Role of Actinomyces in the progression of medication-related osteonecrosis of the jaws in an immunocompromised mouse model with periapical disease

Objectives

This study aimed to investigate the role of Actinomyces on the development of MRONJ in an immunocompromised mouse model with periapical disease.

Methods

Thirty ovariectomized C57BL/6 N female mice were treated with zoledronic acid (ZA) and dexamethasone (DX) for 12 weeks. At the eighth week of drug administration, pulpal exposure operation was performed on the lower right first molar in Group B and C, meanwhile Actinomyces inoculation was performed at the pulpal entrance of Group C. Group A received no operation as control. After 4 weeks, loads of total bacteria and Actinomyces in the oral cavity were assessed by real-time polymerase chain reaction (PCR). Mandibles were harvested for micro-computed tomography (CT) and histological analysis.

Results

Real-time PCR revealed positive detection of Actinomyces in 30% samples in Group C and negative detection in all samples in Group B and control group. Micro-CT examination demonstrated that in ZA treated mice, pulpal exposure significantly increased periapical bone loss, which was significantly aggravated by Actinomyces inoculation. Histological assessment showed vasodilation, acute exudative changes and pulp necrosis in Group B and C.

Conclusions

The present study revealed that inoculation of Actinomyces compromises the bone quality but does not further aggravate bone necrosis significantly.