Orthodontic Treatment in Adolescents With Crowding and Displaced Teeth From the Clinical, the Patients' and Economic Perspectives

Overall project design The primary outcomes of treatment will be tooth alignment and function on the clinical level. Other outcomes on the clinician's, patients and societal levels as well as adverse effects will be considered as secondary outcomes. The treatment consists of two phases, first an active treatment phase with fixed appliance during 2 years to align the arches. Secondly, the so called retention treatment, aimed at stabilization and maintenance of the achieved correction. This means that the active treatment and follow-up will last for 7 (2+5) years.

Subjects The patients, recruited from four orthodontic specialist clinics (two clinics in Region Skåne), are boys and girls aged 12 to 17 years with crowding and tooth displacement. Adolescents with craniofacial syndromes, previous orthodontic treatment, ongoing sucking habits and persisting primary teeth will be excluded as well as patients with crowding and displacement treated with extraction. The patients will be randomized in two groups and treated to a pre-set standard concept developed for each treatment group, the conventional with bracket system (Straight-wire, 3M®) and the new with self-ligating bracket system (Damon®). The randomization will follow recommendation from the CONSORT group. A statistician will perform the randomization for all clinics according to "Permuted block design" with equal number in both groups. To obtain the (random) sequence, a computerized random-number generator will be used.

Power analysis To test the null hypothesis that the two population means are equal on tooth alignment and function the criterion for significance (alpha) has been set at 0.050. The test is 2-tailed, i.e. an effect in either direction will be interpreted. With the proposed sample size of 75 in each group, the study will have power of 86% to yield a statistically significant result. The computation assumes that the mean difference is 500 SEK and the common within-group standard deviation is 1000 SEK. This was selected as the smallest effect that would be important to detect, in the sense that any smaller effect would not be of substantive significance.

Key action 1 - Evaluating the treatment methods at the clinicians' level Specific aim 1: To compare the techniques on ease of use, time at chairside and for maintenance Rationale: Orthodontic treatment with fixed appliance demands technical skill and is time-consuming. Therefore it is motivated to evaluate the techniques with regard to ease of use, time at chairside and time for maintenance. The new technique, self-ligating bracket system, is supposed to produce low-forces due to low-friction and this should facilitate more efficient tooth movement,extended intervals between appointments and reduction of chairside time. Presently there is insufficient evidence to support these assumptions. Methods: Protocols of the treatment with the techniques will be used to document treatment time, number of visits, defaults and cancellations. Expected outcome: We expect to find the self-ligating technique to result in shorter total treatment time compared with the conventional technique. The self-ligating technique will also be easier and quicker to handle when changing wires.

Key action 2 - Evaluating treatment outcomes at the clinical level Specific aim 2: To evaluate tooth alignment, function and morphological stability of the techniques under comparison Rationale: The goal of orthodontic treatment is to achieve an occlusion with good function, esthetical appearance and long- term stability. Immediately following completed treatment results are usually satisfactory with ideal occlusion and appearance. The few long-term studies indicate that during a follow-up time of at least 5 years crowding often arise.