By

Dr. Abhishek Solanki

INTRODUCTION Premolars are so named because they are

placed between the anterior teeth and the molars

(pre = before)

Premolars assist canines & molars in tearing and

chewing food

Have two cusps (bicuspid) & two roots (buccal &

lingual)

Eruption : at 10-11 years

TOOTH NUMBERING Universal : #5 , #12

Z-P : 4 4

FDI : 14, 24

CHRONOLOGY First evidence of calcification :1.5 – 1.75 yrs

Enamel Completion : 5-6 yrs

Eruption : 10-11 yrs

Root completion : 12-13 yrs

DIMENSIONS (in mm)Cervico-occlusal Length of Crown 8.5

Length of Root 14

Mesiodistal Diameter of Crown 7

Mesiodistal Diameter of Crown at Cervix 5

Labio- or Bucco-lingual Diameter of Crown 9

Labio- or Bucco-lingual Diameter of Crown at Cervix 8

Curvature of Cervical Line—Mesial 1

Curvature of Cervical Line—Distal 0

Buccal Aspect Crown : Pentagonal shaped

Crown closely resembles to maxillary

canine and second premolar

Mesial margin joins the mesio-occlusal

slope to create an obtuse mesio-occlusal

angle

Contour of the mesial outline is concave

from the contact area to the cervical line

The mesial slope of the buccal cusp is

longer than distal slope, which is the

opposite of canine

Disto-occlusal angle is a little less

prominent and the cervical concavity is not

as deep

Occlusal margin of this tooth is, similar to

the incisal margin of the maxillary canine

Buccal ridge

Mesio-buccal & distobuccal developmental

depressions on each side of buccal ridge

Lingual Aspect

• The crown tapers towards the lingual aspect

• The lingual cusp is shorter than the buccal

cusp

• The lingual cusp is smooth from the cervical

portion to the area near the cusp tip

• The cusp tip is pointed with mesial and

distal slope meeting at an angle of about

90 degrees

• Small portion of the buccal cusp can be

seen from this aspect

Smoothly convex in all directions

There is no clearly defined lingual ridge

Mesial and distal outlines are normally

somewhat convex & shorter than the same

outlines of the buccal surface

Lingual cusp tip is not as sharply pointed as

the buccal cusp tip

The mesio-occlusal slope is shorter than the

disto-occlusal slope

Mesial Aspect• From the mesial and distal aspect both the

buccal and lingual cusps are visible

• A well developed mesial marginal ridge

and a mesial marginal developmental

groove is present

• In the middle of the mesial surface is the

mesial developmental depression which

continues beyond the cervical line

Mesial concavity

Shape of the mesial surface is trapezoidal

Buccal outline is generally convex, with

the height of contour in the cervical third

Lingually the outline takes the form of

an even arc, with the height of contourin the middle third

Occlusal margin is irregularly concave

and the majority of it is made up of the

mesial marginal ridge.

A prominent mesial marginal groove is

usually present indenting the occlusal

margin almost two-thirds of the way

from the buccal to the lingual outline.

Distal Aspect There is no developmental depression or

groove on this aspect, instead it is convexat almost all points

The curvature of the cervical is less on thisaspect

The contact area is near the junction ofocclusal and middle third

distal is remarkably similar to the mesial

surface, although it is slightly shorter

occluso-cervically.

Lingual margin is almost symmetrical & is

quite convex, especially in middle third,

where height of contour is located

Occlusally, distal is similar to mesial aspect,

except that marginal ridge is located at a

more cervical level

There is normally no marginal groove

Occlusal Aspect• Within cusp ridges and marginal

ridges the following are present

TBC & TLC : Tip of Buccal & Lingual

cusp

BTR & LTR : Buccal & Lingual

Triangular ridge

DBDG: disto-buccal developmental

groove

DTF & MTF : Mesial & Distal

triangular fossa

CG : Central groove

outline of crown can be described as

hexagonal or six-sided and it is wider

buccolingually than mesiodistally

prominent buccal ridge is primary

contributor to generally convex buccal

outline

lingual margin is evenly convex, almost

in a semicircle

Proximal margins are relatively straight

& they converge toward lingual

Root• Most Maxillary first premolars have 2 roots,

but one and three roots can also be seen

• Two roots : buccal and lingual

• Buccal portion of the root resembles canine

• The root when viewed from the proximal side shows a big

trunk and bifurcation area from where the buccal and

lingual root separate

• A developmental depression is seen on the mesial aspect

of the trunk

TRUNK

REFERENCES CONCISE DENTAL ANATOMY & MORPHOLOGY :

JAMES L FULLER

DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION:

WHEELER’S

TEXTBOOK OF DENTAL ANATOMY, PHYSIOLOGY &

OCCLUSION: RASHMI GS (PHULARI)

INTERNET