Accuracy and reproducibility of two manual periodontal probes. An in vitro study

Periodontal probe is the standard instrument for assessment of probing pocket depth and clinical attachment level. However, probing measurements have inherent measurement errors from a wide range of sources, such as instrument, patient, examiner and disease status.

The purpose of the present study was to create an in vitro model simulating gingival sulcus/pocket and investigate the accuracy and reproducibility of two different manual probes.

Thirty-three aluminium blocks with dimensions of 2 x 2 cm and thickness ranging from 2.00 to 10.00 mm were constructed. Holes with a diameter of 1.00 mm were made in the blocks through the whole thickness. These 33 aluminium blocks were then carefully stuck together so that the probing faces would be on the same level. A plastic material, which shows deformation with forces >45 g was placed at the base of the blocks. Two conventional manual probes (Williams and WHO probes) were used in the present study. Seventeen periodontists were selected to perform duplicate measurements on the blocks over two visits using both of the probes. The intra- and inter-examiner percentage accuracy (with regard to 0.25 mm) and reproducibility for each of the duplicate measurements was calculated and analysed using repeated measure analysis of variance (ANOVA) (three factor experiments with repeated measure on two factors; probe and probing session).

ANOVA showed statistically significant differences between the examiners (p=0.000) and between the two readings of each probe (p=0.002), while the differences between the two probes were not statistically significant (p=0.098). The overall percentage of accuracy was higher with WHO probe compared with Williams probe. Kappa analysis revealed better reproducibility percentages for WHO probe in comparison with Williams probe.

This in vitro study, using a metal construction and a plastic material with a deformation coefficient similar to that of gingival pocket, may be suggested as a good model to test intra- and inter-examiner differences in periodontal probing. Our findings emphasise the importance of inter-examiner calibration for probing, particularly in longitudinal studies.