5. post-natal growth

8/3/2019 5. Post-Natal Growth

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Dr. Munizeh Khan

S.R Orthodontics



Cranial vault

Cranial base

Nasomaxillary complex

Mandible



a) Function:

Protection of the brain

b) Growth:1) Mechanisms & sites:

Sutures

Surface remodeling

2) Timing:

Paced by brain growth



a) Functions:

Protection & support of brain and spinal cord

Articulation of skull with vertebrae, mandible & maxilla

b) Growth:

1) Mechanisms & Sites:

Sutural growth

Elongation at synchondroses

Extensive cortical drift & remodeling (ectocranial)



Combination provides:

Differential growth between calvaria & cranial base

Expansion of endocranial fossae

Maintenance of passages and housing for vessels andnerves (foramina)

Clinical Significance:

Spheno-occipital complex anterior displacement of midface

Fwd displacement of mandible ramus growth



Timing:

Paced with brain growth

Synchondroses:• Intra-sphenoidal = after birth

• Intra-occipital = 3-5 yrs

• Spheno-ethmoidal = 6-7years

• Spheno-occipital = 13 years



a) Functions:

Mastication, Respiration

Encloses the eyes

b) Growth:

1) Sites:

Sutures

Nasal septum

Alveolar process

Periosteal & endosteal surfaces



2) Mechanisms: Passive Displacement

Growth of cranial base Important up to age 7yrs 1/3rd of total maxillary forward movement

Active Growth Sutural growth Cortical drift Surface remodeling

Anterior surface resorptive Posterior surface depository

Direction: downward and forward



3) Amounts & Directions:

Maxillary Height: Sutural growth towards frontal & zygomatic bones

Appositional growth in the alveolar process (40%)

Orbits

Hard palate



• Maxillary Length:

– Apposition on maxillary tuberosity

– Anterior region is resorptive

– Posterior region is depository

• Maxillary Width:

– Midpalatal suture – Vertical growth of alveolar process (divergence)



Timing:

Alveolar process eruption of teeth

Roughly coincident with general body growth

Coincides with CVM 2-3 stages

Compensatory Mechanisms:

alveolar process



a) Functions:

Mastication, airway, speech & facial expression

Type of growth:

Slender, U-shaped bone

“Bent”long bone:

endochondral = ends

intramembranous = in between



b) Mechanisms & Sites:

1) Condylar cartilage:

CONTROVERSY: Growth site or center?? Secondary cartilage

Grows in face of pressure

Experiments:

No condyle but normal function

Transplanted alone = no growth

Transplanted with functional forces = growth



THUS:

Condyle is dependant on articular function

Articular function is dependant on how mandible grows

Mandibular growth is dependant on factors outside themandible, i.e. Maxillary growth, soft tissue matrix

CONDYLE:

Important growth SITE

Aids in translation of mandible (AP growth) Highly responsive to functional forces

Reacts faster to lower threshold forces



Displacement

1st!!!!

Adaptive

2nd!!!!

Primary Displacement of

Mandible



++

+

++

+

+

+

+

+

+

-

-

-

---

-

-

-

Posterior Relocation of Ramus

As a result of cortical drift



3) Corpus:

Moves in conjunction/in response to maxilla

Displaced downward and forward

Areas of Muscle attachments:

Encourage cortical drift and local remodeling

Coronoid process & gonial angle

Areas with deficient/abnormal muscle function

under-developed



4) Alveolar Process:

Formation controlled by dental eruption

Serve as important buffer zones

Help to maintain occlusal relationships duringdifferential midface & mandibular growth



c) Amounts & Directions: Height:

Ramus growth

Alveolar process• Dental eruption

• Anterior mandibular height

Width: Symphyseal cartilage plays no major role

V-principle of growth

Length increase + natural divergence of mandible



Sequence in which growth is completed in both jaws:

Width

Mostly over before puberty

Length Continues through puberty

Height

Continues post-puberty



Hemifacial Microsomia



Confusing!!

Simplified by Proffit



Proffit : simplified terminology

– Internal rotation:

– Rotation of mandibular core relative to cranial base

– External rotation:

– Rotation of mandibular plane relative to core of mandible

– Total rotation:

– Rotation of mandibular plane relative to cranial base

– Equals internal rotation – external rotation



Internal rotation:

Rotation of mandibular core relative to cranial base

Has 2 components:

Matrix rotation= around the condyle

Intra-matrix rotation = centered within mandibular body

Matrix rotation Intra-matrix rotation



External rotation:

Rotation of mandibular plane relative to core of mandible

Surface changes:

Posterior part of lower border of Md: resorption

Anterior part: unchanged or slight apposition



* Anterior rotation: * Posterior rotation:¬ Forward, counter-clockwise ¬ Backward, clockwise

¬ Negative sign (-) ¬ Positive sign (+)

Internal rotation = -15o

25% from matrix rotation, 75% from intra-matrix rotation

External rotation = + 11 to 12o

Total rotation= Internal – External

= -15 – (+ 11/12)

= -3

o

or 4

o



Therefore:

• 15 degrees : forward rotation

• 11 to 12 degrees: backward rotation

• Net result: 3 to 4 degrees forward rotation



Maxillary core less defined

Internal rotation:

No matrix rotation (no condyle)

Intra-matrix rotation present

External rotation:

Resorption on nasal floor, deposition on palatal side

Total rotation:

Equal and opposite internal and external rotations

= zero degree change in jaw orientation



Variation in face types:

Normal angle High angle Low angle

(long face) (short face)



After summer break = conclude growthsection

Test on growth (September 2010)

Moyers

Proffit Any other text you may like to add



Enjoy your summer vacations!

Stay safe and see you soon inshAllah!

5. post-natal growth

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