3First PremolarThese premolars have bifurcated roots. A Longitudinal groove is present on the root. The mesial surface shows a developmental fossa. The mesial marginal groove crosses the mesial marginal ridge and extends onto the mesial surface. The facial cusp is wider and longer than the lingual cusp. The mesial ridge of the facial cusp may have a slight concavity.
4Number of roots – 2Number of pulp horns – 2Number of cusps – 2Number of developmental lobes - 4
5Second PremolarThese premolars usually have a single root. About 40% have two root canals. The buccal and lingual cusps are nearly equal in length. The buccal cusp is shorter than that of the first premolar. The entire crown, especially the occlusal outline, is less angular and more rounded. The occlusal developmental grooves are shorter, shaloower, and more irregular.
6Number of roots – 1Number of pulp horns – 2Number of cusps – 2Number of developmental lobes - 4
7First MolarA cusp of Carabelli (5th cusp) may be present. The occlusal outline is square or rhomboidal rather than triangular. The distolingual cusp is well developed. There is a prominent oblique ridge and distal facial and lingual grooves. The crown is nearly as wide mesiodistally as buccolingually. The three roots are widely seperated.
8Number of roots – 3Number of pulp horns – 4Number of cusps – 5Number of developmental lobes - 5
9Second MolarThese teeth are similar to the first molars except that the 5th cusp is usually absent and the distolingual cusp is less developed. The oblique ridge is less prominent. The crown is shorter occlusocervically and narrower mesiodistally. The occlusal outline of the drown is rhomoidal to heart shaped. The three roots are less seperated.
10Number of roots – 3Number of pulp horns – 4Number of cusps – 4Number of developmental lobes - 4
11Third MolarThese teeth vary more in form than the others. They usually do not have a distolingual cusp. The occlusal outline is heart shaped, with three cusps. The roots, usually three, have a tendency to be very close together or to fuse with an extreme distal inclination.
12Number of roots – 1 to 4Number of pulp horns – 1 to 4Number of cusps – 3 to 5Number of developmental lobes - 4
14First PremolarThese premolars have two cusps, one large buccal and one small lingual. The buccal cusps are centered directly over the root. The lingual cusps are centered lingual to the root and are afunctional and nonoccluding. The occlusal surface slopes sharply lingual in a cervical direction. The mesiobuccal cusp ridge is shorter than the distobuccal ridge. It has a mesiolingual developmental groove and one root.
15Number of roots – 1Number of pulp horns – 1 or 2Number of cusps – 2Number of developmental lobes - 4
16Second PremolarThese premolars have 2 or 3 cusps. The buccal cusp is very large. If two lingual cusps are present, the mesiolingual is the larger. Although the lingual cusps are larger than on the first premolar, they are afunctional and do not occlude with the maxillary teeth. A second premolar has more secondary anatomical features and more variation than any other tooth except a third molar.
17The two-cusp forms a U- or H- groove pattern The two-cusp forms a U- or H- groove pattern. A mesiolingual groove is rare and is poorly developed if present. The three-cusp form has a lingual developmental groove between the two lingual cusps and forms a Y- groove pattern. The single root is longer and larger than that of a first premolar.
18Number of roots – 1Number of pulp horns – 2 or 3Number of cusps – 2 or 3Number of developmental lobes - 4
19First MolarThe five cusps make these that largest mandibular teeth. They are wider mesiodistally than buccolingually. The crown converges lingually and slightly distally. The three buccal cusps are seperated by two buccal grooves. The two lingual cusps are seperated by one lingual groove. These three grooves converge to form a Y pattern. There are two roots, a mesial and a distal, and three root canals (the mesial root has two root canals).
20Number of roots – 2Number of pulp horns – 5Number of cusps – 5Number of developmental lobes - 5
21Second MolarsThese molars have four cusps of nearly equal size. The crown is smaller in all dimensions and has less lingual convergence. There is only one buccal groove and one lingual groove, which join together on the occlusal surface as they bisect the central developmental groove. The groove pattern is therefore a cross (+). The two roots are closer together and incline slightly distally. There is one root canal in the distal root. The mesial root can have one or two root canals.
22Number of roots – 2Number of pulp horns – 4Number of cusps – 4Number of developmental lobes - 4
23Third MolarsThese are the most variable mandibular teeth in form. They usually resemble the mandibular second molars, with four cusps and a shallower, smaller central fossa, with more secondary and teriary grooves. A five-cusp form is not unusual. The two roots (mesial and distal) and often fused and inclined toward the distal side.
24Number of roots – 2 (fused) Number of pulp horns – 4 or 5Number of cusps – 4 or 5Number of developmental lobes – 4 or 5