Effect of Asymptomatic Visible Third Molars on Periodontal Health of Adjacent Second Molars: A Cross-Sectional Study

Purpose Evidence that asymptomatic third molars (M3s) negatively affect their adjacent second molars (A-M2s) is limited. The present study evaluated the association between visible M3s (V-M3s) of various clinical status with the periodontal pathologic features of their A-M2s. Patients and Methods Subjects with at least 1 quadrant having intact first and second molars, either with V-M3s and symptom free or without adjacent V-M3s, were enrolled in the present cross-sectional investigation. Periodontal parameters, including plaque index (PLI), bleeding on probing (BOP), probing pocket depth (PPD), and at least 1 site with a PPD of 5 mm or more (PPD5+), obtained from M2s were analyzed according to the presence or absence of V-M3s or the status of the M3s. The χ2 test or t test was used to compare the mean PLI, PPD, BOP percentage, and PPD5+ percentage. The association of PPD5+ with V-M3 status was assessed using a multivariable logistic regression model (quadrant-based analysis), and variances were adjusted for clustered observations within subjects. Results In total, 572 subjects were enrolled in the study, and 423 had at least 1 V-M3. At the in-quadrant level, the presence of a V-M3 significantly increased M2 pathologic parameters, including PLI, PPD, BOP, and PPD5+. When analyzed using a multivariate logistic regression model, impacted M3s and normally erupted M3s significantly elevated the risk of PPD5+ on their A-M2s (odds ratio 3.20 and 1.67, respectively). Other factors associated with an increased odds of PPD5+ were mandibular region and older age. Finally, the patient-matched comparison showed that the percentage of BOP and PPD5+ on M2s increased when V-M3s were present. Conclusions Irrespective of their status, the presence of V-M3s is a risk factor for the development of periodontal pathologic features in their A-M2s. Although the prophylactic removal of asymptomatic V-M3s remains controversial, medical decisions should be made as early as possible, because, ideally, extraction should be performed before symptom onset. Evidence that asymptomatic third molars (M3s) negatively affect their adjacent second molars (A-M2s) is limited. The present study evaluated the association between visible M3s (V-M3s) of various clinical status with the periodontal pathologic features of their A-M2s. Subjects with at least 1 quadrant having intact first and second molars, either with V-M3s and symptom free or without adjacent V-M3s, were enrolled in the present cross-sectional investigation. Periodontal parameters, including plaque index (PLI), bleeding on probing (BOP), probing pocket depth (PPD), and at least 1 site with a PPD of 5 mm or more (PPD5+), obtained from M2s were analyzed according to the presence or absence of V-M3s or the status of the M3s. The χ2 test or t test was used to compare the mean PLI, PPD, BOP percentage, and PPD5+ percentage. The association of PPD5+ with V-M3 status was assessed using a multivariable logistic regression model (quadrant-based analysis), and variances were adjusted for clustered observations within subjects. In total, 572 subjects were enrolled in the study, and 423 had at least 1 V-M3. At the in-quadrant level, the presence of a V-M3 significantly increased M2 pathologic parameters, including PLI, PPD, BOP, and PPD5+. When analyzed using a multivariate logistic regression model, impacted M3s and normally erupted M3s significantly elevated the risk of PPD5+ on their A-M2s (odds ratio 3.20 and 1.67, respectively). Other factors associated with an increased odds of PPD5+ were mandibular region and older age. Finally, the patient-matched comparison showed that the percentage of BOP and PPD5+ on M2s increased when V-M3s were present. Irrespective of their status, the presence of V-M3s is a risk factor for the development of periodontal pathologic features in their A-M2s. Although the prophylactic removal of asymptomatic V-M3s remains controversial, medical decisions should be made as early as possible, because, ideally, extraction should be performed before symptom onset.