Involvement of afferent nerves in pulpal blood-flow reactions in response to clinical and experimental procedures in the cat

A unilateral resection of the mandibular nerve ( n = 20) was made 10–14 days before investigation of the contribution of afferent nerves in vasodilator reactions in the dental pulp. Lower canine teeth were subjected to various stimuli and pulp blood-flow responses monitored by laser Doppler flowmetry. An absence of response to bipolar electrical (5 impulses, 50 μA, 5 ms, 2 Hz) stimulation on the tooth surface was used to demonstrate a successful chronic nerve lesion. Local application of capsaicin (10 −4 M) in a deep dentinal cavity induced a long-lasting increase in pulpal blood flow in control teeth only. Bradykinin (10 −3 M) induced significantly larger responses in control than in denervated teeth (58.3 ± 9.8% and 24.5 ± 4.9%, respectively, p < 0.005, n = 8); in addition, the onset was slower and the duration of the response significantly (60%) shorter than in control teeth. Intermittent grinding of surface dentine instantly increased flow in control teeth by 53.0 ± 12.5% ( n = 12) whereas in denervated teeth the response was delayed and significantly (70%) smaller. Deeper preparation produced responses of similar magnitude in control and denervated teeth (69 and 50%, respectively) but the onset was delayed in denervated teeth. Low-intensity ultrasonic stimulation caused vasodilation in intact teeth (38% increase) but had no effect in denervated teeth. This effect was abolished after local anaesthetic (mepivacaine) injection. Sympathectomy ( n = 3) did not influence stimulation-induced blood-flow responses in the dental pulp. The results show that afferent nerves make an important contribution to haemodynamic reactions in the pulp in response to experimental and clinical procedures directed at the tooth.