The International Journal of Oral & Maxillofacial Implants, 06/1994

One hundred fifty-nine partially edentulous patients, ranging in age from 17 to 70 years, were treated with the Brånemark implant system at nine centers throughout the world. The patients were followed for 5 years in a prospective study focusing on implant success and prosthesis stability. Plaque and gingival indexes, as well as probing depths, were recorded around teeth and implants. The marginal bone level at implants was determined from intraoral radiographs. The stomatognathic function and possible complications were also reported. Initially, 558 implants were placed in 68 maxillae and 91 mandibles of Applegate-Kennedy classes I, II, and IV. Of the placed implants, 528 were reexposed at the abutment operation, whereafter 521 were loaded with 197 freestanding fixed prosthetic restorations in a total of 154 patients. During the follow-up period, a total of 27 patients dropped out or were excluded because of nonconformity with the protocol. This meant that 116 implants (80 withdrawn [14%] and 36 failed [6%], and 32 fixed prostheses [16%]) were not reexamined at the final follow-up visit. Based on the remaining implants, the cumulative implant success rates were 92% and 94% for maxillae and mandibles, respectively, and the corresponding prosthesis stability was 94%. Plaque and gingivitis indexes showed a similar pattern of good health around both natural teeth and titanium abutments. The marginal bone loss during the 5-year period did not exceed 1 mm as a mean for all implants analyzed. During the follow-up period, few complications were reported, the most frequent being resin fractures and loose gold screws. The outcome of the study indicated that safe and predictable treatment results can be obtained for 5 years in partially edentulous jaws treated with the Brånemark implant technique. Keywords: Brånemark system, oral, osseointegration, partial edentulism, titanium implants

Eight nonsubmerged titanium implant screws were placed in monkey maxillary bone, restored 1 month after surgery, and kept under occlusal forces for 14 months. Block biopsy specimens were processed for light and electron microscopy. In all samples, the implant surface appeared integrated to both hard and soft peri-implant tissues. The supracrestal peri-implant connective tissue included densely packed collagen fibers free of inflammatory cells. The fibers originated from the alveolar bone crest, radicular cement of adjacent teeth, and gingival mucosa, and migrated towards the implant neck. Near to the implant surface, the fibers merged together and constituted a circular ligament. Thin histologic sections of the circular ligament showed collagen fibrils with diameters similar to those of the ligaments of natural teeth. Moreover, histochemical observations disclosed that the fibrils near the metal surface were immersed in a matrix containing highly sulfated proteoglycans. Keywords: gingival connective tissue, histochemistry, SEM, TEM, titanium implants

The use of guided bone regeneration to fill large bone voids in the mandible created through en bloc resection and chronic granulation in three primates was examined. In each of three animals, en bloc resections of implants and surrounding bone were done bilaterally (10 × 8 mm and 16 × 8 mm). Tissues were allowed to heal in a chronic state (for 6 months). A reinforced expanded polytetrafluorethylene (e-PTFE) membrane was then surgically placed over each defect site to be followed for 1 year postsurgically. Two of the six membranes became infected during the first month and were removed. The remaining four membranes were removed en bloc after 1 year. Bone regeneration (greater than 90% of the defect) was observed clinically, and subtraction radiology demonstrated bone gain of between 544 and 733 mg. Histomorphometry after fluorescent labeling demonstrated a mean growth rate of 2.77 µm/wk for all sites measured, and a decrease in the number of osteons from the new bone at the crest to the mature bone at the base of the original defect. This study gives evidence that substantial quantities of new bone can be produced in atrophic mandibles and that this regenerated bone exhibits normal maturation dynamics. Keywords: guided bone regeneration, mandibular defects, monkeys

A study of 125 titanium implants placed in irradiated bone is reported. Eighty-eight implants were placed in nonirradiated bone and 45 implants were placed in irradiated bone after hyperbaric oxygen treatment (HBO) was undertaken in 68 patients. There was an increased loss of implants in irradiated bone (38.4%) compared to nonirradiated bone (17%). None of the implants placed after HBO was lost. Low irradiation doses did not prevent implant losses. Longer intervals from the time of irradiation to implant surgery resulted in more implant losses. The highest implant losses were seen in the periorbital bone. Three-millimeter-long implants showed increased loss compared to 4-mm or longer implants. Retention of the prosthesis with bar and clips resulted in reduced implant losses, compared to the use of individual magnets or a combination of magnets and clips. Using a grading system for cutaneous reactions, irradiated skin showed increased adverse reactions during the first year after implant surgery. Adjunctive treatment with HBO reduced adverse skin reactions. Keywords: hyperbaric oxygen treatment, irradiation, osseointegration, prosthetic reconstruction, titanium implants

Metal-ceramic, all-ceramic, and porcelain crowns, as well as complete implant posts and alumina copings alone, were loaded in an Instron universal testing machine. Load was applied until fracture or major deformation of tested objects was observed. Based on these results, theoretical calculations were made for different clinical situations. The maximum load that the single crown could resist without giving rise to any damage on the superstructure was calculated. The conclusion was that the abutment screw is the weakest link, since the failure loads of the gold screws are lower than the failure loads of the crowns, with the exception of porcelain crowns. Keywords: alumina, bending moment, ceramic crown, occlusal force, single-tooth implant

The aim of this study was to determine by selective culturing methods whether implants and natural teeth in the periodontally healthy mouth are colonized by the same oral bacteria. In 16 partially edentulous patients, one or two titanium implants, and respectively, one or two sites from the natural teeth, were examined (total of 58 sites). Periodontal parameters were assessed, and supragingival and subgingival plaque was examined for selective pathogenic bacteria. No significant difference was found between the subgingival flora around the teeth as compared to the implant flora. However, the frequency of occurrence of Actinobacillus actinomycetemcomitans (Aa) and Actinomyces viscosus in the supragingival plaque was higher for teeth compared to implants (92% vs 57% and 90% vs 73%, respectively). The amount of Aa was significantly higher around teeth than around implants (mean Ln of 6.69 vs 3.25). These data suggest that while the composition of the subgingival flora appears to be similar around healthy teeth and implants, composition of the supragingival plaque may differ. Keywords: dental implants, gingival plaque, microbiology

Significant atrophy of the edentulous maxilla was treated with one of three bone grafting techniques: (1) onlay augmentation of the alveolar crest; (2) inlay grafting of the floors of the nose and maxillary sinuses following a Le Fort I osteotomy; and (3) inlay grafting of the maxillary sinus. Autogeneic iliac composite bone blocks were used with immediate placement of Brånemark implants. The first 10 consecutively treated patients for each treatment regime were followed between 33 and 95 months. Sixty-eight percent to 86% (onlay 83%, Le Fort I 68%, inlay 86%) of the 124 total implants placed into the bone graft were well integrated at the latest follow-up. However, although the primary intention was to provide all patients with a fixed prosthesis, five patients received a removable overdenture because of a reduced number of existing implants. Also, two patients in the Le Fort I group received removable overdentures due to a remaining large sagittal discrepancy between the jaws. In general, patients had good intraoral function; eight patients had minor phonetic problems, and three were not fully satisfied with the esthetic result. The specific indication for each of the techniques described is discussed and constitutes valuable means for treatment of severely atrophic maxillae. Keywords: atrophy of maxilla, bone grafting, Brånemark implants, endosseous implants

In this study, the soft tissue around 23 percutaneous Brånemark titanium implants was studied using light microscopic morphometry. The duration of the skin penetration varied between 4 and 98 months. The results show that phagocytic and immunocompetent cells (lymphocytes, polymorphonuclear granulocytes, plasma cells, and macrophages) were present in biopsies from patients with irritated as well as nonirritated skin around the implants. The concentration of inflammatory cells was higher in the tissue close to the implant and in this region particularly just beneath the epithelium. The concentration of inflammatory cells in irritated skin did not differ statistically from nonirritated skin. This was probably related to the fact that the grade of skin irritation generally was low in the material and to the relatively small amount of material investigated. The present observations suggest that a cellular barrier of phagocytic and immunocompetent cells may be operative around percutaneous titanium implants. The mechanisms for the clinically manifest irritation and reinforced cellular barrier function are not known but may be related to both the implant per se and to invasion by exogenous agents. Keywords: histology, inflammation, percutaneous implant, titanium

In this study, cylindrical titanium plasma-sprayed dell implants were divided into three groups and implanted in rabbit femurs as: (1) control, a conventional method recommended by IMZ, (2) experimental I, artificial bone defects were formed prior to implantation, and (3) experimental II, porous hydroxyapatite (HA) granules were grafted into bone defects after implantation. The rabbits were sacrificed after 8 weeks and specimens were prepared and immediately pushout-tested for shear-bond strength of the bone-implant interface. Each group was examined histologically. The results showed that mean shear strength of the bone-implant interface in the control group was 2.61 ± 0.68 MPa, in experimental I was 0.66 ± 0.32 MPa, and in experimental II was 2.28 ± 0.60 MPa. There was a significant difference between the control and experimental I and between experimental I and experimental II, but no statistically significant difference between the control and experimental II. Cortical bone formation was more advanced than cancellous bone around the implants. In the histologic study of nondecalcified specimens, control and experimental II groups showed about 55% bone or osteoid tissue in contact with titanium at the bone-implant interface. In the histologic review of undecalcified specimens, the experimental I group demonstrated about 45% bone or osteoid tissue in contact with titanium at the interface, and partial bony defects were seen in the coronal zone. In the experimental II group, direct bony contact to HA granules and infiltration of a few giant cells were seen. When porous HA granules were grafted in the randomly made bone defects around the titanium implants, bone growth was more active and implant-bone bond strength was greater than when only the implants were placed. Keywords: bone-implant interface, hydroxyapatite, IMZ implants, shear-bond strength

The opportunity to connect implants and teeth has been discussed in the literature. A comparative retrospective study was performed to evaluate the prosthetic results obtained in our clinical experience with 31 free-standing and 30 tooth-connected posterior IMZ implant-supported fixed partial dentures. Complications such as the loosening and fracture of fixation screws and abutments, ceramic fractures, and natural tooth migration were observed. A significant difference in the incidence and types of such complications in the two groups was found: problems occurred more frequently and in a different pattern with the free-standing compared to tooth connected restorations. Possible explanations for this dissimilar behavior are discussed. Keywords: complications, free-standing, implant-supported fixed partial dentures, intramobile elements, proprioception, tooth-connected

This study investigated the tactile threshold of peri-implant tissues to clarify the pressure-recognition mechanism for static loads in patients with osseointegrated implants. A measuring device composed of a loading apparatus with electrical strain meters, a hand switch, and a thermal-pen recorder was used. Experiments were performed under different conditions involving loading direction and participation of surrounding tissues. This study confirmed that patients with osseointegrated implants lacked the pressure-recognition mechanism for very small loads, but possessed the mechanism for larger loads. This mechanism is thought to depend on the mechanoreceptors present in muscles, tendons, and the temporomandibular joints. Keywords: osseointegrated implant, peri-implant tissues, pressure-recognition mechanism, tactile threshold

In 1989 the Dental School at the University of Texas Health Science Center at San Antonio originated a study to determine the feasibility of teaching clinical implant therapy to predoctoral students. Students in this selective program performed all of the implant surgery, prosthodontics, and maintenance therapy on assigned edentulous and partially edentulous patients. In 1992 another implant selective was added that enabled other students to become involved in the prosthodontic and maintenance phases of implant therapy. During the first 4 years of this program, dental students placed 120 implants in 74 patients with no failures. This program will continue and expand. Keywords: dental implants, dental students, education, implantology, problem-based learning