Symptom free vs pathology free

Young adults with “symptom-free” third molars would like to know whether their third molars are “pathology free” and, if so, the likelihood of their third molars remaining free of pathology if the third molars are retained for a lifetime. Data on the prevalence of pathology with retained third molars, particularly periodontal inflammatory disease and caries experience, have been limited because third molar data are often not collected from subjects enrolled in clinical or population studies, or third molar data are excluded in the analyses. A recent report by Eke et al suggested that the limited periodontal examination for the prevalence of periodontal pathology in the United States in the National Health and Nutrition Estimates Survey, compared with full-mouth periodontal probing on all teeth present, underestimated the prevalence of periodontal disease. In both analyses by the National Health and Nutrition Estimates Survey and Eke et al, the periodontal status of the third molars was excluded. An additional comment by Eke et al is instructive; they stated that exclusion of third molars possibly contributed to the underestimation of the prevalence of periodontitis.

Retained third molars with no symptoms can be associated with cysts or tumors, increased susceptibility to jaw fractures, and malpositions of posterior teeth. Most clinicians would agree that the prevalence of these conditions is limited, probably less than 5%. In addition, some patients do have symptomatic third molars, most often pericoronitis or symptomatic periodontal inflammatory disease. This chronic condition with recurring acute episodes has a prevalence not greater than 10%. The treatment for these conditions almost always involves third molar removal.

Prevalence of third molar pathology

A series of recent reports based on an exploratory, longitudinal study conducted at 2 academic centers, the University of North Carolina and the University of Kentucky, has begun to better define the prevalence of third molar pathology in the remaining 85% of the population—those with no third molar symptoms yet with possible detectable caries experience or periodontal pathology. These current data confirm that “symptom-free” third molars do not equate to “pathology-free” third molars today, or for the person’s lifetime.

Data at enrollment from 409 healthy young adults, who averaged 25 years of age, with 4 retained asymptomatic third molars, suggested that periodontal pathology, defined as at least 1 probing site with at least 1 periodontal probing depth (PD) greater than 4 mm (PD4+), was prevalent on the third molars and the distal aspect of the adjacent second molars; 65% of the subjects were affected. The third molars at the occlusal plane or in the mandible were more likely to have a PD4+ than those below the occlusal plane or in the maxilla. A few subjects, 15%, had periodontal PD4+ sites anterior to the molars. Conversely, caries experience on third molars was less prevalent than on first or second molars, and only 1% of the subjects had caries experience on a third molar without first or second molar involvement. Caries experience overall was less than periodontal pathology. However, only 16% of subjects with 4 asymptomatic third molars at the occlusal plane, a useful functional position, were free of both periodontal pathology and caries.

More than a third of the 106 subjects with asymptomatic third molars that were free of periodontal pathology at enrollment developed a PD4+ in at least 1 third molar region within the next 4 years. The periodontal pathology was significantly more likely to be in the mandibular third molar region. Affected mandibular third molars tended to be vertical or distal and at the occlusal plane.

For the 194 subjects in the longitudinal study, who were followed for an average of 6 years, if 1 PD4+ was detected in a third molar region at enrollment, odds were 12-fold that at least 4 PD4+ would be found in a third molar at follow-up ( P <0.01). If the subjects had 1 PD4+ in a third molar region at enrollment, odds were 5-fold greater that at least 1 PD4+ would be detected on teeth more anterior in the mouth at follow-up in subjects with no anterior teeth involved previously ( P <0.01).

Prevalence of third molar pathology

A series of recent reports based on an exploratory, longitudinal study conducted at 2 academic centers, the University of North Carolina and the University of Kentucky, has begun to better define the prevalence of third molar pathology in the remaining 85% of the population—those with no third molar symptoms yet with possible detectable caries experience or periodontal pathology. These current data confirm that “symptom-free” third molars do not equate to “pathology-free” third molars today, or for the person’s lifetime.

Data at enrollment from 409 healthy young adults, who averaged 25 years of age, with 4 retained asymptomatic third molars, suggested that periodontal pathology, defined as at least 1 probing site with at least 1 periodontal probing depth (PD) greater than 4 mm (PD4+), was prevalent on the third molars and the distal aspect of the adjacent second molars; 65% of the subjects were affected. The third molars at the occlusal plane or in the mandible were more likely to have a PD4+ than those below the occlusal plane or in the maxilla. A few subjects, 15%, had periodontal PD4+ sites anterior to the molars. Conversely, caries experience on third molars was less prevalent than on first or second molars, and only 1% of the subjects had caries experience on a third molar without first or second molar involvement. Caries experience overall was less than periodontal pathology. However, only 16% of subjects with 4 asymptomatic third molars at the occlusal plane, a useful functional position, were free of both periodontal pathology and caries.

More than a third of the 106 subjects with asymptomatic third molars that were free of periodontal pathology at enrollment developed a PD4+ in at least 1 third molar region within the next 4 years. The periodontal pathology was significantly more likely to be in the mandibular third molar region. Affected mandibular third molars tended to be vertical or distal and at the occlusal plane.

For the 194 subjects in the longitudinal study, who were followed for an average of 6 years, if 1 PD4+ was detected in a third molar region at enrollment, odds were 12-fold that at least 4 PD4+ would be found in a third molar at follow-up ( P <0.01). If the subjects had 1 PD4+ in a third molar region at enrollment, odds were 5-fold greater that at least 1 PD4+ would be detected on teeth more anterior in the mouth at follow-up in subjects with no anterior teeth involved previously ( P <0.01).

Data on visible third molars

A recent review of available third molar data from clinical studies and studies conducted for other purposes suggested that having a visible third molar might be a risk indicator by itself for an anaerobic environment conducive to periodontal inflammatory disease. Deeper mean periodontal PDs in the first and second molar regions were detected more often in patients retaining third molars, and third molar mean PDs were greater than mean PDs on other teeth more anterior in the mouth.

Are these data biologically plausible? Once teeth are exposed to the oral cavity and can be probed, oral flora colonize on the tooth surfaces in a nonsheddable biofilm. Third molars are the most posterior teeth in each jaw; on average, they erupt at age 19, after jaw growth is complete. Mandibular third molars are situated anatomically in alveolar bone in the jaw at the junction of the horizontal body and the vertical ramus. The combined impact of erupting at a later age than other teeth and the anatomic location in the jaw might be why a greater prevalence of PD4+ is found around mandibular third molars.