What is an impacted tooth?

The Glossary of Periodontal Terms defines impacted tooth as:

An unerupted or partially erupted tooth so positioned that complete eruption is unlikely

Impacted canines are a relatively common finding in dental practice. After the third molar, the maxillary canine is the most frequently impacted tooth. The prevalence of impacted maxillary canines is reported to range from 1.5 to 4% (Elefteriadis & Athanasiou, 1995; Ericson & Kurol, 1988; Fox et al, 1995; Stewart et al 2001). The maxillary impacted canine is more frequently located palatally (85%) than labially (15%). The orthodontist can use the patient dental age timetable to decide whether to monitor progress, initiate prophylactic treatment, or recommend surgical exposure of the tooth.

Eruption and Dental Age
Tooth	Maxilla (yrs)	Mandible (yrs)
Central Incisors	7	7
Lateral Incisors	8	7.5
Canine	11-12	9-10
1st Premolars	10-11	9-10
2nd Premolars	11-12	9-10
1st Molars	6	6
2nd Molars	12	12

When interpreting the dental age table, three situations are possible:

• The root development is within the normal range but slow (there is a gap between dental and chronological age). No action should be taken
• Dental and chronological age coincide but one or more teeth are late in erupting after root formation is complete. Extraction of primary teeth is indicated.
• Dental and chronological age coincide but the root formation of one or more teeth remains incomplete. Progress should be monitored and no immediate action should be taken.

By the time two thirds of a tooth’s root is formed, it should have emerged into the arch. If the crown remains at some distance from the alveolar crest after its physiological eruption time because of insufficient room or an ectopic pattern, it is said to be impacted.

Diagnosis of tooth impaction

The orthodontic-surgical management of impacted canines requires accurate diagnosis and precise location of the impacted canine and the surrounding structures.

The panoramic radiograph is the basic radiograph for detecting impacted teeth because it provides an overall view of the maxilla, mandible, alveolar processes, dentition and nasal fossae. In summary, a panoramic radiograph provides:

• Tooth position, whether deep o shallow
• General orientation, horizontal or inclined mesially/distally
• Relationship with neighboring teeth
• Risk of tooth transposition
• Presence of absence of apical resorption of the roots of adjacent teeth.

The panoramic radiograph has the limitation of superimposing structures making the precise localization of the impacted tooth, difficult or even impossible. Furthermore on this type of radiograph it is very difficult to evaluate the exact inclination of canine teeth which are situated  where the arch curves distally.

Periapical films can also provide important information for the treatment of impacted teeth. By taking two or more periapical films of the same region with different angulations of the xray source and a long-cone technique, it is possible to determine tooth position.

Clark’s rule: If three objects are aligned on the axis of the central ray, their images will be superimposed on the film. If the x-ray source is moved laterally but remains aimed at the three objects, individual images of each will appear on the radiograph. The object closest to the film will appear to have moved in the same direction as that of the x-ray source.

An easier way to remember this is the acronym SLOB: Same Lingual, Opposite Buccal. An example is presented in the illustration above. The two fingers represent two teeth, if we “record” a new image of the “teeth” moving our head towards the right or left, the finger further away (“palatally impacted”) from our eyes will appear to move in the same direction.

Occlusal radiographs are a useful supplement to other radiographic examinations, providing a third, horizontal dimension by which to assess the size of the maxilla. Occlusal radiograph can be used with an orthogonal technique, a lateral technique or a combination of both.

Computerized tomography (CT), or more recently cone-beam computerized tomography (CBCT) play a major role in the planning of canine exposure, as well as improve clarity and facilitate communication between the member of the dental team and the patient.

Treatment options for impacted canine

For patients with impacted teeth, several treatment options are available. After clinical and radiographic analyses, patients and parents can be presented with the advantages and disadvantages of three options:

• No treatment. If a patient decide to have neither surgical nor orthodontic treatment, the dentist should monitor the impacted tooth by radiographic examination, looking for the development of pathologic changes such as root resorption of adjacent teeth. The patient is informed of all associated risks, including the poor prognosis for long-term retention of the short-rooted primary canines.
• Extraction of the impacted tooth. Once it is extracted the tooth can be replaced with an implant or a fixed partial denture. Another solution is to move the distal teeth forward, replacing the missing canine with the first premolar.
• Combined surgical and orthodontic treatment. This is the most satisfactory option. With a combined surgical and orthodontic approach and impacted tooth can be brought to the ideal position, therefore achieving esthetic and function.

Combined surgical-orthodontic treatment

Based on the location of impaction, the canine tooth can be exposed with a palatal or a buccal approach.

With the palatal approach for canine exposure the incision is made within the gingival sulcus of the teeth adjacent to the area of impaction. The incision can be extended to the other quadrant if a bilateral exposure is planned. Preparation of the bony window should be started at a safe distance from the central incisors. After bonding the attachment, the osseous tissue still separating the crown from the edentulous crest can be removed. Uncovering the tooth destroys a portion of the follicular envelope and thus reduces the eruptive potential for bone resorption. Before replacement of the palatal flap, an opening of 5x5mm can be created in the mucosal surrounding the attachment.

Buccal flaps can be replace or displaced. A simple gingival incision (direct access flap) is sometimes indicated when the impacted tooth has been located by clinical and radiographic examination, has already emerged through the bone, is located near the space in the arch prepared for it, and is covered by dense fibrous tissue.

The apically displaced flap offers a few advantages over the replaced flap:

• Assists a physiologic process by allowing for surgical emergence of the tooth
• Allows for orthodontic control of the tooth’s movement and long axis
• Allows for placement, replacement, or removal of a bonded attachment without additional surgery

To be able to use an apically displaced flap for canine exposure the tip of the crown of the impacted canine must be near the mucogingival line of the lateral incisor. To ensure a satisfactory esthetic result, the gingival displacement should not exceed a few millimeters. If the tooth is impacted in a higher position, a replaced flap should be used. The apically displaced flap can also be set laterally for buccally impacted canines that are lying across the roots of lateral incisors and could compromise the periodontal health of adjacent teeth.

More info about the author: Alessandro Geminiani, DDS, MSc, MS is a specialist in periodontics and dental implants. His practice focuses on canine exposure and is located in Rochester, NY.