Written by David M. Gardner, DDS Tuesday, 01 June 2004 00:00
Since the introduction of osseointegrated implants for the replacement of missing or lost teeth, treatment options for partially and fully edentulous patients have expanded exponentially. Removable prostheses are no longer the only available options to restore the edentulous arch. In fact, this approach is no longer the first to be considered. Furthermore, the preparation of teeth that do not otherwise require treatment in order to provide a tooth-borne fixed prosthesis can now be avoided. The ability to replace a tooth or teeth with osseointegrated implants and restore the dentition is now a predictable treatment modality.
Compared to traditional methods of tooth replacement, implant therapy offers increased longevity, improved function, bone preservation, and improved quality of life.1 Ten-year survival surveys of fixed prostheses on natural teeth reveal a survival rate of approximately 75%.2 Success rates for endosseous implants have been shown to be more than 90%.3-4
Due to the predictability of implant dentistry, clinicians can remove a tooth or teeth with an unfavorable long-term prognosis and use osseointegrated implants as a long-term replacement. Consequently, dentists can predictably restore form and function and improve a patients quality of life after the permanent teeth have been lost.
As for all clinical modalities, implant restoration has many variables that must be controlled. Treatment must follow the correct sequence, and all providers must coordinate care in order to restore the patient to optimum oral health. The case report presented in this article demonstrates the sequence of treatment that was followed in order to achieve a predictable and desirable outcome.
The steps taken to reconstruct the hopeless maxilla through the use of endosseous implants will be demonstrated. Variables were controlled through proper diagnosis, treatment planning, and a presurgical phase that utilized tools such as a CT scan and radiographic/surgical template. The surgical phase was simplified as a result of appropriate planning. The prosthetic phase was uneventful due to utilization of techniques to ensure a passively fitting prosthesis. The final restoration was developed using principles such as progressive loading and establishment of a proper occlusal scheme. Finally, a staged approach was used to provide a fixed prosthesis throughout the course of treatment. In addition, this treatment plan allowed the patient to meet his financial responsibilities over a longer period of time. A harmonious and predictable outcome was accomplished.
A 59-year-old male presented with the chief complaint of "I am not happy with my bridgework. What can I do?"
His medical history was carefully reviewed and was unremarkable. A comprehensive oral evaluation, including appropriate radiographs, was performed. The patient exhibited pathology throughout his dentition that included caries, moderate to severe periodontal disease, and occlusal disharmony.
|Figure 1. Preoperative radiograph of maxillary right quadrant.|
|Figure 2. Pre-operative radiograph of anterior teeth.|
|Figure 3. Preoperative radiograph of maxillary left quadrant.|
Examination of the maxilla determined that most of the patients teeth had a hopeless long-term prognosis. In the maxillary right sextant, a fixed partial denture (FPD) was present from teeth Nos. 3 to 5, and both abutments exhibited periapical and periodontal pathology. The right cuspid demonstrated external root resorption (Figure 1). The teeth in the anterior sextant exhibited severe caries, mobility, and periodontal disease (Figure 2). The maxillary left posterior sextant was compromised in that a FPD from teeth Nos. 11 to 13 exhibited moderate bone loss, and both abutment teeth were nonvital. In addition, tooth No. 14 was not restorable (Figure 3).
A treatment sequence for the maxillary arch was planned
The patient expressed the opinion that a fixed prosthesis was preferred, and sought a functional restoration that was comfortable, long-lasting, and aesthetically pleasing.
After carefully reviewing the examination findings and considering the patients expectations, it was determined that implants would be used to restore the dentition.
Implant-supported prostheses provide distinct advantages over removable, soft-tissue-borne restorations.1
These advantages include the following: maintenance of bone; maintenance of vertical dimension; improved psychological and emotional response; increased stability and retention; improved function of the prostheses; increased survival time of restorations (endosseous implants have proven to be predictable, exhibiting 10-year success rates of more than 90%4); and improved phonetics.
A staged approach to the reconstruction was selected in order to provide a fixed prosthesis throughout the course of active treatment.
|Figure 4. Panorex following strategic extractions.|
Following periodontal therapy, all hopeless teeth were extracted. These edentulous areas would serve as the regions where implants would be placed to retain the final prosthesis. The remaining teeth would serve as abutments for a fixed provisional prosthesis (Figure 4).
|Figure 5. Tooth-supported maxillary provisional FPD.|
Following the extractions, a tooth-borne provisional prosthesis was inserted utilizing the remaining dentition (Figure 5). The importance of the provisional prosthesis cannot be overstated. It serves to evaluate an acceptable vertical dimension of occlusion (VDO) and assess aesthetics, phonetics, and lip support required of the final restoration. An acceptable provisional restoration also aids in fabricating a diagnostic template for a computed axial tomogram (CT) scan of the maxilla.
|Figure 6. Treatment plan aided by ICT.|
The diagnostic template enables the clinician to (1) incorporate a 3-dimensional aspect into the treatment plan for the final prosthetic result; (2) evaluate the patients anatomy relative to the proposed implant sites, aesthetics, and occlusion; and (3) record and transfer these findings to the patient at the time of surgery.5 A CT scan of the maxilla was performed with interactive computed tomography (ICT) to develop an implant treatment plan (Figure 6). ICT determines bone quality at the prospective implant sites, and the number, size, and position of the implants are established prior to stage I surgery.6
|Figure 7. Surgical stent prior to stage I surgery.|
|Figure 8. Radiograph following stage I.|
|Figure 9. Radiograph of implant. Note halo of graft material from osteotome procedure.|
Conversion of the radiographic template into a surgical stent was accomplished by utilizing the information provided by the radiographic examination, then transferring this information to a template that would be used during surgery. This process provided a guide for direction, angulation, length, and width of implants (Figure 7). Six root-form implants were placed in the maxilla at sites 3, 6, 8, 9, 12, and 14 (Ti-unite, Branemark). The surgery was uneventful, and there was a need to augment the most posterior implant sites bilaterally (as a result of limited alveolar bone inferior to the sinus floor). An osteotome sinus augmentation was performed to increase the height of available bone (Figures 8 and 9).7 The fixtures were placed at the time of augmentation, thereby reducing the length of time until stage II surgery. This approach to sinus augmentation is less invasive than the lateral window approach.
An osteotomy was performed just inferior to the sinus floor. Using osteotomes, the floor of the sinus was infractured, and the bone graft material (Bio-Oss, Osteohealth) was moved both superiorly and laterally, thereby augmenting the sinus floor. This procedure has been described by Summers.7 Cover screws were placed on all of the implants, surgical sites were closed, and 6 months were allowed for osseointegration.
Following this healing phase, the implants were uncovered and healing abutments placed. The fixed provisional was relieved in order to allow complete seating over healing abutments.
Three weeks after the stage II surgery, a fixture/implant impression was taken utilizing direct implant transfer copings that were screwed onto each implant and confirmed radiographically to check for proper seating. Implant positions and angulations were recorded on the cast. Using a template (vacuform) of the provisional prosthesis (with occlusal areas removed), abutment selection was performed on the cast using guide pins to determine implant angulation (Figure 10).
|Figure 11. Abutment seating jig on cast.||Figure 12. Abutment seating jig correctly positioned on implant platforms.|
|Figure 13. Verification jig.|
Angled abutments were selected for 3 of the implants to create parallelism of all implants. Due to the internal geometry of angulated abutments, they can be placed at variable positions around the hexed implant platform. It is important to transfer the abutment positions accurately from the cast to the mouth. An abutment seating/positioning jig was fabricated to assist with this transfer. Figures 11 and 12 illustrate this process.
The fabrication of a verification jig is the most important step to ensure that the final prosthesis will be passive.8 Stress and strain need to be within a physiologic range, and the implants must remain undisturbed when the prosthesis is secured in place. Because there is no space between the coping and implant abutment, the casting must fit accurately and passively before the screw is completely tightened (Figure 13).9
Vertical studies were performed with wax rims to determine the correct VDO. Master casts were mounted on a semi-adjustable articulator, and a new provisional restoration that includes both implants and teeth was fabricated.
For several weeks, the provisional restoration remained in place, progressively loading the implants. After this period, the remaining teeth were extracted. By incorporating variables such as time, diet, occlusion, prosthesis design, and occlusal materials, progressive loading was accomplished. Progressive loading of implants has been shown to improve implant success, regardless of implant design, coating, or length.10,11
|Figure 14. Abutment level impression.||Figure 15. Metal framework on articulator.|
|Figure 16. Framework try-in.||Figure 17. Radiographic confirmation of passive fit.|
Following the final impression, master casts were articulated, and the framework was waxed, cast, and verified (Figures 14 and 15). The patient returned for the framework try-in, which was confirmed clinically and radiographically (Figures 16 and 17).
Development of the Occlusal Scheme
|Figure 18. Final prosthesis, occlusal view.|
The primary concern when developing the occlusion was minimizing implant load. This was accomplished with the use of therapeutic biomechanics.12 Reduction of implant load may be achieved using several approaches, including the use of angulated abutments to create parallelism, reduction of posterior cusp inclination to reduce torque, development of widened central fossae to avoid interferences during excursive movements, and development of a cuspid protected occlusion. The use of these approaches when designing occlusal contacts will help to minimize stresses on the fixtures (Figure 18).
|Figure 19. Insertion of implant-supported FPD.||Figure 20. Implant-supported FPD upon insertion.|
The prosthesis was inserted and the occlusion was checked for interferences (Figures 19 and 20). All retaining screws were torqued to 20 ncm. Following monitoring of the prosthesis for screw loosening, patient comfort, and occlusal stability, the screw access holes were covered with composite and the patient was placed on a recall of 3 months for the first year and 6 months thereafter.
This case report reviews an approach to restoring and rehabilitating the maxillary arch of a patient with advanced dental disease. A staged approach was used to reconstruct the patients arch with dental implants. A thorough treatment plan, meticulous attention to detail, and careful control of variables helped achieve a successful outcome. The treatment plan provided the patient with a fixed prosthesis throughout the course of treatment. The length of treatment for this case was approximately 28 months.
The author would like to thank Alter Smiles Dental Studios in New Hyde Park, NY, which completed all laboratory work.
1. Misch CE. Contemporary Implant Dentistry. 2nd ed. St Louis, Mo: Mosby; 1999:9-11.
2. Walton JN, Gardner FM, Agar JR. A survey of crown and fixed partial denture failures: length of service and reasons for replacement. J Prosthet Dent. 1986;56:416-421.
3. Adell R. Clinical results of osseointegrated implants supporting fixed prostheses in edentulous jaws. J Prosthet Dent. 1983;50:251-254.
4. Albrektsson T, Jansson T, Lekholm U. Osseointegrated dental implants. Dent Clin North Am. 1986;30:151-174.
5. Monson ML. Diagnostic and surgical guides for placement of dental implants. J Oral Maxillofac Surg. 1994;52:642-645.
6. Misch CE. Contemporary Implant Dentistry. 2nd ed. St Louis, Mo: Mosby; 1999:80.
7. Summers RB. The osteotome technique: Part 3—Less invasive methods of elevating the sinus floor. Compendium. 1994;15:698-708.
8. Knudson RC, Williams EO, Kemple KP. Implant transfer coping verification jig. J Prosthet Dent. 1989;61:601-602.
9. Misch CE. Principles for screw-retained prostheses. In: Misch CE. Contemporary Implant Dentistry. 2nd ed. St Louis, Mo: Mosby; 1999:669-685.
10. Misch CE. Density of bone: effect on treatment plans, surgical approach, healing, and progressive bone loading. Int J Oral Implantol. 1990;6:23-31.
11. Rotter BE, Blackwell R, Dalton G. Testing progressive loading of endosteal implants with Periotest: a pilot study. Implant Dent. 1996;5:28-32.
12. Weinberg LA. Reduction of implant loading with therapeutic biomechanics. J Impl Dent. 1998;7:277-285.
Dr. Gardner completed a general practice residency and a 2-year fellowship in advanced prosthetics and implant dentistry at North Shore University Hospital (NSUH). He remains on staff at NSUH, where he teaches in the department of implant dentistry, and maintains a private practice in Roslyn Heights, NY.
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