A longitudinal study of occlusal interferences and signs of craniomandibular disorder at the ages of 12 and 15 years.

Occlusal interferences and signs of craniomandibular disorder (CMD) were studied longitudinally in 167 Finnish adolescents at the ages of 12 and 15 years in order to evaluate their importance for orthodontic diagnosis. Of the adolescents sampled 16.8 per cent had received orthodontic treatment. The results showed that occlusal interferences and signs of CMD are quite common. Of the 12-year-olds 25.7 per cent and 30.5 per cent of the 15-year-olds showed palpatory tenderness of the muscles of mastication. Clicking sounds were recorded for 6 per cent of the 15-year-olds. Opening capacity increased with age. Only tow of the adolescents at the age of 12 and none at the age of 15 fulfilled the criteria of functionally optimal occlusion. The number of occlusal interferences increased between 12 and 15 years of age. Both occlusal interferences and clinical signs of CMD were inconsistent in nature. Mediotrusion contracts and protrusion interferences were found to be the most stable occlusal interferences at adolescence. As to pain on mouth opening, the symptom group at the age of 15 consisted of entirely new individuals. No single sign or CMD symptom, nor combination of them, was consistent enough for inclusion in orthodontic screening indices. However, even though the symptomatology changed, only a few of those considered to be symptomatic at the age of 12 were asymptomatic at the age of 15. In accordance with the present state of knowledge, it would thus seem appropriate to add a general statement about the presence or absence of CMD signs and/or symptoms to orthodontic screening indices.(ABSTRACT TRUNCATED AT 250 WORDS)