Anatomy of the mandibular first molar - The mandibular first molar has five cusps: mesiobuccal (MB), mesiolingual (ML), distolingual (DL), distobuccal (DB), and distal (D). - The cusps are listed in order of decreasing size: ML, DL, DB, MB, and D. - The occlusal surface of the mandibular first molar is pentagonal in shape and tapers toward the lingual. - The tooth has four grooves: central groove, distobuccal groove, lingual groove, and buccal groove. - The mandibular first molar has two roots, with the distal root generally being straighter.

Pathology of the mandibular first molar - The shape of the developmental and supplementary grooves on the occlusal surface is described as being M-shaped. - Mandibular first molars are the most common carious teeth. - They are also the most common teeth to undergo endodontic treatment or extraction. - Up to 45% of all extracted teeth are mandibular first molars.

References - Zadik Y, Sandler V, Bechor R, Salehrabi R (August 2008). Analysis of factors related to extraction of endodontically treated teeth. - Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 106 (5): e31–e35. doi:10.1016/j.tripleo.2008.06.017. PMID18718782. - Ash, Major M. and Stanley J. Nelson, 2003. Wheelers Dental Anatomy, Physiology, and Occlusion. 8th edition. - Rodriguez-Florez, C.D. et al., 2006. Occurrence of an Eighth Cusp on Primary Second Mandibular Molars of a Contemporary Argentinean Child. Dental Anthropol 19(3): 83-85. (https://anthropology.osu.edu/DAA/back%20issues/DA%20Vol%2019%203.pdf)

Notation for deciduous teeth - In the universal system of notation, the deciduous mandibular first molars are designated by a letter written in uppercase. - The right deciduous mandibular first molar is known as S, and the left one is known as L. - The international notation uses a different system, with the right deciduous mandibular first molar known as 84 and the left one known as 74.

Notation for permanent teeth - In the universal system of notation, the permanent mandibular first molars are designated by a number. - The right permanent mandibular first molar is known as 30, and the left one is known as 19. - The Palmer notation uses a number in conjunction with a symbol designating the quadrant the tooth is found in. - For this tooth, the left and right first molars would have the same number (6), with the right one having the symbol ┐ and the left one having ┌. - The international notation has a different numbering system, with the right permanent mandibular first molar known as 46 and the left one known as 36.