Background and objectives
It is recognized that orthodontic force has an aggravating effect on the progression of destructive periodontitis if periodontitis have not been well controlled. However, the underlying mechanism is not completely clear. This study was to investigate the effect of antibiotic administration on orthodontic force-aggravated, ligature-induced experimental periodontitis in mice.
Methods
C57BL/6 mice (male, 8-week old) were divided into three groups (n=8). Silk ligatures (SL) were tied around the maxillary right (Group 1) or both (Groups 2&3) first molars on Day 0, removed on Day 8, and systemic antibiotics (SA) was administered through drinking water (Group 3) since Day 8. Orthodontic force (OF) was applied on the maxillary right first molars since Day 13 (Groups 2&3). All mice were sacrificed on Day 20.
Results
Total oral bacteria load was significantly higher in Group 2 when compared to Group 1 on Day 20, whereas such count was greatly reduced in Group 3 when antibiotics were administered. Periodontal bone loss (PBL) was significantly increased on SL side vs. control side in Group 1. PBL was significantly increased on OF+SL side vs. SL side in Group 2 (p < 0.05) but not in Group 3 when SA was administered. Gingival mRNA and protein expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) / osteoprotegerin (OPG) were significantly increased on OF+SL side vs. SL side in Group 2 (p < 0.01) but not in Group 3. However, comparable levels of TRAP+ cell formation within periodontal space and tooth movement were observed on OF+SL side in Group 2 and Group 3.
Conclusion
Our results suggest that reduction of oral bacterial load by antibiotic administration alleviate orthodontic force-aggravated periodontitis bone loss.