Lecture 6 Flashcards
Canine - middle ridge
Lingual ridge
Canine
distal pinch
Canine maxillary vs mandibular incisal edge
Mesial angle is greater, incisal edge is much less horizontal.
Premolar function
Mastication - this is the first tooth with an occlusal surface.
Maintain vertical dimension of the face
Assist canines to shear/cut food.
Support cheeks and mouth corners.
Vertical dimension
Distance between mental protuberance and tip of nose.
Most pemolars have
2 cusps. Mandibular 2nd premolar might have 3 cusps (one buccal two lingual).
Premolars develop from
3 facial lobes, one or two lingual cusps.
Class traits of premolars similar to anterior teeth
Crowns taper to cervical
CEJ curve similar in shape but less curved.
Roots taper narrower apically and lingually.
Premolars differ from anteriors
Two or three occlusal cusps vs incisal edge.
Marginal ridges more horizontal (except mesial marginal ridge of mandibular first premolar).
Crowns are shorter.
HOC = facial in cervical 3rd, lingual in middle 3rd. facial HOC is not too close to CEJ. - like Maxillary canine in this way
Proximal contact areas more cervical and broader.
Buccal view - premolars
Pentagon outline of crown
Contact areas are convex, distal contact is more cervical than mesial (except mandibular 1rst premolar).
Mesial cusp ridge longer than distal (except maxillary first premolar).
Premolars - lingaul view
Crown outline narrows towards lingual. Some proximal surfaces are visible (except for 3 cusp mandibular second premolars with 2 lingual cusps).
Premolars - proximal view
Mesial marginal ridges - more occlusal than distal (except mandibular first premolar).
Premolars- occlusal view
Wider faciolingually than mesiodistally.
Occlusal table bound by marginal and cusp ridges.
Proximal contacts are located buccal to buccolingual midline. Lingual embrasure spaces are larger.
height of marginal ridge proportional to
HOC
Transverse ridges - premolar
Traingular ridges join to form this - except 3 cusp mandibular second premolars.
Mandibular 1st premolar
Do not connect mesial and distal. The central groove is so subtle and shallow that it is not necessary.
Arch traits that differentiate Maxillary and mandibular premolars
Mand have more noticeable crown tilt than maxillary.
Mandibular premolar has
less prominent buccal ridge.
All premolars are larger
buccolingually than mesiodistally *mand 1st premolar is closer to square. Max premolar is rectangular (buccolingual greater than mesiodistal).
Maxillary 1st vs 2nd premolar
Max 1st larger than 2nd. More convergence from prox contact to cervical on first than second.
Location of contacts = max premolars
Mesial contact junction of occlusal and middle 3rd, distal contact middle third. - like max canine and max lateral.
Location of buccal cusp tip of max premolars - buccal
Max second - mesial cusp ridge is shorter than distal. Max first is opposite.
Shape of buccal cusp of max premolars
Cusp is sharper on max first premolar than second. Max canine = 105 deg, Mand = 100 angle for comparison.
Buccal ridge and depression of max premolars - buccal view
Buccal ridge more prominent on max first premolar than max second. (buccal ridge - middle lobe) Developmental grooves = between lobes.
PKT notches
Notches made by developmental grooves in occlusal premolar. This allows food to escape through these notches. These notches are more common on mesail of 1st, distal of 2nd (not as prominent).
Roots of max premolars from buccal view
Max 1st premolar more likely to have two roots. About 65% do. Max second has only 1. Lingual root usually is straight while buccal tilts to distal.
Relative cusp size of max premolars - lingual view
lingual cusp shorter than buccal cusp - moreso on max 1st premolar than second.
Cusp ridges of max premolars - lingual
Lingual cusp relatively sharper on max second premolar than on first. **This can very due to wear.
Lingual cusp position for max premolars - lingual view
Both max 1st and 2nd premolars have the lingual cusp tip positioned mesial to the midroot axis.
Marginal ridges of max premolars - from lingual view
Distal marginal ridge is more cervical than mesial for both max 1st and 2nd premolars (best seen at mesail/distal views).
Roots of max premolars - lingaul
Max 1st - lingual root is shorter than buccal root. You can see it tilt distally.
Root crown ratio is 1.56 (same RCR as max canine) on 1st, 1.82 on 2nd. **This is the longest RCR in the maxillary arch.
Crown shape and morphology - max premolars - proximal
Max premolars have trapezoid outline.
Max 1st is the only premolar with a crown depression - always on mesial.
Relative cusp height of max premolars - proximal
Lingual cusp shorter than buccal cusp, more so on max first premolar than second premolar.
Facial HOC in cervical 3rd
Max premolars. Lingual HOC is in the middle 3rd (like all posterior teeth).
Distance between cusps on max premolars
Distance between cusps is the same for max first and second premolars. Both buccal and lingual cusp tips are located over the root.
Marginal ridge grooves of max premolars
Marg ridge groove is found often on mesial marginal ridge of max first premolar.
Cervical lines of max premolars
More CEJ curvature on mesial than distal (as for all teeth).
Max first premolar is the only premolar with
mesial root depression more pronounced than distal - only premolar with a mesial crown depression joining with the deep root depression.
Grooves and fossae of maxillary premolars from occlusal view
Triangular, usually long mesiodistally for 1st. 2nd has short central groove with thin marginal ridges. Longer the groove, thicker marginal ridges.
Relative proportions of max premolars from occlusal view
Both are long faciolingually, narrow mesiodistally.
Outline of Max premolars - occlusal view
2nd premolar usually very symmetrical. 1st is not -buccal ridge is very sharp and pronounced. Max first is more hexagonal than second. Looks a little twisted. **because of twisting, distal contact is a bit more forward compared to the mesial contact. These contacts are near the junction of buccal/middle 3rds.
Lingual cusp ridges of premolars
point mesially.
1st premolar
Buccal cusp is distal - 2nd is more central/mesial.
Mandibular first vs second premolar
Lots of variation in shape. Mandibular second premolar is the only premolar more likely to have 3 cusps.
Relative crown shape and size of mand premolars - buccal
Shoulders - junction of cusp ridges and functional surface. Both have rounded shoulders (first wider than second). Apex of mand first molar is sharper than second. More taper after shoulders on 2nd - as a result 2nd looks thicker on cervical. PKT notches more common on mesial of first and distal on second.
Spiel way spaces
Spaces that allow food to escape.
Mand 2nd appears to be…
wider than first due to more obtuse curve.
Cervical lines of mand premolars - bucal
CEJ is more curved…
Proximal contact locations - mand premolars
Most have mesial more occlusal, distal more cervical. Mand 1st premolar is opposite. Mand 1st is the only tooth with a contact on mesial 3rd in junction of middle and occlusal.
Mand premolars from the buccal view
Both types of mandibular premolar roots taper to apex with distal bend of apex more common. Root crown ratio on second premolar is larger.
Mand premolars from lingual view -crown shape
most mandibular premolars taper narrower towardlingual (except some 3 cusp type of mand 2nd premolar)
Lingual cusps of mand premolars - lingual
Lingual cusp of mand 1st premoalr is very short. This lingual cusp is non-functional and is located medial to midline. Does not participate in occlusion at all- this is like an enlarged cingulum.
Lingual cups on 2nd mand premolar is slightly shorter than the buccal and is mesial to midroot axis.
Marg. ridge of mand premolars - lingual
Mesial lingual groove - mand 1st premolar is the only premolar to have its mesial marginal ridge more cervical than the distal.
Grooves on mand. premolars from lingual view
Only mand 2nd premolars with 2 lingual cusps have a lingual groove separating them.
Crown shape of mand premolars from proximal views
Crowns tip noticeably to the lingual, more so on mand first premolar than second.
Outlines are rhomboid.
Lingual cusps are shorter.
Axial/vertical loading
Shapes made for this - interaction between max and mand teeth.
Marginal ridges of mand premolars - proximal views
Mesial marginal ridge slopes at 45 degrees for mand 1st. Nearly parallel to buccal triangular ridge.** Important for identifying right from left.
Marginal ridge grooves and mesiolingual grooves - mand premolar proximal view
Mesiolingual groove is present of 1st, not 2nds. Second premolars sometimes have marginal ridge grooves.
Cervical lines of mand premolars
More CEJ on mesial than distal -lingual CEJ more occlusla than buccal.
Mand 1st premolars have mesial and distal
Root depressions - deeper on distal.
Mand 2nd have distal root depression, no mesial.
Outline of mand premolar - occlusal
Has more bulk in distal half than mesial half.
Has mesiolingual line angle that is flat (pushed in).
Diamond shaped occlusal outline.
Occlusal table is triangular.
Outline shape of madn premolars - occlusla cont. Mand 2nd.
Two cusped type has almost rounded outline - three cusped is square. Occlusal tables are square on mand 2nd.
Rounded fossae
No triangular fossae on mand first premolars. You have this instead. Mesial distal circular fossae resemble snake eyes.
Distal fossa usually larger than mesial.
Two cusp mand second premolars
U and H groove pattern on mand 2nd premolars with 2 cusps. This is a common board question.
Mand 2nd premolar 3 cusps ridges/fossae/grooves
No transverse ridge - only premolar with central fossa with mesial and distal fossa. Lingual groove forms Y pattern.
