Impact of Porphyromonas gingivalis inoculation on ligature-induced alveolar bone loss. A pilot study in rats

Abstract

Periodontitis is a polymicrobial infection characterized by the loss of connective tissue attachment, periodontal ligament and alveolar bone. The aim of this study was to evaluate the impact of Porphyromonas gingivalis inoculation on the ligature-induced alveolar bone loss (ABL) model in rats. Forty male Wistar rats were randomly assigned to the following groups: G1, control (n = 10); G2, ligature-induced ABL (n = 15); and G3, ligature-induced ABL + P. gingivalis inoculation (n = 15). Rats in G2 and G3 were killed 15, 21 and 30 d after ligature placement, and the following parameters were assessed: microbiological load; ABL; and interleukin (IL)-1β (Il1beta)/Il1ra, Il6/Il10 and Rankl/osteoprotegerin (Opg) mRNA ratios in the gingival tissues, as determined by quantitative PCR. Microbiological analyses demonstrated that rats in G1, G2 and G3 were positive for the presence of bacteria (determined using PCR amplification of the 16S gene), but that only the treatment sites of rats in G3 were positive for P. gingivalis at all time-points investigated. Histometrically, significant bone loss (p<0.001) was observed for both ligated groups (G2 and G3) compared with the nonligated group (G1), with higher ABL observed for G2 at all the experimental time-points. Furthermore, gene-expression analysis demonstrated that the presence of P. gingivalis in the dentogingival area significantly decreased the Il1β/Il1ra, Il6/Il10 and Rankl/Opg mRNA ratios compared with ligature alone. Within the limits of this pilot study, it was concluded that inoculation of P. gingivalis affected the ligature-induced ABL model by the induction of an anti-inflammatory and antiresorptive host response.