Success rate of palatal orthodontic implants: a prospective longitudinal study

AIM: The purpose of this prospective cohort study was to assess the survival and success rates of palatal implants. MATERIAL AND METHODS: Seventy patients (56 female, 14 male; age 25-6 +/- 10-8 years) receiving Orthosystem (Straumann AG, Basel, Switzerland) palatal implants from March 1999 to November 2006 were included. The indication was established according to the required anchorage for orthodontic therapy. All implants were placed in a mid-sagittal, median or paramedian palatal location by the same surgeon. They were orthodontically loaded after a healing period of 8-16 weeks (Mean: 12.8 weeks). RESULTS AND DISCUSSION: Of the initially 70 consecutively admitted patients, two implants in two patients were not primary stable after installation and had to be removed. Of the 70 initially installed palatal implants, 67 implants or 95.7% osseointegrated successfully and were loaded actively and/or passively for approximately 19 months. Only one implant of the 67 osseointegrated implants lost its stability under orthodontic loading. By the time of re-evaluation, 20 palatal implants were still used for orthodontic therapy, while 46 implants had been removed after completed orthodontic therapy. By only analyzing those, the success rate of the initially installed implants was 92%. CONCLUSIONS: Orthodontic palatal implants with a rough surface are predictable and highly reliable devices for a multitude of maxillary orthodontic treatment options. The survival and success rates for palatal orthodontic implants are comparable to dental implants installed for dental prostheses

Characterization and MRI detection of 19F-PLGA labelled human mesenchymal stem cells

Introduction 19F based stem-cell labelling is attractive, since it may enable long-term studies of cellular migration provided sufficient detection sensitivity can be achieved and has no background signal. Several 19F based compounds are based on a cocktail of approved pharmaceutical compounds, that facilitates translationonal studies. 19F-PLGA: poly(D,L-lactide-co-glycolide) has successfully been used for tracking of dendritic cells and has clinical research approval [1]. Methods 19F PLGA nanoparticles (19F PLGA NP) of various compositions, with and without surface modification were prepared by encapsulation of of perfluoro-15-crown-5-ether and by optical probes (carboxyfluorescein). The nanoparticle size was determined by DLS light scattering. Human mesenchymal stem cells (hMSC) were incubated in a solution containing a maximum of 4mg of the nanoparticles for a 1-3 days. The influence of 19F-PLGA-NP labelling on the following parameters was investigated: proliferation kinetics, colony generation, adhesion, surface migration, and presence of stem-cell markers. Fluorescence microscopy was used to verify cellular uptake of the compound, while cell loading was determined by MR spectroscopy and referencing to tri-fluoroacetic acid at 7T. The longitudinal relaxation time of the free nanoparticles and after hMSC labelling was determined at 7T. MRI sequence optimization was performed by simulation of the expected MR signal in Matlab [2] and labelled cells were measured either as a pellet or as an agarose suspension. Results Without surface modification, no uptake in hMSC occurred (0.01x1012 19F/cell). while the cell-load increased after surface modification and optimization of the loading protocol (0.29-1.16x1012 19F/cell). The size of the nanoparticles was 306nm, with a PDI of 0.16. No significant influence of 19F-PLGA-NPs on the cells was observed after achieving a cell loading of 1.16x1012 19F/cell. The T1 time of the 19F-PLGA-NP decreased from 1090 to 790ms after loading. In vitro, the T2 time was 590ms. The MRI detection limit with a cell load of 0.4x1012 19F/cell in a 2h scan was 20.000 cells (pellet) or 10.000 cells per microliter (suspension). Conclusions Besides optimization of the imaging protocol, a significant increase in MRI sensitivity can be achieved through improving the cell-load. The 19F-PLGA-NP did not significantly alter the properties of hMSC. In vivo studies of 19F-PLGA-NP labelled hMSC are under way to verify the utility of this technique in a pre-clinical setting

Magnetic retraction: A viable method for the purification of encapsulated islet grafts

Islet cell transplantation is a promising option for the restoration of normal glucose homeostatsis in patients with type-1 diabetes. But problems remain regarding the efficient use of donor cells and the prevention of graft rejection by the host immune system. Previously, we were able to show that xenotransplantation of microencapsulated rat and human islets cells can achieve life-long graft function in immunocompetent diabetic mice without the need for immunosuppression [1]. Since the microencapsulation of islets results in a significant amount of empty capsules, and since graft volume is a crucial issue, we developed a new method which uses magnetic labeling and separation of the microencapsulated islets witch supramagnetic iron particles (SPIO) in order to eliminate empty capsules. For this purpose, rat islets were isolated and labeled with two different concentrations of SPIO (3 and 30µl/ml Resovist®, respectively) before microencapsulation in alginate beads as described [1]. Before transplantation into diabetic mice, the magnetic capsules were separated from the empty capsules using a newly developed linear magnetic flow apparatus. Using this method we were able to reduce the ratio of empty capsules (EC) to islet containing capsules (IC) from 4:1 to at least 2:1 or 1:1 in the low (3µg/ml) and high (30µg/ml) SPIO concentration group, respectively. In vitro viability and functionality assessment using the insulin stimulation index did not show any differences between SPIO-labeted islets and freshly isolated unlabeled islets. For proof of in vivo function 3500 islet equivalents (Ieq) of SPIO-labeled islets from both concentrations were transplanted in the peritoneal cavity of streptozotozin-diabetic immunocompetent balb/c mice, resulting in long term (>30 weeks) normoglycemia. We conclude, that magnetic separation of SPIO-labelled encapsulated islets is a clinically safe and effective principle to significantly decrease the graft volume without impairing graft quality and function

Targeting the homing of stem cells via suppression of cell adhesion in the peripheral vasculature

The general approach of the so far developed technologies is the attempt to increase the homing rate of transplanted stem cells by modifying the molecules/receptors that interact directly with the chemokines/ligands in the damaged tissue. Our unique technology does not interact with the natural repertoire of specific molecules/receptors mediating homing of stem cells to the damaged tissue (SPECIFIC HOMING) but impairs the function of molecules/receptors that are responsible for the adhesion of stem cells throughout the non-damaged vasculature (NON-SPECIFIC CELL ADHESION). Moreover and most importantly, our highly effective technology is non-toxic, does not affect stem cell function and does not require genetic modifications thus making it a most promising candidate for clinical us