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The purpose of this study was to evaluate the fit, fracture load and aging resistance of the monolithic zirconia tooth-borne crowns with conventional and high-speed sintering.The Y-TZP block was machined and sintered with conventional and high-speed sintering furnace. The marginal and internal gap between the crown and abutment was measured using a microscope and a fit checking material. A total of 28 crowns were further divided into an undegraded and a degraded group. An accelerated aging test was carried out on the degraded group. The crown was cemented and a fracture resistance was tested. X-ray diffraction was used to evaluate the crystalline structure. The data were analyzed with Student's t-test, and a one-way ANOVA and Tukey's multiple comparison test.There was no significant difference in mean marginal gap between the two groups. The mean internal gap was significantly greater in the speed sintering than in the conventional sintering (P0.001). The mean fracture load of the conventional sintering crowns was not significantly different from that of speed sintering crowns after aging. The occurrence of monoclinic crystals of degraded crown was significantly higher than that of undegraded crown both in the conventional (P0.001) and speed-sintering group (P0.001).It was concluded that the monolithic zirconia crowns produced by high-speed sintering showed no significant difference in the marginal gap and the fracture load after aging compared to conventional sintering. Therefore, the high-speed sintering seems a valid method of producing tooth-borne monolithic zirconia crowns.

In this paper, the new local approach model (NLAM) is first adopted to predict the cleavage fracture probability-load curves of notched round bar tensile specimens of ferritic steel 20MnMoNi55 at the temperatures of 123 K and 223 K. Then, based on the obtained curve, the probability density function, and the extreme value theorem of function, two significant cleavage fracture probabilities are proposed. Finally, the proposed probabilities are employed to predict the load which is most likely to cause cleavage fracture of 20MnMoNi55 steel. The results show that when the value of cleavage fracture probability is 45.29%, the corresponding predicted load is basically equal to the average fracture load of the specimens. Besides, the load corresponding to the cleavage fracture probability of 59.7% is the most likely one to induce cleavage fracture of the structure.

To determine the effect of veneering material and framework design on fracture loads of implant-supported zirconia molar fixed dental prostheses (FDPs).Sixty-six zirconia FDPs were manufactured onto two implants and classified as uniform thickness (UT) or anatomic design (AD). These framework design groups were then further divided into three subgroups (n=11): feldspathic porcelain-veneered zirconia FDPs (PVZ), indirect composite-veneered zirconia FDPs (IVZ), and metal-ceramic FDPs (MC). The FDPs were luted on the implant abutments and underwent fracture load testing. Significant differences were assessed by the Kruskal-Wallis test and Mann-Whitney U-test (α=0.05).For UT group, median fracture load was significantly higher for the IVZ (1.87kN) and MC (1.90kN) specimens than for the PVZ specimens (1.38kN) (p0.05). In the AD group, the IVZ specimens had the highest median fracture load (4.10kN) of the three groups tested. The AD group exhibited higher median fracture loads than the UT group in all subgroups.Indirect composite appears to be a useful alternative to feldspathic porcelain as the layering material for implant-supported zirconia FDPs. The AD group had higher fracture loads than UT group. In addition, implant-supported indirect composite-veneered zirconia-based FDPs appear to be clinically feasible.

Indirect CAD/CAM restorations can be fabricated using both subtractive and additive CAD/CAM technology. This study investigated the fracture load of crowns fabricated from three particle-filled composite CAD/CAM materials and one 3D-printed composite material. Lava Ultimate, Cerasmart and Brilliant Crios were used as particle-filled composite CAD/CAM material and els-3D Harz as 3D-printed composite material. For each group, crowns with three different material thicknesses (0.5/1.0/1.5 mm) were fabricated. Control group was composed of ceramic-based CAD/CAM materials e.max CAD and Enamic. Totally, n = 180 crowns were fabricated and adhesively seated on SLA fabricated dies. Thermomechanical loading and fracture testing were performed. The data for fracture loading force were statistically analyzed by two-way ANOVA followed with multiple comparisons by post hoc Tukey’s test (α = 0.05). In contrast to ceramics, all particle-filled composite crowns with 0.5-mm thickness survived fatigue testing. Forces varied statistically significantly. Brilliant Crios showed highest maximum loading force with 1580.4 ± 521.0 N (1.5 mm). Two-way ANOVA indicated that both the material and the thickness affected the fracture load (p

Objectives This study aims to evaluate the fracture load of differently fabricated 3-unit posterior fixed dental prostheses (FDPs) with an intermediate pontic. Methods Fifty sets of two stainless-steel abutments were randomly assigned to five groups (n = 10 each) depending on the material and technique used for manufacturing the FDPs: (1) Metal-ceramic (MC, control); (2) Lava Zirconia (LZ, bi-layered); (3) Lava Plus (LM, monolithic); (4) VITA In-Ceram YZ (YZ, bi-layered); and (5) IPS e-max ZirCAD (ZZ, bi-layered). After being luted to the dies, all FDPs were submitted to thermo-mechanical cycling (120,000 masticatory cycles, 50 N; plus 774 thermal cycles of 5 °C/55 °C, dwell time: 30 s). Samples were then subjected to a three-point bending test until fracture in a universal testing machine (cross-head speed: 1 mm/min). Fracture load of the veneering ceramic (VF) and total fracture load (TF) were recorded. Microstructure and failure patterns were assessed. Data was analysed using one-way ANOVA and Tukey HSD post-hoc tests (α = 0.05). Results MC restorations recorded higher VF and TF values than did zirconia FDPs (p = 0.0001), which showed no between-group differences. Within the bi-layered groups, TF was significantly higher than VF. LM pieces registered lower average grain size than did LZ specimens (p = 0.001). Overall, the connector was the weakest part. Conclusions All of the groups tested could withstand clinical chewing forces in terms of average fracture load. Zirconia-based samples performed similarly to each other, but showed lower mean fracture load values than did metal-ceramic ones. Clinical significance Monolithic zirconia may be recommendable for solving the chipping problem.

Aim: The use of colored translucent zirconia may enable restorations of a more natural tooth-like appearance than previous opaque white zirconia. The shift from non-colored to colored zirconia may however entail a risk of reduced strength. The aim of the present study was to compare fracture load and fracture mode of fixed dental prostheses frameworks made of colored translucent zirconia to that of non-colored controls. Methods: A total of forty three-unit FDP frameworks were manufactured from two different high translucent zirconia materials (Zenostar, Wieland Dental, and DD cubeX2, Dental Direkt). Each group contained two subgroups, one colored and one non-colored. Coloring was performed before final sintering using two different infiltration techniques. All FDPs underwent an artificial aging process in the form of heat treatment, thermocycling and preloading whereafter the specimens were subjected to load until fracture. Fracture load and mode was registered. Results: For one of the zirconia materials, Zenostar, the non-colored frameworks showed significantly higher fracture loads (p .05) was found between colored and non-colored frameworks in the other zirconia material, DD cubeX2. All FDPs fractured through the connector. Some fractures ran through the mesial and some through the distal side of the connector but there were no significant differences in fracture mode between groups. Conclusion: Coloring before sintering of high-translucent zirconia may decrease the fracture load of FDP frameworks for certain materials and techniques. Fracture mode however, does not appear to be affected.

Enhanced direct Cu/Cu joining by applying current was investigated. Joining was conducted at 240–300 °C for 10–50 min under 40 MPa. Current was applied to Cu wire during joining. Contact resistance of joints decreased and the fracture load of joints increased as the current increased. The joined region increased and the interface became less straight as the current increased. These results are ascribed to electromigration and joule heating effects. The enhanced diffusion contributed significantly to the joining of metals.

Three experimental glass fiber posts (EGFP) based on 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl] propane, triethyleneglycol dimethacrylate monomers, and alkaline-resistant (AR) glass fibers were obtained. The EGFP as well as 29 commercial endodontic posts were investigated for fracture load, force load at upper yield, and filler content. Each post was loaded at a 135° angle to the root's long axis using a universal testing machine, and the maximum strength was recorded. EGFP showed the fracture load values from 68.02 to 115.97 N, and the force load at upper yield values from 38.70 to 70.46 N. The filler content of the EGFP ranged between 49.64 and 62.67 vol%. EGFP showed mechanical strength comparable to other posts already on the market. A polymer matrix based on bis-GMA/TEGDMA and AR glass fibers could be an alternative to epoxy resin and glass fibers from commercial endodontic posts. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

The aim of the current investigation was to evaluate the fracture resistance of one-piece zirconia oral implants with and without all-ceramic incisor crowns after long-term thermomechanical cycling. A total of 48 implants were evaluated. The groups with crowns (C, 24 samples) and without crowns (N, 24 samples) were subdivided according to the loading protocol, resulting in three groups of 8 samples each: Group “0” was not exposed to cyclic loading, whereas groups “5” and “10” were loaded with 5 and 10 million chewing cycles, respectively. This resulted in 6 different groups: C0/N0, C5/N5 and C10/N10. Subsequently, all 48 implants were statically loaded to fracture and bending moments were calculated. All implants survived the artificial aging. For the static loading the following average bending moments were calculated: C0: 326 Ncm, C5: 339 Ncm, C10: 369 Ncm, N0: 339 Ncm, N5: 398 Ncm and N10: 355 Ncm. To a certain extent, thermomechanical cycling resulted in an increase of fracture resistance which did not prove to be statistically significant. Regarding its fracture resistance, the evaluated ceramic implant system made of Y-TZP seems to be able to resist physiological chewing forces long-term. Restauration with all-ceramic single crowns showed no negative influence on fracture resistance.

Objective The aim of the study was to evaluate the thermomechanical behavior of alumina-toughened zirconia (ATZ) oral implants in the artificial mouth and the fracture resistance (fracture load and bending moment) in a subsequent static fracture load test. The effects of abutment modification and different cyclic loadings were evaluated. Methods A total of 48 implants were used. 24 implants were left as machined (Group A), and 24 implants were shape modified at the abutment (Group B). Groups were divided into three subgroups composed of 8 samples each (A1/B1: no cyclic loading; A2/B2: 1.2 million cycles; A3/B3: 5 million cycles). Subsequently, all implants were statically loaded to the point of fracture. Results The implants showed the following survival rates after the artificial mouth: A2 and B2 100%; A3 and B3 87.5%. The following average fracture resistance values were found (fracture load [N]/bending moment [N mm]): A1 (583/2907), B1 (516/2825), A2 (618/2737), B2 (550/3150), A3 (802/3784) and B3 (722/3809). After 5 million loading cycles a significant increase in fracture load and bending moment was found. Modification of the abutment significantly decreased the fracture load of implants without foregoing dynamic loading. However, the shape modification altered the lever arm. For that reason, a smaller load resulted in the same bending moment. Therefore, abutment modification had no significant influence on the fracture resistance of ATZ. Significance Neither thermomechanical cycling in an aqueous environment nor modification of the abutment had a negative effect on the fracture resistance of ATZ.

Low alloyed high strength steels with yield strength above 1200 MPa are increasingly implemented for the reduction of the component weight in the automotive industry. This material type is known for its susceptibility to hydrogen assisted cracking. Both, manufacturing process induced and hydrogen induced embrittlement during component operation have to be considered. The aim of this study was to evaluate the impact of different zinc-containing topcoats on hydrogen re-embrittlement. The susceptibility of high strength fasteners (strength class 12.9) with various zinc-based topcoats (electroplated zinc, electroplated zinc-nickel, galvanized zinc and zinc-flake) were tested under various corrosive environmental conditions. It is shown that the zinc-containing topcoats impose a different susceptibility on hydrogen re-embrittlement. Under the tested environmental conditions, fasteners with electroplated zinc revealed a decrease in the fracture load compared to the heat treated black specimen. In contrast to that, an electroplated zinc-nickel topcoat demonstrated a failure at the loads slightly exceeding the fracture load of the uncoated specimen. Hochfeste Stahle mit einer Zugfestigkeit von uber 1200 MPa werden aufgrund ihres Leichtbaupotenzials beispielsweise in der Automobilindustrie zur Gewichtsreduzierung eingesetzt. Bedingt durch die Festigkeitseigenschaften besitzt diese Werkstoffgruppe allerdings per se eine gewisse Anfalligkeit gegenuber dem Schadensmechanismus der wasserstoffinduzierten Rissbildung (fertigungs- als auch betriebsbedingt). Ziel dieser Arbeit war es den Einfluss zinkbasierter Deckschichtsysteme auf das korrosionsbedingte Wasserstoffgefahrdungspotenzial zu untersuchen. Die Anfalligkeit einer hochfesten Schraube (Festigkeitsklasse 12.9) mit unterschiedlichen Zinkuberzugssysteme (galvanisch Zink; galvanisch Zinknickel, thermisch Zink und Zinklamelle) wurde unter verschiedenen korrosiven Bedingungen ausgelagert. Unter den getesteten Bedingungen konnte gezeigt werden, dass die Deckschichtsysteme einen Einfluss auf das korrosionsbedingte Wasserstoffgefahrdungspotenzial ausuben. Verglichen mit einer unbeschichteten Schraube erhohen die Deckschichtsysteme galvanisch Zink sowie thermisch Zink das korrosionsbedingte Wasserstoffgefahrdungspotenzial. Dahingegen konnte fur die Systeme Zinknickel sowie Zinklamelle kein negativer Einfluss festgestellt werden.

Handgun bullets fired toward the windshield of an automobile sometimes ricochets. In such a case, we must estimate the type of bullet and direction of shooting from the damaged windshield. The purpose of this study is to obtain a method to estimate the fired direction of a handgun bullet from the fractured windshield. We test fired bullets to an automobile windshield with various incidence angles. The thickness of the windshield is slightly different from model to model of the automobiles. In the beginning, we examined the strength of the automobile windshield of various car models. First, we examined the static failure strength of the windshield by an indentation test. In this test, fracture load and the amount of indentation were measured on windshield samples cut from ten models of Japanese automobiles. Next, we test fired a handgun in order to examine the relation between the trajectory of a bullet and the collision marks on the windshield. The cartridges used in these test firings were 38SPL. lead round nose (LRN) bullet and full metal cased (FMC) bullet. In the results of static indentation test for different car models, there was found to be almost no differences in the relationship between fracture load and indentation depth. With the LRN bullet, bullets perforated the windshield when the incidence angle was less than 45 degrees and ricocheted when the incidence angle was greater than 60 degrees. In these cases, a characteristic damage was left on the windshield. On the other hand, FMC bullets of 38SPL. perforated the windshield when the incidence angle was less than 60 degrees and ricocheted when the incidence angle was greater than 70 degrees. Based on these results, we proposed a method to estimate the direction of shooting in criminal cases in which a bullet was fired on an automobile windshield.

Four-channel α-Al 2 O 3 ceramic hollow fibers were first fabricated by a combined phase-inversion and sintering technique. The hollow fibers could provide low transport resistance as well as high mechanical strength. Influences of air gap and sintering temperature on properties of the obtained hollow fibers were investigated. Using an air gap of 100 mm and a sintering temperature of 1450 °C for 5 h, the as-prepared four-channel fibers with the cross-linking configuration showed a pure water flux of 1.93 m 3 m −2 h −1 at 0.1 MPa and a fracture load of 18.5 N, which was superior to that of single-channel ceramic hollow fiber. It is suggested that the four-channel ceramic hollow fibers exhibit great potential for practical applications.

This study investigated the influence of different surface treatments on fracture load (FL) of canine crowns fabricated from two different pressable lithium-disilicate ceramics: A (HS10PC, estetic ceram, n=180) and B (IPS e.max Press, IvoclarVivadent, n=120). The standardized specimens were divided into groups of six different surface treatments and two glazing temperatures. A-group specimens were additionally assigned two glazing pastes with various thermal expansion coefficients (TEC). FL was measured and TECs were determined. Data were analyzed using three/one-way ANOVA followed by post-hoc Scheffe's test. B showed comparable or higher FL than A (B: 503-876 N; A: 375-734 N). Lithium-disilicate crowns show higher FL when not grinded but only polished or glazed. Glazing pastes affected FL depending on their TECs, firing temperature and crown treatment. TEC of A and B was 10 ppm/K, glazing pastes for A presented TECs of 7.5 ppm/K and 10 ppm/K and for B of 9 ppm/K.

Objective: To evaluate the fracture resistance of endodontically treated teeth reinforced with cast titanium posts and prefabricated glass-fiber posts with different diameters. Materials and Methods: 50 recently extracted human maxillary central incisors were endodontically treated and randomly divided into 5 groups of 10 specimens each: Group A: 1.35mm diameter of cast titanium post; Group B: 1.5mm diameter of cast titanium post; Group C: 1.375mm diameter of prefabricated fiber post; Group D: 1.5mm diameter of prefabricated fiber post; Group E: resin restoration. All specimens were subjected to fracture resistance testing in a universal testing machine, statistical analysis was performed and the fracture modes were analyzed. Results: The mean fracture resistance of five groups as follows: 404.22±73.92N for group A, 488.17±78.68N for group B, 280.32±45.23N for group C, 317.53±50.87N for group D, 222.76±38.67N for group E. The fracture resistance of restored teeth between group C and group D had no significant difference (P>0.05). The fracture resistance of the rest pairwise group comparisons had significant difference (P

Objective: This study aimed to evaluate the fracture load of endocrown restorations and fiber-reinforced composites (FRCs) fabricated through computer-aided design/computer-aided manufacturing (CAD-CAM) for post–cores of anterior teeth. Materials and Method: Forty post–core-supported crowns and endocrowns were fabricated through CAD-CAM on a canine root zirconia model (Ice Zirconia, ZirkonZahn GmBH, Bruneck, Italy). The static load-bearing capacity was measured on the following restoration groups: Group 1: zirconia crown (Prettau anterior, ZirkonZahn GmBH) retained with CAD-CAM one-piece FRC post-core crown system (experimental CAD-CAM FRC block); Group 2: zirconia crown (Prettau anterior) retained with FRC post (GC Corp., Tokyo, Japan) with discontinuous fiber composite (EverX posterior, GC Corp) core; Group 3: zirconia endocrown (Prettau anterior); and Group 4: lithium disilicate ceramic endocrown (IPS e.max CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein) (n = 10/per group). After the adhesive cementation of crowns/endocrowns to the zirconia root model, a load was applied at 45° to the long axis of the teeth and measured using a universal testing machine. The fracture modes were visually examined. The statistical analyses were performed using one-way ANOVA and Tukey post-hoc tests (p < 0.05). Results: The fracture load significantly differed among the groups (p < 0.05) and was ranked as follows: Group 3 (1168 ± 141 N) > Group 4 (721 ± 96 N) ≥ Group 1 (680 ± 86 N) > Group 2 (534 ± 36 N). Conclusion: Endocrown monoblock restorations can be used as an alternative to fiber-reinforced post–core supported crown restorations.

This study evaluated the effect of zirconia framework design on fracture load of implant-supported zirconia-based prostheses after thermal cycling and mechanical loading. Three different zirconia framework designs were investigated: uniform-thickness (UNI), anatomic (ANA), and supported anatomic (SUP) designs. Each framework was layered with feldspathic porcelain (ZAC group) or indirect composite material (ZIC group). The specimens then underwent fracture load testing after thermal cycling and cyclic loading. In the ZAC group, mean fracture load was significantly lower for UNI design specimens than for the other framework designs. In the ZIC group, there was no significant difference in mean fracture load between ANA design specimens and either UNI or SUP design specimens. To improve fracture resistance of implant-supported zirconia-based prostheses after artificial aging, uniformly thick layering material and appropriate lingual support with zirconia frameworks should be provided.

PURPOSE To investigate the effect of reducing tooth preparation and ceramic thickness on fracture resistance of lithium disilicate crowns. MATERIALS AND METHODS Specimen preparation included a standard complete crown preparation of a typodont mandibular left first molar with an occlusal reduction of 2 mm, proximal/axial wall reduction of 1.5 mm, and 1.0 mm deep chamfer (Group A). Another typodont mandibular first molar was prepared with less tooth reduction: 1 mm occlusal and proximal/axial wall reduction and 0.8 mm chamfer (Group B). Twenty crowns were milled from each preparation corresponding to control group (n=5) and conditioned group of simultaneous thermal and mechanical loading in aqueous environment (n=15). All crowns were then loaded until fracture to determine the fracture load. RESULTS The mean (SD) fracture load values (in Newton) for Group A were 2340 (83) and 2149 (649), and for Group B, 1752 (134) and 1054 (249) without and with fatigue, respectively. Reducing tooth preparation thickness significantly decreased fracture load of the crowns at baseline and after fatigue application. After fatigue, the mean fracture load statistically significantly decreased (P.05) in Group A. CONCLUSION Reducing the amount of tooth preparation by 0.5 mm on the occlusal and proximal/axial wall with a 0.8 mm chamfer significantly reduced fracture load of the restoration. Tooth reduction required for lithium disilicate crowns is a crucial factor for a long-term successful application of this all-ceramic system.

Several of the most popular scratch and mar test methods and their scratch failure mechanisms are reviewed. These include Crockmeter-2 μm, Crockmeter-9 μm, Amtec Kistler Car Wash, and Nano Scratch. Plastic deformation is identified as the primary failure mechanism for the Crockmeter tests, but fracture type scratches are more associated with Amtec Kistler Car Wash test. Nano Scratch quantitatively measures both plastic deformation and fracture load. From the coating design perspective, crosslink density and chain elasticity are the most important factors for scratch and mar resistance. Higher crosslink density is correlated to lower plastic deformation, while higher chain elasticity results in higher fracture threshold. Aging of polyisocyanate type coatings helps scratch and mar resistance due to postcure reaction from the isocyanate residual groups. Weathering hurts scratch and mar resistance due to network degradation. For technology comparison, two-component (2K) isocyanate was superior in comparing to one-component (1K) acrylic melamine due to its better weathering resistance. Impact of nanoparticles on scratch and mar resistance appeared to be related to the cluster formation of the particles. The tightly clustered nanoparticles appeared to improve scratch and mar resistance through arresting the propagating fronts of cracks initiated during the scratching process.

Estimating the risk of osteoporotic fractures is an important diagnostic step that needs to be taken before medicinal treatment. Densitometry-based criteria are normally used in clinical practice for this purpose. However, densitometry-based techniques could not explain all low-energy fractures. As patient-specific finite element (FE) models allow for consideration of other parameters (e.g. load conditions) that are known to be associated with fracture, they are considered promising candidates for more accurate fracture risk estimation. Nevertheless, they are often time consuming, expensive, and complex to build and may need the type of expertise that is not normally available in clinical settings. In this study, we report the development of an automated platform for estimating proximal femur fracture loads using patient-specific 2D FE models generated using dual-energy x-ray absorptiometry (DXA) scans. First, a statistical shape and appearance model (SSAM) is built using DXA scans of patients screened for osteoporosis following a low energy fracture. SSAM is then used together with Active Appearance Models (AAM) for automated segmentation of the proximal femur from new unseen DXA scans. The mean point-to-curve error of the automated procedure, i.e. 1.2-1.4 mm, is shown to be only slightly larger than the intra-observer variability of manual segmentation, i.e. 1.0 mm. Moreover, the developed platform automatically meshes the segmented shape, assigns density-based mechanical properties, assigns loads and boundary conditions, submits the 2D FE model for solution, and performs post-processing of the 2D FE simulation data to determine fracture loads. The fracture loads predicted using the manually generated and automatically generated 2D FE models are shown to be very close with a mean difference of around 8.8%. Repeated measures ANOVA showed no significant differences between the fracture loads calculated using FE models manually generated by three independent observers and those calculated using the automatically generated FE models (p > 0.05). (C) 2014 Elsevier Ltd. All rights reserved.

SUMMARY Purpose To evaluate the fracture load and survival rate of weakened and non-weakened roots restored with different intracanal posts. Methods Eighty teeth (16 mm) were prepared to a length of 10 mm with a custom drill. Fifty roots were weakened with a tapered diamond drill, and 30 roots were not. The specimens were embedded with acrylic resin up to 3 mm from the coronal aspect, and the periodontal ligament was simulated. The 50 weakened roots were restored with (n=10) CPC-gold (cast post and core made of gold alloy), CPC-Ni (cast post and core made of Ni-Cr alloy), FP (glass fiber posts), FP-W (glass fiber posts with a wider coronal diameter), and FP-CR (fiber posts relined with composite resin). The 30 nonweakened roots were restored with (n=10) CPC-gold, CPC-Ni, and FP. All of the posts were adhesively cemented. All of the specimens were mechanically cycled (37°C, 45°, 130 N, 2.2 Hz, and 1.5 million pulses) and evaluated after every 5 × 104 cycles to evaluate the presence of cracks as a primary outcome (event). The specimens that survived cycling were subjected to a fracture load test (load application on the palatal aspect at a 45° inclination). Failure mode was classified as favorable (above the simulated bone level) and catastrophic (below the simulated bone level). Survival rates were estimated using the Kaplan-Meier method. Fracture load data were analyzed using the Kruskal-Wallis test (α=0.05) for weakened roots, one-way analysis of variance, and Tukey test (p Results For the preliminary survival results, FP-W showed a higher survival rate when compared with CPC (gold/Ni). For the fracture load (N), the statistical analysis (p FP (282.2) = FP-W (274.1) = FP-RC (216.6). No differences were observed for the groups that were nonweakened (majority of favorable failures): CPC-gold (459.3) = CPC-Ni (422.0) = FP (347.9). Weakened roots restored with CPC-gold promoted high values of load fracture and unfavorable failure rates. Conclusion Cast post and cores or fiber posts can be used for restoring nonweakened roots. However, for weakened roots, a fiber post with a wider cervical emerging diameter appears to be a better alternative when compared with cast post and cores.

Aim The present in-vitro study aimed to compare the fracture resistance of mandibular premolars, obturated after instrumentation by Self-Adjusting File (SAF), ProTaper NEXT (PTN) and WaveOne (WO). Method Sixty extracted mandibular premolars were decoronated to obtain the root length of 15 mm. The samples were divided into 4 experimental groups: Group 1 without instrumentation (control), Group 2 instrumented with SAF, Group 3 with PTN (X1 and X2) and Group 4 with WO (primary). Following instrumentation, the samples were obturated by cold lateral compaction technique using gutta-percha and AH Plus sealer. A week later, after the sealer was completely set, a vertical load was applied to the specimen's canal until fracture. Statistical analysis was performed. Results The mean fracture load exhibited significant difference (p 0.05), but a significant difference with group 4 (p Conclusion Teeth instrumented by SAF exhibited a better fracture resistance.

The fracture of zirconia abutments has been reported relative to different amounts of reduction. Data are not available to demonstrate whether the apical vertical reduction of a zirconia abutment at different levels can be achieved while maintaining an acceptable load-to-fracture value.The purpose of this study was to evaluate in vitro the effect of different levels of preparation of zirconia implant abutments on the fracture load.Twenty-seven zirconia abutments (NobelProcera Abutment Zirconia) and 27 implant analogs (NobelReplace Implant Replicas) were divided into 3 groups of 9 abutments and 9 implant analogs. The Zu group (n=9) without any modification and with a chamfer margin width of 0.8 mm served as the control. The Zp1 group (n=9) was prepared with a chamfer margin width of 0.8 mm and with a 1-mm step in the labial margin. The Zp2 group (n=9) was prepared with a chamfer margin width of 0.8 mm and with a 1.5-mm step in the labial margin. The zirconia abutment was attached to the implant analog and fixed in a customized steel mounting table. The abutment-implant complex was immersed in saliva substitute to simulate the clinical oral environment. A 250 000 cycle sinusoidal fatigue load that ranged between 10 N and 210 N was applied to the specimens by using a universal testing machine. Subsequently, the specimens were loaded to fracture. One-way ANOVA and the Tukey post hoc test were used to compare the groups statistically (α=.05).The mean (standard deviation) values of the abutment load to fracture were as follows: Zu group = 567.3 ± 35.4 N; Zp1 group = 445.4 ± 41.0 N; Zp2 group = 430.5 ± 39.4 N. The lowest abutment load-to-fracture value was in the Zp2 group (408.6 N), whereas the highest abutment load-to-fracture value was in the Zu group (591.4 N). A significant (P.05) difference was found between the Zu group and the other groups, but no significant difference was found between the Zp1 group and the Zp2 group. The primary mode of fracture (67%) was at the abutment-analog interface.Preparation of prefabricated zirconia abutments had a statistically significant negative effect on the abutment load-to-fracture values.

Friction stir brazing (FSB) was developed for dissimilar joining to overcome the problems associated with friction stir lap welding (e.g. pin wear, narrow bonded area, hook defect) by metallurgical reaction instead of plastic flow. To enhance the thermomechanical effect of the rotating shoulder, a pin free tool with a large shoulder of 30 mm diameter was used in FSB of 5 mm thick Al/Cu plates in stepped lap configuration with Zn braze. Compared to the case using common tool of 20 mm diameter, it was found that although the intermetallic compound (IMC) layer grew thickly, it was disrupted into particles, and end crack within thick IMC layer was eliminated. As a result, the joint fractured not along interface and the fracture load increased by as much as 2271 N. This work proposed an approach to disrupting continuous IMC into particles by enhancing the mechanical effect of rotating shoulder.

The purpose of this paper is to develop clinching technology using AC servo direct-drive device. The control systems of AC servo direct-drive device are designed to control the clinching. It could accurately control the connection of aluminum alloy 6061 sheets with the round joint. The joint quality is evaluated by the tensile tests. The results of the tensile tests shown that fracture load satisfied the required joint strength. Meanwhile, AC servo direct-drive device also could ensure the efficiency and quality of clinching process.

Background Current clinical methods for fracture prediction rely on two-dimensional imaging methods such as dual-energy X-ray absorptiometry and have limited predictive value. Several researchers have tried to integrate three-dimensional imaging techniques with the finite element (FE) method to improve the accuracy of fracture predictions. Before FE models could be used in clinical settings, a thorough validation of their accuracy is required. In this paper, we try to evaluate the current state of accuracy of subject-specific FE models that are used for prediction of the fracture load of proximal femora. Methods All the studies that have used FE for prediction of fracture load and have compared the predicted fracture load with experimentally measured fracture loads in vitro are identified through a systematic search of the literature. A quantitative analysis of the results of those studies has been carried out to determine the absolute prediction error, percentage error, and linear correlations between predicted and measured fracture loads. Findings The reported coefficients of determination (R2) vary between 0.773 and 0.96 while the percentage error in prediction of fracture load varies between 5 and 46% with most studies reporting percentage errors between 10 and 20%. Interpretation We conclude that FE models, which are currently used only experimentally, are in general more accurate than clinically used fracture risk assessment techniques. However, the accuracy of FE models depends on the details of their modeling methodologies. Therefore, modeling procedures need to be optimized and standardized before FE could be used in clinical settings.

The aim of this study was to determine if biomechanical investigations of skull samples are reliable after skulls have been subjected to a freezing and thawing process. The skulls were obtained from 105 Japanese cadavers (66 males, 39 females) of known age that were autopsied in our department between October 2012 and June 2013. We obtained bone specimens from eight sites (four bilaterally symmetrical pairs) of each skull and measured the mass of each specimen. They were then classified into three groups (A, B, C) based on the duration of freezing of the experimental samples. The left-side samples were subjected to frozen storage (experimental group). The corresponding right-side samples were their controls. Bending tests were performed on the controls immediately after they were obtained. The experimental samples were preserved by refrigeration at -20 °C for 1 day (group A), 1 month (group B), or 3 months (group C). Following refrigeration, these samples were placed at 37 °C to thaw for 1 h and then were subjected to bending tests using a three-point-bending apparatus attached to a Handy force gauge. The device recorded the fracture load automatically when the specimen fractured. Statistical analyses revealed that there were no significant differences in sample fracture loads between the frozen preserved/thawed samples and the unfrozen controls for each of the cryopreservation intervals. We eliminated any possible sample mass bias by using controls from the same skull in each case. The results suggest that the freezing/thawing process has little effect on the mechanical properties of human skulls. Thus, frozen storage for up to 3 months is a good method for preserving human skulls.

Objectives: To test the fracture strength of weakened bovine incisors endodontically treated with mineral trioxide aggregate (MTA), cal- cium phosphate bone cement (CPBC) or fibre reinforced composite (FRC) posts, and to evaluate the fracture mode. Methods: Weakened bovine incisors (n = 75), standardized according to the dentinal wall thickness at the cervical area, were randomly assigned to one control group and three experimental groups. Unfilled teeth were assigned to group 1 (n = 20) and served as control group. Group 2 (n = 17) consisted of teeth filled with MTA. In group 3 (n = 18), the incisors were filled with CPBC and in group 4 (n = 20) with FRC posts. All specimens were subjected to load at a cross-head speed of 60 mm min 1 until fracture occurred. The initial (IL) and final fracture (FL) loads (N) were recorded, and the failure mode among the different groups was evaluated. Results: ANOVA showed a sta- tistically significant difference in fracture load among the groups. Tukey's test revealed a significant difference for the IL between the control group and the experimental groups with exception of the MTA group. The FL was not significantly different among the experimental groups. A high per- centage of favourable fractures was seen in the FRC and CPBC groups. Conclusion: FRC posts and CPBC could be promising materials to strengthen non-vital structurally compromised teeth.

Zur Untersuchung der Zusammenhange zwischen inneren Strukturen und mechanischen Eigenschaften wurden variierte Al2O3-Spruhgranulate hergestellt. Bei Modifikation der Additivart und -menge wurde der Einfluss der inneren Strukturen durch die Additiveigenschaften uberlagert. Bei Variation von z. B. Primarpartikelgrose oder Feststoffgehalt konnte der Einfluss der inneren Strukturen auf mechanische Eigenschaften deutlich abgebildet werden. Erhohte Schalendicken sowie reduzierte Mikroporositaten wirken festigkeitssteigernd, wobei die Mikrostruktur (Mikroporositat) offensichtlich einen dominierenden Einfluss hat. To investigate the correlations between internal granule structure and mechanical properties, different granules were spray-dried from varied Al2O3 suspensions. Variation of polymer type or amount overlays the effect of changed internal granule structure parameters. If suspension parameters like solid content or primary particle size are modified, a clear influence of internal structure can be measured. Increased shell thickness and reduced microporosity cause a fracture load increase. From the results a dominant influence of the microstructure on the resulting mechanical properties was shown.

The compression properties of three varieties of alfalfa seeds, such as Medicago sativa L. cv. Gannong No.3, Medicago sativa L. Longdong and Medicago sativa L. cv. Golden Empress, are studied by extrusion experiments using SANS universal material testing machine. The results of Longdong alfalfa seed show that the fracture load has relation with shape and size of the alfalfa seeds. For both of ellipsoidal seed and arched seed, the fracture load of single seed is about 19N to 30N. The fracture load increases linearly with the thickness of plump seed with the ratio of thickness to width greater than 0.75. These inclusions for other two varieties are the same with Longdong alfalfa seed. This research could offer a technical basis of designing and developing of the alfalfa seeder and seed harvesting machine.

Objectives: The objective of this study is to evaluate, in vitro, the thickness of immediate dentin sealing (IDS) materials on full crown preparations and its effect on the fracture load of a reinforced all-ceramic crown. Materials and Methods: Sixty premolars received full crown preparation and were divided into the following groups according to the IDS technique: G1-control; G2-Clearfil SE Bond; and G3-Clearfil SE Bond and Protect Liner F. After the impressions were taken, the preparations were temporized with acrylic resin crowns. IPS empress 2 restorations were fabricated and later cemented on the preparations with Panavia F. 10 specimens from each group were submitted to fracture load testing. The other 10 specimens were sectioned buccolingually before the thicknesses of Panavia F, Clearfil SE Bond and Protect Liner F were measured in 10 different positions using a microscope. Results: According to analysis of variance and Tukey′s test, the fracture load of Group 3 (1300 N) was significantly higher than that of Group 1 (1001 N) (P < 0.01). Group 2 (1189 N) was not significantly different from Groups 1 and 3. The higher thickness of Clearfil SE Bond was obtained in the concave part of the preparation. Protect Liner F presented a more uniform range of values at different positions. The thickness of Panavia F was higher in the occlusal portion of the preparation. Conclusions: The film thickness formed by the IDS materials is influenced by the position under the crown, suggesting its potential to increase the fracture load of the IPS empress 2 ceramic crowns.

Aim To determine whether the use of oval posts increases fracture resistance of root canal treated teeth with oval-shaped canals. Methods Extracted mandibular premolars with similar dimensions were decoronated. After root canal treatment, standardized post space preparations were performed to simulate the presence of oval-shaped root canal morphologies. Specimens were randomly assigned to 3 groups (n = 3 × 24). In group SFP (small fiber post), circular posts with a cervical diameter of 1.5 mm were used without additional form-congruent post space preparation. In group LFP (large fiber post), a circular post space preparation was performed to adapt posts with a cervical diameter of 1.9 mm. In group OFP (oval fiber post), oval posts with a long cervical diameter of 1.9 mm and short cervical diameter of 1.3 mm were utilized without additional post space preparation. Posts were cemented with dual-cure resin. All specimens were restored with standardized direct composite crowns. After thermo-mechanical loading in a computer-controlled masticator, all specimens underwent fracture resistance testing. Means and standard deviations were calculated. Data were analyzed using the Kruskal–Wallis test (α = 0.05). Results The highest mean fracture load was observed in group OFP (273N ± 51), the lowest in group LFP (258N ± 72). Kruskal–Wallis indicated no significant differences in fracture resistance among the three experimental groups. Conclusions Within the limitations of this laboratory study, oval posts did not reveal increased fracture resistance of root canal-treated premolars with oval-shaped root canals compared with circular posts.

A set of mixed-mode I/II fracture tests was carried out on a polyurethane material. Using a single edge notched bend (SENB) type specimen, containing straight and respectively inclined U notches, the full range from pure mode I to dominant mode II was achieved. Two different fracture criteria were employed for the prediction of the fracture conditions: the UMTS criterion and the averaged SED criterion. Using these two criteria a set of curves were derived in terms of the fracture load vs. notch radius. The agreement between the experimental results and those predicted based on these two criteria is discussed finally.

The objective of this in vitro study was to assess the effect of wall thickness on the fracture loads of monolithic lithium disilicate molar crowns. Forty-eight extracted molars were prepared by use of a standardized preparation design. Lithium disilicate crowns (e.max CAD, Ivoclar/Vivadent, Schaan, Liechtenstein) of different wall thicknesses (d = 0.5, 1.0, and 1.5 mm; n = 16 for each series) were then constructed and milled (Cerec MC-XL, Sirona, Bensheim, Germany). After placement of the teeth in acrylic blocks (Technovit, Heraeus Kulzer, Hanau, Germany), the crowns were adhesively luted (Multilink, Ivoclar Vivadent). In each series, eight crowns were loaded without artificial aging whereas another eight crowns underwent thermocycling (10,000 cycles, THE-1100, SD Mechatronik) and chewing simulation (1.2 million cycles, Willytec CS3, SD Mechatronik, F max = 108 N). All specimens were loaded until fracture on one cusp with a tilt of 30° to the tooth axis in a universal testing machine (Z005, Zwick/Roell). Statistical assessment was performed by use of SPSS 19.0. Crowns with d = 1.0 and 1.5 mm wall thickness did not crack during artificial aging whereas two of the crowns with d = 0.5 mm wall thickness did. The loads to failure (F u) of the crowns without aging (with aging) were 470.2 ± 80.3 N (369.2 ± 117.8 N) for d = 0.5 mm, 801.4 ± 123.1 N (889.1 ± 154.6 N) for d = 1.0 mm, and 1107.6 ± 131.3 N (980.8 ± 115.3 N) for d = 1.5 mm. For aged crowns with d = 0.5 mm wall thickness, load to failure was significantly lower than for the others. However, differences between crowns with d = 1.0 mm and d = 1.5 mm wall thickness were not significant. Fracture loads for posterior lithium disilicate crowns with 0.5 mm wall thickness were too low (F u 600 N. The wall thickness of posterior lithium disilicate crowns might be reduced to 1 mm, thus reducing the invasiveness of the preparation, which is essential for young patients.

Objectives This study evaluated and compared the impact of soldering on fracture resistance of veneered 4-unit fixed dental prostheses (FDPs). Materials and methods Forty-eight 4-unit zirconia frameworks were milled and randomly divided in four groups ( n =12). Untreated frameworks served as control, one group underwent thermal treatment, one group was sectioned and soldered in the connector between both pontics and one group was sectioned and soldered centrally in the mesial pontic. All frameworks were veneered with glass-ceramic material in powder build-up technique. The fracture load was determined on two different failure types, namely on chipping of the veneering ceramic and on total fracture of the FDP. Data were analysed using descriptive statistics, one-way ANOVA together with the Scheffe post-hoc test and Weibull statistics ( p Results The mean range of fracture load of chipped FDPs was determined between 655 N and 789 N; no differences between the tested groups were found ( p =0.587). The mean fracture load until total fracture ranged in all tested groups from 768 N to 1261 N. Sound FDPs and soldered FDPs in the connector area presented lower mean total fracture load compared to soldered FDPs in the pontic ( p Conclusions Soldered zirconia frameworks showed similar in-vitro performance compared to sound frameworks.