The newly revised American Dental Association Specification No. 11 for Dental Hydrocolloidal Impression Material-Agar Type did not exclude the agar impression materials on the current List of Certified Dental Materials as established by the American Dental Association. Therefore, these materials comply with both the old and the revised specifications which define materials having a wide range of flexibility. The authors recommend that serious consideration be given to the use of agar impression materials, especially in indirect methods.
The formulation of a specification for dental alginate impression materials, which will characterize them adequately, is described and much of the experimental data obtained during the development is presented.
Attention not only on the part of medical profession, but also on the part of general public has been recently much stirred in connection with the congenital abnormality, particularly as represented by the so-called thalidomide baby. KOBAYAKAWA  and KURIHARA , one of the present authors, gave their report on a complete case of amelus in limbs of a baby attributable to the prolonged use of thalidomide hypnotic by its mother, the first attempt undertaken in the light of dental investigation. Although there is no agreement among the scholars as to what is meant by the congenital abnormality, we may follow the definition of Schwalb which states to the effect that an abnormality is applied to a case taking place in the developmental process which falls outside the species variation. In a similar vein, World Health Organization (WHO) defines anatomical developmental anomalies to be 1) already existing at the time of birth or to be confirmed by autopsy, and 2) visible macroscopically and not include microscopic anomalies. As against the anatomical developmental anomalies, congenital. anomalies are to be held such as are included in those even prior to an actual birth and any other disturbances of functional, biochemical or metabolic nature, both macroscopic and microscopic. In the dental field, the teeth and jaws are conventionally subject to twofold classification of abnormality and teratism. With the abnormalities of teeth are associated such features as irregular number of teeth, irregular dental morphology, irregular dental position, various malocclusions, irregular dental substances, etc. With particular reference to pedodontics, a great majority of abnormalities are due to influence of a mother in pregnancy, time of birth, diseases in the neonatal period and systemic diseases of an infant, all of which have important bearings on its deciduous teeth formation and subsequent change for succedaneous teeth. The present report is concerned with a clinical case of pedodontic abnormality which is of much interest as one in which the fingers are associated with the oral cavity.
Today the common acceptation of the term congenital tooth is used to mean the tooth which is already erupted in the oral cavity of a new suckling on the occasion of its birth. According to the literature related to congenital teeth, most cases occur in the locality of lower incisors. But even today there is no research report available concerning its electron microscopy. 4 congenital teeth from 2 sucklings were recently sent to the author by the courtesy of Dr. O. Okamoto, a practicing dentist at Yonago City, Main Island, Japan. Therefore, he was enabled to examine electron microscopically the hard tissues of the congenital teeth. As a consequence, some interesting findings have come to light respectively in the enamel, dentin and cementum. Concerning these congenital teeth, Dr. Okamoto and his associates had already published in detail their macroscopic aspects in a Japanese dental journal “Shikai-tembo” (Dental Outlook), Vol. 23, No. 4, in 1964. Here reference is made to macroscopic photographs and measurement rates of the congenital teeth from their paper.