Purpose: The purpose of this study is to extract contributing factors related to temporomandibular disorders (TMD) in the working population through a questionnaire survey.
Methods: We conducted a questionnaire survey for TMD screening and to ascertain contributing factors on 2,723 working people in company A, and collected 2,203 eligible answers.
Results: Out of 2,203 people, 362 were considered to have TMD (16.4%). This ratio was higher than the prevalence in the general population in Japan. Both the total score of psychosocial factors and habitual behavior were significantly higher in patients in the TMD group than in the non-TMD group. A multivariate logistic regression analysis revealed the aggravation of anxiety, increase of fatigue, increase of tooth contacting habit and symptoms upon waking in the morning in males, and an increase of fatigue and symptoms upon waking in the morning in female as significant factors.

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The guideline committee for the primary care of temporomandibular disorders (TMD) in the Japanese Society for Temporomandibular Joint carried out a preliminary questionnaire investigation of patients with TMD who visited one of three general dental practitioners for treatment. The purpose of the present investigation was to collect the "patient's questions (PQ)" from these patients. The questionnaire included questions on age, gender, commuting time to her/his dental office, symptoms and treatment of those patients who sought treatment for their symptoms.
As results, we collected 177 answers from 62 males and 115 females. Regarding the symptoms, joint noise was the most frequently listed, followed by limited mouth opening, myalgia, biting pain and arthralgia. As for treatment, mouth opening exercise was the most frequently listed, followed by massage, mouthpiece and jaw rest.
We confirmed that the treatment with a mouthpiece was well known to many patients. It was also shown that the expectation for treatment of joint noise was great. Further consideration and discussion on the methods and samples will be necessary in future investigations.

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Purpose: To investigate the false positive (FP) and false negative (FN) groups who were screened by one item screening (binary scale) for temporomandibular disorders (TMD).
Methods and subjects: We analyzed 1,225 dental patients (666 males and 559 females). We decided the FP group who was diagnosed as having TMD by one-item screening but was not diagnosed as having TMD by the clinical diagnosis, and the FN group who was not diagnosed as having TMD by the screening but was diagnosed by the clinical diagnosis. We investigated the differences of these definite diagnosis constitutions between the FP and true negative (TN) group. According to the four-item questionnaire for TMD (disturbance of mouth opening, jaw opening and/or closing pain, deviation opening, hard food chewing pain) on a five-point numeric rating scale, we compared the scores of four items between the FP and TN group, FN and true positive (TP) group.
Results: Inflammation and dental caries in the FP group showed a ratio as high as the TN group. The FP group had significantly high total scores for four items in comparison with the TN group. The FN group had significantly low total scores of jaw opening and/ or closing pain and food chewing pain in comparison with the TP group.
Conclusion: Inflammation and dental caries in the FP group showed a ratio as high as the TN group. The FN group had weaker pain than the TP group.

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It has been suggested that there is a relationship between temporomandibular disorders (TMD) such as temporomandibular joint osteoarthritis (TMJ-OA) and craniofacial morphology. However, no definite conclusion has been reached due to the variety of TMJ pathology and natural course of TMD. The purpose of this study was to investigate the association between TMJ-OA and craniofacial morphology. Subjects were selected from orthodontic patients with signs and symptoms of TMD who underwent MRI examination before treatment from 1998 to 2008. The subjects were divided into three groups: patients with unilateral TMJ-OA (UOA group), patients with bilateral TMJ-OA (BOA group) and patients without TMJ-OA and disc displacement (N group). Craniofacial morphology was analyzed on postero-anterior and lateral cephalograms. Bonferroni correction was used for statistical comparisons among the three groups.
As a result, the following measurement items showed significant differences between the BOA group and the other two groups (UOA group and N group), (∠ANB (p< 0.01), ∠SNB (p< 0.01), SN/MP (p< 0.01), PP/MP (p< 0.05) and Ar-Go (p< 0.01)). In the UOA group, all the patients exhibited mandibular lateral shift of the Me point to the symptomatic side. Moreover, the amount of lateral shift was significantly greater in the UOA group than in the other two groups (BOA and N groups).
These findings showed that bilateral TMJ-OA is related to steep mandibular plane, short ramus height, retro-positioned mandible and the resultant skeletal II maxillo-mandibular relation. Unilateral TMJ-OA may be related to lateral shift of the mandible. It is thus suggested that there might be an association between the presence of TMJ-OA and craniofacial morphology in orthodontic patients.

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Holmium: YAG (Ho: YAG) lasers are used during arthroscopic surgery of the temporomandibular joints. The aim of this study was to investigate the safety range for laser irradiation output in the temporomandibular joints of rabbits. The tip of the laser fiber was brought into contact with the disk and condyle; laser irradiation was conducted at 1 W, 7 W, and 10 W in each exposure time of 1, 3, and 5 seconds. Tissues were then stained and examined by optical microscopy to measure the maximum depth and width of tissue damage for each output. The results showed that ablation of the disk and condyle was observed at 1 W with 1 second exposure. However, the disk perforated at 7 W with 3 seconds of continuous exposure. The condyle was damaged up to a depth of 0.79 mm at 7 W with one second exposure. Considering the normal anatomy of the human condylar bone and disk thickness, the power of a Ho: YAG laser irradiation should be limited within a single exposure of 7 W for one second when clinically applying it in human temporomandibular joint surgery.

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