Mandibular Premolars 3 PDF

ANATOMY OF PERMANENT MANDIBULAR Premolar Dr. Sandeep Gupta Oral Pathologist Distinguishing Characteristics Of Mandibular Premolars  Generally speaking : 1. The mand. 1st premolar has a longer crown and a shorter root than the 2nd premolar 2. The mand. 1st premolar is longer overall than the 2nd 2nd...

ANATOMY OF PERMANENT MANDIBULAR Premolar Dr. Sandeep Gupta Oral Pathologist Distinguishing Characteristics Of Mandibular Premolars  Generally speaking : 1. The mand. 1st premolar has a longer crown and a shorter root than the 2nd premolar 2. The mand. 1st premolar is longer overall than the 2nd 2nd 1st Buccal Aspect Of Mandibular Premolars 1. Crown Shape: (roughly trapizoidal)  1st: Nearly symmetrical except for a shorter mesial cusp ridge and a distal bulge of the crown Buccal Aspect Of Mandibular Premolars 2nd 1st 1. Crown Shape: (roughly pentagonal)  2nd premolar: Buccal cusp is less pointed and cusp slopes are less steep than on the mandibular 1st premolar Buccal Aspect 2. Notches on Cusp Ridges:  Notches often seen on mesiobuccal cusp ridge in mandibular 1st premolars  Notches often seen on distobuccal cusp ridge in mandibluar 2nd premolars 2nd 1st Buccal Aspect 3. Cervical Lines: 2nd  The cervical line of the mandibular 1st premolar is more rounded mesiodistally, while that of the 2nd premolar is more flat 1st Buccal Aspect 4. Contact Areas - Mesial:  1st and 2nd premolar - near junction of occlusal and middle third Buccal Aspect 6. Contact Areas - Distal:  2nd premolar has a distal contact located more cervical than the mesial contact area, as is usually the case with posterior teeth Lingual Aspect Of Mandibular Premolars 1. Crown Shape:  Mandibular first premolar crown tapers (converges) to the lingual (narrower on lingual side that buccal) Lingual Aspect Of Mandibular Premolars 1. Crown Shape:  Mandibular 2nd premolar with 1 lingual cusp, crown tapers to lingual  Mandibular 2nd premolar with 2 lingual cusps, crown is as wide or wider mesiodistally than the buccal Lingual Aspect 2. Cusp Size and Shape: M D  Mandibular 1st premolar lingual cusp is small and pointed  Most of the occlusal surface can be seen from this aspect Lingual Aspect 2. Cusp Size and Shape:  Mandibular 2nd premolar with 1 lingual cusp:  Lingual cusp is smaller than buccal cusp, but larger than lingual cusp of 1st premolar Lingual Aspect 2. Cusp Size and Shape:   Mandibular 2nd premolar with 2 lingual cusps: ML ML cusp is larger than the DL cusp, with the Lingual groove between them and onto the lingual crown surface M DL D Lingual Aspect 3. Marginal Ridges:  Mandibular 1st premolar: M  Only tooth in the mouth where the mesial marginal ridge is more apical than the distal marginal ridge D Lingual Aspect 3. Marginal Ridges:  Mandibular 2nd premolar:  Mesial marginal ridge is more occlusal than the distal marginal ridge (as found in all other teeth) M D Lingual Aspect 4. Mesiolingual Groove:  Frequently seen on Mandibular 1st premolar only Proximal Aspect Of Mandibular Premolars Crown Shape - Rhomboid:  The crowns of both premolars tilt lingually, but the mandibular 1st premolar tilts more lingually than the mandibular 2nd premolar Mesial View Proximal Aspects 1st Premolar Proximal aspects have Mesial Rhomboid shape With narrow occlusal table prominent lingual inclination Distal  Outlines of proximal aspects Mesial Aspect Distal Aspect Buccal outline is convex with maximum convexity at C 1/3 representing cervical ridge. Lingual outline is convex with maximum convexity at middle1/3 Cervical line curves occlusally and less curved distally Mesial Aspect Distal Aspect Occlusal margin: The two cusps are not on the same level The lingual cusp is shorter by 1/3 length of crown The Buccal cusp centered over the root. This is due to the prominent lingual inclination. The Lingual cusp tip in line with lingual border of the root. Mesial Aspect B L Mesial Marginal Ridge(MMR) inclined from B to L surface parallel to B cusp ridge. Distal Aspect Distal Marginal Ridge(DMR) is straight and at right angle to the axis of the tooth. DMR is more occlusal than MMR (unique characteristic of this tooth). Mesial Aspect  Proximal surface anatomy Distal Aspect M & D surfaces are smooth & convex except for a concave area cervical to contact area. Mesio Lingual developmental groove present at the junction of Lingual and Mesial surfaces.  Outline and surface anatomy of the root Mesial Aspect Distal Aspect B & L outlines are nearly straight cervically then taper to apically to a pointed apex The mesial surface of root is more convex The root surface is smooth and flat with deep developmental groove Proximal Aspect 2nd Premolar Height of Contour: Buccal = junction of cervical and middle 1/3 Lingual = middle 1/3 Proximal Aspect 2nd Premolar  Distolingual cusp is smaller so more of the occulasal surface is seen from distal aspect. Distal Mesial Proximal Aspect 2nd Premolar Root Depressions: Distal  Mandibular 2nd premolar:  Have a distal root depression in the middle third of the root, but NO mesial depression Mesial Occlusal Aspect Of Mandibular First Premolar 1. Outline: – Have much variation in occlusal morphology M D – Outline is not symmetrical (more bulky on the distal) Occlusal Aspect Of Mandibular First Premolar 1. Outline: – Often appears as if the mesial side has been pushed inward (mesiolingual corner) M D Occlusal Aspect Of Mandibular First Premolar 1. Outline: – Tip of the buccal cusp is near the center from occlusal view – Lacks a prominent buccal ridge – Cusp ridges are nearly straight lines M D Occlusal Aspect Of Mandibular First Premolar 1. Outline: – Crown is somewhat diamond shaped converging lingually – Shape of crown is asymmetrical M D Occlusal Aspect Of Mandibular First Premolar 1. Outline: – Mesial and distal marginal ridges may converge lingually Occlusal Aspect Of Mandibular First Premolar 2. Ridges, Fossae, Grooves: – Due to size of cusp, the buccal triangular ridge is long – Joins the shorter lingual triangular ridge – Often may meet smoothly and form a uninterrupted transverse ridge Occlusal Aspect Of Mandibular First Premolar 2. Ridges, Fossae, Grooves: – The transverse ridge may be crossed by a shallow central groove extending from mesial to distal fossa – This is rare Occlusal Aspect Of Mandibular First Premolar 2. Ridges, Fossae, Grooves: – Possess a mesial and distal fossa – Both are irrregular or circular, not triangular – Both possess pits – Distal fossa is usually larger and/or deeper D Occlusal Aspect Of Mandibular Second Premolar 1. Outline - Two-cusp version: – Crown is round or oval shaped with a square occlusal table Occlusal Aspect Of Mandibular Second Premolar 1. Outline - Two-cusp version: – There is slightly more bulk in the mesial half buccolingually than in the distal half Occlusal Aspect Of Mandibular Second Premolar 2. Ridges, Fossae, Grooves - Two-cusp version: – Lingual cusp smaller than buccal cusp – Possess more supplemental grooves than first premolars – Also has a smaller triangular ridge Occlusal Aspect Of Mandibular Second Premolar 2. Ridges, Fossae, Grooves - Two-cusp version:  Possess a curved central groove with no lingual groove  This groove can be fairly straight D Occlusal Aspect Of Mandibular Second Premolar 1. Outline - Three-cusp version: – When lingual cusps are large, the occlusal surface is broader on the lingual Occlusal Aspect Of Mandibular Second Premolar 1. Outline - Three-cusp version:  Often have greater bulk buccolingually in the distal not the mesial  The ML cusp is usually larger than the DL cusp ML DL Occlusal Aspect Of Mandibular Second Premolar 2. Ridges, Fossae, Grooves - Three-cusp version:  Possess three triangular ridges converging toward the central fossa 1 2  There is no transverse ridge 3 Occlusal Aspect Of Mandibular Second Premolar 2. Ridges, Fossae, Grooves - Three-cusp version:  Has a central fossa (unique) shifted towards the distal  Lacks a central groove  Mesial groove present M D C Occlusal Aspect Of Mandibular Second Premolar 2. Ridges, Fossae, Grooves - Three-cusp version:  Possess a lingual groove that separates the two lingual cusps  This groove completes the Y-shaped occlusal groove pattern Thank You