What type of intra-oral appliance shall I use?
Any appliance that is secure. Any appliance that you would use with a facemask, i.e., braces, an acrylic palatal appliance with retention that makes it secure when the elastics are connected to the Crane.
If the patient needs lateral expansion, as well as forward pull, it is best to do this treatment in two stages; first pull the maxillae forward, then do the lateral expansion, or vice versa. Too much at one time is not a favor to the body.