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PubMed1999

Determination of the elastic modulus of resin based materials as a function of resonance frequency during polymerisation.

OBJECTIVES: The aim of this investigation is to describe the development of a novel non-invasive technique to measure the change in the elastic modulus of resin based restorative materials during polymerisation using resonance frequency analysis. METHODS: A transducer was developed which was designed to resonate at its first natural frequency in the range 5-15 kHz. The transducer was excited electronically and the response measured using a frequency response analyser. The transducer was mounted in a specimen well containing a range of test materials including unfilled resins, composites and luting cements. Each test material was polymerised by mixing and/or exposure to a visible light source and the frequency response measured at intervals during the curing process. The resonance frequency was determined at each interval by the measurement of the signal amplitude and phase. RESULTS: The resonance frequency of the transducer-resin system was plotted against time for the different material and curing combinations. Different sampling intervals were selected depending on the test procedure. All results showed a clear increase in resonance frequency as a function of the increase in stiffness and elastic modulus of the material during polymerisation. SIGNIFICANCE: A new non-invasive test method is described which can measure the increase in the elastic modulus of resin based materials as a function of resonance frequency. The technique is not sensitive to temperature, exhibits no drift and does not influence the polymerisation of the test material. Further development should enable resonance frequency measurements to be directly related to elastic material coefficients.

Composite Resins↗

PubMedDate not supplied

Shear bond strengths of 10 adhesive resin/amalgam combinations.

This study compared the shear bond strengths of amalgam to dentin using two amalgam alloys and five adhesive resin systems. One hundred extracted human third molars were flattened occlusally to expose dentin. Dentin surfaces were treated with one of five adhesive resins: All-Bond 2, Amalgambond Plus, Amalgambond Plus with HPA Powder, OptiBond, and Resinomer. Tytin (spherical) or Dispersalloy (admixed) amalgam was condensed onto the treated dentin surface through a Teflon split mold. The samples were stored 7-10 days and thermocycled before shear testing using a Zwick Materials Testing Machine. Two-way ANOVA revealed significant differences among the 10 groups (P < 0.05). The combination of Tytin/OptiBond produced the highest bond strength to dentin (14.17 MPa), while Dispersalloy/Amalgambond Plus produced the lowest (3.89 MPa). In general, the filled resin systems (Amalgambond Plus with HPA Powder, OptiBond, Resinomer) produced higher bond strengths than the unfilled systems (All-Bond 2, Amalgambond Plus). Additionally, for four of the five resins, bond strengths were higher with Tytin than with Dispersalloy, although differences were statistically significant in only two groups.

Adhesives↗

PubMed1998

Accuracy of subsurface temperature distributions computed from pulsed photothermal radiometry.

Pulsed photothermal radiometry (PPTR) is a non-contact method for determining the temperature increase in subsurface chromophore layers immediately following pulsed laser irradiation. In this paper the inherent limitations of PPTR are identified. A time record of infrared emission from a test material due to laser heating of a subsurface chromophore layer is calculated and used as input data for a non-negatively constrained conjugate gradient algorithm. Position and magnitude of temperature increase in a model chromophore layer immediately following pulsed laser irradiation are computed. Differences between simulated and computed temperature increase are reported as a function of thickness, depth and signal-to-noise ratio (SNR). The average depth of the chromophore layer and integral of temperature increase in the test material are accurately predicted by the algorithm. When the thickness/depth ratio is less than 25%, the computed peak temperature increase is always significantly less than the true value. Moreover, the computed thickness of the chromophore layer is much larger than the true value. The accuracy of the computed subsurface temperature distribution is investigated with the singular value decomposition of the kernel matrix. The relatively small number of right singular vectors that may be used (8% of the rank of the kernel matrix) to represent the simulated temperature increase in the test material limits the accuracy of PPTR. We show that relative error between simulated and computed temperature increase is essentially constant for a particular thickness/depth ratio.

Algorithms↗

PubMed2004

Teratogenicity study of some pesticides in chicken embryos.

The use of pesticides involves the risk of poisoning on wild animals. Teratological tests carried out on avian embryos provide useful data for environmental protection and facilitate the development of environment-friendly chemical plant protection techniques. A 30% dimethoate containing insecticide formulation (BI 58 EC) and a 20% benfluralin containing herbicide formulation (Flubalex) and a 960 g/l S-metolachlor containing herbicide formulation (Dual Gold 960 EC) were studied in chicken embryos after single administration by immersion and injection technique. Treatment was done on day 0 of incubation. Applied concentration of pesticides were 0.1% (dimethoate) and 2.05% (S-metolachlor) and 0.375% (benfluralin) corresponding to that used in plant protection practice. Test materials were injected into the air chamber in a volume of 0.1 ml/egg, or eggs were treated by the immersion technique for 30 min. at 37 degrees C. Evaluation was done on day 19 of incubation. Injection treatment: the administration of S-metolachlor and benfluralin did not result a significant decrease in the average body weight of embryos. At the same time the body weight of embryos significantly decreased because of single administration of dimethoate. The embryomortality increased markedly after the administration of test materials (S-metolachlor, benfluralin, dimethoate). Immersion treatment: the administration of S-metolachlor and benfluralin and dimethoate did not result a significant decrease in the average body weight of embryos. The rate of embryomortality was low after the administration of S-metolachlor, benfluralin and dimethoate. After the immersion and the injection treatment the incidences of developmental anomalies were sporadic. In summary it can be established that the injection treatment was more toxic than immersion technique of the test materials in our study.

Animals↗

PubMed1998

Comparison of the strengths of lumbosacral fixation achieved with techniques using one and two triangulated sacral screws.

STUDY DESIGN: The strength of sacral screw fixation achieved with techniques using one sacral screw and two triangulated sacral screws with Chopin block was tested on 10 fresh human sacrum specimens. OBJECTIVES: To compare the stiffness and the failure strength of single sacral screw fixation and those of two divergent triangulated sacral screw fixation under different loading conditions. SUMMARY OF BACKGROUND DATA: Weak sacral screw fixation is the major cause of failure in instrumented lumbosacral fusion. Although previous studies have evaluated the strength of anteromedially and anterolaterally inserted sacral screws, the strength of two divergent triangulated sacral screws has not been evaluated biomechanically. It is assumed that increasing the number of sacral screws and using a triangulated insertion technique may increase the strength of purchase for lumbosacral fixation. METHODS: Ten fresh human sacrum specimens were used in this study. Six specimens were from donors less than 30 years of age (younger group), and the other four were from donors more than 60 years of age (aged group). The specimens were assigned randomly to either one side one S1 pedicle screw inserted anteromedially or to the other side with two screws directed anteromedially and anterolaterally. All specimens were tested with an Instron material testing machine (Instron Limited, High Wycombe, England). The average stiffness under compression, tension, and torsion were calculated from the average slopes of the load deformation curves. The failure load was applied for the final testing. RESULTS: The results showed significant differences in stiffness between fixation with one screw and fixation with two divergent triangulated screws. With one S1 pedicle screw fixation, the average stiffness was 203 N/mm for compression, 147 N/mm for tension, and 2 Nm/degree for torsion. With two-screw fixation the average stiffness increased to 255 N/mm (126%), 185 N/mm (126%) and 2.4 Nm/degree (120%), respectively. The average failure strength under tension loads was found to be 1450 N in the younger specimens and was reduced to 980 N in the aged specimens. CONCLUSION: This study showed that fixation with two divergent triangulated screws to the sacrum was significantly stronger than one-screw fixation for lumbosacral fusion. The strength of fixation seems to have a negative correlation with aging.

Adult↗

PubMed1999

Comparison of the retentive and photoelastic properties of two prefabricated endodontic post systems.

This in vitro study compared the retention and photoelastic stress patterns from two loading conditions, vertical (133.2 N, 30 pounds) and oblique at a 26 degrees angle (133.2 N, 30 pounds) for two prefabricated post systems. The post studied were: (1) Flexi-Post (a split-shank threaded post) and (2) C-Post (a carbon fibre bound in an epoxy resin, passive double taper tier post). Two groups with 10 specimens per group were subjected to retentive forces with a universal testing machine (MTS 810 Material Testing Machine). In addition, two photoelastic test blocks were prepared with simulated root canals for each post studied. After cementation the photoelastic blocks were photographed before vertical and oblique loading and after loading. One-way analysis of variance (ANOVA) for retention data revealed a highly significant difference (P<0.0001) between groups. The Flexi-Post had a statistically higher mean retention force of 1180.6 N (265.9 pounds), while the C-Post had a mean of 171.8 N (38.7 pounds). Photoelastic analysis indicated minimal stresses for both the Flexi-Post and C-Post in the unloaded state. The C-Post showed asymmetrical apically stress patterns, while loaded in both states. The multi-tiered system of the Flexi-Post clearly distributes stress symmetrically, while the C-Post distributes stresses asymmetrically. The symmetric, even stresses and statistically higher retentive strength for Flexi-Post are more favourable than the asymmetric, uneven stresses and relatively low retentive strength for the C-Post.

Analysis of Variance↗

PubMedDate not supplied

A dynamic closed-loop recirculating inhalation chamber for conducting pharmacokinetic and short-term toxicity studies.

Tests for evaluating the hazard of inhalation exposure generally require large quantities of the chemical of interest. This paper describes an inhalation technique that involves a dynamic closed-loop recirculating system which uses only small amounts of toxicant since the test atmosphere to which the animals are exposed is recycled. Carbon dioxide and water are continually removed while the oxygen and test substance absorbed by the animals are replenished. The approach described is different from other closed-loop chambers since the test substance is continuously added to the chamber and the air concentration is continuously measured. The technique was successfully used to expose 20 adult rats for up to 12 consecutive hours to 100 ppm of 14C-carbon tetrachloride yet only 2-3 mL of test material were consumed. The inhalation chambers were fabricated from standard 40-liter cylindrical glass bell jars. A high number of air changes (35-40 equivalent chamber volumes per hour) permitted exposure of as many as five adult rats per 10 liters of chamber volume. This closed-loop approach should prove to be especially useful for evaluating the risk of exposure to very expensive materials or when only limited quantities of a test material are available. These systems may also be used to expose rats and other small animals to radioisotopes in studies which evaluate the uptake, distribution, metabolism, and excretion of volatile xenobiotics.

Animals↗

PubMed1979

Partition coefficients of some aromatic hydrocarbons and ketones in water, blood and oil.

Water/air, blood/air, oil/air, oil/water, and oil/blood partition (or solubility) coefficients of 17 aromatic hydrocarbons and ketones were measured by a newly developed vial-equilibration method, which needs no direct measurements of the concentration either in the liquid or in the air phase, but only the gas chromatographic peak heights of the air in the sample (in which a test material is contained) and reference vessels (containing no test material). It was found that the blood/air partition coefficients for aromatic hydrocarbons are correlated closely with the product of water/air and oil/air partitiion coefficients, whereas those for ketones are almost in the same range as the water/air, irrespective of the oil/air partition coefficients.

Blood↗

PubMed1993

Regulation of factor VIIa/tissue factor functional activity in an umbilical vein model.

Activation of factor IX in an umbilical vein model was established to result solely from factor VIIa/tissue factor (TF) activity generated within the umbilical vein wall, and the model was then used to study regulation of such extravascular factor VIIa-TF complexes. Vein segments were filled with a reaction mixture containing factor VIIa, Ca2+, a substrate, either [3H]factor IX or [3H]factor X, and a test material. Subsamples were assayed for activation peptide release. Test materials included defibrinated plasma or recombinant protein as a source of TF pathway inhibitor (TFPI), recombinant factor VIIa to 10 times plasma factor VII concentrations, and annexin V. A plasma concentration of TFPI inhibited but did not totally suppress factor VIIa/TF activity. Reducing the TFPI concentration by 50% markedly reduced the inhibition. A 10-fold increase in the factor VIIa concentration in reaction mixtures failed to accelerate factor Xa generation. Annexin V, in contrast to its inhibition of factor VIIa/TF formed with TF reconstituted into mixed phospholipid vesicles, failed to inhibit factor VIIa-TF complexes formed within the vessel wall. We conclude that 1) moderate variation in plasma TFPI concentration or activity may affect TFPI's ability to inhibit factor VIIa/TF activity during hemostasis, 2) a plasma concentration of factor VII suffices to saturate TF sites exposed in a vessel after tissue injury, and 3) the resistance of factor VIIa-TF complexes to inhibition by annexin V suggests that they are formed in the umbilical vein model primarily on cell surfaces.

Anions↗

PubMed2003

A new method to measure post-traumatic joint contractures in the rabbit knee.

A new device and method to measure rabbit knee joint angles are described. The method was used to measure rabbit knee joint angles in normal specimens and in knee joints with obvious contractures. The custom-designed and manufactured gripping device has two clamps. The femoral clamp sits on a pinion gear that is driven by a rack attached to a materials testing system. A 100 N load cell in series with the rack gives force feedback. The tibial clamp is attached to a rotatory potentiometer. The system allows the knee joint multiple degrees-of-freedom (DOF). There are two independent DOF (compression-distraction and internal-external rotation) and two coupled motions (medial-lateral translation coupled with varus-valgus rotation; anterior-posterior translation coupled with flexion-extension rotation). Knee joint extension-flexion motion is measured, which is a combination of the materials testing system displacement (converted to degrees of motion) and the potentiometer values (calibrated to degrees). Internal frictional forces were determined to be at maximum 2% of measured loading. Two separate experiments were performed to evaluate rabbit knees. First, normal right and left pairs of knees from four New Zealand White (NZW) rabbits were subjected to cyclic loading. An extension torque of 0.2 Nm was applied to each knee. The average change in knee joint extension from the first to the fifth cycle was 1.9 deg +/- 1.5 deg (mean +/- sd) with a total of 49 tests of these eight knees. The maximum extension of the four left knees (tested 23 times) was 14.6 deg +/- 7.1 deg, and of the four right knees (tested 26 times) was 12.0 deg +/- 10.9 deg. There was no significant difference in the maximum extension between normal left and right knees. In the second experiment, nine skeletally mature NZW rabbits had stable fractures of the femoral condyles of the right knee that were immobilized for five, six or 10 weeks. The left knee served as an unoperated control. Loss of knee joint extension (flexion contracture) was demonstrated for the experimental knees using the new methodology where the maximum extension was 35 deg +/- 9 deg, compared to the unoperated knee maximum extension of 11 deg +/- 7 deg, 10 or 12 weeks after the immobilization was discontinued. The custom gripping device coupled to a materials testing machine will serve as a measurement test for future studies characterizing a rabbit knee model of post-traumatic joint contractures.

Animals↗

PubMed2002

Oxygen permeability (Dk) of thirty-seven rigid contact lens materials.

PURPOSE: Oxygen permeability (Dk) was determined for 37 available rigid contact lens materials in a masked fashion. The results were compared with those of an earlier study that included different lots of 14 test materials assessed in the current study. METHODS: Six lenses of different thicknesses in each test and reference material were obtained. Test materials were arranged in sets of six to eight materials per set. Each set of materials, with inclusion of at least two reference materials for the purpose of simultaneous calibration, was measured to obtain preliminary amperages. Four preliminary measures were performed per thickness, resulting in 24 per material, in a schedule designed to spread the potential effects of machine drift and other factors. The mean preliminary amperages were used to derive corrected Dk values according to American National Standards Institute (ANSI) Z80.20-1998, and the values were linearly calibrated using the measured and established Dk values of the reference materials. RESULTS: The resistance (t/Dk) vs. thickness (t) plots for the 37 test and seven reference materials were approximated linearly. In 54 of 57 linear regressions, the coefficients of determination (R2) were >0.96, and in 48 instances were >0.98. Fourteen Dk values from the current study and an earlier study were linearly correlated (R2 = 0.9846), with a slope close to unity (+1.056) and intercept close to zero (-0.292). Ten of the current values fell within 10% of their corresponding earlier values. Only three current Dk values fell outside of the ANSI Z80.20-1998 tolerance for Dk (+/-20%). Two of these Dk values met the product tolerance when an obvious outlying point was graphically identified and omitted from the linear resistance (t/Dk) vs. thickness (t) regression. CONCLUSION: Omission of a single outlying point from a linear resistance vs. thickness regression can help provide a more valid Dk value. The ANSI Z80.20-1998 tolerance of +/-20% on Dk and the measurement reproducibility of +/-10% were achieved for the overwhelming majority of rigid contact lens materials up to at least 160 Dk units. The corrected, calibrated Dk values for the 37 test materials, in ANSI units, ranged from 13.8 to 175.1, having an overall mean of 43.2, median of 31.9, and standard error of 6.57 (N = 37).

Calibration↗

PubMed2004

Cross institutional collaboration in assessment: a case on progress testing.

The practice of assessment is governed by an interesting paradox. On the one hand good assessment requires substantial resources which may exceed the capacity of a single institution and we have reason to doubt the quality of our in-house examinations. On the other hand, our parsimonity with regard to our resources makes us reluctant to pool efforts and share our test material. This paper reports on an initiative to share test material across different medical schools. Three medical schools in The Netherlands have successfully set up a partnership for a specific testing method: progress testing. At present, these three schools collaboratively produce high-quality test items. The jointly produced progress tests are administered concurrently by these three schools and one other school, which buys the test. The steps taken in establishing this partnership are described and results are presented to illustrate the unique sort of information that is obtained by cross-institutional assessment. In addition, plans to improve test content and procedure and to expand the partnership are outlined. Eventually, the collaboration may even extend to other test formats. This article is intended to give evidence of the feasibility and exciting potential of between school collaboration in test development and test administration. Our experiences have demonstrated that such collaboration has excellent potential to combine economic benefit with educational advantages, which exceed what is achievable by individual schools.

Cooperative Behavior↗

PubMedDate not supplied

[Mexican ceramic material for skin healing].

Sixty female Wistar rats were employed and divided into three experimental groups of 20 rats each. Groups were evaluated at 15, 30, and the last at 45 days after surgery. Each group was divided into four sets of five rats each. All rats were subjected to surgery; an incision of 2 x 2 cm was done on the back of each animal, removing tissue until reaching muscular fascia, where the material was applied. Nitro-furazone was employed as positive control. Test materials were AlPO added with 0.55% wt of Zn; 0.30% wt of Ca(OH)2, and AlPO added with 0.55% wt of Zn and 0.66% wt of Ca(OH)2. Finally, as negative control no material was used. The object of this work was in the first place obtension of test materials and to evaluate the healing skin process in rats using AlPO enriched with Zn and Ca(OH)2; as indicated previously. Obtained materials were characterized employing XRD. Histologic studies tested showed that best healing process of dermal tissue corresponded to rats treated with AlPO added with 0.55% wt of Zn and 0.30% wt of Ca(OH)2. Use of AlPO ceramics to repair skin has not been reported previously.

Animals↗

PubMed2004

Evaluation of modifications of the traditional patch test in assessing the chemical irritation potential of feminine hygiene products.

BACKGROUND/AIMS: The first main objective of the work presented in this paper was to investigate ways of optimizing the current arm patch test protocol by (1) increasing the sensitivity of the test in order to evaluate more effectively the products that are inherently non-irritating, and/or (2) reducing the costs of these types of studies by shortening the protocol. The second main objective was to use the results of these studies and the results of the parallel studies conducted using the behind-the-knee method to better understand the contribution of mechanical irritation to the skin effects produced by these types of products. In addition, we were interested in continuing the evaluation of sensory effects and their relationship to objective measures of irritation. METHODS: Test materials were prepared from three, currently marketed feminine protection pads. Wet and dry samples were applied to the upper arm using the standard 24-h patch test. Applications were repeated daily for 4 consecutive days. The test sites were scored for irritation prior to the first patch application, and 30-60 min after removal of each patch. Some test sites were treated by tape stripping the skin prior to the initial patch application. In addition, in one experiment, panelists were asked to keep a daily diary describing any sensory skin effects they noticed at each test site. RESULTS: All protocol variations ([intact skin/dry samples], [compromised skin/dry samples], [intact skin/wet samples], and [compromised skin/wet samples]) gave similar results for the products tested. When compared to the behind-the-knee test method, the standard upper arm patch test gave consistently lower levels of irritation when the test sites were scored shortly after patch removal, even though the sample application was longer (24 vs. 6 h) in the standard patch test. The higher level of irritation in the behind-the-knee method was likely due to mechanical irritation. The sensory skin effects did not appear to be related to a particular test product or a particular protocol variation. However, the mean irritation scores at those sites where a sensory effect was reported were higher than the mean irritation scores at those sites were no sensory effects were reported. CONCLUSIONS: All four protocol variations of the standard upper arm patch test can be used to assess the inherent chemical irritant properties of feminine protection products. For these products, which are inherently non-irritating, tape stripping and/or applying wet samples does not increase the sensitivity of the patch test method. Differences in irritation potential were apparent after one to three 24-h applications. Therefore, the standard patch test protocol can be shortened to three applications without compromising our ability to detect differences in the chemical irritation produced by the test materials. The patch test can be used to evaluate effectively the inherent chemical irritation potential of these types of products. However, this method is not suitable for testing the mechanical irritation due to friction that occurs during product use. There is no relationship between specific test conditions, i.e., compromised skin and/or testing wet samples and reports of perceived sensory reactions. However, there seems to be a clear relationship between sensory reactions and objective irritation scores.

Absorbent Pads↗

PubMed2006

Fit-for-purpose shellfish reference materials for internal and external quality control in the analysis of phycotoxins.

The need for reference materials for quality control of analysis of foodstuffs has been stressed frequently. This has been particularly true in the phycotoxins field, where there is a great shortage of both pure calibration standards and reference materials. Worldwide there are very few independent bodies that produce certified reference materials for phycotoxins, the main producers currently being the National Research Council Canada and the Japanese Food Research Laboratory. Limited availability of contaminated shellfish and algae, as well as the time and knowledge necessary for the production of adequate reference materials, continuously lead to limited editions of certified reference materials and even more limited production of in-house reference materials. The restricted availability of in-house quality control materials promotes the rapid use of the limited certified reference materials, which in turn hampers the production of the suite of materials required globally for complete protection of public health. This paper outlines the various options that analysts can pursue in the use of reference materials for internal and external quality control, with a view to optimising the efforts of both reference materials users and reference materials producers. For this purpose, the logical sequence is reviewed from the discovery of a new bioactive compound in shellfish, through initial method development up to regulation for food safety purposes including accepted reference methods. Subsequently, the requirements for and efforts typically spent in the production and characterisation of laboratory reference materials, certified reference materials and other test materials used in inter-laboratory studies or proficiency testing, in the area of marine biotoxins are evaluated. Particular emphasis is put on practical advice for the preparation of in-house reference materials. The intricate link between reference material characterisation and method performance is outlined to give guidance on the appropriate in-house method validation in the rapidly developing field of phycotoxins.

Animals↗

PubMed1987

Biomechanical aspects of playing surfaces.

The purpose of this paper is to discuss some biomechanical aspects of playing surfaces with special focus on (a) surface induced injuries, (b) methodologies used to assess surfaces and (c) findings from various sports. The paper concentrates primarily on questions related to load on the athlete's body. Data from epidemiological studies suggest strongly that the surface is an important factor in the aetiology of injuries. Injury frequencies are reported to be significantly different for different surfaces in several sports. The methodologies used to assess surfaces with respect to load or performance include material tests and tests using experimental subjects. There is only little correlation between the results of these two approaches. Material tests used in many standardized test procedures are not validated which suggests that one should exercise restraint in the interpretation of these results. Point elastic surfaces are widely studied while area elastic surfaces have received little attention to date. Questions of energy losses on sport surfaces have rarely been studied scientifically.

Athletic Injuries↗

PubMed1993

Evaluation of the viscoelastic properties of denture soft lining materials.

Denture soft lining materials are widely used in prosthetic dentistry. Their success has been attributed to their softness and resilience, properties described by their viscoelasticity. Though these properties have been extensively investigated in laboratory studies, clinical studies have been limited. The viscoelastic properties of the temporary soft lining material Coe Soft and the permanent soft lining materials Palasiv 62 and Molloplast-B have been studied using a force/distance probe whereby penetration was measured against time under constant stress. Derived values of an initial and time-dependent compliance has allowed a quantitative in vivo and in vitro assessment of freshly prepared samples of each test material and comparison between materials. The baseline behaviour of each test material in response to the test regimen was similar for both clinical and laboratory specimens. Three types of behaviour could be identified: (i) constant strain in which penetration was clearly less than specimen thickness--elastic behaviour (Molloplast-B); (ii) constant strain in which the penetration was equal or nearly equal to specimen thickness--apparent elastic behaviour (Coe Soft); (iii) strain which increased with time of load application--viscoelastic behaviour (Palasiv 62). The mean and range of baseline clinical thickness for Coe Soft was approximately half that seen for the permanent soft lining materials. There was a much smaller range in the baseline compliance of all materials than might have been anticipated from a knowledge of their relative softness.

Acrylic Resins↗

PubMed2002

An evaluation of accelerated Portland cement as a restorative material.

Biocompatibility of two variants of accelerated Portland cement (APC) were investigated in vitro by observing the cytomorphology of SaOS-2 osteosarcoma cells in the presence of test materials and the effect of these materials on the expression of markers of bone remodelling. Glass ionomer cement (GIC), mineral trioxide aggregate (MTA) and unmodified Portland cement (RC) were used for comparison. A direct contact assay was undertaken in four samples of each test material, collected at 12, 24, 48 and 72 h. Cell morphology was observed using scanning electron microscopy (SEM) and scored. Culture media were collected for cytokine quantification using enzyme-linked immunosorbent assay (ELISA). On SEM evaluation, healthy SaOS-2 cells were found adhering onto the surfaces of APC variant, RC and MTA. In contrast, rounded and dying cells were observed on GIC. Using ELISA, levels of interleukin (IL)-1beta, IL-6, IL-18 and OC were significantly higher in APC variants compared with controls and GIC (p<0.01), but these levels of cytokines were not statistically significant compared with MTA. The results of this study provide evidence that both APC variants are non-toxic and may have potential to promote bone healing. Further development of APC is indicated to produce a viable dental restorative material and possibly a material for orthopaedic

Biocompatible Materials↗