Alexander C. Kübler

Cytocompatibility of brushite and monetite cell culture scaffolds made by three-dimensional powder printing

This study investigated the cytocompatibility of low-temperature direct 3-D printed calcium phosphate scaffolds in vitro. The fabrication of the scaffolds was performed with a commercial 3-D powder printing system. Diluted phosphoric acid was printed into tricalcium phosphate powder, leading to the formation of dicalcium phosphate dihydrate (brushite). Hydrothermal conversion of the brushite matrices led to the formation of dicalcium phosphate anhydrous (monetite). The biocompatibility was investigated using the osteoblastic cell line MC3T3-E1. Cell viability and the expression of alkaline phosphatase served as parameters. The culture medium was analyzed for pH value, concentration of free calcium and phosphate ions and osteocalcin. Both types of scaffolds showed a considerable increase of cell proliferation and viability; the monetite matrices were a little inferior compared with the brushite ones. The activity of alkaline phosphatase showed a similar pattern. Optical and electron microscopy revealed an obvious cell growth on the surface of both materials. Analysis of the culture medium showed minor alterations of pH value within the physiological range. The concentrations of free calcium and phosphate ions were obviously different among brushite and monetite cultures, due to their different solubility. The content of osteocalcin of the culture medium was reduced by the printed scaffolds due to adsorption. We conclude that the powder printed brushite and monetite matrices have a suitable biocompatibility for their use as cell culture scaffolds. Both materials enable osteoblastic cells in vitro to proliferate and differentiate due to the expression of typical osteoblastic markers.

Phase composition, mechanical performance and in vitro biocompatibility of hydraulic setting calcium magnesium phosphate cement

Brushite (CaHPO(4) x 2H(2)O)-forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. However, their short setting times and low mechanical strengths limit broad clinical application. In this study, we showed that a significant improvement of these properties of brushite cement could be achieved by the use of magnesium-substituted beta-tricalcium phosphate with the general formula Mg(x)Ca((3-x))((PO(4))(2) with 0 < x < 3 as cement reactants. The incorporation of magnesium ions increased the setting times of cements from 2 min for a magnesium-free matrix to 8-11 min for Mg(2.25)Ca(0.75)(PO(4))(2) as reactant. At the same time, the compressive strength of set cements was doubled from 19 MPa to more than 40 MPa after 24h wet storage. Magnesium ions were not only retarding the setting reaction to brushite but were also forming newberyite (MgHPO(4) x 3H(2)O) as a second setting product. The biocompatibility of the material was investigated in vitro using the osteoblast-like cell line MC3T3-E1. A considerable increase of cell proliferation and expression of alkaline phosphatase, indicating an osteoblastic differentiation, could be noticed. Scanning electron microscopy analysis revealed an obvious cell growth on the surface of the scaffolds. Analysis of the culture medium showed minor alterations of pH value within the physiological range. The concentrations of free calcium, magnesium and phosphate ions were altered markedly due to the chemical solubility of the scaffolds. We conclude that the calcium magnesium phosphate (newberyite) cements have a promising potential for their use as bone replacement material since they provide a suitable biocompatibility, an extended workability and improved mechanical performance compared with brushite cements.

Natural resistance to ascorbic acid induced oxidative stress is mainly mediated by catalase activity in human cancer cells and catalase-silencing sensitizes to oxidative stress

BackgroundAscorbic acid demonstrates a cytotoxic effect by generating hydrogen peroxide, a reactive oxygen species (ROS) involved in oxidative cell stress. A panel of eleven human cancer cell lines, glioblastoma and carcinoma, were exposed to serial dilutions of ascorbic acid (5-100 mmol/L). The purpose of this study was to analyse the impact of catalase, an important hydrogen peroxide-detoxifying enzyme, on the resistance of cancer cells to ascorbic acid mediated oxidative stress.MethodsEffective concentration (EC50) values, which indicate the concentration of ascorbic acid that reduced the number of viable cells by 50%, were detected with the crystal violet assay. The level of intracellular catalase protein and enzyme activity was determined. Expression of catalase was silenced by catalase-specific short hairpin RNA (sh-RNA) in BT-20 breast carcinoma cells. Oxidative cell stress induced apoptosis was measured by a caspase luminescent assay.ResultsThe tested human cancer cell lines demonstrated obvious differences in their resistance to ascorbic acid mediated oxidative cell stress. Forty-five percent of the cell lines had an EC50 > 20 mmol/L and fifty-five percent had an EC50 < 20 mmol/L. With an EC50 of 2.6–5.5 mmol/L, glioblastoma cells were the most susceptible cancer cell lines analysed in this study. A correlation between catalase activity and the susceptibility to ascorbic acid was observed. To study the possible protective role of catalase on the resistance of cancer cells to oxidative cell stress, the expression of catalase in the breast carcinoma cell line BT-20, which cells were highly resistant to the exposure to ascorbic acid (EC50: 94,9 mmol/L), was silenced with specific sh-RNA. The effect was that catalase-silenced BT-20 cells (BT-20 KD-CAT) became more susceptible to high concentrations of ascorbic acid (50 and 100 mmol/L).ConclusionsFifty-five percent of the human cancer cell lines tested were unable to protect themselves against oxidative stress mediated by ascorbic acid induced hydrogen peroxide production. The antioxidative enzyme catalase is important to protect cancer cells against cytotoxic hydrogen peroxide. Silenced catalase expression increased the susceptibility of the formerly resistant cancer cell line BT-20 to oxidative stress.

Influence of Skeletal and Local Bone Density on Dental Implant Stability in Patients with Osteoporosis

BACKGROUND AND PURPOSE Osteoporosis is a major skeletal disease affecting millions of people worldwide. Recent studies claim that patients with osteoporosis do not have a higher risk of early implant failure compared to non-osteoporotic patients. The aim of this study was to assess the effect of skeletal osteoporosis and local bone density on initial dental implant stability. MATERIALS AND METHODS Seventy-three patients were recruited and were assigned (based on a Dual-energy X-ray Absorptiometry scan) to either the osteoporosis (Opr), osteopenia (Opn), or control (C) group. Forty nine of the 73 patients received dental implants and had implant stability measured by means of resonance frequency analysis (RFA) at implant placement and at prosthetic abutment placement. On the computerized tomography scans, the cortical thickness and the bone density (Hounsfield Units) at the sites of implant placement were measured. RESULTS At implant placement, primary stability was on average lower in group Opr (63.3 ± 10.3 ISQ) than in group Opn (65.3 ± 7.5 implant stability qutient (ISQ)), and group C (66.7 ± 8.7 ISQ). At abutment placement, a similar trend was observed: group Opr (66.4 ± 9.5 ISQ) scored lower than group Opn (70.7 ± 7.8 ISQ), while the highest average was for group C (72.2 ± 7.2 ISQ). The difference between groups Opr and C was significant. Implant length and diameter did not have a significant effect on implant stability as measured with RFA. A significant correlation was found between local bone density and implant stability for all regions of interest. CONCLUSIONS Implant stability seems to be influenced by both local and skeletal bone densities. The lower stability scores in patient with skeletal osteoporosis reinforce the recommendations that safe protocols and longer healing times could be recommended when treating those patients with dental implants.

Multi-directional Le Fort III midfacial distraction using an individual prefabricated device.

BACKGROUND Midfacial distraction following Le Fort III osteotomy has become an established procedure for midfacial advancement of syndromic craniosynostosis patients. A frequent difficulty is the precise three dimensional (3D) alignment of the distracted midface and the proper fixation of the distraction device in the midfacial area. In this study we present an individual modification method for commercial distraction devices comprising the establishment of prefabricated fixation plates and parallel connecting pins. MATERIAL Individual prefabricated fixation plates for the zygomatic buttress were combined with two commercial distraction devices. METHOD The fixation plates were made by a casting technique using individual cranial models as templates. The latter were fabricated by the rapid prototyping technique of 3D powder printing. For precise realization of the distraction vector, two commercial devices were combined and attached rigidly to the fixation plates by two parallel pins. RESULT In the clinical routine, the 3D powder printing technique enables the simple fabrication of precise individual cranial models, which are required for manufacturing individual fixation plates. The combination of two commercial distraction devices facilitates the appropriate transfer of complex distraction vectors into the midfacial area. CONCLUSION The technique presented should be useful for a precise multi-directional midfacial distraction following Le Fort III osteotomy.

The current state of facial prosthetics – A multicenter analysis

Even though modern surgical techniques are dominating reconstructive facial procedures, the capability to use facial epitheses for reconstruction is still an important skill for the maxillofacial surgeon. We present an international multicenter analysis to clarify which techniques are used to fixate facial prostheses. We contacted all maxillofacial departments in Germany, Austria, Switzerland and Norway which were registered with the German society for oral and maxillofacial surgery (DGMKG). These centers were asked via electronical mail to provide information on the type of epithesis fixation systems currently in use. The return rate from 58 departments was 43.1% (n = 25). Overall, implant fixation was the preferred fixation system (92%). Plates were the second most common fixation technique (32%). No centers reported the standard use of non-invasive fixation techniques for permanent epithesis fixation. The main retention systems in use were magnets (24/25), other retention systems are used much less often. The current preferred fixation technique for facial epitheses consists of implant-based, magnet-fixated epitheses. For nasal prostheses, a plate-based, magnet-fixated system is often used.

Preoperative vs. postoperative radiochemotherapy in patients with N2 squamous cell carcinoma of the oral cavity

BACKGROUND The aim of our study was to evaluate retrospectively whether neoadjuvant or adjuvant radiochemotherapy yields better survival for patients with N2-oral squamous cell carcinoma and to identify subgroups, which may benefit from one of the therapeutic settings. No studies have been carried out to investigate whether radiochemotherapy should be applied before or after surgery. METHODS In total, 151 patients with oral squamous cell carcinoma with N2-nodal-status were reviewed. Eighty five patients received neoadjuvant radiochemotherapy, 66 patients were treated with surgery and adjuvant radiochemotherapy. Overall survival was plotted by Kaplan-Meier analysis. Prognostic factors were identified through univariate and multivariate analysis. RESULTS Patients treated with neoadjuvant radiochemotherapy had a significantly improved 5-year survival in comparison to patients, who received adjuvant radiochemotherapy (46.3% vs. 27.4%, p=0.035). A subgroup analysis by T-stage revealed that neoadjuvant and adjuvant radiochemotherapy yielded similar 5-year survival rates for patients with T2N2-tumors (42.3% vs. 41.2%, p=0.871), whereas patients with T4bN2-tumors significantly benefitted from neoadjuvant treatment (37.3% vs. 9.7%, p=0.019). CONCLUSIONS Neoadjuvant radiochemotherapy is an effective treatment for patients with nodal status N2-oral squamous cell carcinoma, however prospective randomized trials are needed to confirm, which patients should be treated with neoadjuvant or adjuvant radiochemotherapy.

Occipital plagiocephaly: unilateral lambdoid synostosis versus positional plagiocephaly

Objective We defined parameters that could differentiate between positional and synostotic plagiocephaly and defined a diagnostic chart for decision making. Design Prospective study. Setting We examined 411 children with non-syndromic skull abnormalities between January 2011 and December 2012. Participants A total of 8 infants under 1 year of age with proven unilateral non-syndromic lambdoid synostosis (LS) and 261 children with positional deformity were examined to outline the specific clinical features of both diagnoses. After clinical examination, an ultrasound revealed either a closed suture suggestive of LS or a patent lambdoid suture suggestive of positional deformity. For patients with synostosis, plain radiographs, MR imaging and follow-up examinations were performed. In cases of open sutures, only follow-ups were completed. Main outcome measure Clinical, imaging, genesis and treatment differences between positional plagiocephaly and LS. Results In all 8 cases of unilateral LS and 258 cases of positional plagiocephaly, the diagnosis was established by clinical examination alone. In three cases of positional plagiocephaly, diagnosis was determined after an additional ultrasonography. MR imaging revealed a unilateral tonsillar herniation in five of the eight children with LS and hydrocephalus in one child. Conclusions We have suggested a list of clinical features that specify the underlying cause of posterior plagiocephaly. An additional ultrasound scanning confirmed the diagnosis without any risks of ionising radiation or sedation as in a CT scan.

Relation between Spongy Bone Density in the Maxilla and Skeletal Bone Density

BACKGROUND AND PURPOSE Osteoporosis is a disease affecting more than 300 million people worldwide and is responsible for numerous medical complications. This study aimed to investigate the relation between skeletal and maxillary bone density. MATERIALS AND METHODS Seventy-three patients were recruited and divided between group A (osteoporosis), group B (healthy, control), and group C (osteopenia) on the basis of a dual-energy x-ray absorptiomery (DXA) scan. These patients also received a CT scan on which bone density measurements were performed at five sites: maxilla midline, retromolar tuberosities, incisor, premolars, and molar regions. RESULTS The bone density was lower in osteoporotic patients compared with the control patients. The bone mineral density (BMD) of the tuberosities showed the strongest correlations with the BMD of the hip and the spine (respectively, r = 0.50 and r = 0.61). The midline region showed moderate correlations with the hip (r = 0.47) and the spine (r = 0.46). For potential implant sites, the correlations with the BMD of the hip and spine were, however, small to insignificant. Based on measurements of bone density of the maxilla, it was possible to predict if the patient was osteoporotic or not with a sensitivity of 65% and a specificity of 83%. CONCLUSIONS The maxillary bone density of subjects with osteoporosis is significantly lower than that of healthy patients. Moreover, there is a direct correlation between the density of the skeleton and the density of some sites of the maxilla. Using measurements of maxillary bone density in order to predict skeletal bone density might be a useful tool for the screening of osteoporosis.

Perception of children’s faces with unilateral coronal synostosis—an eye-tracking investigation

PurposePremature unilateral coronal craniosynostosis results in distinctive cranial and facial abnormalities of varying severity, including orbital dystopia and an abnormal head shape. As the face is affected, these children may encounter stigmatization. To avoid this scenario, many parents elect for their child to undergo surgical correction. Laypeople’s perception of children with either untreated or treated unilateral coronal craniosynostosis (UCS) has not yet been objectively evaluated.MethodsThis study introduces eye tracking as an objective instrument in order to evaluate the perception of 14 children with coronal synostosis, both pre- and postoperatively. Age-matched healthy children served as a control group. Using standardized photos, the involuntary eye movements and the fixations of 30 unaffected laypeople were evaluated.ResultsIn the untreated children, whose faces were characterized by striking orbital dystopia, the eyes drew more attention than those of the healthy children. The results of our study demonstrate that the operative correction of unilateral coronal synostosis results in the normalization of the asymmetry of the fronto-orbital region, whereas the C-shaped deformity of the midface, which is not addressed via surgery, subsequently attracts more attention.ConclusionEye tracking objectively evaluates both the perception of craniofacial abnormalities and the extent of the approximation of normality after surgical correction. We introduce eye tracking as an objective measurement tool for craniofacial abnormalities for the first time.