Dr. Dean C. Vafiadis presents a case report that describes treatment of an edentulous patient involving the placement of eight implants and immediate restoration



Immediate placement of endosseous implants has become a predictable technique for many patients (Liu CLS, 2005; Ganeles J et al, 2001; Romanos GE, 2003; Jaffi RA, Kumar A, Berman CL, 1996). After the implants have been placed, many factors need to be evaluated for the fabrication and design of the provisional restoration. Critical factors in the fabrication of such a provisional include: torque value, stability of implants, arch-form, occlusion, opposing dentition, implant type, anterior-posterior (A-P) spread, facial esthetics, lip form, and evaluation of the buccal corridor (Sullivan DY et al, 1996; Tarnow DP, Emtiaz S, Classi A, 1997; Saadoun AP, 2004; Salama H et al, 1945; Hunt P, Ararat Y, 2006). During implant rehabilitation, many steps and procedures have to be successfully accomplished to restore a full-arch dentition in a timely fashion.

All of the preliminary surgical diagnostic steps—radiographs, wax-ups and dental scans—comprise the necessary surgical checkpoints to provide a successful surgery. For the restorative dentist, the most important of these is the diagnostic wax-up. Because many patients present with existing dentures, this step often gets overlooked. A full denture set-up will be necessary at some point, so the clinician should try to fabricate this wax-up as soon as possible so that, even before the surgical procedures, all the facial esthetics and phonetic considerations have already been addressed. A surgical stent can be fabricated from this wax-up, and an incisal position index may be used for scanning radiographs.

Case study
A 45-year-old man had been edentulous for 4 years and was a smoker. Facial esthetics had been compromised with the original denture. The lack of lip support was evident. The vertical dimension of occlusion (VDO) had collapsed (Figures 1 and 2). The denture had undergone many repairs as a result of compromised occlusion, and the teeth were too short and did not enhance his face. The ridge architecture was normal, and the bony hard tissue was available for implants. Bone and gingival evaluation was performed intraorally with dental scans.

For this patient, the plan was to place eight implants with immediate restoration in order to establish cross-arch stabilization with the interim prosthesis. The original prosthesis would be used for the provisional over provisional abutments that would be cement-retained. Using endosseous internal hexed implants (NanoTite™ Certain®, Biomet 3i™) and interim provisional abutments at the time of surgery facilitated the treatment, resulting in an efficient sequence with very minimal postoperative pain and swelling. In addition, it gave the patient confidence in chewing and socializing that had been lost when his teeth were originally removed.

Regardless of the type of interim prosthesis—immediate fixed restoration, original denture, or immediate denture—the provisional restoration must be fabricated after consideration of:

1.    Facial esthetics
2.    Central tooth position
3.    Restoration of the VDO
4.    Right side/left side dominance
5.    Phonetics and lingual position
6.    Smile line
7.    Buccal corridor and lip support

All of these factors play a critical role in the fabrication of the final implant-supported prosthesis, laboratory framework, and final facial esthetics. Without addressing these factors, the prosthesis may be short vertically with a lack of tooth support for the facial muscles and lips. The prosthesis will look artificial, and the occlusion will be compromised.

Procedure
A surgical full-thickness flap for visibility and true analysis of hard tissue was performed. Eight NanoTite™ Certain®  (Biomet 3i™) implants were placed in ideal positions (Figure 3). This placement, although guided by presurgical scans, still resulted in a 12-degree to 15-degree offset. Four 15-degree provisional abutments were used. Gold screws were used and tightened to 20 Ncm with a torque driver. The palatal and posterior portion of the denture was removed (Figure 4). Note: If the placement of the implants had been greater than 20 degrees in divergence, it would have been impossible to cement the prosthesis onto the implant abutments, and the prosthesis would have had to be screw-retained.

VDO verification  
After the denture was prepared, a VDO verification had to be made before relining the provisional restoration. Two reference points were chosen—one in the maxillary arch and one in the mandibular arch. For example, the cervical area at the gingival margin from implant position UL3 and the cementoenamel junction (CEJ) gingival margin of tooth LL3 were chosen arbitrarily. (Multiple reference points can be chosen to have more predictable repeated measurements.) These measurements were made with a digital caliper, which immediately displayed the distance in millimeters or inches. This tool meets the need for accuracy and takes into account patient variability. A single transverse horizontal axis can usually be located (Preston JD, 1979; Ortial JP, 1995). These measurements are based on facial esthetics, phonetics, anterior tooth position, and mandibular freeway space from the diagnostic denture. It is these measurements, when repeated intraorally, that determine the final VDO (Figure 5).

    

Provisionalization
Before relining the provisional, these measurements were confirmed. The remaining denture was relined with self-cured acrylic over the provisional abutments. Previous protocols described by Tarnow et al (1997) were used. After relining, the provisional was removed, trimmed, and polished. Centric occlusion and maximum intercuspation were corrected, and canine guidance was established. Using additional acrylic on the maxillary canines can ensure that the patient has canine guidance and posterior disocclusion in working movements (Figure 6). The prosthesis was cemented with IRM cement (3M™ EPSE™) and not removed for 3 months. After 4 months, the provisional was removed, and evaluation of the osseointegration of the implants was performed with the reverse-torque technique. A new impression of the edentulous ridge and fabrication of a wax rim was made during the healing phase. Six months after implant place-ment, the implants were exposed with a nonsurgical laser technique (Waterlase™, Biolase®), and Encode® (Biomet 3i™) healing/coded abutments were placed (Figure 7).

Final impression
Final impressions of the Encode® abutments were made (Figure 8), and the provisional was relined over these abutments. Accurate capture of 3 mm beyond the tissue and all the codes of the Encode® abutments are required criteria for success with this technique. Models were poured and mounted and ready for scanning.

Computerized abutments  
An optical light scanner was used to capture all of the information provided by the Encode® abutments. This information was used to design a perfect abutment for the prosthesis. Marginal placement of the facial and lingual gingival heights was determined by the clinician. The recommended depth of the abutment margin was 0.5 mm for posterior teeth, 1 mm for anterior teeth, and placement of the lingual margin of the abutment was at the height of tissue (Figures 9 and 10). The information relating to the abutment design was transferred to a milling machine, and the abutments were milled from a titanium block. The abutments were then placed on the master model and returned to the clinician for try-in (Figures 11 and 12).  

Verification   
Abutments were placed in each specific site based on the acrylic transfer index, which designated the orientation of each abutment as it related to the arch. Radiographs were made to verify the seating of all of the abutments. Because these abutments were fabricated with computerized landmarks, the tissue response and position circumferentially was very predictable (Vafiadis DC, 2007). Tissue position on the facial, lingual, mesial, and distal was calculated by the computer, and during the design phase, positioned as designated by the clinician (Figure 13). The recommended position in the maxillary posterior region was 0.5 mm below tissue level.



The new occlusion rim was fabricated for use to fit over the abutments so that final facebow transfer, VDO, and midline positions could be recorded. The midline was verified, and the facebow transfer was made. Tooth selection and position were verified. In addition, the original VDO reference position was measured and replicated in the new denture try-in. Evaluation was made at this point for lip support, phonetics, occlusion, VDO, and patient approval. After final approval, models were made from this provisional and used in the laboratory for various procedures and for the final fixed ceramometal prosthesis position (Figures 14 and 15).

Framework
This information facilitated the transfer of the teeth positions to the original abutment master model. An incisal index was made from a putty matrix, and this served as the guide for the ceramometal framework preliminary wax form. Using the cutback technique, a proper tooth alignment was created. This ensured that the position determined by the previous denture base would be replicated through to the wax design. Once all of the incisal positions had been verified, proper ceramic support was created to ensure even distribution of ceramic material throughout the prosthesis. Once this was confirmed, it was cast with high noble metal (64% gold). It was fitted onto the abutments on the original master model, trimmed, and polished (Figures 16 to 22).

Final placement
Final placement of the abutments using a torque driver to 25 Ncm, sealed with cotton balls and flowable composite (LuxaFlow™, DMG America), was accomplished. The framework was tried-in, and radiographs were taken. After it was confirmed that the castings adequately fit the abutments, a final VDO record was made from the metal framework to the opposing dentition with a rigid bite registration material (Regisil®, Dentsply). The measurements from the original reference points were repeated, confirming the final working VDO. A final pick-up impression with polyvinyl impression material was made (Impregum™, 3M™ ESPE™) for final facebow transfer (Artex®) and mounting (Figures 23 to 26).



Occlusion
Porcelain bis-bake was achieved with the proper mounting position. Hard- tissue pink porcelain was used to enhance esthetics and mimic natural-looking contours and anatomy. Occlusion contacts in centric position were confirmed to the original VDO recorded during treatment. Working movements and canine disocclusion were confirmed and replicated in line with the final diagnostic denture set up. After first try-in, the occlusion analysis was confirmed using a computer-generated device (T-Scan® III, Tekscan®) (Neff AW, 2009).

Appearance
Final facial esthetic evaluation and sculpting was performed. In addition, incisal interproximal disking was performed to create tooth individuality (Figures 27 to 31).



Discussion
Treating the maxillary edentulous area can be difficult unless proper planning is scheduled with the surgeon and the restorative dentist. Using a provisional denture set-up will help the clinician to evaluate the facial vertical dimension, incisal edge position, and placement of the implants based on the lip support, and develop the angulation of placement so that an immediate provisional can be placed. Using a rigid fixed position to determine the working vertical dimension and repeating this measurement throughout the treatment may be more accurate than extraoral markings on the face. Using computerized abutments to relate the placement of the implants and final abutments is beneficial. Anecdotally, the tissue response is very favorable with these abutments, and the tissue change after placement is minimal. Avoiding impression copings and repeated removal of healing abutments may preserve the integrity of the tissue and prevent recession. Final esthetics for implant restorations depend on proper VDO and filling out the buccal corridor, which is sometimes difficult. The use of hard tissue replacement and pink porcelain will also enhance the esthetic result. Using canine guidance and posterior disocclusion during working movements will reduce muscle clenching, similar to that of bite-plate therapy. This may also prevent the porcelain from fracturing during mastication. Using computerized abutments may give the clinician a more accurate and predictable way to fit abutments and try in metal/ceramic prostheses.



Additional Notes
In the past 3 years, since the completion of this patient’s treatment, digital acquisition technology has advanced (see Figures 32 to 35). Today, we can also scan the coded abutments and transfer the information directly to the implant companies through electronic files. This technology saves additional time and money for all parties. These digital programs are now being married together to serve clinicians and patients more effectively. The design technician is also given more information, improving the design of the CAD/CAM abutments. During the design phase, we are providing them with a digital radiograph to help see the bone levels and the tissue biotype for a better understanding of the tissues’ ability to be displaced. We are also giving the design technician an algorithm equation, called “Finding Z,” which helps to predict the tissue displacement through a mathematical equation. To acquire this equation, please email the author at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Bio
Dean C. Vafiadis, DDS, is a prosthodontist who maintains a cosmetic and implant practice in Manhattan, New York. He is currently the director of the full-mouth rehabilitation CE course at New York University (NYU), and an associate professor of prosthodontics at NYU College of Dentistry. Dr. Vafiadis also is a lecturer and clinical instructor for the Aesthetic Advantage Course in the Rosenthal Institute of Aesthetic and Implant Dentistry at NYU.

References

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