Fixed or removable appliance for early orthodontic treatment of functional anterior crossbite : evidence-based evaluations of success rate of interventions, treatment stability, cost-effectiveness and patients perceptions

Abstract: Anterior crossbite with functional shift also called pseudo Class III is a malocclusion in which the incisal edges of one or more maxillary incisors occlude with the incisal edges of the mandibular incisors in centric relationship: the mandible and mandibular incisors are then guided anteriorly in central occlusion resulting in an anterior crossbite.Early correction, at the mixed dentition stage, is recommended, in order to avoid a compromising dentofacial condition which could result in the development of a true Class III malocclusion and temporomandibular symptoms. Various treatment options are available. The method of choice for orthodontic correction of this condition should not only be clinically effective, with long-term stability, but also cost-effective and have high patient acceptance, i.e. minimal perceived pain and discomfort. At the mixed dentition stage, the condition may be treated by fixed (FA) or removable appliance (RA). To date there is insufficient evidence to determine the preferred method.The overall aim of this thesis was therefore to compare and evaluate the use of FA and RA for correcting anterior crossbite with functional shift in the mixed dentition, with special reference to clinical effectiveness, stability, cost-effectiveness and patient perceptions. Evidence-based, randomized controlled trial (RCT) methodology was used, in order to generate a high level of evidence. The thesis is based on the following studies: The material comprised 64 patients, consecutively recruited from the Department of Orthodontics, Faculty of Odontology, Malmö University, Sweden and from one Public Dental Health Service Clinic in Malmö, Skane County Council, Sweden. The patients were no syndrome and no cleft patients. The following inclusion criteria were applied: early to late mixed dentition, anterior crossbite affecting one or more incisors with functional shift, moderate space deficiency in the maxilla, no inherent skeletal Class III discrepancy, ANB angle> 0º, and no previous orthodontic treatment. Sixty-two patients agreed to participate and were randomly allocated for treatment either with FA with brackets and wires, or RA, comprising acrylic plates with protruding springs. Paper I compared and evaluated the efficiency of the two different treatment strategies to correct the anterior crossbite with anterior shift in mixed dentition. Paper II compared and evaluated the stability of the results of the two treatment methods two years after the appliances were removed. In Paper III, the cost-effectiveness of the two treatment methods was compared and evaluated by costminimization analysis. Paper IV evaluated and compared the patient´s perceptions of the two treatment methods, in terms of perceived pain, discomfort and impairment of jaw function. The following conclusions were drawn from the results: Paper I • Anterior crossbite with functional shift in the mixed dentition can be successfully corrected by either fixed or removable appliance therapy in a short-term perspective. • Treatment time for correction of anterior crossbite with functional shift was significantly shorter for FA compared to RA but the difference had minor clinical relevance. Paper II • In the mixed dentition, anterior crossbite affecting one or more incisors can be successfully corrected by either fixed or removable appliances, with similarly stable outcomes and equally favourable prognoses. • Either type of appliance can be recommended. Paper III • Correction of anterior crossbite with functional shift using fixed appliance offers significant economic benefits over removable appliances, including lower direct costs for materials and lower indirect costs. Even when only successful outcomes are considered, treatment with removable appliance is more expensive. Paper IV • The general levels of pain intensity and discomfort were low to moderate in both groups. • The level of pain and discomfort intensity was higher for the first three days in the fixed appliance group, and peaked on day two for both appliances. • Adverse effects on school and leisure activities as well as speech difficulties were more pronounced in the removable than in the fixed appliance group, whereas in the fixed appliance group, patients reported more difficulty eating different kinds of hard food. • Thus, while there were some statistically significant differences between patients´ perceptions of fixed and removable appliances but these differences were only minor and seems to have minor clinical relevance. As fixed and removable appliances were generally well accepted by the patients, both methods of treatment can be recommended. Key conclusions and clinical implications Four outcome measures were evaluated: -success rate of treatment, treatment stability, cost-effectiveness and patient acceptance, which is important from both patient and care giver perspectives. It is concluded that both methods have high success rates, demonstrate good long-term stability and are well accepted by the patients. Treatment by removable appliance is the more expensive alternative. Thus, in the studies on which this thesis is based, fixed appliance emerges as the preferred approach to correction of anterior crossbite with functional shift in the mixed dentition.