Unit 4b - Tooth Eruption Flashcards
What is eruption?
Process whereby developing Eruption begins at the time the crown is completed and the roots start to form and continues throughout the life of the tooth..
It is brought about in part by the lengthening root and the development of additional alveolar bone beneath the root.
During eruption, the apical end of the root is relatively fixed at the point where HERS invaginates and comes the epithelial diaphragm.
What is the PreEruptive Phase
The tooth germs are initially congested especially in the anterior, but with growth of the jaws the crowding is ‘usually’ alleviated.
The tooth germs move outward and toward the occlusal direction as the jaws increase in width, height and length.
The preeruptive movements all occur within the crypt before the development of the root begins.
The permanent teeth are beginning to develop in a position lingual to their predecessors.
Describe the prefunctional eruptive phase (active eruption)
In this stage the root sheath forms and proliferates apically and root formation begins.
There is vertical movement of the crown toward the oral eptihelium.
The inward curved edges of the bony crypt resorb via osteoclasts.
Constant remodelling surrounding individual teeth PLUS increase in height, width and length of arches.
As the teeth move toward the oral surface, the connective tissue between the OE and the REE is broken down and digested by the cells of the REE and other cells (macrophages).
Once the OE and REE come together, fusion takes place and the REE and OE now make the JE.
The blood supply is lost and central cells perish establishing an open pathway to the oral cavity.
Tooth crown is now in functional occlusion.
Describe what the tooth looks like at the prefucntional active eruption stage.
crown enamel is formed - secondary dentin begins.
Root is 2/3 formed (small amount of cementum.
Apical foramen is wide open.
Root dentin, cementum and PDL continue to form.
Alveolar bone continues to remodel and grow in all directions.
Describe functional eruptive phase
Once the teeth are in fucntion, there is a compensating increase in the height of the alveolar process as root completion continues.
Root completion takes about 1-1.5 years in deciduous teeth and 2-3 years in permanent teeth.
The mineral density of bone increases, the principle fivers increase in dimension and organize into groups, blood vessels also become more highly organized.
The tooth will erupt further to maintain occlusal contact by depositing more cementum at its apex.
Describe passive eruption
This is given to the process of gingival recession and how with it, more tooth becomes exposed to the oral cavity.
The movement here is with the gingival tissue and not the tooth itself. Although it is likely accompanied by functional eruption.
Describe mesial drift
This phenomenon is the bodily movement of the erupting permanent teeth toward the midline.
Partially due to the flattening out of the contact areas as well as the pressure from mastication.
Describe exfoliation
To shed or eliminate something from the surface of the body, as in the loss of teeth from the jaws.
Gradual process of resorption of the roots and PDL structure.
the developing permanent teeth create pressure to produce resorption of the primary roots and the bone surrounding the roots.
Performed primarily by the odontoclast cell (similar to marcrophage, but tooth related)
Describe the pattern of exfoliation
Depends on the position of successional tooth in relation to the primary.
Primary tooth resorption show a resorptive pattern lingually where the posterior teeth show pattern interradicularily.
General rules *pattern of eruption
-symmetrical
-mand prior to max except …
-2nd molars simultaneous
-Female before male
What are some of the mechanisms responsible for tooth eruption?
- root growth is accommodated by occlusal crown movement.Root growth does occur simultaneous with eruption, but when eruption is halted (in vitro) root growth continues.
- Selective deposition and resorption of bone around the tooth. Bone remodelling can and does occur during eruption. Folicular cells may have more influence on development of an erution pathway (resorption) which enables eruption.
- cells and fibers of the PDL-cells of the dental follicle have been noted to have contractile properties of PDL fivers (and fibroblasts) have been shown to have tractional forces that may assist in eruption.
What is the eruption sequence and movements?
- anteriors move toward incisal
- premolars move horizontal due to jaw growth
- 1st molars erupt where they develop
- 2nd and 3rd molars must rotate and move forward
- max 3rd molars develop in tuberosity with occlusals distal and buccal
- mand 3rd molars develop in ramus with occlusals directed mesially
What are some abnormalities in eruption and exfoliation?
-lingual eruption of perm teeth (tongue and lips eventually press into position)
-impactions (cannot erupt)
congenitally missing (partial anodontia)
-imbalance between tooth development and jaw growth (small jaw - large teeth)
-delayed eruption (genetic, systemic - nutritional deficiencies; or local etiologies) (ankylosis, premature loss = locked in, eruption cysts, impaction….)
Describe the development of occlusion
it is essentially a continuation of the eruption process and is a very complex process
- further growth of roots, jaw/alveolar bone etc.
- many factors influence the final position of teeth in arches
What are some environmental factors that influence occlusion?
- muscle forces (tongue, cheeks)
- contact of erupting teeth with other erupting teeth
- habits (thumb sucking)
What are some eruption factors that influence occlusion?
- eruption pattern and timing/allows permanent teeth to move into key positions
- facial and individual tooth development and growth
- sequence of tooth bud formation
