Delayed-Immediate Approach to Implant Restoration of Maxillary Left Central Incisor
Thomas J. Salinas, DDS
A 56-year-old male patient presented with a nonrestorable tooth #9 (Figure 1). The tooth was extracted and a standard externally hexed implant was placed using the delayed immediate approach. The existing proportion between the crown on tooth #8 (Figure 2) and the implant-supported provisional crown restoration on tooth #9 revealed asymmetry in form. The correct these discrepancies, it was decided to electively retreat tooth #8 with an all-ceramic crown restoration that would distribute the space evenly between the two teeth.
Following an appropriate healing period, definitive impressions were made of the implant body and surrounding tissues. Preservation of the soft tissue profile can be cumbersome, unless the provisional restoration is used to fabricate a modified impression transfer post (Figure 3). The transfer post preserves the soft tissue profile and the configuration of the abutment and provisional restoration. Using this prefabricated abutment system, the soft tissue outline is preserved by the transfer assembly for the definitive restoration (Figure 4).
Once the impression has been recorded, a soft tissue replica cast (Figure 5) is fabricated to provide an estimate of the soft tissue level surrounding the implant. The cast should be made of a flowable elastomeric material that exhibits sufficient rigidity to resist permanent deformation. When the cast has been fabricated, the abutment try-in kit may be utilized again to select the appropriate abutment (Figure 6). Depending on the extent of correction required in the angulation, either a 0- or 15-degree indirect abutment may be selected.
However, after ordering the correct abutment and prior to sending the case to the laboratory, the clinician may wish to prepare the abutment in such a manner that it exhibits the dimensions of a conventional tooth preparation for a crown (Figures 7 and 8). Since the abutment exhibits an oblong or triangular shape in cross-section, no antirotational feature in the coronal aspect of the abutment is required (Figure 9). One of the primary advantages of the system is the ability to transfer the indirect abutment system and send it to the laboratory for fabrication of the definitive restoration on the abutment itself. The other advantage is that the removal of the impression post facilitates inspection of the periimplant tissues for residual impression material, which is impossible if the abutment is allowed to remain in place and traditional crown and bridge impression procedures are performed.
The use of two indirect abutments may be required in cases where a provisional abutment is used to develop soft tissue profiles and the second abutment is forwarded to the laboratory. At the time of prosthetic delivery, the abutments are exchanged, and the definitive restoration is cemented. In this case, the abutment and die of tooth #8 were scanned utilizing the most recent technology to create a core of high purity aluminum oxide (Figure 10). The technique utilizes the concept of computer-aided design to create a high-strength ceramic core with optical properties that masks the metallic abutments, yet provide the desired optical properties in the cervical region. According to the manufacturer's recommendation, laminating porcelain is added to the ceramic core to create a gradual emergence with appropriate line angles, proximal surfaces, highly chromatized opacious dentin, and opalescent enamel. The fit and the optical properties of industrially fabricated copings eliminates the need for shoulder porcelain (Figure 11). Clinically, the indirect abutment should be placed into the implant site and verified radiographically for complete seating. At this time, the abutment is secured by torquing to 32 Ncm with a torque wrench (Figure 12).
The tissues are prepared for try-in and cementation by assessing the fit of the restorations with a silicone-dislodging medium. The accuracy of the fit will depend primarily upon the precision of the impression, since the dies/abutments are scanned with the aid of a computer. The copings produced are machined to have a uniform relief of 60 um above the finish line to allow space for cement internally. If the restoration binds on a particular area, the preparation, not the internal surface of the restoration, should be relieved. This measure will restrict the development and propagation of microcracks to an absolute minimum.
Once the restoration is adjusted for correct proximal and occlusal contact, the area should be prepared for cementation. Numerous cements are available today, and due to the high strength of the ceramic system utilized, the clinician should select the cement accordingly. Nonimpregnated retraction cord is placed beneath the finish line, and the restoration is tried in to ascertain that the cord does not restrict placement. The restoration is filled with the cement and seated with firm pressure; any excess is allowed to set completely. The excess cement and the retraction cord are then carefully removed with a curette. A radiograph may be taken to ascertain that all of the cement has been removed. The patient is instructed regarding appropriate oral hygiene procedures ot maintain the tissue health (Figure 13).
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