Anatomy Teeth are composed primarily of dentum, With an enamel cap over the coronal portion and a thin layer of cementum over the root surface The enamel cap characteristically appears more radiopaque than the other tissues because it is the most dense naturally occurring substance in the body

Dentin is smooth and homogeneous on radiographs because of its uniform morphology. The enamelodentinal junction, between enamel and dentin, appears as a distinct interface that separates these two structures.

The thin layer of cementum on the root surface has a mineral content (50%) comparable to that of dentin. Cementum is not usually apparent radiographically because the contrast between it and dentin is so low and the cementum layer is so thin.

Diffuse radiolucent areas with ill-defined borders may be apparent radiographically on the mesial or distal aspects of teeth in the cervical regions between the edge of the enamel cap and the crest of the alveolar ridge.This phenomenon, called cervical burnout

This phenomenon, called cervical burnout, is caused by the normal configuration of the affected teeth, which results in decreased x-ray absorption in the areas in question. Furthermore, the perception of these radiolucent areas results from the contrast with the adjacent, relatively opaque enamel and alveolar bone. Such radiolucencies should be anticipated in almost all teeth and not be confused with root surface caries, which frequently have a similar appearance

The pulp of normal teeth is composed of soft tissue and consequently appears radiolucent. The chambers and root canals containing the pulp extend from the interior of the crown to the apices of the roots. Although the shape of most pulp chambers is fairly uniform within tooth groups

great variations exist among individuals in the size of the pulp chambers and the extent of pulp horns. The practitioner must anticipate such variations in the proportions and distribution of the pulp and verify them radiographically when planning restorative procedures.

In normal, fully formed teeth the root canal may be apparent, extending to the apex of the root; an apical foramen is usually recognizable

In other normal teeth the canal may appear constricted in the region of the apex and not discernible in the last millimeter or so of its length. In this case the canal may occasionally exit on the side of the tooth, just short of the radiographic apex. Lateral canals may occur as branches of an otherwise normal root canal. They may extend to the apex and end in a normal,

lamina dura A radiograph of sound teeth in a normal dental arch demonstrates that the tooth sockets are bounded by a thin radiopaque layer of dense bone. Its name, lamina dura ("hard layer"), is derived from its radiographic appearance. This layer is continuous with the shadow of the cortical bone at the alveolar crest

lamina dura It is only slightly thicker and no more highly mineralized than the trabeculae of cancellous bone in the area. Its radiographic appearance is caused by the fact that the x-ray beam passes tangentially through many times thethickness of the thin bony wall, which results in its observed attenuation. Developmentally the lamina dura is an extension of the lining of the bony crypt that surrounds each tooth during development.

lamina dura The appearance of the lamina dura on radiographs may vary. When the x-ray beam is directed through a relatively long expanse of the structure, the lamina dura appears radiopaque and well defined. When the beam is directed more obliquely, however, the lamina dura appears more diffuse and may not be discernible

supporting bone In fact, even if the supporting bone in a healthy arch is intact, identification of a lamina dura completely surrounding every root on each film is frequently difficult, although it usually is evident to some extent about the roots on each film. In addition,small variations and disruptions in the continuity of the lamina dura may represent superimpositions of trabecular pattern and small nutrient canals passing from the mandibular bone to the periodontal ligament.

The appearance of the lamina dura is a valuable diagnostic feature. The presence of an intact lamina dura around the apex of a tooth strongly suggestsa vital pulp. Because of the variable appearance of the lamina dura, however, the absence of its image around an apex on a radiograph may be normal. Rarely, in the absence of disease the lamina dura may be absent from a molar root extending into the maxillary sinus

ALVEOLAR CREST The gingival margin of the alveolar process that extends between the teeth is apparent on radiographs as a radiopaque line, the alveolar crest

The level of this bony crest is considered normal when it is not more than 1.5mm from the cementoenamel junction of the adjacent teeth. The alveolar crest may recede apically with age and show marked resorption with periodontal disease. Radiographs can demonstrate only the position of the crest; determining the significance of its level is primarily a clinical problem

The level of this bony crest is considered normal when it is not more than 1.5mm from the cementoenamel junction of the adjacent teeth. The alveolar crest may recede apically with age and show marked resorption with periodontal disease. Radiographs can demonstrate only the position of the crest; determining the significance of its level is primarily a clinical problem

PERIODONTAL LIGAMENT SPACE Because the periodontal ligament (PDL) is composed primarily of collagen, it appears as a radiolucent space between the tooth root and the lamina dura. This space begins at the alveolar crest, extends around the portions of the tooth roots within the alveolus, and returns to the alveolar crest on the opposite side of the tooth

CANCEllOUS BONE The cancellous bone (also called trabecularb on e o rspongiosa) lies between the cortical plates in both jaws. It is composed of thin radiopaque plates and rods (trabeculae) surrounding many small radiolucent pockets of marrow. The radiographic pattern of the trabeculae shows considerable intrapatient and interpatient variability, which is normal and not a anifestation of disease

MAXILLA Intermaxillary Suture The intermaxillary suture (also called the mediansuture) appears on intraoral periapical radiographs as a thin radiolucent line in the midline between the two portions of the premaxilla. It extends from the alveolar crest between the central incisors superiorly through the anterior nasal spine and continues posteriorly between the maxillary palatine processes to the posterior aspect of the hard palate. It is n6t unusual for this narrow radiolucent suture to terminate at the alveolar crest in a small rounded or V-shaped enlargement (Fig. 9-16). The syture is limited by two parallel radiopaque borders of thin cortical bone on each side of the maxilla. The radiolucent region is usually of uniform width. The adjacent cortical margins may be either smooth or slightly irregular. The appearance of the intermaxillary suture depends on both anatomic variability and the angulation of the x-ray beam through the suture.The intermaxillary suture may terminate in a V-shaped widening (arrow) at the alveolar crest.

Anterior Nasal Spine The anterior nasal spine is most frequently demonstrated on periapical radiographs of the maxillary central incisors. Located in the midline, it lies some 1.5 to 2 cm above the alveolar crest, usually at or just below the junction of the inferior end of the nasal septum and the inferior outline of the nasal fossa. It is radiopaque because of its bony composition and is usually V- shaped

Incisive Foramen The incisive foramen (also called the nasopalatine or anteriorp alatine foramen)i n the maxilla is the oral terminus of the nasopalatine canal. It transmits the nasopalatine vessels and nerves (which may participate in the innervation of the maxillary central incisors) and lies in the midline of the palate behind the central incisors at approximately the junction of the median palatine and

incisive sutures. Its radiographic image is usually projected between the roots and in the region of the middle and apical thirds of the central incisors (Fig. 9-23). The foramen varies markedly in its radiographic shape, size, and sharpness. It may appear smoothly symmetric, with numerous forms, or very irregular, with a welldemarcated or ill-defined border. The position of the foramen is also variable and may be recognized at the apices of the central incisor roots, near the alveolar crest, anywhere in between, or extending over the entire distance