DENTAL ANATOMY 1 st Semester 20082009 Academic Year

DENTAL ANATOMY 1 st Semester 2008/2009 Academic Year Department of Stomatology School of Stomatology Wenzhou Medical College

Primary (and Mixed) Dentition Kevin Yang Li Hong-qing

SECTION 1 n Background Info. Objectives • Dental formulae • Functions of primary dentition

A definitions n Deciduous teeth • Deciduous: fall off n n Primary teeth Nicknames • Milk teeth • Temporary teeth

B Dental formulae n Primary teeth • I 2/2+C 1/1+M 2/2=5/5 n Permanent teeth • I 2/2+C 1/1+P 2/2+M 3/3=8/8

n Teeth numbering • A to T

n 1 D to 20 D

C functions n Mastication of food

n Support the cheeks and lips

n Speech formulation

n Maintaining the space and arch continuity

SECTION 2 Developmental Data n Objective • Time ranges for primary and secondary tooth eruption • Time ranges crown and root formation for primary and secondary teeth • Oder of eruption of primary and secondary teeth

A important times for tooth emergence n No teeth • Birth 6(or 8) months old: n Primary dentition only • 6(or 8) months-2(or 21/2)old: • 2(or 21/2)-6(or 53/4)years old:

n Mixed dentition • 6(or 53/4)years old: • 6 -9 years old: • 9 -12 years old: • 12 years old: n Adult dentition only • 17 -21 years old:

B crown and root development n General development • primary teeth: Lobes- crown calcifications- root formation, tooth eruption process- resorptionexfoliation • Succedaneous teeth: Lobes- crown calcifications- root formation, tooth eruption process

1. 2. 3. 4. 5. 6. Average primary crown calcification time? When does root formation begin? When does tooth start to erupt? How long does the eruption process last? Order of emergence of primary teeth? When do the primary tooth roots are completed? 7. What’s Mixed dentition? Age of mixed dentition? 8. Age of crown formation of 2 nd teeth? 9. Oder of emergence for 2 nd teeth? 10. 1 st and last emergence tooth of 2 nd teeth?

SECTION 3 Dentition traits of all primary teeth n Specimens • The best: in kids mouth • Or: plastic model

n General traits compared to secondary teeth • Smaller in size • Whiter • Marked constriction at cervix • Relative longer roots • Large pulp cavity, thin enamel and dentin layer • Less mineralized • More consistent shape

n Traits of all primary anterior teeth • Cervical ridges on facial surfaces are prominent • Lingual cingula are prominent • Labial surfaces are smooth

n Root traits of primary teeth • Long to the crown • Narrow mesiodistally • Roots bend labially

n Traits of primary posterior teeth • Prominent cervical ridge • Narrow occlusal table

• Buccal view: wide mesiodistally • Shallow occlusal anotomy

• Few grooves or depressions • Primary second molar larger than primary first molar

n Root traits of primary teeth • Root furcation near the crown, little or no trunk • Roots are thin or slender • Root number and relative size

SECTION 4 Class and Type Traits n n n Primary incisor traits canine traits molar traits

SECTION 5 pulp cavity n Anterior teeth • Large pulp cavity • Slight projection n Posterior teeth (molars) • Chamber Less elongated vertically • Pulp chamber in root crown • Long, narrow pulp horns