Chapter 6-2 Tooth development and Eruption Flashcards
When does root development begin
After crown is completely formed and tooth begins to erupt
What structure is responsible for root development
Cervical loop
What is the cervical loop consists of
Inner enamel epithelium and outer enamel epithelium
What is the Hertwig Epithelial Root Sheath (HERS)
Elongated cervical loop that encloses dental papilla tissue
What is te HERS responsible for
Shaping roots by inducing dentin formation of root area
Outer dental papilla cells undergo what processes (2) to become what?
Undergo induction and differentiation to become odontoblasts
What does HERS induce?
Odontoblastic differentation
Odontoblasts undergo what to do what?
Undergoes dentinogenesis to begin secreting predentin
When root dentin formation is complete what occurs?
Basement membrane disintgetration
HERS disintegration
Rise of ERM from HERS
What is Epithelial rests of Malassez (ERM)
Cells that form from disintegrated HERS cells
What do ERM cells end up in?
Periodontal ligament (PDL)
Order of layer formation
Dentin, cementum, Pulp
Cementum formation begins with?
Cementoblasts undergoing cementogenesis which causes appositional growth of cementum in tooth area when HERS disintegrates
Explain the process of cementogenesis
Lays down cementum matrix or cementoid
What happens to cementoblasts during cementum formation
Become trapped in the cementum they produce
Dentinocemental junction (DCJ) occurs as a result of what?
Apposition of cementum over dentin
What cells form the pulp?
Central cells of dental papilla
What structure causes teeth to develop multiple roots?
Differential growth of HERS
What determines the number of roots the mature tooth will have?
Number of extensions of the cervical loop
Ectomesenchyme from dental sac begins to form what two structures?
Periodontal ligament (PDL) and tooth sockets
What is Sharpey’s Fibers
Mineralized ends of PDL; portion that is inserted into the cementum and alveolar process (bone)
Define Eruption
Vertical movement of tooth eruption
After enamel growth ceases in crown of tooth what occurs?
Ameloblasts place acellular dental cuticle on newly formed outer enamel surface
During tooth shedding, what occurs to the layers of enamel organ
The enamel organ condenses into one layer called Reduced Enamel Epithelium (REE)
What occurs after REE forms?
Tooth begins eruption into oral cavity
Describes the steps of eruption process (2)
- REE fuses with oral epithelium
- Enzymes of REE disintegrate central part of the fused tissue - forming the Gubernacular canal
What is the Gubernacular Canal?
Protective epithelial-lined eruption tunnel where the tooth erupts through
What is the initial junctional epithelium and what does it do?
Fused tissue near the CEJ; creates seal between the tissue and tooth surface
What is the initial junction epithelium later replaced by?
Definitive junctional epithelium
In what direction do succedaneous permanent teeth develop?
Lingually to primary teeth except permanent maxillary incisors which develop facially
What are osteoclasts
absorb alveolar process
What are odontoclasts
tooth root resorption; removal of dentin and cementum
What is the nasmyth membrane
Green gray residue formed on newly erupted teeth; consists of fused tissue of the REE and oral epithelium
