Anomalies of Tooth Structure
Course Number: 651
Course Contents
Dens Invaginatus
Dens invaginatus is an inversion or enfolding of enamel into the crown, sometimes extending beyond the CEJ or into the root.5,9 Comparatively, dens invaginatus is an internal involution of tooth structure while dens evaginatus is an external outcropping of tooth structure.5,9
Dens invaginatus varies in the degree of tooth structure enfolding. Three types are recognized per Oehlers Classification, the most widely used nomenclature. (Table 4).10,11 These coronal invaginations usually involve the permanent maxillary lateral incisors but other permanent teeth can be affected including central incisors, premolar, canine, and molar teeth with the maxillary arch more frequently involved than the mandibular arch.5,9,10 The most common and least severe form of coronal dens invaginatus, Type I, is limited to the crown.10 Typically, the cingulum exhibits a small pit but an invagination of enamel can be present as well (Figure 41).5,9 The pit is prone to develop caries or possible explorer perforation into the pulp due to the thin layer of enamel.8
Type II exhibits more severe coronal invagination extending from the incisal edge to below the CEJ ending in a blind sac or involution of enamel.5,9 Radiographically, it may have the appearance of a radiolucent teardrop with a radiopaque outline (Figure 41).9 If the defect is more extensive, often the tooth crown is malformed and the invagination dilated giving the appearance of a dens in dente or tooth within a tooth.5,9 In cases where there is communication between the invagination and the pulp, necrosis will occur resulting in periapical disease.9 This may occur before the apex is completely formed and closed.5,9 The permanent maxillary lateral incisor teeth are most commonly affected with a tendency for bilateral occurrence.9
Type III dens invaginatus extends through the root either perforating it laterally or apically communicating with the PDL (Figure 42A and B).
The most severe form, dilated odontome, involves the tooth root with a doughnut-shaped invaginated defect lined with cementum.5,9 Radiographically, the affected tooth is significantly malformed displaying a radiopaque round or oval periphery with a radiolucent center as seen in Figure 43.5,9,12 This anomaly is rare and appears to be independent of the traditional classification system outlined in Table 4.12 The clinical relevance of these defects is the possibility of pulpal involvement and necrosis.5,9,10
| Type | Description |
|---|---|
| Type I | Defect is enamel-lined and confined to the tooth crown |
| Type II | Defect is enamel-lined and extends into the pulp chamber but remains within the root canal |
| Type III | Defect extends into the tooth root and perforates the root laterally or through the apical foramen (See subtypes A and B) |
| Type IIIA | Perforates the root laterally with PDLS communication; usually without pulp involvement |
| Type IIIB | Communicates with the PDLS at the apical foramen; usually without pulp involvement |
Figure 41.
Periapical radiograph of maxillary right central incisor tooth #8 with dens invaginatus Type I and lateral incisor tooth #7 with dens invaginatus Type II.
Figures 42A & 42B.
Periapical radiographs of maxillary right and left lateral incisor teeth #7 (A) and #10 (B) with dens invaginatus Type IIIB.
Figure 43.
Panoramic radiograph with developing dilated odontomes of mandibular premolar #20 & #29.