An assessment of the validity of a constant force electronic probe in measuring probing depths.

Reproducible and accurate measurement of probing depth and attachment levels is important in longitudinal studies and clinical monitoring of patients. The aim of this study was to determine the validity of a constant force electronic probe in comparison with a conventional probe in measuring probing depth. Thirty-three teeth scheduled for extraction from 15 patients were used in the study. Probing depths were measured with a constant force electronic probe and a conventional probe at six sites per tooth prior to extraction. The teeth were extracted, washed, and stained and the actual probing depth measured in the laboratory. The constant force electronic probe showed a consistent systematic bias to under measure pocket depths. The mean difference was 0.48 mm, which was statistically significant (P < 0.01). The conventional probe over measured by a statistically non-significant mean of 0.08 mm (P > 0.05). The measurements with the constant force electronic probe were not affected by the site or the position of the tooth in the mouth. The study demonstrated that the constant force electronic probe under measured the probing depths as determined in the laboratory and was less valid than the conventional probe. However, the validity of probing depth measurements using the constant force electronic probe was clinically acceptable.