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.