بسم الله الرحمن الرحيم IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

1. بسم الله الرحمن الرحيم IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

2. PREMOLARS

3. Premolars There are four maxillary and four mandibular premolars. Relations: • 4 &4 contact: • 3 & 3 mesially and • 5 & 5 distally • 5 & 5 contact: • 4 & 4 mesially and • 6 & 6 distally.

4. General Features of Premolars • They are transitional teeth located between the canine and molar teeth. • By definition: Premolars are permanent teeth distal to the canines, and successors to deciduous molars. • There are two premolars per quadrant and are identified as first and second premolars.

5. General Features of Premolars • They have usually two cusps(bicuspid) : • One large buccal cusp, • Smaller lingual cusp • The lower second premolar may- sometimes- have two lingual cusps.

6. MAXILLARY FIRST PREMOLAR Chronology: • Enamel organ appearance: 7 mIU. • Beginning of calcification: 1½-1¾y • Crown completed: 5 – 6y • Eruption: 10 – 11y • Root completed: 12 – 13y • Number of lobes: four lobes : • Three buccally • One lingually

7. Buccal Palatal Mesial Distal No. of roots Two roots(60%). One root(40%). Occlusal

8. Geometric Outline of the Crown Facial and lingual aspects have trapezoid out line. The smallest of the uneven sides  cervically.

9. Outlines: • Mesial and distal outlines: are nearly concave and both become convex at cont. areas. Buccal Aspect • Mesial and distal cusp slopes: are also slightly concave D M Contact areas: Mesially: at the middle third(broad) Distally: Little more cervically than the mesial one(broader) M. slope > D. slope(sometimes convex) Bucc. cusp pointed, long and the tip is slightly distal to the vertical axis Cervical line: convex rootwise.

10. Surface Anatomy of the Crown Elevations: Buccal Aspect • The surface is convex with maximum convexity at cerv. 1/3representing cervical ridge • The middle lobe is prominent buccally forming bUCCAL ridge. Depressions: • Shallow depressions are present mesial and distal to the buccal ridge.

11. Outline and Surface Anatomyof the Root Buccal Aspect The M and D outlines of the root taper to a pointed apex curved distally. If two roots: The buccal root hides the lingual root as it is shorter and narrower than the buccal root. D M . The surface of the root is convex and smooth

12. Lingual Aspect • Lingual convergence: • Ling.s. is narrower than buccal s. • Outlines: • M and D outlines are convex M D • The L. cusp is shorter by 1 mm but sharper than the B cusp • The D slope of L cusp is longer than M slope Cervical line: is convex rootwise. • Surface Anatomy : • The surface is convex with maximum convexity at the middle 1/3. • The root is convex.

13. Outline and Surface Anatomy of the Root Lingual Aspect The M and D outlines of the root taper to a pointed apex that curves distally. D M If one root: The ling. Surface is convex and narrower MD than the buccal portion. If two roots: The lingual root appears shorter and narrower than the buccal root.

14. Proximal Aspects Mesial aspect Distal aspect Proximal aspects have trapezoid out line. The smallest of the uneven sides  occlusally.

15. Outlines of Proximal Aspects Mesial aspect Distal aspect Buccal outline : Convex with maximum convexity at cervical 1/3 representing cervical ridge. Lingual outline:convex with maximum convexity at middle 1/3 Cervical line:curves occlusally and less curved distally

16. Distal aspect Mesial aspect Occlusal outline: Bucc. cusp is longer than Ling. cusp by 1mm. Bucc. cusp tip is below the center of Bucc root. Ling. cusp tip is on line with Ling. border of the ling. root. MMR concave, at the junction of occ. & middle thirds. DMRmore cervical.

17. Surface Anatomy of Proximal Aspects Mesial Aspect Distal Aspect Contact areas: At the middle 1/3, bucc. to midline More cervically positioned & more buccally. • Mesial marginal developmental groovecrossing MMR and located lingual to the contact area. Smooth and convex surface except for a small flat area cervical to contact area(no canine fossa or develop. groove crossing the DMR) . • Mesial Developmental depression in the crown & continues on the root (canine fossa). Cervical line curvature: Less curved Curves occlusally

18. Outline and Surface Anatomy of the Root Mesial Aspect Distal Aspect In case of two roots (more common). Root trunk about half the root length. Root trunk is longer as bifurcation is near apical 1/3 Surface is smooth and convex except deep developmental depression below bifurcation that continue with the mesial dep. on the crown. Surface is smooth and convex except shallow devlop. depr. on the root trunk

19. In case of one root (less common) The B and L outlines tapere to a blunt apex in line with the center of the crown. The surface is smooth and convex except for a shallow depression in the center that is deeper mesially than distally.

20. Geometric outline Occlusal Aspect • Hexagonal • 2 equal buccal sides (MB, DB) • M side shorter than D side. • ML side shorter than DL side. • Thickness(BL) is greater than width(MD). • The crown is wider buccally than lingually, due to lingual convergence of the crown D M

21. Occlusal Aspect • Surface anatomy Elevations: Bucc. triangularridge. D M Ling. triangular ridge. M & D marginal ridges Depressions: Central developmental groove M and D triangular fossae. M marginal developmental groove

22. The most charecteristic identifying feature of the max. first premolar Mesial marginal developmental groove

23. MAXILLARY FIRST PREMOLAR

25. PULP CAVITY MD section BL section Root canals: 2 root canals (B&L) but rarely 3 canals lingual canal is larger & more accessible Cervical cross sec. oval or kidney shaped Wide Narrow Pulp chamber:

26. MAXILLARY SECOND PREMOLAR

27. MAXILLARY SECOND PREMOLAR Chronology: • Enamel organ appearance: 8 mIU. • Beginning of calcification: 2-2¾y • Crown completed: 6 – 7y • Eruption: 10 – 12y • Root completed: 13 – 15y

28. Maxillary Second Premolar Buccal Lingual Mesial Distal Occlusal

29. Comparison between Maxillary First and Second Premolars Facial & Lingual Aspects • Geometric Shape of the Crown Trapezoid shape. The smallest of the uneven sidescervically.

30. Buccal Aspects Maxillary Second Premolar Maxillary First Premolar D M D M • B cusp is long and pointed • B cusp is short and not pointed • Shorter M slope than D • Longer M slope than D • Mesial contact : in the occ.1/3 while distally more cervically. • Mesial contact: in the middle1/3 while distally more cervical. • Cervical line curved rootwise. • Cervical line less curved.

31. Buccal Aspects Maxillary First Premolar Maxillary Second Premolar Less prominent B ridge Prominent B ridge Narrow cervical portion. Wider cervical portion. Longer root. Short root.

32. Lingual Aspects Maxillary First Premolar Maxillary Second Premolar • The L cusp is shorter by 1 mm than the B cusp. • The L and B cusps are nearly of same height. • 60% has 2 roots with • L root is shorter than B root and its apex is pointed. • Rarely has 2 roots • In case of two roots the L root is shorter & its apex more blunt.

33. Mesial and Distal Aspects • Geometric Shape of the Crown 4 5 Trapezoid in shape B L Smallest of the uneven sides:  occlusaly

34. Mesial Aspects Maxillary First Premolar Maxillary Second Premolar • B cusp is longer than L cusp by 1mm • The cusps are shorter & nearly at the same level. • The occlusal table is wide. • The occlusal table is narrow • Mesial marginal dev. groove in crown & deep canine fossa extending on root surface. • The crown surface is smooth & convex. The root has shallow dev. dep.

35. Mesial Aspects Maxillary First Premolar Maxillary Second Premolar MMR positioned more occlusal. MMR at the junction of M1/3 &Occ1/3 Contact area: At the occlusal third (OC dimension) and slightly buccal to midline (BL dimension) At the middle third (OC dimension) and slightly buccal to midline (BL dimension)

36. Distal Aspects Maxillary First Premolar Maxillary Second Premolar DMR more cervical than MMR DMR more cervical than MMR CA cervically positioned and more buccally than MCA. CA cervically positioned and more buccally than MCA. Smooth and convex surface except for a small flat area cervical to contact area. Smooth and convex surface.

37. Distal Aspects Maxillary First Premolar Maxillary Second Premolar One root and if 2 the bifurcation will be more apically. Root trunk is long as the bifurcation is near apical 1/3 Surface is smooth and convex except deeper DD in the middle of the root than mesially. Surface is smooth and convex except shallower DD on the root trunk than mesially.

38. Occlusal Aspect Maxillary First Premolar Maxillary Second Premolar hexagonal oval(less angular) B & L triangular ridges. B & L triangular ridges. Thin M & D marginal ridges Thicker M & D marginal ridges

39. Occlusal Aspect Maxillary First Premolar Maxillary Second Premolar Shorter Central dev gr. Long Central dev.gr. M marginal dev. groove Not present. Multiple supplemental grooves M and D fossae. M and D fossae. Thin marginal ridges Thick marginal ridges

40. MAXILLARY SECOND PREMOLAR

41. PULP CAVITYof maxillary second premolar MD section BL section Root canals: 2 root canals one B & one L Dentin island Lingual horn Cervical cross sec. Buccal horn (longer) Narrow(MD) Wide(BL) Oval or kidney

42. THANKS

43. بسم الله الرحمن الرحيم IN THE NAME OF ALLAH THE MOST GRACIOUS THE MOST MERCIFUL

44. MANDIBULAR FIRST PREMOLAR Chronology: • Enamel organ appearance: 7 miu. • Beginning of calcification: 1 ¾ - 2y • Crown completed: 5 – 6y • Eruption: 10 – 12y • Root completed: 12 – 13y

45. Mandibular First Premolar Buccal Lingual Mesial Distal No. of roots One root Occlusal

46. Geometric Outline of the Crown Facial and lingual aspects have trapezoid out line. The smallest of the uneven sides  cervically.

47. Outlines: • Mesial and distal outlines: are nearly concave Buccal Aspect Bucc. cusp pointed and long • Mesial(shorter) and distal cusp slopes: are also slightly concave • Contact areas: • Mesially and Distally: are nearly at the same level, just occlusal to the middle of the crown. M D • Cervical line: • convex root wise.

48. Surface anatomy of the crown Elevations: Buccal Aspect • The surface is convex with maximum convexity at C 1/3representingcervical ridge • The middle lobe is convex buccally forming prominent BUCCAL ridge. Depressions: • Shallow depressions are present mesial and distal to the buccal ridge.

49. Outline and Surface Anatomy of the Root Buccal Aspect The M and D outline of the root tapered to a pointed apex that curved distally(similar to canine but slightly shorter). The surface of the root is convex and smooth.

50. Lingual Aspect • Lingual convergence: • Ling. s. is narrower than buc. s. • Outlines: • M and D outlines are convex M D • The L cusp is short and small reaching 2/3 of the length of the B. cusp(has a pointed tip). Cervical line: is convex rootwise. • Surface Anatomy : Elevations: The lingual surface is convex with maximum convexity at middle 1/3 Depessions:ML developmental groove separating the MM ridge from the M slope of the L cusp.