October 1, 2004
by Mario Cabianca, DDS
Implants are an exciting field of restorative dentistry that offers many interesting and demanding challenges. Despite our most carefully laid out plans and efforts, situations arise which require re-evaluation and retreatment. If one becomes involved in surgical placement of dental implants one should also understand and perform the surgical correction of these complications. Complications may result from smoking, bruxism, poor oral hygiene and under engineering of the case. This discussion deals with the sequence of events involving failing implants,1 their replacement and reducing sources of complication.
Patient B.P. was involved in a workplace accident in 1994, which resulted in massive trauma to his lower right mandible. The consequence was loss of teeth from #32 to #45 inclusive as well as supporting alveolar bone. Following initial trauma care the restorative phase involving placement of five dental implants and a non- removable hybrid prosthesis was completed in October 1996. In May 1998 the patient first presented to my office and examination of his reconstruction revealed initial signs of crestal bone loss around the #45 implant. The patient was advised of the findings and declined removal of the prosthesis and treatment of the affected area. Following recare visits were met with similar responses. Finally in July 2000 the patient agreed to consider removal of the appliance and treatment of the affected sites. The patient was advised that successful treatment of the area required bone grafting and this would be influenced by his smoking habit. The patient understood this and began a smoking cessation program with his physician. In the year 2002 the patient began removal, reconstruction and replacement therapy. The panoramic and periapical radiographs (May ’98 and May ’02) illustrate the progression of the problem to this time (Figs. 1A-D).
After the prosthesis was removed, the implant sites were exposed with a midcrestal incision and a full periosteum reflection. Degranulation of the implant sites showed exudate and crestal bone loss involving over 50% of the 3 most distal implants (Fig. 2). These three failed implants were cored out with a 4.0 mm trephine bur and the flap was then closed with Vicryl (Ethicon, Somerville, NJ) sutures. The sutures were removed two weeks later. The tissue was allowed to heal another three weeks. This allowed for infection to resolve and healing by secondary intention of the former implant sites.
Re-entry of the area involved another midcrestal incision and full reflection (Fig. 3) of the periosteum. The flaps were tied back with 2-0 silk to allow ease of visual access. The former implant sites were degranulated of tissue and the remaining two implants were detoxified with supersaturated solution of citric acid.2 The bony defects were perforated to assist with the regional acceleratory phenomenon (RAP)3-5 (Fig. 4). The deficiencies were grafted with a 25/75 mixture of OsteograftN-300 (Ceramed, Lakewood, CO) and Grafton( (Osteotech, Eatontown, NJ) putty (Fig. 5). This mixture filled the sites but was not densely compacted. Overfill would delay blood vessel ingrowth. The crestal surfaces were then covered with Bioguide (Osteohealth Co. Shirley, NY) membranes to prevent soft tissue in growth of the grafted areas (Figs. 6A,B). The nonrigid nature of this membrane allowed it to be placed in situ without need for fixation.
To obtain tension free primary closure, the buccal full thickness flap periosteum was scored using horizontal releasing incisions and spreading by Metzenbaum scissors after insertion into the tissue. The flap was approximated using Gortex (Gore, Flagstaff, AZ) sutures (Fig. 7). These sutures prevent wicking of bacteria into the graft as well as maintain tensile strength. One cannot overly emphasize the importance of establishing and maintaining primary closure following bone-grafting procedures.6 The sutures were removed two weeks postoperative. The patient agreed to refrain from wearing a prosthesis over this area thus facilitating undisturbed healing (Fig 8).
Surgical and radiographic templates (Fig. 9) were fabricated7 based on a diagnostic wax up of the proposed future prosthesis. After five months, a CT scan8 (Fig. 10) of the grafted area was obtained. The scan revealed a lingual concavity in the posterior area of the mandible, which would necessitate a more buccal placement of any dental implants.
B.P.’s next appointment was for implant replacement (Fig. 11). A full thickness flap was reflected revealing a well-healed ridge of Division A, Type II bone9 (Fig. 12). The surgical template (Fig. 13) was used to guide placement (Fig. 14) and four 4.0mm diameter Maestro (Biohorizons, Birmingham, AL) implants were inserted. The cover screws (Fig. 15) were placed and the flap was closed to obtain primary closure using 4-0 Vicryl sutures (Fig. 16). A postoperative panoramic film was obtained (Fig. 17). The sutures were removed two weeks later. Oral hygiene instructions were reviewed. Four months healing was followed by uncovery of the implants and six permucosal extensions were placed. The patient returned in four weeks for a final impression.
After the soft tissue had healed, the patient returned for the final impression. Six impression pins were attached and a radiograph was taken to confirm seating on the implants that were subgingival. A custom tray with polyvinylsiloxane was used for the impression and sent to the lab for fabrication of the fixed bridge prosthesis. In addition, a facebow record was taken. Four custom and two stock abutments (Figs. 18A,B) were fabricated and milled to support a seven-unit porcelain fused to metal bridge (Fig. 19). The abutments were connected (Figs. 20A,B) and a radiograph (Fig. 21) was taken to confirm seating as necessary. The abutments were torqued down to 30N.cm with the assistance of a hemostat to provide antirotational force. The abutment screws were covered with cotton and Fermit-N (Vivadent, Liechtenstein). The inside of the prosthesis was lined with petroleum jelly and then cemented using NeoTemp (Waterpik, Fort Collins, CO) (Figs. 22A,B). A panoramic film (Fig. 23) was taken upon completion of treatment. Oral hygiene instructions were reviewed again and occlusion was checked. The patient was pleased with the final outcome (Fig. 24). Total time for retreatment was 19 months.
The methods, time and cost of retreatment are often greater than initial treatment. It is imperative that both the dentist and patient understand and eliminate as many factors as possible, which may contribute to failure prior to beginning treatment. Despite our best efforts failures will occur, but our understanding of the causes will enable us to reduce these incidents.
Dr. Cabianca is a Diplomate of the International Congress of Oral Implantologists and an Associate Fellow of the American Academy of Implant Dentistry. He maintains a private practice in Trail, BC.
Oral Health welcomes this original article.
Acknowledgement: Thank you to Robin Ybema for her assistance in preparing this manuscript.
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