The contributions of craniofacial growth to clinical orthodontics

Abstract

Balanced facial form and functions are derived from a harmonious integration of the various components of the craniofacial complex. These components grow and develop throughout life in a sequential, predictable, and orderly fashion, albeit with a wide range of variation in the amount and timing of growth.The knowledge of growth-related changes is essential in planning orthodontic treatment. It is important to understand and anticipate the amount and relative rate of growth in different parts of the face, especially during childhood and adolescence. The orthodontist needs to assess the developmental status of the individual and estimate the remaining growth to plan treatment.Incremental growth curves made on linear measurements from longitudinal cephalometric radiographs have demonstrated that all facial dimensions have varying relative rates of growth and show small prepubertal and postpubertal growth spurts.1Nanda RS Cephalometric study of the human face from serial roentgenogram.Ergeb d Anat d Untwicklungs-Geschichte. 1956; 35: 358-419PubMed Google Scholar The pubertal spurt in facial dimensions was found to coincide with the spurt in skeletal growth, as reflected by body height, lasting 3 to 4 years. It is apparently of shorter duration and occurs earlier in females than in males. To determine the time of the peak growth period in facial dimensions for an individual, several maturity indicators have been tested. The closest relationship was found with skeletal maturation, which can be readily assessed from hand and wrist radiographs. In many cases orthodontic treatment should commence before the onset or early during the pubertal spurt in order to take advantage of the accelerated growth period.In some instances, prolonged nasorespiratory obstruction and certain metabolic diseases during the growth years may affect facial development. However, removal or correction of such an unfavorable environment may restore the genetic growth potential. This is an important observation, both from the view of orthodontic treatment and the stability of the treatment outcome.Orthodontic or orthopedic procedures are often used to modify the growth pattern in a growing patient. Such alterations are indeed feasible by appropriate treatment procedures. However, during posttreatment recovery, a major part of the gains may be lost. It must be remembered that orthodontic treatment is often completed during early adolescence, before the peak growth increment. Thus, dentofacial growth after the completion of orthodontic treatment may undo the treatment outcome. To gain stability of the correction, it is necessary to design retainer appliances from the perspective of preventing or attenuating unwanted effects of recovery of the inherent growth pattern.Diagnosis and treatment planning of an orthodontic patient must, therefore, include application of knowledge in craniofacial growth and dental development. Changes in skeletal and soft tissue integument during adolescent growth have to be included in the assessment. However, soft tissue growth is not well understood, and there is no direct correlation between the growth of skeletal and soft tissues.The integument varies considerably in thickness between individuals. An old adage is that children with a large symphysis would grow up to have an even larger one. However, when there is little symphysial prominence at the chin, the soft tissue chin can make up the deficiency.4Nanda RS Ghosh J Facial soft tissue harmony and growth in orthodontic treatment.Sem Orthod. 1995; 1: 67-81Abstract Full Text PDF PubMed Scopus (59) Google Scholar We have measured soft tissue thickness at the chin for as little as 5 mm and as much as 23 mm in adults.The potential growth at the mandibular symphysis has a profound effect on the facial profile; so does the growth of the nose. We have found that a balanced facial profile in a patient with a large nose and chin can tolerate more incisor procumbency to attain better balance in the nose, lips, and chin relationships. Longitudinal growth studies have revealed that the range of variation is much wider than presumed, and individuals differ in almost every attribute and characteristic. In diagnosis, application of rigid rules derived from average values of cephalometric measurements is, therefore, not valid. There may be compensations between teeth and jaws, which may create acceptable relationships.Class II relationships are the most predictable. Even during the period of primary dentition, a distal terminal plane relationship with little or no spacing between the teeth is usually destined for a Class II malocclusion. Crowding of teeth in the primary dentition is another ominous sign of malocclusion in the permanent dentition. The Leeway space,5Nanda RS Chawla JM Variability of leeway space.J Ind Dent Assoc. 1973; 45: 99-108Google Scholar on which so many orthodontists depend for alleviating crowding in the mandibular arch, is highly variable and in some cases may be absent altogether.Long face vertical growth patterns can be diagnosed even before the first molars have erupted.6Nanda SK Pattern of vertical growth in the face.Am J Orthod Dentofacial Orthop. 1988; 93: 103-116Abstract Full Text PDF PubMed Scopus (152) Google Scholar The most reliable criterion for diagnosis of a long face pattern is the percentage of lower face height. In such patients, if vertical dentoalveolar growth in the molar region can be controlled, the unfavorable dentitional attributes of such a facial pattern can be minimized.The growth of the lips differs, not just due to gender, but also because of different facial types. Long face individuals have more growth in length and thickness of lips. The gender difference of anticipated small growth changes in the lips, coupled with a relatively smaller mandibular growth potential for a female patient, may allow an orthodontist to make an early decision for treatment with extraction or orthognathic surgery.In conclusion, knowledge of growth and development of the craniofacial complex has provided a plethora of informational data on the pattern of individual facial growth and maturity. It has been clearly demonstrated that infinite amounts of variation exist in timing, duration, and amount of growth in different components of the face. Moreover, group norms based on averages used for comparison to determine the range of deviation must be used cautiously. No two individuals are alike and deviation in a particular measurement may be compensated by changes in other dimensions. Therefore, in each case, orthodontic treatment must be planned to carefully address individual needs. In order to obtain stability of the treatment outcome, retention has to be maintained for an indefinite amount of time to prevent future growth changes from undoing the treatment outcome.Future developmentsCraniofacial development and dental malocclusion reflect an interplay between a number of factors, including tooth size, arch size and shape, the number and arrangement of teeth, size and relationship of the jaws, and related soft tissues including lips, cheeks, and tongue. Barring the genetic syndromes, congenital defects, and trauma, most malocclusions may be considered variations from normal development.With so many factors involved, there is an assumption of multifactorial inheritance with both genetic and environmental influences. Pattern profiles of dental crown size show that both X and Y chromosomes exert growth-promoting effects on the size of the human tooth crown. The X chromosome appears to regulate enamel thickness, while the Y chromosome affects both enamel and dentin. The X and Y chromosomes also affect craniofacial development. Cephalometric analysis of a sample of 47 XXY males indicated pronounced facial prognathism, especially in the mandible.7Brown T Alvesalo L Townsend CG Craniofacial patterning in Klinefelter (47,XXY) adults.Europ J Orthod. 1993; 15: 185-194Crossref PubMed Scopus (21) Google Scholar The mandibular corpus length was larger, and there was a tendency for reduction of the cranial base angle. Studies of 45 X females indicated a retrognathic face with a short mandible and a flattened cranial base angle.8Laine T Alvesalo L Isotupa K Shape of the craniofacial complex in 45, X females: cephalometric study.J Craniofac Genet Dev Biol. 1989; 9: 331-338PubMed Google Scholar It is suggested that the X chromosome may alter morphology of the cranial base by affecting growth at the synchondroses.The developmental processes are regulated by networks of signal transduction pathways that relay and integrate information from outside the cell, through the plasma membrane and cytoplasm to the nucleus, to regulate the expression of target genes. The nucleus also influences factors in the cytoplasm, modifying the cell’s responsiveness to outside signals and affecting the activities of neighboring or distant cells.Lack of coordination in the linkage of genes, receptor dimerization and biochemical interferences may lead to disharmonious relationships. Bioengineering may provide the designs and tools such as growth factors or receptor antagonists to manipulate the proliferation, patterning, and differentiation of cells in culture to grow tissues and replace or augment those of a patient.Experiments with transgenic mice revealed that numerous genes are required for the development of organs and structures in embryos. These findings have led to the detection of defects in the same genes in human beings who possess specific syndromes. Moreover, molecular genetic research procedures have facilitated identification of gene defects that cause craniofacial anomalies in human beings.Many craniofacial defects are the outcome of formation of abnormal extracellular matrix molecules, such as collagen and elastin. However, most of these defects seem to result from the action of defective genes, mainly developmental regulatory, transcription factors, and intracellular signal molecules. In this manner, gene defects have now been identified in cases of hypodontia, ectodermal dysplasia, and craniosynostosis. Identification of specific gene defects is perceived to be the first step in the development of methods for treatment and prevention of craniofacial and other anomalies.As a result of these developments, new concepts in directing and redirecting tissue growth may emerge and be successfully applied to the craniofacial complex.At the dawn of the 21st century we witness vigorous advances in biological and computer sciences. Rapid developments in the latter field facilitate facial examination in 3 dimensions, photographically and radiographically, which promote better understanding of craniofacial growth and development by precise localization of areas and tissues involved in normal and abnormal processes. These tissues are the main targets of ongoing biological research. The outcome of these investigations will have far-reaching implications in our age-old desire to better understand the mechanisms that govern craniofacial growth and development. This increasing comprehension should hone our diagnostic and therapeutic talents in the foreseeable future. Balanced facial form and functions are derived from a harmonious integration of the various components of the craniofacial complex. These components grow and develop throughout life in a sequential, predictable, and orderly fashion, albeit with a wide range of variation in the amount and timing of growth. The knowledge of growth-related changes is essential in planning orthodontic treatment. It is important to understand and anticipate the amount and relative rate of growth in different parts of the face, especially during childhood and adolescence. The orthodontist needs to assess the developmental status of the individual and estimate the remaining growth to plan treatment. Incremental growth curves made on linear measurements from longitudinal cephalometric radiographs have demonstrated that all facial dimensions have varying relative rates of growth and show small prepubertal and postpubertal growth spurts.1Nanda RS Cephalometric study of the human face from serial roentgenogram.Ergeb d Anat d Untwicklungs-Geschichte. 1956; 35: 358-419PubMed Google Scholar The pubertal spurt in facial dimensions was found to coincide with the spurt in skeletal growth, as reflected by body height, lasting 3 to 4 years. It is apparently of shorter duration and occurs earlier in females than in males. To determine the time of the peak growth period in facial dimensions for an individual, several maturity indicators have been tested. The closest relationship was found with skeletal maturation, which can be readily assessed from hand and wrist radiographs. In many cases orthodontic treatment should commence before the onset or early during the pubertal spurt in order to take advantage of the accelerated growth period. In some instances, prolonged nasorespiratory obstruction and certain metabolic diseases during the growth years may affect facial development. However, removal or correction of such an unfavorable environment may restore the genetic growth potential. This is an important observation, both from the view of orthodontic treatment and the stability of the treatment outcome. Orthodontic or orthopedic procedures are often used to modify the growth pattern in a growing patient. Such alterations are indeed feasible by appropriate treatment procedures. However, during posttreatment recovery, a major part of the gains may be lost. It must be remembered that orthodontic treatment is often completed during early adolescence, before the peak growth increment. Thus, dentofacial growth after the completion of orthodontic treatment may undo the treatment outcome. To gain stability of the correction, it is necessary to design retainer appliances from the perspective of preventing or attenuating unwanted effects of recovery of the inherent growth pattern. Diagnosis and treatment planning of an orthodontic patient must, therefore, include application of knowledge in craniofacial growth and dental development. Changes in skeletal and soft tissue integument during adolescent growth have to be included in the assessment. However, soft tissue growth is not well understood, and there is no direct correlation between the growth of skeletal and soft tissues. The integument varies considerably in thickness between individuals. An old adage is that children with a large symphysis would grow up to have an even larger one. However, when there is little symphysial prominence at the chin, the soft tissue chin can make up the deficiency.4Nanda RS Ghosh J Facial soft tissue harmony and growth in orthodontic treatment.Sem Orthod. 1995; 1: 67-81Abstract Full Text PDF PubMed Scopus (59) Google Scholar We have measured soft tissue thickness at the chin for as little as 5 mm and as much as 23 mm in adults. The potential growth at the mandibular symphysis has a profound effect on the facial profile; so does the growth of the nose. We have found that a balanced facial profile in a patient with a large nose and chin can tolerate more incisor procumbency to attain better balance in the nose, lips, and chin relationships. Longitudinal growth studies have revealed that the range of variation is much wider than presumed, and individuals differ in almost every attribute and characteristic. In diagnosis, application of rigid rules derived from average values of cephalometric measurements is, therefore, not valid. There may be compensations between teeth and jaws, which may create acceptable relationships. Class II relationships are the most predictable. Even during the period of primary dentition, a distal terminal plane relationship with little or no spacing between the teeth is usually destined for a Class II malocclusion. Crowding of teeth in the primary dentition is another ominous sign of malocclusion in the permanent dentition. The Leeway space,5Nanda RS Chawla JM Variability of leeway space.J Ind Dent Assoc. 1973; 45: 99-108Google Scholar on which so many orthodontists depend for alleviating crowding in the mandibular arch, is highly variable and in some cases may be absent altogether. Long face vertical growth patterns can be diagnosed even before the first molars have erupted.6Nanda SK Pattern of vertical growth in the face.Am J Orthod Dentofacial Orthop. 1988; 93: 103-116Abstract Full Text PDF PubMed Scopus (152) Google Scholar The most reliable criterion for diagnosis of a long face pattern is the percentage of lower face height. In such patients, if vertical dentoalveolar growth in the molar region can be controlled, the unfavorable dentitional attributes of such a facial pattern can be minimized. The growth of the lips differs, not just due to gender, but also because of different facial types. Long face individuals have more growth in length and thickness of lips. The gender difference of anticipated small growth changes in the lips, coupled with a relatively smaller mandibular growth potential for a female patient, may allow an orthodontist to make an early decision for treatment with extraction or orthognathic surgery. In conclusion, knowledge of growth and development of the craniofacial complex has provided a plethora of informational data on the pattern of individual facial growth and maturity. It has been clearly demonstrated that infinite amounts of variation exist in timing, duration, and amount of growth in different components of the face. Moreover, group norms based on averages used for comparison to determine the range of deviation must be used cautiously. No two individuals are alike and deviation in a particular measurement may be compensated by changes in other dimensions. Therefore, in each case, orthodontic treatment must be planned to carefully address individual needs. In order to obtain stability of the treatment outcome, retention has to be maintained for an indefinite amount of time to prevent future growth changes from undoing the treatment outcome. Future developmentsCraniofacial development and dental malocclusion reflect an interplay between a number of factors, including tooth size, arch size and shape, the number and arrangement of teeth, size and relationship of the jaws, and related soft tissues including lips, cheeks, and tongue. Barring the genetic syndromes, congenital defects, and trauma, most malocclusions may be considered variations from normal development.With so many factors involved, there is an assumption of multifactorial inheritance with both genetic and environmental influences. Pattern profiles of dental crown size show that both X and Y chromosomes exert growth-promoting effects on the size of the human tooth crown. The X chromosome appears to regulate enamel thickness, while the Y chromosome affects both enamel and dentin. The X and Y chromosomes also affect craniofacial development. Cephalometric analysis of a sample of 47 XXY males indicated pronounced facial prognathism, especially in the mandible.7Brown T Alvesalo L Townsend CG Craniofacial patterning in Klinefelter (47,XXY) adults.Europ J Orthod. 1993; 15: 185-194Crossref PubMed Scopus (21) Google Scholar The mandibular corpus length was larger, and there was a tendency for reduction of the cranial base angle. Studies of 45 X females indicated a retrognathic face with a short mandible and a flattened cranial base angle.8Laine T Alvesalo L Isotupa K Shape of the craniofacial complex in 45, X females: cephalometric study.J Craniofac Genet Dev Biol. 1989; 9: 331-338PubMed Google Scholar It is suggested that the X chromosome may alter morphology of the cranial base by affecting growth at the synchondroses.The developmental processes are regulated by networks of signal transduction pathways that relay and integrate information from outside the cell, through the plasma membrane and cytoplasm to the nucleus, to regulate the expression of target genes. The nucleus also influences factors in the cytoplasm, modifying the cell’s responsiveness to outside signals and affecting the activities of neighboring or distant cells.Lack of coordination in the linkage of genes, receptor dimerization and biochemical interferences may lead to disharmonious relationships. Bioengineering may provide the designs and tools such as growth factors or receptor antagonists to manipulate the proliferation, patterning, and differentiation of cells in culture to grow tissues and replace or augment those of a patient.Experiments with transgenic mice revealed that numerous genes are required for the development of organs and structures in embryos. These findings have led to the detection of defects in the same genes in human beings who possess specific syndromes. Moreover, molecular genetic research procedures have facilitated identification of gene defects that cause craniofacial anomalies in human beings.Many craniofacial defects are the outcome of formation of abnormal extracellular matrix molecules, such as collagen and elastin. However, most of these defects seem to result from the action of defective genes, mainly developmental regulatory, transcription factors, and intracellular signal molecules. In this manner, gene defects have now been identified in cases of hypodontia, ectodermal dysplasia, and craniosynostosis. Identification of specific gene defects is perceived to be the first step in the development of methods for treatment and prevention of craniofacial and other anomalies.As a result of these developments, new concepts in directing and redirecting tissue growth may emerge and be successfully applied to the craniofacial complex.At the dawn of the 21st century we witness vigorous advances in biological and computer sciences. Rapid developments in the latter field facilitate facial examination in 3 dimensions, photographically and radiographically, which promote better understanding of craniofacial growth and development by precise localization of areas and tissues involved in normal and abnormal processes. These tissues are the main targets of ongoing biological research. The outcome of these investigations will have far-reaching implications in our age-old desire to better understand the mechanisms that govern craniofacial growth and development. This increasing comprehension should hone our diagnostic and therapeutic talents in the foreseeable future. Craniofacial development and dental malocclusion reflect an interplay between a number of factors, including tooth size, arch size and shape, the number and arrangement of teeth, size and relationship of the jaws, and related soft tissues including lips, cheeks, and tongue. Barring the genetic syndromes, congenital defects, and trauma, most malocclusions may be considered variations from normal development. With so many factors involved, there is an assumption of multifactorial inheritance with both genetic and environmental influences. Pattern profiles of dental crown size show that both X and Y chromosomes exert growth-promoting effects on the size of the human tooth crown. The X chromosome appears to regulate enamel thickness, while the Y chromosome affects both enamel and dentin. The X and Y chromosomes also affect craniofacial development. Cephalometric analysis of a sample of 47 XXY males indicated pronounced facial prognathism, especially in the mandible.7Brown T Alvesalo L Townsend CG Craniofacial patterning in Klinefelter (47,XXY) adults.Europ J Orthod. 1993; 15: 185-194Crossref PubMed Scopus (21) Google Scholar The mandibular corpus length was larger, and there was a tendency for reduction of the cranial base angle. Studies of 45 X females indicated a retrognathic face with a short mandible and a flattened cranial base angle.8Laine T Alvesalo L Isotupa K Shape of the craniofacial complex in 45, X females: cephalometric study.J Craniofac Genet Dev Biol. 1989; 9: 331-338PubMed Google Scholar It is suggested that the X chromosome may alter morphology of the cranial base by affecting growth at the synchondroses. The developmental processes are regulated by networks of signal transduction pathways that relay and integrate information from outside the cell, through the plasma membrane and cytoplasm to the nucleus, to regulate the expression of target genes. The nucleus also influences factors in the cytoplasm, modifying the cell’s responsiveness to outside signals and affecting the activities of neighboring or distant cells. Lack of coordination in the linkage of genes, receptor dimerization and biochemical interferences may lead to disharmonious relationships. Bioengineering may provide the designs and tools such as growth factors or receptor antagonists to manipulate the proliferation, patterning, and differentiation of cells in culture to grow tissues and replace or augment those of a patient. Experiments with transgenic mice revealed that numerous genes are required for the development of organs and structures in embryos. These findings have led to the detection of defects in the same genes in human beings who possess specific syndromes. Moreover, molecular genetic research procedures have facilitated identification of gene defects that cause craniofacial anomalies in human beings. Many craniofacial defects are the outcome of formation of abnormal extracellular matrix molecules, such as collagen and elastin. However, most of these defects seem to result from the action of defective genes, mainly developmental regulatory, transcription factors, and intracellular signal molecules. In this manner, gene defects have now been identified in cases of hypodontia, ectodermal dysplasia, and craniosynostosis. Identification of specific gene defects is perceived to be the first step in the development of methods for treatment and prevention of craniofacial and other anomalies. As a result of these developments, new concepts in directing and redirecting tissue growth may emerge and be successfully applied to the craniofacial complex. At the dawn of the 21st century we witness vigorous advances in biological and computer sciences. Rapid developments in the latter field facilitate facial examination in 3 dimensions, photographically and radiographically, which promote better understanding of craniofacial growth and development by precise localization of areas and tissues involved in normal and abnormal processes. These tissues are the main targets of ongoing biological research. The outcome of these investigations will have far-reaching implications in our age-old desire to better understand the mechanisms that govern craniofacial growth and development. This increasing comprehension should hone our diagnostic and therapeutic talents in the foreseeable future.