Implant Impression: What about Splinted Impression Copings?

The object of making an impression in implant dentistry is to accurately relate an analogue of the implant or implant abutment to the other structures in the dental arch. This is achieved by use of an impression coping which is attached to the implant or implant abutment. This impression coping is incorporated in an impression much as a metal framework is ‘picked up’ in a remount impression for fixed prosthodontics. With implant copings the coping is usually attached to the implant or abutment with screws. The impression material used is usually an elastomeric impression material; the two types most widely used and shown to be the most appropriate are polyether and polyvinyl siloxane impression materials [1]. Many articles have been written and many in vivo studies have been carried out to improve the fidelity of impressions over the use of pick up type impression copings alone [2]. Characteristics of the pickup type impression coping are that they are removed from the mouth together with the set impression. They require access to the retaining screw to allow release of the screw prior to removal of the impression coping impression assembly the analogues are attached to the impression copings while they are embedded in the impression tray. A custom tray with access to the impression coping screws is required [1]. An accurate transfer of relationship of multi-unit implants from mouth to the master cast demands a rigid splinting of impression copings. Auto-polymerizing acrylic resin, the most commonly used material for such splinting, exhibits polymerization shrinkage resulting inaccurate transfer of spatial relationship of implants from mouth to the master cast [3]. Numerous impression techniques have evolved to improve accuracy [4,5]. One technique involves tying open-tray impression copings together with floss, then splinting them together with self-curing resin [6].