Over the years, many devices have been designed to remove crowns and bridges from abutment
teeth.1-5 These crowns and bridges may be fabricated from dental acrylics cemented to the abutment teeth with nonrigid temporary cements, or they may be definitive restorations fabricated from cast metal, porcelain-metal, ceramic, or composite resin cemented with more rigid cements. While the removal of temporary crowns and bridges is usually very straightforward, the removal of a definitive cast crown with an unknown cement is more challenging. For a temporary crown or bridge, the restoration can be removed using a hand instrument, usually a scaler or large spoon excavator, or crown-removing pliers or a hemostat exerting force parallel to the long axis of the tooth. The crown or bridge is gently moved until the cement seal is broken. The restoration is then easily and atraumatically removed by breaking the weak cement seal between tooth and restoration.
Unfortunately, the routine removal of temporary restorations does not parallel the decisions that must be made when a patient presents with a defective crown and bridge that need to be removed and replaced with a new restoration. The same techniques used for the removal of temporary restorations can lead to disastrous results. While there are many designs of crown removers that use a bumping force created by a weight sliding on a bar or an air-driven motor to knock the crown or bridge off the tooth, these devices are radical and can cause considerable damage. When a crown-and-bridge bumper is used to remove an existing restoration, the practitioner usually doesn’t know what cement was used to place the restoration. Whether a highly retentive, adhesive resin-modified glass ionomer cement or resin cement was used, or a traditional zinc phosphate cement, the overriding goal when removing the crown or bridge is to do it without causing any damage to the abutment tooth, the periodontal supporting apparatus, or the pulp. A crown bumper, even if it is well controlled, can cause fracture of the crown of the tooth, root fracture, pulpal injury, or injury of the periodontal ligament. The author has personally witnessed defective crowns and bridges that, when removed with a crown bumper, have either fractured the abutment tooth at the gingival line, fractured the root, or luxated the tooth out of the socket. In several cases, the tooth needed endodontic therapy. The dental students or practitioners did not know how to control the forces of the device, nor did they know how many hits on the tooth were necessary before changing techniques.
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