PERMANENT PREMOLARS Succeed deciduous molars 8 in all

PERMANENT PREMOLARS • Succeed deciduous molars • 8 in all • Max 1 st 2 nd & Mand 1 st – from 4 lobes • Mand 2 nd – from 5 lobes • one large buccal cusp • Mand present with two lingual cusps (2 lingual lobes)

st 1 MAXILLARY PREMOLAR • 2 cusps F & L • B – longer • 2 root canals & 2 pulps (could be 1 root) • All cusp tips centered over roots

UNIQUE FUTURES • • • the largest occlusocervical dimension of any posterior tooth the only premolar where the mesial cusp ridge (arm) is longer than the distal cusp ridge and the facial cusp is located slightly distal to the midroot axis The mesial marginal ridge is crossed by a substantial groove The mesial crown surface has a relatively deep developmental depression The mesial development root depression is deeper than the distal root depression The junction of the facial and lingual triangular ridges (at the central developmental groove) occurs at an occlusocervical location that is approximately onethird to one-half of the distance from the facial cusp tip to the cervical line, a depth that is greater than any other tooth

Facial view • • Similar to canine buccal cusp is long Contact areas – same level M & D marginal ridges sharper than canines • Crown - shorter & narrower MD • Root - shorter canine

• B cusp tip – located D to midline and separates • prominent buccal ridge descends to the cervical line of the tooth • Cervically, from contact areas – D border – straight, M – more concave

Lingual view • lingual cusp is smaller and the tip of that cusp is shifted toward the mesial • lingual surface is rounded in all aspects

Mesial view • groove extends from mesial marginal ridge cervically - mesial marginal groove • It crosses the mesial marginal ridge and runs from the occlusal to the middle third of the crown, lingual to contact area

• mesial marginal developmental groove - concavity in the cervical third that extends onto the root • The facial outline – convex with the contact at cervical third of the crown • Cervical curvature is greater M • Cusps tips close to each other

Distal view • NO groove crossing distal marginal ridge • No crown developmental depression (just root) • Cervical curvature lesser in size • B & L cusp tips – centered over the root

Occlusal view • two well-defined cusps buccal and lingual • The larger cusp is the buccal • lingual cusp tip is shifted M • outline - hexagonal appearance • On M marginal ridge - M marginal developmental groove • Each cusp -four ridges • Triangular ridges form transverse ridge

• • Primary grooves are sharp, deep Secondary shallower First premolar – fewer secondary grooves Second more - and more pronounced

Root/Pulp cavity • Bifurcated or single (will have grooves) • Single or two roots – two canals • Pulp horns = number of cusps

Maxillary nd 2 Premolar • Single root (usually) with a single pulp canal • Root length is as great if not greater than the max. 1 st premolar

UNIQUE FUTURES • the largest occlusocervical crown dimension of any posterior tooth, a distinction shared with the maxillary first premolar and mandibular first premolar • approaches bilateral symmetry closer than any other posterior tooth • The facial and lingual cusp heights are closer to the same level than any other premolar • The mesial and distal fossae are closer to each other than any other posterior tooth

Facial view • Buccal cusp is smaller than the max. 1 st premolar, but still longer than the lingual cusp • Cusps are not as sharp as max. 1 st premolar (rounder in appearance) 1 st premolar

Lingual view • The lingual cusp, however, is more nearly as large as the buccal cusp. • The cusp tip is in the middle of the occlusal edge

Mesial view • Buccal cusp is a little longer than the lingual cusp • NO developmental groove • Developmental depression just a shallow – on the root surface • No mesial concavity, instead the mesial crown surface is convex 1 st premolar

Distal view • Shows the similarity of 1 st and 2 nd , except that the B & L cusps of 2 nd are more even in length 1 st premolar

Occlusal view • From occlusal view the crown is round in shape • Multiple supplemental grooves which give the occlusal surface the appearance of being wrinkled • Central groove is shorter and irregular

Mandibular st 1 Premolar • Developed from four lobes • Mesial, Middle and Distal lobes form one buccal cusp— lingual lobe forms the lingual cusp • Large buccal cusp with a small NONFUNCTIONAL lingual cusp • Smaller of the mandibular premolars (opposite of the maxillary arch)

Facial view • Lingual cusp resembles a canine while the buccal cusp resembles the 2 nd premolar & centered directly over the root • The outline is very nearly symmetrical bilaterally, displaying a large, pointed buccal cusp. From it descends a large, well developed buccal ridge • Developmental depressions - between 3 B lobes • Buccal triangular ridge is prominent on the buccal surface

Lingual view • Lingual less convexity than the buccal • Mesiolingual developmental groove – separates the MMR from L cusp • Broader MD on the B cusp portion • Can see most of the occlusal surface, as well as mesial and distal marginal ridges

Mesial view • The large buccal cusp tip is centered over the root tip, about at the long axis of this tooth • The very large buccal cusp and much reduced lingual cusp are very evident • mesial marginal ridge is more cervical than the distal contact ridge • mesiolingual developmental groove can be seen between MB & L lobes • the buccal outline is prominently curved from the cervical line to the tip of the buccal cusp.

Distal view • The distal marginal ridge is higher above the cervix and doesn’t have extreme lingual slope (more nearly at right angle) • No ML developmental groove • Root – more convex D than M • Shallow developmental depression

OCCLUSAL VIEW • • The occlusal outline is diamond-shaped The large buccal cusp dominates the occlusal surface. The occlusal surface slopes sharply lingually in a cervical direction HUGE buccal triangular ridge moves into the lingual triangular ridges and functions as transverse ridge. Very small lingual triangular ridge Marginal ridges are well developed and the mesiolingual developmental groove is consistently present. There are mesial and distal fossae with pits, affectionately known as 'snake eyes' when they are restored.

Mandibular nd 2 • Shorter B cusp than 1 st • M & DB cusp ridges more rounded • Contact areas – broad • Root – wider MD & longer with blunt apex Premolar

Lingual view • 2 or 3 cusps • If 2 – L lobe higher. There is developmental depression DL • If 3 – ML (wider &longer) & DL cusps divided by L groove • Surface of root – wide than 1 st

Mesial view • lingual cusp is shorter than the facial cusp • Crown & root wide & root surface has been described as flat or convex • MR at 90 angle to long axis of tooth • a mesial view as can be seen from a distal view

Distal view • both lingual cusps are visible form this view since the distolingual cusp is smaller • The distal root surface has a developmental depression • The cervical line curvature is less on the distal than mesial.

Occlusal view • The mandibular second premolar has 3 cusps more often than it has 2 cusps • Buccal cusp the largest • All cusps have well developed deep developmental grooves • 2 -cusp premolar has a transverse ridge whereas there is no such ridge on the 3 -cusp premolar with its “Y”-shaped groove pattern • The 2 -cusp second premolar has a central developmental groove creating either a “U” or “H”-shaped groove pattern

• With 3 cusp premolars, the occlusal outline form is nearly square. The outline of 2 cusp premolars has been described as round or oval • 3 fossae (M, D and central) on 3 -cusp premolars and 2 fossae (M & D). The central fossa was the largest

Root/Pulp cavity • Similar to 1 st • Longer and wide B • 2 or 3 horns more pointed than 1 st • One root canal