Introduction
There are twelve permanent molars: first, second and third in each quadrant (16–18, 26–28, 36–38, 46–48). The first molars are the largest and strongest teeth of each arch; the third molar is the last tooth, with no neighbour behind it.
Molars do most of the chewing and grinding, hold the vertical dimension of the face, keep the arch continuous so the other teeth stay aligned, and keep the cheeks full.
Upper molars
Fossae of the upper first molar: a large central fossa, a small mesial triangular fossa, a tiny distal triangular fossa and an elongated distal fossa between the two lingual cusps. The distal oblique groove runs out onto the lingual surface as the lingual groove.
Lower molars
The mesial root of lower molars always has two canals, buccal and lingual. Both roots are about twice as long as the crown and curve distally in their apical half.
Marks that tell the molars apart
- Lower molar crowns tilt lingually on their roots, so their lingual cusps sit lower in the mouth and a lot of the buccal surface shows from above. This is true of all lower back teeth.
- Lower molars taper toward the distal and toward the lingual; the mesial cusps are larger than the distal ones.
- The buccal crest of curvature of lower molars is a cervical ridge in the cervical third.
- On all molars the distal marginal ridge is lower than the mesial one, and distal contacts are more cervical.
- Upper molars are wider buccolingually; lower molars are wider mesiodistally.