International Poster Journal of Dentistry and Oral Medicine, 03/2009

Objectives: The study was focused on stress areas evaluation, induced in RPD laser welded frameworks, on the purpose of determining the durability of prosthesis rehabilitations. Material and Methods: For testing, there were used 2 types of laser welding with filling material for CoCrMo alloys (WIRONIT-BEGO, "C" VASKUT KFT) in RPD technology. In order to realize a thermal analysis with finite elements and reveal the welding residual stress, specific software (solid work 2007) was used. This analysis serves to welding procedure simulation, in which temperature, heat flux distribution and static analysis of stress state, resulting from welding, were under observation. The following thermal parameters resulted for evaluation: coefficient of linear expansion-ß=3,36•105 W/mm2•°C, coefficient of heat conductivity-λ=6,05•10-2W/mm•°C; specific heat-C=434 J/Kg•°C. Results: The Study results reveal that around the fusion zone there is a stress gradient, and this is the one that forms cracks in the fusion zone in steel. The thermal calculation applied in the rib is analyzed in connection with temperatures distribution during welding and cooling. This consists in temperature field's distribution on a period of 1-5s. Analysing the stress field of numerical simulated longitudinal section, the high values of stress from the heat affected zone and their orientation towards the welding exterior surface, where cracks usually appear, can be observed. Conclusion: The study with finite elements has the advantage of being non-invasive and of permitting a correct prognosis of cracks appearance zones in the heat affected zone. Welding is a useful method for metallic prostheses repairs and for the control of welding heat input, contributing to the decrease of welding stress and to the avoidance of cracks. Schlagwörter: residual tension states, CoCrMo alloys, laser welding

The sucessful incorporation of extracorporally engineered tissue into critical size bone defects (CSD) entails an optimal compound of a tissue matrix and the incorporated specific cell types. The aim of this study was the development of a primary vascularised implant construct on the basis of a fibrin matrix and autologeous cells and tissue components to restore CSDs ad integrum. For this reason fibrin matrices were engineered from veneous blood from Göttinger minipigs using the Modidified Critical Point Dry (MCPD) - method and stored at - 20° Celsius for further use. Osteoblast were gathered from the periost of the scull while the endothelial cells were cultured from jugular veins of the pigs. The defrosted matrices were incubated with the cells an controlled in vitro for proliferation, adhesion and differentiation using histological, immunohistological and ultrastructural techniques. In vivo constructs of three incubated matrices were sandwich-like incorporated in artificial CSD. Bone regeneration was controlled at specific times after 3,7 and 14 days past incorporation again using histological, immunohistological and ultrastructural techniques. In vitro both cell lines showed a clear adhesion on the matrix only few hours after colonization and increased proliferation with confluent cell layers after 3 days. Osteoblast proved an increased expression for extracellular matrix proteins while the endothelial cells started to build cyclic structures after confluence and cell-to-cell contacts. The in vivo results a condensed, accelerated regeneration in the CSD with endothelial sprouting into the defects after 3 days and osteous mineralisation areas in the fibrin network. 14 days past incorporation the CSDs were nearly completely filled with new bone formation. The bone regeneration in the MCPD-Fibrin sprouted twice as fast as in the controll groups. Regarding the results of the study fibrin is an ideal matrix for solely outologeous bone tissue engineering with precise advantages concerning cell behaviour an defect incorporation in comparison to alternative constructs. Schlagwörter: autolog, tissue engineering, fibrin, angiogenesis, osteogenesis, osteoconduction

IntroductionPrecision slide attachment could be successfully used as the retainer for RPD, providing beneficial axial loading. Regardless restorations opposed by a denture, where one single tooth on each side of the arch would be needed as a retainer, in the case where bony support of abutment could be compromised 3, or more abutment teeth have to be included in design on each side. The aim of this study is to present prosthetic rehabilitation of partially edentulous patient by mandibular cobalt-chrome partial denture with non-adjustable intracoronal slide attachments and upper CD. Schlagwörter: slide-attachment, denture, partiallyedentulous, patient

A distinguishing feature of Ni-Cr alloys is that their properties are developed by heat treatments. Purpose: The aim of the study was to evaluate the effect of pre- and post-weld heat treatments on Ni-Cr dental alloys. Materials and Methods: Plates of different Ni-Cr alloys were cast conventionally. Half of them were slowly and half were rapidly cooled. The plates were microplasma welded and half of them were heat treated. They were analyzed macroscopically, metallographic, and the microhardness was determined in the base metal (BM), weld metal (WM) and heat affected zone (HAZ). Results: The dendritic microstructure of the BM became finer and the microhardness increased after heat treatments. Metallographic analyses showed fewer cracks along the joining line for the pre-weld heat treated samples. Conclusion: The composition of the Ni-Cr alloys is decisive for their behavior to heat treatments. Schlagwörter: heat treatment, microplasma welding, Ni-Cr alloys

Due to the increasing incidence the diagnosis and therapy of osteomyelitis, especially in the subacute and chronic form is an great challenge for todays medicine. So far there is no scheme for the classification of the different osteomyelitis forms and the resulting possible therapies. The aim of this study was the quantitative analysis of T-cells and their subpopulations als well as macrophages as part of the cell-mediated immunity in osteomylitic bone tissue from biopsies taking from 15 patient suffering from different forms of osteomylitis using monoclonal antibodies for CD3, CD45RO, CD8 and CD68. The results showed that the percent of positiv marked cell compaired to the total ammount of immunocompetent cells varied with CD45R0 22%, CD3 mit 13%, CD68 5,2% and CD8 3,0%. Overall the biopsies proved a significant higher expression of secondary antibodies than the controll group. The literature gives no clear evidence for a precise immunological reaction scheme of the human body suffering from osteomyelitis. Looking at our results we suggest a irregular and increased immun reaction leading to a permanent dysregulation of activator-inhibtor-schemes caused by autoimmunological processes. This might keep up a persistent osteomyelitic reaction of the bone. Further studies should therefore concentrate on the quantification of T-Helper-cells. Schlagwörter: Osteomyelitis, Immunhistologie, Differenzierung

In dentistry, three-dimensional reconstructions after computed tomographies are used in traumatology and implantology. The aim of the study was to achieve three-dimensional reconstructions after computed tomographies, in order to obtain faithful models which can be used for numerical simulations of the teeth and prosthetic restorations. Because of the small dimensions and high complexities used in dentistry, it was necessary to obtain enlarged radioopaque models. Axial slices of 1 mm were made. Resulted images were transformed into curves and these in point clouds. The points were used to get a network and than for surfaces and solids, necessary for numerical simulations. The faithfulness of the solids depends on the structural complexity, the aggrandizement degree and the images processing procedures. Three-dimensional reconstructions of complex prosthetic restorations is difficult to obtain using computed tompographies. Schlagwörter: three-dimensional reconstructions, computed tomographies, teeth, prosthetic restorations

Full denture casting currently represents a technological alternative. The Vertex casting system, which uses reversible hydrocolloids for investing wax patterns, was applied. Besides the system's own advantages, the authors also noticed certain errors consecutive to casting, materialized in lack of substance and the development of porosities on the mucosal facets of the complete denture bases. Schlagwörter: casting, full dentures, errors

The aim of the study was to evaluate the influence of the stud attachments components dimensions on their strength using the finite element analysis.Purposely designed resilient ball and socket stud type attachments were modeled in order to be exported for numerical simulations. The parameters like ball diameter and female insert width were varied. Generated stresses and displacements were calculated numerically and plotted graphically. High stresses were present on the upper surface of the resilient female insert. Regarding the stresses in the metal ball, they are present around the neck and on their top. In the metal housing high stresses were located around the balls greatest circumference. The described methods can generate experimental models, which can be used to select the preferable attachment size. Schlagwörter: finite element analysis, stud type attachments, stresses

Background: Numerous studies point to an association between periodontal and cardiovascular diseases. The results, however, are not consistent. Genetic factors of host response and the influence of periodontal pathogens have not sufficiently been investigated although they might be responsable for the mentioned discepancies. The aim of this study was to examine the prevalence of periodontal pathogens and polymorphisms in the interleukin-1 (IL-1) gene cluster in patients after acute myocardial infarction (AMI). Material and Methods: In 54 patients with AMI (35-50 years) and 50 healthy probands (36-61 years) the following parameter were recorded: periodontal probing depth (PD), clinical attachment level (CAL), bleeding on probing (BOP), plaque index (PI) and gingival index (GI). In all patients and controls subgingival plaque samples were analysed for periodontal pathogens Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf) and Prevotella intermedia (Pi) using dot blot hybridisation. Further, in 39 AMI patients and 50 controls allele frequencies of IL-1A, IL-1B and IL-1RN were examined using PCR with reverse hybridisation. Results: In patients with AMI all periodontal parameters (PD, CAL, BOP, PI, GI) were significantly higher than in healthy controls. Among different cut-off levels, the frequency of more than 50% sites with PD >= 4 mm showed the highest discrepancy between both groups (33% vs. 0%, p50% PD >= 4 mm) versus without (= 4 mm) generalized periodontitis had two different IL-1-haplotype patterns. Conclusions: The results confirm the association between AMI and periodontitis. A.a. and P.g. might be risk indicators for AMI. Two different IL-1 haplotypes may explain previous discrepancies in the association between cardiovascular diseases and periodontitis. Schlagwörter: periodontitis, myocardial infarction, interleukin-1

A sucessfull integration of a bone transplant gained from tissue engineering depends largely on a sufficient angiogenesis. While the effect of severel substances on angiogenetic processes has been studied thoroughly, the influence of hormonal anticontraceptives (OC) like estrogen an gestagen has so far been neglected. On grounds of the increasing use of natural and synthetic contraceptives the aim of this study was the examination of the the influence of different gestagen derivates in oral contraceptives on the proliferation of human endothelial cells. Therefore human umbilial endothelisl cells (HUVEC) were gained using standard techniques and incubated with different combnations of ethinyl-estrogen (EE), gestagen and EE plus gestagen. The gestagen were 3 nortestosteron derivates (norethisteron-acetate, levonorgestrel, desogestrel) and one 17-alpha-hydroxyprogesteron derivat (Chlormadinon-Acetat) applied in 1 hour aquivalent doses. After 24 and 72 hours the proliferation of the endothelial cells was controlled photmetrically in size and ammount. The results showed that oral contraceptives (OC) have an effect on angiogenesis. While some contens can increase the angiogenetic process others block it. The used progesterone derivate seemed to have an different effect on the endothelial cells. All tested combinations had an decreasing effect on the cell number,only EE and EE+ norethistosterone acetate showed larger number in the cell count compared to the control. Apart from EE with smaler cell diameter, all other combinations showed an increased diameter of the endothelial cells, in comparison with the control group. As only a few gestagens and their combination could be investigated in this study further investigation have to enlarge the ammount of data. Anyhow the study showed thatOC have an influence on angiogenesis which can effect incorporation of implants and healing processes. Schlagwörter: angiogenesis, oral contraceptives, ethinyl estrogen, norethistosterone acetate, levonorgestrel, desogestrel

For patients requiring aesthetic restorations, ceramic inlays provide durable alternatives to posterior composite resins. It is important to ensure optimal performance in selection of the adequate preparation design to reduce stresses and their susceptibility to fracture. Purpose: The aim of the study was to develop 3D finite element models of molars with different preparations, restored with inlays, in order to evaluate and compare stress distributions under occlusal loads. Material and Methods: Thirteen 3-D models of first upper molars of the same shape and size were created: an intact tooth; six unrestored teeth with class II cavity preparations with different tapers (between 0 and 10Ί); the same six teeth restored with ceramic inlays. The geometries of the teeth were constructed by 3D scaning using a manufactured device. These were exported in Ansys finite element analysis software (Ansys Inc., Philadelphia, USA), to be used for structural simulations. In making the finite element models, the characteristics of the materials used for the restorations were entered into the computer program. Each model was subjected to a force of 200 N directed to the occlusal surface. Stresses were calculated in the tested inlays, and tooth tissues. Results: In the teeth restored with ceramic inlays, the von Mises equivalent stress values were higher than in the intact tooth. High stresses were located at the junction of the butt joint margin inlay and enamel. The values depend on the preparation shape and decrease with the increase of the taper. Conclusion: The study provides a biomechanical explanation for inlays restored teeth. Ceramic inlays do not restore the original strength of the teeth, but the preparation shape is decisive for the stress values and distribution. Schlagwörter: ceramic inlays, 3D models of molars, stress distribution, finite element analysis