Distal movement of maxillary molars. Studies of efficiency and timing of treatment

Abstract: Maxillary molar distalization is a frequently used treatment method in cases with crowding associated with dental Class II molar relationship or Class I skeletal relationship. Despite the fact that several studies have been published concerning the treatment outcome of different appliances for distal movement of maxillary molars, it is still difficult to interpret the results and evidence presented in these studies because a variety of study designs, sample sizes and research approaches exists. In view of this, well-designed randomized clinical trials comparing patient compliant and non patient compliant extra- and intraoral appliance as methods of distalizing maxillary first molars is desirable as well as a systematic review of the present knowledge. Furthermore, there is a need for further evaluations and knowledge about the most appropriate time to move maxillary molars distally, i.e. evaluation of movement efficiency including anchorage loss before and after eruption of second maxillary molars. The overall aim of this thesis was to evaluate the outcome measures by distalizing maxillary molars with either the conventional extraoral traction (EOA) or a intraoral fixed appliance (IOA) and also to evaluate the optimal timing of distalizing treatment – either before or after the eruption of the second maxillary molars. This thesis was based on two studies and a systematic review included in the frame story: Paper I was a randomized controlled trial involving 40 patients in orthodontic treatment. The study evaluated and compared the treatment effects of an EOA and an IOA for distal molar movement of maxillary first molars. Paper II was a retrospective study involving 40 patients evaluating the maxillary molar distalization and anchorage loss in two groups, one before (MD 1 group) and one after eruption of second maxillary molars (MD 2 group). The systematic literature search was made in 4 different databases to determine what appliances for distal molar movement of maxillary molars have been evaluated in an evidence based manner and with focus on the most efficient method and outcome of molar movement and anchorage loss. Also, the evidence-based standard of Paper I and II was evaluated. These conclusions were drawn: • The IOA was more effective than the EOA to create distal movement of maxillary first molars, and thus, for the clinician the IOA is the most favourable method. • Moderate and acceptable anchorage loss was produced with the IOA implying increased overjet whereas the EOA created decreased overjet. • The two appliances did not have any considerable corrective effect on Class II skeletal relationships and these appliances shall therefore only be used in cases of moderate dental sagittal discrepancies and arch-length deficiencies. • The most opportune time to move maxillary first molars distally is before eruption of the second molars, since molar movement is then most effective and the anchorage loss lesser. • There is limited level of evidence that intraoral appliance is more efficient than extraoral to create distal movement of maxillary molars and that anchorage loss was produced with the intraoral appliance. • It is still difficult to draw any conclusions as to which of the intraoral appliances that were the most effective, and therefore, more RCTs are desireable.