Dental Anatomy and Occlusion - Maxillary First Premolars

occlusion

the way the teeth meet when the lower jaw (mandible) and upper jaw (maxilla) come together. It is how the teeth contact in any type of functional relationship.

Why is normal occlusion desirable?

1) allows oral functions to operate properly
2) provides the best esthetics
3) is helpful in the prevention of disease.

Malocclusion

Anytime normal occlusion does not occur in the mouth,

Malocclusion can have an effect on what?

- dental diseases
- chewing
-speech
-esthetics (especially facial profile)
-other functions of the oral cavity.

Reasons why malocclusion occurs

- hereditary
- trauma
- diseases
- habits (ex: thumb sucking)

How to identify class 1 occlusion in mouth?

mesial cusp slope (max canine) aligns with the distal cusp slope (mandibular canine)

stamp cusp

functional cusp

shearing cusp

non functional cusp

Cusps of maxillary premolar

Buccal cusps = non-functional
Lingual cusps = functional

Cusps of mandibular premolar

Buccal cusps = functional
Lingual cusps = non-functional

When do Maxillary first premolars begin formation?

1 ½-1 ¾ years

When do Maxillary first premolars erupt?

10-11 years

When do Maxillary first premolars have root completion?

12-13 years

Functions of Premolars

- Mastication
- Maintaining vertical dimension of the face
- Assist canines in shearing or cutting food ("transition" teeth)
- Support cheeks and corners of the mouth

What coronal outline does a maxillary first premolar have?

Hexagonal coronal outline

Buccal cusp position maxillary first premolar

B cusp tip is distal to center on the crown.

Mesial cusp slope VS Distal cusp slope - maxillary first premolar

M cusp slope longer than the distal cusp slope.
**This feature is unique.

Lingual cusp position - maxillary first premolar

Lingual cusp is mesial to the center

mesial depression - maxillary first premolar

involves both the crown and the root. It runs from the MMDG to the bifurcation of the root.

challenges of mesial depression - maxillary first premolar

difficult to clean
difficult to restore
may be perforated during endo access

root trunk - maxillary first premolar

body of the root from the CEJ to the level of the furcation

How does the distal view differ from the mesial? - maxillary first premolar

- CEJ a little flatter

- DMR a little more cervical in position

- NO developmental depression of crown!

- Root trunk has distal developmental depression in middle third but LESS than on mesial.

The maxillary first premolar has how many lobes of development?

4