First maxillary molar (part 1)
The first maxillary molar is the most significant tooth of all maxillary molar teeth. It has a rhomboid shape, and its mesiodistal length is slightly smaller than the buccolingual length. The buccal mesiodistal length of the first maxillary molar is narrower than the same palatal length.
The cervical distobuccal line angle is concave and rounded, and it is a common site for plaque retention. The buccal surface is flatter than the palatal, as the palatal surface tends to be more convex.
The first maxillary molar presents with four cusps:
The first maxillary molar is the only tooth of the maxillary molars, which sometimes has a 5th cusp called the cusp of Carabelli. The cusp of Carabelli is usually connected with the mesiolingual cusp. Also, the 5th cusp groove is usually present. The highest point of each cusp is known as the cusp apex.
The height of the contour of this tooth is as follows:
- Facial - in the cervical third;
- Palatal (lingual) - near or in the middle third;
- Buccal - often called the buccal cervical ridge or simply the cervical ridge.
The mesiobuccal root presents with mesial and distal root depressions. This characteristic can result in a 4th root canal on the mesiobuccal root.
Overall, the roots of the first maxillary molar are divergent, and they can spread out of the periphery of the crown part.