Fractal analysis of the effects on mandibular bone of botulinum toxin therapy of the masseter muscle in patients with bruxism.

[OBJECTIVE] We examined changes in the mandibular angle, ramus, and condylar neck of patients with bruxism after botulinum toxin-A (BTX-A) injection into the masseter muscle as calculated with fractal analysis (FA) on panoramic radiographs (PRs).

[METHODS] We examined the PRs of 3 groups of 22 patients each (n = 66) obtained upon presentation and 6 months later. One group included healthy controls without bruxism, one group included patients with untreated bruxism, and one group included patients with bruxism who had undergone BTX-A injection into the masseter muscle. We performed FA of the bilateral angle, ramus, and condylar neck of the PRs to calculate fractal dimension (FD).

[RESULTS] The FD values of the angle on the second PRs of the untreated bruxism group were significantly higher than those of the other groups (P = .026), specifically when compared to the BTX-A injection group (P = .017). The FD values in the angle and ramus of the bruxism group were significantly higher on the second PRs (P ≤..005)) Conversely, the FD values in the angle of the BTX-A injection group were significantly lower on the second PR (P = .039).

[CONCLUSIONS] Masseter muscle hyperactivity due to bruxism increases bone density in masseter muscle attachment regions. BTX-A injection restricts muscle activity, thereby chnging bone structure and decreasing FD.