growth of maxilla, mandible, soft tissue, and body (most
TRANSCRIPT
Growth of the Maxilla, Growth of the Maxilla, Mandible, Soft Tissue and BodyMandible, Soft Tissue and Body
Heekyoung Jo, D.D.S., M.S.Heekyoung Jo, D.D.S., M.S.
ORTD 323
Summer 2002
•General concepts of Growth•Growth Assessment•Bone formation and growth control•Growth of cranial complex
•General concepts of GrowthGeneral concepts of Growth•Growth Assessment•Bone formation and growth control•Growth of cranial complex
Growth and Development
• Terminology– Growth
– Development
• Pattern, Variability, and Timing
Pattern vs.. Variability• Normal growth patternex) Changes in overall body proportions
Cephalocaudal gradient of growth
Pattern vs. Variability
Scammon’s Curve
Pattern vs. VariabilityBoys GirlsGrowth Curves
Variability
• Racial and ethnic differences
• Gender
• Sickness
• nutrition
• Timing factor -Late/early maturers
• Problems with growth (hormones or genetics)
Timing Variation
• Early, average, and late matuerers
• Chronological age vs. Developmental age
•General concepts of Growth•Growth AssessmentGrowth Assessment•Bone formation and growth control•Growth of cranial complex
Why do we assess growth?
• To determine optimum time for treatment (growth modification and surgery)
• to determine the amount of growth left
• to determine type of growth
How to assess growth clinically
• Hand wrist x-ray
• sexual maturity: onset of menarche in girls, voice changes and facial hair in boys
• lateral cephalogram tracings: superimpositions
• Ask parents how much the child grew last year (height and shoe size)
• look at parent’s phenotype: tall or short
The Human Head ShapeBrachycephalic Dolichocephalic
•“Brachy” tends to grow horizontally; “Dolicho” tends to grow vertically.•Knowing the general pattern of growth and the expected direction can be helpful in orthodontic diagnosis and treatment planning.
Growth - cellular level
• Hypertrophy
• Hyperplasia
• Increased production of extracellular matrix
Hard Tissue Soft Tissue• Bone, teeth,
sometimes cartilage• Hyperplasia
hypertrophy mineralized ECM
• Interstitial growth, remodeling, endochondral
• Everything including some cartilage except bone and teeth
• Hyperplasia hypertrophy
• Interstitial growth
Soft Tissue Profile
convex straight concave
retrognathic orthognathic prognathic
Soft Tissue Changes with Growth
Boy growing normallyBlack - 10 yoRed - 14 yo
• Soft tissue profile tends to flatten with growth
• Nose and chin button growth at teenage years may change facial appearance
•General concepts of Growth•Growth Assessment•Bone formation and growth controlBone formation and growth control•Growth of cranial complex
Types of Bone formation
• Intramembranous– by secretion of bone matrix directly within C.T.
without any intermediate formation of cartilage– Through the activity of cells in the periosteum– Cranial vault, Mx & body of Md
• Endochondral – Cartilage is replaced by bone– Cranial base, Md condyle
Theories of Growth Control
• Determinants of the growth control– Bone– Cartilage– The soft tissue matrix in which the skeletal
elements are embedded - 60’s “Functional Matrix Theory” by Moss
• Level of control: Sites vs. Centers
Principles of Growth - Remodeling
• Resorption• Apposition
• Surface remodeling of a bone in the opposite direction to that in which it is being translated by growth of adjacent structures
•General concepts of Growth•Growth Assessment•Bone formation and growth control•Growth of cranial complexGrowth of cranial complex
Growth of the Craniofacial Complex
• Cranial Vault
• Cranial Base
• Maxilla (Nasomaxillary Complex)
• Mandible
Cranial Vault
• Intramembranous bone formation without cartilaginous precursor
• Apposition of new bones at the cranial sutures, periosteal activity(remodeling) due to the pressure from the growing brain
Cranial Base
• Mostly formed by endochondral ossification.• Bands of cartilage are formed between centers of
ossification called synchondrosis:– Spheno-occipital synchondrosis
– Inter-sphenoid synchondrosis
– Spheno-ethmoid synchondrosis
Cranial Base
• Cranial base grows by endochondral ossification that occurs at both margins of the synchondrosis.
Cranial Base
• Cranial base grows by endochondral ossification that occurs at both margins of the synchondrosis.
• Maxilla ( Nasomaxillary Complex)– Intramembranous ossification
• by apposition of bone at the sutures that connect the Mx to the cranium and cranial base
• by surface remodeling
• Mandible– Intramembranous and endochonral ossification
• The body grows longer by periosteal appposition of bone on its posterior surface
• The ramus grows higher by endochondral replacement at the condyle accompanied by surface remodeling
Maxilla • Remodeling of the palatal vault moves it in the same direction as it is being translated
• bone is removed from the floor of the nose and added to the roof of the mouth
•On the anterior surface, bone is removed, partially cancelling the forward translation. As the vault moves downward, the same process of bone remodeling also widens it.
Maxilla
• Growth of the surrounding soft tissues translates the maxilla downward and forward, opening spaces in the sutures where bone is added.
Maxilla
• Midpalatal suture is opened until teenage years.• Apposition of bone in the molar area accounts for
space for the third molars.
Mandible
• Remodeling is done by resorption in the anterior part of the ramus and deposition in the posterior part of the ramus
Mandible
• Overall growth direction results in a downward and forward displacement with most of growth occurring in the ramus.
Mandible
• Mandibular symphysis is closed by age of 1 year.• Late mandibular growth can occur in the late
teenage years or adulthood - most often seen in asians and males
When things go wrong
• Congenital craniofacial malformations: cleft lip/palate, syndromes (Apert, Crouzon, etc..), craniosynostosis
• Non-syndromic craniosynostosis
• Trauma
• Ankylosis
• Juvenile rheumatoid arthritis
When things go wrong
Trauma• Blow to one side of
the mandible may fracture the condylar process on the opposite side
• pull of the lateral pterygoid muscle distracts the condylar fragment including all the cartilage = resorption occurs