Description:
<jats:p><jats:bold>Abstract.</jats:bold> The furcation involvement of 100 molars in 25 patients suffering from moderate to advanced periodontitis was investigated. Presurgically, the horizontal probing attachment level (PAL‐H) within the furcations was assessed 2 × within 14 days. To determine the measurement error of PAL‐H, the standard deviation of single measurements was calculated. The measurements were repeated intrasurgically and compared with presurgical assessments of furcation degrees. The overall standard deviation of single measurements was 0.739 mm. For buccal, lingual, mesiolingual and distolingual furcations, the standard deviations were 0.602 mm, 0.559 mm, 0.759 mm, 1.099 mm, respectively; measurement error was less in buccal and lingual furcations than in distolingual furcations (<jats:italic>p</jats:italic><0.001). The agreement of replicate measurements of furcation degrees was excellent for buccal, lingual and mesiolingual furcations (weighted κ– coefficients between 0.776 and 0.944), but only moderate for distolingual furcations (κ<jats:sub>w</jats:sub>= 0.706). Multiple linear regression analysis revealed significant influence of furcation depth, width and furcation location on differences of PAL‐H (<jats:italic>p</jats:italic><0.05). There was no significant difference between furcation degree as assessed presurgically and intra‐surgically.</jats:p>