Abstract: Ten studies, reporting data from 354 participants, were included in this review, the majority of which were carried out in a university dental hospital setting. The studies were published between 2005 and 2011 and were conducted in Europe and in Brazil. The age range of participants was from nine to 15 years, with an even distribution of males and females in seven of the studies, and a slight predominance of female patients in three of the studies. The quality of the studies was generally poor; seven studies were at an overall high risk of bias, three studies were at an unclear risk of bias, and we judged no study to be at low risk of bias. We carried out random-effects meta-analyses as appropriate for the primary clinical outcomes of movement of upper first molars (mm), and loss of anterior anchorage, where there were sufficient data reported in the primary studies. Four studies, involving 159 participants, compared a distalising appliance to an untreated control. Meta-analyses were not undertaken for all primary outcomes due to incomplete reporting of all summary statistics, expected outcomes, and differences between the types of appliances. The degree and direction of molar movement and loss of anterior anchorage varied with the type of appliance. Four studies, involving 150 participants, compared a distalising appliance versus headgear. The mean molar movement for intraoral distalising appliances was -2.20 mm and -1.04 mm for headgear. There was a statistically significant difference in mean distal molar movement (mean difference (MD) -1.45 mm; 95% confidence interval (CI) -2.74 to -0.15) favouring intraoral appliances compared to headgear (four studies, high or unclear risk of bias, 150 participants analysed). However, a statistically significant difference in mean mesial upper incisor movement (MD 1.82 mm; 95% CI 1.39 to 2.24) and overjet (fixed-effect: MD 1.64 mm; 95% CI 1.26 to 2.02; two studies, unclear risk of bias, 70 participants analysed) favoured headgear, i.e. there was less loss of anterior anchorage with headgear. We reported direct comparisons of intraoral appliances narratively due to the variation in interventions (three studies, high or unclear risk of bias, 93 participants randomised). All appliances were reported to provide some degree of distal movement, and loss of anterior anchorage varied with the type of appliance. No included studies reported on the incidence of adverse effects (harm, injury), number of attendances or rate of non-compliance. It is suggested that intraoral appliances are more effective than headgear in distalising upper first molars. However, this effect is counteracted by loss of anterior anchorage, which was not found to occur with headgear when compared with intraoral distalising appliance in a small number of studies. The number of trials assessing the effects of orthodontic treatment for distilisation is low, and the current evidence is of low or very low quality.

Plain-language summary: This review of existing studies was carried out by the Cochrane Oral Health Group, and the evidence is current as of December 2012. In this review there are 10 studies published between 2005 and 2011 in which a total of 354 children were randomised to receive treatment with a distalising orthodontic appliance and compared to either no treatment, headgear or another distalising appliance. The age range of children in nine of the studies was from 11 to 15 years, although the children recruited to one study were younger, from nine to 10 years old. Both girls and boys participated in the studies. Where it was mentioned, the funding was from a university or dental research foundation. The authors did not assess the impact of the funding sources. When intraoral appliances are compared to headgear they will probably move the upper molar teeth backwards more than headgear. However, the use of intraoral appliances was also associated with movement of the upper front teeth when compared to extraoral appliances in four studies. This is an unwanted effect that was not observed with the use of the headgear appliances. Harm, injury from the appliances and other characteristics of the appliances which may be important to patients were not reported in the studies. The evidence presented is generally of low quality. The main shortcomings were related to trial design.