chapter 6: eruption and shedding of teeth

(no development)

diphyodont

having 2 dentitions

when will a teeth stop erupting?

until something physically stops them

or until a tooth is lost 

eruption is active or passive

preeruptive phase

begins with tooth initiation, ends when the crown is complete and root formation starts

teeth shift in position in the jaws as they grow and develop

permanent teeth develop lingual to primary teeth at the same level

after primary teeth erupt:

• permanent posteriors move within the roots of primary teeth

• permanent anteriors shift to a lingual position near the apical third

active eruption

starts with root formation and ends at occlusal contact

four main events: root formation, movement, penetration, and occlusal movement

after enamel is complete, ameloblasts form an acellular dental cuticle, and the enamel organ flattens into the reduced enamel epithelium (REE)

REE fuses with oral epithelium; enzymes dissolve the center, forming an epithelial tunnel (appears as an inverted triangle) for the tooth to erupt in the mouth

prefunctional eruption

the top part of the fused tissue pulls away from the crown, while the bottom part stays attached around the neck of the tooth (attached remains are the PEJ)

tissue changes during eruption 

the dental follicle creates a pathway for the erupting tooth

macrophages break down connective tissue, cells, and nerve fibers above the erupting tooth

blood vessels in the area decrease

gubernaculum dentis fibers may guide the tooth’s eruption path

osteoclasts remove bone for eruption, while osteoblasts form new bone where needed

initial junctional epithelium of the tooth

fused tissue that remains near the CEJ after eruption

what replaces the initial junctional epithelium as the root is formed

definitive junctional epithelium

principle fiber development

fiber bundles form around the developing root

fibroblasts can both create and break down collagen fibers (acting as fibroclasts)

once the tooth fully erupts, the fibers become permanently positioned

teeth lost prematurely need something to maintain the space or ____ can occur

drifting and/or supereruption (tooth grows more out of socket)

ankylosis

condition in which the cementum of the tooth fuses with the alveolar bone proper surrounding the alveolus (jawbone)

further eruption of the tooth is prevented

passive eruption

begins after the teeth are functioning and continues as long as they’re present

roots of primary teeth take 1-1.5 years to fully develop

roots of permanent teeth take 2-3 years to fully develop

posteruptive

occurs from functional contact until the tooth is lost

alveolar bone grows in height and density

root canal becomes narrower

apical fibers grow, enlarge, and reorient as they mature

attrition or abrasion may cause slight continued eruption, with cementum added to maintain tooth position

possible causes of tooth eruption

root growth

pulpal pressure

cell proliferation

increased vascularity

increased bone formation around teeth

endocrine influence

enzymatic degradation

6/4 rule for primary tooth emergence

from birth, 4 teeth emerge for each 6 months of age 

(timing is not as important as sequence)

exfoliation of primary teeth

osteoclasts- absorb alveolar bone between the primary and developing permanent tooth

odontoblasts and cementoblasts- resorb the root and parts of the crown of primary tooth

(occurs at the same time)

how do permanent maxillary incisors move as they erupt?

a more facial position

T or F: process of eruption for a succedaneous tooth is not the same as for the primary tooth

F, the eruption is the same

root resorption and pulp degeneration

primary tooth pulp is highly cellular during root formation

during root resorption, the pulp loses cells and nerve fibers, and fibrosis develops

blood vessels remain until the tooth is exfoliated

periodontal support is similar in primary and permanent teeth

common variations in eruption of permanent teeth

unilateral eruption

maxillary premolars erupt before canines, causing canines to erupt more labially

mandibular 2nd molars come before premolars, causing it to invade the premolar’s spot

incisor liability

the space problem that occurs when bigger permanent front teeth replace smaller baby front teeth

leeway space

extra space left when primary molars are replaced by smaller permanent premolars

nasmyth’s membrane

a thin layer that can occur on newly erupted teeth (both baby and permanent)

made of leftover tissue from REE, oral epithelium, dental cuticle

soft and sticky, so it stains easily from food and drinks

why are sports guards important for active children?

to prevent traumatic injury to the permanent teeth before they’re fully anchored to the jaws

why is it important to remove a loose primary tooth within 2 weeks/ASAP?

if a loose tooth is not taken out, the gums will swell up and reattach the tooth to gum tissue to try and reabsorb the crown (makes it super painful to pull out)