Changes in Third Molar and Nonthird Molar Periodontal Pathology Over Time

The purpose of this study was to assess changes in periodontal probing depth (PD) over time for third molar and nonthird molar regions in young adults.The data were obtained from healthy subjects with 4 asymptomatic third molars, enrolled in an IRB-approved longitudinal trial. Demographic and oral health data were collected at baseline. Full-mouth PD, 6 sites per tooth, was conducted to determine periodontal status at baseline and at longest follow-up. The third molar region was defined as the PD for 6 sites around the third molars and the 2 sites on the distal of the second molars. The nonthird molar region was defined as the remainder of the PD sites in the mouth. The primary outcome measures for this study were the occurrence of a PD greater than or equal to 4 mm and the increase in PD of at least 2 mm in the third molar and nonthird molar regions. Changes from enrollment to longest follow-up were compared by the binomial or McNemar's test. Level of significance was .05.Data from 195 subjects were available, and the median follow-up was 5.9 years (interquartile range [IQ], 4.6 to 6.9 years). Median age at enrollment was 26.2 years (IQ, 22.0 to 34.0 years); 52% were female, 84% were Caucasian, and 10% were African American. The proportion of subjects with at least 1 involved site in nonthird molars increased significantly from baseline to follow-up, 36% to 49% (P.01), reflecting mostly changes in mandibular nonthird molars, 33% to 48% (P.01). Of the 122 subjects who presented at baseline with at least 1 PD greater than or equal to 4 mm in the third molar region, the proportion of subjects with at least 1 involved site in nonthird molars increased significantly from baseline to follow-up, 48% to 59% (P = .05), also reflecting mostly changes in mandibular nonthird molars, 44% to 59% (P = .05).In this unique longitudinal clinical study of early periodontal disease in young adults, periodontal pathology worsened over time for nonthird molars. This was more likely if PD greater than or equal to 4 mm was detected in the third molar region.