21 and 28: mandibular 1st PM Flashcards
occlusion - where is force/stress directed
down the long axis of tooth to protect tooth itself and the underlying structures
stamp vs shearing cusp
stamp = fxnal cusp (MAX LINGUAL)
shearing = non-fxnal
stamp cusps
functional
- max lingual
- mand buccal
shearing cusps
non fxnal
- mand lingual
- max buccal
when do 21-28 erupt
10-12 yo
bell shape tooth
mand 1st PM, 21/28
- cervical constriction
- flip tooth upside down to see bell
shark tooth
21 and 28 – buccal cusp way taller than lingual adn also buccal cusp tip is half way between B/L
occlusal view of 21 and 28
- diamond outline
- mesial outline narrower than distal, distal bulges out
- cusp tips mesial
- facial cusp slopes = half way B/L divider
F and L HOC on 21/28
mesial to center from occlusal view
21/28 proximal contacts
- -from occlusal view, in middle third, almost centered B/L
- -M contact is narrower than D
- -from buccal, you see that M contact is MORE CERVICAL than D, which is unique
why are 21/28 unique in terms of proximal contacts
M is more cervical than D
transverse ridge
on 21/28, unique -feature
- triangular ridge of facial adn lingual togetehr make the transverse ridge
- each ridge goes from cusp point down to center of occlusal table and there they meet to form one big groove
unique features of 21/28
- transverse ridge
- snake eyes
- ML devo groove
- shark tooth
- 45 tilted occ.table
ML devo groove
on 21/28, from M pit on occlusal surface to ML surface of crown adn even onto root
buccal view of 21/28
- UNIQUE proximal contacts, M is more cervical
- cusp tips M to center
- D slope longer
- CEJ getting flat
