A biocompatible microporous composite of PMMA (poly-methyl-methacrylate), PHEMA (poly-hydroxyl-ethyl-methacrylate), and calcium hydroxide (HTR) or autogenous osseous coagulum (AOC) bone replacement grafts were evaluated in 15 pairs of mandibular molar Class II furcations in 9 patients. Following initial preparation, full thickness flaps were raised to gain access to the furcations; mechanical hand and ultrasonic root and defect debridement and chemical (tetracycline) root preparation were performed; paired furcations in each patient were randomly grafted with either HTR or AOC; and the host flaps replaced or slightly coronally positioned. Weekly, then monthly, deplaquing was performed until surgical re-entry at 6 to 12 months. Both treatments improved the clinical status of the treated furcations. Direct clinical measurements demonstrated essentially equivalent clinical results with both bone replacement graft materials related to most hard and soft tissue changes in the furcations. Differences in favor of HTR were found for horizontal residual furcation depth (2.4 mm vs. 3.9 mm), horizontal furcation fill (1.9 mm vs. 0.8 mm), and percent horizontal furcation fill (44.4% vs. 17.1%) (all P < or = 0.05 paired t test). These favorable results with HTR polymer are similar to several reports with other graft materials and with GTR barriers, and suggest that HTR polymer may be a useful therapeutic adjunct in the clinical management of grade II mandibular molar furcations.