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Objective: The aim of this study was to evaluate fracture characteristics of rigid two-tooth segments splinted with fiber reinforced composite (FRC), with and without application of simulated masticatory forces. Material and Methods: In this experimental study, 80 extracted maxillary bicuspids were joined in pairs from the buccal aspect using FRC. The specimens were divided into two groups. In group A, the fracture load of FRC was measured. The 20 specimens of group B were initially loaded in a chewing simulator machine for 4×105 cycles to simulate a two-year chewing period. Samples that withstood these loads were assessed for fracture load. The results were compared using student t-test. Stereomicroscopic evaluation of fracture areas was performed to determine the fracture pattern. Results: None of the specimens in group B failed during application of simulated masticatory forces, meaning that the survival rate was 100%. Mean (standard deviation) of fracture loads in groups A and B were 195.80 (14.345) and 190.57 (24.027), respectively. No significant difference was found in mean fracture loads between the two groups. The overall fracture pattern was similar in both groups. Conclusions: FRC bars demonstrated sufficient durability to withstand chewing forces within the chewing simulation period. The fracture loads were higher than the mean mastication forces and remained almost unchanged after application of these forces.

Objectives To study the surface properties of polyetheretherketone (PEEK) and its bond strength with two veneering resins after different conditioning methods as well as fracture load of PEEK three-unit fixed dental prostheses (FDPs). Methods Two hundred and twenty five PEEK specimens were fabricated and divided into five groups: no treatment (A), etching with 98% sulfuric acid for 1 min (B), air-abrasion for 10 s with either 50 or 110 μm alumina (C and D, respectively), and silica coating using the Rocatec System (E). On 15 specimens of each conditioning method, contact angle and surface roughness were determined. The remaining 150 specimens of each conditioning method were divided into two groups for the veneering procedure with the composites Gradia (GC Europe) and Sinfony (3M ESPE). Shear bond strength (SBS) was measured and failure types were assessed. In addition, 15 FDPs were milled and the fracture load was tested. Data were analyzed using descriptive statistics, one-way ANOVA (Scheffé test), two sample Student's t-test, and Weibull statistics ( p < 0.05). Results Silica-coated PEEK surfaces showed the highest wettability. The highest roughness and lowest contact angles were observed for 110 μm air-abraded and silica-coated PEEK surfaces. The highest SBS values were, however, achieved in the acid-etched group. PEEK three-unit FDPs showed a mean fracture load of 1383 N with a plastic deformation starting approximately at 1200 N. Conclusions Acid etching should be applied when PEEK is used as substructure material and composite veneering material is applied. In this combination, PEEK might be a suitable material for FDPs, especially in load-bearing areas. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1209-1216, 2013. [ABSTRACT FROM AUTHOR]

Abstract: 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 Scheffé post-hoc test and Weibull statistics (p<0.05). Results: The mean range of fracture load of chipped FDPs was determined between 655N and 789N; no differences between the tested groups were found (p=0.587). The mean fracture load until total fracture ranged in all tested groups from 768N to 1261N. Sound FDPs and soldered FDPs in the connector area presented lower mean total fracture load compared to soldered FDPs in the pontic (p<0.001). Conclusions: Soldered zirconia frameworks showed similar in-vitro performance compared to sound frameworks. [Copyright &y& Elsevier]

Objectives: The authors analyzed the effect of fatigue on the survival rate and fracture load of monolithic and bi-layer CAD/CAM lithium-disilicate posterior three-unit fixed dental prostheses (FDPs) in comparison to the metal-ceramic gold standard. Materials and methods: The authors divided 96 human premolars and molars into three equal groups. Lithium-disilicate ceramic (IPS-e.max-CAD) was milled with the CEREC-3-system in full-anatomic FDP dimensions (monolithic: M-LiCAD) or as framework (Bi-layer: BL-LiCAD) with subsequent hand-layer veneering. Metal-ceramic FDPs (MC) served as control. Single-load-to-failure tests were performed before and after mouth-motion fatigue. Results: No fracture failures occurred during fatigue. Median fracture loads in [N], before and after fatigue were, respectively, as follows: M-LiCAD, 1,298/1,900; BL-LiCAD, 817/699; MC, 1,966/1,818. M-LiCAD and MC FPDs revealed comparable fracture loads and were both significantly higher than BL-LiCAD. M-LiCAD and BL-LiCAD both failed from core/veneer bulk fracture within the connector area. MC failures were limited to ceramic veneer fractures exposing the metal core. Fatigue had no significant effect on any group. Conclusions: Posterior monolithic CAD/CAM fabricated lithium-disilicate FPDs were shown to be fracture resistant with failure load results comparable to the metal-ceramic gold standard. Clinical investigations are needed to confirm these promising laboratory results. Clinical relevance: Monolithic CAD/CAM fabricated lithium-disilicate FDPs appeared to be a reliable treatment alternative for the posterior load-bearing area, whereas FDPs in bi-layer configuration were susceptible to low load fracture failure. [ABSTRACT FROM AUTHOR]

Introduction: Periprosthetic tibial plateau fractures (TPF) are rare but represent a serious complication in unicompartmental knee arthroplasty. The most common treatment for these fractures is osteosynthesis with cannulated screws or plates. The aim of this study was to evaluate two different treatment options for periprosthetic fractures. The hypothesis was that angle-stable plates show significantly higher fracture loads than fixation with cannulated screws. Materials and methods: Twelve matched, paired fresh-frozen tibiae with periprosthetic TPF were used for this study. In Group A, osteosyntheses with cannulated screws were performed, whereas in Group B plates fixated the periprosthetic fracture. DEXA bone density measurement and standard X-rays (AP and lateral) were performed before loading the tibiae under standardised conditions with a maximum load of up to 10.0 kN. After the specimens had been loaded, fracture patterns and fracture loads were analysed and correlated with BMD, BMI, bodyweight (BW), age and size of the tibial implant. Results: In the plate group all tibiae fracture occured with a median load of F = 2.64 (0.45-5.68) kN, whereas in the group with cannulated screws fractures occurred at a mean load of F = 1.50 (0.27-3.51) kN. The difference was statistically significant at p < 0.05. Discussion: Angle-stable plates showed significantly higher fracture loads than fixation with cannulated screws. Cannulated screws show a reduced stability of the tibial plateau. Therefore in periprosthetic TPF, osteosyntheses with angle-stable plates should be recommended instead of cannulated screws. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to evaluate the effect of AlO content on the fracture property of all-ceramics ZrO. To improve the all-ceramics ZrO restoration mechanics properity,96 samples containing 0,5,10 and 15 wt% of AlO particles were prepared by cold isostatic pressing (200 MPa) and 1 550 °C sintered. The phase was analyzed by X-ray diffraction analysis and the bulk densities of the samples were made using Archimedes principle. Samples were randomly divided into four groups. In each group, 24 specimens were prepared so that the angle between notch and specimen's long axis is 90° and 60°. Notch depths were 1 mm for all samples. Samples were loaded with three-point bending method. 90° cut samples were used to measure fracture toughness while 60°cut samples were used to observe fracture curve by taking points on the fracture extension path under microscope, plotting points on coordinates, generating fitting curve by software 'Origin', and analyzing the microstructure of the specimen fracture surfaces by scanning electron microscopy (SEM).The results show that the increment of AlO has insignificant effect on the densification of all-ceramic ZrO.XRD analysis shows that the specimen is comprised of t-ZrO and α-AlO before fracture while fracture surface is m-ZrO, t-ZrO and α-AlO. ZrO containing 10% AlO has the optimum mechanical properties and unconspicuous crack propagation and distribution. The observations may provide a reference for the materials selection, shape design, and production process of all-ceramic crown and bridge. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the fracture load and fracture mode of th:n Ceria-stabilized tetragonal zirconia poly cry stals/Al2O3 nanocomposites (Ce-TZP/A) and Yttria-stabilized tetragonal zirconia po.ycrystals (Y-TZP) crown frameworks. Artificial maxillary second premolars were prepared for metal-ceramic crown and all-ceramic crown restorations and Co-Cr tooth analogs were duplicated. 10 standard (0.5 mm overall thickness) zirconia-ceramic crown frameworks (Y-TZPs) for all-ceramic crown preparation and 10 modified (a 0.3-mm-thick framework increased in thickness by adding a 1.0-mm-thick palatal margin with a height of 2.0 mm) zirconia-ceramie crown frameworks (Y-TZPm, Ce-TZP/Am) for metal-ceramic crown preparation were fabricated. The frameworks were cemented to the Co-Cr tooth analog and loaded vertically until fracture. The fracture load of Y-TZPs (180.0 N) and Ce-TZP/Am (183.7 N) were significantly higher than that of Y-TZPm (133.7 N). There was a significant difference in fracture mode between Y-TZPm and Ce-TZP/Am. Within the limitation of this study, Ce-TZP/Am provide sufficient strength for clinical application. [ABSTRACT FROM AUTHOR]

To evaluate the fracture resistance of computer-aided design and computer-assisted manufacturing restorations as the abutment of removable partial dentures, experimental blocks, with the rest seat made of feldspar, hybrid resin composite, lithium disilicate glass ceramic, or zirconia, were subjected to loading by a metallic occlusal rest. The rest contacted the rest seat with an accurate fit and two mismatch contact conditions: bottom and sidewall contact. Zirconia exhibited the highest fracture load, and the fracture load of the accurate fit was significantly higher than that of the sidewall contact (p<0.05) and insignificantly higher than that of the bottom contact (p>0.05). A finite element analysis of the sidewall contact revealed a higher tensile stress concentration at the bottom of the rest seat than the other contact conditions. The mismatch between the rest and the restoration reduced fracture resistance, while zirconia as the abutment withstood the average occlusal force of the posterior region.

Aims: Periprosthetic hip fractures (PPFs) after total hip arthroplasty are difficult to treat. Therefore, it is important to identify modifiable risk factors such as stem selection to reduce the occurrence of PPFs. This study aimed to clarify differences in fracture torque, surface strain, and fracture type analysis between three different types of cemented stems., Methods: We conducted biomechanical testing of bone analogues using six cemented stems of three different types: collarless polished tapered (CPT) stem, Versys Advocate (Versys) stem, and Charnley-Marcel-Kerboull (CMK) stem. Experienced surgeons implanted each of these types of stems into six bone analogues, and the analogues were compressed and internally rotated until failure. Torque to fracture and fracture type were recorded. We also measured surface strain distribution using triaxial rosettes., Results: There was a significant difference in fracture torque between the three stem types (p = 0.036). Particularly, the median fracture torque for the CPT stem was significantly lower than that for the CMK stem (CPT vs CMK: 164.5 Nm vs 200.5 Nm; p = 0.046). The strain values for the CPT stem were higher than those for the other two stems at the most proximal site. The fracture pattern of the CPT and Versys stems was Vancouver type B, whereas that of the CMK stem was type C., Conclusion: Our study suggested that the cobalt-chromium alloy material, polished surface finish, acute-square proximal form, and the absence of a collar may be associated with lower fracture torque, which may be related to PPF. Cite this article: Bone Joint Res  2022;11(5):270-277.

Objective: This study tested the fracture load of milled and conventionally fabricated polymeric and glass-ceramic three-unit fixed dental prostheses (FDPs) after aging. Materials and methods: FDPs were fabricated ( N = 1,050) from four computer-aided design and computer-aided manufacturing (CAD/CAM) resins: (1) AT (artBlock Temp); (2) TC (Telio CAD); (3) ZP (ZENO PMMA); (4) CT (CAD-Temp); two conventionally fabricated resins, (5) IES (integral esthetic press), (6) CMK (CronMix K), and a glass-ceramic (control) (7) PG (IMAGINE PressX). Specimens of each group were tested immediately after fabrication ( n = 15 per material). Seventy-five FDPs per material type were stored in artificial saliva (37°C) and 15 of them were randomly selected after aging (1, 7, 28, 90, and 180 days) for fracture load measurement. The remaining specimens ( n = 60 per material) were subjected to chewing simulation (×120.000-1.200.000, 49 N, 5°C/50°C). The data were analyzed using two-way and one-way ANOVA followed by Scheffé test. Results: The interactions between FDP materials and aging time in both storage media showed a significant impact on the results ( p < 0.001). Among saliva storage groups, TC and ZP showed the highest, and PG the lowest fracture load ( p < 0.05). AT and CT were not affected from chewing simulation. TC, ZP, and AT presented the highest in ascending order ( p < 0.05), PG and CMK showed the lowest fracture load after chewing simulation ( p < 0.001). Conclusions: Aging did not influence the fracture load of FDPs made of CAD/CAM resins. FDPs made of glass-ceramic showed significantly lower fracture load than those of all resin FDPs. Clinical relevance: Considering fracture load measurements, CAD/CAM resins tested could be alternative materials to glass-ceramic for FDP construction. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the fracture load and failure types of veneered zirconia crowns that were air-abraded on either the veneering or cementation surface. Fracture loads were determined before and after chewing simulation. Standardized Y-TZP frameworks ( n = 360) for canines were fabricated and divided into one control group ( n = 72) and 12 test groups ( n = 24). The test groups were air-abraded using alumina powder (10 s, 2 bar, distance: 10 mm) with particle size of 50 μm resp. 110 μm and veneered with one of the veneering ceramics: Triceram, Zirox, or VITA VM9. The crowns were cemented on their corresponding CoCr abutment. The initial fracture load was measured in one half of each group ( n = 12), and the other half ( n = 12) was subjected to chewing cycling. The data were analyzed using three-way and one-way ANOVA, a post-hoc Scheffé test, two sample Student's t-test, and Weibull statistics ( p < 0.05). Thus, nonaged, air-abraded groups of two veneering ceramics (Triceram, VITA VM9) showed higher mean fracture load compared to control groups. After chewing simulation, air-abraded groups showed lower mean fracture load compared to control groups. Aging decreased the Weibull modulus of all tested groups, and air-abraded groups showed lower Weibull moduli compared to control groups. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 1683-1690, 2012. [ABSTRACT FROM AUTHOR]

Wire rope in elevators can become disconnected by tensile stress from friction between the rope and sheave, and by repeated stress including bending stress from various effects formed during contact between the rope and sheave. It is known that in designing wire rope, its strength is affected when wire disconnection occurs. However, insufficient related data is available. Therefore, fracture strength reduction and the effect of bending fatigue on wire rope life is difficult to evaluate. We considered the effects of wire rope diameter and tensile stress on fracture strength and wire rope life. We observed that fracture strength rapidly decreased when bending fatigue accumulated at the same time that the wire became disconnected. Moreover, bending fatigue was shown to be a crucial factor in decreased wire rope life. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to evaluate the effect of different types and design of zirconia frameworks as well as the effect of different veneering ceramics on the fracture strength of crowns. The importance of different abutment materials was also evaluated. Materials and methods: Eighty cores, 40 in a fully-sintered zirconia material and 40 in a pre-sintered zirconia material were made. Twenty cores of each material were made with a core of even thickness shape (ES) and 20 were made with a core with anatomical shape (AS). The cores were divided into subgroups and veneered with one of two different veneering ceramics: a porcelain and a glass-ceramic material. In total eight groups of 10 crowns were made. They were all cemented onto abutments made of resin. One extra group of 10 AS, pre-sintered zirconia cores veneered with glass-ceramic were made and cemented onto titanium abutments. All crowns underwent thermocycling and mechanical pre-load and were finally loaded until fracture. Results: AS crowns withstood significantly higher loads than ES crowns ( P-value <0.001), and crowns with titanium abutments withstood significantly higher loads than crowns supported by abutments made of inlay pattern resin ( P-value <0.001). Three types of fracture were noted: minor and major fracture of the veneering ceramic, and complete fracture through core and veneer. ES crowns showed significantly more major fractures of the veneering ceramic than AS crowns. Conclusions: This in vitro study indicates that the design of the core, as well as the abutment support, significantly influences fracture load and fracture mode of yttria-stabilized tetragonal zirconia polycrystals crowns. To cite this article: Larsson C, El Madhoun S, Wennerberg A, Vult von Steyern P. Fracture strength of yttria-stabilized tetragonal zirconia polycrystals crowns with different design: an in vitro study. Clin. Oral Impl. Res. 23, 2012; 820-826. doi: 10.1111/j.1600-0501.2011.02224.x [ABSTRACT FROM AUTHOR]

ABSTRACT One of the most powerful criteria to predict the critical fracture load in plates with notches is the strain-energy density averaged over a well-defined control volume ahead of the notch tip. Although the averaged strain-energy density (ASED) criterion has been proposed for homogeneous materials, it has been shown in this paper that this criterion can also be applied for non-homogeneous materials, especially for functionally graded materials (FGMs). A numerical method has been used to evaluate the control volume boundary, the averaged strain-energy density over the control volume, and also the critical fracture load in FGMs under mode I loading. A new set of experimental results on fracture of blunt V-notched samples made of austenitic-martensitic functionally graded steel under mode I loading have been provided. [ABSTRACT FROM AUTHOR]

Abstract: The averaged value of the strain-energy density over a well-defined volume is used to assess the static strength of U-notched specimens under mixed mode loading (I+II). The volume is centered in relation to the maximum principal stress present on the notch edge, by rigidly rotating the crescent-shaped volume already used in the literature to analyze U- and V-shaped notches under mode I loading. In total 96 new tests have been carried out on specimens made of structural steel with a martensite phase weakened by U-notches. The notch root radius varies from 0.2 to 2.0mm while the notch depth is equal to 5, 7.5, 10 and 15mm, respectively. In addition, for the lowest value of the notch depth (5mm), some data from cracked specimens are summarized in the paper. Good agreement was found between experimental results and theoretical assessment based on the averaged strain energy density criterion under mixed mode loading. [Copyright &y& Elsevier]

Purpose: Periprosthetic tibial plateau fractures represent a rare but serious complication in unicompartmental knee arthroplasty and are associated with extended sagittal tibial bone cuts. These can occur during the surgery, weaken the posterior cortex of the tibia and are associated with periprosthetic tibial plateau fractures. Although excellent long-term results have been reported with cemented unicompartmental knee arthroplasty, there is high interest in cementless fixation. The aim of the study was to compare fracture loads of cementless and cemented unicompartmental knee arthroplasty. Methods: Tibial components of the Oxford Uni were implanted in six paired fresh-frozen tibiae with a defined extended saw cut (10°) at the dorsal cortex of each specimen. In one set, surgery was performed with cement fixation, and in the other, cementless components were implanted. Vertical loads were then applied under standardised conditions to fracture the specimens. Results: Median loads of 3.7 (0.7-6.9) kN led to fractures in the cemented group, whereas cementless fixated tibiae fractured with a median load of 1.6 (0.2-4.3) kN ( P = 0.02). Conclusion: The loading capacity in tibiae with cementless components is significantly less compared to cemented fixation. The results show that in case of an extended sagittal bone cut patients especially those with poor bone quality who are treated with a cementless unicompartmental knee arthroplasty are at higher risk for periprosthetic tibial fractures. [ABSTRACT FROM AUTHOR]

The paper deals with the minimum value of a fracture load, with respect to the notch root radius, in plates weakened by U-notches under Mode I loading. It has been found that the fracture load has a minimum value at a critical value of the notch root radius ( ρ ), using four criteria, namely, Mean Stress (MS), maximum tangent stress or Point Stress (PS), Critical Strain-Energy (CSE) and Averaged Strain-Energy Density (ASED). Using a characteristic length ( l c h ), which is a function of material properties, the results showed that the dimensionless critical notch root radius ( ρ / l c h ) c r depended on w / a ratio (the specimen width to the notch depth), Poisson ratio, and loading condition (tensile or bending loading) under Mode I loading. In other words, according to these criteria, a notch root radius different from zero exists, providing a minimum fracture load. Therefore, a crack is not more dangerous rather than a U-notch under Mode I loading. This critical notch root radius is important for a quasi-brittle material, but may not be significant for brittle ones in practical engineering situations. Good agreement was found between theoretical predictions and experimental results on Al356-T6. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The aim of this study was to compare the fracture load of veneered anterior zirconia crowns using normal and Weibull distribution of complete and censored data. Methods: Standardized zirconia frameworks for maxillary canines were milled using a CAD/CAM system and randomly divided into 3 groups (N =90, n =30 per group). They were veneered with three veneering ceramics, namely GC Initial ZR, Vita VM9, IPS e.max Ceram using layering technique. The crowns were cemented with glass ionomer cement on metal abutments. The specimens were then loaded to fracture (1mm/min) in a Universal Testing Machine. The data were analyzed using classical method (normal data distribution (μ, σ); Levene test and one-way ANOVA) and according to the Weibull statistics (s, m). In addition, fracture load results were analyzed depending on complete and censored failure types (only chipping vs. total fracture together with chipping). Results: When computed with complete data, significantly higher mean fracture loads (N) were observed for GC Initial ZR (μ =978, σ =157; s =1043, m =7.2) and VITA VM9 (μ =1074, σ =179; s =1139; m =7.8) than that of IPS e.max Ceram (μ =798, σ =174; s =859, m =5.8) (p <0.05) by classical and Weibull statistics, respectively. When the data were censored for only total fracture, IPS e.max Ceram presented the lowest fracture load for chipping with both classical distribution (μ =790, σ =160) and Weibull statistics (s =836, m =6.5). When total fracture with chipping (classical distribution) was considered as failure, IPS e.max Ceram did not show significant fracture load for total fracture (μ =1054, σ =110) compared to other groups (GC Initial ZR: μ =1039, σ =152, VITA VM9: μ =1170, σ =166). According to Weibull distributed data, VITA VM9 showed significantly higher fracture load (s =1228, m =9.4) than those of other groups. Significance: Both classical distribution and Weibull statistics for complete data yielded similar outcomes. Censored data analysis of all ceramic systems based on failure types is essential and brings additional information regarding the susceptibility to chipping or total fracture. [Copyright &y& Elsevier]

Abstract: Fracture of a cracked elastic medium in compression is investigated. For fracture of an angled straight crack in compression, two crack surfaces are in contact under the action of far-field compressive loading. The classical singular terms related to mode-I stress intensity factors (SIFs) at the near-tip field are no longer present. Instead, another nonsingular stress perpendicular to the flaw plane is added. The singular field related to the mode-II SIFs and two nonsingular T-stresses, parallel to and perpendicular to the crack direction, form leading and secondary parts of the asymptotic stress field near the crack tip. The crack-tip stress field is dominated by the mode-I, II SIFs and one T-stress term with positive mode-I SIFs for an opening crack, or by the mode-II SIFs and two T-stress terms with mode-I SIFs less than or equal to zero for a closed crack in compression, respectively. For the case of an inclined crack, the effects of two T-stresses, confinement ratio and Coulomb friction on kink angle and fracture load are discussed for smooth and rough crack surfaces. Our theoretical predictions on fracture initiation direction and critical fracture stress are satisfactory as compared with experimental measurements and field observations for simple compression. The obtained results show that for negative mode-I SIFs, our model containing three parameters (mode-II SIF, and two T-stresses) is superior to the classical model containing the mode-II SIF alone or containing the mode-II SIF and one T-stress term simultaneously. Two T-stresses or two biaxiality ratios play a crucial role in determining the direction of fracture onset for a wing crack being created from a closed crack in uniaxial and biaxial compression. [Copyright &y& Elsevier]

Summary The aim of this study was to analyse the strength and failure mode of teeth restored with fibre posts under retention and flexural-compressive loads at different stages of the restoration and to analyse whether including a simulated ligament in the experimental setup has any effect on the strength or the failure mode. Thirty human maxillary central incisors were distributed in three different groups to be restored with simulation of different restoration stages (1: only post, 2: post and core, 3: post-core and crown), using Rebilda fibre posts. The specimens were inserted in resin blocks and loaded by means of a universal testing machine until failure under tension (stage 1) and 50º flexion (stages 2-3). Half the specimens in each group were restored using a simulated ligament between root dentine and resin block and the other half did not use this element. Failure in stage 1 always occurred at the post-dentine interface, with a mean failure load of 191·2 N. Failure in stage 2 was located mainly in the core or coronal dentine (mean failure load of 505·9 N). Failure in stage 3 was observed in the coronal dentine (mean failure load 397·4 N). Failure loads registered were greater than expected masticatory loads. Fracture modes were mostly reparable, thus indicating that this post is clinically valid at the different stages of restoration studied. The inclusion of the simulated ligament in the experimental system did not show a statistically significant effect on the failure load or the failure mode. [ABSTRACT FROM AUTHOR]

The present study was conducted to compare and evaluate the tensile strength of silver soldered joints of stainless steel and cobalt-chromium orthodontic wires with band material . An attempt was made to observe the effect of joint site preparation on various orthodontic joining configuration . A total of sixty wires specimens were selected out of them, thirty in stainless steel group and thirty in cobalt - chromium group Again in each group sample were equally divided into three-sub groups i.e., End - End ,Round and to Orthodontic band material. The findings of the study were suggestive that all three configuration may be used for preparing silver soldered joints irrespective of the quality of the wire. However when subjecting the wire to joint site preparation, S.S wire should be used keeping its limitations in view. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The aim of this study was to test whether the load bearing capacity of anterior zirconia crowns veneered with overpressed or layered, is similar and to evaluate the failure types. Methods: Standardized zirconia frameworks were fabricated and randomly divided into 8 groups (N =120, n =15 per test group). Four groups were veneered with one of the layered veneering porcelains: Zirox, GC Initial ZR, VITA VM9 or IPS e.max Ceram and the other four groups were veneered with overpressed veneering porcelains: PressX Zr, GC Initial LF, VITA PM9 or IPS e.max ZirPress. The crowns were cemented on their corresponding CoCr abutment and the specimens were loaded at an angle of 45° in a Universal Testing Machine to determine the fracture load. Data were analyzed using one-way and two-way ANOVA, followed by a post hoc Scheffé test, t-test and Weibull analysis (alpha=0.05). Results: Within three manufacturers of veneering porcelain, fracture load values were not statistically significant between overpressed and layered porcelain systems. Within one manufacturer of veneering porcelain, the overpressed crowns (IPS e.max ZirPress: 1519±334N) demonstrated significantly higher (p <0.05) fracture load than that of the layered one (IPS e.max Ceram: 894±160N). Except with IPS e.max ZirPress, where exclusively only chipping of the veneering porcelain was observed, all other porcelain systems showed predominantly framework fractures together with fracture of the veneering porcelain. Conclusion: Overpressed veneering porcelains for zirconia frameworks exhibited similar or better fracture load compared with layered ones. [Copyright &y& Elsevier]

Introduction: In spite of ceramics' desirable esthetics and compressive strength, they are inherently prone to fracture and are weak against tensile and torsional loads. In-Ceram Alumina is a type of reinforced alumina which has been used as a core material for crowns and three units anterior bidges since 90s. Turkom-Cera is presented in the market recently which uses a simple method to produce single and multiple unit anterior and posterior restorations. The purpose of this study is to evaluate the fracture resistance of copings made by these systems. Materials & Methods: 40 brass dyes were prepared and divided into two groups. To make the copings, impression was taken and model dyes were made. 20 ceramic coping were prepared according to manufacturers instructions for each group, cemented to brass dyes and kept in 100% moisture for one week. Load to fracture test was performed by Universal testing machine and load was applied by a speed of 0.5 mm/min. Fracture load was recorded for each specimen. Data were collected and entered to the SPSS software and t-test was done. Results: The average fracture load for Turkom-Cera was 1273 N and was 1079 N for In-Ceram Alumina. The maximum and minimum values for the first group was 2490, 530 N and for the second group was 1490, 714 N respectively. According to t-test results with P-value<0.05 there was no significant difference between the two groups. Conclusion: According to the close results for both groups, clinical performance of the Turkom-Cera ceramic copings would be similar to In-Ceram Alumina and a wide range of clinical use could be anticioated for this system. [ABSTRACT FROM AUTHOR]

This study investigated the influence of zirconia coping designs on the fracture load of all-ceramic crown. Four kinds of zirconia copings were designed (a: Conventional zirconia coping with flat occlusal surface: thickness of the each coping is 0.6 mm evenly, and at the cervical margin area, the coping is adjusted sharply so as to fit preparation margin, b: Conventional zirconia coping with shoulder collar of 1 mm: thickness of the each coping is 0.6 mm evenly, and there is a collar of 0.6 mm from the margin, c: Zirconia coping with following original cuspal configuration (concave): two inclined cusp planes, and at the cervical margin area, the coping is adjusted sharply so as to fit preparation margin, and d: Zirconia coping with supporting configuration on the occlusal area: supporting configuration against the occlusal force, and at the cervical margin area, the coping is adjusted sharply so as to fit preparation margin) and porcelain was fired. Vertical and lateral load were conducted until fracture. Coping design affected the fracture load; conventional uniform thickness coping design showed the lowest load (a), whereas cuspal configuration to perform even thickness of porcelain showed the highest fracture load both load directions (c). [ABSTRACT FROM AUTHOR]

Abstract: Eight pairs of fresh frozen human femora were prepared for hip resurfacing. One side of each pair was impacted gently, the other side vigorously. After implantation procedure, specimens were loaded in a material testing machine to the ultimate fracture load. Median impaction loads on the vigorously implanted side were 11 298N compared to 1374N on the gently implanted side. Failure loads in the high-impact group (median, 8873N) were significantly (P = .0078) reduced when compared with the low-impact group (median, 9237N). The study stresses that meticulous reaming of the femoral head and the pinhole is of tremendous importance. Remaining obstacles can lead to excessive loads, while attempting to enforce the correct seating of the implant. Only careful, slight tapping should be applied to ensure final seating. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The purpose of this study was to evaluate the fracture loads of post-and-core systems with two different individually formed fibre post designs and polymerization conditions. Methods: Totally seventy-two (n =8/group) bovine teeth were cut and made up the root length of 15.0mm. They were divided into 3 main groups (Group A, B, C). A: one glass fibre post was light-cured before cementation, B: fibres were bundled to fill the entire root canal opening and light-cured before cementation, C: one unpolymerized glass fibre post was inserted into cement-filled root canal and light-cured with luting cement (ParaCem). Moreover specimens of each group were divided into 3 subgroups according to the post length: subgroup 1: 10mm; subgroup 2: 7.5mm; subgroup 3: 5.0mm. After cementation, the core was built up, and then made the composite resin crown (Filtek Z250). Fabricated specimen was loaded from 45° of palatal side at a crosshead speed of 1.0mm/min. The first load drop and maximum fracture loads were statistically analyzed by ANOVA and Tukey''s test. Results: Maximum fracture load of Group B (433N) and C (418N) are significantly higher than Group A (284N) (p <0.01). Short post (5mm) provided higher fracture loads in all main groups, especially in Group C. Conclusions: Using short and thick fibre post system (the same diameter as the root canal) showed higher strength than one fibre post only. In addition, by curing the cement and the fibre material simultaneously, the strength of the restored tooth was increased. [Copyright &y& Elsevier]

Abstract: Periprosthetic tibial plateau fractures (TPF) are rare but represent a serious complication of unicompartmental knee arthroplasty (UKA). As TPFs usually occur perioperatively, these can be associated with extended sagittal saw cuts during surgery. The aim of the study was to evaluate TPF as a function of extended sagittal saw cuts. The hypothesis was that extended sagittal saw cuts reduce the loading capacity of the tibial plateau and increase the risk of periprosthetic TPF. In a randomised study, standardised cemented Oxford UKA tibial component implantation was performed in six matched, paired fresh-frozen tibiae. In group A, a regular preparation of the tibial plateau was performed, whereas in group B a standardised extended sagittal saw cut was made at the dorsal cortex of the tibia. All tibiae were fractured under standardised conditions and fracture patterns and fracture loads were analysed. In group A, tibiae fractured with a mean load of F max =3.9 (2.3–8.5) kN, whereas in group B fractures occurred at a mean load of F max =2.6 (1.1–5.0) kN. The difference was statistically significant (p <0.05). Extended sagittal saw cuts in UKA weaken the tibial bone structure. Our results show that descendent extended sagittal saw cuts of 10° reduce fracture loads by about 30%. Surgeons should be aware of the potential pitfalls of an extended sagittal saw cut, as this can lead to reduced loading capacity of the tibial plateau and increase the risk of periprosthetic TPF. [Copyright &y& Elsevier]

Abstract: Objectives: The purpose of this in vitro study was to compare the centric and eccentric quasi-static and fatigue fracture strength of industrially prefabricated resin-bonded three-unit inlay-retained fixed dental prostheses (IPIRFDPs). The IPIRFDPs consisted of industrial manufactured yttria-stabilized tetragonal zirconia (Y-TZP) frameworks with an industrially added microhybrid composite veneering. Methods: Identical IPIRFDP-models consisted of a second premolar, a missing first molar and a second molar (CoCrMo alloy) integrated in a low melting alloy base. Roots were covered with a soft silicone layer to simulate an artificial parodontium. Premolars had an occlusal–distal inlay-preparation and molars a mesial–occlusal inlay-preparation. Forty-two IPIRFDPs with a connector size of 9mm2 and a framework connector size of 4.7mm2 were cemented adhesively to the IPIRFDP-models. Quasi-static fracture strength was tested with centric (n =12) and eccentric (n =6) loading in a universal testing machine at a cross-head speed of 1mm/min. Fatigue fracture strength was tested at 1200N with centric loading (n =12) and at 600/500N with eccentric loading (n =6) at a frequency of 0.5Hz. Statistical comparison of groups was performed with the Mann–Whitney U test. Results: Quasi-static fracture strength differed significantly between centric (1749N) and eccentric loading (880N, p <0.001). Mean loading cycles until fracture were 4432 for centric loading at 1200N compared to only 3 and 410 loading cycles for eccentric loading at 600 and 500N, respectively. Significance: Considering the maximum chewing forces in the molar region, it seems clinically possible to use prefabricated IPIRFDPs with Y-TZP as a core material with a framework connector size of 4.7mm2. [Copyright &y& Elsevier]

All-ceramic dental restorations are popular because they provide superior esthetics and better biocompatibility than traditional porcelain-fused-to-metal restorations. Several factors influence the strength of a ceramic crown, including the shape of the prepared tooth, the all-ceramic crown system used, thickness of the porcelain crown, defects within the porcelain, and luting cement systems. The purpose of this study was to investigate the effect of different resin cements on the fracture loads of aluminium oxide and lithium disilicate all-ceramic crown systems. [ABSTRACT FROM AUTHOR]

Objective: In in vitro tests, metals and resins are frequently used as substitutes for human teeth. This study aims at determining the suitability of various materials for substituting human incisors in load capability tests. Method: Veneering composite (Adoro; n = 16) and non‐precious CoCr‐alloy (NPA; n = 16) were used for manufacturing 32 identical specimens based on the model of a maxillary central incisor resin tooth (Morita). Sixteen human incisors served as a control group. After root canal treatment, all specimens were restored with fiber‐reinforced composite posts and core build‐ups. For each group, eight specimens were chosen randomly and restored either with identical NPA crowns or with all‐ceramic crowns. Specimens were exposed to thermal cycling and mechanical loading (TCML) until failure. Statistical analysis was conducted using the Kruskal–Wallis test and the Bonferroni‐adjusted Mann Whitney U‐test. Results: In ceramic crowns, the highest median fracture resistance was found in alloy tooth substitutes (430 N) and natural incisors (426 N), which both showed a significantly higher fracture resistance than composite tooth substitutes (162 N). In alloy crowns, alloy tooth substitutes exhibited the highest fracture resistance (348 N), but no statistically significant difference could be detected between natural incisors (158 N) and composite tooth substitutes (117 N). No artificial tooth substitute showed fracture patterns similar to those of natural incisors. Significance: Mechanical parameters are significantly influenced by the type of restoration and the restorative material used. In in vitro tests, the range of artificial tooth substitutes suitable for the replacement of human incisors is limited by load capability. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2009 [ABSTRACT FROM AUTHOR]

Abstract: Ceramics are more and more used for hip joint implants due to their excellent biocompatibility, longevity, corrosion and wear resistance. Despite these excellent material properties, their fracture toughness is low compared to metals. Various studies reported the probability of in vivo fracture occurring on an implanted ceramic femoral head is in the range of 0.004–0.05%. Besides material flaws and overloading, improper handling during implantation may induce fractures of the ceramic ball head on the long term. Even though the exact cause of failure could not be clarified in most of the cases, there is strong suspicion that the presence of biological contaminants may constitute the primary cause of failure. Asymmetric wear traces observed on fragments of in vivo fractured alumina femoral head endorse the assumption that a non-uniform load was introduced in the ball head. This study focuses on the influence of blood and bone chips located in the stem–ball interface and of scratches on the metal tapers on the strength of alumina ball heads. Mechanical tests on 26 samples according to ISO 7206-10 were performed to identify the effect of contaminants and altered taper on the static fracture load. The experimental study showed that relatively small contaminants induce considerable decreases of the static fracture load. A blood drop of 30mg reduced the fracture load by more than 60% while a bone chip as small as 4mg reduced it to less than half the reference fracture load. In a third experimental series, the change of fracture load with a 5–10mm scratch on the stem was found to be in the range of the standard deviation and thus no clear influence could be observed. Since any alteration of the interface between metal taper and ceramic ball head through contaminants yields a non-uniform load introduction leading to a reduction of the static fracture load, an absolute clean interface is of primary importance. [Copyright &y& Elsevier]

Purpose: The aim of this study was to compare the fracture load of different joints made by conventional brazing, tungston inert gas (TIG) and laser welding. Materials and methods: Six standardized joining configurations of spring hard quality orthodontic wire were investigated: end- to-end, round, cross, 3 mm length, 9 mm length and 6.5 mm to orthodontic band. The joints were made by five different methods: brazing with universal silver solder, two TIG and two laser welding devices. The fracture loads were measured with a universal testing machine (Zwick 005). Data were analysed with the Mann-Whitney-Wilcoxon and Kruskal-Wallis tests. The significance level was set at P<0.05). Results: In all cases brazed joints were ruptured at a low level of fracture load (186-407 N). Significant differences between brazing and TIG or laser welding (P<0.05) were found. The highest mean fracture loads were observed for laser welding (826 N). No differences between the various TIG or laser welding devices were demonstrated, although it was not possible to join an orthodontic wire to an orthodontic band using TIG welding. Conclusion: For orthodontic purposes laser and TIG welding are solder free alternatives. TIG welding and laser welding showed similar results. The laser technique is an expensive, but sophisticated and simple method. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The aim of this in vitro study was to assess the influence of thermal properties of veneering ceramics on the fracture load of layered ceria stabilized zirconia/alumina nanocomposite (Ce-TZP/A) single crowns. Methods: Ce-TZP/A single crown frameworks (nanoZr) were veneered with 5 different veneering ceramics for zirconia (Cerabien ZR, IPS e.max, Triceram, Vintage ZR, VM9). In addition, veneering ceramics for alumina (Allux) and for the metal–ceramic technique (Reflex) were included in order to cover a wide range of coefficients of thermal expansion. Fracture load of the crowns was assessed in a shear test (n =10). Glass transition temperatures (T g) of the ceramics as well as the coefficients of thermal expansion of the ceramics (α veneer) and Ce-TZP/A (α core) between 25 and 500°C were determined (n =6). Results: Fracture load ranged from 574.0±97.1N (IPS e.max) to 1009.6±150.0N (VM9). Δα = α core − α veneer and ΔT = T g −25°C (ΔT in K) were calculated. The fracture load was strongly correlated to Δα ΔT with a maximum at Δα ΔT ≈580×10−6. Significance: The overall fracture load of veneered Ce-TZP/A crowns is correlated to the thermal properties of the respective veneering ceramic. [Copyright &y& Elsevier]

The periprosthetic femoral fracture is one of the most severe complications after total hip arthroplasty and is associated with an increased mortality. The underlying causes and the patient- and implant-specific risk factors of periprosthetic femoral fractures remain insufficiently understood. The aim of this study was to gain a more profound understanding of the underlying fracture mechanisms and to provide experimental datasets for validation of computational models. Six cadaveric femurs were implanted with straight hip stems (Zweymueller design) and loaded until fracture reproducing the clinically relevant load cases stumbling and sideways fall. Displacements and the strain distribution on the surface of the femurs and implants, as well as the fracture load and implant subsidence were measured. For the load case stumbling the mean fracture load was 6743 N and two different mechanisms leading to fracture could be identified: high subsidence with low femoral bending and small subsidence with high femoral bending. For the load case sideways fall the mean fracture load was 1757 N and both tested femurs fractured due to a rotation of the hip stem around its own axis. The detailed datasets provided by this study can be used in future computational models. We demonstrated that the underlying fracture mechanisms of periprosthetic femoral fractures can be fundamentally different in the load case stumbling. The seating and exact position of the hip stem in the femur may correlate with implant subsidence and therefore lead to different types of fracture mechanisms resulting in different patient-specific fracture risks. • Early periprosthetic femoral fractures were experimentally reproduced. • Measurement of displacements, strains, stresses, fracture loads and subsidence. • Two fundamentally different fracture mechanisms could be observed during stumbling. [ABSTRACT FROM AUTHOR]

Fit accuracy and fracture strength of milled monolithic zirconia (Zi) and zirconia-reinforced lithium silicate (ZLS) crowns are important parameters determining the success of these restorations. This study aimed to evaluate and compare the marginal and internal fit of monolithic Zi and ZLS crowns, along with the fracture load, with and without mechanical aging. Thirty-two stone dies acquired from a customized master metal molar die were scanned, and ceramic crowns (16 Zi Ceramill Zolid HT+ and 16 ZLS Vita Suprinity) were designed and milled. Absolute marginal discrepancies (AMD), marginal gaps (MG), and internal gaps (IG) of the crowns, in relation to the master metal die, were evaluated using x-ray nanotomography (n = 16). Next, thirty-two metal dies were fabricated based on the master metal die, and crowns (16 Zi; 16 ZLS) cemented and divided into four groups of eight each; eight Zi with mechanical aging (MA), eight Zi without mechanical aging (WMA), eight ZLS (MA), and eight ZLS (WMA). Two groups of crowns (Zi-MA; ZLS-MA) were subjected to 500,000 mechanical cycles (200 ± 50 N, 10 Hz) followed by axial compressive strength testing of all crowns, until failure, and the values were recorded. Independent sample t tests (α = 0.05) revealed no significant differences between Zi and ZLS crowns (p > 0.05); for both internal and marginal gaps, however, there were significant differences in AMD (p < 0.005). Independent samples Mann–Whitney U and Kruskal–Wallis tests revealed significant differences between the two materials, Zi and ZLS, regardless of fatigue loading, and for the individual material groups based on aging (α = 0.05). Multiple comparisons using Bonferroni post-hoc analysis showed significant differences between Zi and ZLS material groups, with or without aging. Within the limitations of this study, the ZLS crown fit was found to be on par with Zi, except for the AMD parameter. As regards fracture resistance, both materials survived the normal range of masticatory forces, but the Zi crowns demonstrated greater resistance to fracture. The monolithic Zi and ZLS crowns seem suitable for clinical application, based on the fit and fracture strength values obtained. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The purpose of this laboratory study was to compare the frequency of failures (complete fractures or partial cracks) of molar crowns made of two different all-ceramic materials during dynamic loading in a chewing simulator, as well as the fracture load when subjected to static loading, in relation to different dynamic loading and luting protocols. Methods: One hundred and forty-four molar crowns fabricated with IPS Empress or an experimental e.max Press material with high translucency (e.max Press Exp) were luted on CAD/CAM milled PMMA abutments (first lower molar, circular chamfer) either with Variolink or glass-ionomer cement (GIC). All crowns were loaded according to three different loading protocols (n =12 per group) and two force profiles (sinusoidal, rectangular) in a pneumatically driven chewing simulator with a steel stylus (Ø 8mm) and they underwent simultaneous thermocycling (5°C/55°C). After each phase the crowns were evaluated with regard to fractures or cracks. After dynamic testing, the crowns that did not fail were subjected to compression loading until complete fracture in a universal testing machine (UTM). As control groups, unloaded crowns were also subjected to a UTM. Survival statistics with log-rank tests were applied for the results of the dynamic loading, while ANOVA with post hoc Tukey B was used for the fracture load results and two-way ANOVA was carried out for logarithmically transformed data. Weibull statistics were calculated for pooled fracture load data of the dynamically loaded and control groups. Results: In the 144 IPS Empress crowns, complete fractures were observed in 9 crowns and partial cracks in another 3 crowns. When the data was pooled, a statistically significant increase in fractures occurred when the sinusoidal force profile was applied compared to a rectangular force profile (log-rank, p <0.05). No fractures occurred in the e.max Press Exp crowns. The two-way ANOVA showed that the type of luting protocol used had the most significant effect on the fracture load of both materials. In conjunction with Empress, however, the luting material influenced the variability twice as much as in e.max Press Exp. There was no statistically significant difference in the fracture load of GIC-luted e.max Press Exp crowns and that of the Variolink luted Empress crowns. The force profile had a significant effect on the fracture load only of the Empress crowns but not of the e.max Press Exp crowns. Weibull statistics revealed a higher scattering of the data of dynamically loaded crowns compared to that of the control groups. Conclusions: For testing all-ceramic materials, dynamic loading is indispensable to draw valid conclusions on clinical performance of all-ceramic molar crowns. A sinusoidal profile is advisable, while a gradual increase of the force amplitude does not significantly affect the results. [Copyright &y& Elsevier]

Purpose: A common problem associated with implant-supported prostheses is the fracture of denture teeth. This study was designed to compare the fracture modes of three denture teeth by compressive load at a 30° off-axis angle. Material and Methods: Three denture teeth (Vident Duostat, Ivoclar Vivadent, and Dentsply Trubyte) processed to two denture base processing systems [injection-molded (IM) SR-Ivocap system and compression-molded (CM) denture base resin] were evaluated. Each specimen was processed to a metal framework. Ultimate failure strength of each system when point loaded at a 30° off-axis angle was recorded, along with a visual inspection of each specimen. Results: The average load fracture for each group was (in N): Vident CM 1106.97 ± 223.20, Vident IM 1168.18 ± 322.52, Dentsply CM 1098.08 ± 286.32, Dentsply IM 1023.80 ± 282.45, Ivoclar CM 1616.98 ± 204.87, and Ivoclar IM 1373.54 ± 282.58. There was a significant difference between the groups and the Ivoclar CM group. The Ivoclar CM group had the highest average load force, and the Dentsply IM group had the lowest average load force. On average, the teeth within the groups fractured at a higher compression force than the average maximum occlusal force in natural dentition. Dentsply and Vident denture teeth fractured more horizontally, and the Ivoclar denture teeth fractured more vertically within the groups. There was no significant difference among the groups between the IM and CM processing methods. Conclusions: In the present in vitro study, all specimens were able to withstand 30° off-axis loading with the exception of one specimen. With these results, this would indicate that these denture teeth are able to withstand normal occlusal forces. [ABSTRACT FROM AUTHOR]

The probability of in-vivo failure of ceramic hip joint implants is very low (0.05–0.004 per cent). Besides material flaws and overloading, improper handling during implantation may induce fractures of the ceramic ball head in the long term. This study focuses on the influence of contaminants located in the stem–ball interface and on the use of damaged metal tapers on the strength of ceramic ball heads. Mechanical tests on alumina ball heads according to the standard ISO 7206-10 were performed to identify their effect on the static fracture load. A decrease of up to 90 per cent with respect to the reference static fracture load was found when contaminants such as bone chips, soft tissue, or blood were present. Reductions of 57 per cent and 27 per cent were observed for deformed stem cross-sections (from circular to elliptical) and for flattened stems respectively, making deformed stems another influential parameter. Since any alteration of the interface between the metal taper and the ceramic ball head yields a non-uniform load introduction and hence results in stress concentrations, its presence has to be avoided. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The purpose of this in vitro study was to compare the quasi-static (QSFS) and fatigue fracture strength of all-ceramic resin-bonded three unit inlay-retained fixed partial dentures (IRFPDs) made from a heat-pressed lithium-disilicate based glass-ceramic (LDGC) and a CAD/CAM-manufactured yttrium-oxide partially stabilized zirconia framework (YPSZ). Methods: Identical IRFPD-models of the maxilla were used. They consisted of a second premolar, a missing first molar and a second molar (Co–Cr–Mo alloy) integrated in a low melting alloy base. Roots were covered with a soft silicone-layer to simulate an artificial parodontium. Premolars had an occlusal-distal inlay-preparation and molars a mesial-occlusal inlay-preparation. Thirty-two IRFPDs were made from each ceramic using two different connector dimensions: 3mm×3mm (LDGC_9, YPSZ_9); 4mm×4mm (LDGC_16, YPSZ_16). All IRFPDs were cemented adhesively to the IRFPD-models, using composite resin cement. QSFS was tested in a universal-testing-machine (UTM) for six specimens. The other specimens were fatigued either with cyclic loading at 250N (n =4) in a chewing simulator or at 600N (n =6) using the UTM, and group YPSZ additionally at 1500N. Results: The medians of QSFS (N) were 960 (LDGC_9), 1316 (LDGC_16), 3180 (YPSZ_9) and 3120 (YPSZ_16). For both QSFS and cyclic loading significant differences were found between LDGC_9 and LDGC_16 (p ≤0.03) but not between YPSZ_9 and YPSZ_16 (p >0.05). Differences between LDGC and YPSZ were significant for both connector sizes (p ≤0.001). Significance: Considering the maximum chewing forces in the molar region it seems clinically possible, to use YPSZ as a core material for IRFPDs with a connector size between 9 and 16mm2. [Copyright &y& Elsevier]

Thermal misfit is deemed as one reason for the chipping of veneered zirconia restorations. Aim of the present study was to assess the effect of thermal misfit on the fracture load of veneered zirconia frameworks and to evaluate the applicability of a universal veneering ceramic for both zirconia and titanium frameworks. Fracture loads of zirconia and titanium frameworks veneered with different ceramics were measured. Differences in the thermal expansion coefficients of core and veneer (Δα), as well as differences between glass transition temperatures of the veneering ceramics and room temperature (ΔT)—which is considered as the effective temperature range for stress formation, were determined. In the zirconia group, fracture load ranged from 818.0±127.2 to 935.2±186.3 N without significant differences (Student's t-test, p<0.05). Moreover, zirconia and titanium crowns veneered with the universal veneering ceramic revealed high fracture load. Results also showed a correlation to the product Δα · ΔT, such that if 185 · 10-6<· α · ΔT<1120 · 10-6, a veneering ceramic adapted for titanium might be likewise applicable for zirconia. [ABSTRACT FROM AUTHOR]

This study evaluated the fracture loads of three-unit all-ceramic bridges on implants; the core frameworks of the bridges were made of zirconium oxide. Three core framework designs were fabricated according to the design of the bars between the retainers: (i) straight, (ii) curved in the occlusal direction, or (iii) curved in the gingival direction. A static load was applied at the centre of the pontic, and the mean initial crack and final fracture loads were measured and compared. The core framework curved in the occlusal direction had the highest final fracture loads; there were significant differences ( P < 0·05) in the mean final fracture load, whereas initial fracture load, which fractured of veneered porcelain, did not show significant differences among three designs. The all-ceramic bridges on the implants made with Procera zirconium core frameworks had high final fracture load. The core framework design that curved in the occlusal direction helped the framework withstand the occlusal load, which results in reliable prostheses, especially in the molar region. [ABSTRACT FROM AUTHOR]

Abstract: Objective: The aim of the present study was to investigate the influence of the rigidity of different post materials (titanium versus glass fiber reinforced composite [FRC]) on the fracture resistance of endodontically treated teeth (ETT). Method: Forty-eight caries-free maxillary central incisors were randomly assigned to six groups (n =8). After endodontic treatment, teeth of four groups were flattened 2mm above and two groups at the cemento-enamel junction (CEJ). As control, specimens of one group received neither composite build-up nor post, and teeth were left empty (E). In another group only a resin composite build-up was placed (C). In two groups, both titanium and FRC posts were inserted. One group with titanium (2/T) and FRC (2/FRC) post received a 2mm deep ferrule preparation. For one group with titanium (0/T) and FRC (0/FRC) post no ferrule design was provided. All-ceramic crowns were adhesively luted on all specimens. Specimens were exposed to thermomechanical loading and finally statically loaded until failure. Results: The median fracture load values (min–max) were: E=317 (242–404); C=387 (335–475); 0/FRC=352 (0–440); 2/FRC=502 (326–561); 0/T=420 (0–548), 2/T=517 (416–653). Statistically significant differences were computed between E, C, 2/FRC, 0/T and 2/T; between C, 2/FRC and 2/T; between 0/FRC, 2/FRC and 2/T; between 0/T and 2/T regarding maximum fracture load. Significance: Fracture resistance of ETT is not influenced by the rigidity of the post material. The combination of ferrule preparation and endodontic post results in higher load resistance after TML than any other build-up design. [Copyright &y& Elsevier]

Abstract: Objectives: The aim of the present investigation was to study the influence of a reduced bone support on the fracture resistance of endodontically treated teeth restored with glass fibre-reinforced posts (FRC). Methods: 30 caries-free maxillary central incisors were divided into 3 groups (n =10). Endodontic treatment was performed. Teeth were flattened 2mm above the cemento–enamel junction. Group I (control) simulated a clinical situation without horizontal bone loss. In group II a horizontal bone loss of 25% and in group III of 50% was simulated. All specimens received FRC posts and composite core restorations. All-ceramic crowns were adhesively cemented. Specimens were exposed to thermal cycling and mechanical loading (TCML) and finally statically loaded until failure in a universal testing machine ( =1mm/min). Non-parametric tests were used to compare median fracture loads between groups. Fracture modes were compared using Fisher''s exact test. Results: The median fracture load values (min/max) in [N] were: group I=501 (326/561), group II=422 (323/495); group III=352 (266/406), p =0.004. Two specimens in each group II and III failed during TCML. Statistical analysis revealed statistically significant differences between all test groups regarding maximum fracture load and mode of fracture. Conclusions: The fracture resistance of endodontically treated teeth restored adhesively with a FRC post, composite core, and all-ceramic crown is dependent on the level of surrounding supporting periodontal bone. Loss of alveolar bone loss due to periodontal disease may lead to an increased risk of failure. [Copyright &y& Elsevier]

The aim of this in vitro study was to evaluate the fracture load and marginal accuracy of crowns made from a shrinkage-free ZrSiO4 ceramic cemented with glass–ionomer or composite cement after chewing simulation. Thirty-two human mandibular molars were randomly divided into two groups. All teeth were prepared for and restored with shrinkage-free ZrSiO4 ceramic crowns (Everest HPC®, KaVo). The crowns of group A ( N = 16) were luted to the teeth using KetacCem® and group B ( N = 16) were adhesively cemented using Panavia®21EX. Measurements of the marginal accuracy before and after cementation were made using replicas and an image analysis system. All specimens were exposed to 1·2 million cycles of thermo-mechanical fatigue in a chewing simulator. Surviving specimens were subsequently loaded until fracture in a static testing device. Fracture loads (N) were recorded. All specimens survived chewing simulation. The mean fracture loads (±s.d.) were Group A, 1622 N (±433); group B, 1957 N (±806). There was no significant difference between the two groups ( P > 0·05). The marginal gap values before cementation were (mean ± s.d.): Group A, 32·7 μm (±6·8); group B, 33·0 μm (±6·7).The mean marginal gap values after cementation were (±s.d.): Group A, 44·6 μm (±6·7); group B, 46·6 μm (±7·7). The marginal openings were significantly higher after cementation for both groups ( P < 0·05). All test groups demonstrated fracture load and marginal accuracy values within the range of clinical acceptability. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The mechanical properties of zirconia ceramics are affected of stabilizing oxides and quality of sintering. The purpose of this study was to investigate the fracture resistance of frameworks manufactured using prefabricated zirconia blanks with differing stabilizing oxides and quality of sintering. Methods: After dynamic loading in water, the fracture resistance was determined of stylized three-unit fixed partial dentures made of prefabricated homogenous ceramic green-body yttria-stabilized zirconia (Y-TZP) blanks (Vita YZ) or of densely-sintered magnesia partially stabilized zirconia (Mg–PSZ) blanks (Denzir-M); (i) as supplied from the manufacturer, (ii) after subjection to heat treatment in a way similar to veneering, and (Hi) after veneering with a feldspar-based ceramic. Results: After veneering, the load at fracture of the Vita YZ specimens was significantly higher (p <0.05) than that of Denzir-M. The load necessary to fracture Denzir-M as supplied after machining was significantly (p <0.05) higher than that of heat-treated Denzir-M, Vita YZ as supplied and heat-treated Vita YZ specimens. There was no significant difference (p >0.05) between the heat-treated and veneered Denzir-M specimens. For Vita YZ the load at fracture of the veneered specimens was significantly (p <0.05) higher than of those as supplied or heat-treated, whereas no significant difference (p >0.05) was seen between heat-treated Vita YZ and Vita YZ specimens as supplied. Significance: The fracture strength of the Vita YZ specimens increased considerably after veneering. Denzir-M and Vita YZ seem to be interesting alternatives for use as core materials in all-ceramic restorations. Long-term studies are, however, necessary before general clinical recommendations can be issued. [Copyright &y& Elsevier]

The strength and fracture pattern of posterior CAD/CAM-generated crown copings with 0·4 mm wall thickness were evaluated in vitro hypothesizing that fracture resistance of YTZP-zirconia copings might be independent of mode of cementation whether resin-bonded or cemented because of the high strength of YTZP-zirconia. Two sets of copings ( n = 15) each were fabricated using CEREC inLab CAD/CAM from (i) lithiumdisilicate glass–ceramic, (ii) infiltration ceramic as controls and (iii) YTZP-zirconia. Copings ( n = 15) of ceramics (i), (ii) and (iii) each were (a) zinc–phosphate cemented, (b) adhesively seated on resin-based composite dies and loaded until fracture. Load (N) data was analysed usinganova and Scheffé tests. Crack pattern was evaluated on additional three sample cross-sections for each group at fracture-start. Radial cracks originated early at the cementation interfaces and cone cracks were observed finally at the loading sites. Mean load (N) values (±s.d.) of A-copings at fracture-start/-end (i) 804 ± 195/862 ± 162, (ii) 923 ± 180/975 ± 147, (iii) 697 ± 110/1607 ± 145, were all significantly ( P < 0·01) lower when compared with their B-crown coping analogs (i) 1183 ± 318/1919 ± 326, (ii) 1621 ± 165/1820 ± 211, (iii) 731 ± 115/1973 ± 287 except for A3 and B3 at fracture-start. This confirmed our hypothesis at fracture-start ( P > 0·05) but rejected it at fracture-end ( P < 0·01). The A3 fracture-end data, even if significantly ( P < 0·01) lower, came close to the B3 values by 18%. A3 was significantly ( P < 0·001) stronger by 86/74% than A1/A2 at fracture-end. The data indicates that YTZP-zirconia copings have the potential to provide support for all-ceramic core crowns, which may be adequate for non-adhesive cementation. [ABSTRACT FROM AUTHOR]

Summary: Objectives: The present study was designed to test the null hypothesis that there is no difference in the fracture resistance of pulpless teeth restored with different types of post-core systems and full coverage crowns. Methods: Extracted human upper premolars were restored with a fiber post, prefabricated metallic post or cast metallic post-core. Teeth with full crown preparations without post-core restorations served as a control. All teeth were restored with full coverage crowns. A 90-degree vertical or 45-degree oblique load was applied to the restored teeth with a crosshead speed of 0.5mm/min, and the fracture loads and mode of fracture were recorded. Results: Under the condition of vertical loading, the fracture load of teeth restored with the cast metallic post-cores was greatest among the groups (two-factor factorial ANOVA and Scheffe''s F test, P<0.05). All fractures in teeth restored with all types of post-core systems propagated in the middle portions of roots, including the apices of the posts. Under the condition of oblique loading, the fracture load of teeth restored with pre-fabricated metallic posts was significantly smaller than that in other groups. Two-thirds of fractures in the fiber post group propagated within the cervical area, while most fractures in other groups extended beyond the middle of the roots. Significance: From the results of the present investigations, it was concluded that under the conditions of vertical and oblique loadings, the combination of a fiber post and composite resin core with a full cast crown is most protective of the remaining tooth structure. [Copyright &y& Elsevier]

In this study, the effect on the fracture load of inlay-retained composite fixed partial dentures (FPDs) caused by reinforcing them with fiber-reinforced composite (FRC) in different positions was examined. Experimental FPDs were fabricated using Estenia/EG Fiber (Kuraray Medical). Pontic reinforcement was then performed in one of the following three ways: reinforced the central area in a single line or in double straight lines, or reinforced the bottom in a curved line. The finding was that, when the area ranging from the connector to the bottom of the pontic was reinforced with FRC in a curved line, the fracture load of the FPDs tended to become higher. In addition, the FPDs fractured mainly at the veneering composite of the connector area. Based on the results of this study, it was concluded that reinforcement using FRC is effective, and that the veneering composite in the connector area needs to have sufficient strength to prevent the fractures. [ABSTRACT FROM AUTHOR]