PERMANENT PREMOLARS

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

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

3. 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 one-third to one-half of the distance from the facial cusp tip to the cervical line, a depth that is greater than any other tooth

4. 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

5. 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

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

7. 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

8. 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

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

10. 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 -Mmarginal developmental groove • Each cusp -fourridges • Triangular ridges form transverse ridge

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

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

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

14. 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

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

16. 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

17. 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 1st premolar

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

19. 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

20. Mandibular 1st 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)

21. Facial view • Lingual cusp resembles a canine while the buccal cusp resembles the 2nd 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

22. 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

23. 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.

24. 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

25. 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.

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

27. 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 1st

28. Mesial view • lingual cusp is shorter than the facial cusp • Crown & rootwide & 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

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

30. 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

31. With 3 cusp premolars, the occlusaloutline 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

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