Maxillary premolars (bicuspids)

-We have 4 maxillary premolars; two in right and two in left side.

-Mesial to them is the canine and distal the molars present.

-They have two cusps (one buccal and one lingual) {bicuspid}

Premolars are posterior teeth because:

1 -They have occlusal surface instead of incisal ridge.

2 -The bucco-lingual measurements are greater than the anterior teeth.

4 -The crown is shorter than the anterior teeth.

5 -The cervical curvature is less than the anterior.

3 -The contact areas are broad and nearly at the same level.

Maxillary first Maxillary first premolarpremolar

ChronologyAppearance of the dental organ 7 m.i.uFirst evidence of calcification 11/2-13/4 years.

Enamel completed 5-6 yearsEruption 10-11 yearsRoot completed 12-13 years

Type and functionThis tooth has the function of tearing and grinding food.

No. of lobesIt has four lobes (three buccal -the middle is well developed (the buccal cusp)- and one lingual (the lingual cusp).

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RelationThe upper 1st premolar makes contact mesially with the distal surface of the canine and distally with the mesial surface of the 2nd premolar.

No. of surfaces It has four surfaces and Occlusal aspect.

Buccal Lingual Mesial Distal

OcclusalNo. of roots

It has 80% 2 roots.

The buccal aspect

Geometrical outline

-The short side cervically.-The long side occlusally.

Trapezoid in shape.

The outline -Mesial outline is slightly concave till

the half of the crown (the contact area). -The distal outline is straight or

slightly concave till the contact area (more occlusally).

-The mesial slope is longer than the distal slope.

Surface anatomyThe elevations

-The cervical ridge

-The buccal ridge

The depressions

Two developmental grooves mesial and distal to the buccal ridge.

The root

The buccal root is similar to that of the canine but shorter.

Lingual aspect

-Similar to the buccal aspect but in a reverse manner and with lingual convergence.

-The lingual cusp is shorter than the buccal cusp by 1mm.

-The mesial and the distal slopes of the lingual cusp have right angle.

-The lingual surface is spheroid and has a less developed lingual ridge Than the buccal ridge.

-Cervical line is slightly convex or even straight.

Mesial aspect

Geometrical outlineTrapezoid in shape.

-The short side occlusally.-The long side cervically.

The outline -The buccal outline is convex till the

buccal cusp tip with the maximum convexity at cervical 3rd.

-The lingual outline is convex with the maximum convexity at the center.

-The lingual cusp is shorter than the buccal cusp.

-The mesial marginal ridge present at the junction of the occlusal and middle thirds

-The mesial contact area present at the middle third.

Surface anatomy1 -Mesial developmental groove crossing

the mesial marginal ridge.2 -Mesial developmental depression

above the contact area and continue on the root surface ( The canine fossa).

-The bifurcation of the root present at the middle of the root length.

The root

-The buccal cusp tip is in one line with the center of the buccal root.

-The lingual cusp tip is in one line with the lingual border of the lingual root.

Distal aspectThe distal surface differs than the

mesial in :

1 -No developmental groove crossing the distal marginal ridge.

2 -No developmental depression on the crown or root.

4 -The cervical line is less curved or straight.

5 -The bifurcation present at apical third.

3 -The contact area is broader.

Occlusal aspect

It is hexagonal in shapeMesio-B. Disto-B.

Distal. Mesial

Disto-L. Mesio-L.

-Central developmental groove.

-Distal and mesial triangular fossa.

-Distal and mesial developmental pit.

-Distal and mesial marginal ridges.

-The buccal and lingual cusps have triangular ridge.

-The mesial marginal ridge is crossed by mesial developmental groove.

-The bucco-lingual measurement is larger than the mesio-distal measurement

The pulp cavity

Bucco-lingual section -Has wide pulp chamber

with two pulp horns. -There are two root canals

tapering to the apical foramen. -In case of one root ; it has

two root canals.

Mesio-distal section -The pulp chamber is

bulbous and short.

-The root canal is narrow to the apex

-The palatal root canal is wide.

Maxillary Maxillary 2nd premolar2nd premolar

ChronologyAppearance of the dental organ 8 m.i.uFirst evidence of calcification 2-21/4 years.

Enamel completed 6-7 yearsEruption 10-12 yearsRoot completed 13-15 years

Type and functionThis tooth supplements the maxillary first premolar in function of tearing and grinding food.

No. of lobesIt has four lobes (three buccal -the middle is well developed (the buccal cusp)- and one lingual (the lingual cusp).

4 5

RelationThe upper 2ndt premolar makes contact mesially with the distal surface of the 1st premolar and distally with the mesial surface of the 1st permanent molar.

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No. of surfaces It has four surfaces and Occlusal aspect.

Buccal Lingual Mesial Distal

OcclusalNo. of roots

It has 85% one root.

The buccal aspect

1 -The buccal cusp is less pointed and shorter.

2 -The mesial slope is shorter than the distal slope.

3 -The buccal ridge is less prominent.

-Similar to that of the 1st premolar and differs in:

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Buccal aspect.

The lingual aspect

-The lingual cusp is longer than that of upper 1st premolar.

-The buccal and lingual cusps are nearly equal.

4 5

Lingual aspect.

The mesial aspect

-The buccal and the lingual cusps are nearly at the same level.

-The mesial marginal ridge is more occlusal than the 1st premolar.

-No mesial developmental groove.

-Mostly it has one root.

-There is great distance between the buccal and the lingual cusps more than the 1st premolar.

The distal aspect

-There is no difference except it has one root.

The occlusal aspect

-It is oval or round shape

-Wide bucco-lingual dimension.

-Short central developmental groove.

-Multiple supplemental grooves.