Background: Osteoporosis is a metabolic bone disease, which impairs and/or delays the regenerative response of calcified tissues.

Aim: The aim of this study was to assess the histopathologic response to direct pulp capping in osteoporotic rats that received a preoperative treatment with Zoledronic acid, a bisphosphonate which is currently prescribed for treating osteoporosis.

Methodology: Two groups, each with 7 osteoporotic female Wistar rats (n=7) received either an intravenous dose of 100 mg/kg of Zoledronic Acid (Group 1) or the same volume of sterile saline (Group 2). One week later, the pulps of the right and left mandibular first molars of each animal were exposed and capped with Biodentine. After 20 days the animals in Group 1 received a second similar dose of Zoledronic acid and Group 2 a similar second dose of sterile saline. After 38 days the animals were euthanized and a total of 28 teeth (14 per group) were prepared for histologic analysis evaluating the following parameters: inflammation, reparative hard tissue formation, odontoblast cell layer organization, fibrous tissue, and necrosis.

Results: In Group 1 the reparative hard tissue formation was scarce with preservation of the pulp tissue structure and the odontoblast cell layer. In Group 2 the pulp was preserved as a fibrous reticular-like structure. Reparative hard tissue formation was totally absent and the odontoblast cell layer was atrophic or absent. In both groups, no inflammation or necrosis was observed.

Conclusions: The intravenous administration of Bisphosphonate (Zoledronic Acid) did not promote pulp healing in osteoporotic rats.