Observations on the recovery of sensation following inferior alveolar nerve injuries.

The recovery of sensation to the lower lip and chin following unilateral inferior alveolar or mental nerve injuries has been examined in 21 adult patients for periods of up to 45 months. Sensory testing was performed using light touch, pin prick and thermal stimuli as well as testing for sharp/blunt differentiation, localisation and two-point discrimination. The area of anaesthesia to light touch stimuli had disappeared by 4 months after nerve compression and by 3.5-8 months after nerve section, but persisted after nerve section if nerve regeneration was impeded. In this latter group there was a significant reduction (mean 65%) in the area of anaesthesia by 1 year post injury and this would be consistent with the development of a collateral reinnervation. Nerve section injuries and 46% of the nerve compression injuries resulted in a persistent sensory abnormality. The tests most likely to reveal this abnormality were localisation, pin prick threshold and two-point discrimination.