Probing site configuration in patients with untreated periodontitis. A study of horizontal positional error

This study examined the morphology of 487 probing sites in patients with untreated periodontitis, using a constant force probe (0.25 N, 0.5 mm) and flexible stent with guide grooves, at 3 adjacent points per site, 6 sites per tooth. Sites were classified into 9 configuration types according to the relationship of the 3 adjacent points. Duplicate measurements were made and sites were analysed with special reference to whether a slight horizontal movement was likely at the second examination. 60% of individual point probing measurements were exactly reproduced, but only 23% of site configurations. 65% of configuration change was accountable on the basis of slight horizontal shift of the probe. Only 13% of configurations required the postulate of other forms of probing error. These results suggest that probing reproducibility is not always an indication of site reproducibility, and that the variation of probe position in the transverse plane is an important source of probing error, even when a stent is used.