Transcript PERMANENT MANDIBULAR MOLARS
PERMANENT MANDIBULAR MOLARS
MANDIBULAR 1
st
MOLAR
• the largest and the strongest mandibular molars • not considered succedaneous • first permanent molars to erupt=six year molars • 5 cusps • 2 roots D &M (3 canals: 1-D, 2-M)
UNIQUE FUTURES
• largest mesiodistal crown dimension of any tooth • he occlusocervical and faciolingual dimensions of the first molar are greater than any other mandibular molar • Mandibular first molars have three facial cusps as do some mandibular third molars • the longest roots of any molar • the greatest mesiodistal root separation of any molar • The mesial root has the greatest faciolingual dimension of any root in the mouth
Buccal view
• The mesiofacial (mesiobuccal) cusp is the largest, widest, and highest of the 3 facial cusps • The facial (buccal) cervical line is nearly straight but there can be enamel that dips cervically nearly into the furcation • The two lingual cusps (mesiolingual and distolingual) are visible because they are taller cusps
• The mesial root averaged 1 mm longer than the distal root • Both roots have an overall distal inclination • The distal root is straighter than the mesial root
Lingual view
• The greater height of the lingual cusps hide the facial cusps • portions of the proximal surfaces are visible from a lingual view • The lingual cervical line is nearly straight
Mesial view
• Two cusps can be seen (ML & MB) • Only one root can be seen (FL length twice MD) • The mesial cervical line curves occlusally • The lingual height of contour (area of greatest convexity) has been located in the middle third of the crown • The faciolingual (buccolingual) crown, root, cusps dimension is greater M than D • The two major
mesial
cusps (mesiofacial and mesiolingual) are larger than the distal cusps
Distal view
• Distolingual cusp is largest • distal proximal contact has been located facial to the crown center (Fuller/Denehy/Schulein; Renner), centered over the root • From a distal view, more of the facial surface can be seen than from a mesial view because the crown tapers distally • More of the occlusal surface is visible from a distal view than mesial view because the distal surface is shorter occlusocervically
Occlusal view
• 5 cusps. All of them functional • The mesiofacial cusp is the largest cusp • The crown tapers lingually • The outline form has been described as pentagonal
• There are four developmental grooves on the occlusal surface: central; mesiofacial (mesiobuccal); distofacial (distobuccal); and lingual • There are three fossae: central; mesial; and distal • The central developmental groove has a zigzag mesiodistal form • The central development groove forms a “Y” shape with the lingual developmental groove. This is one of the principal occlusal groove patterns
MANDIBULAR 2
nd
MOLAR
• Resemble 1 st B and L except there no 5 th cusp or D cusp • Rooth shorter, closer more D inclined • 4 cusp nearly equal size
UNIQUE FUTURES
• F the roots curve laterally and then toward each other in a manner that resembles the handles of a pair of pliers a unique form shared with only the maxillary first molar • a MF prominence, a unique feature for mandibular molars • The D proximal contact is centered both FL and occlusocervically, a characteristic shared with four other teeth (Max lateral incisor, Max canine, Max 1 st molar and Max 2 nd molar)
Facial view
• Shorter MD and cervicoolcclusally than 1 st • Just 2 B cusps • Roots shorter, closer, more D inclined
Lingual view
• Little if any of the mesial and distal surfaces are visible lingually due to the limited lingual crown taper • The lingual groove may terminate on the occlusal surface or extend onto the lingual surface in the occlusal third (L pit) • Contact areas lower D and M
Mesial view
• The FL dimension of the M root is greater than the distal , but less rhan 1 st molar • mesial proximal contact - similar to the 1 st molar, slightly to the facial of the center of the crown • The cervical line is more cervically positioned on the facial surface than lingual
Distal view
• No Distal cusp • Little of the facial surface is visible from a distal view • proximal contact has been located at the center of the crown • Distal root is narrower than M
Occlusal view
• The outline form has been described as rectangular • A number of supplemental grooves are present, “wrinkled” appearance • mesiobuccal cusp is normally the largest cusp, but almost equal in size • developmental grooves: facial; central; and lingual, forming a cross • 3 fossae, 3 B, L & M pits+grooves may present
MANDIBULAR 3
RD
MOLAR
• more varied in size and shape than all other teeth except the maxillary third molars • small apical-occlusal dimension • the D half of the crown has a noticeably shorter than the M half • crown resembles a mandibular second molar with 4 cusps • Some mandibular third molars have three facial cusps • The mesiolingual cusp is the largest of all the cusps. The lingual cusps are often larger and longer than the facial cusps and more rounded
• • • • • • The roots are usually pointed, inclined D, often fused, short There may be multiple roots and as many as 8 roots The
facial
surface is very convex and the
tooth
has a bulbous form
occlusal outline form
is often ovoid The
occlusal table
in
outline form
is distinctly ovoid and highly restricted The
occlusal surface
is quite “wrinkled” due to numerous supplemental grooves and
ridges
MANDIBULAR MOLAR ROOTS
• 2 roots: 1-M, 2 – D with single root trunk • M root – longer and stronger, curves M then turns D near apex • Root trunk short and grooved on B and L surfaces