OBJECTIVEThe relationship between occlusion and temporomandibular disorders (TMD) remains disputed. The related epidemiological studies have been carried out focused on the occlusal characteristics in motion, for example in protrusion, retrusion or laterally extension and on some of malocclusion features. Very few studies were carried out on the intercuspal occlusion which is the most important occlusal relationship. Angle's classification of occlusion and the relationship of over-jet and over-bite are two prominent features now generally used in clinical practice for occlusal evaluation. In present study two kinds of features of occlusion were compared among TMD patients, malocclusion patients and university student volunteers, who of the laters represented nature population.

METHODS100 continued cases visiting our TMD Clinic during the year of 2 000 with complain of TMD problem, 100 malocclusion patients in continued orthodontic department records, and 268 university student volunteers were included. All subjects were with complete dentitions, except of age-related third or second molar tooth eruption difference. Study cast were obtained for all 468 subjects involved and following characters were studied. 1. Angle's classification; 2. Over-jet and over-bite relationship. Anteriorly it included cross-bite, cusp-to cusp bite, deep over-bite (without deep over-jet), deep over-jet (with or without deep-bite), open bite, and others. Posteriorly it included cross-bite, reverse cross-bite and others. 3. Abnormal occlusal index: For the purpose of quantitatively comparing the abnormal occlusal relationship of over-bite and over-jet, the occlusal index was introduced. The anterior continued abnormal was scored as 3 while posterior continued oclcusal abnormal scored as 5. The sum of the scores in the same subject was taken as his abnormal occlusion index.

RESULTS1. Ratio of Angle's I patients in malocclusion group was significantly lower than those in TMD group and US group (P < 0.05), while the later two groups had no difference (P > 0.05). 2. The ratios of anterior cross-bite and deep over-jet were higher in malocclusion group than those in other two groups. No significant difference for the other kinds of abnormal over-jet and over-bite relationship were found among the three groups. 3. The abnormal occlusion index of malocclusion group was higher than that of US group, but not than that of TMD group which had no difference with US group either.

CONCLUSIONS1. Aesthetic related anterior abnormal occlusion such as anterior cross-bite and deep-over-jet attract more attention of popular. But they had no relationship with TMD. 2. TMD patients had not significant occlusal features on Angle's classification and over-jet and over-bite relationship compared to malocclusion and nature population subjects.

Dental Occlusion ; Humans ; Malocclusion ; epidemiology ; Students ; Temporomandibular Joint Disorders ; Universities