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Growth & Development (Symposium (Impact of Obesity & Orofacial GD,…

- - - - Sequence of Eruption
        
        Centrals(6-7months)
        Laterals(7-8 months)
        1st Molars (12-15 months)
        Canines (18-20 months)
        2nd Molars (24-36 months)
        
        Eruption complete around age 3
      - Occlusal Feats
        
        Space primary Incisors
        
        critically important...
        
        Incisors erupt upright and spaced
        --> A lack of spacing suggests permanents successors will be crowded
        
        Incisor liability
        Difference between the space available and the space needed for the permanent incisors
        
        Well aligned teeth in deciduous will result in crowding in permanent dentition
        
        Primate Spaces
        
        mesial to canines in the upper arch
        
        distal to canines in the lower arch
        
        naturally occurring spaces in primary dentition
        
        Molar Terminal Planes
        
        Flush – suggests end-end (or Class I)
        
        Mesial Step – suggests to lead to Class I (or Class III)
        
        Distal Step – suggests Class II (or end-end)
        
        Final Molar relationship occurs as a result of
        
        Amount of mandibular growth
        
        Early mesial drift of 6s
      - First tooth erupts is deciduous lower central incisors (~6-7months)
      - A 'natal tooth' may be present at birth --> This should NOT BE EXO unless interferes with breast feeding or risk of inhalation
    - - Early (1st transitional)
        
        Eruption 6s and 1s & 2s
      - Middle (Inactive)
        
        Mixed dentition stage
        
        Disappear w/ eruption of 3s
        
        Ugly Duckling Phase Presents:
        
        Flared laterals (due to pressure exerted by upper canines on roots)
        
        Midline diastema, lower incisors crowding, spacing (if canine primaries lost)
      - Late (2nd Transitional)
        
        Eruption 3s, 4s, 5s and 7s
    - - Root calcification of permanent teeth is complete 2-3 years after eruption
      - eruption sequence of:
        - Maxillary = 6124537
        - Mandibular = 6123457
  - - - Ages 6
        
        Early Mixed - simultaneous eruption of 31/41, 36/46, & 16/26
      - Ages7
        
        Eruption of 11/21, 32,42
      - Ages 8
        
        Eruption of 12/22
        
        At this age there is 12 deciduous and 12 pernamnet teeth
        The buccal segments contain the C,D,E of primaries and permanent 6s, 1s & 2s
      - Ages 9/10
        
        Middle mixed - No teeth erupting
      - Age 11
        
        Late Mixed - Eruption of 33/43, 34/44 and 14/24
      - Ages 13/14
        
        Extend of completion of the roots of permanent teeth
      - Ages 15
        
        Permanent dentition stage - roots of all teeth complete, except 8s which crown is often complete
      - Age 12
        
        Late Mixed - eruption of 15/25, 13/23, 35/45
    - - Which teeth have erupted?
      - Amount of root resorption?
      - Amount of development of permanent teeth
  - - - Primaries more upright that permanents
        
        Labial positioning of the central and laterals
    - - Difference in width between primary and permanent teeth
      - Mandibular arch ~ 4.8mm
      - Maxillary arch ~1.6mm
    - - Permanents are palpable around age 9
      - Palatally impacted canines assoc w/:
        
        Small/peg laterals
        
        Missing lateral teeth
        
        Common in females
- - - - Branchial Arch 1 (early wk6)
        
        The frontonasal process (x1) --> nose, upper incisors, ant. Palate
        The secondary palate forms as secondary outgrowths from the maxillary process, which grow vertically down the side of the tongue (week 6)
        
        The maxillary processes (x2) --> post. palate, upper teeth & mx.
        Tongue drops and the palatal processes elevate and fuse (weeks 7-8)
        
        The mandibular processes (x2) --> mandible & lower teeth
        First part of the face to form and results from a merging of the medial ends of the mandibular processes (week 4)
        
        Palate fuses from anterior to posterior
        Failure of fusion results in cleft palate (females > males 2:1)
      - Endochondral Ossification
        = Bone replaces a cartilaginous precursor
        
        Bones form in response to load
        ex. Base of skull (synchondroses)
        
        Mesenchymal cells --> chondroblasts --> cartilage model --> apoptosis of chondrocytes --> replacement with bone
      - Intramembranous Ossification
        Bone forms directly on / within the FCT membranes
        
        These bones do not form in response to load (no cartilage model)
        ex. maxilla, frontal, parietal bones, mandible(except condyles)
        
        Mesenchymal cells condense and differentiate --> osteoprogenitor cells --> osteoblasts --> bone
      - (Cranial) Neural Crest Cells [NCCs]
        
        NCCs are Transient, migratory multipotent cells which give rise to
        the craniofacial bones, cartilage, nerves & connective tissue
    - - Growth movement defined as "bone drift" allowing bone to maintain its position during resorption and deposition
        
        There is a differential mode of enlargement in which some areas grow faster and to a greater extent than others (due to remodelling)
      - Primary Displacement
        A bone’s own increase in size leads to its own translation (displacement in space)
        
        Occurs both in mx and mdb
        nb: difference between the two
        Drift = growth movement due to remodeling
        Displacement = the growth movement of a whole bone as a unit
      - Secondary Displacement
        Translation of a bone occurs as a result of an increase in size of other bones around it
        
        movement of the maxilla occurs as a result of both its growth (1° displacement - maxilla) and that of the surrounding bones (2° displacement – cranial base)
      - V principal
        Bone deposited in the internal aspect
        Resorption on the outer aspect
    - - The vault bones are separated by loose CT that facilitate skull deformation at birth
        = Six fontanelles are present that close at (18 months)
        
        Premature closure of the sutures of the skull can result in craniosynostoses
        
        such as Crouzon or Apert’s syndromes
        
        The growth of cranial base influences the overall facial skeletal pattern and play an important role in determining how the mandible and the maxilla relate to each other
        
        (i) Low base angle assoc. w/ skeletal class III
        (ii) high base angle assoc. w/ skeletal class II
        
        Nasomaxillary Complex
        
        As the maxilla grows downward and forward, bone is removed from most of its anterior surface
        
        Bone is removed from the floor of the nose and is added to the roof of the mouth
        
        The widening of the vault occurs according to the “V” principle
  - - - = multidirectional proliferative capacity
        
        Endochondral ossification at articular contact
        
        Intramembranous ossification elsewhere
      - Condylar cartilage is a type of secondary cartilage
- - - - Ossification of the bones in hand/wrist in a predictable sequence to determine skeletal age
    - - Skeletal age is determined by the shape of the cervical (C2-C4) vertabrae
      - Each CVM bracket corresponds to a time around peak mandb growth
      - CS2 - Ideal to begin tx for Class III
        CS3 - Ideal to begin tx for Class II
      - C3 and C4 become progressively taller with time
        
        The lower border of C3-C4 become progressively more concave with time
        
        The concavity in C2 appears before the concavity in C3, which in turn appears before the concavity in C4
  - - - Rapid Growth Phase (age 3-7 months)
      - Decelerated/Constant (age 4-7 years)
      - Adolescent spurt (age 10-15)
- - - - Over the last century there have been a tendency for humans in developed countries to progressively larger @ all ages /cons
      - Secular trends reported in many dentofacial characteristics, for example tooth size, face size, severity of malocclusion
      - Main drivers are environmental variations