Functionality testing of an innovative biomechanically optimized and surface-modified orthodontic mini-screw-a comparative study.

PURPOSE: The failure rate of orthodontic mini-screws depends strongly on primary stability and, thus, on insertion torque. Further improvement regarding the failure rate might be achieved by modifying the surface coating. Therefore, the aim of the study was to investigate the stability of a newly designed and surface-modified orthodontic mini-screw in beagle dogs. METHODS: Newly designed mini-screws coated either with DOTIZE® or DOTIZE®-copper (DOT GmbH, Rostock, Germany; each: n = 24) were inserted in the mandibles of eight beagle dogs for a duration of 8 months. Insertion and removal torque were measured. These data were compared to values generated by using the artificial bone material Sawbones® (Sawbones Europe AB, Malmö, Sweden). Experiments with and without torque limitation (each: n = 5) were run. The bone-to-implant contact rate and the amount of bone between the threads were examined. Statistical significance was set at P < 0.05. RESULTS: The success rates of the in vivo study reached high levels with 95.3% for the DOTIZE-coated and 90.5% for the DOTIZE-copper-coated screws, whereas the insertion and removal torque did not differ between the coatings. During insertion, a torque limitation of 20 Ncm was necessary to ensure that the recommended limit was not exceeded. The insertion in Sawbones without torque limitation revealed a significantly higher torque compared to torque-limited insertion (18.2 ± 1.3 Ncm, 23.6 ± 1.3 Ncm). Bending occurred (n = 5) in the thread-free part of the mini-screw. CONCLUSIONS: Surface coating might be able to improve the performance of orthodontic mini-screws. The study showed high success rates and stable mini-screws until the end of observation. Further investigations are necessary.

Influence of Test Specimen Geometry and Water Soaking on the In Vitro Cytotoxicity of Orthocryl®, Orthocryl® LC, Loctite® EA 9483 and Polypropylene.

Depending on their composition, plastics have a cytotoxic potential that needs to be evaluated before they are used in dentistry, e.g., as orthodontic removable appliances. Relevant guidelines set out requirements that a potential new resin in the medical field must meet, with a wide scope for experimental design. In the present study, test specimens of different geometries consisting of varying polymers (Orthocryl®, Orthocryl® LC, Loctite® EA 9483, Polypropylene) were soaked for different periods of time, then transferred to cell culture medium for 24 h, which was subsequently used for 24-h cultivation of A549 cells, followed by cytotoxicity assays (WST-1, Annexin V-FITC-propidium iodide (PI) flow cytometry). In this context, a reduction in the cytotoxic effect of the eluates of test specimens prepared from Orthocryl® LC and Loctite® EA 9483 was particularly evident in the Annexin V-FITC-PI assay when the soaking time was extended to 48 h and 168 h, respectively. Consistent with this, a reduced release of potentially toxic monomers into the cell culture medium, as measured by gas chromatography-mass spectrometry, was observed when the prior soaking time of test specimens of all geometries was extended. Remarkably, a significant increase in cytotoxic effect was observed in the WST-1 assay, which was accompanied by a higher release of monomers when the thickness of the test sample was increased from 0.5 to 1.0 mm, although an elution volume adapted to the surface area was used. However, further increasing the thickness to 3.0 mm did not lead to an increase in the observed cytotoxicity or monomer release. Test specimens made of polypropylene showed no toxicity under all test specimen sizes and soaking time conditions. Overall, it is recommended to perform toxicity studies of test specimens using different geometries and soaking times. Thereby, the influence of the different specimen thicknesses should also be considered. Finally, an extension of the test protocols proposed in ISO 10993-5:2009 should be considered, e.g., by flow cytometry or monomer analysis as well as fixed soaking times.

Osteoblast growth, after cleaning of biofilm-covered titanium discs with air-polishing and cold plasma.

AIM: To investigate the effects of a combined biofilm removal with an optimized air polishing and a cold plasma device on cells in vitro. MATERIALS AND METHODS: A 7-day-old biofilm was removed from rough titanium discs with an air-polishing device with erythritol powder (AP) or with a cold atmospheric pressure argon plasma (CAP) device or in combination of both (AP + CAP). The removal efficacy was evaluated by subsequent cell seeding of osteoblast-like cells (MG-63). The cell spreading was analysed after 5 days of incubation by scanning electron microscopy. Separately, the surface hydrophilicity was analysed by measuring the water contact angle (WCA) of the disc for each treatment method. RESULTS: The mechanical plaque removal with AP rendered specimen conducive for cell growth, 85% of the surface was covered with cells. An advantage of the combination of AP + CAP was not detectable compared to AP (cell coverage ranged from 57% up to 75%). After sole CAP treatment, microorganisms re-grew and destroyed all cells. The WCA was reduced by all treatment methods. CONCLUSION: An AP treatment has the potential to remove biofilm from rough implant surfaces completely. In contrast to our hypothesis, the combination of plasma and AP treatment did not enhance osteoblast spreading.

Skeletal effects in Angle Class II/1 patients treated with the functional regulator type II : Cephalometric and tensor analysis.

OBJECTIVES: The purpose of this work was to employ both cephalometric and tensor analysis in characterizing the skeletal changes experienced by patients with Angle Class II/1 malocclusion during functional orthodontic treatment with the functional regulator type II. METHODS: A total of 23 patients with Class II/1 malocclusion based on lateral cephalograms obtained before and after treatment with the functional regulator type II were analyzed. Another 23 patients with Angle Class II/1 malocclusion who had not undergone treatment were included as controls. RESULTS: Our cephalometric data attest to significant therapeutic effects of the functional regulator type II on the skeletal mandibular system, including significant advancement of the mandible, increases in effective mandibular length with enhancement of the chin profile, and reduction of growth-related bite deepening. No treatment-related effects were observed at the cranial-base and midface levels. In addition, tensor analysis revealed significant stimulation of mandibular growth in sagittal directions, without indications of growth effects on the maxilla. Its growth-pattern findings differed from those of cephalometric analysis by indicating that the appliance did promote horizontal development, which supports the functional orthodontic treatment effect in Angle Class II/1 cases. CONCLUSIONS: Tensor analysis yielded additional insights into sagittal and vertical growth changes not identifiable by strictly cephalometric means. The functional regulator type II was an effective treatment modality for Angle Class II/1 malocclusion and influenced the skeletal development of these patients in favorable ways.

Cold atmospheric plasma in combination with mechanical treatment improves osteoblast growth on biofilm covered titanium discs.

Treatment of implants with peri-implantitis is often unsuccessful, because an instrumented implant surface and residual microbial biofilm impedes re-osseointegration. The application of cold atmospheric plasma (CAP) could be a simple and effective strategy to overcome the inherent problems of peri-implantitis treatment. CAP is able to destroy and eliminate bacterial biofilms. Additionally, it increases the wettability of titanium, which supports cellular attachment. In this study, the behaviour of osteoblasts on titanium discs was analysed after treatment of bacterial biofilms with CAP, brushing, or a combination of both. A human plaque biofilm was cultured on titanium discs. Treatment with a brush (BR), 1% oxygen/argon CAP (PL), or brushing combined with CAP (BR+PL) was used to eliminate the biofilm. Discs without biofilm (C), autoclaved biofilm (AUTO) and untreated biofilm (BIO) served as controls. Subsequently, human osteoblastic cell growth (MG-63) was observed after 1 and 24 h. Biofilm remnants on BR and PL impaired osteoblastic cell development, whereas the BR+PL provided an increased area of osteoblastic cells. A five-day cell growth was only detectable on BR+PL treated discs. The combination of established brushing and CAP application may be a promising strategy to treat peri-implantitis.

Microstructured zirconia surfaces modulate osteogenic marker genes in human primary osteoblasts.

In dentistry, zirconia has been used since the early 1990s for endodontic posts, more recently for implant abutments and frameworks for fixed dental prostheses. Zirconia is biocompatible and mechanically strong enough to serve as implant material for oral implants. Although several zirconia implant systems are available, currently the scientific and clinical data for zirconia implants are not sufficient to recommend them for routine clinical use. Here the influence of microstructured yttria-stabilized zirconia (YZ) on human primary osteoblast (HOB) behavior was determined. YZ surfaces were treated by sandblasting (YZ-S), acid etching (YZ-SE) and additionally heat treatment (YZ-SEH). Morphological changes of HOB were determined by scanning electron microscopy. Actin cytoskeleton was investigated by laser scanning microscopy and analyzed by novel actin quantification software. Differentiation of HOB was determined by real time RT-PCR. Improved mechanical interlocking of primary HOB into the porous microstructure of the acid etched and additionally heat treated YZ-surfaces correlates with drastically increased osteocalcin (OCN) gene expression. In particular, OCN was considerably elevated in primary HOB after 3 days on YZ-SE (13-fold) as well as YZ-SEH (12-fold) surfaces. Shorter actin filaments without any favored orientation on YZ-SE and YZ-SEH surfaces are associated with higher roughness (Ra) values. Topographically modified yttria-stabilized zirconia is a likely material for dental implants with cell stimulating properties achieving or actually exceeding those of titanium.

Atmospheric plasma enhances wettability and cell spreading on dental implant metals.

OBJECTIVES: Treatment regimens, which predictably support re-osseointegration of implants with peri-implantitis, are needed. Increased wettability may be an important factor for re-osseointegration. In this study, a cold atmospheric pressure gas-discharge plasma was applied to reduce water contact angles on titanium discs with different surface topography and to improve the spreading of osteoblastic cells. MATERIAL AND METHODS: An argon plasma jet with different oxygen admixtures was used to treat titanium discs with different topologies, i.e. machined, SLA(®) , SLActive(®) , diamond bur-treated or Airflow(®) -treated. Water contact angles were measured before and after plasma treatment. The spreading behaviour of human osteoblastic cells was investigated. RESULTS: Contact angle of titanium discs (baseline values: 68°-117°) were significantly reduced close to 0° irrespective of surface topography after the application of argon plasma with 1.0% oxygen admixture for 60 s or 120 s. The cell size of osteoblastic cells grown on argon-oxygen-plasma-treated titanium discs was significantly larger than on non-treated surfaces (p < 0.001) irrespective of surface topography. CONCLUSIONS: Plasma treatment reduced contact angle and supported spreading of osteoblastic cells. The application of cold plasma may be supportive in the treatment of peri-implant lesions and may improve the process of re-osseointegration.

Influence of phytoestrogens on the proliferation and expression of adhesion receptors in human mammary epithelial cells in vitro.

Tumor metastasis is associated with integrin-mediated adhesion and hyaluronan receptor expression. Accumulating evidence suggests that phytoestrogens, which are naturally occurring, plant-derived phytochemicals, could inhibit tumorigenesis during the development of breast cancer. Less is known, however, about the regulation of adhesion receptors by phytoestrogens and, particularly, their potency to influence proliferation of primary human breast cells in comparison with the steroid hormone 17beta-estradiol. Throughout the proliferation experiments, we used primary human mammary epithelial cells from normal tissue that was derived from plastic surgery. For receptor expression (beta1, alpha2, alpha3, CD44), we used the cell line MCF-7. Both investigations were carried out by flow cytometry. The phenotype of primary human mammary epithelial cells was microscopically characterized by analyzing the distribution of ZO-1, cytokeratin and the estrogen receptors alpha and beta. The integrins and the hyaluronan receptor were significantly up-regulated with 17beta-estradiol in human MCF-7 cells. In contrast, genistein and daidzein did not affect the expression at a concentration of 100 micromol/l. In all proliferation experiments with a significant stimulation of the primary human mammary epithelial cell growth due to 17beta-estradiol, in general, genistein and daidzein did not influence S-phase and G2/M-phase cells. Additionally, the stimulative effect of 17beta-estradiol could be inhibited. As the phytoestrogens do not up-regulate adhesion receptors in human breast cells and, regarding proliferation, are able to abolish the stimulatory effect of 17beta-estradiol, we suggest that phytoestrogens could have beneficial effects for the prevention or inhibition of carcinogenesis in hormone-dependent malignancies.