THE DENTAL PULP 



221 



scarcely be any doubt. Dentine is an extremely sensitive 

 structure. Healthy dentine, when fractured without 

 exposure of the pulp, is usually very sensitive ; it is also 

 a common clinical observation that in coning a living tooth 

 for crowning, when the enamel has been removed, the 

 grinding of the dentine causes acute pain. 



In the excavation of a carious tooth, although little 



FIG. 137. Diagram. Scheme of distribution of the nerves of the pulp. 

 m. Axis cylinder of medullated nerve ; x. medullary sheath ; p. nerve 

 plexus ; s. synaptic terminations ; n. nerve-end cell ; dn. dendrons ; 

 a. axon ; o. odontoblasts ; d. dentine ; /. dentinal fibril. 



pain is felt on removal of the superficial layers, when the 

 lowest layer is raised from the healthy dentine beneath the 

 pain is acute. From these and other observations we must 

 conclude that sensory nerve fibres are distributed to the 

 dentine, but the question arises whether all the nerves .of 

 the pulp are made up of sensory fibres. We know also that 

 the surface of an exposed pulp is very sensitive, so we must 

 suppose that sensory fibres are distributed to the odonto- 

 blast layer. We should, therefore, imagine that both sensory 



