Maxillary first molar

For my dental students

1. Maxillary First Molar Dr / Hesham Dameer

2. You have to know the following: 1- Discussion of the characteristics of the first maxillary molars 2- Description of the first maxillary molars a . Chronology. b. Geometric outline of the crown in different aspects . c. Outlines & Surface anatomy of the crown. d. Outlines & Surface anatomy of the root.

3. It is normally the largest tooth in the maxillary arch. It has 4 well developed functioning cusps and 1 supplemental or nonfunctioning cusp. This tooth has three roots which gives this tooth maximum anchorage. Maxillary First Molar

4. First evidence of calcification at birth Enamel completed 3-4 Y Eruption 6 Y Root completed 9 -10 Y Chronology

5. It has five surfaces It has 3 roots BUCCAL PALATAL MESIAL DISTAL OCCLUSAL

6. D M The geometric outline of the crown is trapezoidal with the short of the uneven sides cervically . The geometric outline

7. D M 3-Occlusal outline : Mesio-buccal cusp is broader , shorter and less sharp than disto-buccal cusp 1-Mesial & Distal Outline : M outline nearly straigh t till the contact area. D outline Convex till the contact area 2-Contacr Area : M contact area at the junction of the occlusal and middle 1/3 D contact area at the middle 1/3 Outline of the buccal Aspect

8. D M Depression Buccal groove may terminate by buccal pit . Cervical outline: Irregular and slightly convex toward the root Surface Anatomy of the B Aspect

9. The root trunk is approximately 4mm . The MB root is curved distally Its apex is rounded & slightly distal to the MB cusp tip. The DB root is curved mesiaally Its apex is tapered & on line with the DB cusp tip. The L root is appear longer than the 2 buccal roots M D The Roots M D 4mm MB root D B root

10. Buccal D M M D

11. No lingual convergence Mesial outline : Nearly straight & with the M slope of the ML cusp Distal outline : Convex and form semicircle with the distal slope of the DL cusp D M Outline of the Lingual Aspect D M Cusp outline : The ML cusp is the largest and longest cusp of this tooth. Its width is about 3∕5 of the MD diameter. 3∕5 2∕5 The DL cusp makes the remaining 2∕5 of the MD diameter. It is semicircular or spheroid in shape.

12. The Lingual dg cross between the L cusp s to enter the occlusal surface. Elevations The fifth cusp ( Carabelli ) appears on the surface over the ML cusp & approximately 2 mm. cervical to the cusp tip. Depression M D Surface anatomy of the crown Lingual surface

13. The lingual root is conical, with a wide base and a blunt apex & longer than the buccal roots. The lingual surface of the lingual root shows a shallow depression in the center. All three roots are visible from the lingual aspect. The lingual aspect The outline and surface anatomy of the roots

14. L B Trapezoidal in shape with the small uneven side occlusally proximal Aspect The geometric outline

15. L B Lingual outline: Convex with the crest of curvature at the middle 1/3.The lingual outline dips inward to illustrate the Carabelli tubercle . *The fifth cusp is on a line with the apex of the lingual root. *Buccal outline: * is convex with the crest of curvature located in the cervical third representing the cervical ridge with the presence of a shallow concavity might be noticed in the M 1∕3. The outline convex again till the B cusp Outline of the mesial Aspect L

16. The surface a natomy of the mesial aspect B L The cervical line is slightly convex crown wise. *It is a flat surface with presence of the contact area cervical to the junction of the O & M 1/3 and located bucally

17. The MB root It is broad occupying 2/3 of the root trunk It has a blunt apex which is on one line with the MB cusp. On the M. surface, there is mesial depression The Lingual root It is longer and narrower occupying 1/3 of the root trunk . It is a banana shaped & its L convexity is outside the crown dimension The fifth cusp is on a line with the apex of the lingual root. The root trunk is shorter than buccal aspect ( about 3mm ) . B L 2/3 The outline and surface anatomy of the root from the mesial aspect 3 mm

18. * Surface Anatomy The crown converges distally so , the buccolingual measurement of the crown distally is smaller than that mesially , thus part of the buccal surface can be seen distally. Distal MR curved more cervically exposing part of the occlusal surface distally . The cervical line is nearly straight .* It is similar to the mesial aspect with certain variations . The outline and surface anatomy from the distal aspect

19. The outline and surface anatomy of the root from the distal aspect * The root trunk shows the largest length distally reaching 5 mm or more. The distobuccal root is narrower than the other two roots.

20. 5mm 3mm * Distal Convergence * Convex distal surface * Distal MR curved cervically * Straight cervical line * Root trunk= 5mm * 3 roots are seen * Wider mesial surface * Flat mesial surface * Mesial MR less curved * Convex cervical line * Root trunk = 3mm * 2 roots are seen Mesial Aspect Distal Aspect

21. The crown converges distally and * buccally The ML cusp is the largest cusp; it is followed in point of size by the MB, DB, DL and fifth cusp . The Carabelli cusp may appear clearly in 50% & it may be indistinct or completely absent in 50% . B D L M Occlusal Aspect

22. It is Rhomboidal M D B L Note : * Distal & buccal convergence. * ML, BD angles are obtuse . *MB, DL angles are acute The geometric outline No lingual convergence

23. M D B L Elevations: *Oblique ridge between ML,DB triangular ridge *4 cusps with 4 triangular ridges and tubercle of Carabelli * MMR and DMR B M L D 1 2 3 4 The mesiolingual cusp is the largest followed in decreasing order of size by the mesiobuccal , distobuccal and distolingual cusp . The fifth cusp (tubercle), if present, is the smallest.

24. Remember Union of the triangular ridges of the mesiolingual and the distobuccal cusps forms an oblique ridge crossing the occlusal surface obliquely (characteristic of maxillary molars). This ridge is reduced in height in the center of the occlusal surface. MLC DBC MBC DLC Carabelli cusp

25. M D B L Depression: * 2 Minor fossae ( mesial and distal triangular fossae ) In the center of the central fossa is a central pit . D *2 major fossae ( central and distal ) *5 Developmental grooves Buccal , Central , transverse groove of oblique ridge , Distal oblique groove and Lingual groove . MLC DBC MBC DLC D M B L . . Central fossa Distal fossa Distal t . fossa Mesial t . fossa

26. Central , transverse groove of oblique ridge, Distal oblique groove, Buccal and Lingual groove . 5 Developmental groove

27. *2 major fossae ( central and distal ) * 2 Minor fossae ( mesial and distal triangular fossae ) *5 Developmental grooves 2 major fossae 2 Minor fossae So the depressed anatomical landmarks in upper first molar are M D

28. D M MLC DBC MBC DLC B L 5 Developmental grooves

29. Self-Evaluation Review Describe how can you diagnose the upper first molars What is the characteristic features of the mesial aspect of the upper 1 st molars ? All the teeth converge lingually except ……… which converge buccally . During extraction, the lingual root could be fractured due to its Ling convexity which is outside the crown dimension (banana shape). True False The cusps of the occlusal surface from bigger to smaller one are…….........., ……………, ……………, ……………., & ……… Discuss the surface anatomy of the occusal surface (elevations & depressions).

30. Wheeler’s Dental Anatomy, Physiology and Occlusion, 8th Ed .ASH and NELSON,W.B. Saunders Company, 2003. Dental Anatomy: Its Relevance to Dentistry, Julian BW, Rickne CS.5 th Ed,Williams& Wilkins, Baltimore, 1997.

31. Dent 131 skill 1