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April 2009 | Dental Products Report
The set-up “Let’s explore the use of Vita In-Ceram and the ELC process (electrophoretic deposition) to create restorations that are not only high strength, but can result in an excellent esthetic match, especially when covering different substrates (preps) that may vary in value (degree of darkness).”—Dr. Robert Lowe, Team Lead
There are many esthetic challenges dentists face when restoring teeth in the esthetic zone. When a natural tooth is lost and an implant is used to replace the missing unit, the esthetic demands can increase considerably because of bone and gingival positions relative to the remaining natural units and implant position. Add to that an endodontically treated tooth (low value) that requires a post and core build up prior to restoration placement, then the choice of restorative materials to cover all of these variety of abutments to create an esthetically uniform result can be the biggest challenge of all. Case in point(Refer to the slideshow for figures)
A common cause of tooth morbidity in the maxillary central incisor region is trauma to the face. The patient shown in Fig. 1 had received a traumatic blow to the anterior maxilla that resulted in the fracture of tooth Nos. 7 and 8. Tooth Nos. 8 and 9 had all-ceramic crowns that had been previously placed after a traumatic accident. Upon removal of the existing restorations, it was observed that No. 8 had sustained a vertical root fracture and would not be restorable (Fig. 2). Tooth No. 7, although horizontally fractured, would be saved, but would require root canal therapy and a post and core prior to restoration. It was decided after a discussion with the patient that tooth No. 10 would be electively restored to improve the tooth position in the arch (crowding) that existed pre-operatively and to improve esthetic proportions. After tooth preparation, a provisional restoration was placed on tooth Nos. 7 through 10 (Fig. 3). The fractured tooth (No. 8) will be atraumatically extracted at the time of implant placement. This step is crucial as preservation of interproximal and facial bone during the extraction process is essential to papilla position marginal gingiva respectively after implant placement. Also, by placing a precision provisional restoration, it can be used as a surgical guide during implant placement to replicate the correct facial angulation and mesio-distal position of the pilot hole. At the time of implant placement, the provisional maxillary right central incisor will then be converted to a pontic allowing the implant to integrate without any esthetic compromise to the provisional restoration. Custom abutment, provisionalsSecond step: Guiding the gingival maturation during osseointegration using a custom abutment and provisional restoration. One restorative challenge faced when replacing a natural tooth with an implant is that while the natural root form in this case is triangular, the artificial root (implant) is cylindrical. This can be a problem when trying to create natural gingival esthetics. One solution is to use a custom implant abutment that replicates the natural root form of the implant platform. Also, the placement of the implant platform relative to the free gingival margin is just as critical. There must be enough distance between the implant platform and the FGM to shape the emergence profile and have a subgingival margin for the restoration. This means sometimes the surgeon must remove some crestal bone to get the implant submerged to the correct position. A common problem exists when the implant platform is too close to the free gingival margin. When this occurs, natural emergence profiles are impossible to achieve and unesthetic “black triangles” will be the result. Fig. 4 shows a fixture level impression coping placed on the implant and marginal retraction for the post and core that will be fabricated for tooth No. 7. Note the palatal position of the implant relative to the adjacent central incisor. Tissue sculpting and placement of a connective tissue graft will be necessary to create the proper facial emergence position for the implant restoration. A diode laser (Biolase Technology’s ezlase, biolase.com) is used to sculpt an “ovate pontic” type site around the implant platform that resembles the correct triangular “egression silhouette” (emergence profile) for the implant abutment/restoration complex (Fig. 5). A master impression is then made for the fabrication of a cast post and core for tooth No. 7 and an Atlantis Implant Abutment from Astra Tech (astratech.com) for the tooth in the No. 8 position. An Atlantis abutment is chosen because of the design of this CAD/CAM-generated abutment closely resembles the natural prepared tooth. The result will be a more naturally esthetic gingival profile of the definitive restoration. Once these are received from the laboratory, they are placed on the respective units and the provisional restoration is altered and realigned to accommodate the new preparation shapes (Fig. 6). After osseointegration is complete (about 4 months) the case will be ready for master impression making for the restorations. Fig. 7 shows how the patient-specific CONTINUED ON NEXT PAGE
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Interview with Dr. Robert A. Lowe 
