Microbial population changes in patients with medication-related osteonecrosis of the jaw treated with systemic antibiotics.

Objective: This study aimed to investigate the bacterial population in patients with medication-related osteonecrosis of the jaw (MRONJ) after treatment with doxycycline and metronidazole.

Study Design: A total of 38 patients with MRONJ (age range 55-88, mean age 73 + 8.82 standard deviation) treated with doxycycline first and with metronidazole second were enrolled in this study. Two swabs were taken at the margin of the infected MRONJ lesion after applying pressure on the marginal mucosa, and visible pus was secreted. Real-time polymerase chain reaction was used to analyze 20 periopathogenic and commensal species and the total bacterial level. Bacterial counts were compared between antibiotic treatments and with a control group of orally healthy patients who didn't have periodontal pockets of more than 3 mm (n = 29) by means of a Mann-Whitney U test. Comparisons between the two antibiotic treatments were performed by a paired Wilcoxon signed rank test.

Results: The total bacterial level was significantly higher in the MRONJ patients treated with systemic antibiotics compared with the control group. However, significant lower bacterial amounts were found for 12 of the 20 investigated bacteria. We couldn't establish a significant advantage of metronidazole administration after doxycycline treatment.

Conclusion: Our findings suggest that the total bacterial level in MRONJ patients is higher even when treated with systemic antibiotics. The significantly different bacterial amounts of the selected species suggest an alteration in the microbial population.