Much research has been done of color science relative to dentistry, but the amount of research applied to denture base resin is very small-there are only three papers, by KANEKO et al. [4, 5], IBUSUKI et al. [10], and POWERS and J.M. [11, 12] and most of these used the Munsell color comparison method. Therefore, the authors did experiments using measuring equipment which can produce objective results, and obtained the following conclusions :
1. The lightness of the resin decreased with increasing thickness.
2. The color saturation of the resin was greatest when the thickness was 1.8 mm.
3. A tendency for the hue to change from reddish-yellow to red and to reddish-purple was observed with increasing thickness.
4. For the lightness of the resin, no influence was observed of the change in Shades No. 1 to No. 4. However, lightness was influenced by differences in the thickness of Shades No. 1 to No. 4, and also by differences in the shade as well as the thickness of Shades No. 6 to No. 9.

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Orthopantomography for dental X-ray examinations is a kind of tomography which has a special characteristic different from any other tomographic methods. A comparative study of radiographic images formed by ordinary tomographic equipment with the attachment of slits devised by the authors and images produced by orthopantomography is presented.
As a result of comparing image-formation in orthopantomography with that of ordinary tomography using the same objects, (1) hardly any blur was observed inside the contours of the orthopantomographic image, (2) a very slight blurring effect of orthopantomography was observed on the slit side, (3) the slit played an important role in limiting the tomographic effect, and (4) consequently, orthopantomography may be considered as a very special type of tomography in the presence of slits.

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The purpose of this study was to evaluate, in replanted rat upper first molars, through histological analysis, the effect of splinting upon postoperative events related to the tooth and its supporting structures.
Seventy-two male albino rats were used in order to analyze the effect of splinting upon periodontal healing after molar replantation. The animals were sacrificed after 2, 5, 10, 20, 30 and 60 days. The authors concluded that splinting of the replanted teeth :
a) Contributes to limiting the apical migration of the muscou membrane epithelium and favors epithelial reattachment.
b) Contributes to reducing the degree of external root resorption and the degree of resorption of the alveolar bone wall.
c) Creates better conditions for healing of the periodontal ligament and favors the revascularization of the pulp.

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