P. aeruginosa were detected frequently. Regarding orthodontic treatment, Naranjo et al. (14) reported that bracket placement influences the plaque accumulation and colonization of peri odontopathic and superinfecting bacteria, resulting in more inflammation of gingival tissue. Based on the latter three reports, we examined opportunistic or superinfecting patho- gens, and we think it is necessary to reduce plaque accumulation during orthodontic treatment to prevent such type of periodontal disease.