Teeth Internal Anatomy

Dr. Muna Q. MarashdehMSc. Endodontics

LECTURE OUTLINE• METHODS OF DETERMINING PULP ANATOMY• Textbook Knowledge• Radiographic Evidence• Exploration• GENERAL CONSIDERATIONS• Root and Canal Anatomy• Identification of Canals and Roots• ALTERATIONS IN INTERNAL ANATOMY• Age• Irritants• Calcifications• Internal Resorption

• COMPONENTS OF THE PULP SYSTEM• Pulp Horns• Pulp Chamber• Root Canals• Accessory Canals• Apical Region• VARIATIONS OF ROOT AND PULP ANATOMY• Dens Invaginatus (Dens in Dente)• Dens Evaginatus• High Pulp Horns• Lingual Groove• Dilaceration

METHODS OF DETERMINING PULP ANATOMY

• Textbook Knowledge• Radiographic Evidence• Exploration

Textbook Knowledge

• Gaining knowledge of anatomy from textbooks is the most important and most useful method of learning.

• Common and frequent variations must be memorized for each tooth. This means having a working knowledge of the number of roots, number of canals per root and their location, longitudinal and cross-sectional shapes, most frequent curvatures (particularly in the faciolingual plane), and root outlines in all dimensions

Radiographic Evidence

• Certainly, radiographs are useful, but they are somewhat overrated for determining pulp anatomy, particularly conventional

periapical films.• The standard parallel facial projection gives just two dimensions; a common error is to examine only this view, overlooking the important third dimension. • In addition, radiographs tend to make the canals look relatively uniform in shape and tapered. In fact, the aberrations often found are generally not visible

• Standard projections indicate general anatomic features. Special

radiographic techniques disclose missed canals and determine curvatures.

Exploration

• Additional determinations of pulp anatomy are made during access preparation and when searching for canals.

• These methods also have limitations because canals often are neither readily apparent nor easily discovered with instruments.

GENERAL CONSIDERATIONS

• Root and Canal Anatomy• Identification of Canals and Roots

GENERAL CONSIDERATIONS

• A basic tenet in pulp root anatomy is the shape of the pulp system reflects the surface outline of the crown and root.

• Because the pulp tends to form the surrounding dentin uniformly on opposite walls, the pulp is generally a miniature version of the tooth and conforms to the tooth surface

Root and Canal Anatomy

• Although root shape in cross-section is variable, there are seven general configurations: round, oval, long oval, bowling pin, kidney bean, ribbon, and

hourglass. • Shape and location of canals are governed by root shape (in cross-section).

• Different shapes may appear at any level in a single root• It is important to note that a canal is seldom round at any level. To assume that it is may result in improper canal preparation

• Root canals take various pathways to the apex. • The pulp canal system is complex; canals may branch,

divide, and rejoin.• Canal systems have been categorized into four basic

types (Weine classification).• Vertucci et al utilized precise techniques and found a

complex canal system and identified eight pulp space configurations.

• Both gender and ethnic origin should be considered during the preoperative evaluation stage.

• Weine root canal classification

Diagrammatic representation of Vertucci’s canal configurations

A. One canal at apex

Type I Type II Type III

B. Two canals at apex

Type IV Type V Type VI Type VII

C. Three canals at apex

Type VIII

Identification of Canals and Roots

• Differentiation and identification of canal orifices are facilitated by following certain procedures and by identifying anatomic features

• Obviously, to clean, shape, and obturate a canal, it must first be located.

• In roots that may contain two canals, a basic rule is to assume that the root contains two canals until proved otherwise.

• Rather than memorize roots that often contain two canals, it is easier to remember those few that are unlikely to have two canals.

• Maxillary teeth contain some roots that rarely have two canals: anterior roots, premolars with two or three roots, and distobuccal and lingual roots of molars.

• All other maxillary roots and all mandibular roots require a careful search for two (or possibly more) canals.

The Laws of Orifices Location

• LAWS OF CANAL ORIFICES• 1. Symmetry 1: Canal orifices are equidistant from a line drawn in a mesiodistal direction through the pulp-chamber floor (exception: maxillarymolars).• 2. Symmetry 2: Canal orifices lie on a line perpendicular to a line drawn in a mesiodistal direction across the center of the floor of the pulp chamber (exception: maxillary molars).

3.Orifices’ location 1: Canal orifices are located at the junction of the walls and the floor.4. Orifices’ location 2: Canal orifices are located at the line angles in the floor-wall junction.5. Orifices’ location 3: Canal orifices are located at the terminus of the root development fusion lines.6. Color change: Pulp chamber floor color is always darker than the walls

ALTERATIONS IN INTERNAL ANATOMY

• Age• Irritants• Calcifications• Internal Resorption

ALTERATIONS IN INTERNAL ANATOMY

• Initial pulp shape reflects root shape. However, because pulp and dentin react to their environment, changes in shape occur with increasing tooth age and in response to irritation

Age

• Although dentin formation tends to occur with age on all surfaces, it occurs predominately in certain areas.

• For example, in molars, the roof and floor of the chamber show more dentin formation, eventually making the chamber almost disclike in configuration.

• Treatment implications (difficulty in locating chamber and canals) are obvious.

Irritants

• Anything that exposes dentin to the oral cavity can potentially stimulate increased dentin formation at the base of tubules in the underlying pulp. Causes of such dentin exposure include caries, periodontal disease, abrasion, erosion, attrition, cavity preparations, root planing, and cusp fractures.

• Vital pulp therapy, such as pulpotomy, pulp capping, or placement of irritating materials in a deep cavity, may cause an increase in dentin formation, occlusion, or other unusual configurations in the chamber or

canals.• These tertiary (irregular secondary) dentin formations tend to occur directly under the involved tubules.

Calcifications

• Calcifications take two basic forms within the pulp: pulp stones (denticles) and diffuse calcifications.

• Although pulp stones are usually found in the chamber and diffuse calcifications within the radicular pulp, the reverse may also occur.

• These calcifications may form either normally or in response to irritation. Pulp stones are often seen on radiographs; diffuse calcifications are visible only histologically.

• Pulp stones in the chamber may reach considerable size and can markedly alter the internal chamber anatomy

• Although they do not totally block a canal orifice, pulp stones often make the process of locating an orifice challenging.

• These large pulp stones may be attached or free and are often removed during access preparation.• Although pulp stones are not common in canals, if present, they are usually attached or embedded in the canal wall in the apical region. Rarely do they form a barrier to instrument passage.

Internal Resorption

• Such resorptions are uncommon. • They are a response to irritation that is sufficient to cause

inflammation.• Most resorptions are small and are not detectable on radiographs

or during canal preparation.• When visible radiographically, they are usually extensive and often perforate.• Internal resorptions usually create operative difficulties

COMPONENTS OF THE PULP SYSTEM

Pulp Horn

Accessory Canal

Apical RegionApical

Delta

Pulp Chamber

Root Canal

Root Canal System

COMPONENTS OF THE PULP SYSTEM

• The pulp cavity is divided into a coronal (the pulp chamber) and a radicular portion (the root canal).

• Other features include pulp horns, canal orifices, accessory (lateral) canals, and the apical foramen.

• The internal anatomy of these pulp components is altered by secondary dentin or cementum formation

Pulp Horns

• Pulp horns represent what the dentist does not want to locate during restorative procedures but does want to locate during access preparation.

• Although they may vary in height and location, a single pulp horn tends to be associated with each cusp in a posterior tooth, and mesial and distal horns tend to be in incisors.• Generally, the occlusal extent of the pulp horns corresponds to the height of contour in a younger tooth but because of continued dentin formation lies closer to the cervical margin in an older tooth.

Pulp Chamber

• The pulp chamber occupies the center of the crown and trunk of the root.

• In mature molars, the roof of the chamber is approximately at the level of the cemento-enamel junction

Root Canals

• Root canals extend the length of the root, beginning as a funneled orifice and exiting as the apical foramen.

• Most canals are curved, often in a faciolingual direction.

• Therefore a curved canal is often undetectable on facial projection radiographs.• The operator should always assume that a canal is curved.

• Canal shape varies with root shape and size, degree of curvature, and the age and condition of the tooth

• Irregularities and aberrations are common in posterior teeth.

• The chamber tends to occupy the center of the crown; a canal occupies the center of the root. When there are two canals in a root, each will often occupy the center of its own root “bulge.”

Accessory Canals

• Accessory (or lateral) canals are lateral branches of the main canal that form a communication between the pulp and periodontium.

• They contain connective tissue and vessels and may be located at any level from furcation to apex but tend to be more common in the apical third and in posterior teeth.

• They do not supply collateral circulation and therefore contribute little to pulp function and probably represent an anomaly that occurred during root formation.• These canals do form an exit for irritants from the pulp space to the lateral periodontium.• They probably cannot be débrided during cleaning and shaping but are occasionally filled with obturating materials during canal filling.• Débriding and obturating lateral canals are not important for success of root canal treatment

Apical Region

• Development• The apex is the root terminus. It is relatively straight in

the young mature tooth but tends to curve more distally with time.

• This curvature results from continued apical-distal apposition of cementum in response to continued mesial-occlusal eruption.

• Alterations in the apical region may also result from resorption and irregular cementum apposition. Thus apical anatomy tends to be non-uniform and unpredictable.

• Apical Foramen• The apical foramen varies in size and configuration with maturity. • Before maturation, the apical foramen is open. • With time and deposition of dentin and cementum, it becomes

smaller and funneled. • The foramen usually does not exit at the true (anatomic) root apex

but is offset approximately 0.5 mm and seldom more than 1.0 mm from the true apex.

• For this reason, root canal preparation and obturation end short of the anatomic root apex as seen in the radiograph Usually, the apical foramen is not visible radiographically.

• Variations in Anatomy• The only consistent aspect of the apex region

is its inconsistency.• The canal may take twists and turns, divide

into several canals to form a delta with ramifications on the apical root surface, or exhibit irregularities in the canal

• Apical Constriction• The presence of an apical constriction is unpredictable.

Frequently there is no apical constriction. It has been proposed that the cementodentinal junction forms the apical constriction; however, this concept is incorrect.

• In fact, the junction is difficult to determine clinically with accuracy, and the intracanal extent of cementum is variable.

• If an apical constriction is present, it is not visible on a radiograph and usually is not detectable with tactile sense using a file, even by the most skilled practitioner

VARIATIONS OF ROOT AND PULP ANATOMY

• Dens Invaginatus (Dens in Dente)• Dens Evaginatus• High Pulp Horns• Lingual Groove• Dilaceration

VARIATIONS OF ROOT AND PULP ANATOMY

• Occasionally, teeth vary significantly in root or, more likely, in pulp anatomy. Such variations and abnormalities are most common in the maxillary lateral incisors, maxillary and mandibular premolars, and maxillary molars. Unusual root morphology tends to be bilateral

Dens Invaginatus (Dens in Dente)

• Dens invaginatus, which is most common in maxillary lateral incisors, results from an infolding of the enamel organ during proliferation and is an error in morphodifferentiation .

• It often results in an early pulp-oral cavity communication requiring root canal treatment.

• Dens invaginatus shows varying degrees of severity and complexity.

• The more severe cases should be referred to a specialist because special treatment, such as surgery, is frequently required.

• The lingual pit on maxillary anterior teeth represents a minor form of dens invaginatus

Dens Evaginatus

• Dens evaginatus is most common in mandibular premolars • Clinically, dens evaginatus initially appears as a small tubercle “bulge”

on the occlusal surface, but it may not be obvious radiographically. • These tubercles often contain an extension of the pulp. • When these fragile tubercles fracture off, the pulp is exposed and will

become necrotic, requiring apexification.One method to prevent pulp exposure , before the tuberclefractures, is to remove the tubercle with a bur and then cap, followed by a good sealing restoration

High Pulp Horns

• Occasionally, a pulp horn extends far into a cusp region, resulting in premature exposure by caries or accidental exposure during cavity preparation.

• These high pulp horns are often not visible on radiographs. This is most common in the mesio-buccal of first molars.

Lingual Groove

• Usually found in maxillary lateral incisors, a lingual groove appears as a surface infolding of dentin oriented from the cervical toward the apical direction

• Frequently, this results in a deep narrow periodontal defect that occasionally communicates with the pulp, causing an endodontic/periodontal problem

• Treatment is difficult andunpredictable, so prognosis is poor. Usually these teeth require extraction

Dilaceration

• By definition, dilaceration is a severe or complex root curvature .

• During root formation, structures, such as the cortical bone of the maxillary sinus or the mandibular canal or nasal fossa, may deflect the epithelial diaphragm, resulting in a severe curvature.

• Many of these curvatures are found in a faciolingual plane and are not obvious on standard radiographic projections

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