Retrograde amnesia after intravenous sedation and general anaesthesia in a dental hospital.

Midazolam, a benzodiazepine, is commonly used for intravenous sedation for dental procedures and, together with other benzodiazepines, can cause anterograde amnesia. Retrograde amnesia, however, is rare. It is defined as a loss of access to memory of events that occurred, or information that was learned, before the injury or event that caused the amnesia. We know of no reports of this occurring after the intravenous use of midazolam alone and few after general anaesthesia. We present two cases of retrograde amnesia: one after intravenous sedation and one after general anaesthesia.

Cannabinoid receptor CB1-immunoreactive nerve fibres in painful and non-painful human tooth pulp.

The cannabinoid receptor CB1 is involved in modulation of neuronal hypersensitivity and pain. The aim of this study was to evaluate CB1 receptor levels for the first time in dental pain. A total of 19 patients due for molar extraction were divided into two groups, those with existing dental pain (n=9), and those with no history of pain (n=10). Immunohistochemistry and computer image analysis was used to evaluate CB1-positive nerve fibres in tooth pulp, with neurofilament-immunostaining as a structural nerve marker. CB1-immunoreactive nerve fibres were scattered throughout the tooth pulp and often seen in nerve bundles, but the fibres did not penetrate the subodontoblastic layer. There was no statistically significant change in the CB1 nerve fibre percentage area in the painful group compared to the non-painful group (p=0.146); the neurofilament fibres were significantly reduced in the painful group compared to the controls (p=0.028), but there was no difference in the ratio of CB1 to neurofilaments between the two groups. Thus, CB1 expression is maintained by nerve fibres in painful human dental pulp, and peripherally-restricted CB1 agonists currently in development may advance the treatment of dental pain.