They are six in number, three on each side of the mandible. They are larger than any mandibular teeth. The crowns are quadrilateral being some what longer mediodistally than buccolingually. The crowns of the mandibular molars are shorter cervico-occlusally than the other mandibular teeth. The posses two roots,  one mesial and one distal.



It is the largest tooth in the mandibular arch.  It has five well-developed cusps, two buccal two lingual and distal cusp, so it is formed of five lobes. Occasionally four cuspid first molar is formed with the distobuccal and distal cusp0s fused with little or no distobuccal developmental groove.

It has two well developed roots, one mesial and one distal which are very buccolingually.  The roots are widely separated at the aspices. The most abnormal finding is to see a thin slender long root originated lingual and adjacent to the mesial root.

Buccal aspect

  • The outline is trapezoid with the long side occlusally.  It is wider mesiodistally than occlusocervically.  The five cusps ar in view from this aspect (the two buccal cusps, the buccal portion of the distal cusp and the tips of the two lingual cusps).  The developmental grooves appear on the crown.
  • The mesiobuccal developmental groove which demarcates the mesiobuccal cusp from the distobuccal cusp is situated a little mesial to the root bifurcation.  It originates from the occlusal and extends onto the buccal surface of the crown ending with a pit.
  • This distobuccal development groove is longer than the other and separates the the distobuccal cusp from the distal cusp from the distal cusp.  It has its terminus near the cervical third of the crown.
  • The cervical ridge is a heavy mesiodistal ridge along thte cercival thir of the surface.  It is more prominent in its mesila portion. The cervical line is regular in outline and curved root wise.
  • The mesial outline of the crown is convex in the occlusal third to the contact area and becomes concave to the cervical line. The mesial contact area is located at the junction of the occlusal and middle thirds.
  • The distal ouline is more convex in the occlusal portion than the mesial outline, and straight from the cervical line to the distal contact area which is near the crown centre cervico-occlusallu.
  • The buccal cusps are flat with less curved ridge (which is characteristic for madnibular moral) .  The mesiobuccal cusp is the widest mesiodistally and the distobuccal cusp, is less wide.
  • The mesial root curves mesially from a point shortly below the cervical line to the middle third, then curves distally to tapered apex which is located below the mesiobuccal cusp.  The distal outline of the mesial root is concave from the bifurcation of the trunk to the apex.
  • The distal root is less curved than mesial.  The apex is more pointed and is located below or distal to the distal contact area of the crown.
  • Both roots are wider misiodistally at the buccal surgace than they are lingually.  Develpmental deprssions are present on ht emesial and distal sides.  The point of bifurcation of the two roots is located approximately 3mm below the cervical line.  There is a deep developmental depression on the root trunk from the bifurcation ending immediately above the cervical line.

Lingual aspect

  • It is trapezoid and is smaller than the buccal aspect due to the convergence of the mesial and distal surfaces. The mesial outline of the crown is convex from the cervical line to the marginal ridge with the crest of curvature at the contact area.
  • The distal outline is straight or slightly concave above the cervical line to the distal contact area and becomes convex to the occlusal margin.  The contact area is lower than on the mesial side located in the middle third.
  • It shows two pointed lingual cusps with high cusp ridges as well as the lingual part of the distal cusp.  The mesiolingual cusp is the widest mesiodistally and its cusp tip is higher than the distolingual cusp.  The mesiolingual and distolingual cusp ridges form obtuse angles at the cups tips.  The tow lingual cusps are separated by the lingual developmental groove  which extends downward on the lingual surface of the crown for a short distance to the junction of the occlusal and middle thirds.  The distal cusp is at a lower level than the mesiolingual and distolingual cusps.
  • The cervical line is irregular and is sharply pointed toward the bifurcation of the root.
  • The roots are longer by 1mm lingually than buccally.  The root trunk is also 1mm longer, the root bifurcation starts at about 4 mm.  It shows deep developmental depression form the point of bifurcation progresses cercially and fades out entirely immediately below the cervical line.  The bifurcation groove of the crown.

Mesial aspect

  • It is rhomboidal, wider at the cervical margin than at the occlusal margin.  From this aspect the mesiobycccal and mesiolinguals cusps together with the mesial root are seen.  The entire crown has a lingual tilte in relation to the root axis (the maxillary posterior teeth have the centre of the occlusal surgaces between the cusps in line with the root axis).
  • The buccal outline is convex immediately above the cervical line which outlines the buccal cervical ridge.  Above the cervical rideg, the buccal contour becomes flat till the contour of the mesiobuccal cusp.  The mesiobuccal cusp is located directly above the buccal third of the mesial root.
  • The lingual outline is straight from the cervical line to join the curvature at the middle third then becomes curved till tip of the mesiolingual cusp.  The crest of curvature is locted at the centre of the middle third of the crown.  The mesiolingual cusp tip is located directly above the lingual third of the mesial root.
  • The mesial marginal ridge is continous with the mesial ridges of the mesiolingual and mesiobuccal cusps, but is below the cusp tip by 1 mm.
  • The surface of the crown is covex and smooth over the cusps.  A slightly concave areas exists at the cervical line immediately above the centre of the mesial root.  Above this area is the contact area which is rounded to slightly ovoid in shape and located at the junction of the middle and occlusal thirds almost centred buccolingully.
  • The root outline is almost straight buccally and lingually and then becomes convex on both sides to taper to a blunt apex which is located directly below the mesiobuccal cusps.  The mesial surface of the root is convex with broad concavity in the centgre for the full length of the rootl.  The apex is usually bifid at the apical third.

Distal aspect

  • The gross outline is similar to the mesial aspect, but the crown is shorter distally, and the buccal and lingual surfaces converge distally.  From this aspect part of the occlusal surface and part of each of the five cusps are seen due to the distal inclination of the crown to the long axis.
  • The distal, distobuccal and distolingual cusps are clearly seen.  The distolingual cusp is the largest of the three cusps, and the distal is the smallest.
  • The distal marginal ridge is short and dips sharply in a cervical direction and developmental groove or depression is found corssing it at this point.
  • The end of the distobuyccal developmental groove is located on the distal surface, forming a convavity at the cervical portion of the distobuccal line angle of the crown.
  • The distal contact area is located below the distal cusp and is centered over the distal root near the crown center cervico-occlusally.  It is larger than the mesial contact area.
  • The distal surface of the crown is convex except above the cervical line whre is becomes flat and joins the flattendd surface of the root trunk distally.
  • The distal root is narrow buccalingually than the mesial root.l  The distal and mesial surfaces of the root are smooth and flat with a shallow developmental depression on the distal surface.  The apical third of the root is more rounded and tapers to a sharper apex than is found in the mesial root.  The lingual border of the mesial root may be seen from the distal aspect.

Occlusal aspect

  • The crown is hexagonal from the occlusal aspect.  It is 1 mm greater mesiodistally tan buccolingually (which is the opposite for the maxillary molars).  It has five cusps, the mesiobuccal cusp is slightly  larger than the lingual cusps which are nearly equals, than followed by the distobuccal cusp.  The distal cusp is the smallest of all.  Some times the first molar has four cusps when the distobuccal and distal cusps fuse.  The crown converges lingually and distally.
  • The occlusal surface has a major central fossa and two mino fossae.  The central fossa is concave and circular.  It is centerally placed on the occlusal surface between the buccla and lingual cusp ridges.  The two minor fossae are the the mesial triangular fossa and the distal triangular fossa just distal and mesial to the marginal ridge respectively.  The distal fossa is smaller and shallower than the mesial fossa.  The central groove has its two has its two terminals in each fossae.
  • From the central fossa at the central pit amny developmental grooves radiate.  The are, the central developmental groove which in a zigzag manner runs it ends on either side in the triangular fossae.  Sometimes it crosses the distal marginal ridge and continues as a shollow groove for a small distance on the distal surface.  A short distance from the central pit, the central groove joins the mesiobuccal developmental groove which separates the mesiobuccal and distobuccal cusps.
  • The developmental groove of the surface is irregular coursing in a lingual direction to the junction of the lingual cusp ridges.
  • The distobuccal developmental groove extends from the central fossa to pass between the distobuccal and distal cusps.Supplemental grooves,and developmental pits may also found on the occlusal surface.Buccal and lingual supplimantal grooves join the terminal of the central groove in the mesial and distal triangular fossae.

Pulp cavity

  • In buccolingual section the pulp chamber is wide with prominent pulp horns.Some times the pulp chamber is quite deep with the floor extending well down.The mesil root may show broad root canal (but very thin mesiodistally) which becomes narrow at the apical end of the root to a pointed apical foramen.Mor likely this root present two separate canals which join in a common apical opening,or the two canels open in two separated apical foramina.
  • In mesiodiscatl section the pulp chamber is wide and accommodate pulp horns.The mesial root show considerable curvature which contains the most constricted canal mesiodistally. The distal root presents shorter, rounder and more open root canal.
  • In cross section at the cervical part of the pulp chamber is rectangular in shape.



The Second molar supplements the first molar in function and its anatomy differs in the following details.

  • The second molar is slightly smaller than the first molar in all dimensions, although a second molar with larger crown or longer root may be found.
  • The crown has four well developed cusps, two buccal and two lingual of nearly equal development. The distobuccal cusp is larger than the same one of the first molar.
  • The tooth has two well developed roots,one mesial and distal. They are less wide buccalingually than the roots of the first molar and they are not so widely separated.

The differences between the second and first molars are as follow:-

■ Buccal aspect

  • The crown is some what shorter cervico-occlussally and narrower mesiodistally than the first molar.
  • The buccal cervical ridge is less prominent.
  • There is one development groove, the buccal developmental groove between the mesiobuccal and distobuccal cusps.
  • The roots may be shorter and closer together and their axes are parallel.  They are inclined distally in relation to the occlusal plane of the crown than is found on the first molar.  The roots may be used for all or part of their length.

■ Lingual aspect.

  • The crown and root of the second molar converge far less lingually than the first molar.
  • The two lingual cusps, mesiolingual and distolingual are nearly the same size.
  • The lingual developmental groove crosses from the occlisal surface onto the ligual durface and fades out near the junction of the middle and occlusal thirds,between the lingual cups.
  • The curvatures of the contact area are more noticeable from the lingual aspect. They are at slight lower level specially the distal contact area than those of the first molar.
  • The cervical line is irregular mesiodistally.

■ Mesial aspect

  • It is Rhomboidal in shape with lingual tilt.
  • The buccal cervical ridge is less pronounced.
  • The occlusal surface is more constricted buccolingally.
  • The mesial root is less broad and some what pointed apically.

■ Distal aspect

  • There is no distal cusp and distobuccal groove.
  • The distal root is less broad.
  • The contact area is therefore centered on the distal surface buccoligually as well as cervico-occlussaly.

■ Occlusal aspect

  • The occlusal aspect of the second molae differs considerably from the first molar. The outline form of the occlusal surface is rectangular wider mesiodistally than buccolingually.
  • The second molar exhibit more curvature of the outline of the crown distally than mesially showing a semicircular outline of the disto-occlusal surface in comparison with a square outline mesially.
  • The occlusal surface shows four cusps.  The distobuccal cusp is less pronounced than the mesiobuccal cusp.  There is no distobuccal developmental groove buccally or occlusally.The distal cusp is absent. The lingual cusps are equal.
  • The buccal and lingual development grooves meet the central groove at right angles at the central pit,so forming a cross dividing the crown into four nearly equal parts. This groove is known as crossi form fissure.
  • There are major central fossa and two minor fossae ( the mesial and distal triangular fossae). Three pits are present, a mesial a distal, and a central.
  • There are more secondary grooves than on the first molar so the occlusal surface is wrinkled.
  • Pulp cavity.
    • As for the mandibular firs molar, except that the root canals appeared shorter, straighter with less spread.
    • The cervical cross section is not as square as the first molar as the crown tapers distally in the second molar.



The mandibular third molars are extremely variable in size and shape of both crown and root portions.

There are two basic forms:

  • Type I resembles the permanent second molar 50%. It has four cusps and the same general occlusal pattern and contour. Ordinarily the size is the same, but range from very small larger than any other molar.
  • Type II resembles the permanent first molar (40%) with five cusps and a similar occlusal pattern and contours. In 10% of cases it has more than five or less than four cusps.

The roots are extremely variable in size,number and curvature.Single fused roots are common.Most often,root length is less than other mandibular molars regardless of the crown size. The most common root torm reveals two short curved roots.

Pulp cavity, If it is well developed and is comparable to the second molar in shape the pulp cavity will resemble the second molar.However,if it differs,it follows the general outline of the tooth.