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Dr. Edward Angle
- -Malocclusion publiation 1890s
- -1st clear definition of normal occlusion
- -Upper 1st molars are the key
- -MB cusp of upper 1st molar occludes in buccal groove of lower 1st
Class I Malocclusion
Molars normal, but malposed teeth
Class II Malocclusion
Lower molar distally positioned relative to the upper
Lower molar mesially positioned relative to the upper
Types of tissue growth
- 1. Hypertrophy- increase in cell size
- 2. Hyperplasia- increase in cell number
- 3. Secretion of extracellular material- tissue mass increases
Name the three Interstitial growth characteristics
- 1. Occurs throughout the tissue
- 2. Ocurs in Soft tissues
- 3. occurs in uncalcified cartilage
Name the three Appositional growth characteristics
- 1. Occurs only on tissue surfaces
- 2. Occurs in hard tissues
- 3. Occurs in calcified tissues
Name three aspects of intramembranous growth (one type of ossification)
- 1. No structural precursor
- 2. Secretion of bone matrix directly within connective tissues
- 3. In cranial vault, maxilla, and mandible
Name three aspects of endochondral osseous growth
- 1. Cartilaginous precursor
- 2. Replacement of cartilage with centers of ossification
- 3. In axial and appendicular skeleton, cranial base
What is the chondrocranium like at 8 weeks?
- -The chondrocranium begins to develop, from the nasal capsule to the occipital region
- -Before ossification, chondrocranium can undergo interstitial growth. Afterwards, bone is only added by apposition
Which bones in the head arise from intramembranous ossification?
- The cranial vault, maxilla, and mandible arise from intramembranous ossification
- -additional bone can only be added by apposition
In which parts of bone can interstitial activity occur?
Interstitial activity for bone can only occur in the soft tissues of the periosteum
The mandible ossifies adjacent to which structure? What happens to the remnants of this structure?
- The mandible ossifies independently and adjacent to Meckel's cartilage.
- -remnants of Meckel's form two middle ear ossicles
- -Meckel's perichondrium becomes the sphenomandibular ligament
How does the condylar cartilage of the mandible develop?
- The condylar cartilage arises independently as secondary cartilage.
- -it is initially separated from the body of the mandible, and fuses during fetal life
- -increase in tissue mass at the condyle proceeds via the cartilaginous precursor, but additional bulk increase is appositional
Which types of ossification contribute to the origin of the mandible?
Both endochondral and intramembranous ossification contribute to the origin of the mandible.
What is remodeling?
- Remodeling is the balance of apposition and resorption
- -think of the sand dune relative to desert floor
What is relocation
Relocation is movement of a component part of boneas a result of remodeling
What is displacement/translation?
- Displacement/translation is the movement of a whole bone as a response to remodeling
- -think of the balloons moving away from each other
What makes the cranial base a unique tissue type?
- The cranial base is endochondral in origin
- -up to young adulthood, cartilage layer between each bone of the cranial base is preserved, allowing growth between the bones via a cartilaginous precursor
- -The cranial base bones increase in mass through ossification and proliferation of cartilage in the synchondroses
Does the maxilla have cartilage?
- No. All of its growth is in the sutures or the periosteum
- -in the sutures, there is apposition in an upward and backward direction.
- -this causes downward and forward displacement of the maxilla
What happens to the anterior maxilla during remodeling?
- Resorptive remodeling occurs on the anterior maxillary surface.
- -apposition occurs on the posterior surfaces, and resorption occurs anteriorly to prevent the maxilla from moving forward too far
What occurs during palatal remodeling?
- The palate remodels with apposition on the palatal surface and resorption on the nasal surface.
- -the result is a net downward translation
Summarize the 3 aspects of maxillary growth apposition
- 1.Apposition of bone at the sutures (downward/forward displacement)
- 2. Apposition of bone at maxillary tuberosity (increase arch depth)
- 3. Apposition of bone at the palatal surface (relocate palate downward)
What are the two sites of resorption of the maxilla?
- 1.Resorption at the anterior maxillary surface
- -maintains position of the anterior surface
- 2. Resorption of the nasal cavity floor
- -relocates the palate downward
What are the sites and characteristics of mandibular remodeling?
- 1. Large resorption on the anterior surface of the ramus
- 2. Apposition on the posterior surface of the ramus
- 3. Upward/backward increase in condylar mass through endochondral-like remodeling process
What happens to the mandible during remodeling?
The growth in mass in the mandible is predominantly upward and backward, but the mandible is displaced downward and forward due to the consistent articulation of the condyle with the glenoid fossa
Give a summary of the types of growth in the mandible
- 1. Endochondral bone growth at the condyle
- -displaces mandible downward and forward
- 2. Apposition at the posterior border, resorption of anterior border of ramus
- -relocates ramus posteriorly
- -displaces mandible downward and forward