Frequency of occlusal interferences: a clinical study in teenagers and young adults

Contact relations between the teeth in the lower and upper jaws in the retruded position and on the nonfunctional side were investigated in two different age groups with mean ages of 15 and 22 years, respectively. The subjects had no complaints of mandibular dysfunction. The relations on the nonfunctional side were registered in four different positions of the mandible. Unilateral tooth contacts in the retruded position were found in 75% of the persons in both age groups. Lateral displacement of the mandible of 0.2 mm or more in sliding from RP to the IP occurred in 34% in the younger group and in 66% of the adults. Contacts on the balancing side at the four different lateral positions were found in 6% to 13% among the teenagers and in 9% to 25% among the adults. Balancing interferences, which appeared in 5% to 10% of the persons in both age groups at 3 mm lateral movement, increased 5% to 11% between each one of the other positions registered. These interferences reached a level of appearing in every three to four persons at maximal lateral movement of the mandible. No less than 88% and 89%, respectively, of the individuals in both age groups had at least one occlusal contact, usually defined as an interference, in one or more of the nine registered positions of the mandible. Because the subjects had well-functioning masticatory systems, this study does not support the opinion that the mere presence of occlusal interferences is of major importance in the etiology of mandibular dysfunction.