The International Journal of Oral & Maxillofacial Implants, 01/1992

Since the introduction of osseointegrated titanium implants for bone-anchored facial and dental prostheses, an increasing number of irradiated patients are being treated with this technique. Although the number of patients who have had titanium implants after irradiation is limited, available statistics point to a tendency of a higher implant loss frequency as compared with nonirradiated patients. This review discusses factors behind deleterious tissue effects and implant failures from irradiation and points to possibilities to improve the surgical outcome with special reference to hyperbaric oxygen therapy. Keywords: hyperbaric oxygen, irradiation, osseointegration, titanium implants

Metal fatigue failure of the gold screw used to retain a fixed prosthesis to Branemark osseointegrated fixtures/abutments has been analyzed theoretically. Mechanical engineering principles show the importance of appropriate preload being applied through the gold screw to the gold cylinder and abutment. The significance of the screw design and necessity of applying the correct torque to achieve a long fatigue life for the screw are also described. The consequence of misalignment of a gold cylinder to an abutment is discussed. Keywords: Brånemark System, metal fatigue, osseointegrated implants, preload, stress, torque

Because of reported prosthodontic failures, alternative implant abutments and screws with suggested strength superiority have been manufactured. However, little quantitative data are available to support these claims. This study compared the force necessary to cause failure in many of the more commonly used implant and abutment combinations. An 18-mm cantilever test prosthesis was constructed for each system and loaded on an MTS machine until failure occurred (n = 5 for each sample). The mean failure forces ranged from 1.22 to 17.23 kg. The failure force and location of failure for each individual system are reported. Keywords: dental implants, failure, prosthetic components

Ninety-six partially edentulous maxillae and mandibles were consecutively treated with 127 freestanding fixed prostheses supported by 354 implants. The patients were followed for 1 year and the overall success rate was 98.6% for the examined implants. None of the inserted prostheses was lost during the observation period. The most commonly reported problems during the first year of function were related to loose gold screws and esthetic complaints, complications that were easily resolved. Furthermore, the total number of complications was low and was less than has been reported for routine full-arch fixed prostheses. Keywords: Brånemark implants, complications, failures, fixed partial prostheses

The results of 10 fixture placement operations with transpositioning of the inferior alveolar nerve are presented. Nerve transpositioning increased the operating time, but with experience this time should be reduced. Neurosensory dysfunction of the inferior alveolar nerve was found in 7 of 10 operated sites 1 week after surgery. Six months postoperatively, altered sensation was still present in 2 patients. Nerve function was normal in all patients 1 year postoperatively. The stability of fixtures was satisfactory throughout the examination period and the procedure should prove useful in treatment of the resorbed mandible posterior to the mental foramina. Keywords: fixture, implant, inferior alveolar nerve, nerve transpositioning

Sixty-four edentulous patients with severe conventional denture problems who had been treated with 218 one-stage titanium plasma sprayed (TPS) screw implants and new overdentures were clinically evaluated and questioned on their experiences with treatment up to 6 years after implant insertion. The results demonstrated that only seven of the implants had failed during this period, resulting in a success rate of 97%. Most of the patients (95%) were satisfied with their new overdentures, and almost all patients (98%) found that their new dentures fit comfortably. Only 3% of the patients treated would not recommend that others undergo similar treatment. Keywords: dental implants, denture satisfaction, overdentures

Fixed-removable implant prostheses provide solutions for some of the problems associated with implant dentistry, especially in the maxilla. The technique for using electrical discharge machining to create a precise passive fit between the substructure bar and the removable suprastructure is presented. The advantages, disadvantages, and complications associated with this type of prosthesis are discussed. Keywords: electrical discharge machining (spark erosion), fixed-removable bar-overdenture prosthesis

The removal torques for screw-shaped pure titanium implants inserted in rabbit tibia and the femoral part of the knee joint and the tissue response to these implants, as quantitated with light microscopic morphometry on ground sections, were compared after 6 weeks, 3 months, and 6 months. The bone surrounding the femoral intra-articular implants was mostly cancellous, while cortical bone was formed around the tibial implants. The torque needed to remove the intra-articular implants increased with time, but there was no such increase for the tibial implants. At 6 weeks, significantly less torque was needed to remove the intra-articular implants in spite of the fact that significantly more bone was found in the threads of these implants as compared with the tibial implants. When calculating the amount of bone in threads situated in the cortical and subchondral passage, more was found in the threads of the tibial implants, which corresponded to the higher removal torque. Additional light microscopic observations on implants unscrewed after 12 months in rabbit tibia indicated that rupture occurred between the implant surface and calcified bone. Findings indicate that the resistance to unscrewing is dependent on the amount of compact bone surrounding a titanium implant. Keywords: cancellous bone, cortical bone, knee joint, morphometry, removal torque, titanium implants

Hydroxyapatite (HA) and tricalcium phosphate (TCP) are useful for grafting and augmentation of bone tissue. In this study, conventional and histochemical transmission electron microscopy were used to study osteogenic events at the interface between the implanted materials and adjacent tissue from 1 to 4 weeks postoperatively. The microscopic results indicated that TCP was resorbed more rapidly than HA after implantation, with a notable breakdown of material and replacement by mesenchymal cells with ultrastructural features resembling osteoprogenitor cells and collagen up to 4 weeks postoperatively. Alkaline phosphatase and acid phosphatase reactivity in the tissues helped to identify and differentiate the histologic differences observed between HA and TCP. Keywords: bone substitute, hydroxyapatite, osteogenesis, transmission electron microscopy, tricalcium phosphate

A new self-tapping Brånemark implant designed for denser bone qualities was evaluated with regard to insertion technique, complications, marginal bone remodeling, and survival rate. Thirty patients, representing 21 mandibles and 9 maxillae, participated in the study. In each patient both standard and self-tapping implants were placed, and a total of 179 implants, 88 self-tapping and 91 standard, were inserted. Thirteen of 62 mandibular self-tapping implants reached their correct positions only after using the screw tap or the cylinder wrench for manual insertion. No such problems were noted when using standard fixtures after bone pre-tapping. In the maxillae, neither of the two implant designs presented any problems. One standard and one self-tapping fixture failed to osseointegrate. Radiolucencies were seen in the bone around the apical portion of two fixtures, one of each design. The mean marginal bone resorption after 1 year of follow-up was 0.5 to 0.6 mm for the two fixture types. Keywords: Brånemark implant, self-tapping fixture

Advanced mandibular atrophy is a serious surgical reconstruction challenge. Previous experience with an inferior border approach has been favorable. Predictably successful osseointegrated implants ultimately allow loading of the healed grafts. The technique described uses a freeze-dried, gamma-irradiated cadaver mandible packed with autogenous iliac crest bone. An extraoral approach allows augmentation without disrupting use of an intraoral prosthesis during healing. The incidence of infection and resorption can be reduced. Fewer problems with neurosensory disturbances common with some of the superior border, or sandwich osteotomy, grafting techniques were experienced. The use of implants to ultimately load the bone should result in less resorption than in those techniques using a conventional removable prosthesis. Keywords: advanced mandibular atrophy, composite cadaver mandibular autogenous bone, extraoral approach, inferior border graft

The chemical composition and topography of an implant surface determine the human immunologic system response. This study compared the surfaces of 13 Brånemark oral implants, 11 that came from retrieved specimens which failed initially or did not osseointegrate and 2 that were never implanted (controls). The period of implantation in human jaws varied between 3 and 20 months. After cleaning and sterilization, the topography, surface chemical composition, and thickness of the oxide layer were studied. The results obtained with scanning electron microscopy did not show any significant topographic differences among the specimens. X-ray spectrographic microanalysis showed very similar composition (titanium and amounts less than 0.5% of other elements) in the outermost layer of the analyzed specimens. The Auger spectroscope revealed considerable percentage differences in the amount of carbon and silicon in the last monolayers, which could be attributed to handling or to an inadequate cleaning process. This places the retrieved specimens out of the acceptable statistical limits of contamination by introducing a factor of doubt for long-term prognosis in the hypothetical situation of their re-use. Keywords: failed implants, microanalysis, osseointegration, surfaces

A new prosthetic concept, today available under the name CeraOne™, for single tooth replacement with the Brånemark system is described. This concept is characterized by a new design of the prefabricated components. A mechanical torque driver is used together with a gold screw and a special counter-torque device to ensure that the screw is tightened in an optimal manner to resist screw loosening and only transmit minor stress to the fixture interface. Another characteristic is the use of a prefabricated cap of sintered aluminum oxide as the basis for the ceramic crown. The crown is cemented to provide better esthetic possibilities even in situations of somewhat unfavorable fixture placement. Keywords: abutment, single tooth implant, titanium

The treatment of a patient with a major defect in the anterior region of the mandible is described. A large part of the anterior dental arch and underlying mandibular bone was involved in the defect. A removable partial denture supported by implants as well as residual teeth was used to restore the defect. Compared with a traditional removable partial denture, which was used by the patient for several years as an interim prosthesis, the application of implants resulted in improved functional comfort and stability. Keywords: anterior defect, implants, removable partial denture