Relationship between the unilateral TMJ osteoarthritis/osteoarthrosis, mandibular asymmetry and the EMG activity of the masticatory muscles: a retrospective study.

The purpose of this retrospective study was to investigate the relationship between the unilateral temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA), mandibular asymmetry and electromyographic (EMG) activity of the masticatory muscles. Twenty-two Japanese women (aged 23.2 +/- 5.4 years) and 10 Japanese men (aged 22.4 +/- 2.8 years) exhibiting unilateral TMJ OA were included in this study. Two angular and seven linear measurements were obtained for the analysis of the skeletal hard tissues. The cephalometric measurement values (CV) were normalized using the CV ratio for the evaluation of the degree of mandibular asymmetry. The EMG was recorded during maximal voluntary clenching efforts for 10 s in the intercuspal position. The average values of integral EMG (iEMG) of three trials were normalized using the iEMG ratio for the evaluation of the functional balance of the masticatory muscles. The mandibular midline was shifted to the TMJ OA side with a median value of 9.85 mm. The CV ratio of the ramus height of the TMJ OA side was significantly smaller than that of the non-OA side. For the masseter muscle, the iEMG ratio of the TMJ OA side was significantly larger than that of the non-OA side (P < 0.05). These results suggest that unilateral TMJ OA is related to the dentofacial morphology, thus resulting in a mandibular midline shift to the affected side and it is associated with a masticatory muscle imbalance.

Relationship of TMJ osteoarthritis / osteoarthrosis to head posture and dentofacial morphology.

OBJECTIVE: The purpose of this study was to test the hypothesis that there is a relationship between the temporomandibular joint (TMJ) osteoarthritis/osteoarthrosis (OA), head posture and dentofacial morphology. DESIGN: Case-control study. SUBJECTS AND METHODS: The subjects consisted of 34 Japanese females with TMJ OA (aged 24.7 +/- 6.1 years) and a control group of 25 healthy Japanese females (aged 23.6 +/- 1.3 years). Six cranio-cervical angular measurements were constructed for head posture analysis. Nine angular and three linear measurements were constructed for the skeletal hard tissue analysis. Five angular and one linear measurements were constructed for the dental hard tissue analysis. Unpaired t-tests were used to compare the mean differences of head posture measurements and dentofacial cephalometric measurements between the TMJ OA and the control group. RESULTS: The TMJ OA group had significantly larger cranio-cervical angles (p < 0.05) and had more posteriorly rotated mandibles (p < 0.0001) than those in the control group. They also had a significantly shorter posterior facial height (p < 0.0001). The TMJ OA group had more retroclined lower incisors (p < 0.05). CONCLUSION: These results suggest that an association may exist between TMJ OA, head posture and dentofacial morphology.

A comparison and validation of amorphous sensor condylar movement analysis to MRI diagnosis of anterior disc displacement.

This study compared temporomandibular joint condylar movements in a sample of six patients with clinically normal joints, with those of nine patients with joints diagnosed by magnetic resonance imaging (MRI) to have anterior disc displacement with reduction (ADD). The aim of this study was to compare and validate the use of the amorphous sensor to MRI diagnosis in condylar movement analysis. The measuring device consisted of an amorphous sensor and a small magnet. Condylar and jaw movements were recorded simultaneously over the course of 10 open-close cycles. Maximum velocity of condylar movement during the opening phase in the ADD joints was significantly higher than the normal joints. The degree of jaw opening at the turning point of condylar movement in the ADD joints was significantly larger than the normal joints. The diagnostic sensitivity and specificity of the maximum velocity of condylar movement during the opening phase was 75.0 and 75.0%, respectively, while those of the degree of jaw opening at the turning point of condylar movement were 91.7 and 91.7%, respectively. These results suggest that the analysis of condylar movement, employing the amorphous sensor may be a reliable method for diagnosis of ADD.

Frequency spectrum of condylar movement in clinically normal subjects, using an amorphous sensor.

The purpose of this study was to determine the properties of the frequency spectrum produced by condylar movements in normal subjects, by the use of an amorphous sensor. The gender-matched sample consisted of white people (17 males and 17 females, aged 25.8 +/- 2.5 and 25.5 +/- 2.8 years, respectively) who had no subjective or objective symptoms related to temporomandibular joint sounds. Bilateral condylar and jaw movements were recorded simultaneously. The results showed that the mean +/- standard deviation (s.d.) for the mean frequency of condylar movement during the opening and closing phases was 45.0 +/- 5.2 and 47.0 +/- 3.5 Hz, respectively. The mean +/- s.d. for the peak frequency of condylar movement during the opening and closing phases was 46.6 +/- 8.0 and 49.7 +/- 4.5 Hz, respectively. Significant correlations existed between the left and right sides in the mean frequency as well as the peak frequency during the opening phase. However, there were no significant correlations between the left and right sides in the mean frequency or the peak frequency during the closing phase. These results suggest that the frequency spectrum of normal condylar movement can be obtained when using the amorphous sensor.

Condylar movement analysis in subjects with clinically normal temporomandibular joints, utilizing an amorphous sensor.

The purpose of this study was to determine the range of condylar movements in normal subjects, by the use of an amorphous sensor. The pair-matched sample consisted of 17 Caucasian males (aged 25.8 +/- 2.5 years) and 17 Caucasian females (aged 25.5 +/- 2.8 years) who had no subjective or objective symptoms related to temporomandibular joint (TMJ) sounds. Bilateral condylar and jaw movements were recorded simultaneously. The results showed that the typical condylar movement points plotted on the X-Y coordinates indicated a uniform or approximately straight line, that is X = Y. The mean +/- standard deviation (s.d.) for the maximum velocity of condylar movement during the opening and closing phases was 32.6 +/- 16.9 and 39.8 +/- 21.5 mm s-1, respectively. The mean +/- s.d. for the degree of jaw opening at the turning point of condylar movement was 36.9 +/- 21.7%. Significant correlations existed between any two measurements of maximum velocity of condylar movement. Moreover, significant correlations existed between the left and right sides in the degree of jaw opening at the turning point of condylar movement. These results suggest that a range of normal values of condylar movements can be developed when utilizing the amorphous sensor method.

Changes in tooth position in humans in relation to arterial blood pressure.

The three-dimensional physiological tooth movement synchronized with the heartbeat is called periodontal pulsation. This study utilized a computer-assisted amorphous sensor to evaluate the relation between tooth position and arterial blood pressure, and also between the amplitude of periodontal pulsation and arterial blood pressure. The measuring device consisted of a small magnet attached to the tooth and an amorphous sensor that was used to detect displacement of the tooth without actually contacting it. The sample consisted of the upper left central incisors of six healthy Japanese volunteers. The three measuring points for each tooth were on the labial surface. The cold-pressor test was used as an autonomic nerve stimulus that induces an increase in blood pressure and heart rate. Periodontal pulsation, electrocardiogram, blood pressure and heart rate were recorded simultaneously during a 1 min pre-test relaxation, a 2 min cold-pressor test and a 1 min recovery. The results showed significant correlations between tooth position and mean blood pressure in five of the six volunteers and between tooth position and pulse pressure in four. Moreover, it was confirmed that tooth position shifted in the labial direction in conjunction with an increase of the mean blood pressure induced by cold stimulation. Significant correlations were found between the amplitude of periodontal pulsation and pulse pressure in four of the volunteers. These findings suggest that in humans tooth position might be affected by the force of blood pressure transmitted through periodontal vessels and that the amplitude of periodontal pulsation tends to reflect changes of pulse pressure rather than changes in mean blood pressure.

An assessment of root cementum in cleidocranial dysplasia.

The purpose of this prospective study was to determine if there is a difference between the amount of cellular and acellular cementum on the roots of 2 teeth extracted from a subject with cleidocranial dysplasia (CCD) compared to 10 teeth extracted from 10 subjects unaffected by CCD. The cementum of 2 permanent teeth, which had been extracted from the CCD subject, was examined and histomorphometrically analyzed for comparison to the cementum of 10 anterior teeth that had been extracted from individuals who were unaffected by CCD. The percentage of the root covered by cellular or acellular cementum was quantified to determine if patients affected by CCD typically lack cellular cementum. In the roots of the 2 permanent teeth of the subject with CCD, a mean of 18.05 +/- 10.67% was covered by cellular cementum and 76.90 +/- 3.53% was covered by acellular cementum. In the 10 permanent teeth from subjects without CCD, a mean of 19.12 +/- 15.60% of the root was covered by cellular cementum and 80.34 +/- 15.71% was covered by acellular cementum. The findings indicate that there is no statistically significant difference between the amount of either cellular or acellular cementum covering the roots of the study subject with CCD and the roots of the 10 control teeth. The presumption that a lack of cellular cementum causes the increased number of unerupted teeth in patients with CCD is not supported by the findings of this study.

An aggressive dentigerous cyst in a seven-year-old child.

A review of literature indicates that very few of these cysts are found in children less than ten years of age, in spite of the fact that the cysts are associated with the eruption and/or formation of the secondary dentition. Although dentigerous cysts are rare in the first decade of life, a thorough review of a child's initial radiographs is of obvious importance as indicated by this case report. Of prime importance in this matter is the age at which the initial panoramic radiographic examination is performed on a child. According to the guidelines recommended by the American Academy of Pediatric Dentistry, the first panoramic radiographic examination should be performed following the eruption of the first permanent tooth. In this case, the appropriate radiographic survey was not conducted. A proper survey should include: Proper exposure of the film. Proper development of the film. Proper interpretation of the film. This child had a quadrant of dentistry performed three months prior to the discovery of the lesion. The previous dental provider noted that a panoramic radiograph had been exposed. It is unclear whether all of the aforementioned steps were followed or completed in order for the provider to obtain the information needed to render a diagnosis, and to properly refer this patient for a more in-depth examination of her mandibular swelling. The mere fact that this child's right mandibular first molar was fully erupted and the left one had not erupted at all, would be reason enough to take a panoramic radiograph to investigate the cause of the clinical absence of the contralateral first molar. This article has presented a case in which a proper panoramic radiographic examination performed at the time of eruption of the first permanent tooth may have led to an earlier diagnosis of the cyst, and thus might have prevented the loss of multiple permanent teeth.

Orthodontic movement through a repaired buccal alveolar fracture: a case report.

Orthodontic treatment in adults often involved the extraction of a lower central incisor. The extraction of these teeth can be problematic. Some factors that can influence successful treatment include: difficult access for actual tooth removal; the existing contour and bulk of the alveolar ridge; the buccal tooth position; and the inclination of the tooth in the alveolus. A patient who had a lower central incisor removed experienced a buccal alveolar fracture because of thin buccal plate. Upon healing there was a buccal defect that prevented the later tooth movement that would have closed the extraction site. The area was grafted with a demineralized freeze dried bone allograft to provide a matrix for osteoinduction. Gore-Tex was used as the physical barrier. After 6 months, the extraction side was closed by passing the lateral incisor through the graft site. The result was good tooth alignment and slight horizontal bone loss in the defect area.

The use of ceramic orthodontic brackets as rest seats for removable partial dentures.

Ceramic orthodontic brackets were developed for the purpose of esthetics and increased tooth-to-bracket strength. An alternative method of preparing a rest seat on the lingual surface of lower canine teeth without violating the enamel integrity is offered. Ceramic orthodontic brackets were bonded to the lingual surfaces of mandibular canines and shaped into rest seats using diamond burs. Because the rest seats are not cut into the tooth structure, sensitivity and potential caries complications are avoided. The bracket is adhered to the tooth surface with a dimethacrylate bonding material. The brackets are bonded with either a no-mix or a two-part adhesive system. The strength of this bond will easily support the forces of a partial denture framework. The advantage over metal acid-etched retained rests is that this method avoids a time-consuming laboratory step. The greatest advantage over the use of composite resins that are shaped into rest seats is the much higher bond strength. After ceramic brackets were bonded to the lingual surfaces of mandibular canines and shaped into rest seats, an impression was obtained for the fabrication of a conventional partial denture framework.