Helmut A. Zander

Occlusal interferences and mastication : An electromyographic study

T I n spite of the many recent advances toward a better understanding of the neurologic aspects of mastication, the function of tooth contacts as a part of the neuromuscular mechanisms of chewing is still a rather controversial question. Some investigators attribute no functional importance to tooth contacts during chewing.’ However, others see a justification for the equilibration of occlusal disharmonies in the fact that tooth contacts occur during mastication.” The neurophysiologic basis by which occlusal disharmonies might act in the creation of occlusal trauma is connected with the possible role of tooth contacts and tooth sliding during functional or dysfunctional movements. Karolyi” recognized early the important role of bruxism in the etiology of periodontal disease and also the interrelationship between occlusal disharmonies and bruxism itself. Thielemann, 4 in discussing the etiology of periodontal disease, clearly distinguishes between chewing and “empty” grinding movernents. Drum” first stressed, in the European literature, the difference between the self-protecting functional movements during mastication and the auto-destructive ‘~I)arafurlctionst“ like bruxism, which are performed on a subconscious level. This view was also cxpressed earlier in the American literature by Shanahan’ and Jankelson.’ Electromyclgraphic (EMG) studies by Ramfjord, fi in an evaluation of the effect of occlusal interferences on bruxism and the EMG activity of the chewing muscles, showed that the masticatory movements were unreliable as an indicator of occlusal interferences for patients who manifested marked EMG changes during “empty” man-

Tooth contact patterns in mastication

T HE PHYSIOLOGY of mastication and its underlying neuromuscular mechanisms .are incompletely understood. Statements about the role of occlusion and tooth contact in these mechanisms have been made in the literature but only a few are based upon experimental evidence. The clinical experience of successful treatment of temporomandibular joint and muscle disturbances, as well as bruxisrn,lm4 by occlusal adjustment (equilibration) and splints is an indication that occlusion has a significant role in the neuromuscular mechanisms. Under experimental conditions, occlusal interferences have been shown to influence electromyographic patterns.3 These clinical and experimental observations are indirect evidence that occlusal contacts play an important role in the reflex systems of the masticatory apparatus. Controversy has surrounded the occurrence of occlusal tooth contacts per se during functional movements and there is no published evidence on the precise jaw relationship during such contacts, or on their duration. Early attempts to measure occlusal tooth contact were the investigation of Hesse5 who studied the masticatory movements of the mandible. His report was concerned with empty movements and his paper, given in Paris, described functional movements.6 He used the space of a missing tooth to contain a lead pencil with a recording layer on the opposing tooth. His experiments showed the occurrence of occlusal tooth contacts during chewing in maximum intercuspation as well as during lateral excursions. The recordings of Jankelson and othersi were the first which measured directly the occurrence of tooth contact. Their attempts to detect tooth contact by means of cinefluorography were not successful. Subsequently, they developed a method which applied an electrical potential between two antagonistic full crowns. Upon contact, the circuit was closed and the potential difference was recorded on an oscillograph. Based upon this study they state: “. . . it cannot be stressed too forcefully that it was only during the act of deglutition that functional contact of opposing teeth was demonstrated.” Anderson and Pictons recorded tooth

Root surface resorption of periodontally diseased teeth

Abstract Investigation of resorption areas on the roots of three groups of teeth—118 healthy, 81 periodontally diseased, and 100 teeth from India—showed three times more root surface resorption on periodontally diseased teeth and five times more on teeth from India than on healthy teeth. Other types of cementum changes or loss were also noted.

Kinetics of Deoxyribonucleic Acid Synthesis within the Inner Enamel Epithelium

SYNOPSIS IN INTERLINGUA LE CINETICA DEL SYNTHESE DE ACIDO DISOXYRIBONUCLEIC INTRA LE EPITHELIO ADAMANTIN INTERIOR.— Le differentiation del epithelio adamantin interior de dentes molar de rattos esseva examinate radioautographicamente post le injection de thymidina tritiate. Esseva analysate le procentage de marcate cellulas in le varie morphologicamente definibile areas, le augmento del numero de marcate cellulas post le prime division, le relation inter le numero de cellulas marcate e le numero de non-marcate mitoses, e le duration del stadio S. Un definite correlation pote esser establite inter morphologicamente identificabile stadios in le differentiation de epithelio adamantin interior e le procentage de marcate cellulas in omne gruppo individual. Tamen, un gradation intra omne gruppo suggere que-ben que omne le cellulas intra un area particular ha le mesme characteristicas morphologic—stadios de differentiation vermente existe. Le capacitate de experientiar additional division cellular declinava con le differentiation. Durante le processo differentiatori del epithelio adamantin interior, le tempore requirite pro le synthese de acido disoxyribonucleic pare accrescer.

Dynamics of Dental Epithelium During Tooth Eruption

The dental epithelium of developing rat molars was labeled with tritiated thymidine administered by gastric intubation. Labeled ameloblasts were lost from all enamel surfaces at approximately the same time by desquamation into the gingival sulcus. The other cells of the dental epithelium proliferated to form the renewing epithelial cuff.

Contact Patterns Using Miniature Radio Transmitters

oneor two-tooth partial denture. A squegging oscillator circuit was used. The components, 7 in number, were subminiature, and the finished unit broadcasted in the marine band (2-4 megacycles). The radio was provided with two gold bars, insulated from each other and connected in the circuit in such a way that only when they were bridged by a conductor was a radio signal broadcasted (Fig. 1). The conductor, a gold pin, was cemented in a hole cut in the tooth cusp opposing the gold bars of the transmitter. It was inserted in such a position that when the teeth were in contact in the

Experimental Ischemia in Monkeys: I. Effect of Ischemia on Gingival Epithelium

Unilateral ischemia was produced in periodontal tissues of squirrel monkeys by introduction of carbonized microspheres into the external carotid circulation. The palate and gingival tissues appeared blanched unilaterally. Histopathology ranged from moderate acanthosis to frank ulceration. Deoxyribonucleic (DNA) duplication was depressed during the period of ischemia and hyperemia, and then increased.

Cementum of Periodontally Diseased Teeth from India

In a study of the thickness of cementum in relationship to age, Hiirzeler and Zander1 found that at all ages the cementum thickness in teeth from the United States was less in teeth with diseased periodontium* than in teeth with healthy periodontium.t Therefore, it seemed of interest to determine whether this trend could also be found in periodontally diseased teeth from India. Unfortunately, periodontal disease seems to be so universal in India that we were unable to find a control group of Indian teeth having no periodontal disease. TABLE 1

Experimental Ischemia in Monkeys: III. Histochemical Analysis of Gingival Epithelium

Changes in oxidative enzyme and acid phosphatase activity, glycogen, ribonucleic acid (RNA), and lipid were demonstrated by histochemical technics in gingival epithelium of squirrel monkeys after experimental arteriolar occlusion. After 24 hours, glycogen and lipid content increased, and all enzyme activity, except lactic dehydrogenase, was depressed. By 72 hours, enzyme activity associated with the hexose monophosphate shunt was elevated.

Clinical Science Physical and Chemical Effects of Toothpastes on Dental Enamel

The effects on surface enamel of an experimental toothpaste containing Sr-EDTA, sodium ricinoleate, and fluoride were compared with those of a commercially available fluoride toothpaste. Knoop indentations, before and after treatment with control and experimental toothpastes, showed no significant changes. Both toothpastes rendered the enamel surface less soluble after treatment.