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A comparative study of the denture and facial skeletal pattern of white identical twins
ABSTRACTS
148
AND
REVIEWS
.Am. J. Orthodontics February,
1958
skulls were studied grossly by means of a processed acrylic articular space model, and (3) there were forty-eight serially sectioned articular space models of twelve skulls. Twenty-four (one set, a left and right, for each skull) were sectioned sagittally to the long axis of the condylar head; the other set for the twelve skulls were sectioned transversely, parallel to the long axis of the condylar head. The serial sections were all mounted on a hard cardboard sheet and studied by tracing enlargements projected with an opaque projector. Important to the method of study was the division of the curved plants into various surfaces and correlating the planar similarity of the parts, rather than of the whole. The results of this three-dimensional study demonstrated a significant parallelism of the curved planes formed by the articular surfaces in certain areas. The most significant dimensional correlation was found on the superior surface of the sagittal sections and on the medial and middle surfaces of the t,ransverse sections. This indicates the validity of assuming that there is a functional adaptation of these articular components. Functional adaptation formerly had been denied on the basis of heredity, postural evolution, and extensive t,wo-plane radiographic studies, wherein mechanical projection error and interpretive error were not fully evaluated. The sectioned results were confirmed, in part, in the gross studies of both the articular space models and gross examination of the skulls.
A Comparative Study of the Denture and Facial Skeletal Pattern of White Identical Twins: By Joseph J. Bonello, B.S.. D.D.S.. KS., IJnivePsity 01 Pittsburgh,
Pittsburgh,
Pennsylvania.
The purpose of this study is to determine the significance of genetic and environmental influences affecting the denture and facial skeletal pattern as expressed by a chronological, comparative study of white identical twins. Thirtynine pairs of t,wins, ranging in ages from 6 to 14 years and almost equally divided as to sex, were used for the author’s master’s thesis at the University of Pittsburgh in 1955. As a recipient of the Cordelia Scaife May Fellowship, the author was able to repcat this research project in 1956 and thirty-two of the original thirty-nine pairs of twins wclc the subject participants. Verification of the twin type was established by the physician attending at birth. The procrdure on each twin in 1955 and in 1956 was to obtain a lateral cephalogram, study models, full-view photographs (front and side), prenatal history, familial hlstorg, and general medical data. A Downs analysis was made from each cephalogram and the study models afforded important measurcments in determining similarities or dissimilarities betwccln twin and co-twin relative to the dcntition. Study model mtlasurements for the maxilla and the mandible included: a”rch width-first molar to first molar, canine to canineand arch length-right first molar t,o midline, left first molar to midline, and canine to canine. In addition, the t,ype and severity of malocclusion (Angle’s classification) were independently judged by three investigators from the study models. The findings of the research done in I955 indicated that the order of birth did not seem to have any significant influence on the various angular measurements in Downs’s system. Also, there appeared to be no significant difference between the first- and secondborn twin of each pair regarding the type and severity of malocclusion, which suggests that occlusion or malocclusion is influenced more by genetic factors than by environmental variables. Correlations between the twin and co-twin of each pair in the ten measurements of
Volume 44 Number 2
ABSTRACTS
AND
REVIEWS
149
Downs’s system and the classification of type malocclusion indicated that measurements of the denture to the facial skeletal pattern (measurements 6 to 10) were less susceptible to environmental influences than were the measurements of the facial skeletal pattern (measurements 1 to 5), with the exception of measurement No. 4.
Analysis of the Electromyogram in Masticating Chewing Gums of Varying Toughness: By Samuel Pruzansky, D.D.S., Martin Pesek,
Quantitative
D.D.S., and L. F. Osborn, M.A., Department of Physical Medicine and Rehabilitation and the Cleft Palate Center of the University of Illinois, Chicago, Illinois.
In 1952 Pruzansky described qualitative differences in the electromyographic patterns of chewing and characterized certain extremes as choppers and grinders. The suggestion was made that the electromyogram might be used as an additional measure of mast,icatory efficiency. The addition of an electronic integrator to the basic electromyographic equipment made it possible, for the first time, to measure the electrical output of a muscle during a given time interval. The specific aims of these investigations were: (1) to analyze the muscular effort required of the masseter muscle in chewing test substances of known and varying degrees of toughness, (2) to quantify the changing requirements in energy input with ascendin g and descending ranges of toughness of test substances, and (3) to measure the differences in energy input in different persons masticating similar test substances and to correlate such differences with variables in the natural or artificial dentition. In our investigations we have employed chewing gums of known and varying degrees of toughness as our test substances, in preference to the use of peanuts or hard crusts of bread. The reason for this is that chewing gum, once softened within the mouth, has the advantage of maintaining a relatively constant resistance to masticatory stress. Chewing food substances, such as peanuts, produces a regular and progressive decay of muscle effort as the bolus is triturated and reduced in size. The energy data presented by the integrating circuit are calibrated by comparing the number of indications of the integrator in a given time frame to a known voltage input. In persons with normal occlusions, the electrical activity of the masseter on the working side is always greater than that on the balancing side. The ratio of energy input between working and balancing sides decreases with increased load,
148
AND
REVIEWS
.Am. J. Orthodontics February,
1958
skulls were studied grossly by means of a processed acrylic articular space model, and (3) there were forty-eight serially sectioned articular space models of twelve skulls. Twenty-four (one set, a left and right, for each skull) were sectioned sagittally to the long axis of the condylar head; the other set for the twelve skulls were sectioned transversely, parallel to the long axis of the condylar head. The serial sections were all mounted on a hard cardboard sheet and studied by tracing enlargements projected with an opaque projector. Important to the method of study was the division of the curved plants into various surfaces and correlating the planar similarity of the parts, rather than of the whole. The results of this three-dimensional study demonstrated a significant parallelism of the curved planes formed by the articular surfaces in certain areas. The most significant dimensional correlation was found on the superior surface of the sagittal sections and on the medial and middle surfaces of the t,ransverse sections. This indicates the validity of assuming that there is a functional adaptation of these articular components. Functional adaptation formerly had been denied on the basis of heredity, postural evolution, and extensive t,wo-plane radiographic studies, wherein mechanical projection error and interpretive error were not fully evaluated. The sectioned results were confirmed, in part, in the gross studies of both the articular space models and gross examination of the skulls.
A Comparative Study of the Denture and Facial Skeletal Pattern of White Identical Twins: By Joseph J. Bonello, B.S.. D.D.S.. KS., IJnivePsity 01 Pittsburgh,
Pittsburgh,
Pennsylvania.
The purpose of this study is to determine the significance of genetic and environmental influences affecting the denture and facial skeletal pattern as expressed by a chronological, comparative study of white identical twins. Thirtynine pairs of t,wins, ranging in ages from 6 to 14 years and almost equally divided as to sex, were used for the author’s master’s thesis at the University of Pittsburgh in 1955. As a recipient of the Cordelia Scaife May Fellowship, the author was able to repcat this research project in 1956 and thirty-two of the original thirty-nine pairs of twins wclc the subject participants. Verification of the twin type was established by the physician attending at birth. The procrdure on each twin in 1955 and in 1956 was to obtain a lateral cephalogram, study models, full-view photographs (front and side), prenatal history, familial hlstorg, and general medical data. A Downs analysis was made from each cephalogram and the study models afforded important measurcments in determining similarities or dissimilarities betwccln twin and co-twin relative to the dcntition. Study model mtlasurements for the maxilla and the mandible included: a”rch width-first molar to first molar, canine to canineand arch length-right first molar t,o midline, left first molar to midline, and canine to canine. In addition, the t,ype and severity of malocclusion (Angle’s classification) were independently judged by three investigators from the study models. The findings of the research done in I955 indicated that the order of birth did not seem to have any significant influence on the various angular measurements in Downs’s system. Also, there appeared to be no significant difference between the first- and secondborn twin of each pair regarding the type and severity of malocclusion, which suggests that occlusion or malocclusion is influenced more by genetic factors than by environmental variables. Correlations between the twin and co-twin of each pair in the ten measurements of
Volume 44 Number 2
ABSTRACTS
AND
REVIEWS
149
Downs’s system and the classification of type malocclusion indicated that measurements of the denture to the facial skeletal pattern (measurements 6 to 10) were less susceptible to environmental influences than were the measurements of the facial skeletal pattern (measurements 1 to 5), with the exception of measurement No. 4.
Analysis of the Electromyogram in Masticating Chewing Gums of Varying Toughness: By Samuel Pruzansky, D.D.S., Martin Pesek,
Quantitative
D.D.S., and L. F. Osborn, M.A., Department of Physical Medicine and Rehabilitation and the Cleft Palate Center of the University of Illinois, Chicago, Illinois.
In 1952 Pruzansky described qualitative differences in the electromyographic patterns of chewing and characterized certain extremes as choppers and grinders. The suggestion was made that the electromyogram might be used as an additional measure of mast,icatory efficiency. The addition of an electronic integrator to the basic electromyographic equipment made it possible, for the first time, to measure the electrical output of a muscle during a given time interval. The specific aims of these investigations were: (1) to analyze the muscular effort required of the masseter muscle in chewing test substances of known and varying degrees of toughness, (2) to quantify the changing requirements in energy input with ascendin g and descending ranges of toughness of test substances, and (3) to measure the differences in energy input in different persons masticating similar test substances and to correlate such differences with variables in the natural or artificial dentition. In our investigations we have employed chewing gums of known and varying degrees of toughness as our test substances, in preference to the use of peanuts or hard crusts of bread. The reason for this is that chewing gum, once softened within the mouth, has the advantage of maintaining a relatively constant resistance to masticatory stress. Chewing food substances, such as peanuts, produces a regular and progressive decay of muscle effort as the bolus is triturated and reduced in size. The energy data presented by the integrating circuit are calibrated by comparing the number of indications of the integrator in a given time frame to a known voltage input. In persons with normal occlusions, the electrical activity of the masseter on the working side is always greater than that on the balancing side. The ratio of energy input between working and balancing sides decreases with increased load,