The feasibility of using infra-red radiation in determining tooth-vitality

• Main Author: Lancaster, Paula Elizabeth
• Other Authors: Brettle, David S. ; Carmichael, Fiona ; Clerehugh, Val
• Published: University of Leeds 2018
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.759784

The aim of this Study was to investigate the feasibility of infra-red radiation determining human tooth-vitality, the basis being that a vital tooth with an internal blood-supply may emit more infra-red radiation and be warmer than a non-vital tooth. The commonest pulp tests are sensibility tests which assess the ability of the nerve fibres within the pulp to respond to a stimulus applied to the tooth, rather than assess the pulp blood-flow. Development of the vitality test involved cooling the tooth-tissues and capturing the emitted infra-red radiation of re-warming with a thermal camera. Cooling and re-warming of tooth-slices enabled calculation of thermal conductivity and thermal diffusivity of the mineralised tissues - enamel and dentine - and production of a thermal map which characterised these. Sixteen extracted human molar teeth were tested in a cross-over-study with simulated vitality at four flow-rates: 0.5ml/min, 0.15ml/min, 0.08ml/min and 0.03ml/min under two conditions: pulsed and non-pulsed. The cross-over-design allowed paired testing of the same tooth and independent testing of two dissimilar teeth. The area under the re-warming curve between vital and non-vital teeth was statistically tested. Statistical significance was shown between the paired vital and non-vital teeth at all pulsed flow-rates, and non-pulsed flow-rates of 0.15ml/min and 0.5ml/min. Only the pulsed flow-rate of 0.5ml/min was significant for dissimilar teeth. A thermal map demonstrated re-warming of the vital tooth before the non-vital tooth. The results suggest infra-red radiation may determine tooth-vitality when the teeth are of the same size and shape, with a blood-flow of 0.03ml/min or above. This could be a realistic blood-flow for the human tooth. Testing teeth of differing size and shape may determine vitality at a blood-flow of 0.5ml/min - higher than realistically expected in the human tooth. Clinically, the vitality test between a vital and non-vital root-treated tooth points to this model being inverted. This may be due to the insulating nature of the materials used to restore the non-vital tooth. Further clinical investigation is justified to validate the vitality test.