1 year 3 month-old Male, Neutered, Yorkshire Terrier

History: One year, 3 month-old Yorkie presented for routine dentistry with moderate tartar. Minimal gingival pockets (<1 mm). Please comment on teeth 309 and 409.


Findings: The apical portions of both roots of 309 and 409 have lost their lamina dura and well-defined lucencies are present at both roots. The distal aspect of the periapical lucency at the mesial root of 309 has an osteosclerotic rim. There is dorsal displacement of the pulp floor at the mesial and middle pulp chambers of 309 and 409. The mesial and central pulp horns at 309 appear completely cut off from the pulp chambers and subsequently the root canal at the mesial root of the tooth. There is a small well-defined periapical lucency at 311.  There is a lucency within opacity surrounding it on the central tooth structure of 109. There is an opacity with a lucent structures surrounding it at the central aspect of 209.  There are endoliths (pulp stones) at 108, 208, 309, 409 and 411.   There are missing teeth at 105-106, 205-206, 305-306, 310, 405-406 and 410. The second mandibular premolars are deciduous teeth (706, 806), with no permanent successors, that can be noted by their slender morphology compared to their surrounding teeth and the relative lack of enamel.  There is an ovoid opacity (with a lucency surrounding it) mesial to the mesial root of 806.  There are convergent roots at 309 and 409. There are most likely enamel pearls attached to 309 and 409 coronal to the furcation. There is lamellar periosteal bone production at the ventral to 309 and 409


The appearance of 309 and 409 are typical of dens invaginatus (DI) or dens in dente.  DI is a developmental malformation that has the radiographic appearance of a tooth inside the pulp chamber of another tooth, but histopathologic examination reveals the structure is an infolding of the tooth’s own enamel and dentin into the pulp canal.  There are no reported incidences of DI in dogs but the reported incidence in humans ranges from 1-10% of the population.  In the dog, DI has only been reported in the mandibular first molar, where it occurs almost exclusively, and the maxillary canine tooth (once).  At the mandibular fist molar it is almost always bilateral.  DI occurs in all breeds.

Q & A:

What is typically seen clinically with DI? 

  1. Enamel pearls which are abnormal circular areas of enamel of various sizes at the crown, the root or at the cementoenamel junction, that alter the normal external contour of the tooth.
  2. Signs of a non-vital tooth
    • A parulis which is a draining tract in the mucosa overlying the apex of the tooth
    • A discolored tooth
  3. May see signs of secondary periodontitis (gingivitis, gingival recession +/- clinical furcation exposure).

What are radiographic signs of tooth non-vitality?

  1. Wide apical periodontal ligaments and/or periapical lucencies indicative of apical periodontitis (apical inflammation/bone lysis)
  2. Inflammatory root resorption
  3. Wide pulp cavities compared to the contralateral teeth (indicating lack of dentinogenesis at non-vital tooth).

What are the radiographic signs of DI?

  1. Various opacities associated with the crown
  2. Dorsal displacement of the pulp floor (usually at the middle pulp horn +/-additional areas)
  3. It is very common to see lack of endodontic patency (inability to follow the entire pulp canal….a portion of the canal gets “cut off”

If DI is seen at 309, was an image of 409 provided? Are the same radiographic signs seen? 

A contralateral image is always necessary as it is most commonly seen bilaterally at the mandibular first molar.

  1. The sides are most commonly, but not always, classified with the same type
    • Type I (an enamel lined invagination into the crown only)
    • Type II (invagination extends into the root and ends in a blind sac which may or may not communicate with pulp)
    • Type III (invagination that penetrates root and exits the root apically or laterally that usually does not communicate with pulp)
  2. If there is bilateral DI with same type, will it have the same radiographic appearance?
    • No, the endodontic patency may be different as the sizes of the enamel pearls can be varied.
      • Smaller pearls do not affect patency and all portions of the pulp cavity (root canal) can be accessed
      • Larger pearls can cut off portions of the root canal.
    • Also, both sides may appear anatomically identical, but are different in terms of the pulpal vitality.
      • 309 may be vital and 409 may be non-vital.

Does the invaginated area always communicate with the pulp?

  1. Not always (see types) but many do or will communicate (as the area of invagination may be incompletely lined by enamel)

How to determine treatment options?

  1. If periapical disease is present, endodontic treatment (root canal therapy) or extraction is indicated
    • If significant inflammatory root resorption, extraction is indicated
    • Endodontic patency
      • If all necrotic pulpal contents cannot be removed/sterilized, root canal therapy is not a viable option and extraction is indicated
  2. If no periapical disease is present
    • No obvious external openings in the invagination are seen, the tooth can be treated conservatively and monitored
    • If obvious external opening, can debride invagination and restore void if no pulpal communication is confirmed

What is important for teeth diagnosed with DI with no periapical disease?

  1. Annual radiographic monitoring and client education regarding clinical signs of non-vitality as endodontic disease may likely occur in future due to the presence of numerous fine (not detected by human eye) canals that connect the invagination with the pulpal space.


Dens Invaginatus of the Mandibular First Molars in a Dog

JVD Vol 21 (1) 2005 21-25

Endodontic Treatment of dens invaginatus in a dog

JVD 2009 26(4) 220-225

One comment

  1. FINDINGS: Surrounding the medial and caudal tooth roots of 309 and 409, there are well-defined, smoothly marginated regions of lucency. The bone surrounding these lucencies are normal.

    PRIMARY DIFFERENTIAL: Dentigerous cysts of 309 and 409. An alternative differential is odontogenic keratocysts.

    Thanks! Cool case!


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