maxillary first and second premolars

embrasures

Spaces formed from curvatures where two teeth in same arch contact

three functions of embrasures

1) Function as spillways to direct food away from the gingiva.

2) Make the teeth more self- cleansing.

3)Protect the gingival tissue from undue frictional trauma, but at the same time provide the proper degree of stimulation to the tissue.

Types of embrasures

facial embrasure
lingual embrasure
gingival (cervical) embrasure
incisal embrasure

Maxillary second premolar begin formation

2-2.5 years

Maxillary second premolar eruption

10-12 years

Maxillary second premolar root completion

12-14 years

Function/role of maxillary second premolars

grinding during chewing

are maxillary second molars present in the primary dentition?

No
(Replaces the maxillary primary second molars - succedaneous teeth)

How many developmental lobes in maxillary second premolar?

4 - (3 facial, 1 lingual)

How many roots in maxillary second premolar?

1 root

Where is the outline form the broadest (buccal view)?

at the contact area in the middle 1/3

Cusp tip location (buccal view)

distal cusp is slightly longer than mesial cusp ridge

THIS IS OPPOSITE OF FIRST PREMOLAR

Root in Second Maxillary Premolar

Conical, smoothly convex root - often longer than the 1st premolar

CEJ in Maxillary second premolar

CEJ only slightly curved towards root apex

Crown from lingual view

crown is narrower on the lingual than the buccal

Lingual cusp (lingual view)

Lingual cusp tip slightly mesial to the long axis of the tooth

Is the cusp tip sharper than the maxillary first premolar?

yes (but not all of the time)

Lingual cusp vs buccal cusp in maxillary second molar

Lingual cusp more similar in height to buccal cusp than for max. 1st premolars

Distal marginal ridge - maxillary second premolar

is located more cervical than the mesial ridge

Mesial marginal ridge (from mesial view)

Mesial marginal ridge is more occlusally positioned than the distal marginal ridge (less occlusal surface visible)

Lingual height of contour (mesial view)

L height of contour is also near the junction of the cervical and middle 1/3's of the crown, but inside the middle 1/3.

Facial height of contour (mesial view)

F height of contour located near the junction of the cervical and middle 1/3's of the crown (but still inside the middle 1/3).

Are the facial and lingual cusps equal in height?

yes, nearly

"side" view - mesial root depression

may be present, no root bifurcation usually

"side" view - mesial marginal ridge groove

mesial marginal ridge groove is less common than in max. 1st premolars

Is there coronal concavity cervical to the contact?

NO coronal concavity cervical to the contact (no danger zone! no mesial menace!!)

Distal view - coronal developmental grooves or depressions

No coronal developmental grooves or depressions

Distal view - distal marginal ridge

more cervically located than mesial m.r. - more occlusal surface visible

Distal view - CEJ

Less pronounced CEJ curvature than on the mesial

Distal view - distal root depression

deeper than the mesial root depression.( opposite to that of 1st PM.)

Occlusal view characteristics - shape vs first max premolar

Oval outline with indistinct facial ridge and depressions, more symmetrical and less "twisted" than max. 1st premolar

Occlusal view - occlusal groove

shorter occlusal groove

Occlusal view - mesial marginal groove

no mesial marginal groove

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