growth n development postnatal

POST NATAL POST NATAL DEVELOPMENTDEVELOPMENT

Dr. Imtiaz AhmedDr. Imtiaz Ahmed BDS, FCPS BDS, FCPS

ASSISTANT PROFESOR ASSISTANT PROFESOR DEPTT. OF ORTHODONTICS DEPTT. OF ORTHODONTICS

PRIMARY DENTITION YEARSPRIMARY DENTITION YEARS(INFANCY AND EARLY (INFANCY AND EARLY

CHILDHOODCHILDHOOD))

MATURATION OF ORAL FUNCTIONMATURATION OF ORAL FUNCTION

The principal physiologic functions of the oral cavity are The principal physiologic functions of the oral cavity are respiration, swallowing, mastication and speech.respiration, swallowing, mastication and speech.

Once the airway is established the next physiologic Once the airway is established the next physiologic priority is to obtain milk form the mother’s mammary priority is to obtain milk form the mother’s mammary gland and transfer it to the GIT. This is accomplished by gland and transfer it to the GIT. This is accomplished by suckling and swallowingsuckling and swallowing..

This sequence of events define an infantile swallow, This sequence of events define an infantile swallow, which is characterized by active contractions of the lips, which is characterized by active contractions of the lips, a tongue tip brought forward into contact with the lower a tongue tip brought forward into contact with the lower lip and little activity of the posterior tongue or pharyngeal lip and little activity of the posterior tongue or pharyngeal musculature. The suckling reflex and the infantile musculature. The suckling reflex and the infantile swallow normally disappear during the first year of life.swallow normally disappear during the first year of life.

MATURATION OF ORAL FUNCTIONMATURATION OF ORAL FUNCTION Maturation of oral function can be characterized in Maturation of oral function can be characterized in

general as following from anterior to posterior. At birth general as following from anterior to posterior. At birth the lips are relatively mature and capable of vigorous the lips are relatively mature and capable of vigorous suckling activity, whereas more posterior structures are suckling activity, whereas more posterior structures are quite immature. As time progresses greater activity by quite immature. As time progresses greater activity by the posterior parts of the tongue and more complex the posterior parts of the tongue and more complex motions the pharyngeal structures are required.motions the pharyngeal structures are required.

This principle of front to back maturation is particularly This principle of front to back maturation is particularly well illustrated by the acquisition of speech. The first well illustrated by the acquisition of speech. The first speech sounds are the bilabial sounds m, p and b. Later speech sounds are the bilabial sounds m, p and b. Later the tongue consonants like t and d appear. The sibilant the tongue consonants like t and d appear. The sibilant sounds which require that the tongue tip be placed close sounds which require that the tongue tip be placed close to but not against the palate, come later, and the last to but not against the palate, come later, and the last speech sound which requires precise positioning of the speech sound which requires precise positioning of the posterior tongue, often s not acquired until the age of 4 posterior tongue, often s not acquired until the age of 4 or 5.or 5.


The chewing pattern of the adult is quite different from The chewing pattern of the adult is quite different from that of a typical child, an adult typically opens the moves that of a typical child, an adult typically opens the moves the jaw laterally and brings the teeth into contact, the jaw laterally and brings the teeth into contact, whereas a child moves the same jaw laterally on whereas a child moves the same jaw laterally on opening. The transition from the juvenile to adult chewing opening. The transition from the juvenile to adult chewing pattern appears to develop in conjunction with eruption pattern appears to develop in conjunction with eruption of the permanent canine sat about age 12. of the permanent canine sat about age 12.

ERUPTION OF PRIMARY TEETHERUPTION OF PRIMARY TEETH


At birth neither the maxillary nor the mandibular At birth neither the maxillary nor the mandibular alveolar process is well developed. Occasionally alveolar process is well developed. Occasionally a Natal tooth may be present although the a Natal tooth may be present although the primary teeth normally do not erupt until primary teeth normally do not erupt until approximately 6 months of age.approximately 6 months of age.

The dates of eruption are relatively variable, The dates of eruption are relatively variable, upto 6 months of acceleration or delay is within upto 6 months of acceleration or delay is within the normal range. The eruption sequence the normal range. The eruption sequence however is usually preserved. One can expect however is usually preserved. One can expect that the mandibular central incisors will erupt that the mandibular central incisors will erupt first, closely followed by the other incisors. first, closely followed by the other incisors.


After a 3 to 4 month interval, the mandibular and After a 3 to 4 month interval, the mandibular and maxillary first molars except, followed in another 3 or 4 maxillary first molars except, followed in another 3 or 4 months by the maxillary and mandibular canines, which months by the maxillary and mandibular canines, which nearly fill the space between the lateral incisor and first nearly fill the space between the lateral incisor and first molarmolar

The primary dentition is usually completed at 24 to 30 The primary dentition is usually completed at 24 to 30 months as the mandibular, and then the maxillary months as the mandibular, and then the maxillary second molars erupt.second molars erupt.

Spacing is normal throughout the anterior part of the Spacing is normal throughout the anterior part of the dentition but is most noticeable in two locations called dentition but is most noticeable in two locations called the Primate Spaces. In the maxillary arch, the primate the Primate Spaces. In the maxillary arch, the primate space is located between the lateral incisors and space is located between the lateral incisors and canines, whereas in the mandibular arch, the space is canines, whereas in the mandibular arch, the space is between the canines and first molars.between the canines and first molars.

MIXED DENTITION YEARSMIXED DENTITION YEARS(EARLY CHILDHOOD)(EARLY CHILDHOOD)

PHYSICAL DEVELOPMENT IN LATE PHYSICAL DEVELOPMENT IN LATE CHILDHOODCHILDHOOD

By age 7, a child has essentially completed his or her By age 7, a child has essentially completed his or her neural growth. The brain and the brain case are as large neural growth. The brain and the brain case are as large as will ever be.as will ever be.

Lymphoid tissue throughout the body has proliferated Lymphoid tissue throughout the body has proliferated beyond the usual adult levels and large tonsils and beyond the usual adult levels and large tonsils and adenoids are common.adenoids are common.

In contrast, growth of the sex organs has hardly begun In contrast, growth of the sex organs has hardly begun and general body growth is only modestly advanced.and general body growth is only modestly advanced.

During early childhood, the rate of general body growth During early childhood, the rate of general body growth declines from the rapid pace of infancy; then stabilizes at declines from the rapid pace of infancy; then stabilizes at a moderate lower level during late childhood.a moderate lower level during late childhood.

ERUPTION OF THE PERMANENT TEETHERUPTION OF THE PERMANENT TEETH

PRE EMERGENT SPURT: PRE EMERGENT SPURT: Eruptive movements begin soon after tooth movements Eruptive movements begin soon after tooth movements

begin. This supports the idea that metabolic activity begin. This supports the idea that metabolic activity within the PDL is necessary for eruption.within the PDL is necessary for eruption.

Two processes are necessary for eruption. Firstly, there Two processes are necessary for eruption. Firstly, there must be resorption of bone and primary tooth roots must be resorption of bone and primary tooth roots overlying the crown of the erupting tooth. Second, the overlying the crown of the erupting tooth. Second, the eruption mechanism itself the must move the tooth in the eruption mechanism itself the must move the tooth in the direction where the path has been cleared.direction where the path has been cleared.

Resorption is the rate limiting factor in pre emergent Resorption is the rate limiting factor in pre emergent eruption. The overlying bone and primary teeth resorb eruption. The overlying bone and primary teeth resorb and the eruption mechanism then moves the tooth in to and the eruption mechanism then moves the tooth in to the space created by the resorption the space created by the resorption

ERUPTION OF THE PERMANENT ERUPTION OF THE PERMANENT TEETHTEETH

Other possibilities for eruption mechanism include Other possibilities for eruption mechanism include variations in blood pressure or flow, forces derived from variations in blood pressure or flow, forces derived from contractions of fibroblasts and alterations in the extra contractions of fibroblasts and alterations in the extra cellular ground substance of the PDLcellular ground substance of the PDL..


POST EMERGENT SPURT:POST EMERGENT SPURT: The stage of relatively rapid eruption from the time of a The stage of relatively rapid eruption from the time of a

tooth first penetrates the gingiva until it reaches the tooth first penetrates the gingiva until it reaches the occlusal level is called the Post emergent spurt.occlusal level is called the Post emergent spurt.

It has been observed that eruption occurs only during a It has been observed that eruption occurs only during a critical period between 8 pm and midnight or 1AM. critical period between 8 pm and midnight or 1AM. During the early morning hours, and the day, the tooth During the early morning hours, and the day, the tooth stops erupting and often intrudes slightly. This is stops erupting and often intrudes slightly. This is probably related to the very similar cycle of growth probably related to the very similar cycle of growth hormone release.hormone release.


The eruption mechanism may be different after The eruption mechanism may be different after emergence. Collagen cross linking in the PDL is more emergence. Collagen cross linking in the PDL is more prominent after a tooth comes into occlusal function, so prominent after a tooth comes into occlusal function, so shortening of collagen fibers as the mechanism seems shortening of collagen fibers as the mechanism seems more likely.more likely.

During the juvenile equilibrium teeth that are in function During the juvenile equilibrium teeth that are in function erupt at a rate that parallels the rate of vertical growth of erupt at a rate that parallels the rate of vertical growth of the mandibular ramus. As the mandible continues to the mandibular ramus. As the mandible continues to grow, it moves away from the maxilla creating a space grow, it moves away from the maxilla creating a space into which teeth erupt.into which teeth erupt.


After a tooth is in the mouth, the forces opposing After a tooth is in the mouth, the forces opposing eruption are those from chewing, soft pressure from eruption are those from chewing, soft pressure from lips cheeks, or tongue contacting the teeth.lips cheeks, or tongue contacting the teeth.

Light pressures of long duration are more important Light pressures of long duration are more important in producing orthodontic movementin producing orthodontic movement

When the pubertal growth spurt ends, a final phase When the pubertal growth spurt ends, a final phase in tooth eruption called the adult equilibrium is in tooth eruption called the adult equilibrium is achieved.achieved.

During adult life, teeth continue to erupt at an During adult life, teeth continue to erupt at an extremely slow rate. If its antagonist is lost at any extremely slow rate. If its antagonist is lost at any stage, a tooth can erupt more rapidly demonstrating stage, a tooth can erupt more rapidly demonstrating that the eruption mechanism remains active and that the eruption mechanism remains active and capable of producing significant tooth movement capable of producing significant tooth movement even late in life.even late in life.

SPACE REPLACEMENT FOR INCISORSSPACE REPLACEMENT FOR INCISORS

The permanent incisor teeth are considerably larger than The permanent incisor teeth are considerably larger than the primary incisors that they replace. The mandibular the primary incisors that they replace. The mandibular permanent central incisor is about 5.5 mm in width, permanent central incisor is about 5.5 mm in width, whereas the primary central it replaces is about 3 mm in whereas the primary central it replaces is about 3 mm in width width

Spacing in the primary incisor region is normally Spacing in the primary incisor region is normally distributed among all the incisors, not just in the “primate distributed among all the incisors, not just in the “primate space” locations where permanent spaces exist.space” locations where permanent spaces exist.

In the maxillary arch, the primate space is located mesial In the maxillary arch, the primate space is located mesial to the canines while in the mandibular arch, it is located to the canines while in the mandibular arch, it is located distal to the canine. The total amount of spacing is distal to the canine. The total amount of spacing is therefore similar in the two arches.therefore similar in the two arches.

SPACE REPLACEMENT FOR SPACE REPLACEMENT FOR INCISORSINCISORS

When the central incisors erupt, they consume all of the When the central incisors erupt, they consume all of the excess space in the normal primary dentition and with excess space in the normal primary dentition and with the eruption of the lateral incisors, space becomes tight the eruption of the lateral incisors, space becomes tight in both arches.in both arches.

The maxillary arch has just enough space to The maxillary arch has just enough space to accommodate the permanent lateral incisors when they accommodate the permanent lateral incisors when they erupt while in the mandibular arch, when the lateral erupt while in the mandibular arch, when the lateral incisors erupt , there is an average 1.6 mm less space incisors erupt , there is an average 1.6 mm less space available for the for mandibular incisors than would be available for the for mandibular incisors than would be required to perfectly align them. This difference between required to perfectly align them. This difference between the amount of space required for the incisors and the the amount of space required for the incisors and the amount available for them is called INCISOR LIABILITY amount available for them is called INCISOR LIABILITY

SPACE REPLACEMENT FOR SPACE REPLACEMENT FOR INCISORSINCISORS

The mandibular permanent central incisors are almost The mandibular permanent central incisors are almost always in proximal contact from the time that they erupt always in proximal contact from the time that they erupt but in the maxillary arch, there may be a space present but in the maxillary arch, there may be a space present called the DIASTEMA between the permanent central called the DIASTEMA between the permanent central incisors.incisors.

This space tends to close when the laterals tend to erupt This space tends to close when the laterals tend to erupt but may persist even after the laterals have erupted. This but may persist even after the laterals have erupted. This situation may be present as a variation of the normal and situation may be present as a variation of the normal and is then called as the UGLY DUCKLING STAGE of is then called as the UGLY DUCKLING STAGE of development.development.

SPACE REPLACEMENT FOR CANINES SPACE REPLACEMENT FOR CANINES AND PRIMARY MOLARSAND PRIMARY MOLARS

The permanent premolars are The permanent premolars are smaller than the teeth they smaller than the teeth they replace. The mandibular primary replace. The mandibular primary second molar is on the average second molar is on the average 2mm larger than the second 2mm larger than the second molar, while in the maxillary arch molar, while in the maxillary arch the primary second molar is the primary second molar is 1.5mm larger. 1.5mm larger.

The primary first molar is only The primary first molar is only slightly larger than the first slightly larger than the first premolar but contributes an extra premolar but contributes an extra 0.5 mm in the mandible.0.5 mm in the mandible.

The result is that each side in the The result is that each side in the mandibular arch contains about mandibular arch contains about 2.5 mm of LEEWAY SPACE 2.5 mm of LEEWAY SPACE


When the second primary molars are lost, the When the second primary molars are lost, the first permanent molars move into mesially into first permanent molars move into mesially into the leeway space. This decreases both arch the leeway space. This decreases both arch length and arch circumference length and arch circumference

A normal relationship of the primary molar is the A normal relationship of the primary molar is the flush terminal plane relationship. The primary flush terminal plane relationship. The primary dentition equivalent of angle’s class II is the dentition equivalent of angle’s class II is the Distal step and a Mesial step corresponds to an Distal step and a Mesial step corresponds to an angle’s Class I an equivalent of angle’s Class III angle’s Class I an equivalent of angle’s Class III is almost never seen in the primary dentition.is almost never seen in the primary dentition.


At the time the primary second molars are lost, both the At the time the primary second molars are lost, both the maxillary and mandibular molars tend to shift mesially maxillary and mandibular molars tend to shift mesially into the leeway space, but the mandibular molar normally into the leeway space, but the mandibular molar normally moves mesially more than its maxillary counterpart. This moves mesially more than its maxillary counterpart. This contributes to the normal transition from a flush terminal contributes to the normal transition from a flush terminal plane relationship in the mixed dentition to a Class I plane relationship in the mixed dentition to a Class I relationship in the permanent dentitionrelationship in the permanent dentition

EARLY PERMANENT DENTITION EARLY PERMANENT DENTITION YEARSYEARS

(ADOLESCENCE)(ADOLESCENCE)

PUBERTAL STAGES IN GIRLSPUBERTAL STAGES IN GIRLS

Adolescence in girls can be divided into three stages: Adolescence in girls can be divided into three stages: The FIRST STAGE which occurs at about the beginning The FIRST STAGE which occurs at about the beginning of physical growth spurt is the appearance of breast of physical growth spurt is the appearance of breast buds and early stages of the development of pubic hair. buds and early stages of the development of pubic hair. The peak velocity for physical growth occurs about 1 The peak velocity for physical growth occurs about 1 year after the initiation of stage I and coincides with the year after the initiation of stage I and coincides with the SECOND STAGE of development. At this time, there is SECOND STAGE of development. At this time, there is noticeable breast development. Pubic hair is darker and noticeable breast development. Pubic hair is darker and hairs appear in the armpits. The THIRD STAGE in girls hairs appear in the armpits. The THIRD STAGE in girls occurs 1 to 1.5 years after stage II and is marked by occurs 1 to 1.5 years after stage II and is marked by onset of menstruation. By this time, the growth spurt is onset of menstruation. By this time, the growth spurt is all but complete. At this stage, there is noticeable all but complete. At this stage, there is noticeable broadening of the hips with more adult fat distribution broadening of the hips with more adult fat distribution and development of breast is complete and development of breast is complete

PUBERTAL STAGES IN BOYSPUBERTAL STAGES IN BOYS

The initial sign is Fat spurt. The maturing boy becomes The initial sign is Fat spurt. The maturing boy becomes fat and chubby and this relates to the estrogen fat and chubby and this relates to the estrogen production by the Leydig cells in the testes before the production by the Leydig cells in the testes before the Sertoli cells predominate. At this time the scrotum begins Sertoli cells predominate. At this time the scrotum begins to increase in size and change in pigmentation.to increase in size and change in pigmentation.

At stage II, about 1 year after stage I, the spurt in height At stage II, about 1 year after stage I, the spurt in height is just beginning. Pubic hair begins to appear and growth is just beginning. Pubic hair begins to appear and growth of the penis begins of the penis begins

PUBERTAL STAGES IN BOYSPUBERTAL STAGES IN BOYS

The third stage occurs 8 to 12 months after stage II and The third stage occurs 8 to 12 months after stage II and coincides with the peak velocity in gain in height. At this coincides with the peak velocity in gain in height. At this time, axillary hair appears and facial hair appears on the time, axillary hair appears and facial hair appears on the upper lip only. A spurt in muscle growth also occurs with upper lip only. A spurt in muscle growth also occurs with a decrease in subcutaneous fat. Pubic hair distribution a decrease in subcutaneous fat. Pubic hair distribution appears and the penis and scrotum are nearly adult size.appears and the penis and scrotum are nearly adult size.

Stage IV for boys, occurs anywhere between 15 to 24 Stage IV for boys, occurs anywhere between 15 to 24 months after stage III. At this time, the spurt of growth in months after stage III. At this time, the spurt of growth in height ends. There is facial hair on the chin as well as height ends. There is facial hair on the chin as well as the upper lip, adult distribution and color of pubic and the upper lip, adult distribution and color of pubic and axillary hair and a further increase in muscular strength axillary hair and a further increase in muscular strength

NASOMAXILLARY COMPLEXNASOMAXILLARY COMPLEX

MAXILLARY TUBEROSITY AND ARCH MAXILLARY TUBEROSITY AND ARCH LENGTHENINGLENGTHENING

The horizontal lengthening of the bony maxillary arch is The horizontal lengthening of the bony maxillary arch is produced by remodelingproduced by remodeling

at the maxillary tuberosity (depository). The arch also at the maxillary tuberosity (depository). The arch also widens and the maxillary sinus increases in size. widens and the maxillary sinus increases in size.

The maxillary tuberosity is important in clinical The maxillary tuberosity is important in clinical orthodontics. It is also a major orthodontics. It is also a major "site""site" of maxillary growth of maxillary growth (but it is not the only site of growth).(but it is not the only site of growth).

The position of the maxillary tuberosity is established by The position of the maxillary tuberosity is established by the posterior boundary of the anterior cranial fossa.the posterior boundary of the anterior cranial fossa.

The whole maxilla undergoes a simultaneous process of The whole maxilla undergoes a simultaneous process of primary displacementprimary displacement in an in an anterioranterior and and inferiorinferior direction as it grows and lengthens posteriorlydirection as it grows and lengthens posteriorly

MAXILLARY TUBEROSITY AND ARCH MAXILLARY TUBEROSITY AND ARCH LENGTHENINGLENGTHENING

It is believed that the stimulus for sutural bone growth It is believed that the stimulus for sutural bone growth (remodeling)(remodeling) relates to the relates to the tensiontension produced by the produced by the displacement displacement of bone. Thus, as the entire maxilla is of bone. Thus, as the entire maxilla is carried forward and downward by displacement, the carried forward and downward by displacement, the osteogenic osteogenic suturalsutural membranes form new bone tissue membranes form new bone tissue that enlarges the overall size of the whole bone and that enlarges the overall size of the whole bone and sustains constant bone-to-bone sutural contactsustains constant bone-to-bone sutural contact..

NASOMAXILLARY REMODELLINGNASOMAXILLARY REMODELLING

Clinically and biologically, all inside and outside parts, Clinically and biologically, all inside and outside parts, regions, and surfaces participate directly in growth.regions, and surfaces participate directly in growth.

Furthermore, because of the developmental and Furthermore, because of the developmental and functional interrelations among all the regions, what functional interrelations among all the regions, what occurs in any one region is not developmentally isolated occurs in any one region is not developmentally isolated from the othersfrom the others

NASAL AIRWAYNASAL AIRWAY

The lining surfaces of the bony walls and floor of the The lining surfaces of the bony walls and floor of the nasal chambers are predominantly resorptive except for nasal chambers are predominantly resorptive except for the nasal side of the olfactory fossae.the nasal side of the olfactory fossae.

This produces a lateral and anterior expansion of the This produces a lateral and anterior expansion of the nasal chambers and a downward relocation of the nasal chambers and a downward relocation of the palate; the oral side of the bony palate is depository.palate; the oral side of the bony palate is depository.

PALATAL REMODELLINGPALATAL REMODELLING

The external (labial) side of the whole anterior part of the The external (labial) side of the whole anterior part of the maxillary arch is resorptive, with bone being added onto maxillary arch is resorptive, with bone being added onto the inside of the arch, the arch increases in width, and the inside of the arch, the arch increases in width, and the palate becomes wider. (the "V" principle).the palate becomes wider. (the "V" principle).

Growth along the midpalatal suture plays a role in the Growth along the midpalatal suture plays a role in the progressive widening of theprogressive widening of the

palate and alveolar arch.palate and alveolar arch. As the palate grows inferiorly by the remodeling process, As the palate grows inferiorly by the remodeling process,

a nearly complete exchange of old for new hard and soft a nearly complete exchange of old for new hard and soft tissue occurs.tissue occurs.

Rapid or slow palatal expansion has become a very Rapid or slow palatal expansion has become a very common clinical technique. This is not a "biologic" common clinical technique. This is not a "biologic" procedure procedure

CHEEK BONE AND ZYGOMATIC ARCHCHEEK BONE AND ZYGOMATIC ARCH

The growth changes of the malar complex are similar to The growth changes of the malar complex are similar to those of the maxilla itself. This is true for both those of the maxilla itself. This is true for both remodeling and displacement processes.remodeling and displacement processes.

The malar region and anterior part of the zygoma The malar region and anterior part of the zygoma undergo posterior remodeling (relocation) movement.undergo posterior remodeling (relocation) movement.

The inferior edge of the zygoma is heavily depository.The inferior edge of the zygoma is heavily depository. The zygomatic arch moves laterally by resorption on the The zygomatic arch moves laterally by resorption on the

medial side within the temporal fossa and by deposition medial side within the temporal fossa and by deposition on the lateral side.on the lateral side.

As the As the malarmalar region grows and becomes relocated region grows and becomes relocated posteriorly, the posteriorly, the nasalnasal region is enlarging in an opposite, region is enlarging in an opposite, anterior direction, drawing out the nose and making the anterior direction, drawing out the nose and making the face deeper, antero posteriorly. face deeper, antero posteriorly.

CHEEK BONE AND ZYGOMATIC CHEEK BONE AND ZYGOMATIC ARCHARCH

The zygoma and cheekbone complex becomes The zygoma and cheekbone complex becomes displaced anteriorly and inferiorly in the same directions displaced anteriorly and inferiorly in the same directions and amount as the primary displacement of the maxilla.and amount as the primary displacement of the maxilla.

The growth changes of the The growth changes of the malar processmalar process are similar are similar to those of the mandibular to those of the mandibular coronoid processcoronoid process , its , its counterpart.counterpart.

MANDIBLEMANDIBLE

RAMUSRAMUS

Provides an attachment site for Provides an attachment site for masticatorymasticatory muscles. muscles. Plays an important role in placing the corpus and dental Plays an important role in placing the corpus and dental

arch into ever changing fit with the growing maxilla and arch into ever changing fit with the growing maxilla and the face's limitless structural variations. The rams adjusts the face's limitless structural variations. The rams adjusts in alignment, vertical length, and anteroposterior in alignment, vertical length, and anteroposterior breadth.breadth.

EveryEvery area and surface throughout the entire mandible area and surface throughout the entire mandible participates directly in its remodeling process; some sites participates directly in its remodeling process; some sites are more active than others.are more active than others.

Ramus remodeling is important because (1) it Ramus remodeling is important because (1) it posit ionsposit ions the lower arch in occlusion with the upper, and (2) it is the lower arch in occlusion with the upper, and (2) it is continuously continuously adaptiveadaptive to the multitude of changing to the multitude of changing craniofacial conditions craniofacial conditions

RAMUSRAMUS

The principal vectors of mandibular "growth" are The principal vectors of mandibular "growth" are posterior and superior. The ramus is posterior and superior. The ramus is remodeledremodeled in a in a generally posterosuperior manner while the mandible as generally posterosuperior manner while the mandible as a whole is displaced anteriorly and inferiorly. This allows a whole is displaced anteriorly and inferiorly. This allows lengthening of the corpus and dental arch.lengthening of the corpus and dental arch.

Parts of the ramus undergo remodeling conversion into Parts of the ramus undergo remodeling conversion into the mandibular corpusthe mandibular corpus..

LINGUAL TUBEROSITYLINGUAL TUBEROSITY

The The l ingual tuberosityl ingual tuberosity is the direct anatomic is the direct anatomic equivalent of the equivalent of the maxil larymaxil lary tuberositytuberosity . Both are major . Both are major sites of the growth for the mandible and maxilla, sites of the growth for the mandible and maxilla, respectively.respectively.

Forms a boundary between the ramus and corpus of the Forms a boundary between the ramus and corpus of the mandible. It is mandible. It is notnot visible \ in headfilms. visible \ in headfilms.

It grows posteriorly by deposits on its posterior facing It grows posteriorly by deposits on its posterior facing surface. As this takes place, that part of the surface. As this takes place, that part of the ramusramus just just behind the tuberosity remodels behind the tuberosity remodels mediallymedially . (The ramus is . (The ramus is coming into line with the axis of the arch in order to join coming into line with the axis of the arch in order to join it.)it.)

The The prominenceprominence of the tuberosity is augmented by the of the tuberosity is augmented by the resorptive resorptive l ingual fossalingual fossa

MANDIBULAR CONDYLEMANDIBULAR CONDYLE

A major site of growth, having considerable clinical A major site of growth, having considerable clinical significance.significance.

It is It is notnot a pacesetting "master center" with all other a pacesetting "master center" with all other regional growth fields subordinate to and dependent on it regional growth fields subordinate to and dependent on it for direct control. (Although it was once believed to be for direct control. (Although it was once believed to be so.)so.)

Growth of the mandible is the aggregate expression of Growth of the mandible is the aggregate expression of all it localized centers.all it localized centers.

Carti lageCart i lage is a special is a special non-vascularnon-vascular tissue and is tissue and is involved at the condyle because variable levels of involved at the condyle because variable levels of compression occur at its articular contact with the compression occur at its articular contact with the temporal bone of the basicranium. It has a temporal bone of the basicranium. It has a hydrophil ichydrophil ic intercellular matrix.intercellular matrix.


An An endochondralendochondral growth mechanism is required for growth mechanism is required for this part of the mandible because the condyle grows in a this part of the mandible because the condyle grows in a direction toward its articulation into the face of direction toward its articulation into the face of direct direct pressure.pressure.

The condylar cartilage has a The condylar cartilage has a secondarysecondary type of type of cartilage, which developed because of the changed cartilage, which developed because of the changed functional and developmental conditions imposed upon functional and developmental conditions imposed upon this part of the mandible. The secondary cartilage is not this part of the mandible. The secondary cartilage is not the pacemaker for the growth of the mandible. It the pacemaker for the growth of the mandible. It functions to provide functions to provide regional adaptive growthregional adaptive growth ..

The condylar cartilage is phylogenetically and The condylar cartilage is phylogenetically and ontogenetically unique and differs in histologic ontogenetically unique and differs in histologic organization from most other growth cartilages involved organization from most other growth cartilages involved in endochondral bone formation. It is not structurally in endochondral bone formation. It is not structurally comparable to a long bone's cartilaginous epiphyseal comparable to a long bone's cartilaginous epiphyseal plate plate


The condyle performs a more functional role. It (1) The condyle performs a more functional role. It (1) provides a pressure-tolerant articular contact and (2) it provides a pressure-tolerant articular contact and (2) it makes possible a multidimensional growth capacity in makes possible a multidimensional growth capacity in response to ever-changing, developmental conditions response to ever-changing, developmental conditions and variations.and variations.

A A capsularcapsular layer of poorly vascularized connective layer of poorly vascularized connective tissue covers the articular surface of the condyle. Below tissue covers the articular surface of the condyle. Below this is a layer of prechondroblast cells, cartilage and this is a layer of prechondroblast cells, cartilage and endochondral bone. endochondral bone.

growth n development postnatal

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