The bony nasopharynx; a roentgen-craniometric study

-Volume Number

Reviews and abstracts

52 4

307

Definitions of the various malocclusions and of the need for treatment used in the registration procedure have been worked out on the basis of three pilot studies, each on 100 children, and modified in the light of experience derived from these studies. In order to evaluate the systematic errors of registration, the examinations in one of these studies were performed by three dentists. In another study the examinations were performed twice by the same dentist to determine the random error of registration. The occlusion is recorded. Incisal occlusion is judged from the most prominent central incisor. Sagittal molar occlusion is evaluated with respect to the mesial contact points of the upper and lower first permanent molars. Before full eruption of the first permanent molars, the molar occlusion is determined from the distal surfaces of the second deciduous molars. The position of the third molars is disregarded in the registration of vertical and transversal occlusion. An account is given of a method for epidemiological investigation of the prevalence of malocclusions. The method consists of a systematic registration of carefully defined individual symptoms. The registration of some of the symptoms is facilitated by using a specially designed instrument. The need for treatment is also investigated, but this registration is subjective. The study has been designed with a view to electronic analysis of the data. The

Bony

Nasopharynx;

By Olav Bergland.

a Roentgen-Craniometric

Acta odont. scandinav.

Study 21: Xupp. 35, 1963.

This article describes a study of the skeletal limitations of the nasopharynx as a part of the cranium. The aim of the study was to investigate (I) variations in the shape and size of this part of the skull and (2) its covariations with cranial features which may influence the morphology of this region, primarily the sagittal shape of the cranial base and the angles of the upper face. The investigation comprised : (1) intragroup variations; (2) population differences; (3) age changes (after about 6 years of age) ; (4) sex differences; and (5) correlations. Anatomically, the bony nasopharynx is bordered by the following skeletal elements : (1) anteriorly, the structures constituting the choanal openings (the medial plates of the pterygoid processes laterally and the dorsal border of the vomer medially) ; (2) posteriorly, the pharyngeal surface of the body of the sphenoid bone and of the basilar part of the occipital bone; (3) caudally, by the posterior border of the horizontal part of the palatine bone anteriorly and by the anterior margin of the foramen magnum posteriorly. Geometrically, the bony nasopharynx in the median sagittal plane is shaped like a gable. The anterior part of the gable, corresponding to the choanal structures, is formed by a line joining the landmarks staphylion (the posterior nasal spine,) and hormion (the vomer’s dorso-rostra1 point of contact with the body of the sphenoid bone). In man this line is approximately parallel to the main direction of the pterygoid processes (the choanal plane). The posterior part of the gable, corresponding to the caudal surface of the

body of the sphcnoid boric and the IJ;lsil;~~* Icrrt of’ 1111,owipit;~l I)olltlj is ~OI~II~(VI by a line joining hormion and basion (the aittcrior nlargin 01‘ t Ire I’otWric~lr magnum). The hormion-basion region mill llcrcilft(~i* 1~ rrI’crret1 to as the pharyngeal clivus. The bony ~laS~J~hw~llx is candal I>- lirnitctl 1)~ a lint joining the points staphylion and basion. The widening of the bony nasopharynx in an iIilt~~l~Op~St~‘~iO~ tlircction. which could be expected because of the increase in length of the \~omcr’s dorsa 1 border and of the clivus, does not occur. The reason is that the available spacc~ is taken up by posterior appositional growth of the choanal structure. The dorsal border of thtt romer is erected, extending the floor of the nasal cavity further backward. Great individual variations in the nasopharyngeal roof angle in adults, a weak correlation between shape and size of the nasopharynx and the upper fact, and a lack of association between the maxillary and the nasophar~ngeal parts of the facial depth indicate that the nasophrynx is an essential region for the adjustment between the relatively early developing neurocranium and the relatively lat,e developing visceral cranium. Fluoride By

Protection Reid&r

of Bones

P. Sognnaes.

and

Teeth

Science.

150:

989-993,

Not:.

19, 1.965.

There is current evidence of a new interest in the extent to which tissue tolerates fluoride and in the potential benefits of ingested fluoride in the management of various general illnesses, notably metabolic bone diseases. The fluoride dosages tolerated in tissue culture (5 to 10 parts of fluoride ion per million) and used in recent medical applications (20 to 100 mg. of fluoride ion per day) suggest that ingestion of water containing fluoride at a concentration of 1 part per million (0.5 to 1 mg. of fluoride ion per day), as recommended for the prevention of dental caries, provides a higher margin of systemic safety than is generally believed. The weight of evidence now indicates that cellular reproductivity goes on in the presence of an amount of fluoride greater than the amount which can bc brought into the body’s circulating Cssue fluids through oral ingestion. One of the remarkable aspects of fluoride ingestion and metabolism is the curious fact that it is almost impossible to raise markedly the fluoride level in blood plasma in logical relation to oral ingestion of fluoride at extremely high concentration. It appears that there is no marked increase in the fluoride levels in plasma, even at intakes twice the 1 part per million recommended for the prevention of dental caries. The body has an effective means of maintaining a constant concentration of fluoride in body fluids, even when t,here are large vuriations in fluoride intake. This homeostasis is effected partly by the kidney, which operates as an efficient organ of fluoride excretion, and partly by the skeleton. The mean fluoride content of the plasma of persons whose drinking water contains more than twice the amount of fluoride recommended for the prevention of caries has been found to lie below 0.20 part per million; even in persons whose