From the occlusal aspect, all five cusps of the maxillary first molar are visible. Mesolingual cusp is the largest cusp, followed by the mesobuccal cusp, then the distolingual cusp, followed by the distobuccal cusp, and the smallest, the fifth cusp. The fifth cusp is also known as the cusp of Carabelli or Carabelli's tubercle, named after George Carabelli, a Vienna dentist who first noticed it. From the occlusal aspect, The outline form of the crown is rhomboidal in shape.
The acute angles of the rhomboid are at mesiobuccal cusp and distolingual cusp, whereas the obtuse angles are at the mesiolingual cusp and distobuccal cusp. The mesiodistal dimension of the crown is more in the lingual half than buccal half and the buccolingual dimension is more in the mesial half than distal half. In maxillary molars, three cusps, mesiolingual cusp, mesiobuccal cusp and distobuccal cusp are considered the primary cusps.
These cusps joined by the cuspal ridges, mesial marginal ridge and oblique ridge forms the maxillary molar primary cusp triangle. This is an important feature in identifying maxillary molars. The distolingual cusp and fifth cusp are the secondary cusps.
As we move from maxillary first molar to maxillary third molar, the distolingual cusp becomes smaller and smaller. There are numerous ridges in maxillary first molar. Starting with the cuspal ridges, each of the functional cusp has two cuspal ridges.
One mesial cuspal ridge and one distal cuspal ridge. Two marginal ridges are present. Mesial marginal ridge present at the mesial outline and distal marginal ridge present at the distal outline.
Four triangular ridges. One for each functional cusp is seen running from the cusp tip towards the center. Among all these ridges, two unions of four ridges can be seen. First, the union of the triangular ridge of the mesolingual cusp and the triangular ridge of the mesobuccal cusp which forms the transverse ridge. Second, is the union of triangular ridge of distobuccal cusp and distal ridge of mesolingual cusp.
This forms the oblique ridge. Oblique ridge is a unique feature of all maxillary molars. There are two major fossa and two minor fossa. The two major fossa are the central fossa just mesial to the oblique ridge which is triangular in shape and distal fossa just distal to the oblique ridge which is linear in shape. The two minor fossa are the two triangular fossa, mesial triangular fossa and distal triangular fossa just adjacent to the marginal ridges.
A central developmental pit is seen at the bottom of the central fossa. Coming to the grooves, a buccal developmental groove from the central pit runs buccally, goes between the buccal cusps on to the buccal surface. A central developmental groove from the central pit runs in a mesial direction and ends in the mesial triangular fossa.
A distal oblique developmental groove originates from the distal triangular fossa, runs through the linear distal fossa and turns lingually between the lingual cusps. From here, it continues on to the lingual surface as lingual developmental groove. A groove formed by the cusp of carabilly is known as the fifth cusp groove.
An additional transverse groove of the oblique ridge is seen in some teeth where a groove runs across the oblique ridge connecting the central fossa and the distal fossa. Apart from these, Numerous supplemental grooves are seen on the occlusal surface of maxillary first molar. Few clinical considerations. Maxillary first molar along with mandibular first molar is used to classify malocclusion in teeth according to Engel's classification.
Due to its three strong roots, maxillary first molar is used as an anchorage in orthodontic treatment. The development of cusp of caribouille varies from being a well-formed cusp to a small groove in different races. Thus, it is sometimes used in forensics to identify populations. For example, the cusp of caribouli is generally well developed in mongoloid and negroid races. Due to its varying development, some researchers do not consider it as a normal landmark of tooth but a developmental anomaly.
The mesio-buccal root usually has two root canals called MB1 and MB2. This is important for endodontic procedures.