Abstract:

Objective:This study aimed atinvestigating effects of fixed appliances on the oral micro-ecological environment and establish- ing further the potential relationship between fixed appliances and the occurrence of caries and gingivitis during orthodontic treat- ment.Methods:50 orthodontic subjects were divided into two equal experimental groups according to the frequency and period of tooth-brushing. 10 non-treated volunteers served as the control group. Dental plaque samples were taken from the testing site at four different times, before the treatment, and 2 weeks, 4 weeks, and 8 weeks after the placement of the orthodontic brackets and bands. Congo red negative stained smearwas introduced to determine the composition of the bacteria from dental plaque.Results: After the insertion of brackets, the dental plaque from the distobuccal aspects of the second mandibular bicuspids showed signifi- cant shifts on the composition of bacteria along with time, the percentage of bacilli increased; contrarily, a decrease in cocci was noted. The frequency and period of tooth-brushing influenced the transformation of composition of bacteria distinctly. Whereas the dental plaque sample from the molar margin did not show significance changes in composition of bacteria after banding despite of the varied oral hygiene measures.Conclusion:The insertion of brackets in the second mandibular bicuspid caused the change of microecological environment by/shifting0the dental plaque to a more disease-inducing population and became the potential factor of the gingivitis and caries during orthodontic treatment, but reinforced oral hygiene measure would be helpful in reducing the risk of caries and gingivitis in bicuspid.

Key words: orthodontic appliance, plaque, caries, gingivitis