Postnatal growth and development of mandible

GOOD MORNING

GOOD MORNING

POST-NATAL GROWTH AND

DEVELOPMENT OF MANDIBLE

CONTENTS

1. Introduction.

2. Anatomy of mandible.

3. Definitions.

4. Theories of growth.

5. Mechanisms of bone growth.

6. Skeletal units of mandible.

7. Main sites of growth of mandible.

8. Condyle and current concept.

9. Age changes in mandible.

10. Anomalies in growth.

11. Clinical Considerations.

12. Conclusion.

13. Questions.

14. References.

INTRODUCTION

• MANDIBLE (from Latin mandibula, "jawbone”)

largest and the strongest bone of the face

serves for the reception of the lower teeth.

consists of a curved, horizontal portion, the body and two perpendicular portions,

the rami, which unites with the ends of body nearly at right angles.

ANATOMY

Mandible

U-shaped body Ramus

Two Surfaces Two Borders

2 Surfaces

4 Borders

2 Processes

DEFINITIONS

• DEPOSITION: Process of addition of bone by osteoblastic activity.

• RESORPTION : Removal of bone by osteoclastic activity

• DRIFT : Relocation of bone by simultaneous deposition and resorption

processes on the opposing periosteal and endosteal surfaces.

DEFINITIONS

• DISPLACMENT: Movement away from a certain position or place.

• Primary displacement: Occurs in conjunction with own growth.

• Secondary Displacement: Caused by enlargement of adjacent bones or soft

tissues, but not of the bone itself.

DEFINITIONS

• REMODLING: Reshaping of the outline of the bone by selective

resorption and deposition in some areas.

• RELOCATION: Relative movement in space of bone due to deposition on

one side.

THEORIES OF GROWTH

1. Genetic theory- Brodie,1941

2. Scott’s hypothesis, 1953

3. Sutural dominance theory- Sicher,1955

4. Functional matrix theory- Moss, 1962

5. Van Limborgh’s theory- 1970

6. Servo System, Petrovic,1977

7. Enlow’s Expanding V Principle

8. Enlow’s Counterpart Principle

GENETIC THEORY

SCOTT’S HYPOTHESIS

SUTURAL DOMINANCE

FUNCTIONAL MATRIX THEORY

• The origin, form, function of all skeletal units are secondary, compensatory

and mechanically obligatory responses to chronologically and

morphologically prior events that occur in specifically related non-skeletal

tissues, organs or functioning spaces.

Cranial Component

Skeletal Unit

Micro Skeletal

Macro Skeletal

Functional Unit

Periosteal Capsular

VAN LIMBORGH’S THEORY

• Multifactorial

• Five factors controls growth:

1. Intrinsic genetic

2. Local epigenetic

3. General epigenetic

4. Local environmental

5. General environmental.

SERVO SYSTEM

• Condylar cartilage growth is integrated in an organized functional whole

that has the form of a servo system and is able to modulate the lengthening

of condyle so that the lower jaw adapts to the maxilla during growth.

ENLOW’S “V” PRINCIPLE

• Growth movement and

enlargement of many facial and

cranial bones or parts of bones

occur towards the wide ends of

“V”

• Bone deposition- inner and wide

end; ends of 2 arms of V

• Bone resorption-Outer surface

ENLOW’S COUNTERPART PRINCIPLE

• Growth of any given facial or cranial part relates specifically to other

structural and geometric “counterparts” in the face and cranium.

• Maxilla and mandible arches are mutual counterparts.

• Bony maxilla and corpus are mutual counterparts.

• Maxillary tuberosity and lingual tuberosity are counterparts.

Regional part Counter part

Balanced growth

FOOT AND SHOE PRINCIPLE

MECHANISMS OF BONE GROWTH

1. REMODELING

2. DISPLACEMENT:-

• Primary displacement

• Secondary displacement

GROWTH CENTERS V/S GROWTH SITES

• Growth Site: A site of growth is merely a location at which where growth

occurs.

• Growth Centre: A location at which is independent growth occurs.

• All centers are sites and the reverse is not true.

Sites in mandible : Condyle and Ramus

GROWTH TIMINGS

• Overall growth of mandible takes place at different stages.

• First there is increase in its

1. Width

2. Length

3. Height

MAIN SITES OF GROWTH OF MANDIBLE

• Principal growth sites are:-

1. Posterior surface of ramus

2. Condylar process

3. Coronoid process/ alveolar process

SKELETAL UNITS OF MANDIBLE

THE RAMUS

• Ramus remodels in posterio superiorly

Mandible gets displaced anteriorly and inferiorly

Allows posterior lengthening of the corpus of the dental arch.

• Lower part of ramus below coronoid process:-

Twisted contour:-

Buccal side – depository surface

Lingual side –resorptive surface

• Posterior margin :-

major site of remodeling.

It is one of the most active areas during mandibular growth in distance moved and amount

of histogenic activity.

• Mandibular foramen:-

It relocates backward and upwards by deposition on the anterior and resorption on

posterior part of its rim.

THE LINGUAL TUBEROSITY

• Counter part of the maxillary tuberosity.

• Marks effective boundary between the ramus and the corpus.

• Grows posterio-medially by deposits on posterior and medial

facing surface.

• Protrude tuberosity in lingual direction towards the midline.

• Periosteal resorption in the lingual fossa below and deposition on

medial facing surface

• Accentuates the prominence.

RAMUS TO CORPUS REMODELING

CONVERSION

Deposits on lingual side of ramus ,the part which is present

behind the lingual tuberosity.

Lingual shift of anterior part of ramus

Comes in line of corpus to join it

Former anterior ramal bone now posterior part of corpus

Corpus lengthening

THE CORONOID PROCESS

• It has propeller-like twist

Lingual side faces

Posteriorly superiorly medially

• Buccal surface :-

Has resorptive type of periosteal surface. This

surface faces away from combined superior,

medial, posterior directions of growth.

• Superior surface(lingual side):-

bone deposition growth superiorly increased vertical dimension

Enlarging V principle with V oriented Vertically

• Medial surface:-

same deposits of bone

carry base of coronoid process and anterior part of

ramus medially

Thus add to lengthening of corpus which lies well

medial to coronoid process

Thus early childhood ramus(1)

relocated and former location becomes posterior part of

corpus(2).

THE MANDIBULAR CONDYLE

• Regarded as a cornucopia from which the whole mandible itself pours forth.

. OLD THINKING:

Ultimate determinant of the amount , direction, rate

of growth, and overall mandibular size and shape.

Pacesetting “master center” with all other regional

growth fields subordinate to and dependent on it for

direct control.

• NEW THINKING:

• The condyle functions as a regional field of growth that provides an adaptation for its

own localized growth circumstances, just as all other fields accommodate.

• Thus the growth of mandible as a whole is the product of all the different regional

forces and regional functional agents of growth control acting on it.

Condylar Cartilage

• Special non vascular tissue.

• The intercellular matrix

hydrophilic

Turgid and Unyielding to surface

pressure.

• Functional significance:-

o An avascular and matrix-firm adaptation

for regional pressure

o Movable articulation

• Secondary type of cartilage ie. It does not

develop by differentiation from the primary

cartilages of fetal skull.

a)The condylar cartilage

b)Endochondral bony tissue in

medullary portion of condyle.

c)The enclosing bony

cortices.(tension related)

HISTOLOGY

• Capsular layer:-

poorly vascularized CT, covers articular surface of condyle,with age become

densly fibrous.

• Zone of growth:-

Prechondroblasts, site for cellular proliferation.

• Zone of maturation:-

functional and hypertrophied chondroblasts.

• Zone of erosion:-

degenerating chondroblasts.

• Zone of endochondral ossification

NECK OF THE CONDYLE

• Lingual and buccal surfaces resorptive

• Thus condyle is broad and neck narrow

• Endosteal deposition of new bone

along with periosteal resorption .

• V-shaped neck is moving

superoposteriorly .

SYMPHYSIS MENTI

• 4-12th month after birth, syndesmosis is converted to synostosis

• No widening after fusion

THE ADAPTIVE ROLE OF THE CONDYLE

• Random arrangement of condylar

prechondroblasts

• Is histogenetic adaptation of condylar

cartilage

• by selective proliferation of prechondroblasts

in some parts with retardation of cell divisions

in other parts around the periphery of the

condyle.

• Multidirectional growth potential

• Condylar growth is an active respondent, that

can adapt to the widely variable conditions

imposed on it.

• Mandibular condylar cartilage is the center of greatest growth in the

craniofacial complex, and is associated with maxillofacial skeleton

morphogenesis.

• This hybrid tissue may play an important role in regulating different rates

of bone formation in intramembranous and endochondral ossification,

allowing for highly diverse growth directions and condylar and

maxillofacial morphology.*

• *Growth of the mandible and biological characteristics of the mandibular

condylar cartilage, Japanese Dental Science Review (2013) 49, 139—150

HUMAN CHIN

• Man is one of the only two species having chin.(and elephant)

• Chin is one of the most variable areas in the entire mandible as seen among

the different basic facial types and patterns.

• Remodeling process:-

• During descend of maxillary arch and vertical drift of the

mandibular teeth

The anterior mandibular teeth simultaneously drift lingually

and superiorly.

Produces anterior overjet and overbite

• Same time:-

Bone deposition in the mandibular basal bone area including

mental protuberance(chin).

• This two-way growth process results- progressive enlarging

mental protuberance

THE MANDIBULAR BODY(CORPUS)

• Depositon :- outer surfaces on both buccal and

lingual sides.

• Resorption:-

- from endosteal surfaces.

- periosteal areas on labial surface of the incisor

region

- below lingual tuberosity

• Effects:- enlarges breadth of corpus.

• The buccal side remodels, to a slightly greater extent than lingual

because bony arch width increases slightly during post natal development,

but not much in comparison to maxillary arch width.

• Ventral border of corpus is also depository.

• Amount of upward alveolar growth greatly exceeds the extent of downward

enlargement by basal bone.

• Basal bone area has higher threshold of resistance to extrinsic forces than

alveolar bone(labile).

• However there no structural line separating basal bone from alveolar bone

rather this is more of physiologic than anatomic difference.

ALVEOLAR PROCESS

• Formation is influenced by dental eruption and it resorbs when teeth are exfoliated or extracted.

• It serves as a “buffer zone” -helps to maintain occlusal relationships during differential mandibular and midface growth.

• Vertical growth persists into adult life to compensate for the occlusal surfaces wear of teeth.

• Adaptive nature makes orthodontic tooth movements possible.

FACTORS AFFECTING MANDIBULAR GROWTH

• Systemic factors

1. Genetic

2. Hormonal

3. Nutritional

4. Illness

FACTORS AFFECTING MANDIBULAR

GROWTH

• Local factors

1. Ankylosis

2. Trauma

3. Birth injury

4. Ear infection

GROWTH MALFORMATIONS

• Pertti Pirttiniemi et al (EJO-2009) - Abnormal mandibular growth and the

condylar cartilage.

• Based on etiology and time of appearance:-

1) congenital malformations with associated growth disorders,

(2) primary growth disorders, and

(3) acquired diseases or trauma with associated growth disorders.

PRIMARY GROWTH DISORDERS

• 1) Condylar Hyperplasia

PRIMARY GROWTH DISORDERS

• 2) Condylar Hypoplasia

ACQUIRED DISEASES OR TRAUMA

WITH ASSOCIATED GROWTH

DISORDERS

• Juvenile idiopathic arthritis :- a chronic inflammatory disease of

unknown aetiology, which is present for longer than 6 weeks and starts

before the age of 16 years

• TMJ ankylosis

OTHER DISORDERS

• Paget’s disease: Caused by the excessive breakdown and formation of

bone, followed by disorganized bone remodeling.

• Achondroplasia: Achondroplasia is a common cause of dwarfism. It

occurs as a sporadic mutation in approximately 80% of cases (associated

with advanced paternal age)

• Condylar resorption* :Idiopathic condylar resorption, ICR, and

condylysis, is a disorder in which one or both of the mandibular condyles

are broken down in a bone resorption process. This disorder is nine times

more likely to be present in females than males, and is more common

among teenagers

* Wolford L. Idiopathic condylar resorption of the temporomandibular joint in teenage girls (cheerleaders syndrome) Proc (Bayl

Univ Med Cent) 2001;14(3):246–252.

OTHER DISORDERS

• Nager syndrome or acrofacial dysostosis - associated with condylar

ankylosis.

• Turner syndrome - short mandibular body and posterior rotation of the

mandible.

• Hemifacial atrophy or Parry-Romberg syndrome - affect mandibular

growth and lead to progressive facial asymmetry.

• Acromegaly - Oversized mandible.

• Proteus syndrome - shows unilateral condylar overgrowth causing

progressive craniofacial asymmetry.

AGE CHANGES IN MANDIBLE

AT BIRTH

• The body of the bone is a mere shell, containing the sockets of the two

incisor, the canine, and the two deciduous molar teeth, imperfectly

partitioned off from one another.

• The mandibular canal is of large size, and runs near the lower border of the

bone

• The mental foramen opens beneath the socket of the first deciduous molar

tooth.

• The angle is obtuse (175°)

• Condyloid portion is nearly in line with the body.

• The coronoid process is of comparatively large size, and projects above the

level of the condyle.

AGE CHANGES IN MANDIBLE

AFTER BIRTH

the two segments of the bone become joined at the symphysis, from below

upward, in the first year;

but a trace of separation may be visible in the beginning of the second year,

near the alveolar margin.

The body becomes elongated in its whole length, but more especially

behind the mental foramen, to provide space for the three additional teeth

developed in this part.

AGE CHANGES IN MANDIBLE

The depth of the body increases owing to increased growth of the alveolar

part, to afford room for the roots of the teeth, and by thickening of the

subdental portion which enables the jaw to withstand the powerful action of

the masticatory muscles;

The alveolar portion is the deeper of the two, and, consequently, the chief

part of the body lies above the oblique line.

The mandibular canal, after the second dentition, is situated just above the

level of the mylohyoid line;

The mental foramen occupies the position usual to it in the adult. The angle

becomes less obtuse, owing to the separation of the jaws by the teeth; about

the fourth year it is 140°.

AGE CHANGES IN MANDIBLE

IN THE ADULT

The alveolar and subdental portions of the body are usually of equal depth.

The mental foramen opens midway between the upper and lower borders of

the bone, and the mandibular canal runs nearly parallel with the mylohyoid

line.

The ramus is almost vertical in direction, the angle measuring

from 110° to 120°.

AGE CHANGES IN MANDIBLE

IN OLD AGE

The bone becomes greatly reduced in size, for with the loss of the teeth the

alveolar process is resorbed, and, consequently, the chief part of the bone is

below the oblique line.

The mandibular canal, with the mental foramen opening from it, is close to

the alveolar border.

The ramus is oblique in direction, the angle measures about 140°, and the

neck of the condyle is more or less bent backward.

PRIMARY CARTILAGE VS SECONDARY

CARTILAGE

• The two types of cartilages show differences in histological organization

and in the pattern of cell proliferation (Delatte et al. 2004).

• In primary cartilages, interstitial cell proliferation occurs in chondrocytes,

whereas secondary cartilage shows appositional proliferation (Durkin,

1972; Copray et al. 1986).

• During development, primary cartilage reacts primarily to systemic growth

stimuli such as hormones. By contrast, the secondary cartilage only

secondarily follows these overall stimuli after additional modulation by

local growth factors (Enlow, 1992; Sperber, 2001).

• The primary and secondary cartilages have different embryonic origins.

Primary cartilages are considered to be part of the primary skeletal

cartilage.

• Secondary cartilages appear later in embryonic development and are

independent of the primary skeletal cartilage.

GROWTH BY SECONDARY CARTILAGE.

• It occurs mainly by secondary cartilages (mainly condylar cartilage), this

helps in:

• Increase in height of the mandibular ramus

• Increase in the overall length of the mandible

• Increase of the inter condylar distance

CLINICAL CONSIDERATIONS

• Pattern of growth of mandible follows the general body growth with

increase during puberty.

• Vertical height and length of mandible –

Girls- 9-13 years

Boys- 11-17 years

Mandibular growth completes by- 17 years of age in girls.

DVELOPMENT OF OCCLUSION AND

MANDIBULAR GROWTH

• Primary Dentition: Mandibular incisors erupt at about 6-7months.

Vertical growth of the alveolar process is rapid

during tooth eruption

• Mixed Dentition Phase: Differential forward growth of the mandible

increase in the length of the corpus

EFFECT OF FUNCTIONAL APPLIANCES

• Effect on functional appliances on mandibular growth on skeletal Class Ⅱmalocclusion: A systematic review

• Objective: To examine the hypothesis that functional appliances enhance

mandibular growth in the treatment of skeletal Class Ⅱ malocclusion

• Conclusion: Functional appliances can enhance mandibular growth in

treatment of skeletal Class Ⅱ malocclusion. This mainly dues to the growth

of the ramus instead of changes of mandibular body length.

EFFECT OF FUNCTIONAL APPLIANCES

• Mandibular changes produced by functional appliances in Class II

malocclusion: a systematic review

• Aim: review of the literature was to assess the scientific evidence on the

efficiency of functional appliances in enhancing mandibular growth in

Class II subjects.

• Conclusion: Herbst appliance showed the highest coefficient of efficiency

(0.28 mm per month) followed by the Twin-block (0.23 mm per month).

EFFECT OF FUNCTIONAL APPLIANCES

• Mandibular changes during functional appliance treatment

• AIM: To determine the changes in position and size of the mandible in

children treated with either the Fränkel function regulator or Harvold

activator

• CONCLUSION:Main effects of both appliances were to allow vertical

development of the mandibular molars and increase the height of the face.

The Harvold appliance also proclined the lower incisors and increased

mandibular arch length.

PLANNING OF ORTHOGNATHIC

SURGERY

• Orthognathic surgery has little inhibitory effect on facial growth.

• Some authors suggest an early operation maybe beneficial altering the

remaining growth.

• Precious and colleagues reported:

more than 69% of growing patients who had an early Orthognathic surgery

had CLASS II malocclusion.

• Several reports on stability of mandibular advancements during childhood

and its effect on growth.

PLANNING OF ORTHOGNATHIC

SURGERY

• Freihofer reported a series :

patients under 17 yrs

BSSO surgery

mandible grew another 1.5-2 degrees post operatively.

• Wolford et al reported that

post-operatively growth occurred in vertical direction

patients who under went BSSO

age range of 8-16 years

Consensus in literature: Mandibular advancement in children can be performed

safely with no adverse effect on lower jaw development.

PLANNING OF ORTHOGNATHIC

SURGERY

• In growing children developing teeth and inferior nerve closely

approximate the inferior border.

Genioplasty delayed until 12 years of age or older.

Augmentation genioplasty with alloplastic implants performed at an earlier age

MANDIBULAR GROWTH AND TRAUMA

• The management is different from adults. Differs in

Anatomic variation

Rapidity of healing

Patient co-operation

Potential changes

• In Lund’s study of mandibular growth after condylar fracture-

Results: The fractured ramus which initially shorter had a greater

incremental growth rate

Conclusion: Lund defined 3 types of growth rates:

Compensatory growth with out over growth-fractured side grows more than normal side. End it remains somewhat shorter . Clinically –facial asymmetry

Compensatory growth with overgrowth –fractured side grows longer than normal side

Dysplastic growth- fractured side grows less than equal rate to normal side so that the difference in length is accentuated with time.

• Lund investigated condylar remodelling after fracture-

• Other authors have reported partial resorption and remodeling of the

condylar region.

Incomplete remodeling

Condyle was irregular

Displacement remained at fracture site

Complete remodeling

INFLUENCE OF CLEFT PALATE ON

MANDIBULAR GROWTH

• Mandibular growth in patients with cleft lip and/or cleft palate—the

influence of cleft type

• Conclusion:

The mandible in the cleft groups displayed shorter mandibular ramus and

body length.

Mandibular position relative to cranial base was similar in the cleft groups

with involvement of the palate.

Palatal clefts induce a significant downward and backward rotation of the

mandible associated with a more obtuse gonial angle.

Thus a small mandible is a structural characteristic of all cleft types

studied. However, mandibular shape and spatial position are strongly

influenced in clefts that involve the palate.

CONCLUSION

• “The human mandible has no one design for life. Rather, it adapts and remodels

through the seven stages of life, from the slim arbiter of things to come in the

infant, through a powerful dentate machine and even weapon in the full flesh of

maturity, to the pencil-thin, porcelain like problem that we struggle to repair in the

adversity of old age.”

D. E. Poswillo

REFERENCES

1. Essential of facial growth- Donald H. Enlow

2. Craniofacial Development- Geoffrey H. Sperber

3. Human anatomy for Dental students - B D Chaurasia

4. Shafers Oral Pathology

5. Current principles and techniques- Graber

6. Human Embryology- Inderbir Singh

7. Pertti Pirttiniemi et al (EJO-2009) - Abnormal mandibular growth and the

condylar cartilage.

REFERENCES

8. Growth of the mandible and biological characteristics of the mandibular

condylar cartilage, Japanese Dental Science Review (2013) 49, 139—150

9. Wolford L. Idiopathic condylar resorption of the temporomandibular joint

in teenage girls (cheerleaders syndrome) Proc (Bayl Univ Med Cent)

2001;14(3):246–252.

10. Pediatric oral and maxillofacial surgery

11. Effect on functional appliances on mandibular growth on skeletal Class Ⅱmalocclusion: A systematic review

12. Grey’s anatomy

13. Effect on functional appliances on mandibular growth on skeletal Class Ⅱmalocclusion: A systematic review

14. Mandibular growth in patients with cleft lip and/or cleft palate—the

influence of cleft type

QUESTIONS

• Describe the development and congenital anomalies of mandible-

20marks (may-2010)

• Define growth and development. Describe in detail pre and post natal

development of the mandible- 20 marks (april-2008)

• Describe the various theories of growth emphasizing on the growth of

mandible-20marks(march-2003)

THANK YOU