The diameter sizes of enamel crevices in cat, man, ape and cattle permanent teethwere measured by the use of an ocular micrometer attached to the optical microscope. The crevice diameter sizes of these four kinds of mammals were found to be in the range of 0.74-1.41 microns, closely resembling one another. On the other hand, thediameter sizes of enamel lamellae in them were in the range of 5.0-85.6 microns and the difference between these two sets of measurement was quite large. Based on the vast difference between the two, the author is inclined to the view that enamel lamellae are an entirely different substance from cracks in the enamel which were invaded and filled by cells from the enamel organ, as has been proposed by GOTTLIEB and long believed by the majority of dental histologists.

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In the course of our consecutive observation of 304 grade school children by means of periodic radiography, attention was drawn to a case of impacted 3_??_ in one of the examined. Therefore, it was subjected to chronological examinations extending for a period of 8 years.
The impacted tooth gradually migrated from its cusp through the body of the mandible and the root region of anterior teeth to a spot beneath the mental foramen on the opposite side, having gone through the symphysis. At present, its apex is found to lie beneath the apex of 1_??_ and it is tilted lingually in the body of the mandible. However, there has been noted no particular influence such as oppression of the mandibular nerve owing to the transmigration of the said impacted tooth.

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In 1962 the authors published their study as “303 Clinical Cases of the Gingival Regeneration in Periodontal Diseases” (The Journal of Nihon University School of Dentistry, Vol. 5, No. 2).
The feature of our technic described in that study is to excise in a fairly wide area the region periodontally afflicted and expose an alveolar bone about 3-4mm by removing the alveolar mucosa and apply a surgical pack directly on the exposed alveolar bone after having cleaned the deposit and imperfect gingiva and, if necessary, osteoplasty is administered. In that study, we stated to the effect that the advantage of this technic consists in the redction of operational time since it does not require suturing as in the case of flap operation and the good postoperational growth of interdental papilla. As distinct from any previous gingival restoraion or curettage technic, a cure under this technic can be effected by means of entirely new gingiva, not from the old native gingiva. A brief summary of the technic together with illustrations appeared in the Dental Abstracts, American Dental Association (Vol.9, No.2, pp. 111-112, 1962). Since this study was published, we have further aplied the same technic to more patients amounting to over 1000 at the time of writing.
Based o these numerous clinical cases, we here report on their curative process by means of roentgenographical findings and magnified photographs to illustrate the manner of curative process in the light of histology.

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