CATEGORY AUSTRALASIAN DENTIST 63 LINICAL u Delayed eruption, marked distal angulation or retroclination, microdontia or absence of the permanent lateral incisor. b. Radiographic examination Radiographic examination is required to demonstrate: u The presence of the canine and its position within the maxillary arch u The condition of adjacent teeth (particularly the degree of resorption associated with the deciduous canine or presence of any resorption associated with the permanent incisors) u Cystic changes u Dilacerations of roots u Displacement of adjacent teeth The position of the canine should be evaluated in all three planes of space: u Buccopalatal relationship to the dental arch; u Height relative to the occlusal plane; u Angulation relative to the mid-sagittal plane; and u Distance from the mid-sagittal plane Various radiographic exposures including occlusal films, panoramic views, and lateral cephalograms can help in evaluating the position of the canines, in most cases, periapical films are uniquely reliable for that purpose. u Periapical films: A single periapical film provides the clinician with a two-dimensional representation of the dentition. It would relate the canine to the neighboring teeth both mesiodistally and superoinferiorly. To evaluate the position of the canine buccolingually, a second periapical film should be obtained by one of the following methods. – Tube shift Technique or Clark’s rule or SLOB rule or Buccal Object Rule Two periapical films are taken of the same area, with the horizontal angulation (mesio-distal movement) of the cone changed when the second film is taken. If the object moves in the same direction as the cone, it is lingually positioned. If the object moves in the opposite direction, it is situated farther to the source of radiation and is therefore buccally located (SLOB-Same side Lingual / Opposite side Buccal). – Buccal object rule: If the vertical angulation of the cone is changed by approximately 20° in two successive periapical films, the buccal object will move in the direction opposite to the source of radiation. On the other hand, the lingual object will move in the same direction as the source of radiation. The basic principle of this technique deals with the foreshortening and elongation of the images of the films. Parallax method: One standard projection is taken and then the tube is shifted horizontally or vertically. On each film, the image of root of lateral incisor and crown of canine will be seen. Horizontal parallax uses a horizontal shift in the X-ray tube (usually with successive periapical views taken with the tube moved horizontally). If the tooth is placed palatally, the image moves in the same direction as the X-ray tube. If the tooth is labially placed, the image moves in the opposite direction as the X-ray tube. Vertical parallax uses a vertical shift in the tube (usually counter checked with panoramic and anterior occlusal view). If the canines move down as the X-ray tube moves up, they are therefore buccally positioned. If the canine moves up same as the X-ray tube also moves up, it is therefore positioned palatally. u Occlusal Films: Determine the buccolingual position of the impacted canine in conjunction with the periapical films, provided that the image of the impacted canine is not superimposed on the other teeth. u Extra oral films: Frontal and Lateral cephalograms can sometimes aid in the determination of the position of the impacted canine, particularly its relationship to other facial structures (e.g., the maxillary sinus and the floor of the nose). u Panoramic films: To localize impacted teeth in all three planes of space, as much the same as with twoperiapical films in the tube-shift method, with the understanding that the source of radiation comes from behind the patient; thus, the movements are reversed for position. u CT/CBCT: Clinicians can localize canines by using advanced threedimensional imaging techniques. CT scanning, although it has a very large exposure, can be suggested in specific cases of palatally impacted canines that are suspected to have caused root resorption of the lateral incisors. The slices of the radiograph show the relationship of the impacted tooth to adjacent teeth in all the three planes. CBCT is the most preferred method to diagnose and localize an impacted tooth in recent years. The proper localization of the impacted tooth plays a crucial role in determining the feasibility of as well as the proper access for the surgical approach and the proper direction for the application of orthodontic forces. 5. METHODS OF TREATMENT FOR IMPACTED CANINE There are four possible methodologies of treatment. Leave alone: The option to leave a maxillary canine in situ is usually made on the basis that the patient is happy with their dental appearance and does not wish to have any form of treatment. u Ideally, the canine should not be closely associated with the erupted dentition.
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