The Pulp Tissue and Pulp Cavity

Dentists Be Damned

Tooth Pain Natural Treatment

Get Instant Access

A. Introduction:

It is not the purpose of this section to preempt the basic sciences by describing pulp histology and physiology in detail. Hence, only a very brief review of the salient features will be presented.

B. Anatomy of the Pulp Cavity:

The pulp tissue is the soft connective tissue which is found in the central portion of the tooth, entirely surrounded by dentin. The cavity, or space, in which the pulp tissue is located is divided into the following anatomical entities.

1. Pulp cavity - The pulp cavity is the entire central space in the dentin of a tooth, both root and crown, which contains the pulp tissue in a vital tooth. The outline of the pulp cavity generally corresponds to the external contour of the tooth, especially in newly erupted teeth. However, its size and contour in any individual tooth is related to the extent that normal physiologic aging has occurred, and that external factors such as pathology and occlusion have stimulated secondary dentin production.

2. Pulp chamber - The portion of the pulp cavity which is located roughly in the anatomical crown of the tooth. It is normally larger in diameter than any portions of the pulp cavity found in roots.

3. Pulp canal(s) - The section of the pulp cavity which is located basically in the anatomical root of the tooth, or in other words, that portion which is apical to the pulp chamber. Another term which is appropriate is root canal.

4. Pulp horn(s) - The pulp horns are the pointed incisal (occlusal) limits of the pulp cavity and pulp chamber, which actually look like horns in many cases. They often reflect the lobe and cusp pattern of a tooth's crown.

5. Apical foramen (pi.-foramina) - The constricted opening(s), at, or near the root apex, through which the main nutrient and nervous supply to the pulp enter and exit. The apical foramen is thus the apical limit of the pulp cavity.

6. Lateral (Accessory) canals - Minute canals which usually extend in a lateral or roughly horizontal direction from the pulp to the periodontal membrane. They are most often found in the apical half of the root, and are a minor source of nutrient supply to the pulp.

7. Supplementary canal - A root canal, or branch, which is in excess of the normal number of root canals found in a root. They serve the same functions as the main root canal(s), but are not present in all teeth.

8. Anastomosis (pl.-anastomoses) - An extra canal branch which horizontally connects pulp canals with each other, or with supplementary canals.

C. Physiology of the Pulp Tissue:

The pulp tissue functions in four major capacities for the dental organ:

1. Formation of dentin: The dentinogenesis process is a function of the odontoblasts, which are cells that differentiate from the peripheral portion of the pulp. The primary dentin is normally laid down only during the period of tooth formation and ends when root development is complete. All dentin production does not necessarily cease following tooth maturation, however. The pulp is still capable of initiating the formation of secondary dentin at any time during the rest of its life, in both primary and permanent teeth. There are two types of secondary dentin, reparative and physiological, which differ from each other histologically, and from primary dentin both macroscopically (mainly color) and microscopically. Reparative dentin forms in response to acute or chronic irritants such as caries, thermal and functional trauma, and mechanical causes. In reality, this is a defensive and protective mechanism. Physiological secondary dentin may be deposited in a rather consistent and uniform manner, as a normal phenomenon of the aging process.

2. Nutrition - This function maintains pulpal vitality, and is carried on by the blood and lymph vessels found in the pulp tissue. Their entrance and exit to the pulp cavity is chiefly through the apical foramen. There is some auxiliary supply from the periodontal membrane.

3. Sensation - The nerve tissue found in the pulp is responsible for relaying sensations to the brain centers. Not only do pain sensations occur, but the sensory function of the entire masticatory mechanism is coordinated.

4. Defense and Protection - The pulp is capable of responding to an irritant, such as progressive caries, through inflammation, which is the classic defense mechanism of the body. This process may eventually result in the differentiation of odontoblasts, and the formation of reparative secondary dentin.

D. Pulp Canal Development:

Early in the development of the root, the pulp canal is funnel-shaped at the root apex, with the greatest width of the funnel at the apex. Consequently, during much of the period of root development the pulp canal is widest in diameter at the apex. For this reason, endodontic therapy is difficult to perform successfully during this period, and is normally postponed until root formation has ceased. The completion of the apical portion of the root continues with primary dentin deposition, and the funnel-shaped opening is filled in until only a small opening, the apical foramen, is present. This is the point in time when root and root canal development are considered to be complete.

E. Changes in the pulp cavity with age:

As previously indicated, the pulp tissue maintains the capacity to produce dentin as long as the pulp remains vital. This is secondary dentin, as contrasted to the primary dentin produced during tooth development. Secondary dentin production reduces the dimensions of the pulp cavity, which may be either in the form of a general reduction in size (physiological), or specific to an area of stimulation (reparative). When one, or both of these processes is occurring, pulp cavity dimensions are reduced. In the young tooth, the pulp horns are prominent elongations of the pulp chamber. With age, these extensions are often blunted, and sometimes even obliterated, so that the teeth of older individuals may not exhibit pulp horns. The same is true of the remainder of the pulp cavity, so that as the tooth ages, the pulp cavity normally decreases in size.

III. Sectioning of the Pulp Cavity:

In the remaining text of this unit, pulp cavity anatomy will be described for individual permanent teeth. It is necessary, then, to briefly discuss the various views of the pulp cavity which may be produced by sections through different areas of the tooth.

As was previously mentioned, normal periapical radiographs (x-rays) of the teeth are taken in a faciolingual direction, thus outlining the pulp cavity in a mesiodistal section. However, the pulpal contours from this aspect are less variable than are those from a proximal aspect. Consequently, faciolingual sections exhibit more variability. Unfortunately, faciolingual sections are not normally feasible to the practitioner through x-rays.

Besides the mesiodistal and faciolingual sections which are vertical, knowledge of the anatomy in horizontal cross sections, at various levels of the pulp cavity, is valuable. Again, these cross sections are not possible with ordinary x-ray techniques. During the next section of the text, cross sections through the cervical line area and mid root level will be described for each tooth. These cross sections would be a welcome addition to the armamentarium of the endodontist, especially the mid-root section, which would most likely reveal the presence of supplementary root canals.

IV. Pulp Cavities of the Individual Permanent Teeth:

A. Introduction:

1. The outline of the pulp cavity generally corresponds to the external contour of the tooth. This is very important, since it provides some knowledge of the contour of the pulp cavity without direct vision of it. In addition, the necessary background should be fresh in the student's mind with completion of the immediately preceding units on individual permanent teeth. The general shape of the crown can be utilized to provide a good indication of the shape and dimensions of the pulp chamber. For example, in anterior teeth where the labial and lingual surfaces are trapezoidal and widest at the incisal, the pulp chamber is also widest toward the incisal. From either proximal, the pulp chamber is pointed at the incisal, and widest at the cervical, corresponding to the triangular-shaped proximal surfaces of anterior teeth. So, if the external anatomy of the teeth just studied is kept in mind, it will be easier to relate to the contours and dimensions of the pulp cavity. Cuspal anatomy can even be used to determine the heights and contours of the pulp horns, especially in posterior teeth.

2. Another general rule suggests that in multirooted teeth there will be at least one root canal in each root branch. Furthermore, tooth roots with round cross sectional outlines generally possess one canal, whereas roots with oval or elongated cross sectional outlines often contain more than one canal.

B. Maxillary Incisors:

1. Introduction:

Similarity between the pulp cavities of the maxillary central and lateral incisors is marked, since their general form is so similar. The pulp cavity outline reflects the external surface outline, as is generally the case with all teeth. The only real difference, excluding relative size, concerns pulp horn anatomy, where, the newly erupted central incisor normally exhibits three pulp horns, and the lateral incisor most often reveals either two or none. The pulp chamber is wider mesiodistally, in contrast to the maxillary canine and premolars, where the chamber is normally wider faciolingually.

2. Labiolingual Section:

a. Pulp chamber - At its incisal extremity, the pulp chamber is pointed, and gradually thickens to its widest point at about the mid cingulum level. The labial outline is slightly convex, while on the lingual there is usually a rounded hump which corresponds to the external contour of the cingulum.

b. Pulp canal - From approximately the cervical line, the outline of the single pulp canal tapers evenly to the apical foramen, generally following the contour of the root. The foramen is quite constricted, except in young teeth.

Mesiodistal Section:

a. Pulp chamber - From this aspect, the chamber outline is widest at the incisal, and tapers fairly evenly to the cervical line level. The three pulp horns, corresponding to the three labial lobes, are prominent and pointed in young central incisors (laterals have two or none). In some specimens there is a slight mesiodistal widening, or bulge, at the cervical line. The mesiodistal dimension of the pulp chamber is generally greater than the labiolingual dimension.

b. Pulp canal - From the cervical line, the pulp canal outline tapers rather evenly to the constricted apical foramen, again following the external root contour.

4. Cervical Cross Section - In newly erupted centrals, the pulp outline may be somewhat triangular like the root outline, but with age, the outline becomes generally circular. The outline for the lateral incisor is most often round at all ages.

5. Mid Root Cross Section - At this level, the pulp outline of both maxillary incisors is round.

C. Maxillary Canine:

1. Introduction:

The pulp cavity is similar in many respects to that of the maxillary incisors. The major difference reveals the pulp chamber width to be greater labiolingually than mesiodistally, the opposite of the incisors. In fact, the pulp cavity of the maxillary canine has the greatest faciolingual width of any anterior tooth. Since this tooth has the longest root in the mouth, it follows that its root canal is also longest.

2. Labiolingual Section:

a. Pulp chamber - The pulp outline is pointed incisally, and widens to the mid cingulum level, similar to the incisors. The labial margin is normally slightly convex, and there may be a slight bulging lingually in the cingulum area. The pointed incisal becomes rounded with age.

b. Pulp canal - Inasmuch as the root of this tooth is wider labiolingually than that of the incisors, the pulp canal is also wider in this dimension. At the apical third level, the canal becomes greatly constricted, although the foramen size is still larger than that of the incisors.

3. Mesiodistal Section:

a. Pulp chamber - In this section, the pulp cavity differs more from the incisors. From the pointed or slightly rounded incisal limit, the outline increases to its greatest width near the cervical line level. There are no pulp horns, as in the incisors, but the somewhat pointed incisal limit does correspond to the single cusp. Its narrowest dimension is at the incisal.

b. Pulp canal - From the cervical line to about the apical third level, the canal outline is about the same width, but in the apical third it tapers to the single foramen.

4. Cervical Cross Section - Since the root is ovoid and wider labiolingually, so is the pulp outline at this level.

5. Mid Root Cross Section - At this level, the pulp outline is less ovoid, and on occasion is nearly circular.

D. Maxillary First Premolar: 1. Introduction:

The maxillary first premolar has a pulp chamber which is considerably wider faciolingually than mesiodistally. This tooth is the only premolar which exhibits two roots in a majority of cases. Maybe this is why there is a wide variation in its pulp canal morphology. Recent research has revealed that about 70% of these teeth have two root canals with separate foramina, while less than 10% possess a single canal and foramen. It is interesting to note that nearly 5% display three canals, usually when there are three root branches. The remaining specimens exhibit two canals which unite in the apical third to exit a single foramen. One study also pointed out a large number of lateral canals, with about 50% of the cases displaying them. Because it is by far the most common situation, two fully formed canals will be described as representative of this tooth.

2. Buccolingual Section:

a. Pulp chamber - Occlusally, the chamber outline reveals two prominent pulp horns representing the two cusps and appropriately named buccal and lingual. The buccal horn is usually larger, and there is a concavity in outline between the two horns. From the pulp horn area, the chamber maintains a similar width to its floor, which is most often just apical to the cervical line.

b. Pulp canals - From the floor of the pulp chamber, the two root canals taper evenly to their apices. The lingual canal is usually slightly wider, even though the lingual root is most often smaller than the buccal root.

3. Mesiodistal Section:

a. Pulp chamber - The mesiodistal outline is quite similar to that of the maxillary canine, although it is shorter and slightly narrower.

b. Pulp canals - This outline is also similar to that of the canine. Only the buccal canal is visible from the buccal aspect, and likewise only the lingual canal can be seen in a section through the lingual part of the tooth.

4. Cervical Cross Section - The root outline at this level is wider buccolingually and is normally somewhat kidney shaped because of the tooth's mesial concavity, and the pulp outline follows that of the root. The maxillary first premolar exhibits two orifices in most cases, with the lingual orifice being slightly larger in size. Orifice is defined as the opening in the floor of the pulp chamber where a root canal exits.

5. Mid Root Cross Section - At this level, the two root outlines, and their respective canals, are both generally round, with the lingual canal normally slightly larger in diameter.

2-roots Single

Maxillary Second Premolar:

1. Introduction:

The pulp cavity is again wider faciolingually than mesiodistally. The normal maxillary second premolar has but one root and one root canal, although often enough to be of significance the canal branches, usually in the apical third, and there are two foramina.

2. Buccolingual Section:

a. Pulp chamber - The outline is very similar to the first premolar's, and occlusally shows two pulp horns, of which the buccal horn is usually the larger.

b. Pulp canal - From the cervical line, the canal tapers regularly to the apical third, where it becomes constricted. The foramen is normally larger than either of the foramina of the first premolar. Occasionally, the canal branches, but rejoins in the apical third, and occasionally there is an apical third branching with two separate foramina. On rare occasions, there may be two roots, and two root canals, similar to the most common type of first premolar.

3. Mesiodistal Section - It is almost identical to the maxillary canine and first premolar from this aspect.

MESIAL VIEW

MESIAL VIEW

DISTAL VIEW

DISTAL VIEW

BUCCAL VIEW

BUCCAL VIEW

LINGUAL VIEW

4. Cervical Cross Section - Since the single root is more ovoid, and not kidney shaped like the first premolar, the canal is also somewhat oval, but much wider buccolingually than mesiodistally.

5. Mid Root Cross Section - The normal outline reveals one canal which is ovoid, and wider buccolingually than mesiodistally.

Maxillary First Molar:

1. Introduction:

Since the crown of maxillary molars is generally wider buccolingually, it is not surprising that the pulp chamber is also wider in this dimension. Until recently, it was thought that the maxillary first molar seldom deviated from a situation of one root canal in each of its three roots. In the past few years, exacting research has disproved that belief. It has been shown that the MB root exhibits two root canals in about 60% of the specimens studied, and only one in the other 40%.

2. Buccolingual Section - The buccolingual section will be described from the mesial aspect for a cut taken through the MB and lingual roots. The distal aspect, with a section through the DB and lingual roots, is similar, except that only one canal is normally present in the DB root, and the DL pulp horn is much less prominent than the DB horn. The cusp of Carabelli is not normally represented by a pulp horn.

a. Pulp chamber - Mesiobuccal and mesiolingual pulp horns are visible from this aspect and they are nearly equal in height. The chamber outline tapers slightly from the cervical line floor toward the occlusal, so it is normally widest at the cervical, similar to the trapezoidal outline of the mesial crown surface.

b. Pulp canals - In the majority (about 60%) of the specimens, two MB root canals are evident. Most often, the two MB canals will reunite in the apical third and exit via a common foramen. In about 40% of the maxillary first molars, only one MB canal will exist. Also visible in this section is the lingual root canal, which tapers evenly to its foramen. There is normally much greater flare between the buccal and lingual root canals in this view than there is between the MB and DB canals in a mesiodistal section.

3. Mesiodistal Section - Only the mesiodistal section from the buccal aspect will be considered. It should be pointed out that in the lingual view of a mesiodistal section, the only canal evident is the lingual canal, and its outline is generally wider than it is in a buccolingual section.

a. Pulp chamber - From this aspect, the chamber is narrower than in a buccolingual section. Its widest point is at the occlusal pulp horn level, corresponding to the trapezoidal shape of the buccal crown surface. Of the two pulp horns visible, the MB horn is normally a little more prominent than the DB horn. From its widest point at the occlusal, the chamber tapers somewhat to its narrowest width, at the level of the floor, which is apical to the cervical line.

b. Pulp canals - Even if the MB root has two canals, normally only one of them is visible in this view. However, any buccal canals (MB and DB) are more constricted than the lingual canal, and they follow the external root curvatures to their restricted apices. When single, the MB canal is usually wider than the DB canal.

LINGUAL VIEW

4. Cervical Line Cross Section - At the cervical line level, the outline of the pulp cavity is roughly rhomboidal in shape. However, the floor of the chamber is lo-

M cated in the root trunk at a more apical level than the cervical line, and exhibits three root canal orifices. Even when two MB canals are present, there is normally but a single MB orifice. These openings are arranged in a typical triangular shape, known as the molar triangle. The character of this triangle is important to the dentist who practices endodontics. The MB orifice is well to the MB portion of the tooth, and the lingual orifice is also well to the lingual portion. However, the DB orifice is not so far buccally placed as the MB orifice, and, in fact, is located somewhat toward the distal surface. The lingual orifice has the largest diameter, and the DB the smallest.

5. Mid Root Cross Section - The outlines of the three root branches are visible in a mid root cross section. The lingual root and its canal are the largest, and they are both ovoid, and wider mesiodistally. The MB root outline is also ovoid, but it is wider buccolingually, and when two canals are present, they are both circular. If one canal exists, it is normally ovoid and wider buccolingually similar to the root outline. The smallest root outline is that of the DB root, and it is less ovoid and more nearly round, as is its canal outline.

G. Maxillary Second Molar:

The pulp cavity of this tooth is so similar to that of the first molar, that only the following differences will be described:

1. There is not so much flare in the roots from any aspect, and consequently not so much spread in the root canals.

2. Although the two facial roots are closer together, and sometimes even fused, there are still at least two complete root canals at the buccal.

3. There is most often but one root canal in the MB root. However, this tooth's most common exception from normal is two canals in the MB root, similar to the normal anatomy of the first molar.

4. Because the DL cusp is normally reduced in size, the DL pulp horn is also relatively smaller.

5. When the general crown form of this tooth is heart shaped, the outline of the pulp chamber in a cervical line cross section is usually roughly triangular, as compared to the rhomboidal pattern most often seen.

H. Maxillary Third Molar:

No standard pulp anatomy can be described for this tooth because of its wide variation in form, although the most common situation shows a typical maxillary molar configuration with three roots and three root canals. This tooth is normally a poor risk for root canal therapy.

I. Mandibular Incisors: 1. Introduction:

As with the maxillary incisors, the pulp cavities of the two mandibular incisors are so similar that they will be discussed together. Unlike the maxillary incisors, however, their pulpal outline is wider labiolingually. By far the majority (about 70-90%) of mandibular incisor (and canine) specimens exhibit the expected one root and one root canal. In rare instances (1-2%), these teeth reveal two fully formed canals, usually when the root is bifurcated. In the remaining cases, there is one canal which branches into two canals. When this occurs, the two branches may either reunite in the apical third to exit via a common foramen, or may remain separate, exiting through individual foramina. When there are two root canals present in any portion of the root, they are almost always labially and lingually located. The most common situation of a single root and canal will be described and diagrammed.

2. Labiolingual Section:

a. Pulp chamber - From this aspect, the outline of the pulp chamber is similar to that of the maxillary incisors. It is pointed at the incisal, and widens to its largest diameter at about the mid cingulum level.

b. Pulp canal - The canal is widest at the cervix, from where it tapers rather evenly to the single constricted foramen.

3. Mesiodistal Section:

a. Pulp chamber - The chamber is generally narrower in this view than in the labiolingual section, and is much narrower when compared to the maxillary incisors. It is widest near the incisal limit, and then it narrows evenly to the cervical line. Unlike the maxillary incisors, the incisal limit lacks any pulp horns, and is flat or slightly rounded instead.

b. Pulp canal - From the cervical line, the single canal tapers only slightly, but regularly, to the apical foramen.

4. Cervical Cross Section - At this level, the pulp outline is ovoid, and wider labiolingually than mesiodistally, just as is the root outline.

5. Mid Root Cross Section - Even though it is still ovoid, the canal is more constricted, and relatively narrower labiolingually than in the preceding view. Mandibular Canine:

The pulp cavity of the mandibular canine is much like that of the maxillary canine, with the following exceptions:

1. The dimensions of the root canal are generally not quite so great.

2. Both the root and root canal outlines are narrower in the mesiodistal dimension, when compared to the maxillary canine.

3. Occasionally there are two roots, which are labially and lingually located, each with its own pulp canal. This phenomenon is difficult to diagnose, since routine x-rays tend to superimpose the labial and lingual roots and their canals.

4. The proportion of variations in canal numbers which was described for mandibular incisors also applies to mandibular canines, although one study indicated a greater number (as many as 6%) with two complete root canals.

Mandibular First Premolar:

1. Introduction:

The pulp cavity of this tooth is wider faciolingually than mesiodistally, and shows many other similarities to the mandibular canine.

2. Buccolingual Section:

a. Pulp chamber - Normally, there are two pulp horns which correspond in size to the cusps of this tooth. There is a large and pointed buccal horn, and a small, sometimes rounded, lingual horn. However, it is not unusual for the lingual horn to be entirely missing, in which case the outline is like that of the canine. The widest point of the chamber is still near the cervical line, although it is wider toward the occlusal than is the outline of the canine.

b. Pulp canal - From the cervical line, the single canal tapers rather evenly to the apical third, where it is constricted to its apical termination. Occasionally, there is a mid root branching into two canals, which reunite in the apical third. And, a few specimens exhibit a branching in the apical third, with two small foramina. Like the canine, a few teeth also have two roots and two root canals, facially and lingually oriented.

3. Mesiodistal Section - This section is nearly identical to the mandibular canine, although the canine has a longer root, and hence a longer pulp canal.

4. Cervical Cross Section - Both root and root canal in this view are normally ovoid, and wider buccolingually.

5. Mid Root Cross Section - In this section, the canal outline is normally round.

L. Mandibular Second Premolar:

Linguobuccol S«ctton Distal view

Linguobuccol S«ctton Distal view

MESIAL VIEW

MESIAL VIEW

DISTAL VIEW

mandibular second premolar is similar to the first premolar except:

1. The lingual pulp horn is normally larger to correspond to the larger lingual cusp(s). Some Y type specimens exhibit two lingual pulp horns.

2. The root and root canal cross sections are more often ovoid, wider buccolingually, than round.

3. The pulp chamber is relatively wider buccolingually than mesiodistally, when compared to the first premolar.

4. In the buccolingual section, the separation of the pulp chamber and canal is normally distinguishable, as contrasted to the more regular taper in the first premolar.

5. The second premolar root, and thus its root canal, are slightly longer. Mandibular First Molar:

1. Introduction:

Although mandibular first molars normally possess two roots, they exhibit three root canals about 70% of the time. Two of these canals are found in the mesial root (MB and ML), while the distal root contains only one canal. In a majority of the remaining 30% of the cases, there are four canals with two per root. In some cases, however, there is only one canal in each root, or a total of two canals. The most common situation of three canals will be discussed and diagrammed. The buccolingual dimension of the pulp chamber is less than the mesiodistal dimension, corresponding to the crown dimensions.

Buccolingual Section:

a. Mesial aspect (chamber and canals) - There are two pulp horns (MB and ML) of nearly equal size and pointedness, corresponding to the two mesial cusps. The chamber is widest near the pulp horn level, but constricts only slightly to the chamber floor, which is apical to the cervical line. The mesial root is larger than the distal, and it is the only one visible in this section. The mesial root normally has two root canals, named MB and ML canals. They constrict only a little from the chamber floor to their separate foramina. In some cases, there is only one canal, which is quite wide buccolingually. Also, on occasion, the two canals unite in the apical third, and share a common foramen.

b. Distal aspect (chamber and canal) - The outline of the chamber is generally smaller but otherwise looks like it did from the mesial aspect, except that a slight pulp horn, corresponding to the distal cusp, can sometimes be seen. The DB and DL pulp horns are about the same size.

There is normally a single canal, which is quite wide buccolingually, and tapers evenly to the apex. It is much larger than either of the mesial canals. As previously mentioned, it is not uncommon to find two canals, similar to those of the mesial root.

DISTAL VIEW

3. Mesiodistal Section (Buccal Aspect):

a. Pulp chamber - The chamber is widest at the pulp horn level, and constricts slightly to its floor, which is apical to the cervical line. Normally, only the two buccal pulp horns can be seen, but occasionally a small distal horn is also visible in the newly erupted specimen. The MB pulp horn is noticeably larger than the DB horn.

b. Pulp canals - Only two canals are visible from either the buccal or lingual aspect. The distal canal is visible from both aspects. However, of the two mesial canals, only the MB canal is visible from the buccal aspect, and the ML canal is only visible from the lingual aspect. There is also more spread to the canals in this section, when compared to a mesial view.

4. Cervical Line Cross Section - The outline of a cervical cross section follows the crown's external contour. There is usually evidence of all five cusps in the form of rounded humps at the five points of the roughly pentagonal outline. The floor of the chamber, apical to the cervical line, exhibits three orifices, two mesially placed, and one distally located. The distal is the largest, and it is quite wide buccolingually, while the two mesial orifices are usually circular.

M D 5. Mid Root Cross Section - There are normally two roots, both of which are wider buccolingually. The mesial root, which is somewhat kidney shaped, is the largest, and contains the two more or less circular root canal outlines, of which the MB is slightly larger in diameter. The smaller distal root contains one large ovoid canal, which is wider buccolingually, like the root shape. In some cases, the distal root outline, and even the root canal, may exhibit a kidney shape.

N. Mandibular Second Molar:

The pulp cavity of the second molar is similar to that of the first molar, with the following exceptions:

1. There are still normally two root canals in the mesial root, but more often than in the first molar, there is only one. There is likewise an even smaller chance of two root canals in the distal root.

2. The pulp chamber is generally not as large, and the two mesial orifices are located closer together.

3. In a buccolingual section, the two mesial canals are not as divergent.

4. There is almost never a distal pulp horn. O. Mandibular Third Molar:

Like the maxillary third molar, no standard pulp outline can be described, due to the wide variation in form. However, most common is the typical mandibular molar configuration of two roots and three root canals. Like the maxillary third molar, this tooth is normally a poor risk for root canal therapy.

Enamel

Chamber Roof Chamber Floor Secondary Dentin

Dentin

Lateral Canal

Enamel

Dentin

Lateral Canal

Supplementary Canal Apical Foramina

Secondary Dentin

Odontoblastic Layer

Capillary Fibroblasts and Fibers Nerve Fibers

Clutch Free Play DefinitionPosterior Anterior Teeth Chart
Posterior Tooth

Mid-Root Cross Section

Insisivo Central Superior Faces

Labiolingual Section Mesial View

Mesiodistal Section Lingual View

Distomesial Section Buccal View

Mesiodistal Section Lingual View

Linguobuccal Section Distal View

Cervical Section

Single 2-roots

Laminated Mid-Root Section

Equine Dental Pulp Anatomy
Cervical Section Mid-Root Section

Cervical Section

Labiolingual Section Mesial View

Mesiodistai Section Lingual View

Cervical Section

Mid-Root Section

Labiolingual Section Mesial View

Mesiodistal Section Lingual View

Labiolingual Section Mesial View

Mesiodistal Section Lingual View

Mid-Root Section

Pulp Anatomy

Distomesial Section Buccal View

Insisors Side View

Distomesial Section Buccal View

Cervical Section

Cervical Section

Mesiodistal Section Lingual View

Buccolingual Section Mesial View

Mid-Root Section

Linguobuccal Section Distal View

Mesiobuccal Orifice

Distobuccal Orifice

Lingual Orifice

Distobuccal Orifice

Lingual Orifice

Molar Triangle

Maxillary First Molar ( Floor of Pulp Chamber)

Molar Triangle

Maxillary First Molar ( Floor of Pulp Chamber)

Deciduous Root Orifice
(Floorof Pulp Chamber)

UNIT #10

I. ReadinçfAssignment:

Unit # 10 (The Deciduous Dentition)

II. Specific Objectives:

At the completion of this unit, the student will be able to:

A. Demonstrate a knowledge of the general differences between the permanent and deciduous teeth, by describing them, or selecting the correct response from a list, when given one or more differences, or any appropriate implications of these differences.

B. Demonstrate a knowledge of the morphology of each surface of the crown and root of all deciduous teeth by:

1. describing,

2. selecting the correct information from a list,

3. or interpreting a diagram to identify or name any of the following features:

a. Contours of any surface, or margin of any surface.

b. Structural entities such as grooves, pits, ridges, cusps, fossae, etc.

c. Relative dimensions and shape.

d. Root numbers, location, and contours.

e. Any other surface feature.

Furthermore, the student will be able to make comparisons of any of these features between any of the deciduous teeth.

C. Make comparisons between specific deciduous teeth and their permanent counterparts, where appropriate, by describing the differences, or selecting the correct information from a list.

D. Determine from a diagram or description which deciduous tooth is being described, or illustrated.

E. Provide the correct universal number or Palmer notation for a given diagram or description of any deciduous tooth.

The student is also responsible for any material which was to have been mastered in previous units.

UNIT # 10 THE DECIDUOUS DENTITION

I. Introduction:

A. Until this point in the text, the deciduous dentition has assumed the status of a second class citizen. Even though the time spent studying the deciduous teeth will be less than that devoted to the permanent teeth, they are nonetheless important.

B. Until a generation or two ago, most parents were guilty of disregarding the value of the deciduous teeth of their children. But even worse, many dentists likewise took this view. As a result, the primary teeth were considered as simply a temporary phase in the more important process of acquiring a permanent dentition. Rarely did these teeth receive adequate attention, and the customary treatment was extraction of any deciduous tooth which became so diseased it caused dysfunction or pain to the child. One of the most common consequences of this philosophy of treatment (or lack of it) was a loss of space with the potential for crowding and malocclusion in the permanent dentition. Fortunately, attitudes have changed and the dental profession, along with the general public, now have a more realistic appreciation of the value of the primary teeth.

C. As previously indicated, there are a total of twenty deciduous teeth, ten per arch, and five per quadrant. In each quadrant, there are two deciduous incisors and one canine, just as in the anterior segment of the permanent dentition. However, unlike the permanent posterior teeth, there are no premolars, and only two molars per quadrant. Deciduous teeth exhibit a functional role similar to their permanent counterparts.

D. A brief review of those portions of the introductory unit which concern the deciduous dentition would be of value to the student. It should also be noted that the development and life cycle of the deciduous teeth will be discussed in the succeeding unit.

II. Comparisons Between Permanent and Deciduous Teeth:

A. External Considerations:

1. The deciduous teeth are generally smaller than their permanent counterparts. This size disparity exists for crown and root portions of both anterior and posterior teeth.

2. The crown portion of the deciduous teeth is quite short inciso (occluso) gingivally, relative to its total crown-root length, when contrasted to the same dimensions of permanent teeth.

3. The crowns of deciduous teeth are wider mesiodistally, relative to their inciso (occluso) gingival height, when compared to the same dimensions of permanent teeth.

4. The crowns of deciduous teeth are more constricted faciolingually at the cervical line than are those of permanent teeth.

5. Because of a greater occlusal convergence of the buccal and lingual surfaces, the occlusal tables of deciduous molars are relatively more constricted faciolingually than are the crowns of permanent molars.

6. There is a cervical ridge on both labial and lingual surfaces of deciduous anterior teeth, as well as on the buccal surface of deciduous posterior teeth. This ridge is normally much more prominent than any analogous structure found on permanent molars.

7. In comparison to the crown height occlusocervically, the roots of deciduous molars are relatively longer than those of permanent molars. They are, how ever, less substantial in their other dimensions, which in summary makes them longer and thinner.

8. The roots of deciduous molars reveal much more flare, or spreading, than do roots of the permanent molars. This flare creates additional space for the permanent premolar crown to develop. Their greater spread, coupled with the more slender shape and lack of a root trunk, make deciduous molar roots easier to fracture during extraction procedures.

9. The roots of deciduous molars branch almost directly from the base of the crown, so that there is no easily identifiable root trunk, as there is in the permanent molars. This feature also creates more space for the developing permanent premolar crown.

10. The crowns of deciduous teeth are lighter in color. This is because they are more opaque and thus exhibit a whitish-white or even bluish-white cast, compared to the yellowish and grayish-white shades of permanent tooth crowns.

B. Internal Considerations:

1. The enamel in the crowns of deciduous teeth is relatively thin, when compared to permanent teeth.

2. The dentin of primary teeth is also relatively thin, in comparison to permanent teeth.

3. The pulp cavity is relatively larger in the deciduous teeth. The mesial pulp horns of deciduous molars are especially large.

III. Description of Individual Deciduous Teeth:

Instead of describing the deciduous teeth in as much detail as the permanent teeth, greater use of comparisons will be made. A. Maxillary Central Incisor:

1. General considerations - The deciduous maxillary central incisor is similar in many respects to its permanent successor. It has the same arch position, function, and relative shape. In addition to the previously elicited general differences, there are two major specific contrasts to the permanent maxillary central. First, there are no mamelons in newly erupted teeth. Second, this is the only anterior tooth of either dentition, in which the mesiodistal crown width is normally greater than the incisocervical crown height.

2. Labial aspect - The mesial and distal outlines are more convex than in the permanent central. The generally convex labial surface is smooth, and rarely exhibits developmental depressions or imbrication lines. The incisal outline is relatively flat, lacks mamelons, and usually slopes toward the distal after wear. The distoincisal angle is slightly more rounded than the mesioincisal angle. The cervical line curves evenly toward the root.

3. Lingual aspect - The cingulum is more prominent, and extends farther incisally than on the permanent tooth. The marginal ridges are also more prominent, and the fossa is deeper.

4. Mesial aspect - The mesial surface is similar to that of the permanent tooth, except that in the deciduous tooth it is relatively wider labiolingually, and the cervical line exhibits less curvature incisally.

5. Distal aspect - The distal is similar to the mesial aspect, except that the cervical line curvature is less.

6. Incisal aspect - The almost straight incisal edge divides the crown into roughly equal labial and lingual portions. The most noticeable feature, however, is the crown's relatively great mesiodistal width.

7. Root - The single root is generally round and tapers evenly to the apex. It is longer, relative to crown length, than in the permanent central.

B. Maxillary Lateral Incisor:

This tooth will not be described in detail, since it is so similar to the central incisor;

only the following differences will be pointed out:

1. The deciduous lateral incisor is smaller than the central in all dimensions. However, unlike the central, the crown of the lateral incisor is wider incisocervically than mesiodistally.

2. Both incisal angles display greater rounding, with the distoincisal angle more so than the mesioincisal.

3. The marginal ridges on the lingual surface are more prominent, with a resultant deeper lingual fossa.

4. From the incisal aspect, the much narrower mesiodistal dimension is reflected in an outline which is more rhomboidal and more convex.

5. The root outlines are similar, but the lateral's root is relatively longer, and its apex is not so rounded.

C. Maxillary Canine:

1. General considerations - The deciduous maxillary canine exhibits a crown which is also quite wide mesiodistally. However, this dimension is slightly less than the incisocervical measurement.

2. Labial aspect - Like the deciduous maxillary incisors, the mesial and distal outlines bulge convexly to the cervical line. The height of contour of these margins is found at the level of the contact area. Interestingly, the mesial and distal contact areas are located at the same level incisocervically, rather than at different levels, as in the permanent canine. This feature is also true for the deciduous mandibular canine. Before incisal wear, the cusp is relatively more prominent than that of the permanent tooth. The mesioincisal slope is normally longer than the distoincisal slope, especially after attrition. The cervical line exhibits an even curvature apically. Normally, no developmental depressions or imbrication lines are present.

3. Lingual aspect - The cingulum is quite prominent, as are the lingual ridge and marginal ridges. Normally, ML and DL fossae are present. Unlike the permanent canine, there is occasionally a tubercle located where the cingulum merges with the lingual ridge near the center of the lingual surface.

4. Mesial aspect - This surface is similar to the primary maxillary incisors, except that labiolingually the tooth is thicker, and the cervical line depth is less.

5. Distal aspect - The distal surface is similar to the mesial, except that the cervical line shows less curvature.

6. Incisal aspect - From this aspect, the outline is rhomboidal, but has more rounding than the permanent canine exhibits. The cusp tip is offset to the distal, and thus the mesial cusp ridge is longer.

7. Root - From all aspects, the root is similar to the deciduous maxillary incisor roots, except that it is longer.

D. Maxillary First Molar:

1. General considerations - This tooth's crown does not resemble any other primary or permanent molar crown, but does exhibit some similarities to the crowns of permanent premolars. However, the root form is typical of maxillary molars. Like all permanent maxillary posterior teeth, the crown shows its greatest dimension buccolingually. The occlusal table reveals only two prominent cusps, the MB and ML cusps. The two distal cusps, and especially the DL cusp, are greatly diminished. This feature creates the most conspicuous comparison to a permanent maxillary premolar crown.

2. Buccal aspect - The mesiodistal diameter is much greater than the crown height. The mesial and distal outlines are convex, and constrict greatly toward the cervix from the heights of contour, which are located at the contact areas near the junction of the occlusal and middle thirds. The occlusal outline is comparatively straight, since the two buccal cusps are nowhere near as prominent or sharp as in the permanent maxillary molars. An essential difference from the permanent tooth is found in the contour of the cervical line, since its depth of curvature is much greater toward the mesial than the distal, thus giving the crown the appearance of being offset toward the mesial. The entire surface is relatively smooth and lacks grooves or depressions. Occlusally, the buccal surface is mostly flat, but in the gingival third the cervical ridge is prominent, especially the mesial portion. The surface has a crest of curvature in the cervical third.

3. Lingual aspect - The lingual outline is much like that of the buccal view, but with a lessened mesiodistal dimension. The account of the mesial and distal margins parallels their description for the buccal surface. Even though the ML cusp is not very tall, it is quite bulky and dominates the occlusal outline. The DL cusp is so diminutive that the DB cusp is also partially visible from this aspect. Unlike the buccal surface, the cervical line is evenly, and slightly, curved toward the apex. The lingual surface is generally convex and smooth without grooves or depressions. The height of contour is more cervically located, at about the middle and cervical third junction, as compared to its middle third location in permanent maxillary posterior teeth.

4. Mesial aspect - The disparity between the faciolingual widths of this surface at its cervical and occlusal margins is much more than in the permanent maxillary molars. Cervically, the dimension is considerably wider, due to the prominent cervical ridge on the buccal, as well as the greater taper of the buccal and lingual outlines toward the occlusal. The buccal outline is dominated by the cervical ridge and crest of curvature in the cervical third. The remainder of the buccal outline is usually straight, or even slightly concave. The lingual outline is generally convex, but with a more cervically located crest of curvature than is present on the permanent molars. The two mesial cusps and the mesial marginal ridge make up the occlusal outline. From this aspect, the ML cusp is more generous in height and size than is the MB cusp. Because of the diminished buccolingual dimension at the occlusal, the marginal ridge is relatively short. The cervical line is slightly curved toward the occlusal.

5. Distal aspect - The distal surface itself is considerably smaller than the mesial surface. Since the buccal surface tapers toward the distal, much of it is visible from this aspect. The DB cusp is more prominent than the minute DL cusp, and the distal marginal ridge is less pronounced than is the mesial. The mesial cusps actually provide the occlusal outline from this aspect. The cervical ridge is not so prominent in the buccal outline as it is from the mesial aspect. The cervical line is straight to slightly curved occlusally.

6. Occlusal aspect - The general shape of this tooth from the occlusal aspect is an unusual five sided figure. The crown dimensions are less buccolingually toward the distal, and less mesiodistally toward the lingual.

a. Cusps - Like most permanent maxillary molars, there are four cusps, but in reality the two distal cusps are so meager that there is a closer similarity to a premolar occlusal table. The ML cusp is the bulkiest, and also the longest, while the DL cusp is the smallest, and on occasion, is entirely absent. Of the two remaining cusps, the MB is of greater proportions than the DB. In fact, the lingual cusp ridge of the MB cusp is the most prominent single elevation within the occlusal table.

b. Transverse ridge - A very prominent transverse ridge dominates the occlusal table of this tooth, and like the permanent maxillary molars, consists of the lingual cusp ridge of the MB cusp and the buccal cusp ridge of the ML cusp.

c. Oblique ridge - The majority of specimens exhibit an oblique ridge, extending from the ML cusp to the DB cusp, similar to, but not as prominent as the analogous structure of permanent molars.

d. Fossae - This tooth contains three fossae: a well defined central fossa, plus mesial and distal triangular fossae.

e. Pits and grooves - There are mesial and distal pits, which are located in the depth of their respective triangular fossae. There is also a central pit, with a central groove connecting it with the mesial and distal pits. The buccal groove, which also originates in the central pit, extends buccally, separating the MB and DB cusps on the occlusal surface only. The distal triangular fossa also contains a disto-occlusal groove, which extends obliquely on the occlusal table, and parallels the oblique ridge just distal to it. This groove rarely crosses onto the lingual surface like the distolingual groove of the permanent maxillary molars does.

7. Roots - As previously pointed out, deciduous molars possess no root trunk, and the root branches are more slender, and reveal greater flare. Otherwise, the root structure of the first molar exhibits three root branches which are similar in name, location, and general contours, to those of the permanent maxillary molars. The lingual root is the largest and longest, followed in size by the MB root, and the DB root, respectively.

E. Maxillary Second Molar:

There is really no need to describe this tooth in detail, since, despite the general differences between deciduous and permanent molars, it closely resembles the permanent maxillary first molar. So, other than those general differences, its contours, occlusal pattern, and roots are modeled after the permanent tooth. In fact, this tooth even exhibits at least a trace of the cusp of Carabelli trait in most specimens.

F. Mandibular Central Incisor:

1. General considerations - This tooth bears a much closer resemblance to the deciduous mandibular lateral incisor than it does to its permanent counterpart, or to any deciduous maxillary incisor. The mandibular central incisor crown is symmetrical, when viewed from the labial, lingual, or incisal, just like its permanent successor. In relation to its incisogingival height, the crown is relatively wider mesiodistally than in permanent incisors. However, the mesiodistal dimension is not greater than the incisocervical dimension, as it is in the deciduous maxillary central incisor.

2. Labial aspect - The mesial and distal outlines are evenly convex from the sharp mesioincisal and distoincisal angles to the cervical line. The convexity is less than that exhibited by the deciduous maxillary incisors. The height of contour of these margins is at the contact area in the incisal third. The incisal margin is straight, and devoid of mamelons. The labial surface itself is smooth, lacking developmental depressions, and generally is flatter than the labial surface of permanent incisors.

3. Lingual aspect - The cingulum is well defined, but the marginal ridges are not so well developed as in the maxillary incisors, thus outlining a lingual fossa which is quite shallow. All margins are comparable to those of the facial surface.

4. Mesial aspect - From this view of the crown, the most outstanding feature is the relatively greater labiolingual width, when compared to the permanent incisors. The incisal edge is located over the root center, and the cervical line contour is evenly curved toward the incisal.

5. Distal aspect - The distal surface is similar to the mesial, except that the cervical line exhibits less depth of curvature.

6. Incisal aspect - From this view, the incisal edge is straight, and it divides the labial and lingual portions of the crown into nearly equal halves. The mesio-distal and labiolingual dimensions are nearly equal, whereas in the maxillary central incisor, the crown was noticeably wider mesiodistally. As in the permanent tooth, mesial and distal portions of the crown are symmetrical from this aspect.

7. Root - The root is single, relatively long, and slender. The labial and lingual surfaces are convex, while the mesial and distal surfaces are somewhat flattened.

G. Mandibular Lateral Incisor:

This tooth is similar in form to the deciduous mandibular central incisor, with the following exceptions:

1. The crown is slightly longer incisogingivally and wider mesiodistally.

2. From the labial or lingual aspect, the incisal outline slopes slightly toward the distal, with a resultant distoincisal angle which is more rounded, as is the distal margin of the crown. The distal margin is also a little shorter.

3. The cingulum and marginal ridges are usually a little larger, and the lingual fossa is a little deeper.

4. From the incisal, the crown is not quite symmetrical like the central, since the cingulum bulges toward the distal, as it does in the permanent mandibular lateral.

5. The root may present a distal curvature in its apical third, and it normally has at least a distal longitudinal groove.

H. Mandibular Canine:

In general form, this tooth resembles the deciduous maxillary canine, but its relative dimensions are somewhat different. The most notable contrasts with the maxillary canine reveal that:

1. The mandibular canine is a much narrower tooth labiolingually, and this is the crown dimension in which the two teeth differ most.

2. The mesiodistal width of the mandibular canine is also considerably less than that of the maxillary canine. The incisocervical dimension of the two deciduous canines is the same. Therefore, the crown of the mandibular canine has an incisocervical height which is noticeably greater than its mesiodistal width, while these two dimensions of the maxillary canine are much closer to being equal.

3. The distoincisal slope is longer on the mandibular canine, whereas on the maxillary canine it is the mesioincisal slope which is longer.

4. The cingulum, marginal ridges, and cervical ridges are less pronounced on the crown of the mandibular canine.

5. The mandibular canine root is shorter. I. Mandibular First Molar:

1. General considerations - This tooth has a crown unlike any other primary or permanent tooth. However, it does have two roots which are positioned similarly to those of the other primary and permanent mandibular molars. Its crown is wider mesiodistally than buccolingually, as is characteristic of all mandibular molars of both dentitions.

2. Buccal aspect - The mesial outline is uniquely straight occlusogingivally for most of its length, but the distal outline is convex, and overhangs the cervical line. The occlusal outline reveals two buccal cusps, of which the MB cusp is much larger. From this view, the cusp outlines are more prominent than those of the deciduous maxillary first molar. There is a depression separating the two buccal cusp outlines, but rarely does the buccal groove extend onto the buccal surface in the depression. The cervical line is deeper, and offset toward the mesial, just like it is on the deciduous maxillary first molar. The cervical ridge is also quite prominent, especially in the mesial portion.

3. Lingual aspect - The lingual surface is shorter occlusocervically than the buccal surface. It is also smooth and convex, and lacks any depressions or ridges. The mesial and distal margins are similar to those of the buccal aspect, but the cervical outline is rather straight, unlike the buccal aspect where it is irregular and has a deep offset to the mesial. The occlusal outline shows two lingual cusps, of which the ML cusp is larger and sharper. Portions of the two buccal cusps can also be seen.

4. Mesial aspect - The most striking feature, from this view, is the cervical ridge representing the crest of curvature in the gingival third of the buccal outline. Both mesial cusps are visible. The contact area is located near

Was this article helpful?

0 0

Responses

  • nicole
    What contour follows the pulp cavity?
    2 years ago
  • eija
    What are the pulp cavity tissue?
    8 months ago

Post a comment