Descriptive anatomy of temporary teeth

Descriptive anatomy of temporary teeth

1. Generality

They are also called: deciduous teeth, primary teeth, occasional teeth or even baby teeth.

When they have all completed their development, they form a real temporary dental system which has the role of:

• Preparing the food bowl
• Maintaining the child’s vertical occlusion dimension 
• Maintaining space for permanent teeth and guiding their eruption.
• The essential aid for learning phonation .

These teeth will function as a complete temporary dentition for 04 years, they will then be replaced by permanent teeth until the age of 11 to 12 years for some of them. The exfoliation process takes place between 7 and 12 years.

2. The dental formula

The temporary dentition presents by hemi-arch:

– two incisors: a central one and a lateral one which will be replaced by the permanent incisors.

– A canine replaced by the permanent canine.

– Two molars replaced by permanent premolars

The dental formula is established as follows:

2i+1c+2m

2i+1c+2m

3. Differential characteristics between temporary and permanent teeth:

3. 1. External differential characters:

• The temporary teeth are smaller except for the temporary molars whose mesio-distal diameter is larger than that of the premolars.
• The crowns of temporary teeth are covered with a more opaque and thinner enamel, which gives them a characteristic milky appearance.
• The temporary molars have an adamantine eminence in the 

1/3 cervical coronal vestibular and lingual. 

• The crown of temporary teeth represents 1/3 of the height

 total, while the ratio of crown height to total tooth height 

permanent is of the order of 35 to 45%

• The ratio of maximum mesio-distal diameter/coronal height is more 

important than that of permanent teeth.

• The difference between the largest coronal diameter (occlusal region) 

 and the smaller coronal diameter (cervical region) is important on 

       temporary teeth.

• The roots of temporary teeth are thinner and longer than 

those of the permanents. 

• The roots of the temporary molars diverge strongly from the neck 

3. 2. Internal morphological characteristics:

• Dentin is thinner on temporary teeth
• The pulp horns are very sharp, they rise very high under the cusps 
• The pulp chamber ceiling is more convex and more deeply embedded in the crown, which accentuates the thickness of the occlusal dentin.
• Pulp volume is important 

4. Anatomical description of temporary teeth
5. The incisors
6. Timeline:

1. Average measurements:
2. Average measurements: 

3. Description

c.1. the upper central incisor:

c.1.1 The crown: 

• Vestibular face: 
• It is the only unit of the incisor-canine group, both maxillary and mandibular, which

 has a mesio-distal diameter greater than the coronal height

• The proximal faces have strongly convex contours; the mesial contour is

 more convex distally.

• The mesial incisal angle is well marked, the distal incisal angle is convex.
• Edge I is straight and slightly inclined on side D.

• Palatal face: 
• The palatal face is narrower than the vestibular face.
• The cingulum is strongly convex.
• The FP does not have any furrows or depressions. There are no wells.

 cingulate.

• Proximal faces: 
• The mesial and distal views are identical. The maximum convexity is at the level of the cervical ¼. A real enamel rim underlines the enamel-cement junction which is at a sharp angle.

• Incisor face: 
• The general outline of the tooth is diamond-cut.
• The mesiodistal diameter is larger than the vestibulolingual diameter.
• The tooth is symmetrical, the incisal edge is straight
• The summit of the cingulum is more often median, it can be offset either

 distally or mesially. 

c.1.2 The root

The root contours converge to a pointed apex. The root surface is convex.

c.2. the upper lateral incisor

c.2.1 The crown:

• Vestibular face: 
• The proximal contours are less convex;
• The distal incisal angle is very rounded, the free edge straight and inclined distally.
• The distal part of the incisal edge is more cervical than the mesial part. 

• Palatal face: 
• The palatine surface is narrower than the vestibular surface; the palatine fossa is deeper.
• The cingulum is centered on the face; the marginal ridges are more accentuated.

• Proximal faces: 
• The cervical line is strongly convex in the direction of the incisal edge.
• The cervical convexity is more palatal than the vestibular.

• Incisor Face:
• The general outline of the tooth is almost circular. 
• The vestibular surface is more convex in the mesio-distal direction.
• The incisal edge is curved, often the apex of the cingulum is median

exceptionally offset to the distal side.

c.2.2. The root  : the root is conical, its apex is pointed

c.3. the lower central incisor

c. 3.1 The Crown

• Vestibular face: 
• the tooth is perfectly symmetrical
• The proximal contours are convex 
• The mesial and distal incisal angles form a right angle 
• The incisal edge is straight and perpendicular to the long axis of the tooth
• The vestibular surface is flat

• Lingual face:
• The lingual surface is concave, the cingulum is important, it rises up to ½ of 

the crown height.

• The cingulum is centered and there are no accessory tubercles

• Proximal faces  :

 The cervical line is moderately convex towards the incisal edge. 

The cervical convexities are identical to those of the maxillary units. 

• Incisor face: 
• The free edge is straight and divides the occlusal face into 2 halves. 
• The vestibular contour is circular, 
• The lingual contour is much narrower due to convergence of the faces

 proximal. 

c.3.2. The root is conical and its apex is pointed

c.4. the lower lateral incisor

There is little difference with the central incisor, only the general shape of the

 crown is more rounded on the distal side in vestibular view. 

The free edge is always straight. 

It should be noted in occlusal view that the free edge has a lingual concavity and that it is 

elbow on the distal side. 

The top of the cingulum is often shifted to the distal side.

2. Canines:
3. Timeline:

b. Average measurements:

c.Description:

c.1. Upper canine

c.1.1 The crown

• Vestibular face:
• The reduced cervical diameter gives it the shape of a cut diamond,
• the mesial contour has a peak located halfway up the crown it is more 

convex than the distal.

• The distal contour is more occlusal than the mesial contour
• The cusp apex is shifted to the distal side.
• The vestibular surface is strongly convex.

• Palatal face: 
• We find on this tooth the same anatomical elements as the permanent tooth:

 cingulum, marginal ridge and median enamel ridge

• The cingulum sometimes bears two tubercles on its incisive part and an arc-shaped groove separates them from the palatine fossa.

• Proximal face: 
• The maximum vestibular convexity and the maximum palatal convexity are located

 in the coronal cervical third, they form a ridge of enamel.

• The cingulum is strongly prominent and occupies half of the coronal height.

• Occlusal face: 
• The tooth has a diamond appearance with well-defined faces and edges.
• The cusp apex is distal and the mesial contour is longer than the distal contour.

c.1.2. The root:

The root is long, smooth, conical and ends with a rounded apex and is generally bent in its 1/3 apica.

c.2. Lower canine

c.2.1. The crown

• Vestibular face:
•  The coronal height is greater than the mesio-distal diameter.
• The mesial contour may exhibit maximum convexity at the junction of the 

incisal third and middle third.

• The distal contour has a maximum convexity located at mid-coronal height.
• The cusp summit is distal, and more acute than that of the mandibular canine 

permed. 

• Lingual face: 

The marginal ridges are not very pronounced. There is no groove on the lingual surface. 

• Proximal faces  : 
•  The vestibulolingual diameter is smaller than that of the maxillary canine.

The cingulum is not very prominent. It occupies less than a third of the coronal height.

• Occlusal face: appearance similar to that of the maxillary canine, i.e.

 diamond appearance. 

c.2.2. The root  : the root is conical, long and smooth. It ends with a rounded apex.

3. Molars:
4. Timeline:
5. Average measurements:
6. Description :

c.1- The first upper molar:

• Vestibular face:
• The crown
• This is the most atypical of dental units, it is generally bicuspid, 

two cusps can be found on its distal portion. 

• The crown is wide in the mesio-distal direction, short in the 

cervical occlusion; 

• The proximal contours are convex and converge towards the cervical region.
• The occlusal contour is scalloped, the mesio-vestibular cusp is blunt,

 the disto-vestibular cusp when it exists only presents a quarter of the 

mesio-distal vestibular diameter.

• The convex vestibular coronal surface in the cervical third especially below the 

 mesio-vestibular cusp where we find the Zuckerkandl tubercle.

•  Roots:
• There are 3 roots: 2 vestibular roots 1 palatine root. They are thin and elongated
• The root trunk is practically non-existent. The bifurcation originates at the 

collar

• The mesio-vestibular root is longer than the disto-vestibular root. They are

 both project outside the coronal contours.

• Palatal face: 
• The crown:
• This face is narrower than the vestibular.
• The mesiopalatal cusp is more acute, there is no deep groove.

• Roots:
• The 3 roots are visible
• The lingual root originates directly at the neck. It is wide conical and 

ends with a rounded apex

• Proximal faces:
• The crown:
• The mesial view is characteristic, the vestibular contour is strongly convex especially in the cervical region
• The distal face is narrower. 

• Roots:
• The roots project outside the coronal contours. They are arcuate in appearance. They are oriented outside the coronal contours in their cervical third and in their median third, then curve towards the general axis of the tooth in their apical third. 
•  The disto-vestibular root is the shortest and narrowest

• Occlusal face:
• The tooth is wider on the mesial side than on the distal side, the mesio-vestibular angle is very acute.
• When it only has two cusps, these are of equivalent value and their occlusal edges constitute a transverse crest and a mesio-distal intercuspid groove separates the vestibular cusp from the palatine cusp and joins the mesial marginal fossa to the distal one. 

c.2- The second upper molar:

• Vestibular face: 
• The crown:
• Resembles the first permanent molar; the dimensions are smaller in all directions, the mesio-distal diameter is greater than the coronal height.
• The disto-vestibular cusp is important.
• The separation between the two vestibular cusps is deep and marked.
• The cervical constriction is strongly pronounced.
• The vestibular surface is marked by a strong convexity in the cervical region.

• Roots:
• It also has 3 roots which are more important than the first one 

molar.

• Sometimes the disto-vestibular root and the palatine root form only one 

one and only root

• The root trunk is small or non-existent
• The roots are thin, long and more divergent than on the 1st ^molar .

• Palatal face: 
• Crown
• Its dimensions are smaller 
• The Carabelli tubercle can be deep. 

• Roots:

The roots are thin, long and more divergent than on the 1st ^molar . 

• Proximal faces: 
• Crown
• With reduced dimensions the vestibulopalatine diameter is greater than the coronal height.
• Roots:

They project outside the coronary contours in their cervical and median thirds then curve sharply in their apical thirds. 

• Occlusal face: 
• When it has four cusps, these are in decreasing order: mesio-palatine, mesio-vestibular, disto-vestibular, disto-palatine.
• The central slopes of the mesiopalatine and mesiovestibular cusp form a transverse ridge never cut by a groove.
• The vestibulolingual diameter is larger than the mesiodistal diameter.
• The mesial marginal ridge has an important structure of this tooth, it sometimes bears two tubercles separated by a groove.

c.3) The first lower molar:

This tooth is unlike any temporary or permanent cusped tooth. It usually has 4 cusps (2 vestibular and 2 lingual). It may have a 5th DV cusp.

• Vestibular face: 
• Crown  :
• It is as atypical as its antagonist. There is a clear disproportion between the mesial and distal part.
•  The mesio-vestibular cusp occupies two-thirds of the mesio-distal diameter. 
• The mesial contour is straight and slightly overhangs the mesial root contour. 
• The distal contour is convex and projects outside the distal root contour. 
• The occlusal contour is marked by the presence of 2 cusps separated by a shallow groove. This contour is saw-toothed.
• Cervical constriction exists, but it is less marked than on the second mandibular molar. 
• The vestibular surface is convex in its cervical and mesial part and rather flat in its occlusal half. 

• Roots:
• There are 2 roots: one mesial and one distal. 
• The mesial root is longer and wider than the distal root.
• The root trunk is not very important

• Lingual face:
• Crown the vestibular cusps are visible when observed by this face. There are 2 cusps: the mesio-lingual cusp is more important, it represents two thirds of the mesio-distal diameter, and the disto-lingual cusp is a small protuberance.

• Roots:

The roots are proportionally larger than on the second

 lower molar 

• Proximal faces: 
• Crown :
• The occlusal area has a reduced diameter in the vestibulolingual direction. The 4 cusps are visible when observed from the distal face. 
• Roots: The mesial root masks the distal root. It has a longitudinal depression over its entire height. The apex is often bifid

• Occlusal face: 
• The general shape is that of a diamond whose acute angles are represented by the mesio-vestibular angle and by the disto-lingual angle.
• the 4 cusps are visible, they are in decreasing order: mesio-vestibular cusp, disto-vestibular, mesio-lingual and disto-lingual.
• The central slopes of the mesio-vestibular and mesio-lingual cusps form a prominent ridge. 
• The cusps are separated from each other by the mesiodistal central groove, vestibular groove and lingual groove. 
• The mesial marginal ridge is consistently present. The distal marginal ridge is reduced or absent. 

c.4) The second lower molar:

• Vestibular face:
• Crown  : 
• The resemblance  to the mandibular 1st ^permanent   molar is found in the general shape and arrangement of the cusps and grooves. 
• The mesiodistal diameter is greater than the coronal height. 
• The occlusal contour is marked by the presence of 3 cusps: mesio-vestibular, disto-vestibular and distal cusps separated by grooves which generally end in wells.
• The cervical region is severely constricted. 
• The vestibular surface is convex in its cervical part and rather flat in its occlusal half. 

• Root :
• The roots are narrow, slightly curved and strongly divergent.
• The root trunk is small or non-existent
• The roots are thin, long and more divergent than on the first

 molar 

• Lingual face:
• Crown :
• The vestibular cusps are barely visible when viewed from this side, due to the height of the lingual cusps. There are 2 cusps: mesio-lingual and disto-lingual, which are equivalent. 

• Root :

The roots are thin, long and more divergent than on the first molar.

• Proximal faces:
• Crown :
• The mesiolingual cusp is often hidden by the distolingual cusp at  

the observation of this face.

• Root :
• The roots are very wide in the mesio-distal direction 

• Occlusal face: 
• The general shape is trapezoidal
• It generally has 5 cusps which are, in decreasing order: mesio-vestibular, mesio-lingual, disto-vestibular, disto-lingual and distal. 
• The vestibulolingual diameter is less important than the mesiodistal diameter.
• The mesial marginal ridge is reduced or absent and the distal ridge is most often absent. 

Descriptive anatomy of temporary teeth

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Descriptive anatomy of temporary teeth