Tooth Morphology - Mandibular I premolar

1. Classification: Confidential
z
DR. DIVYAB
Department of Oral Pathology
& Microbiology
SRM DentalCollege,
Ramapuram,Chennai, India
MANDIBULAR FIRST PREMOLAR

2. Classification: Confidential
z
LOCATION

3. Classification: Confidential
z
FUNCTION
 Shearing of food with canines
 Mastication of food complementing with molars
 Support corners of mouth

4. Classification: Confidential
z
Nomenclature
 FDI
 Universal
 Zsigmondy

5. Classification: Confidential
z
Predecessor tooth
 Primary mandibular I molar

6. Classification: Confidential
z
Chronology
 I evidence of calcification – 1.5 to 2 years
 Crown completion – 5 to 6 years
 Eruption – 10 to 12 years
 Root completion – 12 to 13 years

7. Classification: Confidential
z
DEVELOPMENT
 4 lobes
1
2
3
4

8. Classification: Confidential
z
Measurements

9. Classification: Confidential
z
Characteristics resembling mandibular canine
 Buccal cusp is long and sharp and is the only occluding cusp.
 Buccolingual measurement - similar
 Occlusal surface slopes sharply lingually in a cervical direction.
 Mesiobuccal cusp ridge is shorter than the distobuccal cusp
ridge.
 Outline form of the occlusal aspect resembles the outline form of
the incisal aspect of the canine

10. Classification: Confidential
z
Characteristics resembling second mandibular premolar
 Outline of crown and root from the buccal aspect resembles that
of the second premolar.
 Curvatures of the cervical line mesially and distally are similar.

11. Classification: Confidential
z
Characteristic features of Mandibular I Premolar
 Single root
 Marked lingual inclination
 Lingual cusp smaller than buccal cusp
 More occlusally located distal contact area
 Root concavities found on mesial surface of root
 Endodontist enigma

12. Classification: Confidential
z
BUCCAL ASPECT
Slight concavity
Slightly mesial
Buccal ridge
Distal curvature

13. Classification: Confidential
z
Lingual Aspect
 Lingual taper
 Lingual cusp is short, less developed
 Most of the occlusal surface seen
 Mesiolingual developmental groove
 Grooves in mesial aspect of root
 Mesial marginal ridge shorter, lower than
distal marginal ridge
Pointed tip

14. Classification: Confidential
z
MESIAL ASPECT
 Crown – overhang above root trunk
 Mesiolingual developmental groove
 Occlusal surface
 Mesial surface of the root - shallow groove

15. Classification: Confidential
z
DISTAL ASPECT
 Distal marginal ridge - right angles
 No developmental groove

16. Classification: Confidential
z
OCCLUSAL ASPECT
 Middle buccal lobe - major bulk of the tooth crown.
 Buccal ridge - prominent.
 Mesiobuccal and distobuccal line angles are prominent, although
rounded.
 Broad distal contact areas
 Crown converges - triangular in form
 Marginal ridges - well developed.
 Lingual cusp is small

17. Classification: Confidential
z
OCCLUSAL ASPECT
 Diamond shaped
 Cusps
 Cusp Ridges – 4
 Triangular ridge – 2
 Marginal ridge – 2
 Fossa -2
 Groove - 5

18. Classification: Confidential
z
VARIATIONS
Crown oversized
Diminutive
Unusual formation of lingual cusp
Long lingual cusp
No lingual cusp
Very long curved root
VARIATIONS
VARIATIONS

19. Classification: Confidential
z
Clinical considerations
 Mesial, distal pits
 Periodontal problems
 Difficulty in instrumentation
 Dens evaginatus