Development, form, and eruption

First evidence of tooth formation is

(When?)

Tooth germs in the 6th week in embryo

Tooth germs will form -

Tooth tissues (Primary and Permanent)

Calcification

Hardening of tooth tissues by deposition of minerals

Calcification occurs at

Tip of crown first, apex last

Developmental lobes are

Growth centers

Each tooth begins to develop from how many growth centers/ developmental lobes

Four or more

Coalescence

Fusion of developmental lobes

Developmental grooves

Lines of fusion for lobes

Mamelones

Incisal ridges seen with fusion of developmental lobes

Eruption

• normally no two teeth are visible in the mouth at birth

• No two people are alike in calcification or eruption schedules

• Diseases or illness can alter the formation of the teeth

All deciduous teeth develop by end of

6th month in embryo

Teeth that erupt first

Mandibular

Teeth erupt in

Pairs

Permanent teeth erupt earlier/later in girls

Earlier

(Always exceptions present)

Deciduous teeth expected to have erupted by

2.5 years of age

Normal for spaces to appear about age-

5

Eruption time (time span) and periods (start of the period)

Primary

6 months- 6 year

Eruption of primary mandibular central incisors

Eruption time (time span) and periods (start of the period)

Mixed

6 year- 12 year

Eruption of permanent mandibular 1st molar

Eruption time (time span) and periods (start of the period)

Permanent

12 years

Exfoliation of primary maxillary 2nd molars

Primary teeth eruption

Central incisors

6-8 months

Primary teeth eruption

Lateral incisors

10-9 months

Primary teeth eruption

First molars

14-13 months

Primary teeth eruption

Canines

17-16 months

Primary teeth eruption

Second molars

23-26 months

Importance of deciduous teeth

• normal jaw growth may not take place if deciduous teeth are lost prematurely

• They retain the proper spacing for the permanent teeth

• Guide 1st permanent molars into position directly behind 2nd deciduous molars

Permanent teeth eruption

Central incisors

6-7 years

Permanent teeth eruption

Lateral incisors

7-8 years

Permanent teeth eruption

Canine

9-11 years

Permanent teeth eruption

1st premolar

10-10 years

Permanent teeth eruption

2nd premolar

11-10.5 years

Permanent teeth eruption

1st molar

6-6.5 years

Permanent teeth eruption

2nd molar

11-12years

Permanent teeth eruption

3rd molar

17-22 years

Mesial drift

Drifting of permanent teeth in a mesial direction due to missing teeth

Mesial drift effect on deciduous teeth

Closes spaces between deciduous teeth

Premature loss of deciduous molars cause 1st permanent molars to erupt too mesial to their normal position

Eruption process

Exfoliation

Roots resorb, and tooth falls out

Eruption process

Resorption

Osteoclastic cells destroy root

Eruption process

Impacted

Not completely erupted, embedded in bone or soft tissue

Eruption process

Congenitally missing

Tooth bud/germ never formed

Usually 3rd molars and maxillary laterals

Eruption process

Attrition

Wearing away of tooth