Maxillary 1st Premolar

Maxillary premolars

2 in the right(#14|#15) and 2 in the left (#24|#25)

Premolars are so named because they are anterior to the canines and molars

Assist the Canines and Molars in tearing and chewing food

Have two cusps & sometimes one or two roots

Maxillary First Premolar

FUNCTION:1. Assist in shearing and cutting2. Support the corners of the mouth

• Has 2 cusps buccal and lingual

• Crown is angular shape

• Crown is shorter than canine

• Most have 2 roots and 2 canals

Chronology:

First evidence of calcification:

1 ½ - 1 ¾ year

Enamel completed 5-6 years

Eruption 10-11 years

Root completed 12-13 years

Measurement Table

Cervico-cocclusal length of the crown

Length of root

Mesiodistal diameter of crown

Mesiodistal diameter of crown at cervix

Labio- or buccolingual diameter of crown

Labio- or buccolingual diamter of crown at cervix

Curvature of cervical line- Mesial

Curvature of cervical line- Distal

Dimensions* 8.5 14.0 7.0 5.0 9.0 83.0 1.0 0.0

Buccal Aspect

Crown: roughly trapezoidal

Mesial outline: Slightly concave

Distal Outline: nearly straight

Mesial cusp slope is nearly straight while the distal cusp slope is slightly convex

D M

Surface of the crown

Buccal surface: convex

Middle lobe : prominent bucally forming the BUCCAL RIDGE

Shallow depressions are present mesial and distal to the buccal ridge.

Contact areas: Mesial is at middle third while Distal is at occlusal third

Cervical line: convex root wise

Mesial & Distal Outline of the Root: It tapers to a pointed apex that is slightly curved distally.

If two roots are present, the lingual root is hidden behind the buccal root as it’s shorter and narrower than the buccal root.

Surface of root: convex and smooth

Lingual Root

Lingual cusp: Shorter by 1mm but

sharper than buccal cuspSmooth and spheroidal

from cervical portion near the cusp tip

Mesial and Distal Outlines: Convex

Cervical line: convex root wise

Distal slope is longer than Mesial slope

Lingual surface: convex at middle ⅓

DM

Root

Mesial and Distal Outline of the root taper to a pointed apex that is curved distally

Surface of root: convex and smooth

Apex: more blunt than the buccal root apex

If two roots are present, the lingual root is shorter and narrower than buccal root

Mesial Aspect

Shape: TrapezoidSmallest of the uneven

sides is occlusallyBuccal outline: convex

with maximum convexity at cervical ⅓

Lingual Outline: evenly convexCervical Line: regular in

outlineCurvature occlusally is less

1mm than cervical curvature on mesial

Buccal cusp: Longer than lingual cusp by 1mm

Buccal cusp tip: below the center of Buccal root

Lingual cusp tip: One line with lingual outline of the lingual root

Contact area: at the middle third & slightly buccal to midline

Mesial Development Groove: cross MMR & location: lingual to the contact area

Mesial Developmental Depression: Crown and continues with between the roots (canine fossa)

Two roots (80%)

Root trunk: about half the root length

Surface: smooth and convex

One root

Buccal and Lingual outlines: tapers to a blunt apex on center of the crown

Surface: smooth and convex except for a shallow depression in center that is deeper mesial than distal

Distal Aspect

Curvature of cervical line: less than mesial surface it is almost flat

Developmental Grooves: less evident

Root trunk: flattened with no outstanding developmentalsigns

Occlusal Aspect

Shape: Hexagonal2 equal buccal sides

(MB,DB)

Mesial side shorter than distal side

Mesiolingual side shorter than distolingual side

Crown is wider bucally than lingually

Elevations: Buccal triangular ridge Lingual triangular ridge Mesial & Distal

marginal ridgesDepressions: Central developmental

groove Mesial and Distal

triangular fossae Mesial marginal

developmental groove

Pulp Cavity

MD Section BL section

Lingual canal is larger and more accessible

Root canal

Pulp chamber

2 root canals

Narrow Wider

Buccolingual Section

2 well-developed roots that are not fully separated or 1 broad root

2 root canals Pulp horns: Usually extends further incisally under

the buccal cusp Maybe blunted Pulp chamber floor: Located below the cervical level Pulp chamber: Have at least root separation usually

shows the largest-incisal-apical dimension

Shape of the pulp chamber: square or root

Root canal: Appears to exit at tip of the root |

slightly to labial or lingual

Mesiodistal Section

Pulp horns: Blunted from the

mesial/ distal aspect

Pulp cavity: Tapers slightly from

occlusal aspect to apical foramen

Apical foramen: Appears to exit at tip of

the root

Cervical cross section

Shape: kidney

Pulp cavity:Constriction adjacent

to developmental groove

Some roots demonstrate 2 separated root canals

THE END!