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Aim To analyse 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 oestrogen 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 were 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 oestrogen 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 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 jawbone thickness in post-menopausal females. [ABSTRACT FROM AUTHOR]