Genetic considerations orthodontics
in clinical
G
enetic influence on the pathologic, structural, and morphologic maldevelopment of the dentofacial area is no longer of academic interest only to the practicing orthodontist. However, the clinical evaluation of genetic facies has to date been of extremely limited scope, and genetic influence as an aid in recognition, treatment, and patient counseling has received little or no attention. Parallel with the accelerated knowledge on general medical genetics has been the marked upsurge of research and publication of articles on the expression of genetics in facial, oral, and dental diseases and developmental aberrations. A recently published volume on Oral Facial Genetics* covers the various aspects of genetics in relation to dentofacial maldevelopment and malocclusion and presents a full account of oral and pathologic conditions. The seventeen outstanding research contributors to this volume are widely recognized for their knowledge of the respective subjects they present. This book is a landmark in dental science, of use to students and practitioners and as a source of reference to research workers. If he is familiar with this text, the orthodontist who is interested in doing more than move malposed teeth will find it unnecessary, when faced with an uncommon oral pathologic condition, to refer his patient to a general medical pathologist whose knowledge of the subject may not be more than cursory. Robert J. Gorlin of the School of Dentistry of the University of Minnesota, who discusses heritable mucocutaneous disorders, and M. M. Cohen, Jr. of the University of Washington, Seattle, who writes on dysmorphic syndromes with craniofacial manifestations, have broken new ground with the width and depth of their contributions. It is no longer doubted that orthodontists can successfully treat malocclusions and dentofacial deviations of genetic origin. They constantly treat such conditions and influence the vector if not also the amount of facial growth. Ray E. Stewart, a medical geneticist, and M. A. Spence, Ph.D., a psychiatrist, both of the University of California at Los Angeles, list malocclusion as the most common hereditary deviation in dentistry, followed by periodontal disease and dental caries. They point out that malocclusion can result from a mutation at a single gene locus. While it is not always clear to what extent phenotypic characters are of genetic or of environmental origin, we know that maldevelopment may be multifactorial and is in the nature of a continuum. It is not rare to find the same classification of malocclusion in :‘Stewart, R. E.. and Prescott, Mosby Company.
G. H. (editors):
Oral
Facial
Genetics,
St. Louis,
1978.
The C.
V.
467
468
Ediror-irrl
Am. J. Orthod. October 1978
parents and siblings, extending even to irregularity of a corresponding single tooth or a few teeth as a family trait. However, remarkable differences can be found also in parents and siblings and even in monozygous twins. The reason for these deviations is linked to muscular, functional, and neurogenic differences. While these occurrences usually are attributed to postnatal environmental causes, mutational heterogenicity exists in practically all human genes. Genetic traits in the craniofacial region are known to undergo change. Children who strongly resemble a parent may no longer show such resemblance as they grow older or, on the contrary, the resemblance may become more positive in later years. Orthodontic treatment that affects the facial profile and late adolescent growth can be responsible for change in genetic resemblance and also affect the good result obtained by the orthodontist in his treatment if the change is unfavorable. Malrelation of facial components (as, for example, between teeth and jaw size) has been attributed to racial mixture. However, as Stewart and Spence point out, studies in Hawaii showed that hybridization has no positive effect on increased malocclusion. Superimposition of posteroanterior and lateral tracings of cephalograms most frequently used in orthodontic practice has been found to provide little reliable information on genetic evidence. Comparison of individual craniofacial components and functional matrices described by Moss is considered more reliable. Cervanka of the Minnesota School of Dentistry discusses prenatal aberration of certain chromosomes that can affect the development of facial structures. He presents an important list of phenotypic anomalies and their corresponding chromosomal defects. The recognition of the mutant chromosomes and their prenatal elimination is currently one of the main goals of cytogenetics. The foregoing enlarges the practice of dentistry, and especially of orthodontics, from their limited scope to a point where the dentist can be, in fact, the physician of the oral cavity by recognizing genetic aberrations in the early stages before their full establishment and thus practice preventive dental medicine as well as minister to the maintenance of the dentition. For the orthodontist, the awareness of genetic expression in the dentofacial maldevelopment of his patients, in addition to aiding the correction of malocclusion, will be an important factor in his practice of dentofacial orthopedics in fact as well as in theory. J. A. Salzmann
in clinical
G
enetic influence on the pathologic, structural, and morphologic maldevelopment of the dentofacial area is no longer of academic interest only to the practicing orthodontist. However, the clinical evaluation of genetic facies has to date been of extremely limited scope, and genetic influence as an aid in recognition, treatment, and patient counseling has received little or no attention. Parallel with the accelerated knowledge on general medical genetics has been the marked upsurge of research and publication of articles on the expression of genetics in facial, oral, and dental diseases and developmental aberrations. A recently published volume on Oral Facial Genetics* covers the various aspects of genetics in relation to dentofacial maldevelopment and malocclusion and presents a full account of oral and pathologic conditions. The seventeen outstanding research contributors to this volume are widely recognized for their knowledge of the respective subjects they present. This book is a landmark in dental science, of use to students and practitioners and as a source of reference to research workers. If he is familiar with this text, the orthodontist who is interested in doing more than move malposed teeth will find it unnecessary, when faced with an uncommon oral pathologic condition, to refer his patient to a general medical pathologist whose knowledge of the subject may not be more than cursory. Robert J. Gorlin of the School of Dentistry of the University of Minnesota, who discusses heritable mucocutaneous disorders, and M. M. Cohen, Jr. of the University of Washington, Seattle, who writes on dysmorphic syndromes with craniofacial manifestations, have broken new ground with the width and depth of their contributions. It is no longer doubted that orthodontists can successfully treat malocclusions and dentofacial deviations of genetic origin. They constantly treat such conditions and influence the vector if not also the amount of facial growth. Ray E. Stewart, a medical geneticist, and M. A. Spence, Ph.D., a psychiatrist, both of the University of California at Los Angeles, list malocclusion as the most common hereditary deviation in dentistry, followed by periodontal disease and dental caries. They point out that malocclusion can result from a mutation at a single gene locus. While it is not always clear to what extent phenotypic characters are of genetic or of environmental origin, we know that maldevelopment may be multifactorial and is in the nature of a continuum. It is not rare to find the same classification of malocclusion in :‘Stewart, R. E.. and Prescott, Mosby Company.
G. H. (editors):
Oral
Facial
Genetics,
St. Louis,
1978.
The C.
V.
467
468
Ediror-irrl
Am. J. Orthod. October 1978
parents and siblings, extending even to irregularity of a corresponding single tooth or a few teeth as a family trait. However, remarkable differences can be found also in parents and siblings and even in monozygous twins. The reason for these deviations is linked to muscular, functional, and neurogenic differences. While these occurrences usually are attributed to postnatal environmental causes, mutational heterogenicity exists in practically all human genes. Genetic traits in the craniofacial region are known to undergo change. Children who strongly resemble a parent may no longer show such resemblance as they grow older or, on the contrary, the resemblance may become more positive in later years. Orthodontic treatment that affects the facial profile and late adolescent growth can be responsible for change in genetic resemblance and also affect the good result obtained by the orthodontist in his treatment if the change is unfavorable. Malrelation of facial components (as, for example, between teeth and jaw size) has been attributed to racial mixture. However, as Stewart and Spence point out, studies in Hawaii showed that hybridization has no positive effect on increased malocclusion. Superimposition of posteroanterior and lateral tracings of cephalograms most frequently used in orthodontic practice has been found to provide little reliable information on genetic evidence. Comparison of individual craniofacial components and functional matrices described by Moss is considered more reliable. Cervanka of the Minnesota School of Dentistry discusses prenatal aberration of certain chromosomes that can affect the development of facial structures. He presents an important list of phenotypic anomalies and their corresponding chromosomal defects. The recognition of the mutant chromosomes and their prenatal elimination is currently one of the main goals of cytogenetics. The foregoing enlarges the practice of dentistry, and especially of orthodontics, from their limited scope to a point where the dentist can be, in fact, the physician of the oral cavity by recognizing genetic aberrations in the early stages before their full establishment and thus practice preventive dental medicine as well as minister to the maintenance of the dentition. For the orthodontist, the awareness of genetic expression in the dentofacial maldevelopment of his patients, in addition to aiding the correction of malocclusion, will be an important factor in his practice of dentofacial orthopedics in fact as well as in theory. J. A. Salzmann
