Clinical and microbiological studies of children and adolescents receiving orthodontic treatment.

PURPOSE: This case-controlled study examined clinical and microbiological parameters in Brazilian children and adolescents receiving orthodontic treatment using fixed orthodontic appliances or removable orthodontic appliances. METHODS: The plaque index, gingival index, number of decayed, missing and filled teeth, and probing pocket depth was measured on each fully erupted tooth in 30 patients treated with fixed orthodontic appliances and an equal number of age and sex-matched control subjects. The same parameters were also measured in 18 patients treated with removable orthodontic appliances and an equal number of age and sex-matched control subjects. In the patients treated with fixed orthodontic appliances, subgingival plaque samples were collected from four teeth with orthodontic brackets and from four teeth with orthodontic bands. In the patients with removable appliances, subgingival plaque samples were collected from clasped maxillary permanent first molar teeth and from four unclasped permanent teeth. Samples of unstimulated whole saliva and samples from the dorsal surface of the tongue were also obtained from each subject. Each sample was analyzed for the presence of 19 target bacteria by dot blot. A subset of samples was examined by direct amplification of bacterial nucleic acids. RESULTS: Compared to their respective age and sex-matched controls, whole mouth means for plaque index and gingival index were significantly elevated in both the fixed and removable orthodontic groups. There was no difference in the DMFT. Subjects with fixed orthodontic appliances had a higher prevalence of each of the target species except for L. fermentum, Neisseriaceae and S. mutans. The prevalence of A. naeslundii and Streptococcus sp. was significantly higher on teeth with orthodontic brackets alone compared to teeth with both orthodontic bands and brackets. Subjects with removable orthodontic appliances had a higher prevalence of A. actinomycetemcomitans, C. rectus, E. corrodens, L. fermentum, Neisseriaceae, and spirochetes. The prevalence of Neisseriaceae was significantly higher on unclasped teeth compared to clasped teeth. There was no difference between sample sites for the target bacteria except for A. actinomycetemcomitans that was detected less frequently in saliva. Orthodontic patients demonstrated higher proportions of gram negative species by direct amplification of nucleic acids including species frequently associated with periodontal disease as well as rarely cultivable or non-cultivable species such as Abiotrophia defectiva, Gemella haemolysans, Granulicatella adiacens, Lautropia sp., Terrahaemophilus aromaticivorans, and TM7 bacterium.

Identification of Fur-regulated genes in Actinobacillus actinomycetemcomitans.

Actinobacillus actinomycetemcomitans is an oral pathogen that causes aggressive periodontitis as well as sometimes life-threatening, extra-oral infections. Iron regulation is thought to be important in the pathogenesis of A. actinomycetemcomitans infections and, consistent with this hypothesis, the fur gene has recently been identified and characterized in A. actinomycetemcomitans. In this study, 14 putatively Fur-regulated genes were identified by Fur titration assay (Furta) in A. actinomycetemcomitans, including afuA, dgt, eno, hemA, tbpA, recO and yfe - some of which are known to be Fur regulated in other species. A fur mutant A. actinomycetemcomitans strain was created by selecting for manganese resistance in order to study the Fur regulon. Comparisons between the fur gene sequences revealed that nucleotide 66 changed from C in the wild-type to T in the mutant strain, changing leucine to isoleucine. The fur mutant strain expressed a nonfunctional Fur protein as determined by Escherichia coli-based ferric uptake assays and Western blotting. It was also more sensitive to acid stress and expressed higher levels of minC than the wild-type strain. minC, which inhibits cell division in other bacterial species and whose regulation by iron has not been previously described, was found to be Fur regulated in A. actinomycetemcomitans by Furta, by gel shift assays, and by RT-qPCR assays for gene expression.