Maxillary premolars
The premolars There are 8 of these teeth:
■ There are 8 of these teeth: ■ These teeth are born 2nd
4 in the maxilla; 4 in the mandible dental lamina and replace the temporary molars when they fall out.
■ They erupt between the ages of 10 and 12 and mature completely between the ages of 12 and 14.
■ The maxillary premolars are in descending series, the second always being smaller than the first, while the mandibular premolars are in ascending series, the second always being larger than the first.
The upper first premolar
Chronology
1. Onset of calcification: 1 ½ to 3–4 years 3. Age of eruption: 10 to 11 years
2. Completed crown: 5 to 6 years 4. Completed root: 12 to 13 years
Average measurements
● Total tooth height: 22.5mm ● Mesio-distal coronal diameter: 7mm
● Crown height: 8.5mm ● Coronal vestibulo-lingual diameter: 9mm
● Root height: 14 mm
The crown
Vestibular face
● It has the same appearance as the upper canine, however it is smaller, therefore stockier.
● The tip of the free edge is less prominent (less acute cusp), so the “V” formed by it is more open.
● The mesial contour is concave from the neck to the point
contact which is located at the occlusal 1/3 of the crown height.
● The distal contour of the crown is more rounded and convex than the mesial contour.
● The distal contact point is more occlusal and is located at the occlusal ¼ of the crown height.
● The distal edge is longer than the mesial edge, which has the effect of very slightly shifting the cusp summit to the mesial side.
● The centro-vestibular lobe is by far the largest, it is separated into 2 slopes by a vestibular ridge which joins the cusp summit to the neck.
Lingual face
● It is narrower than the vestibular face
● The surface of the crown is strongly convex and smooth, devoid of any depression.
● The mesial and distal contours are strongly convex.
● The cusp summit is shifted to the mesial side.
● The proximal faces appear in this lingual view
Mesial face
● The general shape of the mesial coronal face is trapezoid
● the maximum vestibulo-lingual diameter is located at 1/3, between the peaks of the vestibular and lingual bulges.
● The vestibulo-lingual occlusal diameter is always smaller than that of the neck.
● the vestibular contour presents a bulge at 1/3 cervical.
● The lingual contour is rounded and lower than the vestibular contour, it has a bulge at the cervical ¼.
● The free edge has the shape of a circumflex accent, and is formed by the axial edges of the cusps, these edges are very convex.
● the collar has an almost rectilinear shape with a higher concavity.
● Modeled: the upper half of the mesial face is very concave, this concavity extends to the inter-radicular embrasure.
Distal face
● The contours are identical to those of the mesial face.
● The marginal crest is higher and reveals a larger part of the occlusal face; it is oblique from bottom to top in the palatal direction.
● The shape of the coronal face is convex
Occlusal face
● is inscribed in a pentagon with unequal sides. It is made up of 2 very prominent cusps, of which the vestibular is the strongest (Vestibulo-lingual diameter 9 mm, mesiodistal diameter 7 mm)
● The vestibular edge forms a sinuous line in the shape of a circumflex accent made up of 3 lobes.
● The palatal edge is more reduced than the vestibular edge and forms an arch with palatal convexity.
● The proximal faces are oblique and converge lingually.
● the occlusal face itself or functional is enclosed within the limits of the transverse edges.
● the palatal transverse ridge is further from the palatal edge (1.5 mm) than the vestibular transverse ridge from the vestibular edge (1 mm).
● The main mesio-distal groove is straight in occlusal view, it is closer to the palatine edge, the vestibular cusp being larger.
● The axial edges of the 2 cusps form a broken line with mesial concavity (distal slope larger than mesial rise)
● The mesio-distal groove ends on each side in 2 dimples, one mesial and one distal.
● From these pits emerge the furrows which delimit the marginal ridges, therefore 2 marginal ridges, one mesial and one distal.
The root
● Bifid
● The vestibular and lingual roots separate in the apical half of the root zone from the root bifurcation.
● The mesial surface of the root trunk is strongly concave, over the entire height of its middle third, while the vestibular and lingual thirds are convex.
● This depression is extended by the mesial coronal depression.
● The vestibular root is stronger and a little longer than the palatine root (0.5 mm) these 2 roots are cylindrical and increasingly tapered towards their apex.
● Between the embrasure and the anatomical collar, a strongly marked furrow accentuates the separation of the 2 roots, and flourishes on the crown
The pulp chamber
● It is quite large, it has 2 pulp horns:
– 1 vestibular pulp horn which is the most important – 1 palatine pulp horn
-.
● The pulp floor provides access to 2 root canals:
1 vestibular canal and 1 lingual canal (usually wider)
VL Direction : Crown: Vertical Roots: 12°
Oral position tilts
MD Direction : Crown 1 to 2°
Roots 4° to the Right: vestibular root
Palatal root: vertical
The second upper premolar
Chronology
1. Start of calcification: 2 to 2 ½ years 3. Age of eruption: 10 to 12 years
2. Completed crown: 6 to 7 years 4. Completed root: 12 to 14 years
Average measurements
● Total tooth height: 22.5mm ● Coronal mesio-distal diameter: 6.5 mm
● Crown height: 8mm ● Coronal vestibulo-lingual diameter: 8.5 mm
● Root height: 14.5 mm
● The morphological characteristics are almost identical to those of the 1st upper premolar. It is also long, but very slightly less strong and its root is very rarely bifid.
● We will point out, by face, the main differences between these 2 teeth.
The crown
Vestibular face
● the crown is shorter and less wide, so it is stockier.
● The contact points (at the mesial and distal contours) are approximately at the same height (1/3 occlusal)
● The divergence of the mesial and distal contours is less important from the neck.
● we see the summit of the palatal cusp appear, very slightly offset to the mesial side.
Lingual face
● the lingual cusp is almost as wide as the vestibular cusp, the proximal faces are practically invisible.
● Same silhouette and same modeling.
Proximal faces
● The crown is 1/2 mm smaller / than the upper 1st premolar .
● The palatal cusp descends slightly lower than the vestibular cusp so the palatal face is at the same height as the vestibular face.
View-my- view-dis
Occlusal face ● The occlusal face has an oval section, the angles are less marked and more rounded
● The mesiodistal groove is in the middle of the occlusal surface.
● the vestibular and palatal cusps are of equal value: the occlusal face is divided into 2 equal halves.
● Overall, the cusps are less prominent than on the 1st premolar , because the fossae are less deep at the level of the 2nd premolar .
The root
● It is almost always unique
● It is slightly longer than the roots of the 1st premolar and flatter in the mesio-distal direction.
● The proximal faces are traversed by a vertical groove along its entire length. It is less marked on the mesial side.
The pulp chamber
● It has 2 pulp horns opposite the vestibular and lingual cusps.
● It is smaller than that of the 1st premolar
● The pulp chamber ends with a single canal that is very wide and flattened in the mesio-distal direction .
● the canal can split into 2 canals, in the apical half, each having an apical foramen.
Oral position tilts
VP direction: Crown: 2 to 5°
Root: 10°
MD Direction: Crown 1 to 2°
Root 4
Maxillary premolars
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