Intercuspal contacts of the natural dentition in centric occlusion.

The location of occlusal contacts in the intercuspal position was recorded in 29 young adults, 18 to 20 years of age. All participants had Class I essentially normal occlusion. Dental impressions and wax registration were made in all participants. Occlusal registrations were made of the posterior teeth only on a U-shaped prosthetic frame. Three types of indentation were recorded. Perforation of the wax represented supracontact; a translucent area represented contact; and slight thinning of the wax represented near contact. All three types of indentation were considered as contacts. The most striking finding was the high frequency of contacts on the mandibular first molar, which occurred in more than 20.9% of all contacts recorded. Most of the contacts were on cusps; only a few were in central fossae and marginal ridge areas. A surprising finding was the predominance of supracontacts on the second molars when compared to the remains of the dentition. No logical explanation for this finding can be offered. Morphologically good occlusion did not imply maximum contacts since an ideal occlusal contact was not found in any of the participants. Only serial studies will show whether occlusal relationships are stable throughout life or constantly changing.