Material and methods

A sample of 28 patients (18 female, 10 male; ages, 17.4 ± 4.3 years) with 37 impacted canines was assembled from the private practices of the 3 authors. The patients’ initial records showed that 26 impactions were palatal, 9 were buccal, and 2 were in the midalveolus. All patients had been treated elsewhere for a malocclusion that included at least 1 impacted maxillary canine that did not respond to treatment. They were referred by general practitioners or orthodontists and were taken consecutively in the referral system for inclusion in our investigative sample. In this study, an orthodontist was defined as a dentist who has received specialty training in a state-recognized university graduate orthodontic course.

Of the sample, 9 patients had bilateral impaction of the canines, and each failed canine was considered separately in the study. From the patient records, the following treatment information was gathered.

• 1.

  Details related to the initial treatment: had the treating practitioner received specialist orthodontic training (as detailed above) with more or less than 10 years of postgraduation experience, or was he or she a general practitioner with more or less than 10 years since graduating from dental school; was the patient transferred in relation to the surgical exposure (before, after); was the patient transferred in relation to the stage of orthodontic treatment (before orthodontic treatment or after the failed treatment); was radiographic documentation used for the original diagnosis; how many times was surgical exposure performed on the tooth; was the surgery successful; how was traction applied (patients were differentiated into those whose traction was performed directly to the labial archwire and those whose traction had 2 stages, first vertically downward to clear the root of the incisor and then laterally into its place in the arch); was the anchorage base intra-arch dental, interarch dental, extraoral, or implant; how much time elapsed between the start of treatment and the realization of failure; and what were the assumed reasons for failure.

• 2.

  Details related to the second orthodontic treatment: were additional radiographic records needed; what was the outcome of revised treatment (success or failure); how long was the revised treatment; what were the revised reasons for initial treatment failure; and what corrective measures were adopted (new surgery, altered direction of traction, reinforced anchorage).

Results

The patients were referred by 26 clinicians. Twenty were specialists, including 15 who had over 10 years of experience, and 6 were general practitioners, including 3 with more than 10 years of experience. Most patients (26 of 28; 92.9%) were referred after surgery had been performed. In 2 (patients 11 and 22), space had been prepared for the impacted teeth without surgery. It had been optimistically expected that the teeth would erupt spontaneously, but that had not occurred. Twenty-five patients (89.3%) had been referred during active orthodontic treatment and 3 after the treatment was stopped because of failure.

Table I describes the initial treatment plans. Panoramic and cephalometric films were available for all patients, together with variable numbers of periapical views. Two patients had undergone 3D imaging, one (patient 8) with conventional spiral computed tomography (CT), and the other (patient 12) with cone-beam CT (CBCT). Among the 35 canines that had previously been exposed, 10 (28.6%) had had 3 such episodes. In 1 bilateral case (patient 3), who had been treated by open exposure, the bonded attachments had failed on both canines, and the tissues had subsequently rehealed over the teeth. In 2 (patients 6 and 24), the surgeon had failed to find the impacted tooth because of misdiagnosis of labiolingual location.

Elastic traction, directly to the arch, was used for 26 canines. For the 7 canines treated in 2 stages, an auxiliary spring was used, with the express aim of erupting the canine into the palate as the initial maneuver. The orthodontic anchorage used in all patients in this sample consisted exclusively of intraoral dental anchorage from other dental units with fixed bonded appliances; this was therefore omitted from Table I . The mean duration of treatment, from start to realization of failure, was 26.2 ± 17.2 months. The reasons for failure, as assumed by the practitioners, were ankylosis (17 teeth, 45.9%), incisor root resorption (6 teeth, 16.2%), intractable position (3 teeth, 8.1%), attachment failure (3 teeth, 8.1%), surgical failure (2 teeth, 5.4%), and inadequate follow-up period (2 teeth, 5.4%). In 6 teeth (16.2%), the orthodontist could find no explanation for the failure, and, for 2 patients, 2 reasons were given.

Table II shows the supplementary records that were considered necessary for each patient. As the result of the new information and consequent practical steps taken, the success rate of the revised treatment plans was 67.6% for the whole group. However, 2 patients (2 canines) refused more treatment, yielding an actual success rate of 71.4%. The mean duration of the new treatment in the successful patients was 14.4 ± 7.2 months. After this, it became possible to diagnose the reasons for failure in each patient more accurately. The major causes were poor anchorage (18 teeth, 48.6%), mistaken positional diagnosis and directional traction (15 teeth, 40.5%), and ankylosis (12 teeth, 32.4%). Seven ankylosed teeth were treated by surgical luxation and subsequent traction, but only 3 were successfully brought in their place in the arch. In 5 patients (6 teeth, 16.2%), resorption of the incisor roots had escaped the practitioner’s notice until treatment was advanced. Three teeth (8.1%) failed to erupt because of interference of soft tissues. In 3 patients (8.1%), inadequate space was considered to be a cause for noneruption. In one (patient 6), surgery was initially performed at the wrong site, and, in another patient (24), the tooth was in an extremely difficult position; therefore, these teeth remained unexposed after surgical intervention. In 2 patients (11 and 22), traction was never applied, and the first practitioner waited in vain for 54 and 30 months, respectively, for the teeth to erupt unaided. Repeated bond failure of the attachments after surgery in 2 patients (3 and 7) accounted for treatment failure. In 1 patient (24), both the first practitioner and the surgeon did not realize that the canine crown was situated on the palatal side between the central and lateral incisors, but its root was labial to the root of the lateral incisor. This created an intractable situation, from which there was no possibility of saving the tooth. In 1 patient (5), the treatment failed because of poor compliance (missed appointments) and inefficient appliances. In several patients, there were 2 or more possible reasons for failure.

Table III summarizes the corrective measures taken for this group of potentially failed patients. Surgery was needed for 22 of the 35 canines (62.9%). Of these, 7 (in 5 patients) were to redirect the ligature wires to permit a change in direction of traction, 3 (in 3 patients) to clear soft tissues, 7 (in 4 patients) to luxate ankylosed canines; 3 teeth needed bond attachments, and 2 were reoperated to expose them in their newly diagnosed positions. In 2 patients, exposure was performed for the first time. Orthodontic corrective measures included the application of traction in 4 canines to which forces had never been applied. A change in the direction of traction was mandatory for 15 canines. Anchorage was reinforced by various methods in 18 canines and included heavier base archwires, intermaxillary elastics, and temporary implant devices in the more recent cases. Additional space was needed in 2 patients (2 canines).