Abstract:

Objective  To establish a multiplex PCR for the detection of four species of bacteria ( Aa, Bf, Fn and Pg) in oral specimens from orthodontic patients, and to analyze the correlation between the presence of bacteria and gingival index.  Methods  Periodomal pocket specimens from fifty-five patients who had worn fixed orthodontic appliances for at least 2 months and thirty-four healthy individuals without orthodontic appliances were collected. DNAs of the bacteria were extracted, and then PCR was used to amplify the target genes. Meanwhile, the anaerobic culture and biochemical events were used to verify PCR results. The sensitivity and specificity of PCR were also evaluated with the reference bacteria. In addition, the gingival index of each individual was recorded.  Results  The multiplex PCR was able to detect a minimum of 1pg bacteria DNAs corresponding to 20 cells of Aa, Fn and Pg as well as 80 cells of Bf. With good specificity, four species of bacteria were detected target fragments but the E.coli was not. The positive rate of PCR assay was coincident with the bacteria culture (P>0.05). There were statistically significant differences in detection results of Aa, Fn and Pg between patients and healthy individuals（P<0.05）, while no difference in the detection result of Bf(P>0.05). The analysis of spearman rank correlation indicated that the gingival index had positive correlation with the presence of Aa, Fn and Pg (P<0.01) while no correlation with Bf (P>0.05). Conclusion  With high sensitivity and specificity, the multiplex PCR can be used to detect Aa, Bf, Fn and Pg simultaneously and to observe changes of bacteria induced by wearing fixed orthodontic appliances.

Key words: Fixed orthodontic appliances; Multiplex PCR; Bacteria detection