The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs

BACKGROUND: It has been shown that different implant designs and different vertical implant positions have an influence on crestal bone levels. The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest. METHODS: Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. The implants were placed submucosally or transmucosally in the left or the right side of the mandible. Within each side, six implants were randomly placed at three distinct levels relative to the alveolar crest. After 12 weeks, 60 crowns were cemented. Radiographs were obtained from all implant sites following implant placement, after crown insertion, and monthly for 6 months after loading. RESULTS: Radiographic analysis revealed very little bone loss and a slight increase in bone level for implants placed at the level of the crest or 1 mm above. The greatest bone loss occurred at implants placed 1 mm below the bone crest. No clinically significant differences regarding marginal bone loss and the level of the bone-to-implant contact were detected between implants with a submucosal or a transmucosal healing. CONCLUSIONS: Implants with non-matching implant-abutment diameters demonstrated some bone loss; however, it was a small amount. There was no clinically significant difference between submucosal and transmucosal approaches.

Accuracy of navigated surgery of the pelvis after surface matching with an a-mode ultrasound probe

Computer-aided surgery (CAS) allows for real-time intraoperative feedback resulting in increased accuracy, while reducing intraoperative radiation. CAS is especially useful for the treatment of certain pelvic ring fractures, which necessitate the precise placement of screws. Flouroscopy-based CAS modules have been developed for many orthopedic applications. The integration of the isocentric flouroscope even enables navigation using intraoperatively acquired three-dimensional (3D) data, though the scan volume and imaging quality are limited. Complicated and comprehensive pathologies in regions like the pelvis can necessitate a CT-based navigation system because of its larger field of view. To be accurate, the patient's anatomy must be registered and matched with the virtual object (CT data). The actual precision within the region of interest depends on the area of the bone where surface matching is performed. Conventional surface matching with a solid pointer requires extensive soft tissue dissection. This contradicts the primary purpose of CAS as a minimally invasive alternative to conventional surgical techniques. We therefore integrated an a-mode ultrasound pointer into the process of surface matching for pelvic surgery and compared it to the conventional method. Accuracy measurements were made in two pelvic models: a foam model submerged in water and one with attached porcine muscle tissue. Three different tissue depths were selected based on CT scans of 30 human pelves. The ultrasound pointer allowed for registration of virtually any point on the pelvis. This method of surface matching could be successfully integrated into CAS of the pelvis.

HLA-Bw4 homozygosity is associated with an impaired CD4 T cell recovery after initiation of antiretroviral therapy

We assessed the influence of human leukocyte antigen (HLA) alleles HLA-Bw4 and HLA-Bw6 on CD4 T cell recovery after starting successful combination antiretroviral therapy in 265 individuals. The median gains in the CD4 T cell count after 4 years were 258 cells/microL for HLA-Bw4 homozygotes, 321 cells/microL for HLA-Bw4/Bw6 heterozygotes, and 363 cells/microL for HLA-Bw6 homozygotes (P = .01, compared with HLA-Bw4 homozygotes). HLA-Bw4 homozygosity appears to predict an impaired CD4 T cell recovery after initiation of combination antiretroviral therapy.

Chest size matching in single and double lung transplantation

We applied predicted vital capacity to chest size matching between donor and recipient in lung transplantation to 15 single-lung transplant recipients with pulmonary fibrosis and to 20 double-lung transplant recipients with emphysema or non-emphysema. The predicted vital capacity of the donor was significantly correlated with the predicted vital capacity of the recipient both in double-lung transplantation (r = 0.79, p = 0.001) and single-lung transplantation (r = 0.71, p = 0.003). In double-lung transplantation, the post-transplant vital capacity was correlated with the predicted vital capacity of the recipient (r = 0.74, p = 0.002). Emphysema patients and non-emphysema patients contributed equally to this correlation. In left single lung transplantation, there was a weak correlation between the post-transplant vital capacity and the predicted vital capacity of the donor in the allograft (r = 0.57, p = 0.1095). In right single lung transplantation, the post-transplant vital capacity of the allograft tended to be correlated with the predicted vital capacity of recipient (r = 0.77, p = 0.0735). We concluded that donors were actually selected based on the comparison of predicted vital capacity between donor and recipient. In double-lung transplantation, the post-transplant vital capacity was limited by the recipient's normal thoracic volume and was not influenced by underlying pulmonary disease. In single-lung transplantation with pulmonary fibrosis, the allograft transplanted in the left chest could expand to its own size, and the allograft transplanted in the right chest could expand to the recipient's normal thoracic volume as in double-lung transplantation.

Anti-HLA I antibodies induce VEGF production by endothelial cells, which increases proliferation and paracellular permeability

Anti-human leukocyte antigen class I (HLA I) antibodies were shown to activate several protein kinases in endothelial cells (ECs), which induces proliferation and cell survival. An important phenomenon in antibody-mediated rejection is the occurrence of interstitial edema. We investigated the effect of anti-HLA I antibodies on endothelial proliferation and permeability, as one possible underlying mechanism of edema formation. HLA I antibodies increased the permeability of cultured ECs isolated from umbilical veins. Anti-HLA I antibodies induced the production of vascular endothelial growth factor (VEGF) by ECs, which activated VEGF receptor 2 (VEGFR2) in an autocrine manner. Activated VEGFR2 led to a c-Src-dependent phosphorylation of vascular endothelial (VE)-cadherin and its degradation. Aberrant VE-cadherin expression resulted in impaired adherens junctions, which might lead to increased endothelial permeability. This effect was only observed after cross-linking of HLA I molecules by intact antibodies. Furthermore, our results suggest that increased endothelial proliferation following anti-HLA I treatment occurs via autocrine VEGFR2 activation. Our data indicate the ability of anti-HLA I to induce VEGF production in ECs. Transactivation of VEGFR2 leads to increased EC proliferation and paracellular permeability. The autocrine effect of VEGF on endothelial permeability might be an explanation for the formation of interstitial edema after transplantation.

Bone response to loaded implants with non-matching implant-abutment diameters in the canine mandible

BACKGROUND: One way to evaluate various implant restorations is to measure the amount of bone change that occurs at the crestal bone. The objective of this study was to histologically evaluate the alveolar bone change around a bone-level, non-matching implant-abutment diameter configuration that incorporated a horizontal offset and a Morse taper internal connection. METHODS: The study design included extraction of all mandibular premolars and first molars in five canines. After 3 months, 12 dental implants were placed at three levels in each dog: even with the alveolar crest, 1 mm above the alveolar crest, and 1 mm below the alveolar crest. The implants were submerged on one side of the mandible. On the other side, healing abutments were exposed to the oral cavity (non-submerged). Gold crowns were attached 2 months after implant placement. The dogs were sacrificed 6 months postloading, and specimens were processed for histologic and histometric analyses. RESULTS: Evaluation of the specimens indicated that the marginal bone remained near the top of the implants under submerged and non-submerged conditions. The amount of bone change for submerged implants placed even with, 1 mm below, and 1 mm above the alveolar crest was -0.34, -1.29, and 0.04 mm, respectively (negative values indicate bone loss). For non-submerged implants, the respective values were -0.38, -1.13, and 0.19 mm. For submerged and non-submerged implants, there were significant differences in the amount of bone change among the three groups (P <0.05). The percentage of bone-to-implant contact for submerged implants was 73.3%, 71.8%, and 71.5%. For non-submerged implants, the respective numbers were 73.2%, 74.5%, and 76%. No significant differences occurred with regard to the percentage of bone contact. CONCLUSIONS: Minimal histologic bone loss occurred when dental implants with non-matching implant-abutment diameters were placed at the bone crest and were loaded for 6 months in the canine. The bone loss was significantly less (five- to six-fold) than that reported for bone-level implants with matching implant-abutment diameters (butt-joint connections).

Functional evaluation of hTM, CD46 and HLA-E transgenes in vitro and in pig leg xenoperfusion experiments

Background Besides α1,3 galactosyltransferase (Gal) gene knockout several transgene combinations to prevent pig-to-human xenograft rejection are being investigated. hCD46/HLA-E double transgenic pigs were tested for prevention of xenograft rejection in an ex vivo pig-to-human xenoperfusion model. In addition, expression of human thrombomodulin (hTM-) on wild-type and/or multi-transgenic (GalTKO/hCD46) background was evaluated to overcome pig-to-human coagulation incompatibility. Methods hCD46/HLA-E double transgenic as well as wild-type pig forelimbs were ex vivo perfused with whole, heparinized human blood and autologous blood, respectively. Blood samples were analyzed for production of porcine and/or human inflammatory cytokines. Biopsy samples were examined for deposition of complement proteins as well as E-selectin and VCAM-1 expression. Serial blood cell counts were performed to analyze changes in human blood cell populations. In vitro, PAEC were analyzed for ASGR1 mediated human platelet phagocytosis. In addition, a biochemical assay was performed using hTM-only and multi-transgenic (GalTKO/hCD46/hTM) pig aortic endothelial cells (PAEC) to evaluate the ability of hTM to generate activated protein C (APC). Subsequently, the anti-coagulant properties of hTM were tested in a microcarrier based coagulation assay with PAEC and human whole blood. Results No hyperacute rejection was seen in the ex vivo perfusion model. Extremity perfusions lasted for up to 12 h without increase of vascular resistance and had to be terminated due to continuous small blood losses. Plasma levels of porcine IL1β (P < 0.0001), and IL-8 (P = 0.019) as well as human C3a, C5a and soluble C5b-9 were significantly (P < 0.05–<0.0001) lower in blood perfused through hCD46/HLA-E transgenic as compared to wild-type limbs. C3b/c, C4b/c, and C6 deposition as well as E-selectin and VCAM-1 expression were significantly (P < 0.0001) higher in tissue of wild-type as compared to transgenic limbs. Preliminary immunofluorescence staining results showed that the expression of hCD46/HLA-E is associated with a reduction of NK cell tissue infiltration (P < 0.05). A rapid decrease of platelets was observed in all xenoperfusions. In vitro findings showed that PAEC express ASGR1 and suggest that this molecule is involved in human platelet phagocytosis. In vitro, we found that the amount of APC in the supernatant of hTM transgenic cells increased significantly (P < 0.0001) with protein C concentration in a dose-dependent manner as compared to control PAEC lacking hTM, where the turnover of the protein C remained at the basal level for all of the examined concentration. In further experiments, hTM also showed the ability to prevent blood coagulation by three- to four-fold increased (P < 0.001) clotting time as compared to wild-type PAEC. The formation of TAT complexes was significantly lower when hTM-transgenic cells (P < 0.0001) were used as compared to wild-type cells. Conclusions Transgenic hCD46/HLA-E expression clearly reduced humoral xenoresponses since the terminal pathway of complement, endothelial cell activation, inflammatory cytokine production and NK-cell tissue infiltration were all down-regulated. We also found ASGR1 expression on the vascular endothelium of pigs, and this molecule may thus be involved in binding and phagocytosis of human platelets during pig-to-human xenotransplantation. In addition, use of the hTM transgene has the potential to overcome coagulation incompatibilities in pig-to-human xenotransplantation.

Do implicit motives and basic psychological needs interact to predict well-being and flow? Testing a universal hypothesis and a matching hypothesis

Self-Determination Theory (Deci and Ryan in Intrinsic motivation and self-determination in human behavior. Plenum Press, New York, 1985) suggests that certain experiences, such as competence, are equally beneficial to everyone’s well-being (universal hypothesis), whereas Motive Disposition Theory (McClelland in Human motivation. Scott, Foresman, Glenview, IL, 1985) predicts that some people, such as those with a high achievement motive, should benefit particularly from such experiences (matching hypothesis). Existing research on motives as moderators of the relationship between basic need satisfaction and positive outcomes supports both these seemingly inconsistent views. Focusing on the achievement motive, we sought to resolve this inconsistency by considering the specificity of the outcome variables. When predicting domain-specific well-being and flow, the achievement motive should interact with felt competence. However, when it comes to predicting general well-being and flow, felt competence should unfold its effects without being moderated by the achievement motive. Two studies confirmed these assumptions indicating that the universal and matching hypotheses are complementary rather than mutually exclusive.