Purpose: Our goals were to determine the prevalence of caries experience, carious lesions, or restorations on the occlusal surface, in asymptomatic third molars erupted to the occlusal plane, and to examine the association between caries experience in other molars and third molars within the same mouth and quadrant.
Patients and methods: Clinical data assessing oral health were collected from healthy patients (ASA I, II). The presence or absence of caries experience on the occlusal surface of third molars and on any surface of the first and second molars was recorded during clinical and radiographic examinations. The occurrence of caries experience for younger and older subjects was compared using the general association Cochran-Mantel-Haenszel statistic and the association of occurrence in the maxilla and mandible by the McNemar test. The association between caries experience in a third molar and caries experience in first and second molars also was assessed.
Results: Overall, 28% of the 303 patients with at least 1 third molar at the occlusal plane were affected by third molar caries. Patients 25 years or older had more caries experience in a third molar than those younger than 25 years, 39% versus 11% (P <.0001). Mandibular third molars were affected more often than maxillary third molars, 24% versus 18% (P <.0001). Nearly all patients, 76 of 80 (95%), with third molar caries experience also had caries experience in first/second molars, but only 80 of 223 (36%) of patients with first/second molar caries experience had a history of third molar caries.
Conclusions: The prevalence of caries in third molars erupted to the occlusal plane in these young patients was high, but not unique to third molars, particularly in those 25 years of age and older. Although these results provide a baseline description of the association between caries experience in first/second molars and associated third molars, data are needed from longitudinal studies to determine the value of first/second molar caries experience in predicting the risk of caries in third molars.