Permanent Molars

Permanent Molars: General Features

• Molars are the most posterior teeth, distal to premolars, and the largest in the dentition.

• Each arch has six molars, three per quadrant: first, second, and third molars.

• Third molars (wisdom teeth) vary in eruption time, size, and form and usually mark the end of jaw growth.

• Only permanent dentition has three molar types; primary dentition has two.

• Molars are nonsuccedaneous, do not replace primary teeth, and have strong crowns for grinding food.

• Crown outline is trapezoidal from buccal or lingual views.

• First molars are the largest, followed by progressively smaller second and third molars.

• Molars have large crowns, shorter OC, buccal cervical ridges, and at least three cusps.

• Occlusal tables are bordered by cusp and marginal ridges, with grooves and pits.

• Maxillary molars are trifurcated (three roots), while mandibular molars are bifurcated (two roots).

• Furcation is the area between root branches; furcation crotches are spaces between roots.

Clinical Considerations for Permanent Molars

• Third molar evaluation by age 25 is recommended, but extraction remains controversial.

• Periodontitis can cause furcation involvement due to loss of periodontal support.

• Furcation invasion is measured using a Nabors probe in a periodontal pocket.

• Debridement involves treating each root separately with instruments, air polisher, or ultrasonic devices.

• Many molar furcations are too narrow for access, decreasing therapy prognosis.

• Cervical ridges pose challenges during instrumentation and restoration.

• Mulberry molars result from congenital syphilis causing enamel hypoplasia.

• Enamel pearls are enamel deposits in root furcation areas, mainly on second molars.

• Dilaceration (root distortion) and root fusion can complicate extractions and endodontic treatments.

Permanent Maxillary Molars: General Features

• Erupt 6 months to 1 year after mandibular molars and are the first permanent maxillary teeth.

• Largest and strongest maxillary teeth, shorter OC but larger in other measurements.

• Crown outline is rhomboidal from occlusal and trapezoidal from proximal views.

• Crown is centered over the root with no lingual inclination.

• Usually have four major cusps and a unique oblique ridge (except third molars).

• Trifurcated roots: MB, DB, and lingual (palatal), with the lingual root being the largest and longest.

• Three furcations are located on buccal, mesial, and distal surfaces, near the cervical and middle thirds of the root.

Clinical Considerations for Permanent Maxillary Molars

• Lingual pits are at high caries risk due to biofilm retention and thin enamel.

• Roots may penetrate the maxillary sinus due to trauma or extraction.

• Concrescence (fusion of roots through cementum) is common.

Permanent Maxillary First Molars: Specific Features

• Universal numbers #3 and #14; International numbers #16 and #26.

• Erupt between 6-7 years, root completion by 9-10 years; first permanent maxillary teeth.

• Nonsuccedaneous, erupting distal to primary maxillary second molars.

• Largest tooth in the maxillary arch with the largest crown in the permanent dentition; least variable.

• Roots are larger and more divergent than second molars, twice as long as the crown.

• Lingual root is largest/longest, inclining lingually and curving buccally.

• MB root is second largest/longest, inclined mesially/buccally, apical third curves distally.

• DB root is smallest/shortest, inclined distally/buccally, apical third curves mesially.

• MB and DB roots have extreme curvature, resembling pliers' handles.

• Furcations are well-removed from CEJ; concavity depths limit homecare and instrumentation.

• Pulp cavity has one pulp horn per major cusp; three main pulp canals (one per root).

• Rhomboidal occlusal outline with longer, more prominent mesial marginal ridge.

• Cusp of Carabelli (fifth nonfunctioning cusp) is common on the ML cusp.

• Tooth loss impacts functional occlusion due to arch position and early eruption.

Permanent Maxillary Second Molars: Specific Features

• Universal numbers #2 and #15; International numbers #17 and #27.

• Erupt between 12-13 years, root completion by 14-16 years; distal to maxillary first molars.

• Nonsuccedaneous, no primary predecessors.

• Crown has much variation, especially in DL cusp size; usually four cusps, can have three.

• Roots are smaller, less divergent, and more parallel than first molars.

• Lingual root is largest/longest, extending beyond crown outline, straighter than first molars.

• Furcation notches are narrower, depressions shallower; greater chance of root fusion.

• Pulp cavity has a pulp chamber and three main pulp canals (one per root).

• Distal cusp is smaller and shorter than on the first molar.

• The cusp of Carabelli is typically not present.

• Mesial contact area is larger, cervical flattening/concavity less pronounced.

• Two crown outlines: rhomboidal and heart-shaped.

Permanent Maxillary Third Molars: Specific Features

• Universal numbers #1 and #16; International numbers #18 and #28.

• Erupt between 17-21 years, root completion by 18-25.

• Distal to permanent maxillary second molars and nonsuccedaneous.

• Smallest molar, most variable in shape; difficult to describe a typical form.

• Smaller in all dimensions than second maxillary molar; poorly developed crown.

• Crown outlines: heart-shaped (most common) and rhomboidal.

• Heart-shaped has three cusps: MB, DB, and ML.

• DB cusp is shorter than MB cusp; roots curve distally.

• Roots may be fused, giving a single-root appearance.

• The pulp cavity has a pulp chamber, three pulp canals, and three pulp horns.

Clinical Considerations for Permanent Maxillary Third Molars

• Homecare, instrumentation, or restoration are difficult due to extreme posterior position.

• May fail to erupt and remain impacted due to underdeveloped maxilla.

• Microdontia (smaller crown, peg molar) can occur due to proliferation failure.

Permanent Mandibular Molars: General Features

• Erupt 6 months to 1 year before corresponding maxillary molars.

• Crown has four or five major cusps, always two lingual cusps of similar size.

• Wider MD than BL.

• The crown outline is rectangular, four-sided, or pentagonal from occlusal view.

• Buccal crown outline has a strong lingual inclination from proximal view, like premolars.

• Mandibular molars are usually bifurcated.

• Two furcations on buccal and lingual surfaces, one-fourth the root length from CEJ.

• Root concavities on mesial surface of the mesial root and furcal surfaces of both roots.

Clinical Considerations for Permanent Mandibular Molars

• Instrumentation/restoration difficult due to narrow lingual surfaces and crown inclination.

• Homecare difficult due to lingual inclination.

Permanent Mandibular First Molars: Specific Features

• Universal numbers #19 and #30; International numbers #36 and #46.

• Teeth usually are the first permanent teeth to erupt in the oral cavity (6-7 years).

• Nonsuccedaneous.

• Crown usually has five cusps: three buccal, two lingual.

• Two roots, mesial and distal, larger and more divergent than the second molar's roots.

• Both roots are usually the same length; if one is longer, it's the mesial root.

Specific Overall Features

• Midway-placed furcations are well removed from the CEJ (3 mm buccal, 4 mm lingual).

• Pulp cavity likely has three root canals (distal, MB, ML) and five pulp horns.

• Mandibular first molars also have pulp canals, distal pulp canal is much larger

• The mesial root usually has two pulp canals: MB and ML.

• The crown is larger MD than OC; widest tooth MD of any permanent tooth.

• The Angle classification of malocclusion relates to the MB groove of a mandibular first molar.

• Buccal pits on the buccal surface of mandibular first molars are at an increased risk of caries

• Tooth loss is bad because The permanent mandibular first molars are considered important in regard to the development of occlusion.

Permanent Mandibular Second Molars: Specific Features

• Numbers #18 and #31 (#37 and #47).

• Erupts between 11 and 13 years of age.

• The crown measurements are generally smaller when compared to a first molar.

• The four cusps of a second are nearly equal in size compared with the five cusps of differing sizes of a first molar.

Other Features

• Buccal Groove divides the same-size MB cusp and DB cusp

• The ML cusp and DL cusp have the same size and shape as the buccal cusps, although they have sharper cusp tips.

• Second molars also has two transverse ridges and a crossshaped groove pattern is formed. Also has three occlusal pits: central, mesial, and distal.

Permanent Mandibular Third Molars: Specific Features

• Numbers #17 and #32 (#38 and #48)

• Has Variable shape, having no standard form.
  Smaller in all dimensions than the second molar

• The occlusal surface appears quite wrinkled, with an irregular groove pattern, numerous supplemental grooves, and occlusal pits.

• IT has has two roots that are fused, irregularly curved, and shorter than those of a mandibular second molar.