Craniofacial Growth and Development PDF

CRANIOFACIAL GROWTH AND DEVELOPMENT Dr. Reham Ibrahim Abdel Raouf El-Gazzar  Growth Vs. Development !! ❖Growth: Growth in general has been defined as an increase in size, which is a physiological process of all living organisms. Increase in size is associated with an obvious increase...

CRANIOFACIAL GROWTH AND DEVELOPMENT Dr. Reham Ibrahim Abdel Raouf El-Gazzar  Growth Vs. Development !! ❖Growth: Growth in general has been defined as an increase in size, which is a physiological process of all living organisms. Increase in size is associated with an obvious increase in weight, mass of the extracellular matrix and spatial dimensions. Growth is also accompanied by an increase in the number of cells and their sizes. ❖Development: Development refers to a stage of growth and maturation encompassing morphogenesis, differentiation, and acquisition of functionality. Development means progress towards maturity. ❖Growth and development although closely related, are not synonyms Growth Development Change in size and Increase in number(quantitative) complexity(qualitative) Physiologic and Anatomic phenomena behavioural Measured by growth Measured by degree of increment specialization  Growth Phases 1. Prenatal growth: Rapid rise in cell number and growth rate. 2. Postnatal growth: First 20 y of life – decrease growth rate – tissue maturation. 3. Maturity: Period of equilibrium between cellular loss and gain. 4. Old age: Functional activity decline.  Different tissues grow at different times and at different rates: 1- Neural tissues: grow rapidly during prenatal and early postnatal life. The brain attains 90% of its full size by 6 years. There is no evidence of any spurt for the neural growth. 2- Lymphoid tissues: reach 100% adult size by 7 years, proliferate far beyond the adult size in late childhood (200% by 14 years) then they start to decline to be 100% at age 20 years. 3-Somatic (general) tissues: growth continues till around 18- 20 years (maxilla, mandible, cartilage, skeleton) and follows S-shaped curve. Increase rapidly prenatally, decline few weeks before birth, increase in first months after birth, decline slowly till growth spurt (11-13 years in girls, 13 – 15 years in boys), then grow slowly till 20 years. 4- Genital tissues: accelerate rapidly around the onset of puberty  Growth Spurts Growth spurts are periods of sudden rapid increases of body growth. Human growth is not a steady and uniform process of acceleration in which all body parts enlarge at the same rate and same increment per year. Mainly three spurts are seen:  Human Velocity Chart  Clinical Significance Of The Growth Spurts To differentiate whether growth changes are normal or abnormal. Treatment of skeletal discrepancies is more advantageous if carried out in the mixed dentition period, especially during the juvenile growth spurt. Orthognathic surgery should be carried out after growth ceases.  Factors affecting growth and maturation 1. Genetic factors. 2. Growth hormones. 3. Nutrition. 4. Illness. 5. Psychological stress  Terminology related to growth: ❑Growth fields: It is the area of bone covered from inside and outside by soft tissue , cartilage or osteogenic membranes and responsible for alteration of the growing bone. ❑Growth sites: They are growth fields that have special significance in the growth of a particular bone, e.g. mandibular condyle in the mandible and maxillary tuberosity in the maxilla. ❑Remodeling: It is a differential growth activity involving deposition and resorption of the inner and outer surface of the bone e.g. mandible moves posteriorly by a combination of resorption and deposition.  The study of growth and development of the head in Orthodontics is very important in answering the following questions: 1. How the face changes from its embryologic form through childhood, adolescence and adulthood. 2. How and where the growth occurs, how much growth is remaining and in which direction and when the growth will express itself. 3. What role the genetic and environmental factors play in influencing facial growth and in turn how orthodontists can influence these factors with treatment to achieve the optimum results in each individual.  Methods of studying physical growth There are different methods for studying the craniofacial growth. Methods of studying growth can be classified into two as: 1. Quantitative 2. Qualitative  Quantitative methods Craniometry: It is the method of taking measurements directly from the skull. The craniometry study is based on measurements of skull framed among human remains. It is advantageous since precise measurement can be taken directly from the skull.  Quantitative methods Anthropometry: Anthropometry method involves the measurement of living human skull. In this method, certain landmarks are taken on the soft tissues over the human skull and then direct measurements are made taking the soft tissue into consideration. The anthropometric measurement can be both cross-sectional and longitudinal. Any individual or group can be studied for several years taking the measurements of skull and face  Quantitative methods Cephalometry: In this method, the radiograph of the skull is taken in a standardized setting, and the measurements are made on the radiographs. Serial cephalograms are taken for the study of growth and measured. Cephalometrics has been extensively used in understanding the nature of craniofacial growth.  Quantitative methods Implant method: tantalum pins, 1.5 mm long and 0.5 mm in diameter, at selected sites in facial bones and skulls of children subjects to study growth. Serial cephalograms were then made and superimposed and measurements between the implants were taken to find the relative direction and extent of growth.. Implant methods to study growth may be difficult to perform in present day scenario due to ethical reasons.  Qualitative methods Vital staining: Dyes have been used to study bone growth. These products have a greater tendency to react with the calcium/proteins during the bone mineralization stage and have an inhibitory influence on bone formation. These methods of studying bone growth are feasible only in experimental animals.  Qualitative methods Autoradiography: The radioactive substances that bind with the active growth metabolites are injected into body These radioactively labelled metabolites release emissions which produce an image in a photographic emulsion. These isotopes are highly concentrated at the active sites of growth and inflammation  Mechanisms of Craniofacial Bone Growth There are mainly four different concepts that would govern facial growth mechanism: 1. Cartilaginous(endochondral) growth 2. Sutural growth 3. Periosteal and endosteal(intramembranous) growth 4. Functional matrix concept  Mechanisms of Craniofacial Bone Growth Cartilaginous (endochondral) growth: Precursor cartilage model is made then replaced by bone. eg. base of the skull, nasal septum and the head of mandibular condyles.  Mechanisms of Craniofacial Bone Growth Sutural growth: sutural growth is active in bringing the bones into close proximity The union of the different sutures takes place at different stages of life. eg. The bony sutures of the head were considered capable of increasing the size of the head in all dimensions as independent growth centres. Sutures are considered only as growth sites and not growth centres. The sutures remain important intramembranous growth sites of craniofacial skeleton  Mechanisms of Craniofacial Bone Growth Periosteal and endosteal (intramembranous) growth: The apposition of bone on the selective periosteal surfaces and simultaneously resorption at some other selective surface. Necessary to maintain the appropriate thickness to the cortical layer of bone. Eg : skull vault, nasal, oral cavities and sinuses.  Mechanisms of Craniofacial Bone Growth Functional matrix concept: the face grows as a response to functional needs and neurotrophic influences which are mediated by the soft tissue around the bones, This concept can be supported by the fact that when the Patient is suffering from hydrocephaly, the bony cranium size increase and when the size of the brain is small, the cranium is correspondingly smaller. The origin, growth and maintenance of skeletal tissues and organs are secondary and compensatory responses to events and processes, occurring in related non- skeletal tissues, organs and functioning spaces called functional matrices. The functional matrices include muscles, nerves, glands and teeth  The Skull At Birth One of the most striking features of a new-born child is the large size of the head in relation to the rest of the body. This is because at birth, the cranial vault is approximately two-thirds of its final dimension, due to extensive prenatal development of the brain. The skull of the neonate differs significantly from that of an adult as follows: a) The face of the infant skull is disproportionately small because the nasal cavity, maxilla and mandible are all poorly developed. b) All of the individual bones within the neonatal skull are smaller than those in the adult. Six fontanelles or fibrous membranes are present in the neonatal skull  Postnatal growth The postnatal growth movement of craniofacial structures takes place due to drift and displacement. Drift is a process in which the combination of deposition and resorption of the bone results in growth movement towards the depositary surface. The primary displacement occurs when bone gets displaced as a result of its own growth. secondary displacement. If the bone gets displaced as a result of growth and enlargement of an adjacent bony structures  Postnatal growth of craniofacial complex Viscero- Neurocranium cranium (face) Nasomaxillary Cranial Vault complex N.B. Cranial base Mandible. Cranial vault & face Intramembranous ossification. Cranial base Endochondral ossification  Cranial Vault It is divided into segments by sutures (fontanelles) that are sufficiently wide to be palpable at birth. The edges of the bones joining the sutures become approximated during the first two years of postnatal life. Concurrently with growth in the sutures, apposition and absorption adjust the shape of each bone to decrease the curvature of the skull as the cranium is enlarged. After the age of seven years, the thickness of these bones increase by apposition of bone on their external surface. About the age of puberty, the development and extension of the frontal sinuses accompany rapid additions of bone to the facial surface of the frontal bone  Cranial base Cranial base is the platform on which the face develops. Therefore the growth of cranial base affects the structures, line angles and placement of facial parts. Bones of the cranial base are formed by endochondral ossification and centres of ossification appear in chondrocranium early in embryonic life. These primary cartilages remain between centres of ossification after birth and play a significant role in postnatal growth of cranial base. These bands of cartilage between the cranial base bones are called synchondroses. Synchondrosis is similar to two sided epiphyseal plate with proliferating cartilage cells in the centre and mature cartilage cells and ossification occurring in both directions away from centre.  Cranial base The spheno-occipital synchondrosis contributes the most in the growth of cranial base as it is the last cranial base suture to ossify. The spheno-occipital synchondrosis is closed by 13-15 years of age. The synchondrosis causes the elongation of the middle portion of the cranial base as a result of primary displacement. Growth due to remodelling process of resorption from the inside and deposition from outside in the cranial fossa leads to the cortical drift. The direction of growth is along an axis that is directed forward and upward. It therefore carries the upper part of the face and the anterior half of the base of the cranium bodily upwards and forwards. This upward movement is compensated by downward growth of the face itself  Nasomaxillary Complex There are different mechanisms of growth which contribute to the nasomaxillary growth. They can be divided into two methods: a) Sutural growth. b) Surface apposition.  Nasomaxillary Complex A. Sutural growth The system of sutures that unit the bones of the upper part of the face to the cranium include the following sutures: Zygomatico-temporal Fronto-nasal Zygomatico-frontal Fronto-maxillary Zygomatico-maxillary Pterygo-palatine Growth at these sutures carries the upper face downwards and forwards and increases the height of the orbit (almost attain its full size at the age of 7 years) but not the infra nasal height. After the age of seven years, the sutures play a little part in vertical growth of the face.  Nasomaxillary Complex A. Sutural growth The whole nasomaxillary complex moves in an inferior direction due to new bone addition at the sutures. As the middle cranial fossa grows, it causes the maxilla to move in anterior and inferior direction which is called secondary displacement. The secondary displacement is an important growth mechanism during primary dentition period but becomes less important as growth of cranial base slows down  Nasomaxillary Complex B. Surface apposition Growth of maxilla takes place by surface apposition over most of the facial or anterior surface of the maxilla and the zygomatic process. The body and alveolar process of the maxilla grow forward at a higher rate than the zygomatic arch that grows outward by addition of bone to its outer surface and resorption on the inner surface,so the inferior root of the zygomatic process occupies first a position over E and later over the root of upper 6 As the maxilla increase in size, the maxillary sinus and the frontal sinus are extended by resorption on the inner surface of their walls.  Nasomaxillary Complex B. Surface apposition Vertical growth of maxilla takes place between the age of five and fifteen years. It occurs largely by apposition of bone at the alveolar margin, which is accompanied by addition of bone to the palate though to a lesser extent, causing an apparent deepening of the palate and the floor of the maxillary sinus comes to lie below the level of the inferior meatus of the nose. Lateral growth of the lower part of the maxilla is achieved by downward and outward growth of the alveolar process. The horizontal lengthening of maxilla occurs by apposition on maxillary tuberosity.  Mandible Shape at birth ▪ The mandible is little more than a curved bar of bone. ▪ The coronoid, angular and alveolar processes are underdeveloped ▪ At each upper end of the mandible a cap of cartilage represents the condyle and merges into the ramus. ▪ The 2 caps are centres from which growth causes increase of mandibular length. The growth here is by: ▪ Surface apposition of cartilage. ▪ Interstitial growth of cartilage.  Mandible A. Condyle: It grows Upward…increase length of ramus Backward…increase anteroposterior length Outward…increase intracondylar width Developing and preservation of the shape of the neck of the condyle occur by resorption and apposition of bone on the surface.  Mandible B. Coronoid: It grows by addition of bone to its posterior surface and resorption at the anterior border as the vertical ramus grows upward, backward and outward with the condyle C. Alveolar process It grows upward, outward and forward Upward…by bone apposition to the inferior surface Outward…by bone apposition to the lateral and anterior surface…increase thickness Forward…by bone resorption of the anterior border of the ascending ramus providing space for the accommodation of the permanent teeth  Mandible D. The Angle At birth …it is about 175 degree By addition of bone to the posterior border of the ramus…decrease the angle to 115 degree in the adult E. Midline Suture The two halves of the mandible are united by a suture in the midline This is closed by the age of one year After this age lateral growth in anterior part of the mandible takes place by apposition of bone on the outer surfaces and a little resorption on the inner surfaces  Mandible F. Mental Foramen During the early years of life, it is situated under the first deciduous molar. In the adult, it lies below and between the roots of the first and second premolars. This change in position is due to the backward and outward inclination of the canal, addition of bone to the outer surface of the body of the mandible which carries the foramen backward, and the upward and forward growth of the alveolar process carries the teeth forward relative to the mental foramen G. Chin The chin of the human beings becomes gradually prominent as individual grows from childhood to an adult. The deposition occurs at the mental protuberance and resorption at the alveolar portion which causes the chin to become prominent.  Late skeletal growth Growth is a continuous process from birth till it reaches a slow rate that characterizes adult size. The most rapid skeletal growth occurs in pubertal growth spurt and the increase in height of adolescents at puberty is quite obvious. Growth in width is completed first followed by growth in length and finally growth in height. Growth in width of both jaws and the dental arches will complete before the pubertal growth spurt.  Late skeletal growth Maxillary growth in downward and forward direction(length) can continue 2- 3 years after the attainment of puberty, whereas mandibular horizontal growth will continue longer than maxillary complex. The vertical height of the face and jaws does not reach adult proportions until later, 17 or 18 years of age in girls and the early 20s in boys. Changes in the soft tissue profile are greater than changes in the facial skeleton, these being an elongation of the nose, flattening of the lips, and increasing prominence of the chin  Growth considerations Orthodontic therapeutic interventions and prognosis are influenced by the growth status and growth trend of the patient For all orthodontic patients, the growth assessment should be carried out as a routine with the help of various growth assessment parameters like height weight charts, canine calcification stages,, hand-wrist radiographs, and cervical vertebral maturation index. Functional jaw orthodontic therapy takes advantages of redirection of remaining growth of craniofacial region. Effectiveness of these appliances to modify skeletal growth is minimal after pubertal growth spurt.  Growth considerations Maxillary horizontal growth is completed much earlier than mandible and so the use of headgear to restrict or redirect its growth should be started much before pubertal growth spurt in mixed dentition period. Maxillary expansion procedures in cases of jaw constriction should be carried out during early mixed dentition. Growth in width of maxilla occurs by sutural growth in interpalatine and intermaxillary sutures. Maximum growth occurs in first 5 years. The skeletal expansion procedures should be carried out before the fusion of palatal sutures. Active growth cessation is prerequisite for orthognathic surgery particularly in cases with mandibular prognathism