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    How to efficiently remove fixed restorations with crown cutters

    Why crown cutters from Komet USA LLC are ideal for working with different restorative materials.

    The removal of all-ceramic and porcelain-fused-to-metal (PFM) crowns is routine in modern dental practices where fixed-prosthetic restorations are among the most commonly used treatments. The specific properties of different restorative materials, however, require special crown cutters to ensure effective, efficient removal. This is especially important when dealing with the new generation of high-performance ceramics, which have considerably improved the long-term clinical prognoses of these restorations.

    Restoration longevity

    Recent studies have shown comparable five-year survival rates for the following anterior crowns: PFM crowns (94.7 percent), all-ceramic crowns made of lithium silicate (96.6 percent) or zirconium oxide (92.1 percent)6. Similar survival rates of 94.4 percent to 95.6 percent were established for tooth- or implant-supported PFM bridges3,4. The failure of a fixed restoration can be due to biological (e.g., secondary caries or endodontic complications) or technical reasons (e.g., material fracture)2,7,8. The failure of tooth-supported PFM crowns and bridges is primarily related to biological complications3,6, whereas implant-supported PFM restorations frequently fail due to technical problems such as fracture of the ceramic veneer1,3-6.

    Read more: Komet expands line of ceramic cutters

    Tooth- and implant-supported all-ceramic bridges and crowns on molars and premolars also exhibit an increased rate of technical complications due to ceramic-veneer fracture2,3,4. To reduce the incidence of such complications, the use of monolithic bridges made of high-strength glass ceramics or translucent zirconium-oxide ceramics is recommended3,6. Common reasons for the biological failure of tooth-supported crowns and bridges include secondary caries and endodontic complications7. In some cases, an anterior fixed prosthetic restoration might be removed because of undesirable esthetics1-6 (Fig. 1).

    Fig. 1

    Fig. 1

    In summary, clinical data suggest an annual loss risk of approximately 1 percent in cases of fixed crowns and bridges, meaning that one in 100 integrated restorations are expected to be lost per year1-4,6. The removal of all-ceramic or PFM crowns is, therefore, an essential treatment carried out regularly in any dental practice.

    Aside from various techniques for the nondestructive removal of crowns and bridges with mechanical or compressed-air powered devices, the most common method for removing a restoration is opening it and then manipulating or breaking it8. Due to the specific properties of the different restorative materials, the removal of PFM and all-ceramic crowns places special demands on the clinical procedure.

    Komet USA has created a line of highly efficient instruments to cut through any crown quickly and easily: the H35L crown cutter features a special blade geometry for use on non-precious metal and gold; the H4MC®L cutter for metal and ceramic is ideal for PFM and hard-metal crowns, efficiently cutting through ceramic veneers and any underlying metal structure without requiring instrument changes; and the 4ZR and 4ZRS Jackie™ crown cutters meet the challenges of removing all-ceramic crowns and are especially effective on those made of extremely hard ceramic materials such as zirconia.

    The following guidelines present the steps necessary for removing PFM and high-strength all-ceramic restorations using the Komet® H4MCL and 4ZRS Jackie crown cutters.

    Continue to page two to read more...

    Dr. Sven Rinke
    Dr. Sven Rinke has been a dental practitioner at a group practice in Hanau/Kleinauheim, Germany, since 2002. He specializes in implant ...

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