Permanent Maxillary 1st premolar

Permanent Maxillary 1st premolar

1. PERMANENT MAXILLARY 1 ST PREMOLAR By Dr. Abhishek Solanki

2. INTRODUCTION Premolars are so named because they are placed between the anterior teeth and the molars (pre = before) Premolars assist canines & molars in tearing and chewing food Have two cusps (bicuspid) & two roots (buccal & lingual) Eruption : at 10-11 years

3. TOOTH NUMBERING Universal : #5 , #12 Z-P : 4 4 FDI : 14, 24

4. CHRONOLOGY First evidence of calcification :1.5 – 1.75 yrs Enamel Completion : 5-6 yrs Eruption : 10-11 yrs Root completion : 12-13 yrs

5. DIMENSIONS (in mm) Cervico-occlusal Length of Crown 8.5 Length of Root 14 Mesiodistal Diameter of Crown 7 Mesiodistal Diameter of Crown at Cervix 5 Labio- or Bucco-lingual Diameter of Crown 9 Labio- or Bucco-lingual Diameter of Crown at Cervix 8 Curvature of Cervical Line—Mesial 1 Curvature of Cervical Line—Distal

6. Buccal Aspect Crown : Pentagonal shaped Crown closely resembles to maxillary canine and second premolar Mesial margin joins the mesio-occlusal slope to create an obtuse mesio-occlusal angle

7. Contour of the mesial outline is concave from the contact area to the cervical line The mesial slope of the buccal cusp is longer than distal slope, which is the opposite of canine Disto-occlusal angle is a little less prominent and the cervical concavity is not as deep

8. Occlusal margin of this tooth is, similar to the incisal margin of the maxillary canine Buccal ridge Mesio-buccal & distobuccal developmental depressions on each side of buccal ridge

9. Lingual Aspect The crown tapers towards the lingual aspect The lingual cusp is shorter than the buccal cusp The lingual cusp is smooth from the cervical portion to the area near the cusp tip

10. The cusp tip is pointed with mesial and distal slope meeting at an angle of about 90 degrees Small portion of the buccal cusp can be seen from this aspect Smoothly convex in all directions There is no clearly defined lingual ridge

11. Mesial and distal outlines are normally somewhat convex & shorter than the same outlines of the buccal surface Lingual cusp tip is not as sharply pointed as the buccal cusp tip The mesio-occlusal slope is shorter than the disto-occlusal slope

12. Mesial Aspect From the mesial and distal aspect both the buccal and lingual cusps are visible A well developed mesial marginal ridge and a mesial marginal developmental groove is present In the middle of the mesial surface is the mesial developmental depression which continues beyond the cervical line

13. Mesial concavity Shape of the mesial surface is trapezoidal Buccal outline is generally convex , with the height of contour in the cervical third Lingually the outline takes the form of an even arc, with the height of contour in the middle third

14. Occlusal margin is irregularly concave and the majority of it is made up of the mesial marginal ridge. A prominent mesial marginal groove is usually present indenting the occlusal margin almost two-thirds of the way from the buccal to the lingual outline.

15. Distal Aspect There is no developmental depression or groove on this aspect, instead it is convex at almost all points The curvature of the cervical is less on this aspect The contact area is near the junction of occlusal and middle third distal is remarkably similar to the mesial surface, although it is slightly shorter occluso-cervically.

16. Lingual margin is almost symmetrical & is quite convex, especially in middle third, where height of contour is located Occlusally , distal is similar to mesial aspect, except that marginal ridge is located at a more cervical level There is normally no marginal groove

17. Occlusal Aspect Within cusp ridges and marginal ridges the following are present TBC & TLC : Tip of Buccal & Lingual cusp BTR & LTR : Buccal & Lingual Triangular ridge DBDG: disto-buccal developmental groove DTF & MTF : Mesial & Distal triangular fossa CG : Central groove

18. outline of crown can be described as hexagonal or six-sided and it is wider buccolingually than mesiodistally prominent buccal ridge is primary contributor to generally convex buccal outline lingual margin is evenly convex, almost in a semicircle Proximal margins are relatively straight & they converge toward lingual

19. Root Most Maxillary first premolars have 2 roots, but one and three roots can also be seen Two roots : buccal and lingual Buccal portion of the root resembles canine

20. The root when viewed from the proximal side shows a big trunk and bifurcation area from where the buccal and lingual root separate A developmental depression is seen on the mesial aspect of the trunk TRUNK

21. REFERENCES CONCISE DENTAL ANATOMY & MORPHOLOGY : JAMES L FULLER DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION: WHEELER’S TEXTBOOK OF DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION: RASHMI GS (PHULARI ) INTERNET