Mandibular 2nd premolar

Mandibular second premolar
By Prof Dr Mohamad Helal
Faculty of Dentistry, Mansoura University

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

2. Mandibular 2 nd premolar By: Prof Dr Mohamad Helal Head of oral Biology Department

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4. THE PREMOLARS

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

6. 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.

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

8. Generally: The Mandibular 2nd premolar has a larger crown and longer root than lower one. The1st premolar like the canine while 2 nd premolar like small molar from the occlusal 3.They are similar shape from buccal surfaces

9. Chronology: First evidence of calcifi . 2 ¼ -2 ½ y Enamel completed 6-7 y Eruption 11-12y Root completed 13-14y

10. Buccal aspect: Like buccal surface of lower 1 st premolar? Trapezoidal shorter cervically Mesial outline: slightly concave Distal outline: slightly concave Contact areas: broad and wide contact located at the same level occlusal to midway cervico-occlusally , the mesial one is more cevically . Cusp: shorter and broader than 1 st one with mesial inclined plane longer then distal one.

11. Lingual aspect Buccal aspect

12. Lingual aspect: Two type : A-Square type (three cusps) -Two lingual cusps with lingual groove B-Round type ( two cusps) - One cusp ligually

13. Three cusp type Two cusp type

14. 2 nd 1st Buccal surfaces

15. Mesial aspect: difference between 1 st and 2 nd premolars

16. Distal aspect

17. Occlusal aspect 2 3 1

18. Geometric outline of the crown Facial and lingual aspects have trapezoid shape But wider cervically than 4. Comparison Between Mandibular First and Second Premolars

19. Facial Outlines and surface anatomy Crown is smaller & B cusp is longer & pointed Prominent B ridge Less prominent B ridge Crown is larger & B cusp is shorter and less pointed Root: Shorter, narrower with pointed apex Root: longer, broader, with blunt apex Mandibular First Premolar Mandibular Second Premolar

20. Lingual outline and surface anatomy The lingual surface is convex with maximum convexity in middle 1/3(center of crown) The L cusp is short and small reaching 2/3 the crown length and has a pointed tip. ML developmental groove at the ML line angle. Two cusp type L cusp is shorter and smaller than B cusp but larger than of 4 The surface is convex with maximum convexity in Occ.1/3. No MLDG Mandibular First Premolar Mandibular Second Premolar Ling. s. not so narrow as in 1 st premolar M D D M

21. Three cusp type: ML cusp is longer and larger than DL cusp. They both shorter than B cusp and less pointed. D M The surface convex with maximum convexity at occ.1/3. The L developmental groove between the 2 ling. cusps No ling. convergency .

22. Proximal outlines Rhomboid in shape with narrow occlusal table. Prominent lingual inclination Rhomboid in shape with wider to some extent occlusal table. Lingual inclination less prominent Mandibular First Premolar Mandibular Second Premolar The crown is wider BL The crown is narrower BL

23. Maximum convexity at M1/3 Maximum convexity at O 1/3 B cusp tip on line buccal to the root axis. The mesial and distal marginal ridges are straight L cusp is shorter and smaller than B cusp but larger than that of 4 The B cusp centered over the root. The L cusp is short and small reaching 2/3 the crown length The mesial MR is oblique while distally is straight Mandibular First Premolar Mandibular Second Premolar The root is wider BL

24. Three Cusp Type of Mandibular Second Premolar ML cusp is shorter than the B cusp & longer and larger than DL cusp. DL cusp is shorter and smaller than ML cusp. Both are seen from this aspect. Both lingual cusps are shorter than the buccal cusp and less pointed Mesial Aspect Distal Aspect Develop. depression Cerv. line: slightly curved. Cerv. line: nearly straight.

25. Occlusal Aspect Two cusp type Diamond-shaped . Lingual convergence is sharp. The outline is round Slight lingual convergence Three cusp type The outline is square Mandibular First Premolar Mandibular Second Premolar U- shaped H - shaped M D The 3 cusps are well developed M D

26. Surface Anatomy of Occlusal Aspect: Elevations: B & L triang . ridges form a transv . ridge. M & D marginal ridges Lower 5 Two cusp type Lower 4

27. Depressions: Shallow central devel. groove M(oval) and D(round) fossae. Mesiolingual devel. gr. Central devel. groove extending MD across the occ. surface, over the transv. ridge. M and D fossae: Circular. The D fossa is larger than the M one Lower 5 Two cusp type Lower 4 . . M D M D

28. Type

29. Elevations & Depressions Each cusp has triang. ridge that converge toward a central fossa, which has cent. pit. M & D marginal ridges are well marked . No central devel . gr. or transv . ridge Three cusp type Lower 5 Three devel. gr.(M,D, & L) radiate from the cent. Pit : Y-shaped. The D triang. fossa is smaller than the M one. M D

30. Type

31. MANDIBULAR SECOND PREMOLAR 3 cusp type 2 cusp type

32. PULP CAVITY MD BL Cross sec. at the cerv. line round or oval www.oralbiology.azhar.edu.eg

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