An automatic scaling apparatusthat simulated the scaling process of hand instrumentation was developed to quantitatively analyze the cutting quality and abrasive resistance of sealers. We first tested 4 synthetic resins as the abraded material. Of the 4 synthetic resins tested, polycarbonate resin proved most similar to dentin. The effects of lateral scaling forces (700, 500, and 300 dyne) and sealer angles (70° to 95°) on the cutting quality and abrasive resistance of sealers were evaluated quantitatively by the amount of the abraded material worn away in 1,000 strokes. Comparison of the 3 scaling forces showed a greater amount of abrasion at higher force than that at lower force. This suggests that the decrease in the amount due to abrasion could be compensated by increasing the lateral scaling force. Regarding the sealer angle, results indicated that the amount of material removed increased with an increase of the sealer angle up to 70°, but then rapidly decreased at an angle of 90° or more. The most effective scaling angle was 87°, and this was not affected by scaling force. These results suggest that a greater amount of removal could be obtained at a scaling angle of 87° and a scaling force of 700 dyne. The present findings suggested the automatic scaling apparatus could be a useful tool for quantitatively evaluating the cutting quality and abrasive resistance of sealers.J Periodontol 1995; 66:62–68.