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In our previous test model, the abutment teeth and the model base were printed with resin and bonded with a polyether material. Some abutment teeth were fractured during the mechanical load test. Therefore, the aim was to develop and evaluate a new model under mechanical loading until fracture with zirconia FPD frameworks. At a fracture load of up to 1,636 N, neither the artificial abutment teeth nor the base model fractured. Furthermore, the artificial abutment teeth did not detach from the base model. Therefore, the model should be suitable for mechanical testing of most ceramic-based framework materials for three-unit FPDs.

Purpose: The study aimed to investigate the cooling performance of three different surgical methods for bone splitting during implant dentistry procedures., Methods: An in vitro study was conducted on bovine ribs to test the cooling performance of three osteotomy methods: conventional osteotomy with standard cooling irrigation, template-assisted osteotomy with standard cooling irrigation, and modified template-assisted osteotomy with additional cooling fluid through internal irrigation channels in the surgical guide. A negative control group without cooling was also included. Temperature measurements were taken during the procedures using a contactless infrared thermometer., Results: The results showed that the conventional osteotomy without cooling resulted in the highest mean of the peak temperatures (114.7 °C ± 45.4), while the modified template-assisted osteotomy with additional cooling achieved the lowest mean of the peak temperatures (29.4 °C ± 7). Statistically significant differences in temperature were observed among the groups (p < 0.001)., Conclusion: The study rejected the null hypothesis and demonstrated that the cooling method used during bone splitting procedures significantly affected the temperature development at the surgical site. The modified template-assisted osteotomy with additional cooling provided the best cooling performance. However, caution should be exercised in interpreting the results due to the limitations of the in vitro study. Further research with stronger external validity is needed to confirm these findings and explore their applicability in clinical settings to benefit patients., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Introduction: Infective endocarditis is a serious infection of the endocardium, especially the heart valves, which is associated with a high mortality rate. It generally occurs in patients with altered and abnormal cardiac architecture combined with exposure to bacteria from trauma and other potentially high-risk activities with transient bacteremia., (This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Introduction: Masticatory pressure increases in the distal areas of the dentition. This should be considered when restoring partially edentulous patients with a metal-free fixed partial denture (FPD). An alternative abutment preparation design can be used in order to increase the materials' volume in the most fracture-prone "connector area" of an FPD. The increased size of the connection might positively influence the constructions' mechanical durability, thereby increasing its success and survivability., Aim: The aim of the present study was to investigate the influence of two preparation designs of the distal abutment on the fracture resistance of three-unit, monolithic, ZrO2 FPDs., Materials and Methods: 3D printed replicas of a partially edentulous mandibular segment and a ZrO2, milled in full-contour, three-unit FPDs were used for this investigation. Two experimental groups (n=10 ) were defined based on the preparation design of the distal abutment tooth - classical shoulder preparation 0.8 mm deep, and endocrown preparation with a 2-mm retention cavity. The bridge - mandibular segment replica assembly was done with relyXU200(3M ESPE, USA), light-cured for 10 seconds per side with D-light Duo (GC, Europe). After cementation the test specimens were subjected to loading in a universal testing machine Zwick (Zwick-Roell Group, Germany). Statistical analysis was performed using R and includes descriptive statistics, t-test for quantitative and chi-squared test for qualitative variables., Results: The results showed no difference between the two studied groups in the maximum force required to fracture the test specimens [t=-1.8088 (17.39), p-value=0.087; P>0.05]. 95% of the fracture lines were located in the distal connector., Conclusions: Within the limitations of this study, it can be concluded that both tested preparation designs show similar results in terms of the load required to fracture the test specimens. Furthermore, it is confirmed that the distal connector is the weakest area of an all-ceramic 3-unit FPD in the posterior area., (This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The aim of this case report is to describe the combination of a surgical guide with a temporary restoration to streamline the implant process. A 54-year-old male patient presenting with partial edentulism underwent computer-aided template-guided implant placement for the replacement of the missing upper second right incisor. The presented technique was used during the surgical procedures; it introduced the integration of a surgical guide into the temporary fixed partial denture. Using computer-aided design, computer-aided manufacturing technology and virtual implant planning, a temporary-implantation fixed partial denture was constructed, and a guidance sleeve was implemented into it. The implant bed preparation was then performed using the bridge as a surgical guide. After osteotomy, the guidance sleeve within the bridge was sealed, and the bridge was temporarily incorporated for submerged healing of the implant. The use of a temporary restoration as a surgical guide seems to make the digital workflow of guided implant placement more efficient by achieving a representative clinical outcome.

Purpose: The aim of this study was to investigate to what extent cyclic load affects the screwless implant-abutment connection for Morse taper dental implants., Materials and Methods: 16 implants (SICvantage max) and 16 abutments (Swiss Cross) were used. The screwless implant-abutment connection was subjected to 10,000 cycles of axial loading with a maximum force of 120 N. For the pull-off testing, before and after the same cyclic loading, the required force for disconnecting the remaining 6 implant-abutment connections was measured. The surface of 10 abutments was examined using a scanning electron microscope 120× before and after loading., Results: The pull-off test showed a significant decrease in the vertical force required to pull the abutment from the implant with mean 229.39 N ± 18.23 before loading, and 204.30 N ± 13.51 after loading ( P <.01). Apart from the appearance of polished surface areas and slight signs of wear, no visible damages were found on the abutments., Conclusion: The deformation on the polished abutment surface might represent the result of micro movements within the implant-abutment connection during loading. Although there was a decrease of the pull-off force values after cyclic loading, this might not have a notable effect on the clinical performance., (© 2021 The Korean Academy of Prosthodontics.)

Purpose: The aim of this study was to investigate if repeated use of pilot and depth drills for implant site preparation in combination with resterilization leads to any significant changes in cutting edges or in preparation times., Materials and Methods: With drills of different lengths and widths (pilot, parallel, and tapered), osteotomies were performed under constant conditions in pig jaws. After each osteotomy, the drills were processed and sterilized. The required time for finishing the osteotomy was noted and analyzed. At the end of each osteotomy cycle, consisting of 10 osteotomies and 10 sterilizations, the cutting edge wear of the drill was analyzed using scanning electron microscopy. Unused but sterilized drills served as a control group., Results: There was no statistically significant difference in the evaluated wear between pilot drills and depth drills as well as between the test and the control group. After 60 osteotomies, implant drills showed considerable signs of wear at the major cutting edge (P > .05). Osteotomy led to a significant increase in the drilling time. While pilot drills showed an increase of drilling time of the factor 33.3, and the tapered drills of the factor 5.37, the parallel drills remained constant in their performance., Conclusion: Within the limitations of this study, it can be concluded that the process of sterilization as well as the number of performed osteotomies play a major role in the wear of the cutting edge and the performance of implant drills.

Objectives: The aim of this study is to analyze the effectiveness of screencast training videos for users from different professional backgrounds on the basis of the quality and quantity of virtual 3D implant planning as evaluated using assessment software., Methods: Participants in the study were dental students (n = 21), dental technicians (n = 16), or practicing dentists (n = 16) with no knowledge of the implant planning software CoDiagnostiX or any experience in virtual implant planning. They were randomly divided into 2 groups: The participants of the control group were presented training videos on CBCT (cone beam computed tomography) and implant planning, additional to the traditional software manual. The participants of the experimental group received, additionally, a training video on the planning software, produced in the form of a screencast. Then 3 implant planning procedures were performed by all participants. The quality of implant planning was assessed using the Treatment Evaluation Tool software, and time for planning was measured., Results: Paired sample tests showed significantly shorter planning times for the experimental groups consisting of dentists and students (P < 0.001). A comparison of the results of the individual groups reveals that students and dental technicians who had not received prior screencast training were significantly less precise in their planning (P < 0.001)., Conclusion: This study suggests a promising outcome for the future use of screencasts in the acquisition of software skills for dental software. There is a need for tools for objective self-assessment of effectiveness in software training., (© 2020 American Dental Education Association.)

Cooling irrigation during implant bed preparation is mandatory to avoid overheating. Due to the surgical guide design, external cooling systems do not reach the point of entry of the implant burr. Here, a new technique for irrigation during guided implant surgery for direct rinse of the burr is described. Using computer-aided design/computer-aided manufacturing additive technology, a pin of a cooling pipe was designed and implemented in a surgical guide template. The implant bed preparation was performed while the cooling pipe was connected to the surgical guide. During surgery, the irrigation solution was directly rinsing the burr at the point of entry through the irrigation channel. The use of a cooling surgical guide seems to improve the cooling of the bone during implant bed preparation. This might lead to less thermal effect of bone cells. However, systematic studies are needed to confirm the observations of the presented case report.

Objectives: The aim of the present clinical study was to determine the stability of color and resistance against abrasion and attrition of provisional single implant restorations., Material and Methods: A group of 16 patients were treated with provisional crowns made of Telio CAD. Shortly before the insertion the crowns were photographed and scanned using a 3D-laser scanner. After 8 weeks of clinical usage, the crowns were photographed and scanned again. The vertical occlusal wear and color changes between the restorations were measured., Results: The occlusal plane of the original crown showed a statistically significant reduction of 0.052 mm ± 0.037 mm 8 weeks after placement (p < .05). For the stability of color, a change in red, green and blue was described. All three scopes (red, green and blue) showed a statistically significant reduction (p < .05)., Conclusions: This prospective clinical study showed that Telio CAD experienced a significant occlusal reduction and color change after an intraoral placement of 8 weeks., (© 2020 The Authors. Clinical and Experimental Dental Research published by John Wiley & Sons Ltd.)

Objective: The aim of this retrospective case study was to evaluate implant placement accuracy in inexperienced clinicians with use of a surgical guide template vs the freehand method for preoperatively planned implant position., Study Design: Oral implant therapy was performed by inexperienced dental practitioners (<20 implants placed) on eligible patients after cone beam computer tomography (CBCT)-based software planning. Two patients' groups were formed according to the surgical technique: guided and freehand implant placement. The casts used for the fabrication of reconstructions were scanned by using a 3-dimensional (3D) laser scanner, the implant positions were superimposed with preoperative planning data, and the 3D deviations were calculated., Results: Twenty adult patients were included in this retrospective study (20 guided and 21 freehand implant placements). Mean calculated deviations with use of a surgical guide template were significantly lower compared with those of the freehand method with regard to angulation (P = .002), apical position (P = .002), and basal position (P = .012). No significant differences in implant placement accuracy were detected between the groups according to the implant position (premolars/molars; upper jaw/lower jaw) (P > .05)., Conclusions: Computer-aided planning and the use of surgical guides in accordance with CBCT images may help inexperienced clinicians to place implants with high accuracy., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objectives: Alveolar ridge and vertical augmentations are challenging procedures in dental implantology. Even material blocks with an interconnecting porous system are never completely resorbed. Shell techniques combined with autologous bone chips are therefore the gold standard. Using biopolymers for these techniques is well documented. We applied three-dimensional (3-D) techniques to create an individualized bending model for the adjustment of a plane biopolymer membrane made of polylactide., Study Design: Two cases with a vertical alveolar ridge defect in the maxilla were chosen. The cone beam computed tomography data were processed with a 3-D slicer and the Autodesk Meshmixer to generate data about the desired augmentation result. STL data were used to print a bending model. A 0.2-mm poly-D, L-lactic acid membrane (KLS Matin Inc., Tuttlingen, Germany) was bended accordingly and placed into the defect via a tunnel approach in both cases. A mesh graft of autologous bone chips and hydroxylapatite material was augmented beneath the shell, which was fixed with osteosynthesis screws., Results: The operative procedure was fast and without peri- or postoperative complications or complaints. The panoramic x-ray showed correct fitting of the material in the location. Bone quality at the time of implant placement was type II, resulting in good primary stability., Conclusions: A custom-made 3-D model for bending confectioned biomaterial pieces is an appropriate method for individualized adjustment in shell techniques. The advantages over direct printing of the biomaterial shell and products on the market, such as the Xyoss shell (Reoss Inc., Germany), include cost-efficiency and avoidance of regulatory issues., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objectives: We assessed the influence of a simulated diving environment on the interfacial microleakage and retentive forces of different post types in root-canal-filled teeth., Materials and Methods: One-hundred-and-twenty extracted, single-rooted teeth were endodontically treated and were randomly divided into three groups according to the post and cement used: ER Post/Harvard cement (Titanium), CeraPost/DentinBuild Evo (Zirconia), DT Light Post/Calibra (FRC). Each group was randomly divided into two equal subgroups, a control group, and an experimental group, subjected to simulated dives to 456 kPa in a diving chamber. For 10 specimens of each subgroup the pull-out strength and the coronal microleakage were measured., Results: Significant differences in the linear coronal penetration were observed between the Titanium and FRC groups (experimental group P ≤ 0.001; control group P = 0.02). Diving simulation had no significant impact on the microleakage for the three post types. The FRC groups showed significantly higher retentive strength values compared to the Titanium and Zirconia groups before and after simulated diving. The pull-out strength of the titanium experimental group was significantly less than the control group (P = 0.008)., Conclusions: Following root canal treatment the combination of fibre-reinforced posts and resin cement should be preferred for patients requiring retention for tooth restorations using posts that are likely to be exposed to hyperbaric conditions.

Purpose: The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method., Materials and Methods: An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling 5℃-55℃ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at 137℃, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture., Results: The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly., Conclusion: The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns.

Objectives: The aim of the present study was to evaluate the trend of dental practitioners in the federal state of Saarland in Germany in regard to restoring endodontically treated teeth using a Web-based survey., Materials and Methods: An interactive Web-based survey instrument was developed, including seven clinical scenarios, presented by photographs of natural incisor and premolar with different types of cavities. Following a decision tree adapted to the clinical treatment, questions on different aspects of the post-endodontic treatment were asked. All 615 members of the Saarland Dental Association (SDA) were asked to participate in the survey., Results: A total of 33 % completed the survey. The majority of the participants believed in the reinforcement effect of the ferrule design, as well as the post placement. The vast majority of the responding practitioners (92 %) adapted their treatment strategies to a high extent to the destruction degree of the endodontically treated tooth. Fiber-reinforced composite (FRC) posts are the most popular prefabricated post type, regardless of the cavity size and tooth localization. Significant differences between the dentists according to the degree of experience were detected only for the use of glass-ionomer cements as core buildup material., Conclusions: The predominant post-endodontic treatment strategies of German dental practitioners are only partly in agreement with the current literature. There is a clear trend toward the increasing use of metal-free post and core materials., Clinical Significance: Although the participants showed a general adoption of modern materials and techniques, different patterns of post-endodontic treatment were revealed that were not consistent with approaches supported by the literature.

Biosilica, a biocompatible, natural inorganic polymer that is formed by an enzymatic, silicatein-mediated reaction in siliceous sponges to build up their inorganic skeleton, has been shown to be morphogenetically active and to induce mineralization of human osteoblast-like cells (SaOS-2) in vitro. In the present study, we prepared beads (microspheres) by encapsulation of β-tricalcium phosphate [β-TCP], either alone (control) or supplemented with silica or silicatein, into the biodegradable copolymer poly(d,l-lactide-co-glycolide) [PLGA]. Under the conditions used, ≈5% β-TCP, ≈9% silica, and 0.32μg/mg of silicatein were entrapped into the PLGA microspheres (diameter≈800μm). Determination of the biocompatibility of the β-TCP microspheres, supplemented with silica or silicatein, revealed no toxicity in the MTT based cell viability assay using SaOS-2 cells. The adherence of SaOS-2 cells to the surface of silica-containing microspheres was higher than for microspheres, containing only β-TCP. In addition, the silica-containing β-TCP microspheres and even more pronounced, a 1:1 mixture of microspheres containing β-TCP and silica, and β-TCP and silicatein, were found to strongly enhance the mineral deposition by SaOS-2 cells. Using these microspheres, first animal experiments with silica/biosilica were performed in female, adult New Zealand White rabbits to study the effect of the inorganic polymer on bone regeneration in vivo. The microspheres were implanted into 5mm thick holes, drilled into the femur of the animals, applying a bilateral comparison study design (3 test groups with 4-8 animals each). The control implant on one of the two hind legs contained microspheres with only β-TCP, while the test implant on the corresponding leg consisted either of microspheres containing β-TCP and silica, or a 1:1 mixture of microspheres, supplemented with β-TCP and silica, and β-TCP and silicatein. The results revealed that tissue/bone sections of silica containing implants and implants, composed of a 1:1 mixture of silica-containing microspheres and silicatein-containing microspheres, show an enhanced regeneration of bone tissue around the microspheres, compared to the control implants containing only β-TCP. The formation of new bone induced by the microspheres is also evident from measurements of the stiffness/reduced Young's modulus of the regenerated bone tissue. The reduced Young's modulus of the regenerating bone tissue around the implants was markedly higher for the silica-containing microspheres (1.1MPa), and even more for the 1:1 mixture of the silica- and silicatein-containing microspheres (1.4MPa), compared to the β-TCP microsphere controls (0.4MPa). We propose that based on their morphogenetic activity on bone-forming cells in vitro and the results of the animal experiments presented here, silica/biosilica-based scaffolds are promising materials for bone repair/regeneration., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objectives: The objective of this in vitro study was to investigate the behavior of different composite restorative materials under the load of cast circumferential clasps for removable dental prostheses (RDPs)., Methods: In 60 human molars, standardized mesial-occlusal-distal cavities were prepared. The cavities were restored with the following materials: Definite, Tetric Ceram, SureFil, Heliomolar RO, Ariston pHc, and Oralloy, and provided with a rest seat. The rest seats were subjected to 5,000 cycles of thermal cycling and 1,200,000 masticatory cycles in a mastication simulator via cobalt-chromium circumferential clasps cast to standardized frameworks in a laboratory model designed to simulate the biomechanics of a free-end denture base. Fracture analysis of the restorations was performed by light microscopy. Before and after loading, material wear was measured with a 3D-laser scanner, and an analysis of the marginal quality was performed in an SEM at ×200 applying the replica technique., Results: No significant differences in the fracture behavior among the composite materials were found; the amalgam control group showed a significantly higher fracture resistance. Regarding the wear of the materials, the composites Definite and SureFil exhibited a behavior similar to that of amalgam. The other composites demonstrated higher wear rates. The initial marginal quality was significantly worse for Ariston pHc. The marginal adaptation decreased significantly after thermal and mechanical loading for Definite and Ariston pHc., Conclusions: In terms of the investigated aspects of mechanical performance, the tested composites seemed to be inferior to amalgam. Further clinical studies are needed to evaluate the ability of composite restorations to provide support for RDP clasps., Clinical Relevance: The use of composites as direct restoration materials should be avoided in teeth, which serve as abutments for clasp-retained RDPs.

Objective: The aim of this in vitro study was to evaluate the influence of different finishing procedures on the wear behavior of zirconia against natural enamel., Methods: 64 quadratic specimens (10 mm × 10 mm × 2 mm) were cut from a commercial hipped dental Y-TZP ceramic. Four different groups with 16 specimens each were formed according to the following finishing procedures: PZ (polished), RR (fine-grit diamond), GR (coarse-grit diamond), GZ (glazed). Polished specimens of a leucite-reinforced glass ceramic (Empress CAD) were used as a control (GC). The materials were subjected to the Ivoclar wear method (Willytec chewing simulator, 120,000 cycles, 5kg weight) with 80 natural caries-free cusps of first upper molars as antagonists. Wear was analyzed for both the enamel cusps and test specimens by measurement of the vertical substance loss with a laser scanner. Surface roughness was measured by means of a white-light interferometer., Results: The surface roughness was significantly different among the polished, diamond-finished, and glazed ceramic specimens (ANOVA, post hoc Bonferroni p<0.05). The results of the one-way ANOVA indicated that the finishing technique significantly affected enamel wear (p<0.05). The post hoc test indicated that the specimens finished with the coarse diamond caused significantly higher antagonist wear than the polished ones. Polished zirconia showed the lowest wear of the antagonist enamel, with a mean value of 171.74 (SD = 121.68), and resulted in enamel wear that was not significantly different from that of the glass ceramic control group. No significant linear correlation could be found between pre-testing surface roughness and abrasive wear., Significance: If zirconia is used without veneering material for crowns and fixed dental prostheses (FDPs), the surface must be well-polished if occlusal adjustments with coarse diamonds are performed. The polishing step reduces the wear of the opposing enamel., (Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

Objective: To investigate nursing home managers' perceptions and attitudes towards oral health care and access to dental services for aged care facility residents., Method: Questionnaires containing 28 closed-ended questions were mailed to all 114 nursing homes in Saarland, Germany. Descriptive statistics were calculated for response items., Results: Facility response rate was 39%. None of the nursing homes in this study offered systematic dental health care. Initial dental screening was carried out only in one facility. In 81%, dental examinations only took place if required. Although stationary dental equipment was available only in one home, dental treatment was carried out in 71% of the cases by a dentist in the nursing home. Eighty-four per cent of the homes' managements rated the state of the dentition of the inhabitants as satisfying. Over half of the managers indicated satisfaction with the know-how of their nursing staff concerning oral hygiene procedures. The most significant barriers to provision of dental care in the facilities according to their managers were staff shortage, lack of interest of the inhabitants and financial concerns., Conclusions: The results of this study showed an urgent need for estimating a programme for systematic dental care for institutionalised elder people in the federal state of Saarland., (© 2011 The Gerodontology Society and John Wiley & Sons A/S.)

The purpose of this study is to compare success rates of dual-viscosity impressions for two types of mixing techniques of the polyether elastomeric impression material. Additionally, influencing parameters on the success rates should be evaluated. The expectation was that there would be no difference between the success rates for the two mixing techniques. Two centres enrolled 290 subjects (727 teeth) into the trial. Patients were randomized for the two types of mixing techniques. One step, dual-viscosity impressions were made with either statically mixed Impregum Soft tray material (SAM) or dynamically mixed Impregum Penta H DuoSoft (DMM). Low viscosity Impregum Garant L DuoSoft was used for both groups. Gingival displacement involved the use of two braided cords. Full-arch trays were used exclusively. Both critical defects and operator errors were assessed for the first impression taken by trained dentists. The primary outcome was impression success. For comparison of the two mixing techniques, the odds ratio for success and the corresponding one-sided 95% confidence interval was calculated by a logistic regression model. To account for the dependence between several teeth within one patient, the method of general estimating equations was used. The overall impression success rate was 35.4%. Both mixing techniques showed equal success rates indicated by an OR of 1.0 and a lower limit of the one-sided 95% confidence interval of 0.71. Using this result to develop the corresponding interval for the difference, it could be shown that the success rate using SAM was at most 8.2% lower than that when using DMM with a probability of 95%. Multivariate logistic regression analysis of other potential influencing factors showed position of finish line (p = 0.008, supra compared to mixed), blood coagulation disorder (p = 0.021) and the level of training of the clinician (student vs dentist, p=0.008) to have an independent influence on the success rate. Dynamic mechanical mixing and the new static mixing of polyether tray material showed nearly equal success rates in the study even though success rates were comparatively low (DMM, 35.3%; SAM, 35.4%).

Objectives: The aim of this study was to evaluate the mechanical properties and the subcritical crack growth behavior of a presintered dental Y-TZP (Kavo Everest ZS) and a hot isostatic pressed Y-TZP (Kavo Everest ZH) and to perform life data analysis., Methods: For each material 150 bending bars were produced. The initial fracture strength was determined in a four-point bending test. The subcritical crack growth parameters n and A were determined in a dynamic fatigue method at four decreasing loading rates from 110MPa/s to 0.11MPa/s in distilled water at 38°C. For each loading rate Weibull statistics were performed and the Weibull moduli m and characteristic strengths σ(0) were calculated. Using these data, strength-fracture probability-life time (SPT) predictions were derived for 1 day, 1 year, 5 years and 10 years, based on a static crack growth mechanism., Results: The "hipped" Y-TZP ceramic exhibited a higher initial strength (σ(c)=1618.18), characteristic strength (σ(0)=837.15) and fracture toughness (K(IC)=4.52MPa/m(1/2)) than the pre-sintered ceramic (σ(c)=1431, σ(0)=745.46 and K(IC)=3.17MPa/m(1/2), respectively). Fatigue parameters, n and A, were 28.5 and 7.97×10(-24) for Everest ZH and 30.15 and 5.47×10(-20) for Everest ZS. The predicted fracture stress at 5% failure probability for a lifetime of 10 years was 259.34MPa for Everest ZH and 263.2MPa for Everest ZS., Conclusions: Although the "hipped" Y-TZP showed favorable initial mechanical properties, no significant difference could be found in the susceptibility of both ceramics to subcritical crack growth and their long-term strength., (Copyright © 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.)

In May-September, 1975, an outbreak of epidemic disease clinically and pathomorphologically simulating nearly all known forms of poliomyelitis occurred predominantly among young infants in Bulgaria. Most cases presented benign aseptic meningitis, sometimes with a short period of general cerebra- symptoms. Paralytic forms, such as bulbar polioencephalitis, anterior poliomyelitis, isolated pareses of the facial nerve, occasional cases of encephalomyocarditis, etc., were observed in about 21% of all cases. Over one-fourth of the paralytic cases with bulbar symptoms ended fatally. In March, 1976 another sporadic fatal case of this disease was examined. No new cases occurred in 1977. Histopathological examinations in all fatal cases regularly revealed lesions in the grey matter of the medulla and spinal cord typical of acute anterior poliomyelitis and bulbar polioencephalitis, with some peculiar features of localization and depth of the involvement of the brain stem. The similarity to poliomyelitis and precariously rapid increase in the incidence led to the decision to urgently vaccinate the entire human population with Sabin's live poliovirus vaccine simultaneously in the whole country in order to produce interference with the circulating agent. This aim appeared to have been achieved partially because soon the number of new cases of the disease began to decrease; however, no sharp and complete break in the curve of the incidence occurred. By the time of mass vaccination, the results of virological examinations started before were not yet available. Later, comprehensive complete evidence was obtained that over 25 fatal and many other typical cases of the disease were associated with an enterovirus proved to be antigenically related to enterovirus 71. The diseases in Bulgaria, 1975, differ considerably in the frequency of paralytic forms and in severity from the epidemics caused by enterovirus 71 in Sweden, 1973, Australia, 1972--1973, USA, 1969--1972, and Japan, 1972--1973.