Bacterial colonization associated with fixed orthodontic appliances. A scanning electron microscopy study

This investigation was undertaken to assess bacterial plaque accumulation a djacent to orthodontic brackets. Experiments were carried out on 11 subject s who were scheduled for orthodontic treatment including extraction of two or four premolars. Metal brackets were bonded to the premolars to be extrac ted using macro-filled bonding composite. A conventional elastomeric ring w as placed around one bracket and a steel ligature wire around the bracket o n the contralateral tooth. The subjects were told to continue their normal oral hygiene regimen. Teeth were extracted at 1, 2, or 3 weeks after bracke t bonding. Scanning electron microscopic (SEM) examination of brackets, excess composi te, and buccal enamel revealed that mature plaque was present on excess com posite at 2 and 3 weeks after bonding, whereas plaque on the gingival ename l surface was still at an early stage of development. The results demonstra te that excess composite around the bracket base is the critical site for p laque accumulation due to its rough surface and the presence of a distinct gap at the composite-enamel interface. The method of ligation does not appe ar to influence the bacterial morphotypes on both composite and enamel surf aces.