Overview
This lecture covers the anatomy, function, and distinguishing features of premolar teeth, highlighting their differences from anterior teeth and between their upper (maxillary) and lower (mandibular) types.
Functions and General Features of Premolars
- Premolars assist molars in grinding and canines in tearing food.
- Help maintain vertical dimension of the face and support cheeks/lips.
- Normally develop from 4-5 lobes: 3 facial, 1-2 lingual.
- Variations exist, especially in the mandibular second premolar, which can have three cusps.
- Every person may have variations from textbook averages.
Comparison: Premolars vs. Anterior Teeth
- Premolars have an occlusal table (chewing surface) instead of an incisal edge.
- Both have crowns that taper cervically, but premolars taper less than anteriors.
- Marginal ridges in premolars are more horizontal, while in anteriors they are vertical.
- Premolar contacts are more cervical and broader than in anteriors.
General Anatomy and Class Traits
- There are 8 premolars: 2 per quadrant.
- Premolars are pentagon-shaped in facial view.
- Mesial contacts are higher (more occlusal) than distal contacts.
- The mesial cervical line is sharper than the distal.
- Roots taper lingually and bend distally at the apex.
- Crowns are broader faciolingually than mesiodistally.
Occlusal Features
- Occlusal table is outlined by the ridges of both buccal and lingual cusps.
- Triangular ridges from cusp tips meet at the central groove; three-cusp types lack a transverse ridge.
- Grooves and fossae are found on the occlusal surface; their arrangement depends on cusp number.
Arch Traits: Maxillary vs. Mandibular Premolars
- Maxillary premolars: prominent buccal ridge, no crown tilt, cusps similar in size.
- Mandibular premolars: less prominent buccal ridge, crowns tilt lingually, and often show a clear difference in cusp height.
Type Traits: First vs. Second Premolars
- Maxillary first premolars: sharper cusp, more prominent buccal ridge, often bifurcated roots, longer central groove, asymmetrical crown.
- Maxillary second premolars: rounder cusp, less pronounced buccal ridge, roots less commonly bifurcated, crown more symmetrical.
- Mandibular first premolars: small, nonfunctional lingual cusp, prominent lingual tilt, diamond occlusal outline.
- Mandibular second premolars: larger, functional lingual cusp(s), square occlusal outline, may have three cusps and three fossae.
Key Terms & Definitions
- Mastication — chewing of food.
- Occlusal Table — the chewing surface of premolars and molars.
- Cusp — a pointed or rounded projection on the chewing surface of a tooth.
- Fossa — pit or depression on the occlusal surface.
- Buccal — towards the cheek.
- Lingual — towards the tongue.
- Marginal Ridge — ridge forming the border of the occlusal table.
- Cervical Line — the line where the crown meets the root.
- Bifurcated — having two roots.
- Transverse Ridge — a ridge formed by the joining of two triangular ridges crossing the occlusal table.
Action Items / Next Steps
- Review module PowerPoints and resources for detailed diagrams.
- Pause and closely examine the video whenever anatomical differences are demonstrated.
- Prepare questions for further clarification if needed.