Normal Development
Deciduous or Permanent?
Deciduous Permanent
Number of teeth 20 32
Dental Formula I 2/2, C 1/1, M 2/2 = 10 I 2/2, C 1/1, P 2/2, M 3/3 = 16
Size Smaller in all dimensions Large
Proportions Wider mesio-occlusally Larger cervical-occlusally
Colour Bluish-white Grey/yellow white
Time of eruption 6-24m 6y-24y
Time present in mouth 6m-12y 6y-rest of life
First to erupt Lower incisor L6
Primate Space Present Absent
Canines Slender, more conical Less conical
Cervical ridges More pronounced, esp on buccal Flatter
aspect of Ds
Occlusal plane Relatively flat Relatively curved contour
Molars Bulbous, sharply constricted Less constriction at neck. 1st
cervically. 2nd largest largest
Contact area between molars Broad Situated occlusally
Supplemental grooves More Less
Mamelons Absent On incisal edges of newly
erupted incisors
Neonatal line In all teeth Only in 6s
Pulp chamber Larger in relation to crown Smaller in relation to crown
Pulpal outline Follows DEJ more closely Follows DEJ less closely
Pulp horns Close to outer surface Comparatively away from outer
surface
Cellularity & vascularity More Less
Potential for repair High Low
Tooth structure protecting Less More
pulp
, Root canals Ribbon-like. Radicular pulp is Well-defined, less branching
thin, tortuous & branching
Floor of pulp chamber Porous. Accessory canals in Doesn’t have accessory canals
floor lead directly to radicular
furcation
Roots Longer & more slender. Shorter & bulbous. Broader
Narrower mesiodistally mesiodistally
Furcation More cervical - root trunk smaller Apical - root trunk larger
Roots of molars Flare outwards - space for No flaring
permanent tooth buds
Physiologic resorption of During shedding of primary teeth None
roots
Eruption Dates
Eruption Patterns
Mechanism of Eruption
● Teeth move from crypt → through alveolar bone → break ep integrity → erupt into oral cavity
Pre-eruptive Phase
● DF surrounded by bony crypt - loose CT sac, regulates alveolar bone activity
● Initiation of root formation stim DF → recruits growth/transcription factors & hormones req for
osteoclastogenesis & osteogenesis
Intraosseous Eruption
, ● Spatially restricted removal of bone on coronal side of tooth → creates eruption pathway
● Tooth moves in occlusal direction
● Bone apposition in apical follicle
● Bone formation increases DA process
● Speed of IO movement determined by genetic & local factors
- Local = crowding, disturbed bone remodelling (reduced oclast activity), obstacles (cysts),
trauma, early loss primary teeth
Mucosal Penetration
● As tooth approaches mucosa, REE + oral ep → ep plug
● Central cells degrade → ep canal for eruption
Junctional Epithelium
● Dentogingival junction = cells of oral ep + REE
● Transform to squamous mucosal cells w time
Supra-osseous Eruption
● Erupts at speed of 25-75 microns/d
● Active eruption stops once occlusal contact made
● Drift continues to occur via PDL remodelling
Eruption of Permanent Teeth
● Roots of deciduous teeth resorbed → shedding
● Directional pathway exists (Gubernacular canal) - widened by bone resorption during eruption
Eruption Sequence
Primary
Tooth Eruption Calcification Begins Enamel Complete
A 6-10m 4m iu 2m
B 8-12m 4.5m iu 3m
D 12-15m 5m iu 6m
C 18-20m 5m iu 9m
E 24-36m 6m iu 12m
Permanent
● Mx: 6, 1, 2, 4, 5, 3, 7
● Md: 6, 1, 2, 3, 4, 5, 7
, Root Development
● Primary complete 12m post-eruption
● Permanent complete 3y post-eruption
Normal Occlusal Features
Deciduous
Teething
● Erythema of surrounding gingivae
● Increased salivation & dribbling
● Systemic problems (irritability, mild fever)
● Tx: teething toys/gels
Spacing
● Growing → increased intercanine width
Permanent
● 6-7y: 6s usually erupt in ½ unit C2 relationship, guided by Es → growth of md, Leeway space &
eventual exfoliation of Es transition into C1
● 7-8y: LI TTB crowded at first - may improve w exfoliation of Cs & further growth. UI TTB mildly
crowded
● 8-9y: median diastema (ugly duckling) - proclined 2-2, convergence of roots prior to eruption of 3s
● Archform determined by: skeletal pattern, ST (tongue, lips, cheeks), dental (crowding),
environmental influences (tongue thrust, digit sucking)
Teeth Relationship
Canines
● C1 = U3 tip b/t L3 & L4
● C2 = U3 tip forward
