EFFECT OF PROBE DESIGN ON THE SUITABILITY OF LASER-DOPPLER FLOWMETRY IN VITALITY TESTING OF HUMAN TEETH

The aim of this investigation was to study the influence of probe desi gn on the signal output from the dental pulp in experiments with laser Doppler flowmetry (LDF). Eighteen patients 14 to 39 years of age were examined. Recordings were made from a maxillary and a mandibular cent ral incisor and a maxillary canine with an infrared laser Doppler flow meter. The radiographic appearance of the tested teeth was within norm al limits and all teeth responded normally to electric pulp testing (E PT). Five configurations of probes were used. Each probe had 3 fibers arranged in a triangle. One fiber carried the laser light to the pulp tissue and 2 fibers carried the backscattered light to the detector gi ving the signal output. The diameter of each of the 3 fibers in the pr obe was 200 mum except in 1 probe where the diameter of the fibers was 125 mum. The distance between the 3 fibers in the triangular arrangem ent in each probe was 250, 500, 800, 1000, and 1500 mum. A special rub ber base splint was used to hold the probe in place on the buccal surf ace of the tested teeth. The output signals from the LDF were fed into an analog printer and a lap top computer where all calculations were done. The probe with the largest separation of the fibers produced sig nificantly higher output signals from the maxillary and mandibular inc isors than the other probes. The same probe also produced significantl y higher output signals than the smaller probes from the maxillary can ine with the exception of the 200/800 probe. The output signals were s ignificantly higher from the mandibular incisor than from the maxillar y incisor and canine. Consecutive recordings with the LDF from the max illary incisor in 5 patients within 1 hour gave coefficient of variati on from 7.9% to 10.3% in output signals. The results of this study sho wed that all 5 experimental probes gave output signals indicative of b lood flow in the dental pulp and the probe with the largest separation of fibers seemed to be the most suitable one under the experimental c onditions used. It appeared to be possible to make reproducible record ings from the pulp of the teeth under the experimental conditions used .