U Lekholm’s research while affiliated with University of Gothenburg and other places

The present paper reports on the result of the use of osseointegrated titanium fixtures and teeth as combined abutments for fixed-bridge restorations in 10 partially dentate patients. In these patients, the remaining teeth were too few or too unfavourably distributed in the jaws to serve as sole abutments for fixed bridgework. Titanium fixtures ad modum Brånemark were therefore implanted in suitable positions and used as abutments in combination with the remaining teeth. Evaluations at periods of 6 to 30 months postoperatively revealed good clinical results. Some tissue reactions, however, were also observed, indicating the presence of certain clinically significant differences in the functional behaviour of tooth abutments and titanium fixture abutments. These reactions and differences are discussed.

The aim of the present study was to evaluate the long-term effect of implants installed in different dental areas in adolescents. The sample consisted of 18 subjects with missing teeth (congenital absence or trauma). The patients were of different chronological ages (between 13 and 17 years) and of different skeletal maturation. In all subjects, the existing permanent teeth were fully erupted. In 15 patients, 29 single implants (using the Brånemark technique) were installed to replace premolars, canines, and upper incisors. In three patients with extensive aplasia, 18 implants were placed in various regions. The patients were followed during a 10-year period, the first four years annually and then every second year. Photographs, study casts, peri-apical radiographs, lateral cephalograms, and body height measurements were recorded at each control. The results show that dental implants are a good treatment option for replacing missing teeth in adolescents, provided that the subject's dental and skeletal development is complete. However, different problems are related to the premolar and the incisor regions, which have to be considered in the total treatment planning. Disadvantages may be related to the upper incisor region, especially for lateral incisors, due to slight continuous eruption of adjacent teeth and craniofacial changes post-adolescence. Periodontal problems may arise, with marginal bone loss around the adjacent teeth and bone loss buccally to the implants. The shorter the distance between the implant and the adjacent teeth, the larger the reduction of marginal bone level. Before placement of the implant sufficient space must be gained in the implant area, and the adjacent teeth uprighted and paralleled, even in the apical area, using non-intrusive movements. In the premolar area, excess space is needed, not only in the mesio-distal, but above all in the bucco-lingual direction. Thus, an infraoccluded lower deciduous molar should be extracted shortly before placement of the implant to avoid reduction of the bucco-lingual bone volume. Oral rehabilitation with implant-supported prosthetic constructions seems to be a good alternative in adolescents with extensive aplasia, provided that craniofacial growth has ceased or is almost complete.

The aim of the present study was to evaluate the soft tissue response to intra-orally exposed and contaminated titanium surfaces (machined, blasted or polished) after being chemically and/or mechanically cleaned. Eight adult Sprague-Dawley rats were used for histomorphometrical and histological analyses. A total of 44 experimental abutments (26 tests and 18 controls) were inserted into abdominal skinpockets of the rats for 6 weeks. No differences regarding the soft tissue response between the different surface characteristics analysed and between test and control could be observed.

Despite good success rates of osseointegrated oral implants, failures do occur. To minimize losses, failure mechanisms should be elucidated. This study sought to describe the morphology of tissues surrounding late failed Brånemark implants in relation to their clinical and radiographic findings to acquire a better understanding of the etiologic factors. Ten failed implants and their surrounding tissues were consecutively retrieved from nine patients after prosthesis placement (late losses). On radiographs, a radiolucent line was visible around nine clinically mobile implants. Tightening of the abutment screw evoked pain at seven mobile implants. Clinically, no other visual inflammatory sign or symptom was manifest. A fistula originated from one stable implant, surrounded on radiographs by a diffuse bone rarefaction. Retrieved implants were electrochemically dissolved. Intact tissue-implant thin (1 micron) and ultrathin (70-80 nm) sections were analyzed with light and transmission electron microscopy. Peri-implant marginal tissues displayed moderate inflammatory infiltrates located adjacent to and beneath the junctional epithelium. One patient affected by oral lichen planus displayed an intense lymphocyte/plasma cell-dominated immune reaction. Deep peri-implant tissues surrounding mobile implants consisted of a dense, fibrous tissue capsule with minimal inflammation. Epithelial downgrowth was observed around four implants. Small areas of nonmineralized bone in contact with the implant were noticed in the apical portion of two implants. One implant was almost entirely colonized by bacterial plaque with the exception of its apical portion, where bone-implant contact was observed. The stable implant was characterized by bone-implant contact. Altogether clinical, radiographic, and histologic findings indicated that two major etiologic factors might have been implicated in the failure process of the investigated implants: excessive occlusal load in relation to the bone-supporting capacity and, in two cases, infection.

To study the bone response around implants placed in tibia of rabbits that supported misfitting superstructures secured with different degrees of preload. Twelve rabbits were provided with two terminal 10-mm and one intermediate 7-mm-long implant in each tibia. After an integration time of about 9 weeks, nine of the animals received one control framework each (n = 9), designed with good fit to all three implants. In the other tibia of these animals, and in both tibias in the remaining three rabbits, test frameworks (n = 15) were connected with a vertical misfit of about 1 mm to the intermediate implant. The intermediate set screws were tightened with a torque ranging from 15 Ncm to 26 Ncm in the different test frameworks. The fascia and skin was then sutured back over the implants. After a loading period of 2 to 3 weeks, the animals were sacrificed, and histomorphometric measurements were made and correlated to the different levels of preload of the central implant. The mean bone-to-metal contact for the three best consecutive threads of the central implant was 40% for both test and control sites (p > .05). Compared to the other regions of the implant thread, less bone-to-metal contact was found at the tip of the test implant threads in the low preload group (p < .05). However, the same relation was not observed in the high preload group. A significant correlation was observed between increasing degree of preload in the central screw joint and increasing bone-to-metal contact, most obviously noticed at the tip of the implant thread (p < .01). Misfit stress levels of clinical magnitudes do not seem to jeopardize osseointegration per se. On the contrary, clinical levels of preload stress seem to significantly promote bone remodeling at the tip of the implant thread.

Oral implant treatment (Brånemark System) of edentulous mandibles has been presented in numerous studies. However, with regard to the severely atrophic lower jaw, no long-term follow-up studies with solely short implants are available. The purpose of the present investigation was to retrospectively follow the long-term treatment outcome of patients with severely resorbed edentulous mandibles being subjected to oral implant placement with short (6-7 mm) Brånemark implants. A total of 247 standard (7 mm long, Ø 3.75 mm) and 13 wide (6 mm long, Ø 5 mm) implants were inserted in 49 patients, all of whom exhibited severe resorption of edentate mandibles. Fixed implant-supported prostheses were manufactured for 45 patients, whereas 4 patients received overdentures. The patients were followed for a mean period of 8 years (range, 1-14 yr). Seventeen implants failed during the study period (cumulative implant survival rate 95.5% at 5-yr and 92.3% at 10-yr follow-up). Implant-supported constructions were worn continuously throughout the investigation by all study subjects. Marginal bone loss, measured after 1, 5, and 10 years of function, concurred with studies of Brånemark implants placed in more voluminous mandibles. No major clinical or construction complications occurred in the followed patients. The outcome of the present study showed that placement of short Brånemark implants without the use of bone grafting procedures for reconstruction of severely atrophic edentulous mandibles is a highly predictable treatment procedure.

The present study evaluated implant survival and marginal bone loss in maxillae over a 15-year follow-up period as a function of either monocortical or bicortical implant anchorage. Of 207 standard Brånemark implants (10 mm in length) followed, 110 implants were judged to be monocortically anchored and 97 as bicortically anchored. The bicortically anchored implants failed nearly 4 times more often than the monocortical ones. Implant fractures accounted for over 80% of the observed failures and were found to affect the bicortical group almost 3 times more often. As tentative explanations, induction of increased stress and bending forces resulting from possible prosthetic misfit, presence of unfavorable arch relationships, or high occlusal tables in combination with bicortically anchored implants have been suggested, all indicating an overambitious fixation of the bicortical anchorage. Total marginal bone loss was low over the 15-year period and close to identical for the 2 groups, suggesting that the mode of cortical anchorage did not have any clinically significant influence on marginal bone remodeling.

The purpose of this study was to morphologically describe the tissues surrounding 20 early failed (prior to prosthesis placement) Brånemark System oral implants. The implants and their surrounding tissues were consecutively retrieved and analyzed with light microscopy and transmission electron microscopy. Failures were chronologically divided into those occurring prior to, at, and after abutment connection. The clinical conditions varied from osteomyelitis to totally asymptomatic but mobile implants. Different histopathologic pictures were observed, ranging from a stratified, almost acellular, connective tissue layer, via a capsule with a great number of inflammatory cells, to a heterogeneous interface with areas of highly vascularized connective tissue and portions of poorly mineralized bone detached from the implant surface. The histopathologic variation may reflect different etiologies and/or time stages of the failure process. Epithelial downgrowth was occasionally observed for asymptomatic submerged implants. Epithelial cells were attached to the failed implant surface via hemidesmosomes. The histologic, clinical, and radiographic findings together indicated that 3 major etiologies might have been implicated in the failure processes: impaired healing ability of the host bone site, disruption of a weak bone-to-implant interface after abutment connection, and infection in situations with complicated surgery.

Using a one-stage surgical protocol, 75 implants ad modum Brånemark of three different designs were inserted in 15 edentulous mandibles of high bone density. All implants were followed with repeated stability measurements by means of resonance frequency analysis (RFA) from implant placement to connection of the fixed prostheses (3-4 months), in order to evaluate possible stability changes during healing. It was shown that the resonance frequency (RF) values slightly decreased for the majority of the implants during the study period independent of design. Consequently, the results of the present study indicated that the implants were as stable at time of placement as when measured at 3-4 months post-surgery, i.e. when the prostheses were attached. The available data support the concept of direct loading of implants when inserted between the mental interforaminal regions. One implant failed during healing and the corresponding RF measurement disclosed, at six weeks post-surgery, a value being far below the one registered at implant placement. The lowered RF value indicated the failure several weeks before the mobility was clinically diagnosed. The presence or absence of a fixture/abutment junction did not exert any influence on the marginal bone level, as determined radiographically at the end of the short investigation period.

Using a one-stage surgical protocol, 75 implants ad modum Brånemark of three different designs were inserted in 15 edentulous mandibles of high bone density. All implants were followed with repeated stability measurements by means of resonance frequency analysis (RFA) from implant placement to connection of the fixed prostheses (3–4 months), in order to evaluate possible stability changes during healing. It was shown that the resonance frequency (RF) values slightly decreased for the majority of the implants during the study period independent of design. Consequently, the results of the present study indicated that the implants were as stable at time of placement as when measured at 3–4 months post-surgery, i.e. when the prostheses were attached. The available data support the concept of direct loading of implants when inserted between the mental interforaminal regions. One implant failed during healing and the corresponding RF measurement disclosed, at six weeks post-surgery, a value being far below the one registered at implant placement. The lowered RF value indicated the failure several weeks before the mobility was clinically diagnosed. The presence or absence of a fixture/abutment junction did not exert any influence on the marginal bone level, as determined radiographically at the end of the short investigation period.