The effect of wavelength, bandwidth, and probe design and position on assessing the vitality of anterior teeth with laser Doppler flowmetry.

OBJECTIVES

To investigate the effect of four variables: wavelength (633 nm and 780 nm), bandwidth filter (3 kHz, 15 kHz, 22 kHz), probe fibre separation (250 microns) and 500 microns) and distance of the probe from the gingival margin (2-3 mm and 4-5 mm) when assessing the vitality of anterior teeth with a laser Doppler flowmetry system.

DESIGN

Split-mouth cohort clinical trial.

SETTING

Childrens dental clinic, Glasgow Dental Hospital and School.

SAMPLE AND METHODS

Sample included 11 non-vital maxillary incisors with necrotic pulps in 10 patients (mean age 12.25 years old). Recordings were taken from the non-vital tooth and from a vital maxillary incisor from the same patient, using all 24 combinations of the recording variables listed above. The vital/non-vital ratios of the signals from the 11 pairs of teeth were calculated and discriminant analysis applied to the data.

RESULTS

Of the variables investigated, the combination of a 633 nm laser source with a 3 kHz bandwidth filter using a probe with a 500 microns fibre separation placed 2-3 mm from the gingival margin was the most reliable, with 10 out of a possible 11 true positives for pulpal necrosis, no false positives, and one equivocal diagnosis, and was the only combination that recorded a smaller blood flow from the non-vital tooth compared with the vital control tooth for all 11 pairs of teeth investigated.

CONCLUSIONS

It was concluded, therefore, that laser Doppler flowmetry can be of use in assessing the vitality of anterior teeth and that this is the preferred combination of recording variables for further investigations.