Upper premolars
Premolars
■ There are 8 of these teeth:
– 4 in the maxilla
– 4 in the mandible
■ These teeth arise from the 2nd 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
Timeline:
– Start of calcification: 1 ½ to 3 – 4 years
– Crown completed: 5 to 6 years
– Age of eruption: 10 to 11 years
– Completed root: 12 to 13 years
Average measurements:
– Total tooth height: 22.5mm
– Crown height: 8.5mm
– Root height: 14 mm
– Coronal mesio-distal diameter: 7 mm
– Coronal vestibulo-lingual diameter: 9 mm
A-The crown:
1-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 contact point 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 ridge is longer than the mesial ridge, which has the effect of shifting the cusp apex very slightly 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.
2-Lingual side:
– 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
3-Mesial face:
– 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.
4-Occlusal face:
– Fits into 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 the mesial slope)
– The mesio-distal groove ends on each side in 2 fossae, one mesial and one distal.
– From these dimples emerge the furrows which delimit the marginal ridges, therefore 2 marginal ridges, one mesial and one distal.
B-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 spreads out onto the crown.
C-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).
D-Inclinations in oral position:
VL Direction: – Crown: Vertical
- Roots: 12°
MD Direction: – Crown 1 to 2°
- Roots 4° to the Right: vestibular root Palatine root: vertical
The second upper premolar
Timeline:
– Start of calcification: 2 years to 2 1/2 years
– Crown completed: 6 to 7 years
– Age of eruption: 10 to 12 years
– Completed root: 12 to 14 years
Average measurements:
– Total tooth height: 22.5mm
– Crown height: 8mm
– Root height: 14.5 mm
– Coronal mesio-distal diameter: 6.5 mm
– Coronal vestibulo-lingual diameter: 8.5 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.
A-The crown:
1-Vestibular face:
– The crown is shorter and less wide, so it is more stocky.
– 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 top of the palatine cusp appear, very slightly offset to the mesial side.
2-Lingual side:
-The lingual cusp is almost as wide as the vestibular cusp, the proximal faces are practically invisible.
– Same silhouette and same modeling.
3-Proximal faces:
– The crown is 1/2 mm smaller / than the 1st upper premolar.
– The palatal cusp descends slightly lower than the vestibular cusp so the palatal face is at the same height as the vestibular face.
– The crown is 1/2 mm smaller / than the 1st upper premolar.
– The palatal cusp descends slightly lower than the vestibular cusp so the palatal face is at the same height as the vestibular face.
4-Occlusal face:
– The occlusal face has an oval section, the angles are less marked, 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 .
B- The root:
– It is almost always unique
– It is a little 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.
C-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.
D-Inclinations in oral position :
VP direction: -Crown: 2 to 5°
-Root: 10°
MD Direction: – Crown 1 to 2°
-Root 4°
Upper premolars
Impacted wisdom teeth may require surgery.
Zirconia crowns are durable and aesthetic.
Bleeding gums may indicate periodontitis.
Invisible orthodontic treatments are gaining popularity.
Invisible orthodontic treatments are gaining popularity.
Modern dental fillings are both durable and discreet.
Interdental brushes are ideal for narrow spaces.
Good dental hygiene reduces the risk of cardiovascular disease.