Normal dental development, Tooth eruption and Interceptive ortho Flashcards
At birth what are the characteristics of the mouth?
- Gum pads
- Upper rounded
- Lower is U shaped
- Appear Class II
- AOB
What is the eruption pattern of deciduous teeth?
- Erupts from 6months to 2.5years
- a-b-d-c-e
- Lowers before uppers
What are the characteristics of deciduous dentition?
- Incisors more upright
- Spaced
- Wear
What is a natal/ neo-natal tooth?
- Abnormal dental development
- Lower incisors (most common natal tooth) present at, or just after birth
When should a natal/neo-natal tooth be extracted?
- If it is mobile and presents risk of inhalation
- Is causing difficulty breastfeeding
What are the processes of tooth eruption? x3
- Pre-eruptive phase
- Eruptive phase
- Post-eruptive phase
What is the pre-eruptive phase?
- Starts when crown starts to form
- Ends when crown formation complete/ root formation about to start
What is the eruptive phase?
- Starts when root starts to form
- Ends when teeth reach occlusal plane
- Split into Intra-osseous stage and Extra-osseous stage
What is the post-eruptive phase?
- Tooth movement/ eruption continues as root forms and throughout life in extremely small increments
- Movement after tooth has reached occlusal plane
What are the characteristics of Pre-eruptive phase? (Movement of crown)
- Developing crowns move constantly in jaw
- Small mesial and distal movement occur
- Developing crowns reposition themselves in response to increasing length, width and height of jaws
Where does the movement of tooth crowns occur in pre-eruptive phase?
- Contained within bony crypts
What does movement of tooth occur in response to during eruptive phase?
- Positional changes of neighbouring crowns
- Growth of mandible and maxilla
- Resorption of deciduous tooth roots
what would alter the relative position of deciduous and permanent teeth
- eruption of the deciduous teeth
- increase in height of the surrounding alveolar bone
What occurs during Intra-osseous eruptive phase?
- Root formation - starts with proliferation of HERS (Hertwig’s epithelial root sheath) and continues with production of dentine and pulp
- Movement of developing tooth - in occlusal or incisal direction (slow)
- REE Reduced enamel epithelium fuses with oral epithelium
What occurs during extra-osseous eruptive phase?
- Penetration of tooth’s crown tip through epithelial layers (fast 1-2weeks)
- Crown continues to move through mucosa in occlusal direction until contacts opposing tooth (slow several months)
- Environmental factors like muscles forces from cheeks, lips and tongue help determine final tooth position
What is the eruption pathway?
- Within dental follicle degeneration occurs
- Blood vessels decrease
- Nerve fibres break up into pieces
- This area is eruption pathway
What is the Gubernacular cord?
- Fibres from dental follicles formed in periphery of eruption pathway
- Theory is it guides teeth to erupt in oral cavity
What happens to the bone during Intra-osseous eruptive phase?
- Adjacent to and overlying, teeth bone loss keeps pace with occlusal movement of teeth
- Osteoclasts and osteoblasts constantly remodelling bone
Why does post-eruptive movement occur?
- In response to increases in height of growing alveolar bone and jaw
- In response to attrition and abrasion (due to occlusal wear compensation )
- In response to loss of opposing teeth (can cause over-eruption)
What does proximal surface tooth wear lead to?
- Mesial drift
Theories of tooth eruption
Multifactorial and likely combo of;
- Root formation
- Remodelling of alveolar bone
- Development of periodontal ligament (membrane)
- Genetics
What are the roles of dental follicle?
- Initiates resorption of bone overlying teeth
- Facilitates connective tissue degradation and creates eruption pathway
- Promote alveolar bone growth at base of tooth
- Provides traction forces within PDL
- Ectomesenchymal cells from dental follicle contribute to root formation