An orthodontic appliance includes a mandibular arch expander and a maxillary arch expander which are interconnected by a pair of adjustable connector assemblies. The maxillary and mandibular arch expanders each include front and rear orthodontic bands which have bosses to facilitate connection of the connector assemblies to the arch expanders. The connector assemblies include an expandable tube assembly and a rod which extends through said expandable tube assembly. The expandable tube assembly has a mount at a first end thereof adapted to connect the connector to the rear orthodontic band of the maxillary arch. The rod has a mount adjacent a second end of the expandable tube assembly adapted to be connected to the front orthodontic bands of the mandibular arch expander. The tube assemblies each include a hollow posterior tube and an anterior tube which are telescopically connected. Preferably, the anterior tube has a hollow body which is externally threaded at its back end. The posterior tube has a hollow body defining a bore and is internally threaded at its front end of said tube. The posterior tube bore is sized to accept the anterior tube so that the two tubes can be threadedly connected together. The posterior tube includes holes adapted to receive a tool to facilitate adjustment of the position of the posterior tube relative to the anterior tube to alter the overall length of the retractable, extendible tube assembly. Further, anterior tube includes indicators, in the form of spaced apart tick marks, to inform a practitioner as to the length of the connector assembly.