12-Mandibular Premolars-bg.ppt

1. Permanent Mandibular Premolars

2. Mandibular First Premolars Initial items of interest • First premolar is always smaller than the second premolar • Faciolingually it is as wide as the mandibular canine • Transitional tooth that resembles the mandibular canine, but with 2 cusps

3. Permanent Mandibular Premolars Class Traits & Key Considerations: • Have a single, well-developed facial cusp, however the lingual cusp or cusps may vary in size and development and are never as well developed as the facial cusp. • The crowns, from the occlusal aspect, are more nearly the same diameter faciolingually and mesiodistally (the faciolingual measurement is greater than mesiodistal measurement by only 1.0 mm or less). • Facial profiles, viewed from the proximal aspect, are significantly inclined lingually from the height of contour (cervical ridge) to the tip of the facial cusp. • Lingual height of contour is situated more occlusally much nearer the tip(s) of the lingual cusp(s). This is still considered to be the middle third of the crown when compared to the crown’s overall occlusocervical measurement. However some text books reference the lingual height of contour as being in the occlusal 1/3 of the crown because it is referencing an OC measurement from the tip(s) of the lingual cusp(s) to the cervical line. • The mandibular first premolar and the 3-cusp variety mandibular second premolar do not share a great deal of morphological similarity. The mandibular 1st premolar and the 2-cusp variety mandibular 2nd premolar demonstrate significant lingual convergence. The 3-cusp variety mandibular 2nd premolar may demonstrate lingual divergence, that is to say the mesiodistal measurement of the lingual surface may be greater than that of the facial surface.

4. Mandibular First Premolars Calcification and Eruption • Calcification begins………………..2 years • Crown completed………………...5-6 years • Eruption…………………………...10-12 years • Root completed………………….12-13 years

5. Permanent Mandibular Premolars – Type Traits Aspect First Premolar Second Premolar Facial > Crown not as bilaterally symmetrical > Crown bilaterally symmetrical Lingual Entire facial profile visible Almost entire occlusal surface visible Lingual cusp much smaller and lower than facial cusp >None of facial profile visible >Little if any of occlusal surface visible >Facial and lingual cusps almost equal in height Mesial > Occlusal plane tilted lingually > Transverse ridge links tips of the facial and lingual cusps > Mesial marginal ridge inclines cervically about 45° > Mesiolingual groove >Occlusal plane horizontal > No transverse ridge (except 2-cusp variety) > Mesial marginal ridge is horizontal > Lingual groove separating lingual cusps (3-cusp variety)

6. Permanent Mandibular Premolars – Type Traits Aspect First Premolar Second Premolar Occlusal >Occlusal crown outline diamond shaped > Mesial and distal profiles converge lingually > Occlusal table triangular in outline > Facial cusp more than twice the size of lingual cusp > Mesial marginal ridge shorter and less prominent than distal marginal ridge > Absence of Y pattern formed by grooves > No pit >Occlusal crown outline square or oval >Mesial and distal profiles straight and parallel >Occlusal table square in outline >Facial and lingual cusps nearly equal in size >Mesial and distal marginal ridges about same length and prominence >Main grooves form Y pattern (3- cusp) >Central pit

7. Permanent Mandibular First Premolar – Introductory Points •The mandibular 1st premolar is viewed as a transitional tooth resembling the mandibular canine but with two cusps. The facial cusp is much larger than the lingual cusp that may even resemble a cingulum. •The occlusal table slopes cervically in a lingual direction. It is the only posterior tooth with this trait. •When viewed from the facial aspect, the tooth has near symmetrical mesial & distal profiles. However, there is a prominent mesial “bulge”. •The mesiolingual groove produces a slight concavity at about the mesiolingual line angle of the tooth. •The occlusal crown outline is diamond shaped. The occlusal table is triangular. •There is a prominent transverse ridge from the facial cusp tip to the lingual cusp. •The MMR is less distinct than the DMR and slopes lingually at or about a 45° angle (approximates the DMR of the abutting mandibular canine).

8. Permanent Mandibular First Premolar Facial View

9. Permanent Mandibular First Premolar Facial View >Nearly symmetrical bilaterally >Pointed cusp >Mesial cusp ridge shorter than distal >Slight vertical depressions

11. Permanent Mandibular First Premolar Facial View >Nearly symmetrical bilaterally >Pointed cusp >Mesial cusp ridge shorter than distal >Slight vertical depressions M D

13. Permanent Mandibular First Premolar Lingual View

14. Permanent Mandibular First Premolar Lingual View >Tapers lingually >Occlusal table slants cervically >Lingual cusp – cingulum qualities >Lingual cusp tip – 2/3’s measurement >Pointed & centered lingual cusp tip >Mesiolingual groove >Horizontal depressions

21. Permanent Mandibular First Premolar Mesial View >Rhomboid crown outline >Facial cusp tip centered over root >Lingual cusp tip in line with lingual root outline >Facial contour – facial cervical ridge >Lingual contour – middle 1/3 >Facial outline is completely convex >Long facial, short lingual triangular ridges >Central groove is lingually positioned >45 degree angle to mesial marginal ridge >Mesiolingual groove present >Contact area lines up with facial cusp tip >Cervical line curves about 1.0 mm.

34. Permanent Mandibular First Premolar Distal View >Essentially the reverse of the mesial view >Distal marginal ridge is more horizontal than mesial marginal ridge >Distal marginal ridge is more superiorly positioned than the mesial marginal ridge >No presence of groove crossing between the distal cuspal ridge of the lingual cusp and the distal marginal ridge >Contact area is centered faciolingually and occlusogingivally >Less curvature to the cervical line

41. Permanent Mandibular First Premolar Occlusal View >Diamond-shaped occlusal outline >Triangular-shaped occlusal table >Long facial cusp triangular ridge >Short lingual cusp triangular ridge >Triangular ridges form a transverse ridge >Linear mesial groove in mesial fossa continuous with mesiolingual groove >”Comma” shaped groove in distal fossa >Central groove is lingually-positioned

54. Mandibular First Premolars Key Points • Similarities to the canine – Lingual cusp short or missing • Marginal ridge form – 45 degrees – Distal is taller • Angle of occlusal surface • Mesiolingual groove

55. Mandibular First Premolars Occlusal Anatomy • Diamond-shaped outline • Triangular occlusal table • Prominent transverse ridge • No central pit

56. Permanent Mandibular Second Premolar • Charles J. Arcoria, DDS, MBA

57. Mandibular Second Premolars Initial items of interest • Second premolar is always larger than the first premolar • This tooth has qualities that are similar to a mandibular molar • Can exhibit either a 3-cusp or 2- cusp variety

58. Mandibular Second Premolars Calcification and Eruption • Calcification begins……………….2 years • Crown completed……………….6-7 years • Eruption………………………….11-12 years • Root completed……………….13-14 years

59. Mandibular Second Premolars Facial View • Crown outline form is trapezoidal or pentagonal • Facial cusp shorter and more blunt than facial of mandibular first premolar • Contacts located nearer the occlusal outline than on the mandibular first premolar • Crown does not taper toward the cervical line, like the mandibular first premolar • Mesial cuspal ridge is shorter than the distal cuspal ridge • Facial cusp tip is slightly mesial to long axis bisector • Distal cuspal ridge has a notch • Root surface is convex • Root tip has distal orientation

64. Mandibular Second Premolars Facial View • Crown outline form is trapezoidal or pentagonal • Facial cusp shorter and more blunt than facial of mandibular first premolar • Contacts located nearer the occlusal outline than on the mandibular first premolar • Crown does not taper toward the cervical line, like the mandibular first premolar • Mesial cuspal ridge is shorter than the distal cuspal ridge • Facial cusp tip is slightly mesial to long axis bisector • Distal cuspal ridge has a notch • Root surface is convex • Root tip has distal orientation D M

69. Mandibular Second Premolars Lingual View • 3-cusp variety has 2 lingual cusps with a lingual groove between them • Lingual groove is distally positioned • Mesiolingual cusp tip is 1.5 mm shorter than facial cusp tip • Distolingual cusp tip is 2.0 mm shorter than facial cusp tip • Mesiolingual cusp is wider than the distolingual cusp • Spheroidal lingual surface contour • Crown has almost the same mesiodistal width on the lingual surface, as it does on the facial surface • Convex root surface • Root apex has distal orientation D M

74. Mandibular Second Premolars Lingual View • 3-cusp variety has 2 lingual cusps with a lingual groove between them • Lingual groove is distally positioned • Mesiolingual cusp tip is 1.5 mm shorter than facial cusp tip • Distolingual cusp tip is 2.0 mm shorter than facial cusp tip • Mesiolingual cusp is wider than the distolingual cusp • Spheroidal lingual surface contour • Crown has almost the same mesiodistal width on the lingual surface, as it does on the facial surface • Convex root surface • Root apex has distal orientation

78. Mandibular Second Premolars Mesial View • Facial cervical ridge is the height of contour • Lingual height of contour is in middle 1/3 • Facial cusp tip is facial to long axis of tooth • Mesiolingual cusp tip is near the lingual crown outline and continuous with lingual outline of root • Mesial marginal ridge is higher, occlusally, than on the mandibular first premolar and more horizontal • None of the distolingual cusp can be seen from the Mesial view • Height of curvature of the cervical line is about 1.0 mm

85. Mandibular Second Premolars Distal View • Distal marginal ridge is slightly lower than the mesial marginal ridge • More of the occlusal surface can be viewed from the distal, as opposed to the mesial view • Long portion of the triangular ridge of the facial cusp is evident from this view • Mesiolingual cusp can be see over the height of the distolingual cusp • Lingual height of contour is in the occlusal 1/3 • Cervical line is almost flat across

92. Mandibular Second Premolars Occlusal View • Facially located contact areas are also wide faciolingually • Rounded facial outline with little evidence of 3 lobes • Nearly square occlusal outline with little lingual convergence seen • Lingual mesiodistal measurement may be slightly wider than facial mesiodistal measurement. Only mandibular tooth that has this. • Straight lingual outline with indentation at lingual groove • 3 distinct cusps in decreasing size: Facial, Mesiolingual, Distolingual • Facial cusp is slightly mesial and facially positioned • Lingual cusp tips are close to lingual outline of occlusal table • Mesiolingual cusp is wider than distolingual cusp • Right angle connections between the cuspal ridges and marginal ridges • 3-cusp variety does not have a transverse ridge • Central groove has a mesial and distal component and is lingually positioned • Outline of developmental grooves is a “Y” shaped pattern • Central pit in center of occlusal table D M

95. Mandibular Second Premolars Occlusal View • Facially located contact areas are also wide faciolingually • Rounded facial outline with little evidence of 3 lobes • Nearly square occlusal outline with little lingual convergence seen • Lingual mesiodistal measurement may be slightly wider than facial mesiodistal measurement. Only mandibular tooth that has this. • Straight lingual outline with indentation at lingual groove • 3 distinct cusps in decreasing size: Facial, Mesiolingual, Distolingual • Facial cusp is slightly mesial and facially positioned • Lingual cusp tips are close to lingual outline of occlusal table • Mesiolingual cusp is wider than distolingual cusp • Right angle connections between the cuspal ridges and marginal ridges • 3-cusp variety does not have a transverse ridge • Central groove has a mesial and distal component and is lingually positioned • Outline of developmental grooves is a “Y” shaped pattern • Central pit in center of occlusal table D M F

106. Mandibular Second Premolars Key Points • Y-type – 3 cusps/5 lobes – Developmental depressions • U-type – 2 cusps/4 lobes • H-type – 2 cusps/4 lobes

107. Y-Type Second Premolar Occlusal Anatomy • Positive Anatomy – Facial Pentagonal outline – Nearly square occlusal table – Cusp size: F, ML, DL – Cusps visible from which view? – No Transverse ridge • Negative anatomy – Grooves – Pits – Distal cuspal ridge of facial cusp is notched

108. Mandibular Second Premolars Key Points • Root anatomy – Shorter than canine – Mild depressions – Usually one canal • Contact areas (slightly facial) • Geometric shapes • Heights of contour – Facial surface (cervical 1/3) – Lingual surface (middle or occlusal 1/3)

109. Anomalies • Missing lingual cusp on mandibular first premolar • Smaller second premolar • Missing second premolar

110. Mandibular Premolars Comparison and Contrast •Cusp tip outlines •Similar crown shapes •Similar root lengths and both shorter than the canine •Lobe depressions 1st 2nd Facial View

111. Mandibular Premolars Comparison and Contrast Lingual view • Taper • Number of cusps • Cusp outlines • Cusp heights 1st 2nd

112. Mandibular Premolars Comparison and Contrast Mesial view • Position of cusp tips • Angle of marginal ridges • Angle of triangular ridges • Mesiolingual groove • Curvature of cervical lines 1st 2nd

113. Mandibular Premolars Comparison and Contrast • Occlusal view – Overall size – Geometric shapes – Cusps: 2 vs. 3 – Grooves – Fossae, pits – Taper – Transverse ridge 1st 2nd

114. The End

12-Mandibular Premolars-bg.ppt

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12-Mandibular Premolars-bg.ppt