growth and development: skeletal and dental

lecture given 10/2/2026

what are the growth concepts?

pattern- repetition, implies predictability, things happen in order

variability- there will always be variations of normal, important to differentiate from those outside of normal

timing- same event for growth happens at different times for different people, variations in timing are most obvious during adolescence, chronological age vs biological/developmental age

craniocaudal growth

humans grow from top down

the skull also grows from top down

what is the order that growth finishes in?

transverse (breadth)

anterior-posterior (depth)

vertical (can continue into the 3rd decade of life)

intramembranous ossification

transformation of mesenchyme and deposition of bone on surfaces (no cartilage model)

endochondral ossification

ossification of a cartilage model

mixed bone formation

intramembranous AND endochrondral

cranial vault

intramembranous

starts forming at 7-8 weeks gestation

cranial vault is disproportionate to body at birth

rapid growth occurs during the first 24 months after birth

by ____ yrs old, the brain and cranial vault will achieve 80% of adult size

4

by ____ yrs old, the brain and cranial vault will achieve 95% of adult size

10

cranial base

endochrondral

first parts start forming at ~6 weeks in utero

as ossification continues, bands of cartilage remain between bones (synchondroses)

synchondroses

growth center

bipolar- like back to back growth plates

when does the intersphenoid synchrondrosis fuse?

birth

when does the spheno-ethmoidal synchrondrosis fuse?

7 yrs old

when does the spheno-occipital synchrondrosis fuse?

15 yrs old, ossifies by age 20

growth center

pre-determined genetic influence

independent growth

epiphyseal plates and synchrondroses

growth site

secondary or compensatory for growth

location of growth (no independent growth, they react to pressure/tension)

all growth ____ are also growth _____

not all growth _____ are _____

centers, sites

sites, centers

growth of the maxilla

entirely intramembranous ossification

down and forward

bone added at maxillary tuberosity (major growth SITE of maxilla)

growth at midpalatal suture until puberty

resorption occurs superior and anterior

growth of the mandible

mixed endochrondral and intramembranous ossification

apposition at condyle and posterior ramus

resorption at anterior ramus

condyle is the primary growth SITE (up and back)

scammon’s curve

graphic representation for differential growth

tells us that each tissue grows at a different rate

growth of neural tissue done by age 6 or 7

general growth (muscles, bone, viscera) slow during childhood and accelerates at puberty

the mandible follows which growth curve on scammon’s curve?

general growth

chronological age

years from birth

dental age

based on teeth present

in general, you should be treating pts based on their ______ age

dental

what factors affect development?

genetics- dental calcification / eruption sequence

nutrition- malnutrition can affect size, proportion, quality, and texture

chronic illness- major illnesses can affect tooth development, psychological/emotional stress in extreme cases can present like chronic illness

race- differences in tooth eruption and calcification

socioeconomic status- multifactorial effect on development

primary dentition

starts to develop at 1.5 mo in utero

calcification begins at 4 mo in utero

primary eruption usually begins at 6 mo, eruption dates are variable

eruption sequence is usually preserved

primary dentition is erupted by 24-30 mo

how do teeth develop?

chronologically from crown to root

how are teeth numbered ortho style?

adult dentition: centrals are 1, laterals are 2, so on and on

primary dentition: centrals are a, laterals are b, so on and on and on

what is the eruption sequence for primary teeth (ortho style)?

A B D C E

where is primate spacing?

max: btwn laterals and canines

mand: btwn canines and first molars

leeway space

the difference in mesiodistal diameter of deciduous C D E and their permanent successors 3 4 5

how much leeway space is in the maxilla?

1.5mm per side, 3mm total

how much leeway space is in the mandible?

2.5mm per side, 5mm total

why is leeway space important?

crowding- most common feature of dental arch malocclusion

bc of crowding in early mixed/mixed dentition with proper space maintenance can help prevent need for future extractions

space in mandible can also help convert flush terminal plane to class I

what are the options for distal step after growth?

minimal growth- class II

forward growth of mandible- end to end

almost always angle class II

what are the options for mesial step after growth?

minimal growth- class I

forward growth of mandible- class III

80% with mesial step <2mm become angle class I

if mesial step >2mm, become class III

what are the options for flush terminal plane after growth?

minimal growth- end to end

forward growth of mandible- class I

56% become angle class I

44% become angle class II

how does intercanine distance change?

max- increases

mand- no change

how does intermolar width change?

both progressively increase in childhood and adolescence

how does arch depth change? (aka distance from incisors to first molars)

both decrease

how does arch perimeter change?

increases during early mixed, decreases during late mixed

max- slight overall increase age 5-18

mand- overall decrease

what is the most frequent eruption sequence for max permanent teeth?

6 1 2 4 5 3 7

what is the most frequent eruption sequence for mand permanent teeth?

6 1 2 3 4 5 7

early mesial shift

eruption of permanent first molars

late mesial shift

exfoliation of primary second molars

what timing eruptions did dr. pan say we should probably know?

6 yr first molars

12 yr second molars

canine between 9 to 11 for girls, 11 to 13 for boys

__% of pts using a LLHA will prevent the need for extractions in later stage

73

generalized spacing in the primary dentition is ______

a good thing!

ugly duckling stage

from ~7-9 yrs old

spacing, flared laterals, no canines

mesial eruption force of permanent canines will consolidate anterior spacing

what teeth are important to preserve space after? (weird way to word the question)

gross caries on primary teeth requiring extraction

early loss of primary second molar before 6 yo

premature loss of ONE primary canine

extracting a primary tooth too early can…

delay the eruption of succedaneous tooth, worsen crowding issues

what are possible reasons for over-retained teeth?

locked in, ankylosed, missing permanent dentition

ectopic eruptions

#1 most frequent- max first perm molars

management depends on tooth position and location/extent of resorption

A?

observe eruption 3-6 mo

B?

observe eruption 3 to 6 mo

C?

separation

D?

observe eruption

E?

unilateral appliance

F?

monitor for early exfoliation and space maintenance

G?

extract E, regain space, then space maintenance

H?

bilateral appliance

I?

monitor for early exfoliation and space maintenance