Oral Anatomy 3 - The Maxillary First Premolar
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How does the maxillary first premolar appear when viewed occlusally?
- When viewed occlusally, this tooth has a crown that appears ovoid, being broader buccally than palatally.
- Thus the profiles of the mesial and distal surfaces converge palatally.
- The mesiobuccal and distobuccal corners are less rounded than the mesiopalatal and distopalatal corners.
- The mesial and distal borders of the occlusal surface are marked by distinct ridges, the mesial and distal marginal ridges.
- The buccal and palatal cusps are separated by a central occlusal fissure that runs in a mesiodistal direction.
- The occlusal fissure crosses the mesial marginal ridge onto the mesial surface.
- On the distal side, the fissure terminates in a fossa before the distal marginal ridge.
- Supplimentary grooves from the central fissure are rare.
How does the maxillary first premolar appear when viewed buccally?
- Viewed buccally, the first premolar bears a distinct resemblance to the adjacent canine.
- A longitudinal ridge may be seen passing down the buccal cusp.
- The mesial and distal ridges of the buccal cusp each form a 30° slope and the mesio- and disto-occlusal angles are prominent, giving the crown a 'bulging shouldered' ovoid appearance.
- The mesial slope is generally longer than the distal slope.
How does the maxillary first premolar appear when viewed palatally?
- Viewed palatally, the buccal part of the crown appears larger in all dimensions than the palatal part so that the enire buccal profile of the crown is visible from the palatal aspect.
- The palatal cusp is lower, and its tip lies more mesially than the tip of the buccal cusp.
How does the maxillary first premolar appear when viewed from the mesial aspect?
- From the mesial aspect, the unequal height of the cusps is clearly seen.
- Note the canine groove extending across the marginal ridge from the occlusal surface.
- The cervical third of the mesial surface is marked by a distinct concavity, the canine fossa.
How does the maxillary first premolar appear when viewed from the distal aspect?
The distal apspect of the crown differs from the mesial aspect in that it lacks a canine groove and canine fossa.
What is the cervical margin and root like for the maxillary first premolar.
- The cervical margin follows a fairly level crouse around the crown deviating slightly towards the root on the buccal and palatal surfaces and away from the root on the mesial and distal surfaces.
- There are usually two roots, a buccal and palatal root, though sometimes there is only a single root.
- However, even a single root is deeply grooved on its mesial and distal surfaces.
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