Mechanisms of pain arising from the tooth pulp

Toothache is one of the most common and unpleasant pain sensations experienced by man. Unfortunately, it is also fairly resistant to normal analgesics, and affected individuals can suffer severe symptoms and disturbed sleep. Tooth decay (caries) is the main cause of pulpal inflammation, which, in turn, may cause dental sensitivity or spontaneous pain. On occasions, the management of advanced tooth decay and pulp inflammation regrettably necessitates root canal therapy (removal of the dental pulp) or an extraction.

Our research group has a particular interest in pain mechanisms, and the tooth pulp provides us with an extremely valuable and interesting experimental model of inflammatory pain.

Human tooth pulp

Experimental approach

Essentially, we use pulp tissue obtained from patients requiring tooth extraction (with their informed consent) to try to correlate reported pain symptoms with histological findings. We use immunocytochemical techniques to specifically label a variety of structures including nerves, blood vessels and immune cells.

In addition, we have been studying a range of neuropeptides, neurotransmitters, and ion channels to gain a greater insight into the more subtle neural changes underlying pain and neurogenic inflammation. Our analysis of immunolabelling is both qualitative and quantitative and relies principally on the use of sophisticated image analysis software.

Key findings

To date, our investigation of the tooth pulp, both in health and disease, have revealed some notable findings. Some of these are summarised below:

  • With caries progression there is a significant increase in the overall density of pulpal nerves, although this increased innervation does not appear to be associated with reported pain symptoms. It is likely, however, that this neural proliferation has importance in inflammation and healing.

Photomicrographs of human tooth pulp


  • There is a marked increase in the neural expression of substance P, (a neuropeptide with nociceptive function) in teeth from patients with toothache, when compared to teeth with a similar degree of caries, but no symptoms. This suggests that substance P plays a key role in painful pulpitis.

Photomicrographs of human

  • The vanilloid receptor, TRPV1, also shows a significant increased in expression in painful pulp tissue, and may also have an important role in dental pain.
  • There are differences between the innervation, immune cell accumulation and vascularity in human primary and permanent teeth, and this may have biological and clinical importance.

Future directions

We are keen to further our knowledge and understanding of the basic neural mechanisms associated with dental pain and inflammation. We hope that a greater appreciation of these cellular events will ultimately lead to improved clinical management of dental pain for our patients, young and old.

Funding

This area of research has been funded by grants from:

  • MRC
  • Royal College of Surgeons
  • Shirley Glasstone Hughes Memorial Prize Fund
  • Proctor & Gamble
  • GlaxoSmithKline

Key Staff

Names link through to personal profiles where available.

Key recent publications

Comparative immunohistochemical analysis of the peptidergic innervation of human primary and permanent tooth pulp. H D Rodd and F M Boissonade. Arch Oral Biol. 47; 375-85, 2002.

Immunocytochemical investigation of neurovascular relationships in human tooth pulp. H D Rodd and F M Boissonade. J Anat. 202;195-203, 2003.

Vascular status in human primary and permanent teeth in health and disease. H D Rodd and F M Boissonade. Eur J Oral Sci. 113; 128-34, 2005.

Vanilloid receptor 1 expression in human tooth pulp in relation to caries and pain. C R Morgan, H D Rodd, N Clayton, J B Davis and F M Boissonade. J Orofac Pain. 19; 248-60, 2005.

Immunocytochemical investigation of immune cells within human primary and permanent tooth pulp. H D Rodd and F M Boissonade. Int J Paediatr Dent. 16; 2-9, 2006.