Modern Techniques for the Partially-Edentulous Patient

Figure 1. Initial picture showing 4-unit metal-ceramic fixed partial denture. Figure 2. Full-thickness mucoperiosteal flap elevated and immediate placement of a regular platform internal connection implant. Figure 3. Second endosseous implant placed in the correct position and angulations. Figure 4. Particulate bone placed in immediate implant site. Figure 5. Cover screws placed (hand-torqued) on endosseous implants. Figure 6. Zirconia custom abutments (Procera Zirconia [Nobel Biocare]) secured in place at 35 Ncm torque. Figure 7. All-ceramic restorations (Procera [Nobel Biocare]) were cemented (Premier Implant Cement [Premier Dental Products]).

INTRODUCTION
When the extraction of a tooth is the only viable alternative, the replacement of the missing tooth with an implant-supported restoration may be a realistic treatment option for some patients. The standard protocol requires 6 months (minimum) of healing time before the placement of an implant in an extraction site.^1,2 Immediate implant placement has been an alternative; this involves the placement of an implant immediately after the extraction of a tooth into that socket.³ Several studies have been conducted in which the success rate of the immediately placed implants is similar to that of implants placed after healing of the extraction site.^4,5 It is usually necessary for an immediately placed implant to engage bone apical to the extraction socket to achieve primary stability.
      Many times, the angulations and location of the immediately placed implant is different from that of the extraction socket. In many of these cases, a larger and tapered implant might be necessary to engage all the walls of the socket; in other cases, bone graft material should be used, and this way the possibility of soft-tissue growth between the implant and the bone is minimized. Several studies^6-8 have reported predictable results with the use of autogenous bone and primary closure of the site. Graft material, and the use of a membrane, as well as primary closure without the use of any bone material, is also a viable solution. These studies lead us to believe that the size of the defect and the type of wound closure is more important than the type of graft material used for the procedures.
      For implants placed immediately into extraction sites, the protocol involves a healing period of 8 to 12 weeks. By carefully selecting the appropriate situations, immediate implant placement into an extraction site is possible, reducing the time for the final tooth restoration.^9,10
     Computer-designed and computer-generated implant abutments have also changed the present restorative protocols for implant dentistry. With the 3-dimensional computer-aided design (3-D CAD) technique, the clinician is now able to design custom abutments and crowns and then to fabricate them using all-ceramic materials. Using the 3-D CAD technique, implant components with the desired height, width, and contour to support the adjacent tissue and to mimic the properties of natural teeth can be made.^11-13 The use of metal-free restorations provides aesthetic results and excellent biocompatibility and material strength.^14-16
     Customized abutments may be fabricated from several different dental materials. One example of 3-D CAD technology that we use in our practice is the Procera (Nobel Biocare) system. This system allows us to design and fabricate implant abutments from materials such as zirconium oxide and titanium.
     Customized abutments may be fabricated with the 3-D CAD technique in the following manner:
     A screw, with a graduated pin for determining height of the abutments, is placed into the implant replica embedded in the master cast to visualize and align the computer image with the master cast. The design software enables the alteration of the body of the abutment, as well as its angle, height, width, and taper. In addition, the gingival margin height and the emergence angle can be modified. The completed abutment design is represented on the screen, and then transmitted electronically to the production facility where it is milled. The implant abutment is delivered within 4 days of sending in the order.¹⁷
     This clinical case report involves the extraction of the left maxillary canine with the immediate placement of a regular platform implant at that site, as well as an implant in the position of the first premolar, both restored with all-ceramic restorations.

CASE REPORT
Diagnosis and Treatment Planning
A 45-year-old white female presented to the office with a chief complaint of discomfort in the area of the maxillary left canine, and movement of the 4-unit fixed partial denture expanding from the maxillary left canine to the first molar (Figure 1).
     After the clinical and radiographic evaluation was performed, it was determined that the left maxillary canine had a vertical fracture, deeming it nonrestorable. The other abutment tooth (the maxillary left first molar) was in good condition. There was movement noted in the 4-unit metal-ceramic bridge, caused by the fracture of the maxillary left canine. (It is important to note that the opposing dentition to the 4-unit fixed partial denture was a removable partial denture.)
     The patient was presented with 3 treatment options: (1) extraction of the maxillary left canine and placement of a removable partial denture to replace the edentulous span from the left canine to the second premolar; (2) extraction of the maxillary left canine, placement of 3 endosseous implants after a sinus lift procedure (to be able to place the most distal endosseous implant), and final restoration with single-unit all-ceramic restorations; (3) extraction of the maxillary left canine, placement of 2 endosseous implants in the position of the canine and the second implant as distal as possible (without compromising the maxillary sinus), and 2 all-ceramic single-unit restorations.
     The patient decided to proceed with the third option, even after explaining to her all the disadvantages (biomechanics, cleansibility, etc) of having to contour the 2 restorations to replace the space of 3 teeth. The patient did not want to have a sinus lift done.
     A complete medical examination was performed, as well as a review of her medical history, and there were no medical findings that would contraindicate dental care, including elective surgery.

Surgical Phase of Treatment
The 4-unit fixed partial denture was sectioned at the level of the left maxillary canine and the left maxillary first molar, the crown on the first molar was left intact and evaluated for margin integrity; it was deemed in good condition. A full-thickness mucoperiosteal flap was then elevated to expose the bone. The extraction of the left maxillary canine was performed, as atraumatically as possible. Then, a regular platform internal connection (Replace Select [Nobel Biocare]) 13 mm in length implant (Figure 2) was placed on the extraction site. On the position of the first premolar, a regular platform 10 mm in length was placed (Replace Select) (Figure 3). Particulate bone (Bio-Oss [Luitpold Pharmaceuticals]) was placed on the area of the maxillary left canine to fill the space between the extraction wall and the implant, even though primary stability was achieved (Figure 4). Next, cover screws were placed (Figure 5) and hand-torqued.
     The full-thickness mucoperiosteal flap was approximated, and a 3.0 synthetic absorbable suture (Vicryl [Johnson & Johnson]) was used to close the margins to permit healing by first intention.
After a period of 3 months, a second-stage surgery was performed to uncover the implants; the cover screws were removed and the healing abutments (Nobel Biocare) (3 mm in height) were hand-torqued.

Restorative Phase of Treatment Begun
After soft-tissue healing, in a period of 5 weeks, closed-tray impression copings were placed and verified radiographically for fit. An implant level impression was then performed to record the location of the implants, utilizing a closed-tray impression technique with vinyl polysiloxane impression material light body and heavy body. The impression was poured to create a soft-tissue moulage with an elastic pink-colored vinyl polysiloxane (Ivoclar Vivadent) and type V gypsum material (Die-Keen [Heraeus Kulzer)].
     The impression was then poured a second time utilizing the same materials mentioned above. With the second cast, provisional implant abutments were placed and used to fabricate a temporary fixed partial denture, with acrylic resin (Lang Dental Manufacturing).
     With the first poured cast, 2 custom zirconium abutments were fabricated using a 3-D CAD program (Procera [Nobel Biocare]). The abutments were then digitized using the touch probe scanner (Piccolo Procera [Nobel Biocare]) and zirconium oxide copings (Procera Zirconia [Nobel Biocare]) were fabricated. Due to its excellent flexural strength¹³ and fracture toughness,¹⁸ zirconium oxide was a good material option for this case. The veneering porcelain (NobelRondo [Nobel Biocare]) was then applied (layered and oven-fired) by the dental ceramist to complete the aesthetic portion of the crowns.

Delivery of the Final Restorations
At the delivery appointment, the all-ceramic custom abutments were placed and secured using 35 Ncm torque (Figure 6). The access openings were filled with cotton and wax. Then, the all-ceramic crowns were placed onto the abutments to verify marginal integrity, occlusal relationships, and aesthetics. The all-ceramic restorations were cemented onto the implant abutments (Figure 7) using provisional cement marketed for use with dental implant restorations (Premier Implant Cement [Premier Dental Products]).
     After the placement of the final restorations, the patient was recalled at one week and at one month. No occlusal adjustments were necessary.

DISCUSSION
Compared with the traditional protocol, no delay was necessary for bone healing, resolution of inflammation, and soft tissue recovery for immediate implant placement. The placement of an immediate provisional restoration might be impossible when wound closure is required for integration of bone substitute material that is placed in the space between the implant and the socket wall. By placing an implant immediately after the extraction, reductions of the number of surgical procedures can be accomplished. However, one must keep in mind that this technique can increase the difficulty of achieving primary stability.
      If the implant is not going to be placed exactly into the site of extraction socket—due to the position of the pre-existing tooth, bone topography, infection among others (careful preoperative assessment is necessary)—this might result in a space between part of the implant and the socket wall, unless a bigger implant is placed, or as in this case, grafting material is used.

CONCLUSION
Immediate implant placement on an extraction site where primary stability is achieved did not lead to an increased rate of complications. It also provided equally favorable soft- and hard-tissue integration, even after the use of particulate bone. With careful case selection, immediate placement of implants in extraction sites can be a predictable procedure.

References

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Dr. Abbo completed the master of science program degree in prosthodontics at the University of Michigan. For the following 2 years, he was a clinical lecturer at the same university. Currently he is a private practitioner in area of Miami, Fla. He has published and lectured internationally. He can be reached at (305) 710-3129 or at bill_abbo@hotmail.com.

Disclosure: Dr. Abbo reports no disclosures.