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Questions and Answers
Which of the following statements about the lingual outline of the maxillary first premolar crown is correct?
In the four-cusp type of maxillary first premolar, which cusp is described as poorly developed and shorter than the distobuccal cusp?
Which of the following is NOT mentioned as one of the depressions on the occlusal aspect of the maxillary first premolar?
Which of the following statements about the roots of the maxillary first premolar is correct?
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In the three-cusp type of maxillary first premolar, which of the following statements is correct?
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Which of the following statements about the occlusal outline of the maxillary first premolar crown is correct?
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What is the typical geometric outline of the maxillary first molar on the buccal aspect?
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How many types of maxillary first molar are described in the text?
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What is the relationship between the mesial and distal roots of the maxillary first molar?
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In the four-cusp type of maxillary first molar, which cusp is the largest and sharpest?
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What is the relationship between the crown and cervical line on the buccal aspect of the maxillary first molar?
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What is the characteristic of the occlusal outline of the maxillary first molar?
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Study Notes
Mesial Aspect
- Geometric outline form is trapezoid with the shortest of the uneven sides present occlusally
- Buccal outline is very convex cervically, representing the prominent mesiobuccal cervical ridge, then becomes straight from the ridge to the occlusal margin
- Lingual outline is more gradually convex in the cervical and middle thirds and straight in the occlusal third
- Occlusal outline: the mesiolingual cusp is sharper than the mesiobuccal cusp
- Mesial marginal ridge is nearly as wide buccolingually as the cusp tips
- Cervical line shows some curvature occlusally
Distal Aspect
- Crown is narrower and shorter on the distal side than on the mesial side
- Distal marginal ridge is more cervically oriented
- In the four-cusp type, the distolingual cusp is poorly developed and shorter than the distobuccal cusp
- All three roots are seen from this aspect, but the distobuccal root is superimposed on the mesiobuccal root
Occlusal Aspect
- Rectangular with buccal and mesial sides longer than the lingual and distal sides
- In the four-cusp type: there are two large cusps (mesiobuccal and mesiolingual) and two very small cusps (distobuccal and distolingual)
- Elevations: four cusp triangular ridges, mesial and distal marginal ridges
- Depressions: central fossa, pit, mesial and distal triangular fossae and pits, central developmental groove, buccal developmental groove, lingual developmental groove
Cusp Types
- Maxillary First Molar can have one of four types:
- Four-cusp type with two buccal and two lingual cusps
- Four-cusp type with two buccal and two lingual cusps with an oblique ridge
- Three-cusp type with two buccal and one lingual cusp
- Two-cusp type (resembling the premolars)
Buccal Aspect
- Geometric outline: trapezoid
- Mesial outline: straight
- Distal outline: convex
- Occlusal outline is scalloped with no definite cusp ridge form
- There is a large mesiobuccal cusp and a small distobuccal cusp
- Surface anatomy: no buccal groove on the buccal surface but just a notch
- Well-developed cervical ridge with a most bulging part mesially (mesiobuccal cervical ridge)
- Cervical line is convex towards the root with the crest of curvature is present mesially to outline mesiobuccal cervical ridge
- Roots: three roots (mesiobuccal, distobuccal, and lingual) are thin and widely spread
- Furcation is close to the cervical line
- Distal root is considerably shorter than the mesial root
Lingual Aspect
- Crown is narrower due to the lingual convergence and its surface is very convex
- In the four-cusp type, the mesiolingual is the largest, sharpest cusp, and the distolingual cusp is poorly developed
- Lingual developmental groove separates the two lingual cusps
- In the three-cusp type, the distolingual cusp is not present
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Description
Test your knowledge on the morphology of maxillary first molars, including the different types and geometric outlines of this tooth. Explore the characteristics of the buccal aspect and learn to identify key features such as the trapezoid shape and marked crown convergence.
