Probing bone level measurements for determination of the depths of Class II furcation defects.

Background: Probing bone measurements as an alternative to open bone measurements to evaluate regenerative procedures in furcation defects do not seem to be used as yet. The purpose of the present study was to investigate the reliability of probing bone measurements in such defects.

Methods: Fifteen patients scheduled for surgical treatment of a total of 30 mandibular molars with buccal or lingual Class II furcation defects were studied. During treatment, duplicate vertical and horizontal recordings of probing attachment levels, probing bone levels, and open bone levels were taken by independent examiners.

Results: Deviations of both vertical and horizontal recordings between the first and second examiners were within +/-1 mm in 90% to 100% of examined sites for all 3 measurements. Standard deviations of differences between pairs of duplicate recordings were also similar for the 3 measurements both for vertical and horizontal defect dimensions and amounted to 0.7 to 0.9 mm. On average, vertical and horizontal open bone levels were 0.9 to 1.1 mm deeper than probing bone levels. Probing bone levels, in turn, were 1.1 to 1.5 mm deeper than probing attachment levels.

Conclusions: In view of the consistency demonstrated between probing bone level and open bone level measurements in mandibular Class II defects, coupled with the additional discomfort for the patient of a reentry surgery and a possible reentry traumatic effect, open bone level measurements do not seem necessary or even justified to evaluate effects of periodontal therapy in these defects, and can be substituted by probing bone measurements.