5. Post-Natal Growth
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Transcript of 5. Post-Natal Growth
8/3/2019 5. Post-Natal Growth
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Dr. Munizeh Khan
S.R Orthodontics
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Cranial vault
Cranial base
Nasomaxillary complex
Mandible
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a) Function:
Protection of the brain
b) Growth:1) Mechanisms & sites:
Sutures
Surface remodeling
2) Timing:
Paced by brain growth
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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)
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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
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Timing:
Paced with brain growth
Synchondroses:• Intra-sphenoidal = after birth
• Intra-occipital = 3-5 yrs
• Spheno-ethmoidal = 6-7years
• Spheno-occipital = 13 years
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a) Functions:
Mastication, Respiration
Encloses the eyes
b) Growth:
1) Sites:
Sutures
Nasal septum
Alveolar process
Periosteal & endosteal surfaces
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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
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3) Amounts & Directions:
Maxillary Height: Sutural growth towards frontal & zygomatic bones
Appositional growth in the alveolar process (40%)
Orbits
Hard palate
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• Maxillary Length:
– Apposition on maxillary tuberosity
– Anterior region is resorptive
– Posterior region is depository
• Maxillary Width:
– Midpalatal suture – Vertical growth of alveolar process (divergence)
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Timing:
Alveolar process eruption of teeth
Roughly coincident with general body growth
Coincides with CVM 2-3 stages
Compensatory Mechanisms:
alveolar process
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a) Functions:
Mastication, airway, speech & facial expression
Type of growth:
Slender, U-shaped bone
“Bent”long bone:
endochondral = ends
intramembranous = in between
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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
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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
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Displacement
1st!!!!
Adaptive
2nd!!!!
Primary Displacement of
Mandible
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Posterior Relocation of Ramus
As a result of cortical drift
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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
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4) Alveolar Process:
Formation controlled by dental eruption
Serve as important buffer zones
Help to maintain occlusal relationships duringdifferential midface & mandibular growth
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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
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Sequence in which growth is completed in both jaws:
Width
Mostly over before puberty
Length Continues through puberty
Height
Continues post-puberty
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Hemifacial Microsomia
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Confusing!!
Simplified by Proffit
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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
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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
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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
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* 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
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Therefore:
• 15 degrees : forward rotation
• 11 to 12 degrees: backward rotation
• Net result: 3 to 4 degrees forward rotation
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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
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Variation in face types:
Normal angle High angle Low angle
(long face) (short face)
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After summer break = conclude growthsection
Test on growth (September 2010)
Moyers
Proffit Any other text you may like to add
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Enjoy your summer vacations!
Stay safe and see you soon inshAllah!