Maxillary Permanent Molars: Anatomy

Maxillary Permanent Molars

• Maxillary permanent molars are largest in the upper teeth.
• The width of the maxillary permanent molar crown is greater than its length.
• Root length is double the crown length.
• These teeth are cheek teeth not preceded by primary teeth.
• Upper molars typically feature three roots.
• The largest tooth is located in the upper maxillary arch.

Anatomical Landmarks: Buccal Aspect

• The buccal surface is convex.
• The buccal groove may terminate in a buccal pit or fade into two short grooves.
• A cervical ridge is present.

Occlusal and Cervical Outlines

• The mesio-buccal cusp is broader, shorter, and less sharp than the disto-buccal cusp.
• The mesial and distal slopes of the mesiobuccal cusp meet at an obtuse angle.
• The mesial and distal slopes of the distobuccal cusp meet at a right angle.
• The cervical outline is irregular and slightly convex towards the root.

Geometric Outline: Buccal Aspect

• The geometric outline is trapezoidal, with a small uneven side cervically.
• The mesial outline is nearly straight until the contact area.
• The contact area is located at the junction of the occlusal and middle third.
• The distal outline is convex until the contact area is at the middle third.

Lingual Aspect Features

• The lingual surface is nearly equal to or slightly wider than the buccal surface.
• There is no lingual convergence.
• The mesial outline is nearly straight, forming a corner with the mesial slope of the ML cusp.
• The distal outline is convex, forming a semicircle with the distal slope of the DL cusp.

Occlusal and Cervical Outlines: Lingual

• The ML cusp is the largest and longest cusp.
• The DL cusp is spheroidal.
• The cervical outline is irregular and slightly convex toward the root.

Anatomical Landmarks: Lingual Aspect

• A convex lingual surface is present.
• The Cusp of Carabelli is present in 50-70% of individuals on the lingual surface of the ML cusp.
• The Cusp of Carabelli is approximately 2mm from the tip of the ML cusp.
• It is outlined by a developmental groove.
• A lingual developmental groove is present.

Geometric Outline: Mesial Aspect

• The geometric outline is trapezoidal with a small uneven side occlusally.
• The buccal outline is convex at the cervical 1/3, denoting the cervical ridge.
• The buccal outline is concave at the middle 1/3, denoting the termination of the buccal developmental groove.
• The buccal outline is convex at the occlusal 1/3, representing the circumscribed MB cusp.

Lingual Outline: Mesial Aspect

• The lingual outline is convex, with the crest of curvature at the middle 1/3.
• The lingual outline dips inward to illustrate the tubercle.

Occlusal and Cervical Outlines: Mesial Aspect

• The occlusal outline is represented by ML and MB cusps.
• The Irregular MMR curves cervically and may exhibit small tubercles.
• It is concave buccally and convex mesially.
• The cervical outline is irregular and convex occlusally.
• The mesial contact area is at the junction between the middle and occlusal 1/3, buccal to the center.

Distal vs. Mesial Aspects

• The distal aspect features distal convergence.
• A convex distal surface exists on the distal aspect.
• The distal marginal ridge (MR) is shorter and located more cervically.
• The mesial aspect has a wider mesial surface.
• The mesial aspect features a flat mesial surface and a mesial marginal ridge that is less curved.

Root Trunk Measurements

• On the distal aspect, the root trunk measures 5mm.
• On the mesial aspect, the root trunk measures 3mm.
• Three roots are visible from the distal aspect.
• Two roots are visible from the mesial aspect.
• The cervical line is straight on the distal aspect but convex occlusally on the mesial aspect.

Geometric Outline: Occlusal Aspect

• The geometric outline of the occlusal aspect is rhomboidal.
• Disto-buccal convergence is noted.
• The ML and BD angles are obtuse.
• The MB and DL angles are acute.

Anatomical Landmarks: Elevations

• There are typically 4 cusps with 4 triangular ridges and a tubercle.
• The ML cusp has 2 triangular ridges.
• The size order of the cusps from largest to smallest is: ML > MB > DB > DL.
• An oblique ridge exists between the ML and DB triangular ridges within the trigon.
• The MMR and DMR are also key features.

Anatomical Landmarks: Depressions

• Two major fossae are present: central and distal.
• Two minor fossae exist: mesial and distal triangular fossae.
• Developmental grooves include the Buccal, Central, transverse groove of oblique ridge, Distal oblique groove, and Lingual groove.
• The Cusp of Carabelli groove is also a notable depression.

Root Characteristics (Buccally)

• The root trunk measures 4 millimeters.
• Three roots are seen from the buccal aspect.
• The axes of the roots are inclined distally.
• A deep developmental groove extends on the root trunk.

Distinct Lingual Root Features

• The lingual root is the longest.
• It has a blunt apex and a distal depression.

Distal vs. Mesial Aspects of Roots

• The distal root trunk is 5mm, while the mesial root trunk is 3mm.
• Three roots are seen from the distal view, and two from the mesial.
• The lingual banana shape of the roots is visible.

Elevations and Depressions

• DMR: Distal Marginal Ridge
• Oblique Ridge
• Distal Linear Fossa
• Central Fossa
• Buccal Groove
• Mesial Triangular Fossa
• Lingual Groove

Differences between Maxillary Permanent Molars

Molar Roots

• Less divergent and the lingual root is straighter

Variations

• The third molar in particular may have 3 or 4 cusps
• Rhomboidal or Heart occlusally
• Roots may be fused

Pulp Cavity (1st Molar)

• The pulp chamber is broader bucco-lingually than mesio-distally.
• It is quadrilateral in shape.
• There is a pulp horn beneath each cusp, and the floor is apical to the cervical line.
• Three main root canals exist, and the MB root may have 2 root canals.

Cervical Cross Section

• the cervical cross section is rhomboidal
• Mid root section of MB root canal is Oval-Kidney
• DB root canal is Round-Oval
• P root canal is Round-Oval

Pulp Cavity (2nd Molar)

• The pulp chamber is broader bucco-lingually than mesio-distally.
• There is a pulp horn beneath each cusp, and the floor is apical to the cervical line.
• Three main root canals exist, and the MB root may have 2 root canals.

Pulp Cavity (3rd Molar)

• The pulp cavity shows great variation in size and shape.
• The pulp chamber is larger than other molars because it is younger (erupting between 9-11 years old) .