Effects of lower third molar extraction on attachment level and alveolar bone height of the adjacent second molar

Several conflicting findings have been published in previous literature regarding the effects of impacted third molar extraction on the periodontal health of the adjacent second molar; some authors have shown improvement of periodontal health distal to the adjacent second molar, whilst others have demonstrated loss of attachment and reduction of alveolar bone height. The purpose of this controlled clinical and radiographic study is to evaluate the long-term changes in periodontal health and alveolar bone height distal to the adjacent second molar following extraction of an impacted third molar. This split-mouth design study included 25 patients who underwent extraction of one mandibular impacted third molar (test), whereas the opposite tooth remained intact (control). Pre-operative and current-state panoramic radiographs were than scanned, and alveolar bone height was digitally measured on the distal aspect of the second molar on the test and control sides. Current-state clinical measurements were performed on both sides, and consisted of plaque index, gingival index, periodontal pocket depth, gingival margin position and clinical attachment level. Student's t-test for paired observations was used in order to examine the statistical significance of the differences in clinical parameters between the test and control sides and the differences in alveolar bone height pre- and post-operatively on both sides. Extraction of an impacted third molar resulted in a significant gain of alveolar bone height on the distal aspect of the adjacent second molar on the test side, whereas slight bone loss was noted on the control side. Even though the difference in plaque index between the test and control sides approached statistical significance following extraction, all clinical parameters seem to be unchanged. Further follow-up on clinical and radiological parameters is required for a more profound understanding of the long-term effects of third molar extraction on the periodontal health of the adjacent second molar.