Reproducibility and validity of furcation measurements as related to class of furcation invasion.

The furcation involvement of 200 molars in 50 patients suffering from advanced periodontitis was investigated. Presurgically, the horizontal probing attachment levels (CAL-H) within the furcations of 4 molars per patient was assessed twice within 14 days. Within a subset of 11 patients duplicate measurements of clinical probing depths (PD) and vertical clinical attachment levels (CAL-V) at the same molars were performed. To determine the measurement error of CAL-H, PD and CAL-V, respectively, the standard deviation of single measurements were calculated. The CAL-H measurements were repeated intrasurgically and compared with presurgical assessments of furcation measurements. The overall standard deviation of single measurements was 0.759 mm. For Class 0, I, and II furcations, the standard deviations were 0.879 mm, 0.664 mm, 0.682 mm, respectively. The standard deviation of PD single measurements and CAL-V single measurements varied from 0.393 mm to 0.993 mm (PD) and from 0.555 mm to 1.161 mm (CAL-V), respectively. The agreement of replicate measurements of furcation degrees was moderate for furcation locations which showed a CAL-H < or = 3 mm and a CAL-H > 3 mm, respectively (weighted kappa-coefficients 0.500 and 0.691). At sites with furcation involvement Class O and II there was no statistically significant difference between presurgical and intrasurgical measurements. At sites with Class I furcations there was a statistically significant mean difference of 0.255 mm between presurgically and intrasurgically assessed CAL-H. There was no statistically significant difference between furcation classes as assessed presurgically and intrasurgically (chi 2 between 1.9 and 4.4).