Two hundred and sixty-nine teeth were used for studying the relation between the level of existing periodontal supporting tissues and the area of the root surface. The new method developed by improving the so-called membrane technique is simple and easy to employ.
The root was coated with vinyl acetate solution twice. The same coating procedure was repeated with alpha-cyanoacrylate monomer. After setting, the membrane was stripped off from the root surface using a disposable blade. The outline of the removed membrane was drawn on the tracing paper and enlarged 10 times photographically. Transparent film with grids (2mm×2mm) was then laid on the enlarged membrane, and the area was calculated by counting the grids. Prior to this procedure, the reproducibility of this method was evaluated: acrylic cylindrical test body (8.0mm diameter, 10.0mm height) was measured 10 times on the same way described above.
The difference between measured and calculated value was 4.2±0.3% and the coefficient of variability was 0.27%. These results indicate that this method is highly reproducible.
The means of the total area of root surface were as follows: upper central incisor: 203.0mm2, upper lateral incisor: 199.0mm2, upper canine: 291.4mm2, the upper first premolar: 252.1mm2, the upper second premolar: 243.3mm2, the upper first molar: 494.5mm2, the upper second molar: 421.3mm2, lower central incisor: 175.0mm2, lower lateral incisor 193.0mm2, lower canine: 246.0mm2, the lower first premolar: 221.6mm2, the lower second premolar: 234.1mm2, the lower first molar: 390.9mm2, the second molar: 347.1mm2.
On the upper jaw, there were neither statistically different between the total area of root surface of central incisor and of lateral incisor, not between of the upper first premolar and of the upper second premolar. On the lower jaw no statistical differences were found between the total area of root surface of the canine and of the first premolar, nor between of the first premolar and of the second premolar.
