The Haas "Memory" Transverse Expansion Appliance utilizes acrylic to support a spring-loaded expansion screw. Adjusting the spring-loaded expansion screw -- three 90-degree turns once every three days -- delivers a continuous positive biologic force of about 500g over a distance of 0.8 to 1mm. Many practitioners prefer this appliance over the coil-spring activated RPE appliances. Because acrylic closely contacts the palatal mucosa, more bodily movement and less tipping occurs. The forces generated by the appliance are applied to the teeth and the palatal tissues. Caution: If hygiene is not carefully monitored, acrylic can cause serious inflammation. Note:Pre-formed bands may be selected and sent with the prescription or bands may be custom fit. Because this appliance uses four bands for retention, seating of the appliance can prove challenging.

Recommended:
• Leave separators in place until the delivery appointment.
• When the path of insertion is a problem, apply gentle pressure to allow seating over time.
• Cement bands with a glass ionomer cement.