Permanent maxillary canines are the second teeth that most commonly assume ectopic positions after the third molars. They are diagnosed as impacted and have an incidence of 1 % to 3%

In their ectopic path of eruption, they can cause damage (resorption) of the adjacent roots, a severe complication that may lead to the loss of anterior teeth. When cone-beam computed tomography (CT) scanning is used for diagnose, root resorption is detected in two-thirds of the lateral incisors adjacent to impacted maxillary canines before treatment.

The treatment of this condition comprises two stages: a surgical intervention to uncover the canine crown followed by orthodontic treatment to move the canine into correct position. The surgical intervention commonly involves two different techniques: the open and the closed technique.

The open technique procedure involves removing the bone and mucosa covering the crown of the canine. The exposed crown is left uncovered and a pack is placed over the area to avoid overgrowth of tissue. When enough spontaneous eruption of the canine has occurred, an orthodontic attachment is bonded to the crown and the tooth is moved above the mucosa with orthodontic appliances into the correct position.

The closed technique procedure involves bonding an orthodontic attachment to the crown with a chain after exposing the canine during the surgery. The palatal flap is sutured back covering the exposed crown and the chain is left through the palatal mucosa free in the oral cavity. Shortly after, the canine is forced to erupt through the palatal mucosa and moved into the correct position with orthodontic appliances.

The purpose of this prospective randomized clinical trial is to compare outcome variables between the Open and Closed surgical exposure techniques regarding the success of treatment, patient's perceptions of pain and discomfort experienced and analgesic consumption, treatment time, and complications. The null hypothesis is that similar outcomes occur when the surgical exposure of palatally impacted canines is performed by using the open or the closed surgical technique.

Consecutive patients planned for surgical exposure of uni- or bilateral palatally impacted canines of two centers, are invited to participate in the Trial. The centers are the University Orthodontic Departments of Oslo, Norway, and Jonkoping, Sweden.

Potential participant patients and their parents are given verbal and written information about the Trial and Informed Consent is obtained.

Participants are randomly allocated to one of two interventions by use of Permuted Block Randomization in order to maintain equal allocations across treatment groups. Allocation concealment is held by one individual in each center that is not involved in the study. No stratification is made for age or gender in the two groups.

If the maxillary deciduous canine is present at the time of the surgery, the tooth is removed together with the exposure of the impacted canine.

Before entering the surgery room, participants answer a first questionnaire on whether they are experiencing pain or discomfort (measured in VAS-scales) in the area of the impacted canine and whether they have taken analgesics. The questionnaire is filled in and delivered back before entering the surgery room. After the surgical exposure, verbal and written information and recommendations on chlorhexidine mouth rinse and analgesic consumption are given. A second questionnaire is then handed out for participants to self-report the pain-discomfort they experienced during surgery, and are experiencing in the evening the same day and the following seven days together with the analgesic consumption. The second questionnaire is delivered back to the clinic at the post-surgical control.

At the post-surgical control, participants receive a third questionnaire where they self-report the pain-discomfort they experienced during and after sutures (closed technique) and packing (open technique) are removed.

After the surgical exposure with the open technique, the canine is left to erupt spontaneously. Participants are follow-up by the orthodontist until the canine has erupted enough (approximately ½ - 1/3 of the crown above the level of the palatal mucosa) to bond an attachment to the crown. The canine then starts to be moved into alignment in the dental arch above the mucosa with orthodontic appliances.

After the surgical exposure with the closed technique, the impacted canine starts to be moved with orthodontic appliances within 2 weeks after surgery. The canine is moved into alignment in the dental arch through the mucosa.

From the completion of the surgical exposure phase until the previously impacted canine is orthodontically positioned in the dental arch, similar questionnaires are handed out to the participants in both treatment groups every second/ third orthodontic control.

The participants are followed until the active orthodontic treatment is finished and orthodontic retainers bonded.

Schedule/ registrations:

Before the surgical exposure phase of treatment (T0)

• Clinical anamnesis
• Routine dental clinical examination. Assessment of periodontal pocket depth, gingival bleeding on probing, gingival recession in the lateral incisor in the impacted and nonimpacted contralateral side.
• Study models. Assessment of occlusion traits, presence of maxillary deciduous canine.
• Panoramic radiograph. Assessment of the position of the impacted canine: mesial position, mesial inclination, and distance to the occlusal line according to Ericson and Kurol.
• Cephalogram. Assessment of upper incisor sagittal inclination.
• CBCT (cone beam computed tomography). Assessment of the exact impacted canine position, size of the impacted canine's follicle, crestal bone height in the lateral incisor in the impacted and nonimpacted contra lateral side, root resorption of the impacted canine, lateral incisor, and first premolar in the impacted and nonimpacted contra lateral side

Surgical exposure day (T1)

• Questionnaires are handed out to the participants for assessment of pain and discomfort (measured on VAS-scale) and analgesic consumption : (1) before surgery same day (2) after surgery same day and following 7 days, (3) post-surgery control same day and following 7 days.
• Registrations at the surgery: duration of the operation, complications, depth of the impacted canine from the mucosa surface.

The previously palatally impacted canine has erupted (approximately 1/3-1/2 canine crown above palatal mucosa) (T2)

• Questionnaires are handed out to participants between T1 and T2 for assessment of pain and discomfort (measured on VAS-scale) and analgesic consumption the same day and following 7 days after every second/ third orthodontic control
• Timespan T1-T2
• Complications associated with the eruption of the canine since surgery

The previously palatally impacted canine is aligned in the dental arch and ligated to a 0.016 X 0.022 nickel-titanium / standard steel archwire in the 0.018- appliance system or a 0.019 X 0.025 nickel-titanium / standard steed archwire in the 0.022- appliance system (T3)

• CBCT (cone beam computed tomography). Assessment of the position of the canine root, crestal bone height in the canine, lateral incisor, and first premolar in the impacted and nonimpacted contra lateral side, root resorption of the impacted canine, incisors, and first premolar in the impacted and nonimpacted contra lateral side
• Questionnaires are handed out to participants between T2 and T3 for assessment of pain and discomfort (measured on VAS-scale) and analgesic consumption the same day and following 7 days after every second/ third orthodontic control
• Timespan T2-T3
• Complications associated with the orthodontic alignment of the previously impacted canine into the dental arch.

The active orthodontic treatment is finished and an orthodontic retainer is fitted (T4)

• Routine clinical examination. Assessment of periodontal pocket depth, gingival bleeding on probing, gingival recession in the canine, incisors and first premolar in the impacted and nonimpacted contra lateral side.
• Study models. Assessment of occlusion traits.
• Panoramic radiograph. Assessment of root parallelism, root resorption.
• Cephalogram. Assessment of upper incisor sagittal inclination.

Except for the CBCT examinations and questionnaires, all the examinations and treatments performed in this trial are the routine examinations and treatments of palatally impacted maxillary canines performed in Norway and Sweeden. All the surgical exposures and orthodontic treatments are performed by or under the supervision of the same specialist in oral surgery and orthodontics, respectively, in each center, with many years of experience.

Inclusion Criteria:

• Consecutive patients diagnosed with palatally impacted canine with a sagittal position in Zone 2-4 as documented on panoramic radiographs according to the criteria proposed by Ericson and Kurol,1988, planned to start treatment with surgical exposure of the impacted canine.
• Patients with uni- or bilateral impacted canines are included. In bilateral impaction cases, the more severely positioned impacted canine according to the Zone (Zone 2 - 4) is included in the trial.
• No restriction of presenting malocclusion
• Dental developmental stage: Maxillary DS2M1 and DS3M2 according to Bjork.
• Age not older than 16 years at surgery

Exclusion Criteria:

• Agenesis of lateral incisors on the impaction side
• Peg-shaped lateral incisors on the impaction side
• Previous orthodontic treatment
• Subjects with craniofacial deformity/ syndromes
• Documented learning disability
• Communication problems related to the language when an interpreter is needed
• Sagittal position of the impacted canine in Zone 5, according to Ericson and Kurol, documented on panoramic radiographs.