During the fixed appliance therapy (metal brackets, NiTi archwires, stainless steel archwires), a marked reduction was observed in the total bacteria count from the subgingival pocket despite the clinical periodontal parameters remaining almost unchanged. However, the total count of some highly pathogenic bacteria rose again slightly after the end of treatment. We attribute the marked improvement in the periodontopathogenic bacteria spectrum under fixed appliance therapy with metal brackets, NiTi archwires and stainless steel archwires to metal corrosion entailing the release of primarily nickel ions, which have a toxic effect on bacteria and thus enable the regeneration of the physiological bacterial flora. In none of the patients was a deterioration of the periodontal status observed during and after fixed appliance therapy.
Changes in growth dimension and growth direction in three to four week old rabbits were studied cephalometrically after surgically repositioning the anterior part of the superficial masseter muscle dorsally to the angle of the mandible (n = 14). Only a sham operation was performed on 13 animals. Twelve months after the procedure the lower jaws were taken out and cleaned by boiling. X-rays were taken of the right and left part of the mandible. All x-rays were measured cephalometrically and the measurements evaluated statistical (alpha = 0.05) with the U-test (Mann/Whiteney). We found a statistically significant shorter mandible and an enlargement of the gonion angle, which indicate a vertical growth direction. The processus condylaris was unchanged. It can be assumed that the growth of the mandible can be altered permanently by muscle reposition, especially in cases with dysmoysis, a term in the literature first proposed by Eschler.
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