maxillary 1st premolar
DESCRIPTION
Maxillary first premolarTRANSCRIPT
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!