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The purpose of this study was to compare the compressive strengths and compressive fatigue limits of three posterior composite resins (Filtek P-60, Surefil and Prodigy Condensable) and a universal restorative composite (Z-100). Cylindrical specimens (8 mm in length x 4 mm in diameter) were used. The dynamic test was performed using the staircase method, and the ratio between compressive fatigue limit and compressive resistance was also calculated (n = 15). The compressive strength and compressive fatigue limit data were analyzed by Anova and Tukeys test. The Z-100 composite demonstrated higher compression strength (307.20 MPa) than Surefil (266.93 MPa) and Prodigy Condensable (222.08 MPa). The resistance of Filtek P-60 (270.44 MPa) was similar to the resistances of Z-100 and Surefil, while Prodigy Condensable presented the lowest compressive strength. In the compressive fatigue limit tests, Filtek P-60 demonstrated a higher value (184.20 MPa) than Prodigy Condensable (155.50 MPa). Surefil (165.74 MPa) and Z-100 (161.22 MPa) presented limits similar to those of Filtek P-60 and Prodigy Condensable. The compressive fatigue limit/compressive strength ratio was 70.01% for Prodigy Condensable, 68.11% for Filtek P-60, 62.09% for Surefil and 52.48% for Z-100. It was concluded that the Z-100 universal composite was more sensitive to the dynamic test than the high viscosity materials.
Compressive strength measurements were conducted on 32 macroporous biphasic calcium phosphate (MBCP) samples to evaluate the influences and interactions of five synthesis factors: chemical composition, percentage of macropores, mean size of macropores, isostatic compaction pressure, and sintering temperature. These parameters were varied simultaneously between two limit levels. Experiments used a factorial design method (FDM) allowing optimization of the number of samples as well as statistical analysis of results. FDM showed that compressive strength, in a defined experimental area, can be described by a first-order polynomial equation in which the percentage of macroporosity and sintering temperature are the major influences. This study leads up to an isoresponse line diagram that will allow the manufacture of some classes of MBCP with fitted compressive strength.
The diametral tensile strength (DTS) and compressive strength (CS) of a calcium phosphate cement comprised of tetracalcium phosphate and dicalcium phosphate anhydrous were studied. Cement powder and water were mixed at a powder/liquid ratio of 4.0. The resulting cement pastes were placed in molds and a pressure ranging from 0-2.8 MPa was applied for various lengths of time (0.5-24 h). DTS and CS measurements were conducted on 24-h wet samples. The strength was found to be significantly (p<0.05) affected by the pressure but not by the time. Samples prepared under a pressure of 0.7 MPa had a mean DTS value of 10.8+/-1.0 MPa (n = 5), which is comparable to the values reported in the literature for the same cement prepared under similar conditions. In contrast, the mean CS value obtained in the present study, 66.1+/-5.0 MPa (n = 5), was significantly higher than the value (51+/-4.5 MPa) previously reported. The higher CS may be attributed to an improved mold design that may reduce sample damage during demolding, and to the use of a loading device that applied a constant pressure to the sample during setting. The average standard deviation of the mean for the 19 DTS sample groups (n = 5 in each group) was 1.1 MPa, corresponding to 9.6% of the mean DTS value. The average standard deviation of the 7 CS sample groups (n = 5 in each group) was 4.5 MPa, corresponding to 7.1% of the mean CS value. Published 2000 John Wiley & Sons, Inc.
OBJECTIVES: This investigation sought to improve the handling and physical properties of a commonly used temporary zinc oxide-eugenol cement by changing the base/accelerator (B/A) ratio or combining it with a petroleum jelly or fluoride varnish. METHODS: Twelve modifications of a temporary cement were evaluated in terms of retentive strength, compressive strength at 24 h, film thickness and by scanning electron microscopy. RESULTS: Decreasing the B/A mixing ratio increased the retentive and compressive strengths, but reduced the film thickness of the cement. By increasing the percentage of incorporated petroleum jelly or fluoride varnish in the cement, there was a progressive decrease in the retentive and compressive strengths and in film thickness. CONCLUSIONS: Modifications of a zinc oxide-eugenol temporary cement to change the B/A ratio or to incorporate additives resulted in variations in physical properties. All modified forms of the cement had a film thickness less than 25 microns and a compressive strength below 35 MPa. With a wide range of retentive strength, modified forms of zinc oxide-eugenol cement may be found to have diverse clinical applications.
This study compared three mechanical properties of two recently introduced core materials, a light-activated glass ionomer cement (VariGlass VLC) and a fluoride-release dual cure composite resin (FluoroCore), with those of a conventional silver-reinforced glass-ionomer cement (Miracle Mix). Seventy-two samples (eight per product for each property) were prepared for testing diametral tensile strength, flexural strength, and compressive strength. The specimens were cured, stored for 24 hours at 37 degrees C in 100% humidity, and tested with the use of an Instron universal testing machine. The results of this study indicate that the diametral tensile strength, flexural strength, and compressive strength of the FluoroCore and VariGlass VLC materials were significantly higher than those of the conventional Miracle Mix. The values obtained with FluoroCore material were consistently higher than those obtained with VariGlass VLC material.
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INTENTION OF THE STUDY: Explanations concerning the physical properties of hyaline cartilage are different. It was the intention of this study to determine the material parameters of hyaline cartilage under axial load (elasticity, plasticity, elasticity and module pressure stress to break). METHODS: Specimens from the medial femoral condyle (chondro-cortical ships) from adult female domestic pigs (n=28) were used for the experiments. The specimens were completely embedded in plaster to minimize shearing. Axial load was carried out by an universal mechanical testing machine (Zwick Z2.5/TS1S, Ulm, Germany) to determine elastic and plastic deformation and pressure stress to break. RESULTS: Axial load up to 5 MPa produces an almost elastic deformation, an increasing axial load results in a plastic deformation. In the range of 3 to 5 MPa the principle of Hooke is valid. The elasticity module amounted to 39.2 +/- 11.9 N/mm(2), determined under 3.8 MPa axial load. An axial load of 25.8 +/- 5.2 MPa (sigma max ) causes a break of cartilage. A strong correlation between break resistance and thickness of the chondral slice (r=0.71; p < 0.05) was observed. CONCLUSIONS: The low module of chondral elasticity characterizes this tissue as "soft". Moderate axial load causes an ideal elastic, higher axial load a plastic deformation. The medium pressure to break to amounted 25.8 MPa. The medium pressure to break of 25.8 MPa is comparable with the forces produced by an unrestrained limited downfall from a height of 4.3 m. It must be concluded that isolated chondral fractures are rare consequences of a trauma as long as accompanying ligamentous or osseous damages are not found.
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Three thoracic (T5-T7) and three lumbar (L1-L3) vertebral bodies and the anterior parts of both iliac crests were removed from 44 normal individuals aged 15-87 years who had died suddenly. Small, cylindrical samples of trabecular bone (length 5 mm, diameter 7 mm) from T6, L1, and L3 and from the standard site for iliac crest biopsies were compressed in an Alwetron-250 materials testing machine. Whole vertebral bodies from T5, T7, and L2 with cut planoparallel end-plates were compressed in an Instron materials testing machine. The maximum compressive stress value sigma max of the whole vertebral bodies and of the vertical vertebral trabecular bone decreased with age with almost parallel linear regression lines. At any age the sigma max for whole vertebral bodies was about 1.6 MPa (1 MPa = 100 N/cm2) higher than for the trabecular bone. The average cross-sectional area of the vertebral bodies increased by 25-30% from the age of 20 to 80 years. The anisotropic properties of the vertebral trabecular bone (expressed as the ratio between the vertical and horizontal sigma max) increased markedly with age. A highly significant positive correlation was observed between the vertical vertebral trabecular bone sigma max (X) and the total vertebral body sigma max (y = 0.90x + 1.75, r = 0.88, P less than 0.01). The slope was not significantly different from 1, whereas the intercept was positive (P less than 0.01). The average total vertebral body sigma max (range 1.5-7.8 MPa) could be predicted from mechanical tests on horizontal iliac crest bone biopsies with standard error of estimate (SEE) of 0.92 MPa.(ABSTRACT TRUNCATED AT 250 WORDS)
Compressive strength is widely used as the criterion of strength of glass-ionomer dental cements, despite the difficulties in interpretation of the findings. With the introduction of light-cured glass-ionomer cements, which can be used only in thin layers, the question arises of how test specimens should be prepared for the measurement of compressive strength. A suggested method has been to prepare test pieces by building them up in layers, an approach which is examined critically in the current paper. Two different conventional (acid-base) glass-ionomers were studied with the use of layered and unlayered specimens of dimensions 6 mm (height) x 4 mm (diameter) and 12 mm (height) x 6 mm (diameter). While smaller samples gave the same value of compressive strength as larger specimens, layered specimens gave significantly lower values of compressive strength for both sizes. In view of these findings, and since the layered specimens are tedious to prepare, we conclude that compressive strength is unsatisfactory as a criterion of strength for light-cured glass-ionomer cements.
The compressive strength of five different amalgams was measured at one hour, six hours, 24 hours, and seven days, and X-ray diffraction analysis was carried out for each amalgam at the same times in order to investigate the early strength characteristics of the amalgams in relation to the formation of different phases. At 24 hours all tested amalgams reached about 90% or more of their seven-day compressive strength, but the increase in the early compressive strength from one hour to 24 hours varied between different amalgams. Two of the five amalgams tested reached about 90% of their seven-day compressive strength at six hours. A significant correlation was found between the ratio of early compressive strength to seven-day compressive strength, and the X-ray diffraction intensity ratio (ratios of one-, six- and 24 hour intensity to seven-day intensity) for the gamma 1 phase, indicating that the increases in early compressive strength are mainly dependent upon the formation of gamma 1.
In the present study, the compressive strength of four representative dental investment materials was compared. The whole investigation was divided in three experiments. In the first one the effect of different ways of mixing on the compressive strength of the investments was examined. In the second the compressive strength of investments mixed mechanically under vacuum was compared: a) two hours after mixing, b) at the highest heating temperature and c) at room temperature after the heating procedure. In the third experiment, a comparison was made between the compressive strength of investments at the highest heating temperature. The investments were mixed mechanically under vacuum but half of the specimens were placed in a pressure device during setting. From the results obtained the following conclusions were made: a) Mixing mechanically under vacuum increases the compressive strength of the investments, b) the compressive strength of phosphate-bonded investments increases at the highest temperature of the heating procedure and c) the use of a pressure device during the setting of the investments results also in an increased compressive strength.
STUDY DESIGN: A human cadaveric study on the compressive strength of different lumbar interbody fusion implants and endplate preparation techniques was performed. OBJECTIVES: To assess the axial compressive strength of an implant with peripheral endplate contact as opposed to full surface contact, and to assess whether removal of the central bony endplate affects the axial compressive strength. SUMMARY OF BACKGROUND DATA: The compressive strength of interbody fusion constructs has been compared between implants and bone grafts. Neither implant design nor endplate preparation has been shown to affect strength. Removal of the central bony endplate for bone grafts was noted to improve graft incorporation but also to facilitate subsidence. METHODS: A total of 44 vertebrae were tested in four experimental groups by combining two interbody implants (full-surface vs peripheral surface support) with two endplate preparation techniques (intact bony endplate vs removal of the central bony endplate). Specimens were tested to ultimate compressive failure using a 50 N/second ramped load. Yield strength and ultimate compressive strength were compared between groups using two-factor analysis of covariance. A P value less than 0.05 was considered significant. Stepwise linear regressions assessed the predictive power of age, bone mineral content, and the implant's normalized endplate coverage on yield strength and ultimate compressive strength. RESULTS: Neither implant design nor endplate preparation technique affected yield strength or ultimate compressive strength. Age, bone mineral content, and the normalized endplate coverage were strong predictors of yield strength (P < 0. 0001; r2 = 0.459) and ultimate compressive strength (P < 0.0001; r2 = 0.510). CONCLUSIONS: An implant with only peripheral support resting on the apophyseal ring offers axial mechanical strength similar to that of an implant with full support. Neither supplementary struts nor a solid implant face has any additional mechanical advantage, but reduces graft-host contact area. Removal of the central bony endplate is recommended because it does not affect the compressive strength and promotes graft incorporation.
PURPOSE: This study analyzed the correlation between the compressive strength of human thoracolumbar vertebrae, bone density and endplate area (measured by SE-QCT). METHOD: The compressive strength of 110 human vertebral specimens (D11-L5) was measured. In order to determine standard values for human vertebral specimens from each level and different female and male age groups were examined. Before biomechanical testing the specimens were examined using SE-QCT with 1.5 and 10 mm slice thickness. Three different slice locations (mid-vertebral and adjacent to both endplates) and 6 regions of interest (ROI) were chosen to assess BMD. The area of the vertebral endplates was measured by CT. RESULTS: Highest correlations between BMD and compressive strength were found for the 10 mm thick midvertebral slices with a small ellipsoid ROI. Cancellous and cortical bone contributed to the compressive strength to the same amount. Compressive strength and endplate area increased in the cranio-caudal direction, bone density was constant throughout thoracolumbar spine. Bone density and compressive strength depended on age and sex. Compressive strength of human thoracolumbar vertebrae increased with bone density as well as the size of the endplates. CONCLUSIONS: Using bone density and endplate area (SE-QCT) of human thoracolumbar vertebrae (D11-L5) a prediction of compressive strength is possible with an error of estimation of 1.17 kN and a correlation factor of 0.85. The prediction of the compressive strength allows an estimation of the risk of vertebral fracture, i.e. in patients with osteoporosis or in individuals with intensive physical activities. The standard values of the human thoracolumbar vertebrae together with biomechanical examinations of vertebral metastases can be used to estimate the compressive strength of osteolytic and osteoplastic spinal metastases.
In this study, we investigated compressive strength of various luting cements and composite resin cores in both dry and wet condition, and then influences of repeating load on compressive strength in wet condition of distilled water at 37 degrees C. As frequency of repeating load increased, compressive strength of all materials decreased. It means that the repeated load cycling test used in this study is adequate for evaluating durability of various dental materials. The results were as follows: 1. In the condition of no loading in both dry and wet condition, resin cement indicated the highest compressive strength of all cements examined and was followed by glass ionomer cement, zinc phosphate cement and polycarboxylate cement. Glass ionomer cement was notably influenced in wet condition. 2. After 10,000 cycles of loading in wet condition, resin cement indicated the highest compressive strength again and was followed by glass ionomer cement, polycarboxylate cement and zinc phosphate cement. In particular, compressive strength of zinc phosphate cement decreased remarkably. 3. In the condition of no loading, visible light-cured composite resin core was superior to chemical one. Visible light one was notably influenced in wet condition. 4. After 10,000 cycles of loading, visible light-cured composite resin core was superior to chemical one.
OBJECTIVE: Compressive strength of four filling materials which are usually used in clinic were evaluated, and the indication of Class I cavity was discussed. METHODS: In vitro, the Class I cavities were prepared on eighty first molars. After filling the cavities with four filling materials, loading was applied with the same speed, and the compressive strength at the fracture point were recorded and analyzed. RESULTS: The compressive strength of silver amalgam was highest, GCFujiIXGP was lower, and 3M composite resin was lowest. CONCLUSION: For Class I cavity of posterior teeth, we should consider the compressive strength of filling materials first, and for anterior teeth, color is most important.
Compressive strength measurement and microstructure studies of standard, diamond bur-ground, and fracture surfaces of durapatite cones were reported. The compressive strength measurements of durapatite cones were variable and strongly dependent on the test method. The fracture force ranged from 1090 to 3692 N and the calculated compressive strengths ranged from 113 (16,333 psi) to 389 mN/m2 (56,462 psi). The outer surface of durapatite cones was rough, irregular, and dense. Sharp fracture lines occurred along the longitudinal axis of the cones. Isolated porosity was seen in the fracture surface of one specimen. Grinding hydroxyapatite cones using a high-speed diamond bur with water spray produced a surface grinding feature, an irregular surface topography, and microcracks. The microcrack directions were perpendicular to the direction of the diamond bur cutting features.