Linden F. Edwards

The edentulous mandible

Abstract 1. The objectives of this article are to describe the edentulous mandible in greater detail than is usually done in standard textbooks of human anatomy and to correlate the anatomic features of the edentulous mandible with the soft parts related to it. 2. Questions are raised concerning the usage of certain anatomic terms in the light of existing structural conditions. 3. The most characteristic and well-known feature of the edentulous mandible, from which the permanent teeth have been missing for a period of time, is the absence of a well-defined alveolar process resulting from resorption due to disuse atrophy. 4. As a result of the resorption of the alveolar process, the vertical height of the bone in the region of the body is greatly diminished; the mylohyoid line, genial tubercles, and incisive fossae with their attached muscles lie near or upon the crest of the residual ridge, as do the mental foramen and its contained vessels and nerve; some structures, such as the buccal shelf and buccinator crest, lose their identity; while others, such as the chin and lingual tuberosity, seem to be exaggerated. 5. The coronoid and condyloid processes exhibit certain characteristic features: the former being shorter than the latter and both bent backward; the anteroposterior diameter of the condylar head is diminished; its articular surface is confined to its superior aspect and the lateral tubercle is quite pronounced. 6. Evidence is presented to indicate that the rami and body of the edentulous mandible may share with the alveolar process in resorption.

Anatomy of the mouth and related structures

Abstract Within the oral cavity, the function of eating is initiated and the function of speech is finalized. A third function, breathing, contributes to both of these other functions by (1) inhalation of air to supply the medium for oxidizing the food and (2) exhalation of air to supply the medium for the production of speech. Since a functional consideration of breathing is essential for an understanding of the physiology of speech, the function of breathing will be considered in the next article of this series.

Does Resection of the Nerves Supplying the Mandible Affect Tooth Development

A review of the literature reveals that relatively little attention had been paid to the problem concerning the effect either of traumatic or experimental resection of the nerves supplying the maxilla or mandible on the development or eruption of teeth. Vieyra (4) reported that unilateral extirpation of the superior cervical sympathetic ganglion in dogs operated 7-12 days after birth resulted in retardation in development of the mandibular teeth on the operated side. This author mentions, without citing any references, that Angelucci observed the same effect in dogs, that Nemzoglau on the other hand noted an acceleration in the development of the teeth whereas Hertel observed no alteration in the rate of growth of the teeth in young rabbits. King (3) found (a) that unilateral resection of the inferior alveolar (dental) nerve in young dogs resulted in a slight acceleration in eruption of the permanent teeth on the operated side; (b) that a similar operation on rabbits resulted in acceleration of growth of the permanently growing incisor tooth on the operated side, at least during the first 8-21 days following the operation after which time a slight retardation in rate sometimes occurred and (c) that unilateral extirpation of the superior cervical ganglion in rabbits likewise produced an increased rate of growth of the lower incisor tooth on the operated side. The objective in the present study was to determine whether or not unilateral resection of the nerves supplying the mandible of the kitten affects the development of the permanent tooth-germs. Three series of operations were performed using 2 animals of the same age in each series. In the first series the superior cervical sympathetic

Anatomy of the mouth and related structures: Part II. Musculature of expression

Abstract The complex interplay of bone and musculature becomes apparent in even a limited analysis of facial expression. The complexity continues in any attempt to analyze further functions of speech, respiration, mastication, and deglutition, all of which are processes occurring in the arena of the pyramid previously delineated. Analyses of functions of facial expression and speech and the study of dissections of the muscles of facial expression indicate that certain of these muscles, acting as combined units and attached to fixed and movable bone, may play a role in mandibular movements associated with the functions of speech and facial expression. These functions and their interassociations will be considered in the next article of this series.

Effect of Artificially Induced Hyperpyrexia on Tooth Structure of the Rabbit

The increasing therapeutic importance of artificially induced fever raises the question of its effect on developing tooth structure. Damage to the enamel by infections accompanied by high fever during the period of tooth formation has been recognized clinically for many years. It is evidenced as a hypoplastic condition with superficial pits and grooves, often markedly disfiguring the anterior teeth. Detrimental effects in the dentin would be an internal dystrophy and would escape clinical notice but might well be expected under conditions which would affect the enamel. Normal dentin is a homogeneously calcified tissue produced by the dental pulp. It is laid down around the periphery of the pulp in periodic increments as an organic matrix which is subsequently calcified to a bone-like consistency. Unlike bone, dentin once formed is not subject to further physiologic change to any marked degree, and hence it affords a permanent record of any variations in the calcification process. The dentin of the continuously growing teeth of the rabbit, therefore, affords a suitable medium for the recording of any effect which might be caused by artificially induced hyperpyrexia. In the same series of rabbits used for observations on other tissues by the Departments of Medicine and Pathology and reported elsewhere, 1 2 3 histologic studies were made on thin ground sections cut longitudinally through the incisor teeth. Schour and Hoffman, 4 reporting on dentin deposition in growing mammalian teeth, state that it is laid down at the approximate rate of 16 micra in 24 hours. Their work included, among other animals, a series of rabbits. Thus, any periodic interference with calcification would be characterized by the presence in the dentin of alternate layers of normal and abnormal tissue, the latter coinciding with the periods of disturbance.

Does the Maxilla Lack a Periosteal Membrane

The periosteum has been a point of contention for almost 200 years, dating from the controversy between Duhamel and Haller (1) concerning its osteogenic or bone-forming power. It is not our purpose to enter into this age old conflict but rather to attempt to clarify the conception which occasionally appears in the literature to the effect that the maxilla lacks, or is poorly provided with, a periosteal covering. Thus, for example, Foman (2) makes the statement that

Anatomy of the mouth and related structures: Part I. The face

Abstract Thus far, external signs and symptoms as revealed in facial features and contours have been considered. These diagnostic aids are readily visible to the dentist as he first sees his patient. But as the patient begins to relax and speak, the dentist has an opportunity to observe the fleeting facial movements and mannerisms characteristic of that individual. He is watching what has been termed the fourth dimension, the vitality factor, or anatomy in action. This will be considered in subsequent articles of this series.

The Extra-Osseous Innervation of the Gingivae

A LTHOUGH the literature, bearing upon the innervation of a tooth and its periodontium, as demonstrated microscopically, is rather voluminous, information concerning the total number of nerves that are involved in innervating all of the mandibular and maxillary teeth and their supporting structures, especially the gingivae, is scant. Several investigators, notably Stewart and his co-workers,18 39-41 have demonstrated by means of histologic preparations that the supporting structures of a tooth are innervated by intra-osseous and extra-osseous nerves. The term intra-osseous refers to the alveolar or dental nerves which course within the mandible and maxillae. According to these investigators, fibers of these nerves supply not only the dental pulp but also the periodontal membrane, the surrounding alveolar process, and the gingiva. By the term extra-osseous nerves is meant those nerves which are situated external to the mandible and maxillae on their buccolabial and palatolingual aspects and from which, according to these investigators, fibers can be traced microscopically to the gingiva, alveolar process, and periodontal membrane. Thus, according to these authors, and, as shown in an illustration in one of their papers,18 the gingiva adjacent to any tooth is innervated by nerve fibers from 3 different sources, namely, from the intra-osseous or alveolar nerve, from an extra-osseous nerve situated on the buccolabial aspect of the jaw, and from an extra-osseous nerve located on the palatal or lingual aspect. Inasmuch as these authors were concerned primarily with the distribution of the nerve fibers from these 3 sources as observed microscopically, their studies did not include an identification of the extra-osseous nerves involved. The. objective of the present paper is to report the results of a study of the extra-osseous nerves which are involved in innervating the gingivae as determined by careful, tedious, gross dissection.