1. Primary Tooth Morphology Flashcards
Issues with primary eruption (4)
Gingival cysts (Epstein’s Pearls/Bohn’s Nodules)
Congenital Epulis
Natal/neonatal teeth
Eruption cysts
When do teeth start to form iul
5wks iul
When does hard tissue formation begin
13wks iul
Features of maxillary central primary incisor development (4)
Calcification begins 13-16wks iul
Crown complete 1.5mths after birth
Eruption 8-12mths
Root complete 33mths
Features of maxillary secondary primary molar development (4)
Hard tissue formation 16-23wks iul
Crown formation complete 11mths after birth
Eruption between 25-33mths
Root complete 47mths
Calcification of crowns at birth (6)
1/2 of primary central incisors 1/3 of primary lateral incisors Tip of primary canines 1/2 of primary first molar 1/3 of primary second molar Tip of cusps of first permanent molars
Reasons for primary dentition defects (3)
Hereditary
Difficult pregnancy
Complications at birth
Possible theories behind tooth eruption (4)
Cellular proliferation at apex of tooth
Localised change in BP/hydrostatic pressure
Metabolic activity within PDL
Resorption of overlying hard tissue
Why does resorption of overlying hard tissue (bone/tooth) occur
Due to enzymes in dental follicle (dark halo around unerupted tooth radiographically)
Function of dental follicle in active tooth eruption (2)
Follicle activated to initiate osteoclastic activity in the alveolar bone ahead of the tooth and clear a path for tooth eruption
Once crystal bone has been breached the follicle is likely to play a lesser role
General rules of primary teeth eruption (4)
Lowers before uppers
Sequence - a, b, d, c, e
Teeth of same series normally erupt within 3mths of contralateral tooth
Usually complete by 2.5/3yrs
Eruption dates of primary teeth (5)
Centrals (4-6mths) Laterals (7-16mths) First molar (13-19mths) Canine (16-22mths) Second molar (15-33mths)
Differences between primary and permanent central incisors
Primary smaller in both crown and root proportions
Differences between primary and permanent lateral incisors
Primary smaller in both crown and root proportions
Differences between primary and permanent canines
Primary smaller in both crown and root proportions
Differences between primary and permanent first molars (2)
Wider mesiodistally than permanent premolars
Primary crowns more bulbous
Differences between primary and permanent second molars
Primary crowns more bulbous
Differences between primary and permanent teeth (7)
Primary whiter in colour
Primary roots narrower, longer and slenderer, tend to flare apically
Large pulp chamber in relation to crown
Pulp horns extend high occlusally
Ribbon shaped root canals
Thinner coronal dentine layer
Relatively thin enamel of consistent depth
Definition of Leeway space (2)
Extra mesiodistal space occupied by the primary molars which are wider than the premolars which will replace them
Usually equates to 1.5mm per side on the upper arch and 2.5mm per side in the lower arch
Definition of anthropoid or primate space (2)
Spacing medial to upper deciduous canine
Spacing distal to lower deciduous canine
Features of mixed dentition stage (2)
Begins form the time of the first permanent tooth erupts until the exfoliation of the last primary tooth
Usually between 6 and 11yrs
Sequence of eruption of permanent teeth both arches (2)
6, 1, 2, 4, 5, 3, 7, 8
6, 1, 2, 3, 4, 5, 7, 8
Identifying primary central incisor (3)
Root may bend distally
Mesial edge of crown tends to be straighter (distal flare)
Lowers are smaller and more triangular labially
Identifying primary lateral incisor (2)
Distal flare on crown
Incisal edge of crown slants up distally
Identifying primary canine
Mesial edge tends to be straighter with distal flare soon after ACJ
Identifying primary first molar (5)
Unique – not like any other tooth
Prominent mesiobuccal tubercle (obvious palatally and mesially)
Upper more square, lower more rectangular
Straight-ish fissure pattern on uppers
Squashed S-shaped fissure pattern on lowers
Identifying primary second molar (5)
Prominent transverse ridge, running from the mesiobuccal cusp to the distopalatal cusp and two buccal
Lower second primary molars have three buccal cusps (like first permanent molar – smallest is the distobuccal)
Two buccal roots, one palatal root
C-shaped mesiobuccal fissure; straight distal fissure
Distopalatal cusp slightly separate due to transverse ridge
