Lecture 7: Eruption and Shedding Flashcards
physiologically, a tooth will move in all directions, except ____, to attain and maintain its position in the jaw. also, normal tooth movement occurs _____ ____
- apically
- throughout life
the movements of eruption are a cellular activity involving different cell types of the PERIODONTAL LIGAMENT including: (4 things)
- cementoblasts
- osteoblasts
- osteoCLASTS
- fibroblasts (most numerous cell type of the PDL)
what are the functions of a fibroblast in the PDL?
- secretes extracellular fluid (fibroblasts)
- lysis the extracellular substance (fibroclasts)
- may become a contraction cell called a FIBROMYOCYTE fibroblast (connected to collagen fiber bundles that connect the tooth to alveolar bone)
what are the three stages of eruption?
- preemergence (moves FACIALLY)
- prefunctional (moves OCCLUSALLY)[wants to get to oral cavity]
- functional (moves mesially)
the PREEMERGENCE stage starts with the appearance of ______ and continues to the appearance of the _______ and ______ just prior to the start of root dentin formation
- dental lamina
- reduced enamel epithelium
- hertwig’s root sheath (# of canals determined at this stage & root dentin outline)
*mainly moves facially
hertwigs root sheath determines the number of root canals in the _____ stage before the start of ______
- preemergence stage
- root dentin formation
when does hertwigs root sheath determine the root dentin outline?
at the start of root dentin formation
what are some of the major events that happen during the preemergence stage
- differentiation of ameloblasts, odontoblasts, and fibroblasts (NOT CEMENTOBLASTS)
- appearance of CROWN dentin and enamel
- DEJ forms and pulp chamber form
- REE (attached by basal lamina to surface)
- # root canals and HERS
the prefunctional stage of eruption starts with ____ and ends when ____
- root dentin formation
- tooth reaches occlusal plane
*mainly moves occlusally
during the PREFUNCTIONAL stage, when does the HERS break up?
when the root dentin forms and cementum forms of the exposed dentin
- sequence continues apically until root dentin is completed
- sheath diagram stage and the elongation of the sheath have already happened
these appear during the PREFUNCTIONAL stage and are remnants of epithelial cells from hertwigs root sheath in the periodontal ligament
epithelial rest of malassez
how does emergence happen in the pre functional stage?
the merged oral epithelium and the reduced enamel epithelium undergo cell death and the most coronal part of the crown emerges into the oral cavity
*when the tooth enters the oral cavity, the reduced enamel epithelium becomes the JUNCTIONAL EPITHELIUM
what anchors the junctional epithelium to both the tooth surface and the connective tissue of the free gingiva
basal lamina (it is on BOTH sides of the junctional epithelium)
the functional stage of eruption starts at _____ and physiologically continues _____
- the occlusal place
- throughout life
*mainly moves mesially
during the functional stage, the position of the junctional epithelium changes from what three places?
- attached to enamel
- attached to enamel and cementum
- attached to cementum
