premolars Flashcards
secondary dentiion
at what age do maxillary and mandibular first premolars erupt?
max and mandibular premolars erupt together for the same tooth type
10-11
1.
at what age do mx and mn second premolars erupt?
what’s so special about this age?
11-12
maxillary canines erupt at this age range too
fdi notation of first premolars
14, 24, 34, 44
universal number of first premolars
5, 12, 21, 28
universal number of second premolars
4,13, 20, 29
fdi notation of second premolars
15,25, 35, 45
dimensions
what’s so special abt md of mn 2nd premolar?
root length > crown length
facial and lingual root length of the mx first pm is identical
OC > MD
FL > OC in maxillary premolars
FL< OC in mn first premolar FL = IC in mn second premolar
FL>MD in all premolars thicker than wide
mn second premolar: lingual MD > facial MD
Crown outline forms
facial, mesial and distal
facial: pentagonal
m/d: trapezoidal for mx, rhomboidal for mn
**rhomboidal mn first premolar has substantial lingual tilt **
crown outline form
occlusal view
mx first pm: hexagonal
mn second pm: ovoid
mn first pm: diamond/rhomboidal
mn second pm: square
facial view
mx cusp ridges
mx first pm: mesial cusp ridge > and straighter than distal cr w 100-120 deg angle
mx second pm: distal cusp ridge > mesial cusp ridge w 125-130 angle
mn cusp ridges
mn first premolar: distal cr > mesial cr different from mx first pm w 100-120 deg angle same as mx first pm
mn second pm: 130 deg angle same as mx second pm
mx first pm cusp tip
offset slightly distal
mn first pm cusp tip
facial cusp relatively sharp offset slightly to mesial
sharpness of mn second pm
relatively blunt
facial view
mesial and distal prox contacts of mx pm
mx first and second pm mc: junction of occlusal and middle third
mx first and second pm dc: middle third
facial view
mesial and distal prox contacts location of mn premolars
mn first pm mc and dc: middle third
mn second pm mc and dc: jkunction of occlusal and middle third
facial view
cervical line form
evenly convex towards apex in mx premolars
evenly curved and slightly convex in mn first pm
evenly curved, less convex in mn second pm
which 2 premolars have well developed and relatively prominent buccal (facial) ridges?
how is the facial ridge of mx compared to mn?
maxillary first premolar and mandibular first premolar
mx buccal ridge more prominent than mandibular
facial developmental depressions
mx first pm: m and d facial dev depressions usually present
mx second pm: mesial rarely present (2%), distal sometimes present (25%)
mn first pm: smooth in the occlusal 1/3, mesial likely to be deeper
mn second pm: mostly absent, when present distal likely to be deeper
number of roots
mx first pm: mostly 2
mx second pm: 1 conically shaped root
mn first and second pm: 1
root curvature
applicable to mx second pm, mn first and second pm
mx second pm: distal curvature at apex of root
mn first pm: distal curvature at apex of foot
mn second pm: most of the time distal curvature at apex of root
m/d view
occlusal table location
mx first pm: centred over root trunk
mn first pm: slopes lingually
m/d view
cusp tip position
mx first pm: located aligned w the apex of the facial / lingual root
mn first pm: facial cusp centred FL, lingual cusp in line with lingual surface of root
mn second pm: facial cusp at junction of facial and middle third
m/d view
cusp heights
mx first pm: facial taller and sharper than lingual cusp
mx second pm: facial and lingual cusp nearly same length
mn first pm: facial cusp much taller than lingual cusp
mn second pm: facial cusp taller than the lingual cusp
mn second pm: mesio lingual cusp is longer and taller than distolingual cusp
m/d view
marginal ridge groove
grooves are linear depressions, marginal = extend onto mr
mx first pm: marginal ridge groove on mesial marginal ridge is very prominent at 2/3 of FL distance, distal marginal ridge rarely has developmental groove crossing it
mx second pm: mesial mr ridge usually absent, distal mr ridge more likely absent
mn first pm: usually no mr groove
mn second pm: usually no mr groove but rarer on distal mr
m/d view
marginal ridge anatomy
mx first pm: m mr < d mr mesial mr groove present
mx second pm: rare to have m mr
for mx premolars, DISTAL marginal ridge is located more cervically than mesial marginal ridge
mn first pm: m mr more cervical than d mr , d mr more horizontal than m mr
mn second pm: distal mr cervical to m mr, m mr horizontal at right angle to long axis, d mr concave
m/d view
triangular ridge angulation
mx first pm: facial and lingual tr at 45 deg to occlusal surface
mn first pm: facial tr slopes lingually at roughly 45 deg
m/d view
facial and lingual hoc
mx first and second pm: facial at cervical third, lingual at middle third
mn first pm: facial at cervical third, lingual at middle third near lingual cusp tip
mn second pm: facial; at cervical third, lingual at occlusal third
m/d view
cervical line form
mx first pm: curves occlusally, mesial cervical line form may have a small “v” apical extention at midpoint, distal cl form shows less curvature
mx second pm: mesial may be irregular / evenly convex. distal shows less curvature
mn first pm: mesial curves occlusally, distal less curvature
mn second pm: mesial curves occlusal slightly, distal less curvature
notice distal cervical line form is less curved throughout all premolars
cervical crown anatomy
mx first pm: mesial has cervical developmental depression while distal is flat, no have
mx second pm: both mesial and distal are quite flat, no developmental depressions
mn first pm: mesial surface is either flat or concave distal surface has concavity
mn second pm: mesial has a flat or concave depression
m/d view
shape of mesial and proximal contacts
mx first pm: mesial prox contact is located facially and circular, distal prox contact is facial and ovoid w larger FL dimension
mx second pm: both m n d prox contacts are facial and ovoid w larger FL dimension
mn first pm: both m n d prox contacts are facial and circular
mn second pm: m prox contact is facial and circular, distal prox contact is facial and ovoid w larger FL dimension same as mx first pm
notice all the contacts are facial
what’s so special about the root of mx first pm?
it is the only pm with 2 roots most of the time
mx first pm facial root is longer than lingual root
m/d view
root surface form
mx first pm: mesial root surface has a deeper developmental depression than distal
mx second pm: mesial has developmental root depression most of the time (but not always) and distal will have deeper root dev depression
mn first pm: mesial has developmental depression 45% of the time, distal mostly has deeper root dev depression
mn second pm: mesial is flat or convex most of the time, distal has dev depression most of the time
where is the root bifurcation located?
which premolar has 2 roots? (61%)
apical third of root
occlusal view
mesio facial angle
angle made by the mesiofacio cusp ridge and mesial marginal ridge
mx first pm: 90 deg
mx 2nd pm: rounded
mn first pm: acute angle
occlusal view
disto facial angle
angle made by distal marginal ridge and distal facial cusp ridge
mx first pm: acute angle
mx second pm: rounded
mn first pm: 90 deg same as mx first pm mesiofacial angle
notice mx second pm is always rounded, no info on mn second pm
occlusal view
faciopalatal line angles of maxillary first pm
more prominent
rmb u tried to give the central incisor more dimension w this
occlusal view
facial developmental groove of maxillary first pm
why only maxillary first pm?
deep, slight M/D concavities in facial outline
only mx first pm usually got mesial and facial developmental depressions
which tooth does not exhibit lingual crown convergence?
mx second pm: parallel coz of ovoid occlusal crown form
mn second pm: coz of square occlusal crown form
occlusal view
number of cusps
2 cusps for mx first pm, second pm, and mn first pm
mn second pm is special
can have 3 mostly (2 lingual) / 2 cusps 43% / 4 cusps 3%
occlusal view
any significant features of the facial cusp ridges?
mx first pm: distal facial cusp ridge is more facial than mesial facial cusp ridge
mn first pm: both M and D cusp ridges are nearly in a straight line
occlusal view
facial triangular ridge of mx first pm
the same as cusp ridge
M/D slopes of the facial triangular ridge meet at the crest of ridge at 120 deg
presence of lingual triangular ridge in mx first pm
seldom prominent
occlusal view
fossae
mx first pm: mesial and distal triangular fossa are present
mx second pm: mesial and distal fossa, closer to centre of tooth
mn first pm: mesial linear fossa, distal circular fossa is deeper, larger than mesial fossa
mn second pm: mesial and distal fossa + central fossa on 3 cusp tooth (largest)
occlusal view
transverse ridge definition
where 2 triangular ridges share the same base (facial to lingual / palatal)
occlusal view
which tooth has transverse ridge?
premolar
maxillary first premolar and mandibular first premolar
occlusal view
developmental groove anatomy
mx first pm: mesiofacial, distofacial, mesial marginal(most prominent) and central
mn first pm: mesiolingual developmental groove angles in a mesiolingual direction from the Mesial fossa, central groove is crescent shaped
mn second pm: mesial and distal groove in facial direction, lingual groove
occlusal view
occlusal pattern of mn second pm
Y for 3 cusps
U/H for 2 cusps
occlusal view
supplemental groove
mx first pm: triangular ridges often flanked by shallow supplemental grooves (2/4)
mx second pm: several supplemental grooves extending from the pits at the depth of each fossa to give a wrinkled appearance
lingual view
lingual crown dimension for mx first pm and mn first pm
mx first pm: lingual surface is smaller than facial surface
mn first pm: lingual crown is narrower MD than facial
lingual view
lingual cusp position
mx first pm; offset mesially
mx second pm: mesial to long axis of the root
mn first pm: aligned with facial triangular ridge, lingual cusp offset medially
NA for mn second pm coz 2 lingual cusps
lingual cusp form
mx first pm: smooth, spheroidal /round
mx second pm: L cusp slightly shorter than F cusp, relatively sharp
mn first pm: small and often pointed
NA for mn second pm
surface visibility from lingual aspect
mx second pm: proximal surfaces not highly visible
mn first pm: almost all is seen
marginal ridge location
which tooth has a mesiolingual groove?
mandibular first premolar, mesiolingual groove separates mesial marginal ridge from lingual cusp
lingual view
cervical line form
mx first pm: curves symmetrically toward root apex
mx second pm: less curvature
mn first pm: slightly convex in direction of root apex
mn second pm: almost straight
which tooth is this applicable to only?
lingual root apex form
mx first pm: lingual root apex is blunter than facial root apex and shorter than facial root, lingual root can bend either mesially or distally
lingual view
lingual surface form special feature
only applicable to the mn second premolar
flattened and grooved occlusally
