INVISIBLE RETAINERS AND ALIGNERS

The invisible retainer, as we use them, was developed by Robert Ponitz of Ann Arbor, Michigan.2 Typically
this retainer is formed from a sheet of thin Biocryl™ or other similar material that is heated and forced by suction1,2 or pressure3 on to a work model of the dentition. This type of retainer has many uses in routine orthodontic practice, not only as a finishing and retention appliance, but also as an active treatment adjunct. The
development of the Invisalign® System of aligners for comprehensive movement, a logical outgrowth of this
technology.

FABRICATION OF INVISIBLE RETAINERS

The steps in invisible retainer fabrication have been described previously by McNamara and co-workers3 in the Journal of Clinical Orthodontics. This article is updated below. In this summary, the possibilities of making minor changes in tooth position with invisible retainers will be stressed.

Preparation of the Work Models

Upper and lower alginate impressions are made with standard aluminum trays, and a wax bite registration is obtained in centric occlusion to articulate the models, if the correct occlusion is not obvious.The impressions are poured in plaster and trimmed as standard work models with minimal base (Fig. 27-2). Before articulating the maxillary and mandibular work models, excess plaster and any bubbles on the articulating surfaces of the teeth should be removed carefully with a laboratory kinfe or waxing instrument.