Upper molars
There are 12 molars (6 in the maxilla; 6 in the mandible)
Their name of molar derives from their function as a grinding stone.
They play an important role in the grinding and comminution of food during chewing.
They ensure the maintenance of the vertical dimension of occlusion.
These teeth arise from the first dental lamina, so they do not replace any temporary teeth.
There are therefore 3 molars per maxillary or mandibular hemi-arch.
The first molar called the 6 year tooth is the most mesial of the 3 molars.
The second molar called the 12-year tooth immediately distal to the first molar
The third molar, called the wisdom tooth, is the most distal in the dental arch.
These teeth erupt between the ages of 6 and 18.
Together with the premolars, they constitute the cuspid posterior group of teeth.
The molars are in descending series,
The first molar is always larger than the second molar; itself stronger than the third.
Molars have the largest functional occlusal surface of all teeth.
Molars have several cusps, but always at least 2 vestibular cusps.
Molars have 2 or 3 roots
The first upper molar or 6-year tooth is remarkable for its anatomical stability.
It is the only tooth that consistently presents a wider lingual face than the vestibular face, hence the divergence of the proximal faces in occlusal view towards the lingual face.
At the glue level, the lingual face is narrower than the vestibular face.
This tooth constantly presents an oblique crest also called “enamel bridge” which crosses the occlusal surface joining the mesio-lingual and disto-vestibular cusp summits.
On the lingual surface of the ML cusp appears a more or less well developed relief, the fifth cusp or tubercle of carabelli.
Vestibular face: the crown has a trapezoidal shape, the large base is located at the level of the occlusal contour.
the cusps are visible; 2 buccal cusps and 2 lingual cusps. The occlusal outline of the buccal cusps is characteristic; the mesio-buccal cusp is larger in size than the disto-buccal cusp
The vestibular cervical contour is in the form of a brace with occlusal concavity; each of the arms of the brace corresponds to a vestibular cusp.
The mesial contour shows maximum convexity at the junction of the occlusal third and the middle third.
At the cervical third, the mesial contour becomes relatively flat, sometimes concave.
The distal contour is uniformly convex from the disto-occlusal angle which is rounded to the cervical line. The maximum convexity is located in the middle third.
The vestibular surface is convex in its cervical half and results from the juxtaposition of two cuspal convexities
Lingual side: the general outline of the crown is the same as in the vestibular view
The mesiolingual cusp is the largest, occupying 3/5 of the mesiodistal diameter.
The distolingual cusp is 0.5 mm to 1 mm shorter than the mesiolingual cusp.
The lingual surface is traversed by a lingual intercuspid groove which passes without transition to the occlusal surface where it separates the cusp
disto-lingual of the 3 major cusps.
This groove ends in the middle of the lingual surface, halfway up the crown, with a well: the lingual well.
The lingual surface presents on the mesiolingual flank of the mesiolingual cusp the fifth cusp or tubercle of carabelli whose development is variable
This tubercle is underlined occlusally by a more or less anfractuous groove which may also be the only visible manifestation of this additional cusp.
Mesial face: the general shape of the crown is trapezoidal with a small occlusal base.
The occlusal contour is mainly marked by the mesial cusps. The mesiolingual cusp is shorter than the mesiovestibular cusp.
The vestibular contour has a marked bulge.
The lingual contour of the crown is strongly convex and presents the relief of the fifth cusp in its middle 1/3
In the mesial view, only the cusps MV; ML; and the carabelli tubercle (when present) are visible.
The mesial surface is convex in its occlusal 1/3; and the contact point is located at the junction of the vestibular 1/3 with the middle 1/3.
The cervical line is often irregular: it presents a slight convexity oriented towards the occlusal contour.
There is usually a mesial marginal groove that crosses the mesial marginal ridge in its middle.
The root:
The mesiovestibular root is wide and flat in the vestibulolingual direction. The lingual root appears narrow, “banana-shaped.”
It curves lingually from the root base, then moves towards the vestibular contour in the apical third.
This root projects outside the lingual coronal contour
Distal face : identical to the mesial view; the contact point is located in the center of the distal surface in its occlusal 1/3.
The distal surface is regularly convex
Occusal surface : This surface has the shape of a trapezoid with a large mesial base. The lingual edge is scalloped into two lobes;
The distal lobe is smaller than the mesial; the mesial lobe is doubled by the tubercle of carabelli when it exists
The almost flat mesial edge is the longest of the 4 edges.
The distal edge, a little convex, is approximately parallel to the mesial edge but shorter than it.
The proximal contours are cut approximately in their middle by the mesial marginal groove and by the distal marginal groove.
On this occlusal face we find 4 cusps;
3 furrows; 3 dimples and 2 marginal ridges
For the cusps, there are four of them: 2 vestibular cusps; 2 palatal cusps.
The strongest of the 4 cusps is the mesio-palatal, then the vestibulo-mesial, the vestibulo-distal and finally the disto-lingual.
The set of these two cusps; palato-mesial and vestibulo-distal are joined by a strong oblique ridge which is called an enamel bridge.
The mesiovestibular cusp and the mesiolingual cusp constitute, through their internal slopes, a transverse ridge
For furrows 3 intercuspal furrows; vestibulo-central, mesio-central and disto-palatal.
For the dimples 3 dimples: 2 main ones: The mesial dimple and the distal dimple
The roughly triangular central fossa located at the intersection of the mesiocentral intercuspal groove and the vestibulocentral intercuspal groove
The mesial triangular fossa is located medial to the mesial marginal ridge
The distal triangular fossa lies medial to the distal marginal ridge
.
For ridges; The mesial marginal ridge is longer and more prominent than the distal marginal ridge.
The central well is located in the deepest part of the central pit. It is the junction point of 3 furrows
The roots ; the upper molar has 3 roots;
Two vestibular; and one palatine
The most robust of the 3 is the palatine root then the vestibulo-mesial root and the smallest being the vestibulo-distal root.
General direction of roots:
1- vestibular roots : The vestibular roots are generally relatively narrow in the mesiodistal direction.
The mesial root is slightly convex on its mesial face and slightly concave on its distal face and its apex is directed towards the distal side.
The distal root; its arrangement is reversed; this root, slightly concave on its mesial face, is slightly convex on the distal face and its apex is turned towards the mesial side
In the vestibulo-palatine direction the two vestibular roots are approximately perpendicular to the crown
Palatal root: slightly inclined towards the distal side;
In the vestibulo-palatine direction diverging on the palatine side.
It is marked by a shallow depression that runs from the cervical line to the middle third of the root.
The apex is roughly aligned with the middle of the crown.
In the background, the mesial outline of the mesiovestibular root is fully visible.
Similarly, part of the distal outline of the distovestibular root is also visible
Pulp chamber; very large, has 4 horns corresponding to the 4 cusps.
The pulp chamber continues with 3 canals; 2 vestibular and 1 palatine; corresponding to the roots of the same name;
The most accessible of the three is the palatine canal, it is wide and almost straight; most often its direction is oblique from bottom to top in the palatal direction; it is slightly inclined on the distal side.
The vestibulo-mesial canal is difficult to access
It is much narrower than the previous one; it is flattened in the mesio-distal direction; its general direction is slightly oblique from bottom to top in the vestibular direction and in the distal direction.
It is curved with mesial convexity.
The vestibulo-distal canal is extremely thin in the same general direction as the previous one but curvilinear in the opposite direction
The second molar has many similarities with the upper first molar; however, we describe two variants:
The most common 4-cusp type is close to the 6-year-old tooth; the crown has a trapezoidal shape in occlusal view.
The occlusal area is formed by 4 cusps, but the distolingual cusp is reduced. The enamel bridge is of reduced size.
The 3-cusp type results from the disappearance or attenuation of the disto-lingual cusp.
In this case the coronal outline is similar to that of the wisdom tooth; it is triangular with a lingual summit in occlusal view.
The vestibulo-distal cusp is slightly smaller; between the vestibular cusps, a significant portion of the cusp is seen
Mesiolingual
The protrusion of the two palatine cusps is even more accentuated by the carabelli tubercle.
The occlusocervical dimension in mesial view is shorter than on the 1st molar while the vestibulolingual dimension is substantially equivalent.
The cervical third is clearly less concave than on the 1st molar.
The proximal contact zone is larger, more irregular, wider in the vestibulolingual direction. It is generally located in the middle third.
Roots: same general arrangement but more closely spaced; they tend to fuse, the palatine root is less divergent on the palatine side.
The vestibular roots are more inclined towards the distal contour.
The vestibular roots are generally relatively narrow in the mesiodistal direction.
It has long been accepted that each root contains a single canal. Recent work has shown that the mesio-vestibular root presents 2 canals in 60% of cases. The pulp chamber sees its vestibulo-lingual diameter decrease up to the cervical region
The upper third molar or wisdom tooth is the most variable of all teeth, in its size, shape, and eruption patterns.
It often presents developmental anomalies, however it can be close to the second upper molar, it is the least voluminous of the upper molars
Vestibular surface: the crown is narrower and less high than that of the second upper molar; the disto-vestibuliar cusp is reduced compared to its mesio-vestibular neighbor.
Lingual face: The distolingual cusp is very frequently absent: the occlusal contour therefore presents a single cusp, wide in the mesiodistal direction.
The distovestibular cusp is reduced.
A very large part of the occlusal face is visible when observed from the distal face
The coronal outline is triangular, sometimes “heart-shaped”. When it is well formed, its crown has only 3 cusps.
2 vestibular and 1 palatine
It is the disto-palatal cusp that disappears.
The enamel bridge , if not absent, is difficult to spot.
The roots are fused and their presence is only marked by furrows; sometimes these roots are well detached and their number varies from 3 to 5 or 6.
Upper molars
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