AIM To analyze the effect of systemic application of N-methyl pyrrolidone (NMP) on the pulp-dentine complex and on the jawbone of ovariectomized rats. METHOD Female Sprague-Dawley rats were randomly divided into a sham-operated group (Sham n=6) and an estrogen depletion by ovariectomy (OVX n=12) group. In 6 of the ovariectomized animals N-methyl pyrrolidone (NMP) in phosphate-buffered saline (PBS) was administered systemically weekly by intraperitoneal injection (i.p.); the other 6 were injected with PBS (Veh). After 15 weeks of injections the jaw bones were collected and pulps extracted from the incisors teeth. Histology was used to determine pre-dentine thickness in teeth and radiography to determine alveolar bone mass. Immunohistological staining and RT-PCR were performed to verify the presence and localization of the odontoblast specific dentine sialoprotein and to quantify its expression in the dentine pulp complex. Mandibular cortical width and mandibular height was evaluated by means of X-ray analysis. Statistical analysis was performed with analysis of variance (ANOVA). RESULTS Both pre-dentine (P=0.029) and alveolar bone structures (P=0.049) were significantly reduced due to estrogen deficiency in OVX Veh and OVX NMP treatment normalized these parameters to the Sham level. DSPP expression in OVX NMP animals was significantly higher (P=0.046) than in OVX Veh. X-ray analysis confirmed that ovariectomy significantly reduced the mandibular cortical width in the OVX Veh group compared to the Sham Veh and OVX NMP (P=0.020). CONCLUSION N-methyl pyrrolidone (NMP) had a remarkable anti-osteoporotic ability preserving the activity in the pulp-dentine complex and preventing jawbone loss. These effects make NMP a promising candidate for the preservation of the activity of the pulp-dentine complex and the jawbone thickness in postmenopausal females. This article is protected by copyright. All rights reserved.