The thirty-three maxillary first molars, which were extracted because of the severe periodontal disease, were cross sectioned every 1.5 millimeter from the Cementoenamel junction to the apex, and each section was photographed, projected and measured with a calibrated Digital Curvi-Meter (Corn Curve-8, Japan). The root surface area (RSA), percentage of´ the RSA, and the linear variation of the RSA were calibrated for each 1.5mm section: The location of root separation was determined and the length of roots were calculated separately.
The results were as follows:
1. The mean length of the roots were 11.52mm for the palatal root, 1 1.28mm for the mesiobuccal root, and 10.68mm for the disobuccal root. The distobuccal root was shortest among the three roots.
2. The mean distance from the Cementoenamel junction to the point at which the roots separate from the root trunk was 4.57mm for the mesiobuccal root and 4.66mm for the distobuccal root. The mesiobuccal root separation was more coronal than the distobuccal root separation but the differences were not significant.
3. The mean root surface area was 88.44mm2 for the mesiobuccal root, 80.14mm2 for the palatal root, and 58.87mm2 for the disobuccal root. The mean mesiobuccal root surface area was wider than the mean palatal root surface area (p < 0.05).
4. The mean surface area of the root trunk was 155.67mm2 and averaged 40.63% of the total root surface area. It was wider than the mean surface area of each roots.
5. The coronal one-half of the root length accounted for approximately 60% of the total root surface area.
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