Mandibular first molar
Encyclopedia
The mandibular first molar or six-year molar is the tooth
located distally (away from the midline of the face
) from both the mandibular second premolar
s of the mouth
but mesial (toward the midline of the face) from both mandibular second molar
s. It is located on the mandibular (lower) arch of the mouth, and generally opposes the maxillary (upper) first molars and the maxillary 2nd premolar in normal class I occlusion. The function of this molar
is similar to that of all molars in regard to grinding being the principal action during mastication
, commonly known as chewing. There are usually five well-developed cusp
s on mandibular first molars: two on the buccal (side nearest the cheek), two lingual (side nearest the tongue
), and one distal. There are great differences between the deciduous
(baby) mandibular molars and those of the permanent mandibular molars, even though their function are similar. The permanent mandibular molars are not considered to have any teeth that precede it. Despite being named molars, the deciduous molars are followed by permanent premolars.
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 has a different system of notation. Thus, the right deciduous mandibular first molar is known as "84", and the left one is known as "74".
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 in which quadrant the tooth is found. For this tooth, the left and right first molars would have the same number, "6", but the right one would have the symbol, "┐", over it, while the left one would have, "┌". The international notation has a different numbering system than the previous two, and the right permanent mandibular first molar is known as "46", and the left one is known as "36".
Mandibular primary first molars usually have four pulp horns.
The first molar is usually the first permanent tooth to erupt and has adult undertones.
Anatomy: The mandibular first molar has five cusps: the mesiobuccal (MB, toward midline and cheek), mesiolingual (ML, toward midline and tongue), distolingual (DL, away from midline and towards tongue), distobuccal (DB, away from midline and toward cheek), and distal (D, away from midline), listed in order of decreasing size. Listed in order of decreasing height they are: ML, DL, DF, MF, and D. Viewed from the top of the tooth (occlusal view), the mandibular first molar is pentagonal (five sided) in shape and tapers toward the lingual, with the sides being the buccal surface, the mesial surface, the lingual surface, distal surface, and the distobuccal surface. The occlusal surface has four grooves. The central groove is not straight but runs down the center of the tooth mesially to distally and contains four pits (mesial, central, central, and distal). The distobuccal groove runs from the distal pit in the central groove distobuccally separating the distal and distobuccal cusps. The lingual groove runs from the more distal of the central pits in the central groove toward the lingual surface between the mesiolingual and distolingual cusps. The buccal groove runs from the more mesial of the central pits in the central groove toward the buccal surface between the mesiobuccal and distobuccal cusps ending in the buccal pit. The portion of the central groove between the central pits is termed the Lewis offset
and is mandatory to account for the locations of the buccal and lingual grooves (buccal groove being more mesial than the lingual groove while they are parallel). From the buccal (buccal view), two roots are present. The distal root is generally straighter, although both often have a slight distal curvature. The heights of contour on the mesial and distal contact the adjacent teeth and are located at the junction of the occlusal and middle thirds of the crown. The mesial view shows a slight tipping of the crown to the lingual. Both roots have flutings but they are more prominent on the mesial root. The mesial root is broader buccolingually and its apex is more blunted. The height of contour on the buccal is in the gingival third and the occlusal two thirds of the surface is flat. The lingual height of contour is in the middle third of the tooth and the lingual surface is evenly convex. The sharpness of the mesiolingual cusp can also be noted from this view.
teeth and the most common teeth to undergo endodontic treatment or extraction. Up to 45% of all extracted teeth are mandibular first molars.
Tooth
Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...
located distally (away from the midline of the face
Face
The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
) from both the mandibular second premolar
Mandibular second premolar
The mandibular second premolar is the tooth located distally from both the mandibular first premolars of the mouth but mesial from both mandibular first molars. The function of this premolar is assist the mandibular first molar during mastication, commonly known as chewing. Mandibular second...
s of the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
but mesial (toward the midline of the face) from both mandibular second molar
Mandibular second molar
The mandibular second molar is the tooth located distally from both the mandibular first molars of the mouth but mesial from both mandibular third molars. This is true only in permanent teeth...
s. It is located on the mandibular (lower) arch of the mouth, and generally opposes the maxillary (upper) first molars and the maxillary 2nd premolar in normal class I occlusion. The function of this molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
is similar to that of all molars in regard to grinding being the principal action during mastication
Mastication
Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...
, commonly known as chewing. There are usually five well-developed cusp
Cusp (dentistry)
A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...
s on mandibular first molars: two on the buccal (side nearest the cheek), two lingual (side nearest the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
), and one distal. There are great differences between the deciduous
Deciduous teeth
Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...
(baby) mandibular molars and those of the permanent mandibular molars, even though their function are similar. The permanent mandibular molars are not considered to have any teeth that precede it. Despite being named molars, the deciduous molars are followed by permanent premolars.
In the universal system of notation
Universal numbering system (dental)
The Universal numbering system is a dental notation system for associating information to a specific tooth, and is commonly used in the United States.The designations "left" and "right" on the chart correspond to the patient's left and right, respectively....
, 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 has a different system of notation. Thus, the right deciduous mandibular first molar is known as "84", and the left one is known as "74".
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
Palmer notation
Palmer notation is a system used by dentists to associate information to a specific tooth. Although supposedly superseded by the FDI World Dental Federation notation, it overwhelmingly continues to be the preferred method used by orthodontists, dental students and practitioners in the United...
uses a number in conjunction with a symbol designating in which quadrant the tooth is found. For this tooth, the left and right first molars would have the same number, "6", but the right one would have the symbol, "┐", over it, while the left one would have, "┌". The international notation has a different numbering system than the previous two, and the right permanent mandibular first molar is known as "46", and the left one is known as "36".
Mandibular primary first molars usually have four pulp horns.
The first molar is usually the first permanent tooth to erupt and has adult undertones.
Anatomy: The mandibular first molar has five cusps: the mesiobuccal (MB, toward midline and cheek), mesiolingual (ML, toward midline and tongue), distolingual (DL, away from midline and towards tongue), distobuccal (DB, away from midline and toward cheek), and distal (D, away from midline), listed in order of decreasing size. Listed in order of decreasing height they are: ML, DL, DF, MF, and D. Viewed from the top of the tooth (occlusal view), the mandibular first molar is pentagonal (five sided) in shape and tapers toward the lingual, with the sides being the buccal surface, the mesial surface, the lingual surface, distal surface, and the distobuccal surface. The occlusal surface has four grooves. The central groove is not straight but runs down the center of the tooth mesially to distally and contains four pits (mesial, central, central, and distal). The distobuccal groove runs from the distal pit in the central groove distobuccally separating the distal and distobuccal cusps. The lingual groove runs from the more distal of the central pits in the central groove toward the lingual surface between the mesiolingual and distolingual cusps. The buccal groove runs from the more mesial of the central pits in the central groove toward the buccal surface between the mesiobuccal and distobuccal cusps ending in the buccal pit. The portion of the central groove between the central pits is termed the Lewis offset
Lewis offset
The Lewis offset is a term for the portion of the central groove on a permanent mandibular first molar which lies between the two central pits. It lies at an angle to the mesio-distal axis of the tooth, and causes the mesial portion of the central groove to be located further buccally than the...
and is mandatory to account for the locations of the buccal and lingual grooves (buccal groove being more mesial than the lingual groove while they are parallel). From the buccal (buccal view), two roots are present. The distal root is generally straighter, although both often have a slight distal curvature. The heights of contour on the mesial and distal contact the adjacent teeth and are located at the junction of the occlusal and middle thirds of the crown. The mesial view shows a slight tipping of the crown to the lingual. Both roots have flutings but they are more prominent on the mesial root. The mesial root is broader buccolingually and its apex is more blunted. The height of contour on the buccal is in the gingival third and the occlusal two thirds of the surface is flat. The lingual height of contour is in the middle third of the tooth and the lingual surface is evenly convex. The sharpness of the mesiolingual cusp can also be noted from this view.
Pathologies
The mandibular first molars are the most common cariousDental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...
teeth and the most common teeth to undergo endodontic treatment or extraction. Up to 45% of all extracted teeth are mandibular first molars.