CLINICAL-SIGNIFICANCE OF ACTINOBACILLUS-ACTINOMYCETEMCOMITANS IN YOUNG INDIVIDUALS DURING ORTHODONTIC TREATMENT - A 3-YEAR LONGITUDINAL-STUDY

The aim of the present study was: (1) to assess longitudinally the occ urrence of Actinobacillus actinomycetemcomitans (Aa) in young subjects wearing fixed orthodontic appliances compared to matched appliance-fr ee controls; (2) to determine whether the presence of the micro-organi sm at baseline could influence the periodontal status assessed 3 years later. 70 subjects, 27 male and 43 female, aged between 12 and 20 yea rs participated in the study: 35 subjects under orthodontic treatment with fixed appliances for at least 6 months, and 35 appliance-free ind ividuals matched for age and gender. All subjects were free of clinica lly demonstrable loss of attachment. They all received oral hygiene in structions 2x during the 2 months preceding the first clinical and mic robiological examination. No subgingival instrumentation was performed between baseline and the 3-year examination. Clinical parameters incl uded gingival bleeding index (GBI), pocket probing depth (PPD) and mea surements of attachment level (AL). Statistically significant differen ces were reported regarding frequency of detection of Aa between both groups at each examination. The %s of orthodontic subjects infected wi th Aa at the baseline and at the 3-year examination were 86% and 80%, respectively, while the corresponding figures for control subjects wer e 16.6% and 26.6%. The frequency distribution of %s of Aa in the total anaerobic subgingival flora among control subjects remained fairly st able, whereas the proportion of orthodontic subjects yielding Aa at a concentration greater than or equal to 1.0% dropped significantly from 32% at baseline to 19% at the 3-year visit. Calculations of the relat ive risk for increasing GBI and PPD in both groups when Aa was present at baseline, revealed that the orthodontic subjects positive for Aa h ad a negligible relative risk of experiencing worse periodontal condit ions compared to orthodontic patients where Aa was not detected at bas eline. In contrast, control subjects initially infected with Aa presen ted with a risk for increased GBI 6.6xhigher than that for subjects wi thout Aa. In conclusion, the present study confirmed previous cross-se ctional findings reporting that young individuals with an integer peri odontium wearing fixed orthodontic appliances harbor Aa with a statist ically significant greater frequency than appliance-free matched contr ols. However, although orthodontic patients exhibited more inflammatio n, their deteriorated clinical conditions could not be accounted for b y the sole presence of Aa in their sulci. In contrast, appliance-free young subjects initially infected with Aa had a higher risk of experie ncing more gingival inflammation than subjects without the bacterium d uring a 3-year observation period.