Visual and tactile observational error: comparative probing reliability with recession and cementoenamel junction measurements.

Probing error may arise from several sources, including visual observations and tactile detection of the cementoenamel junction (CEJ). This study examined two types of probe scale in relation to measurements of recession and CEJ from a flexible stent, and two types of probe design in addition, in relation to CEJ detection. 492 sites were studied in six patients with untreated periodontitis. Following stent construction, patients attended for measurement of recession and probing depth. This was repeated after 1 h, and then calculus was scaled in the vicinity of the CEJ. One week later, patients attended for CEJ measurements, which were similarly repeated. Measurements with an offset scale (between marks) were more reproducible in general, though no significant difference was detected between recession scores. The most reproducible detection of the CEJ was with a modified Cross calculus probe with an offset scale. A curious feature of the results was a bias affecting 9% of the recession measurements. It is possible that edematous enlargement of the gingiva occurred after the first measurement of probing depth, and was occasionally sufficient to alter the recession score.