[Comparative study of 3 irreversible hydrocolloids].

This study was realized: to determine the best manipulation of 3 alginates; to compare their dimensional stability; to compare their reproduction of detail; to evaluate, through these 3 criteria, the best of the 3 alginates. It seems necessary to point out that: The 3 examined alginates show a poor dimensional stability on account of the deformations produced during the setting time and the removal of the impression. The immediate pouring of the model gives the best results, because storing the impression is accompanied by dimensional changes. The other methods of conservation seem considerably less accurate. The reproduction of detail is excellent with the 3 alginates. The accuracy is of 25 micrometer, but it is not possible to take advantage of this quality, because the compatibility and the accuracy of model stone are insufficiently adapted to the properties of the alginates. CA-37 is, among the 3 studied alginates, the one which gave the worst results with regard to the ease of manipulation and compatibility with Vel Mix Stone.