Oral Prosthodontic Rehabilitation
Thomas J. Balshi, DDS, PhD, FACP
Resin bonded splints are also used to stabilize mobile teeth as a result of traumatic injuries. In situations like these, long-term root resorption and continued mobility often result.
The concept of using a resin bonded fixed partial denture, or the resin bonded retaining splint, have many positive aspects and equally as many drawbacks. The advantage of this form of prosthesis is that it is thought to be the conservative form of abutment tooth preparation. Historically, however, it is well noted that frequent maintenance problems are often found with inadequately designed resin bonded fixed partial dentures or splints unless extensive abutment preparation has been accomplished.
Osseointegrated Implants (Tissue Integrated Prosthesis)
Osseointegration is the long-term intimate relationship of ordered living bone fusing to the surface of a load bearing titanium implant. The use of osseointegrated implants today may be considered the most biologically conservative form of replacement for patients who have sustained tooth loss (Fig. 4).
Implant Placement Secondary To Alveolar Ridge Healing
Following severe traumatic loss of numerous teeth and the alveolar ridge, as often seen in high speed impact accidents, the edentulous ridge should usually be allowed to heal initially before fixture (implant) placement. This permits complete mucosal closure over the remaining alveolar bone. Careful treatment planning is necessary to determine precise fixture position, long axis angulation and implant distribution relative to the potential loading forces created by the implant supported prosthesis.
Guided Bone Regeneration Around Implants
Recently some studies have shown that various barrier materials used to enhance osseous generation in areas of voids frequently encountered adjacent to fixtures placed in extraction or root avulsion sockets, have been successful. The use of Goretex has been reported to produce osseous generation around titanium fixtures (implants). Others have reported the effect of resorbable Vicryl mesh as a barrier to inhibit the ingrowth of epithelium around Brånemark fixtures where osseous voids are encountered at the time of initial fixture placement.
Generally sports injuries to the teeth are nonrepetitive and permit the patient to proceed with complete prosthodontic rehabilitation after a normal course of healing. In light of this biologic conservatism, however, one must also consider the professional athlete where the potential for repeated injury does exist.
Removable Prostheses Versus Fixed Implant Supported Prostheses
In some circumstances professional athletes who have lost some of their anterior teeth can benefit greatly from permanent tooth replacement with osseointegrated implants. Such examples might be professional boxers and hockey players who sustain high-impact trauma to the anterior dentition. When such athletes continue in their professional careers, careful consideration should be given to whether or not the use of a fixed implant supported implant is advisable. Because osseointegration by definition is the intimate contact of ordered living bone on the surface of a load carrying implant, without a soft tissue interface, there is absolutely no mobility to the implant fixture. Without a ligament, any impact to the implant supported bridge will convey the same impact to the underlying bone. A sudden blow to the prosthesis can create microfractures to the bone, thereby destroying osseointegration, leading ultimately to the development of fibrous encapsulation.
When professional athletes continue to compete, the clinician may consider the use of osseointegrated implants to support a removable appliance with a resilient interface between prosthetic teeth and the osseointegrated fixtures. Such appliances can be constructed in the form of overdentures with soft tissue liners. Gold clip bars frequently serve as one of the best mechanisms for overdenture retention.
Athletes should be warned that severe impact to the implants can destroy the bone implant interface. Under these circumstances, a secondary appliance should be constructed to prevent implant impact. Mouth guard appliances serve well to protect these implants. During competition, the professional hockey player, the boxer, and other contact sport athletes might do well to remove the implant supported overdenture and replace it with a specially designed mouth guard to avoid implant fractures caused by impact. For these same athletes a nonremovable prosthesis may be constructed to be used during the off season.
Because the Brånemark implant system uses gold set screws to retain the prosthetic components, the bar retainer for the overdenture may be very easily unscrewed and removed at the end of the season and a fixed prosthesis secured with the same fastening screws. At the end of the off season, the athlete may again change from a nonremovable prosthesis to the removable overdenture.
A variety of implant prostheses can be constructed to provide prosthetic replacement for missing dentition as well as supporting alveolar and mucosal tissues. Figure 5 shows two types of prostheses supported by Brånemark osseointegrated implants; one requires prosthetic replacement of lost alveolar tissue (Fig. 5A), the other takes advantage of adequate alveolar and mucosal support (Fix. 5B).
BRANEMARK IMPLANT TREATMENT PROCESS
In order to attain osseointegration, implants must be placed in the alveolar or basal bone and allowed to remain undisturbed for 5 or 6 months in the maxillary (upper) jaw. During this initial healing stage the patient can be temporarily restored with a provisional light weight acrylic removable denture. Alternative forms of temporary prosthesis also include resin bonded teeth or fixed provisional crown and bridge restorations. After the prescribed healing period, a second stage surgery is performed to re-expose the implant and add an extension called the abutment, to which the permanent teeth are ultimately fastened (Fig. 6)
The hardware consists of very special sharp instruments (Fig. 7) and noncontaminated, commercially pure titanium implants (Fig. 8) and abutments (Fig. 9) with a particular surface microarchitecture. These components must be manufactured from a correct bulk metal (CP titanium) and must have an oxide cover with the right characteristics down to the molecular level. Even minor deviations in the titanium oxide can result in the incorrect attachment or arrangement of the early proteins in the wound as it heals.
The software consists of procedures that assure a very gentle tissue handling and careful preparation, recognizing the fact that we are dealing with a wound and that we are creating a defect in the bone that is similar to a fracture. We have to respect that the tissue needs undisturbed healing until the young bone tissue can be made to remodel under functional load (see Fig. 7). next page
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