thick or greater, the restoration can be expected to be successful. The side walls which are normally totally sacrificed in the traditional crown are generally left far more intact with the CAD/CAM option. In regards to post and core buildups, these are generally contraindicated in CAD/CAM crowns as the resin bonding materials do best bonding the etched porcelain interface to the etched enamel/dentin interfaces of the natural tooth itself. The crownlay is also an excellent alternative to the post and core buildup when restoring a root canal-treated tooth. Crown removal At times it may be necessary to remove crown restorations to enable treatment of the tooth tissue underneath, especially to enable for non-surgical endodontic treatment of a necrotic or previously-treated pulp. Several methods are available and the choice is guided normally by the nature and quality of the crown restoration., i.e., whether it is to be retained or to be replaced. Factors to consider when deciding whether to retain or remove the crown include: Replacement cost (time and financial) Aesthetic Ease of removal Marginal integrity Planned restoration (including change from a crown to a bridge, or adapting the crown design to act as abutment for a partial denture) Access required to treat the tooth safely and effectively (especially with regards to access cavity design) Temporary crowns are easy to remove and replace therefore do not pose problems. Before removing definitive crown restorations it is important to plan for a provisional crown, especially if the crown to be removed is expected to be damaged in the process. This usually involves making an impression of the crown so a temporary can be fabricated chair-side or made by the dental laboratory. Several tools and methods are available, which can be classified by how conservative they are to the crown Normally the tooth, if heavily damaged, should be restored prior to a new crown (whether, temporary or definitive) is fitted. Matrix bands Application of a matrix band which is burnished into the undercuts and pulled vertically. Ultrasonic An ultrasonic tip can be applied to a cast metal crown to disrupt the cement lute. This method should be avoided with ceramic restorations as this may lead to fractures. Forceps and crown tractors Crown tractors and forceps can be used to grip the restoration and dislodge it from the tooth preparation. Crown tractors are designed to have rubber grips and powder on their beaks to reduce