Voids and interlayer gaps in Class 1 posterior composite restorations: a comparison between a microlayer and a 2-layer technique.

OBJECTIVE: The main objective was to compare the presence of interlayer gaps between 2 hybrid composites placed using a microlayer and a 2-layer technique. METHOD AND MATERIALS: Standardized Class 1 cavities were prepared in 40 extracted posterior teeth. Two resin composite materials were used. The control group, group A, consisted of samples of the materials extruded out of the manufacturers' syringes. Group B consisted of 10 teeth restored using 2 layers per restoration. Group C consisted of 30 teeth restored using 6 microlayers per restoration. A scanning electron microscope was used to detect voids in the samples. RESULTS: Round, well-defined voids were found in 85% to 100% of the samples within the bulks of the resin composite materials only. A statistically significant relationship between the type of composite and presence of bubbles (Fisher exact test, P = .04) was found among the 2-layer technique group. No statistically significant difference (Fisher exact test, P = .48) was found among the microlayer technique group. Irregular interlayer gaps were found in 5% to 15% of specimens within areas between bulks of composite, as detected by an electron microscope based on the different densities of the bulks of composite and the interlayer areas. No such statistically significant relationship was found (Fisher exact, P = .62) among the study groups. CONCLUSIONS: Voids are routinely found in bulks of composite materials. Higher incidences of interlayer gaps in the 2-layer samples suggest that the use of a microlayering technique may result in fewer gaps.     

Immediate implant placement with transmucosal healing in areas of aesthetic priority. A multicentre randomized-controlled clinical trial I. Surgical outcomes

OBJECTIVES: To compare the clinical outcomes of standard, cylindrical, screw-shaped to novel tapered, transmucosal (Straumann Dental implants immediately placed into extraction sockets. Material and methods: In this randomized-controlled clinical trial, outcomes were evaluated over a 3-year observation period. This report deals with the need for bone augmentation, healing events, implant stability and patient-centred outcomes up to 3 months only. Nine centres contributed a total of 208 immediate implant placements. All surgical and post-surgical procedures and the evaluation parameters were discussed with representatives of all centres during a calibration meeting. Following careful luxation of the designated tooth, allocation of the devices was randomly performed by a central study registrar. The allocated SLA titanium implant was installed at the bottom or in the palatal wall of the extraction socket until primary stability was reached. If the extraction socket was >or=1 mm larger than the implant, guided bone regeneration was performed simultaneously (Bio Oss and BioGide. The flaps were then sutured. During non-submerged transmucosal healing, everything was done to prevent infection. At surgery, the need for augmentation and the degree of wound closure was verified. Implant stability was assessed clinically and by means of resonance frequency analysis (RFA) at surgery and after 3 months. Wound healing was evaluated after 1, 2, 6 and 12 weeks post-operatively. RESULTS: The demographic data did not show any differences between the patients receiving either standard cylindrical or tapered implants. All implants yielded uneventful healing with 15% wound dehiscences after 1 week. After 2 weeks, 93%, after 6 weeks 96%, and after 12 weeks 100% of the flaps were closed. Ninety percent of both implant designs required bone augmentation. Immediately after implantation, RFA values were 55.8 and 56.7 and at 3 months 59.4 and 61.1 for cylindrical and tapered implants, respectively. Patient-centred outcomes did not differ between the two implant designs. However, a clear preference of the surgeon's perception for the appropriateness of the novel-tapered implant was evident. CONCLUSIONS: This RCT has demonstrated that tapered or standard cylindrical implants yielded clinically equivalent short-term outcomes after immediate implant placement into the extraction socket.     

Early tissue reaction at the interface of immediately loaded dental implants

PURPOSE: The treatment of patients with early or immediately loaded dental implants has renewed interest in the behavior of osteoblasts at the implant surface under load. A newly designed dental implant indicated for immediate loading was tested in vivo for early stages of osteoblast behavior at the implant surface. MATERIALS AND METHODS: Thirty-two implants were placed in the mandibles of 8 minipigs. Half of the implants (n = 16) were immediately loaded under occlusal contacts, and implants placed in non-occlusal relations served as a control. RESULTS: All implants, except 1 that showed signs of tissue infection, healed uneventfully and were stable throughout the experimental period. Ultrastructural analysis of mandibular specimens revealed an intimate attachment of osteoblasts to the material surface beginning as early as day 1. Application of either occlusal or non-occlusal load did not alter the phenotypic morphology of the attached osteoblasts. Transmission electron microscopy and x-ray diffraction analysis demonstrated a direct contact of bone-like minerals over the whole implant surface with no signs of crestal hard tissue alteration. Electron diffraction analysis showed a slight release of titanium from the implant side. DISCUSSION: These results indicate that immediate loading of specially designed dental implants can be performed without disruption of the titanium/bone interface or disturbance of osteoblast physiology in the early loading phase. CONCLUSION: Immediate loading protocols can be performed without disturbance of normal bone biology.     

A European HLA Isolate and Its Implications for Hematopoietic Stem Cell Transplant Donor Procurement

Europeans have often been considered a homogenous group in registry donor match predictions, but it is now evident that HLA haplotype frequencies vary across the European continent. Earlier studies have indicated that Finns in northeastern Europe have unique HLA characteristics, and the increasing availability of high-resolution registry donor data is now making more detailed comparisons possible. In the first phase of the present study, estimated HLA haplotype frequencies in stem cell donor registries of Finland and its neighbors Sweden and Russia were calculated using the algorithm of the German National Bone Marrow Donor Registry (ZKRD) and their frequencies were compared with one another and also with that of Germany. Virtual donor searches for 1492 high-resolution typed Finnish patients in the Finnish, Swedish and German registries were then performed, using individual match predictions for each registry. In the last phase, the impact of specifically Finnish-enriched HLA haplotypes on Finnish patients and the use of Finnish registry donors was assessed by analyzing 647 consecutive hematopoietic stem cell transplantation (HSCT) donor searches and 40 exported Finnish HSCTs. The Finnish HLA landscape was more homogenous than the 3 other studied populations, but also genetically distinct from them. The match predictions found a probable 10/10 match for 71%, 41%, and 31% of the Finnish patients in the German, Finnish, and Swedish registries, respectively. Thirty-four of Finland's 100 most frequent HLA haplotypes were represented with a frequency of <.0003 in Germany, and with an 8- to 3262-fold greater frequency in Finland than in Germany. Patients carrying these Finnish-enriched haplotypes were less likely to receive a matched HSCT but more likely to receive it from a domestic donor. Registry donors carrying them were more likely to donate stem cells, both nationally and internationally. The Finnish HLA isolate has a significant impact on both Finnish patients and registry donors, explaining the high use of national registry donors for Finnish patients. Haplotype frequency estimations are an important tool for small registries as well, to help optimize donor match predictions and the size of individual registries.     

Diagnosis and anti-infective therapy of periodontitis

Periodontal diseases (gingivitis and periodontitis) are chronic bacterial infections with a remarkably high prevalence and morbidity. Periodontitis, in contrast to gingivitis, is not reversible, is associated with certain bacterial species and affects all of the soft tissue and bone that support teeth. Among the periodontal pathogens, species, such as Aggregatibacter (Actinobacillus) actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and several forms of uncultivable spirochetes play the major role in the pathogenesis. In severe chronic, recurrent and especially aggressive forms of periodontitis, diagnosis of the species involved and, whenever possible, an optimized evidence-based antimicrobial treatment is indicated. In order to monitor alarming bacterial changes in the periodontal pocket, several techniques, namely microscopy, culture, immunoassays, enzyme tests and DNA-based techniques, have been established and the methods are described in the first part of this review. In the second part, the selection and use of locally delivered (topical) and systemic antibiotics used adjunctively in periodontal therapy are discussed.     

Navigation system for minimally invasive esophagectomy: experimental study in a porcine model

Background

Navigation systems potentially facilitate minimally invasive esophagectomy and improve patient outcome by improving intraoperative orientation, position estimation of instruments, and identification of lymph nodes and resection margins. The authors’ self-developed navigation system is highly accurate in static environments. This study aimed to test the overall accuracy of the navigation system in a realistic operating room scenario and to identify the different sources of error altering accuracy.

Methods

To simulate a realistic environment, a porcine model (n = 5) was used with endoscopic clips in the esophagus as navigation targets. Computed tomography imaging was followed by image segmentation and target definition with the medical imaging interaction toolkit software. Optical tracking was used for registration and localization of animals and navigation instruments. Intraoperatively, the instrument was displayed relative to segmented organs in real time. The target registration error (TRE) of the navigation system was defined as the distance between the target and the navigation instrument tip. The TRE was measured on skin targets with the animal in the 0° supine and 25° anti-Trendelenburg position and on the esophagus during laparoscopic transhiatal preparation.

Results

On skin targets, the TRE was significantly higher in the 25° position, at 14.6 ± 2.7 mm, compared with the 0° position, at 3.2 ± 1.3 mm. The TRE on the esophagus was 11.2 ± 2.4 mm. The main source of error was soft tissue deformation caused by intraoperative positioning, pneumoperitoneum, surgical manipulation, and tissue dissection.

Conclusion

The navigation system obtained acceptable accuracy with a minimally invasive transhiatal approach to the esophagus in a realistic experimental model. Thus the system has the potential to improve intraoperative orientation, identification of lymph nodes and adequate resection margins, and visualization of risk structures. Compensation methods for soft tissue deformation may lead to an even more accurate navigation system in the future.     

Differences in F36VMpl-based in vivo selection among large animal models.

Animal models are indispensable tools for understanding physiological and pathological processes, as well as for developing new therapies. Ultimately, the results of animal experimentation must provide information that can guide the development of therapeutic approaches in humans. Significant differences have been reported comparing a gene therapy approach between different animal models. However, little information exists describing differences among the available large animal models. Here we evaluated, in the hemopoietic cells of baboons, a system of selection that has previously demonstrated activity in mice, in dogs, and in human cells ex vivo. This system employs a derivative of the murine thrombopoietin receptor (F36Vmpl), which is conditionally activated in the presence of a small-molecule drug called a chemical inducer of dimerization (CID). Whereas cultured mouse, human, and, to a lesser extent, dog hemopoietic cells all proliferate in response to the F36Vmpl signal, we observed only a minor and variable response to the F36Vmpl signal in the cultured cells of baboons. Similarly, we have noted significant rises in the frequency of transduced hemopoietic cells in mice and in dogs upon CID administration in vivo; however, here we show that responses to CID administration in three baboons were modest and variable. These findings have general implications for the evaluation and development of new strategies for gene therapy.     

STIMULATED LYMPHOCYTE CULTURES : RESPONDER RECRUITMENT AND CELL CYCLE KINETICS

Lymphocytes, stimulated with different doses of plant mitogens or allogeneic cells, incorporate varying amounts of [³H]thymidine. Theoretically, this may be due to different numbers of responding cells, to earlier proliferative response of these cells, and/or to their more or less rapid transit through the cell cycle. Dog peripheral blood lymphocytes were stimulated in vitro with different doses of phytohemagglutinin (PHA), or with allogeneic lymphocytes. After their synchronization by incubation with hydroxyurea (4 mM), the mean durations of the cell cycle, and of the different cell cycle phases were constant and unrelated to strength or type of stimulation. PHA-stimulated lymphocyte cultures were maintained in the presence of colchicine, to prevent clonal proliferation of responding lymphocytes. DNA uptake in this setting, attributed to first generation responders, was related to the strength of proliferative lymphocyte response in control cultures without colchicine. Furthermore, cell proliferation occurred earlier with greater stimulation. It is concluded that higher [³H]thymidine uptake in vitro by stimulated lymphocytes is due to greater numbers of responding cells, which are triggered into proliferative response earlier, and not to a more rapid transit of the responding cells through the cell cycle.     

Efficient transduction and engraftment of G-CSF-mobilized peripheral blood CD34+ cells in nonhuman primates using GALV-pseudotyped gammaretroviral vectors.

The optimal stem cell source for stem cell gene therapy has yet to be determined. Most large-animal studies have utilized peripheral blood or marrow-derived cells collected after administration of granulocyte colony-stimulating factor (G-SCF) and stem cell factor (SCF); however, SCF is unavailable for clinical use in the United States and the European Union. A recent study in a competitive repopulation assay in the rhesus macaque showed very inefficient marking of G-CSF-mobilized (G/only) peripheral blood (G-PBSC) CD34(+) cells relative to G-CSF and SCF-mobilized cells using vectors with an amphotropic pseudotype. Because G-PBSC would be the preferred target cell population for most clinical stem cell gene therapy applications, we asked whether we could achieve efficient transduction and engraftment of G-PBSC using Phoenix-GALV-pseudotyped vectors. We transplanted three baboons with G/only mobilized CD34(+) cells transduced with GALV-pseudotyped retroviral vectors. We observed high-level, persistent engraftment of gene-modified G-PBSC in all animals with gene marking levels in granulocytes up to 60%. We analyzed amphotropic (PIT2) and GALV (PIT1) receptor expression in G/only cells and found preferential expression of PIT1 after G/only, which may explain the inferior results with amphotropic pseudotypes. These findings demonstrate that high stem cell gene transfer levels can be achieved using G-CSF-mobilized PBSC with Phoenix-GALV-pseudotyped vectors.