sleep bruxism show lower theta and alpha electroencephalographic activity irrespective of transient morning masticatory muscle pain.

Aims: To investigate the hypothesis that the presence of transient morning masticatory muscle pain in young, healthy sleep bruxers (SBr) is associated with sex-related differences in sleep electroencephalographic (EEG) activity. Methods: Data on morning masticatory muscle pain and sleep variables were obtained from visual analog scales and a second night of polysomnographic recordings. Nineteen normal control (CTRL) subjects were age- and sex-matched to 62 tooth-grinding SBr. Differences in sleep macrostructure (stage distribution and duration, number of sleep-stage shifts), number of rhythmic masticatory muscle activity (RMMA) events÷ hour, and EEG activity were analyzed blind to subject status. The influence of pain and gender in SBr and CTRL subjects was assessed with the Fisher's exact test, Mann-Whitney U test, two-sample t test, and analysis of variance (ANOVA). Results: Low-intensity morning transient orofacial pain was reported by 71% of SBr, with no sex difference. RMMA event frequency was higher in SB than CTRL subjects (4.5÷hour vs 1.3÷hour; P < .001). SBr had fewer sleep-stage shifts, irrespective of sex or pain status. Female SBr had significantly lower theta and alpha EEG activity compared to female CTRL subjects (P = .03), irrespective of pain. Conclusion: Female SBr had lower theta and alpha EEG activity irrespective of transient morning pain.


Abstract Symposium: The patterns of close-open jaw movement during sleep in normal subjects


Comparison of ambulatory and polysomnographic recording of jaw muscle activity during sleep in normal subjects.

Clinicians and investigators need a simple and reliable recording device to diagnose or monitor sleep bruxism (SB). The aim of this study was to compare recordings made with an ambulatory electromyographic telemetry recorder (TEL-EMG) with those made with standard sleep laboratory polysomnography with synchronised audio-visual recording (PSG-AV). Eight volunteer subjects without current history of tooth grinding spent one night in a sleep laboratory. Simultaneous bilateral masseter EMG recordings were made with a TEL-EMG and standard PSG. All types of oromotor activity and rhythmic masseter muscle activity (RMMA), typical of SB, were independently scored by two individuals. Correlation and intra-class coefficient (ICC) were estimated for scores on each system. The TEL-EMG was highly sensitive to detect RMMA (0·988), but with low positive predictive value (0·231) because of a high rate of oromotor activity detection (e.g. swallowing and scratching). Almost 72% of false-positive oromotor activity scored with the TEL-EMG occurred during the transient wake period of sleep. A non-significant correlation between recording systems was found (r = 0·49). Because of the high frequency of wake periods during sleep, ICC was low (0·47), and the removal of the influence of wake periods improved the detection reliability of the TEL-EMG (ICC = 0·88). The TEL-EMG is sensitive to detect RMMA in normal subjects. However, it obtained a high rate of false-positive detections because of the presence of frequent oromotor activities and transient wake periods of sleep. New algorithms are needed to improve the validity of TEL-EMG recordings.


Gender specificity of the slow wave sleep lost in chronic widespread musculoskeletal pain.

The majority of patients suffering from musculoskeletal chronic widespread pain (CWP) are females, and they tend to report poor sleep. We tested the hypothesis that the poor sleep of female patients reporting CWP is gender specific for changes in (1) electroencephalograph (EEG) features and (2) heart rate variability (HRV).


A mandibular advancement appliance reduces pain and rhythmic masticatory muscle activity in patients with morning headache.

Short-term use of an MAA is associated with a significant reduction in morning headache and orofacial pain intensity. Part of this reduction may be linked to the concomitant reduction in RMMA.


Tooth wear in young subjects: a discriminator between sleep bruxers and controls?

Purpose: This study investigated whether the presence of tooth wear in young adults can help to discriminate patients with sleep bruxism (SB) from control subjects. Materials and Methods: The tooth wear clinical scores and frequency of sleep masseter electromyographic activity of 130 subjects (26.6 +/- 0.5 years) were compared in this case-control study. Tooth wear scores (collected during clinical examination) for the incisors, canines, and molars were pooled or analyzed separately for statistics. Sleep bruxers (SBrs) were divided into two subgroups according to moderate to high (M-H-SBr; n = 59) and low (L-SBr; n = 48) frequency of masseter muscle contractions. Control subjects (n = 23) had no history of tooth grinding. The sensitivity and specificity of tooth wear versus SB diagnosis, as well as positive and negative predictive values (PPV and NPV), were calculated. One-way analysis of variance and the Mann-Whitey U test were used to compare groups. Results: Both SBr subgroups showed significantly higher tooth wear scores than the control group for both pooled and separated scores (P < .001). No difference was observed between M-H-SBr and L-SBr frequency groups (P = .14). The pooled sum of tooth wear scores discriminates SBrs from controls (sensitivity = 94%, specificity = 87%). The tooth wear PPV for SB detection was modest (26% to 71%) but the NPV to exclude controls was high (94% to 99%). Conclusions: Although the presence of tooth wear discriminates SBrs with a current history of tooth grinding from nonbruxers in young adults, its diagnostic value is modest. Moreover, tooth wear does not help to discriminate the severity of SB. Caution is therefore mandatory for clinicians using tooth wear as an outcome for SB diagnosis. Int J Prosthodont 2009;22:342-350.

The International Journal of Prosthodontics


Studies on the Standardization of Parameters for Jaw Movements Analysis --- 6 Degree-of-Freedom Jaw Movements Analysis

顎運動解析パラメータの標準化に関する検討 --- 6自由度顎運動解析

The Journal of the Japan Prosthodontic Society


Studies on the Standardization of Parameters ofr Jaw Movements Analysis --- - Jaw Movement analysis at the Incisal Point-

顎運動解析パラメータの標準化に関する検討 --- ー切歯点における限界運動路解析ー

Purpose: To establish standardized evaluating methods for jaw movements analysis independently of the reference coordinate system. In this paper, we focused on the analysis of incisor point paths of border movements. Then we investigated parameters that are independent of the reference coordinate system and can be utilized among different systems.Methods: Recorded data of jaw border movements from 20 healthy male adults were employed as basic samples. First, the effects of changes of the reference coordinate systems on the analysis were investigated. Second, the line between incisor points at the intercuspal position and the maximal mandibular opening position was used as the reference line. Then the area index of incisor paths was calculated with the length of the perpendicular line dropped from the incisor point to the reference line and the displacement of the foot of the perpendicular.Results: Changes of the spatial relation between a reference plane of the coordinate system and border movements pathways had an effect on a measured area of projected pathways, about 2%-5% differences of projected area on the frontal plane with 10 degrees rotation around a horizontal axis. The area index of incisor paths showed close correlation with the actual area of a 3-dimensional plane bounded by the incisor path [sagittal border movement: ϱ = 0.53 (p = 0.016), left border opening pathway: ϱ = 0.97 (p < 0.001), right border opening pathway: ϱ = 0.98 (p < 0.001), Spearman rank correlation].Conclusion: The results suggest that new parameters could measure jaw border movements quantitatively independent of the reference coordinate system.

目的 : 本研究では, 解析時の基準座標系が異なっても利用可能な顎運動の評価基準を確立することを目的とし, 切歯点限界運動経路を対象として新たな解析パラメータについて検討を行った.方法 : 顎口腔系に特に異常を認めない成人男性20名 (平均年齢25.0 ± 8.2歳) の限界運動データを使用した. 解析では, まず基準座標系の違いの影響を検討するため, 基準面の傾きと投影面積の変化について検討した. 次に咬頭嵌合位と最大開口位を結んだ線を基準線とし, 各顎位からこの直線への垂線を計測して, 垂線の足の移動距離と垂線の長さから切歯点運動範囲指数を求めた. この指数の妥当性については, 三次元空間内での運動経路範囲を三次元曲面面積として計測した値との相関を求め検証した.結果 : 前頭面投影図面積は, 運動経路と前頭面の角度的関係が10度変化すると2%∼5%程度の影響を受けることが明らかとなった. 一方, 新たに求めた切歯点運動範囲指数は, 限界運動路で囲まれた面の三次元曲面面積と有意な相関を示した (矢状面内限界運動, ϱ = 0.53 (p = 0.016), 左側方限界開口路, ϱ = 0.97 (p < 0.001), 右側方限界開口路, ϱ = 0.98 (p < 0.001), Spearman rank correlation).結論 : 新たに考案したパラメータは, 基準座標系に依存することなく三次元的な限界運動経路を数値化することが可能であることが示された.


Bruxism physiology and pathology: an overview for clinicians.

Awake bruxism is defined as the awareness of jaw clenching. Its prevalence is reported to be 20% among the adult population. Awake bruxism is mainly associated with nervous tic and reactions to stress. The physiology and pathology of awake bruxism is unknown, although stress and anxiety are considered to be risk factors. During sleep, awareness of tooth grinding (as noted by sleep partner or family members) is reported by 8% of the population. Sleep bruxism is a behaviour that was recently classified as a 'sleep-related movement disorder'. There is limited evidence to support the role of occlusal factors in the aetiology of sleep bruxism. Recent publications suggest that sleep bruxism is secondary to sleep-related micro-arousals (defined by a rise in autonomic cardiac and respiratory activity that tends to be repeated 8-14 times per hour of sleep). The putative roles of hereditary (genetic) factors and of upper airway resistance in the genesis of rhythmic masticatory muscle activity and of sleep bruxism are under investigation. Moreover, rhythmic masticatory muscle activity in sleep bruxism peaks in the minutes before rapid eye movement sleep, which suggests that some mechanism related to sleep stage transitions exerts an influence on the motor neurons that facilitate the onset of sleep bruxism. Finally, it remains to be clarified when bruxism, as a behaviour found in an otherwise healthy population, becomes a disorder, i.e. associated with consequences (e.g. tooth damage, pain and social/marital conflict) requires intervention by a clinician.


A New Method for Designing Functionally Generated Occlusal Surface with Six-Degree-of-Freedom Articulator

6自由度咬合器を用いた機能的咬合面製作法の開発


Evaluation of Occlusal Relationship at Molars during Masticaion

咀嚼時の臼歯部咬合関係の評価


A Kinetic Analysis of Occlusal Contacts during Masticating Chewing-gum

ガム咀嚼における咬合接触状態の運動学的解析


咀嚼運動第4相における臼歯部の咬合関係

咀嚼運動第4相における臼歯部の咬合関係


Evaluation of Occlusal Contact Image on Articulating Paper Record

咬合紙記録における咬合接触像の評価


A proposal of quantitative evaluation method of occlusal facets with parameters of x axis value of direction cosine and inclination angle

方向余弦のx成分と傾斜角をパラメータとした咬合小面の定量的評価法の提案

The Journal of Japanese Society of Stomatognathic Function


The study on the occlusal facets of molars from the standpoint of harmony with jaw movements

顎運動の調和という観点からみた大臼歯咬合面形態の検討


A case of preparing complete denture using duplicate denture

複製義歯を用いて上顎総義歯の新製を行った症例


A Case of Dental Implant Treatment for Intermediate Missing of Bilateral Mandibular First Molars

両側下顎第一大臼歯中間欠損に対してインプラント治療を行った1 症例

Journal of Japanese Society of Oral Implantology

日本口腔インプラント学会誌


新しい方式を用いた非接触式3次元形状計測機の開発

新しい方式を用いた非接触式3次元形状計測機の開発


Sleep bruxism and masseter muscle activity during rem sleep of rem sleep behavior disorder patients: a case control study


睡眠時ブラキシズム中の顎運動様式

睡眠時ブラキシズム中の顎運動様式


睡眠時ブラキシズムの咬筋活動と顎運動

睡眠時ブラキシズムの咬筋活動と顎運動