A clinical trial has been carried out on 198 patients with fixed appliances to compare the relative performance of a glass ionomer cement with a zinc phosphate cement as an orthodontic luting agent. It was found that 13.2% of zinc phosphate cemented bands became loose over 24 months compared with 2.3% of bands cemented with glass ionomer. Furthermore, glass ionomer cement appeared to protect the enamel against demineralisation beneath the bands.