Tag Archives: Anatomy

A Guide To Dental Anatomy

Dental anatomy is defined  as, the study of the development, morphology, function, and identity of each of the teeth in the human dentitions, as well as the way in which the teeth relate in shape, form, structure, color, and function to the other teeth in the same dental arch and to the teeth in the opposing arch. Thus, the study of dental anatomy, physiology, and occlusion provides one of the basic components of the skills needed to practice all phases of dentistry.

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CHRONOLOGY OF PRIMARY TEETH

primary teeth ERUPTION

CHRONOLOGY OF PERMANENT TEETH

permanent teeth eruption

THE PERMANENT MAXILLARY INCISORS

The maxillary central incisor is larger than the lateral incisor. These teeth supplement each other in function, and they are similar anatomically.

PERMANENT MAXILLARY CENTRAL INCISOR

The maxillary central incisors are esthetically the most prominent teeth in the mouth. An ideal smile should have incisal dominance, i.e. maxillary incisors should be the most prominent teeth visible when one smiles. Any defects in the form and alignment of these teeth are easily noticed, and adversely affect the normal facial appearance

First evidence of calcification 3–4 mo
Enamel completed 4–5 yr
Eruption 7–8 yr
Root completed 10 yr

maxillary central inciser

Maxillary Lateral Incisor

Because the maxillary lateral incisor supplements the central incisor in function, the crowns bear a close resemblance. The lateral incisor is smaller in all dimensions except root length. This tooth differs from the central incisor in its development, which may vary considerably. Maxillary lateral incisors vary in form more than any other tooth in the mouth except the third molar. If the variation is too great, it is considered a developmental anomaly. A common situation is to find maxillary lateral incisors with a nondescript, pointed form; such teeth are called peg-shaped laterals.

First evidence of calcification 10–12 mo
Enamel completed 4–5 yr
Eruption 8–9 yr
Root completed 11 yr

The Permanent Mandibular Incisors

The mandibular incisors have smaller mesiodistal dimensions than any of the other teeth. The central incisor is somewhat smaller than the lateral incisor, which is the reverse of the situation in the maxilla.

Mandibular Central Incisor

Generally, the mandibular central incisor is the smallest tooth in the dental arches. The crown has little more than half the mesiodistal diameter of the maxillary central incisor; however, the labiolingual diameter is only about 1 mm less. The single root is very narrow mesiodistally and corresponds to the narrowness of the crown, although the root and crown are wide labiolingually. The length of the root is as great as, if not greater than, that of the maxillary central incisor.

mandibular central inciser

First evidence of calcification 3–4 mo
Enamel completed 4–5 yr
Eruption 6–7 yr
Root completed 9 yr

Mandibular Lateral Incisor

Direct comparison is made with the mandibular central incisor, and the variations are mentioned. The two incisors operate in the dental arch as a team; therefore their functional form is related. As with the mandibular central incisor, the shape of the lateral incisor is uniform compared with that of other teeth. Rarely, it will have a labial and lingual root division in the cervical third. Somewhat more commonly it has two canals in the single root.

First evidence of calcification 3–4 mo
Enamel completed 4–5 yr
Eruption 7–8 yr
Root completed 10 yr

The Permanent Canines: Maxillary and Mandibular

The maxillary and mandibular canines bear a close resemblance to each other, and their functions are closely related. The four canines are placed at the “corners” of the mouth; each one is the third tooth from the median line, right and left, in the maxilla and mandible. They are commonly referred to as the cornerstone of the dental arches. They are the longest teeth in the mouth; the crowns are usually as long as those of the maxillary central incisors, and the single roots are longer than those of any of the other teeth.

Maxillary Canine

Figures illustrate the maxillary canine in various aspects. The outline of the labial or lingual aspect of the maxillary canine is a series of curves or arcs except for the angle made by the tip of the cusp. This cusp has a mesial incisal ridge and a distal incisal ridge. The mesial half of the crown makes contact with the lateral incisor, and the distal half contacts the first premolar. Therefore the contact areas of the maxillary canine are at different levels cervicoincisally. (maxillary right canine)

maxillary canine

 

First evidence of calcification 4–5 mo
Enamel completed 6–7 yr
Eruption 11–12 yr
Root completed 13–15 yr

Mandibular Canine

The mandibular canine crown is narrower mesiodistally than that of the maxillary canine, although it is just as long in most instances and in many instances is longer by 0.5 to 1 mm.

The root may be as long as that of the maxillary canine, but usually it is somewhat shorter. The labiolingual diameter of crown and root is usually a fraction of a millimeter less. The lingual surface of the crown is smoother, with less cingulum development and less bulk to the marginal ridges. The lingual portion of this crown resembles the form of the lingual surfaces of the mandibular lateral incisors.

The cusp of the mandibular canine is not as well developed as that of the maxillary canine, and the cusp ridges are thinner labiolingually. Usually the cusp tip is on a line with the center of the root, from the mesial or distal aspect, but sometimes it lies lingual to the line, as with the mandibular incisors.

mandibular canine

First evidence of calcification 4–5 mo
Enamel completed 6–7 yr
Eruption 9–10 yr
Root completed 12–14 yr

 The Permanent Maxillary Premolars

The maxillary premolars are developed from the same number of lobes as anterior teeth—four. The primary difference in development is the well-formed lingual cusp, developed from the lingual lobe, which is represented by the cingulum development on incisors and canines. The middle buccal lobe on the premolars, corresponding to the middle labial lobe of the canines, remains highly developed, with the maxillary premolars resembling the canines when viewed from the buccal aspect.

The buccal cusp of the maxillary first premolar, especially, is long and sharp, assisting the canine as a prehensile or tearing tooth. The mandibular first premolar assists the mandibular canine in the same manner. The second premolars, both maxillary and mandibular, have cusps less sharp than the others, and their cusps articulate with opposing teeth when the jaws are brought together; this makes them more efficient as grinding teeth, and they function much like the molars, but to a lesser degree.

The maxillary premolar crowns are shorter than those of the maxillary canines, and the roots are also shorter. The root lengths equal those of the molars. The crowns are a little longer than those of the molars. Because of the cusp development buccally and lingually, the marginal ridges are in a more horizontal plane and are considered part of the occlusal surface of the crown rather than part of the lingual surface, as in the case of incisors and canines. When premolars have two roots, one is placed buccally and one lingually.

Maxillary First Premolar

The maxillary first premolar has two cusps, a buccal and a lingual, each being sharply defined. The buccal cusp is usually about 1 mm longer than the lingual cusp. The crown is angular, and the buccal line angles are prominent. The crown is shorter than that of the canine by 1.5 to 2 mm on the average.maxillary first premolar

First evidence of calcification 11/2–13/4 yr
Enamel completed 5–6 yr
Eruption 10–11 yr
Root completed 12–13 yr

Maxillary Second Premolar

The maxillary second premolar supplements the maxillary first premolar in function. The two teeth resemble each other so closely that only a brief description of each aspect of the second premolar is necessary. Direct comparison is made between it and the first premolar, and variations are mentioned.

The maxillary second premolar is less angular, giving a more rounded effect to the crown from all aspects. It has a single root.

Considerable variations in the relative sizes of the two teeth may be seen, because the second premolar does not appear true to form as often as does the first premolar. The maxillary second premolar may have a crown that is noticeably smaller cervico-occlusally and also mesiodistally.

First evidence of calcification 2– 21/4 yr
Enamel completed 6–7 yr
Eruption 10–12 yr
Root completed 12–14 yr

The Permanent Mandibular Premolars

The mandibular first premolars are developed from four lobes, as were the maxillary premolars. The mandibular second premolars are, in most instances, developed from five lobes, three buccal and two lingual lobes.

The first premolar has a large buccal cusp, which is long and well formed, with a small, nonfunctioning lingual cusp that in some specimens is no longer than the cingulum found on some maxillary canines. The second premolar has three well-formed cusps in most cases, one large buccal cusp and two smaller lingual cusps. The form of both mandibular premolars fails to conform to the implications of the term bicuspid, a term that implies two functioning cusps.

Mandibular First Premolar

This tooth is situated between the canine and second premolar and has some characteristics common to each of them.
The characteristics that resemble those of the mandibular canine are as follows:
1. The buccal cusp is long and sharp and is the only
occluding cusp.
2. The buccolingual measurement is similar to that of
the canine.
3. The occlusal surface slopes sharply lingually in a
cervical direction.
4. The mesiobuccal cusp ridge is shorter than the
distobuccal cusp ridge.
5. The outline form of the occlusal aspect resembles the
outline form of the incisal aspect of the canine.

The characteristics that resemble those of the second mandibular premolar are as follows:
1. Except for the longer cusp, the outline of crown and
root from the buccal aspect resembles that of    the second premolar.

2. The contact areas, mesially and distally, are near the
same level.

3. The curvatures of the cervical line mesially and distally are similar.

4. The tooth has more than one cusp.

mandibular first premolar

First evidence of calcification 13/4–2 yr
Enamel completed 5–6 yr
Eruption 10–12 yr
Root completed 12–13 yr

Mandibular Second Premolar

The mandibular second premolar resembles the mandibular first premolar from the buccal aspect only. Although the buccal cusp is not as pronounced, the mesiodistal measurement of the crown and its general outline are similar. The tooth is larger and has better development in other respects.

First evidence of calcification 21/4-21/2 yr
Enamel completed 6–7 yr
Eruption 11–12 yr
Root completed 13–14 yr