To Örebro University

OBJECTIVE: To evaluate the costs of open and closed surgical exposure and subsequent orthodontic treatment for the correction of palatally displaced canines (PDCs).

TRIAL DESIGN: A multicentre, two-arm parallel group randomized controlled trial.

METHODS: One hundred twenty adolescents between 9 and 16 years of age, from three orthodontic specialist centres, were randomized to one of the two surgical exposure interventions. The randomization was conducted according to a two-arm parallel group 1:1 allocation ratio, using computerized lists with block randomization. In both the surgical techniques, whole mucoperiosteal flaps were raised, and bone covering the PDCs was removed. In the open technique, glass ionomer was built up on the PDC crown - reaching above the mucosa through a hole punched in the flap - to allow the canine to erupt autonomously. After eruption, the canine was orthodontically moved above the mucosa. In the closed technique, an eyelet was bonded onto the PDC, the flap was repositioned and the canine was orthodontically moved beyond the mucosa. The trial ended when the PDC was successfully aligned in the dental arch.Cost analysis was performed including costs for surgery, orthodontic treatment, emergency visits, and material, as well as costs for transports and time spent in connection with every appointment.

BLINDING: Patients and caregivers could not be blinded due to obvious limitations of the clinical setting, while outcome assessors and data analysts were blinded.

RESULTS: A cost-minimization analysis was performed since both exposure groups succeeded equally well in terms of treatment effects. The two different surgical exposures and following orthodontic treatments did not differ significantly in terms of costs.

GENERALIZABILITY AND LIMITATIONS: Costs are estimated in the Swedish setting, which needs to be considered if applying the results in other settings. Calculations of total cost do not include finishing, debonding, retention, and follow-up.

CONCLUSION: There is no significant difference in costs between closed and open surgical exposure with following orthodontic treatments in PDCs.

TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT02186548.

The maxillary permanent canine usually erupts in the mouth between the ages of 11 and 12 years. Sometimes the canines are displaced toward the palatal side of the dental arch and eruption is disturbed. Palatally displaced canines (PDCs) are a frequent dental anomaly, present in 2% of the young population. If untreated, there is risk of damage to the roots of the adjacent teeth and potential tooth loss. Thus, early interceptive treatment with extraction of the deciduous canine should be undertaken, with the aim to improve the PDC eruption path. If the eruption path does not improve within about a year, surgical exposure and orthodontic treatment is indicated.

The two different main techniques of surgical exposure in PDCs are the open and the closed techniques. Retrospective studies of the exposure techniques have shown differences in outcomes, which high-lights the need for evidence-based research.

The overall aim of this thesis was to compare outcomes of treatment duration, complications and side effects, patients’ perceptions and health economic aspects of the two surgical techniques, in PDCs. Moreover, a comparison of PDC position between the two radiographic methods commonly used in PDC cases; panoramic radiograph and CBCT, aimed to evaluate agreement between the actual measures. 

This thesis was based on a multicentre randomised controlled trial with two parallel groups, including 120 consecutive patients, aged 9 to 16 years, who were randomly allocated to open or closed surgical exposure. 

The following conclusions were drawn:

The agreement of PDC mesiodistal position was fair (weighted kappa 0.36 (95%CI0.24–0.49) and the mean difference in angle to midline was almost 7˚ (95%CI 5.9˚–7.9˚) higher in panoramic radiographs compared with CBCT. Surgery time, treatment time, root resorption or periodontal measures showed no clinically significant differences between the exposure groups. The open group reported higher pain intensity up to one week post surgery. A higher proportion of bilateral open group cases experienced complications, and weremore frequently wakened at night post surgery. The closed group reported higher pain and discomfort during the orthodontic traction. All PDCs were successfully aligned in the dental arch. A cost-minimization analysis showed no differences in healthcare or societal costs.

OBJECTIVES: To compare treatment time, patients' perceptions during orthodontic treatment, dental fear and side effects, between open and closed surgical exposures in patients with palatally displaced canines (PDCs).

TRIAL DESIGN: Multicentre, randomized controlled trial, with random 1:1 allocation of two parallel groups.

MATERIALS AND METHODS: One hundred and twenty patients from three different orthodontic centres were randomized into one of the two intervention arms, open or closed surgical exposure. Both techniques had mucoperiosteal flaps raised and bone removed above the PDCs. In open exposure, tissue was removed above the canine, and glass ionomer - reaching above soft tissue - was built on the crown. The canine was then left to erupt spontaneously, prior to orthodontic alignment. At closed exposure, a chain was bonded to the canine and orthodontic traction was applied under the mucosa until eruption. Orthodontic alignment of the canines was undertaken after eruption into the oral cavity, with fixed appliances in both groups. All participants were treated according to intention to treat (ITT).

BLINDING: Due to the nature of this trial, only outcome assessors could be blinded to the intervention group.

RESULTS: One hundred and seventeen patients completed the trial. All PDCs were successfully aligned. Total treatment time was equal in the two techniques, mean difference -0.1 months (95% CI -3.2 to 2.9, P = 0.93). The closed group experienced more pain and discomfort during the active orthodontic traction. Dental fear, root resorption and periodontal status did not show any clinically significant differences between the groups.

GENERALIZABILITY: Results of this randomized controlled trial (RCT) can be generalized only to a similar population aged 9-16 years, if exclusion criteria are met.

CONCLUSION: The closed exposure group experienced more pain and discomfort mostly during active orthodontic traction. All other studied outcomes were similar between the two exposure groups.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, ID: NCT02186548 and Researchweb.org, ID: 127201.

OBJECTIVES: The early interceptive treatment of palatally displaced canines (PDCs) has for decades been based on their position in panoramic radiographs. In the 1990s, cone-beam computed tomography (CBCT) started to become popular in cases with PDCs. The aims of this prospective study were to evaluate the agreement of PDC sector position and angle to midline between panoramic radiographs and CBCT scans.

METHODS: PDC sector and angle to midline were measured in panoramic radiographs and CBCT scans in 58 consecutive patients with 64 PDCs. Kappa with linear weighting was used to assess the agreement between the measurements of PDC sector position and Bland-Altman limits of agreement to assess the agreement between the PDC angular measurements in the 2 methods.

RESULTS: PDC sector position and angle to midline had systematically higher values in panoramic radiographs compared with those in the CBCT scans. The agreement of sector position between the methods was fair: weighted kappa 0.36 (95% CI 0.24-0.49). The mean difference in angle was almost 7° (95% CI 5.9°-7.9°) higher in panoramic radiographs compared with CBCT.

CONCLUSIONS: Panoramic radiographs overestimate PDC sector and angle to midline position, compared with the use of CBCT scans, but clinically the differences are quite modest. Panoramic radiographs could be considered good enough for rendering PDC position when the need for 3D information is not crucial for treatment planning.