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Malocclusion is considered one of the etiological factors of temporomandibular joint disorder (TMD). The purpose of this study was to investigate the prevalence of TMD and the relationship between TMD and the type of occlusion. The sample consisted of 7337 Japanese children, 6–18 years old, 3219 boys and 4118 girls. TMD symptoms were recorded as well as the type of occlusion in children with TMD.

The prevalence of TMD overall was 12.2%. The prevalence increased with age and was slightly higher in girls (13%) than in boys 11.1%. This difference was not statistically significant. Joint sound as the only symptom was more common in younger subjects. TMD symptoms seemed more complicated with age when pain and abnormal jaw movement combined with sound. Joint sound was the most common symptom (89.3%), followed by the combination of sound and pain (2.2%). The incidence of other symptoms was under 1%. In subjects with TMD, 24.9% exhibited crowding, 20.1% had excessive overjet, 6.8% deep bite, 6.3% edge-to-edge bite, 5.6% anterior crossbite, 5.4% open bite, and 3.8% posterior crossbite. Morphologically normal occlusion was observed in 27.1%. In this study, many subjects with TMD had malocclusions. Early treatment may be important in the prevention of severe TMD. Although those with morphologicallly normal occlusions were included, a more detailed study concerning other causes of TMD is needed also.

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Changes in human gingival blood flow were measured using a Laser doppler flowmeter. The change of blood flow was correlated to the degree of force applied and there were variations in measurement of decreased blood flow among the subjects. The variation was attributed to the degree of tooth displacement and the size of the interdental space. This study examined the effect of tooth displacement on the gingival blood flow, as well as age and sex differences.

Blood flow in gingival tissue was measured using a laser doppler flowmeter, and displacement of the maxillary incisors was measured using an eddy current sensor. The correlation coefficient of the decreased blood flow to the tooth displacement was 0.809, and it was higher than that to the degree of applied force (r = −0.625). The regression coefficient of decreased blood flow to the displacement of teeth was significantly correlated to the interdental space. The regression coefficient of decreased blood flow to the percentage of tooth displacement was independent of the interdental space. However, the regression coefficient of decreased blood flow to the percentage of tooth displacement was significantly higher in young subjects than in adults.

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The effect of artificial saliva and topical fluoride treatments on the force relaxation and change in force delivery by three brands of elastomeric chains over a 4 week period was studied. The effect of storage in air and in the different test media on the distraction to achieve forces of 150g and 300g was determined for the chains. The effect of the test media on load relaxation of the chains was also examined.

Elastomeric chains exhibit good elastic behavior when distracted to an initial force of less than 300g. When forces exceeded 300g, permanent deformation occurred and the force delivery was less predictable. Exposure to artificial saliva and topical fluoride affected the elastic properties of the elastomeric chains and increased the distraction required to deliver both the 150g and 300g force. The increase in distraction for a force of 150g, however, was relatively small and probably insignificant in the clinical setting. The distraction required to produce 300g was significantly larger and appeared to be clinically significant. Pre-stretching the elastomeric chains by 100% of their initial length was not found to be advantageous in terms of the load relaxation behavior. There was less load relaxation found in chains that were immersed in distilled water and Acidulated Phosphate Fluoride than in chains exposed only to air.

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The bonding of orthodontic brackets to enamel surface using bis-GMA composite resin is usually accomplished by first cleaning the tooth surface then etching with phosphoric acid. This study compared the tensile bond strength of composite resin applied to a tooth surface which had been cleansed with an air-powder polisher to that of the same resin applied to a surface cleansed using a rubber cup and pumice. A wire loop apparatus was attached to bonded orthodontic brackets and pulled in tension in order to test the adherence of the bracket to the tooth. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to evaluate the tooth surface to determine whether sodium bicarbonate material remained after the cleaning operation. All data was analyzed by the one way analysis of variants, the Student-Newman-Keuls test and Duncan's multiple comparison test.

No statistical differences were found between the tensile strength of the bonds on the teeth cleansed with the air-powder polisher and those cleansed with a rubber cup and pumice. However, a double exposure of the tooth to phosphoric acid may lower the tensile bond strength by a significant amount.

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A sample of 97 untreated cleft lip and palate adult patients, with and without Simonart's band, was analyzed. The dimensions and form of the maxillary dental arches were analyzed. Comparison of this sample with a “normal” group indicated maxillary dental arch size and shape are distorted by the presence of a cleft which is characterized by a constriction that becomes more severe in the medial and anterior regions. The presence of Simonart's band affects the cleft arch form, redirecting the anterior extremity of the major segment towards the minor segment.

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Orthodontic study models, intraoral photographs, radiographs and diagnostic set-up casts of four completed adult cases are presented to show the possibilities of atypical treatment planning to correct specific and unusual malocclusions. The cases presented required asymmetric dental extractions in order to achieve the desired treatment results. Three diagnostic procedures were used to assist in making the final treatment decisions; a Bolton tooth size analysis, a space available/space needed assessment, and a pretreatment diagnostic set-up. The completed treatment results closely approximate the original diagnostic predictions, and completely satisfied each patient's chief concern. Most orthodontic practices now treat increasing numbers of non-growing (adult) patients. Traditional extraction considerations must be modified to satisfy the treatment needs of this demanding patient population.

This paper was presented at the March 1991 Annual Meeting of the Eastern Component of the Edward H. Angle Society.

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