Isoquercetin upregulates antioxidant genes, suppresses inflammatory cytokines and regulates AMPK pathway in streptozotocin-induced diabetic rats.

Lifestyle and genetic factors contribute to the initiation of oxidative stress and inflammation in diabetes mellitus (DM). Oxidative stress and lipid peroxidation worked in an orchestrated manner and reported to be strongly associated with the formation of the hyperlipidemic condition in DM patients. Isoquercetin, a bioactive constituent isolated from guava leaves has attracted considerable attention because of its antidiabetic activity. The antidiabetic activity of guava leaves may be due to the presence of isoquercetin at a significant level. However, how isoquercetin regulates different pathways in DM is insufficiently studied. We have selected versatile regulators of oxidative stress and inflammatory pathways to fully analyze if isoquercetin effectively modulated the genes of these pathways. At the end of our experimental duration, rats were dissected and analyzed for the oxidative stress, lipid peroxidation, inflammatory and lipid markers. The nuclear factor erythroid 2-related factor 2 (Nrf2) pathway is believed to be the key regulator of expression of various antioxidant enzyme genes and it is directly or indirectly related to nuclear factor Kappa- B (NF-kB) and AMP-activated protein kinase (AMPK) pathways. Therefore, we tend to study the effects of STZ on Nrf2, NF-kB and AMPK pathway and how the isoquercetin treatment performs at a molecular level to overcome the burden of DM. The results of our study provided convincing evidence of significant pharmacological properties of isoquercetin in context of its ability to inhibit the oxidative stress elicited by the STZ through generation of the free radicals and regulation of the expression of Nrf2 pathway-associated proteins and genes and it also reduced the burden of hyperlipidemia and inflammation. By taking the above results into consideration isoquercetin can be studied further to elucidate its antidiabetic effects at various levels.

Novel effects of sarcopenic osteoarthritis on metabolic syndrome, insulin resistance, osteoporosis, and bone fracture: the national survey.

UNLABELLED: This study compared the effects sarcopenic osteoarthritis on metabolic syndrome, insulin resistance, osteoporosis, and bone fracture. By using national survey data, we suggest that the relationship between sarcopenia and metabolic syndrome or insulin resistance is potentiated by the severity of osteoarthritis and is independent of body weight. INTRODUCTION: Sarcopenia and osteoarthritis are known risk factors for metabolic syndrome. However, their combined effects on metabolic syndrome, insulin resistance and osteoporosis remain uncertain. METHODS: We used data from the fifth Korean National Health and Nutrition Examination Survey using a total of 3158 adults (age >50 years). Sarcopenia was defined as a skeletal muscle index score (appendicular skeletal muscle mass/body weight) within the fifth percentile of sex-matched younger reference participants. Radiographic knee osteoarthritis was defined as a Kellgren-Lawrence (K-L) grade of 2 or greater. Metabolic syndrome was diagnosed using the National Cholesterol Education Program criteria. Insulin resistance was evaluated using the homeostasis model assessment-estimated insulin resistance index (HOMA-IR). Osteoporosis was defined using the World Health Organization T-score criteria. RESULTS: In multivariable logistic regression analysis, the sarcopenic osteoarthritis group had a higher odds ratio (OR) for metabolic syndrome (OR = 11.00, 95 % confidential interval (CI) = 2.12-56.99, p = 0.013) than the non-sarcopenic osteoarthritis (OR = 1.02, 95 % CI = 0.65-1.62, p = 0.972) and sarcopenic non-osteoarthritis groups (OR = 7.15, 95 % CI = 1.57-32.53, p = 0.027). Similarly, sarcopenic osteoarthritis had a greater OR of highest HOMA-IR quartiles (OR = 8.19, 95 % CI = 2.03-33.05, p = 0.003) than the other groups. Overall, the association between the K-L grade and body mass index was significant; however, this significance was lower in individuals with sarcopenia and was lost in those with sarcopenic osteoarthritis. Additionally, osteoporosis and bone fracture were not associated to sarcopenic osteoarthritis (p > 0.05). CONCLUSIONS: These results suggest that the relationship between sarcopenia and metabolic syndrome or insulin resistance is potentiated by the severity of osteoarthritis and is independent of body weight.

Implications of obesity for drug therapy: limitations and challenges.

Obesity has become a worldwide challenge with significant health and socioeconomic implications. One of the major implications is its impact on drug therapy. In order to gain a better understanding of this impact, we surveyed the regulatory guidances, the newly approved molecular entity drug products, and drug product labels in the Physician's Desk Reference. This review summarizes the findings of the survey along with the existing knowledge on pharmacokinetic and pharmacodynamic changes associated with obesity.

Doxorubicin-induced platelet cytotoxicity: a new contributory factor for doxorubicin-mediated thrombocytopenia.

BACKGROUND: Doxorubicin (DOX) is a widely used anticancer drug for solid tumors and hematologic malignancy, but its active use is hampered by serious adverse effects, including thrombocytopenia. Although bone marrow toxicity of DOX has been suggested to be the sole mechanism underlying the reduced platelet counts, the direct effects of DOX on platelets have never been examined. OBJECTIVE: Here, we investigated the DOX-induced platelet cytotoxicity and its underlying mechanism in an effort to elucidate the contribution of platelet cytotoxicity to DOX-induced thrombocytopenia. RESULTS: In freshly isolated human platelets, DOX induced platelet cytotoxicity in a time-dependent and concentration-dependent manner. Reactive oxygen species (ROS) generation, decreased glutathione levels and subsequent protein thiol depletion were shown to underlie the DOX-induced platelet cytotoxicity. Conspicuously, DOX-treated platelets displayed apoptotic features such as caspase-3 activation, reduced mitochondrial transmembrane potential, and phosphatidylserine exposure. Decreased glutathiolation of procaspase-3 was shown to be a link between protein thiol depletion and caspase-3 activation. It is of note that DOX-mediated platelet cytotoxicity was significantly enhanced by shear stress, a common complicating factor in cancer patients. These in vitro results were further confirmed by an in vivo animal model, where administration of DOX induced a platelet count decrease, ROS generation, caspase-3 activation, protein thiol depletion, and damaged platelet integrity. CONCLUSION: We demonstrated that DOX can directly induce platelet cytotoxicity through ROS generation, decreased glutathione levels, and protein thiol depletion. We believe that this study provides important evidence for the role of DOX-induced platelet cytotoxicity in the development of thrombocytopenia in DOX-treated patients.

Detection of QTL for yield-related traits using recombinant inbred lines derived from exotic and elite US Western Shipping melon germplasm.

The inheritance of yield-related traits in melon (Cucumis melo L.; 2n = 2x = 24) is poorly understood, and the mapping of quantitative trait loci (QTL) for such traits has not been reported. Therefore, a set of 81 recombinant inbred lines (RIL) was developed from a cross between the monoecious, highly branched line USDA 846-1 and a standard vining, andromonoecious cultivar, 'Top Mark'. The RIL, parental lines, and three control cultivars ('Esteem', 'Sol Dorado', and 'Hales Best Jumbo') were grown at Hancock, WI and El Centro, CA in 2002, and evaluated for primary branch number (PB), fruit number per plant (FN), fruit weight per plant (FW), average weight per fruit (AWF), and percentage of mature fruit per plot (PMF). A 190-point genetic map was constructed using 114 RAPD, 43 SSR, 32 AFLP markers, and one phenotypic trait. Fifteen linkage groups spanned 1,116 cM with a mean marker interval of 5.9 cM. A total of 37 QTL were detected in both locations (PB = 6, FN = 9, FW = 12, AWF = 5, and PMF = 5). QTL analyses revealed four location-independent factors for PB (pb1.1, pb1.2, pb2.3, and pb10.5), five for FN (fn1.1, fn1.2, fn1.3, fn2.4, and fn8.8), four for FW (fw5.8, fw6.10, fw8.11, and fw8.12), two for AWF (awf1.3 and awf8.5), and one for PMF (pmf10.4). The significant (P

Environmental degradation of glass-ionomer cements: a depth-sensing microindentation study.

This study investigated the effects of various environmental conditions on the hardness and elastic modulus of restorative glass-ionomer cements (GICs). Two resin-modified GICs (RMGICs) (Fuji II LC [FL]; Photac-Fil Quick [PQ]) and three highly viscous GICs (HVGICs) (Fuji IX Fast [FN]; KetacMolar [KM]; KetacMolar Quick [KQ]) were evaluated in this study. Specimens were fabricated according to the manufacturers' instructions and stored under a variety of conditions (n = 7): 100% humidity, distilled water, pH 5 demineralization solution, and pH 7 remineralization solution. The hardness and elastic modulus were measured using a depth-sensing microindentation test after 4 weeks. The results were analyzed using the independent samples T-test and ANOVA/Scheffe's post hoc test (p < 0.05). HVGICs showed significantly higher hardness and elastic modulus than RMGICs under all storage conditions. Storage in distilled water significantly increased the hardness and elastic modulus of FN, but decreased that of PQ. All HVGICs and RMGICs stored in remineralization solution had hardness values and elastic moduli comparable to those stored in water. Compared to remineralization solution, demineralization solution had no significant effects on the modified GICs with the exception of KQ. The results suggest that the mechanical properties of glass-ionomer restoratives are material-type and storage condition dependent. Therefore, the clinical selection of a glass-ionomer material should be based on the oral environment to which it will be subjected.

Characterization of a silver-incorporated calcium phosphate film by RBS and its antimicrobial effects.

A thin calcium phosphate film was synthesized on both commercially pure Ti and Si wafers by electron beam evaporation of hydroxyapatite as an evaporant with simultaneous Ar ion beam bombardments. Silver was introduced into an ion-beam-assisted deposition of a calcium phosphate thin film for antimicrobial effect. The amount of incorporated silver ions was controlled by immersing calcium-phosphate-coated samples in different AgNO(3) concentrations, and Rutherford backscattering spectrometry (RBS) was employed to measure the amounts of substituted silver. The higher concentration of silver in the calcium phosphate film was more effective in reducing the bacteria of Escherichia coli ATCC 8739 and Streptococcus mutans OMZ 65 on contact with respect to controls.

Biological responses in osteoblast-like cell line according to thin layer hydroxyapatite coatings on anodized titanium.

Several features of the implant surface, such as roughness, topography and composition play a relevant role in implant integration with bone. This study was conducted in order to determine the effects of various thin layer hydroxyapatite (HA) coatings on anodized Ti surfaces on the biological responses of a human osteoblast-like cell line (MG63). MG63 cells were cultured on 100 nm HA (100 nm HA coating on anodized surface), 500-700 nm HA (500-700 nm HA coating on anodized surface), 1 mum HA (1 mum HA coating on anodized surface) and anodize (non-HA coating on anodized surface) Ti. The morphology of these cells was assessed by scanning electron microscopy (SEM). The cDNAs prepared from the total RNAs of the MG63 were hybridized into a human cDNA microarray (1152 elements). The appearances of the surfaces observed by SEM were different on each of the four dental substrate types. MG63 cells cultured on 100 nm HA, 1 mum HA and anodize exhibited cell-matrix interactions. It was 500-700 nm HA surface showing cell-cell interaction. In the expression of genes involved in osseointegration, several genes, including bone morphogenetic protein 2, latent transforming growth factor beta binding protein 1, catenin (cadherin-associated protein), integrin, PDGFRB and GDF-1 growth differentiation factor 1 were up-regulated on the different surfaces. Several genes, including fibroblast growth factor receptor 3, fibroblast growth factor 12 and CD4 were down-regulated on the different surfaces. The attachment and expression of key osteogenic regulatory genes were enhanced by the surface morphology of the dental materials used.

Molecular phylogeny of Cucumis species as revealed by consensus chloroplast SSR marker length and sequence variation.

To investigate phylogenetic relationships in the genus Cucumis, 9 consensus chloroplast simple sequence repeat (ccSSR) primer pairs (ccSSR3, 9, 11, 13, 14, 17, 20, 21, and 23) were employed for DNA fragment length variation and 5 amplified fragments, ccSSR4, 12, 13, 19, and 20, were sequenced using total DNA from 13 accessions representing 7 African Cucumis species (x = 12), 3 Cucumis melo L. (x = 12) accessions, 2 Cucumis sativus L. (x = 7) accessions, and 1 Cucumis hystrix Chakr. (x = 12) accession. A Citrullus lanatus (Thunb.) Matsum. & Nakai (x = 11) accession was used as an outgroup. While fragment length analysis revealed the existence of 3 major species clusters (i.e., a group of African Cucumis species, a group composed of C. melo accessions, and a group containing C. sativus and C. hystrix species), sequence variation analysis identified 2 major species clusters (i.e., a group of African Cucumis species and a group composed of C. melo, C. sativus, and C. hystrix species). Comparative analysis using nuclear DNA (previous studies) and cpDNA sequence substitution data resulted in the placement of C. melo and C. sativus in different cluster groupings. Thus, both nuclear and cytoplasmic DNA should be employed and compared when a putative progenitor or specimens of an ancestral Cucumis species lineage is investigated. In addition, C. ficifolius (2x) and C. aculeatus (4x) of the African Cucumis species clustered together in this study. This result does not agree with reported isozyme analyses, but does agree with previously characterized chromosome homologies between these 2 species. Although African Cucumis species and C. hystrix do not share a close relationship, genetic affinities between C. sativus and C. hystrix are considerable. Combined evidence from previously published studies and data presented herein lend support to the hypothesis that C. hystrix is either a progenitor species of C. sativus or that they at least share a common ancestral lineage.

Effects of surface finish on indentation modulus and hardness of dental composite restoratives.

OBJECTIVES: The depth-sensing micro-indentation testing was recently introduced for the characterization of dental composites. One of the critical issues raised was the possible influence of surface finish on material properties. The aim of this study was to investigate the effects of surface finish on the indentation modulus and micro-hardness of resin-based dental composite materials. METHODS: The materials used included minifill (Z100, 3M ESPE), microfill (A110, 3M ESPE) and poly-acid modified (F2000, 3M ESPE) composites. The specimens were polished successively using SiC grinding papers of different grit size and diamond suspensions to achieve varying surface roughness. The arithmetic mean of the roughness (R(a)) was measured using profilometry. In the depth-sensing micro-indentation test, specimens (n=7) were indented to 10N with Vickers indenter and the load-displacement (P-h) data was obtained using a universal testing system. The indentation modulus (E(in)) and hardness (H) were then computed using the developed analytical solutions. Data was analyzed using ANOVA/post-hoc Scheffe's test at significance level 0.05. RESULTS: The polished specimens had surface roughness ranging from 0.02 to 0.81 microm. The roughness of F2000 was significantly higher than A110 and Z100. The E(in) and H for Z100 ranged from 14.02 to 14.83GPa and 1.18 to 1.27 GPa, respectively. E(in) for F2000 and A110 ranged from 12.25 to 13.82 GPa and 5.26 to 5.52 GPa and hardness ranged from 0.89 to 0.98 GPa and 0.52 to 0.55 GPa, respectively. SIGNIFICANCE: The indentation modulus and hardness of dental composite restoratives were independent of the surface finish provided indenter penetration is sufficiently deep (h(max)/R(a)>30).

Construction of two BAC libraries from cucumber (Cucumis sativus L.) and identification of clones linked to yield component quantitative trait loci.

Two bacterial artificial chromosome (BAC) libraries were constructed from an inbred line derived from a cultivar of cucumber (Cucumis sativus L.). Intact nuclei were isolated and embedded in agarose plugs, and high-molecular-weight DNA was subsequently partially digested with BamHI or EcoRI. Ligation of double size-selected DNA fragments with the pECBAC1 vector yielded two libraries containing 23,040 BamHI and 18,432 EcoRI clones. The average BamHI and EcoRI insert sizes were estimated to be 107.0 kb and 100.8 kb, respectively, and BAC clones lacking inserts were 1.3% and 14.5% in the BamHI and EcoRI libraries, respectively. The two libraries together represent approximately 10.8 haploid cucumber genomes. Hybridization with a C(0)t-1 DNA probe revealed that approximately 36% of BAC clones likely carried repetitive sequence-enriched DNA. The frequencies of BAC clones that carry chloroplast or mitochondrial DNA range from 0.20% to 0.47%. Four sequence-characterized amplified region (SCAR), four simple sequence repeat, and an randomly amplified polymorphic DNA marker linked with yield component quantitative trait loci were used either as probes to hybridize high-density colony filters prepared from both libraries or as primers to screen an ordered array of pooled BAC DNA prepared from the BamHI library. Positive BAC clones were identified in predicted numbers, as screening by polymerase chain reaction amplification effectively overcame the problems associated with an overabundance of positives from hybridization with two SCAR markers. The BAC clones identified herein that are linked to the de (determinate habit) and F (gynoecy) locus will be useful for positional cloning of these economically important genes. These BAC libraries will also facilitate physical mapping of the cucumber genome and comparative genome analyses with other plant species.

Influence of dietary solvents on strength of nanofill and ormocer composites.

The objective of this study was to determine the influence of dietary solvents on the shear punch strength of nanofill (Filtek Supreme [FS], 3M-ESPE) and ormocer (Admira [AM], Voco) composites. The strength of these materials was also compared to a minifill composite (Z250 [ZT], 3M-ESPE), a compomer (F2000 [FT], 3M-ESPE) and a highly viscous glass ionomer cement (Ketac Molar Quick [KM], 3M-ESPE). Thirty-two specimens (8.7 mm diameter and 1-mm thick) of each material were made, randomly divided into four groups of eight and conditioned for one week as follows-Group 1 (control): distilled water at 37 degrees C; Group 2: 0.02M citric acid at 37 degrees C; Group 3: 50% ethanol-water solution at 37 degrees C and Group 4: heptane at 37 degrees C. After conditioning, the specimens were restrained with a torque of 2.5 Nm and subjected to shear punch strength testing using a 2-mm diameter punch at a crosshead speed of 0.5 mm/minute. The shear punch strength of the specimens was computed and data subjected to ANOVA/Scheffe's tests at significance level 0.05. With the exception of AM, the strength of all materials was not significantly influenced by dietary solvents. For AM, conditioning in heptane resulted in significantly higher shear strength values. The strength of the nanofill and ormocer composites was lower than the minifill composite but higher than the compomer and highly viscous glass ionomer cement investigated.

Elastic modulus of resin-based dental restorative materials: a microindentation approach.

This research aimed to determine the elastic modulus of resin-based dental composite restoratives using the microindentation test method. Results were then compared with those obtained with the ISO three-point bending test method. Five materials from the same manufacturer (3M ESPE) were selected for the study. They included microfill (A110), minifill (Z100 and Filtek Z250), poly-acid modified (F2000), and flowable (Filtek Flowable [FF]) composites. The indentation moduli of the composites were determined using a custom-designed microindentation test set up after conditioning in water at 37 degrees C for 1 week and 1 month. The indentation test was carried out at peak load of 10 N and Oliver & Pharr's method was used to determine the maximum projected contact area. Data was analyzed using ANOVA/post-hoc Scheffe's test at significance level 0.05 and Pearson's correlation at significance level 0.01. The mean indentation modulus ranged from 5.80 to 15.64 GPa and 5.71 to 15.35 GPa at 1 week and 1 month, respectively. At both time periods, the indentation modulus of Z100 was significantly higher than all other materials. F2000 was significantly higher than Z250, which was significantly stiffer than A110 and FF. The rankings were in good agreement with the ISO flexural test. A significant, positive, and strong correlation (r = 0.93 and 0.94 at 1 week and 1 month, respectively) in modulus between ISO three-point bending and microindentation test methods was observed. In view of the small specimen size and good reproducibility, the microindentation reflects a potential test method for determining the elastic properties of dental composite restoratives.

Effects of aging on mechanical properties of composite restoratives: a depth-sensing microindentation approach.

This study investigated the effects of aging on the hardness and modulus of two composites (Tetric Ceram [TC], Vivadent; Esthet X [EX], Dentsply), a conventional (Compoglass [CG], Vivadent) and a posterior compomer (Dyract Posterior [DP], Dentsply) using a depth-sensing microindentation approach. Seven specimens (3-mm wide x 3-mm long x 2-mm deep) of each material were made and conditioned in distilled water at 37 degrees C. Hardness and modulus of the materials were determined at seven and 30 days using depth-sensing microindentation testing with the Instron MicroTester. Hardness was determined by dividing the peak load over the maximum projected contact area while effective modulus was calculated by analysis of the loading/unloading P-h curves and the analytical model according to Oliver and Pharr (1992). Results were analyzed using one-way ANOVA/Scheffe's post-hoc test and Independent Samples t-test at significance level 0.05. Mean Vickers Hardness (HV) ranged from 46.60 to 58.67 and 44.44 to 59.41 at seven and 30 days, respectively. Mean indentation modulus ranged from 9.57 to 9.95 and 9.19 to 10.03 for the same time periods. At both time periods, EX was significantly harder than all the other materials and HV values for TC were significantly greater than CG. No significant difference in hardness and modulus was observed between seven and 30 days for all materials with the exception of CG. For the latter, a significant decrease in mechanical properties was detected over time.

Flexural strength of dental composite restoratives: comparison of biaxial and three-point bending test.

This study compared two test methods used to evaluate the flexural strength of resin-based dental composites. The two test methods evaluated were the three-point bending test4 and the biaxial flexural test. Materials used in this investigation were from the same manufacturer (3M ESPE) and included microfill (A110), minifill (Z100 and Filtek Z250), polyacid modified (F2000), and flowable [Filtek Flowable (FF)] composites. Flexural strength was determined with the use of both test methods after 1 week of conditioning in water at 37 degrees C. Data were analyzed with the use of an ANOVA/Scheffe test and an independent-samples t test at significance level 0.05. Mean flexural strength (n = 7) ranged from 66.61 to 147.21 and 67.27 to 182.81 MPa for three-point bending and ball-on-three-ball biaxial test methods, respectively. In both test methods, Z100 was significantly stronger than all other composites evaluated. In the three-point bending test, flexural strength of Z250 was significantly higher than A110, F2000 and FF, and FF was significantly stronger than A110 and F2000. The biaxial test method arrived at the same conclusions except that there was no significant difference between Z250 and FF. Pearson's correlation revealed a significantly (p < 0.01) positive and good correlation (R2 = 0.72) in flexural strength between the two test methods. Although the biaxial test has the advantage of utilizing small specimens, the low reproducibility of this test method does not support the proposition that it is a more reliable test method when compared to the ISO three-point bending test.

Wear behavior of new composite restoratives.

This study investigated the wear resistance of recently introduced nanofill (Filtek Supreme [FS], 3M-ESPE) and ormocer (Admira [AM], Voco) composites and compared their wear characteristics to microfill (Filtek A110 [AO], 3M-ESPE]), minifill (Esthet X [EX], Dentsply; Filtek Z250 [ZT], 3M-ESPE) and polyacid-modified (Dyract AP [DY], Dentsply) composites. Six specimens were made for each material. The specimens were conditioned for one week in distilled water at 37 degrees C and subjected to wear testing at 20 MPa contact stress against SS304 counter-bodies using reciprocal compression-sliding wear instrumentation. Distilled water was used as lubricant. Wear depth (microm) was measured using profilometry every 5,000 cycles up to 20,000 cycles. The results were analyzed using ANOVA/Scheffe's test (p<0.05). Wear of the materials was cycle and fatigue dependent. Although no significance in wear was observed between materials after 5,000 cycles of wear testing, significant differences were observed at 10,000 cycles and greater. After 20,000 cycles of wear testing, ranking was as follows: ZT > DY >AM > AO > FS > EX. Wear ranged from 39.90 microm for EX to 113.32 microm for ZT. The wear resistance of ZT and DY was significantly lower than AO, FS and EX In addition, ZT experienced significantly more wear than AM. Under the conditions of this in-vitro study, the wear resistance of nanofill and ormocer composites was comparable or superior to polyacid-modified, microfill and minifill composites.

Fracture resistance of compomer and composite restoratives.

This study evaluated and compared the fracture toughness of compomers and composites. Three compomer (Compoglass F [CG], Vivadent; F2000 [FT], 3M-ESPE; Dyract Posterior [DP], Dentsply) and three composite (Tetric Ceram [TC], Vivadent; Z250 [ZT], 3M-ESPE; Esthet X [EX], Dentsply) restoratives were selected for the study. Single-edged notched specimens (25 x 2 x 2 mm) were fabricated according to manufacturers' instructions and conditioned in distilled water at 37 degrees C for one week prior to testing. Seven specimens were made for each material. The specimens were loaded to failure using an Instron microtester with a crosshead speed of 0.5 mm/minute. Data were subjected to ANOVA/Scheffe's test and Independent Samples T-test at significance level 0.05. The mean fracture toughness (K(IC)) ranged from 0.97 to 1.23 MPam 1/2 for compomers and 1.75 to 1.92 MPam 1/2 for composites. The fracture toughness of compomers was significantly lower than their composite counterparts. No significant difference in K(IC) values was observed among the different composites. When the compomers were compared, FT had significantly higher fracture toughness than DP and CG. In view of their poorer resistance to crack propagation, compomers are not recommended for use in stress-bearing areas.

Influence of the polymerization process on composite resistance to chemical degradation by food-simulating liquids.

This study determined the influence of curing lights and modes on composite resistance to chemical degradation by various food-simulating liquids. Two different types of curing light (Halogen [H]-Elipar Trilight, 3M-ESPE; LED [L]-Freelight, 3M-ESPE) and two curing modes (standard [S]; exponential [E) were evaluated in the study. Forty-five composite (Z100 [3M-ESPE]) specimens were made for each light-curing mode combination (HS, HE, LS and LE). The specimens were randomly divided into five groups of nine and exposed to the following food-simulating liquids (FSL) for one week at 37 degrees C: distilled water, 50% aqueous ethanol solution, heptane and citric acid. Specimens stored in air were used as control. After the one week conditioning period, hardness testing was conducted with a digital microhardness tester (load = 500 gf; dwell time = 15 seconds). Mean hardness (HK)/hardness deterioration (deltaHK) were subsequently computed and data was subjected to analysis using ANOVA/Scheffe's test (p < 0.05). The resistance of composite to chemical degradation by FSL was light/curing mode dependent. Significant differences in HK and deltaHK were observed among the four curing techniques after conditioning in some FSL and air. After conditioning in water and citric acid, specimens polymerized with HE underwent significantly more softening compared to specimens polymerized with HS, LS and LE.

Effect of food-simulating liquids on the shear punch strength of composite and polyacid-modified composite restoratives.

This study evaluated the effects of food-simulating liquids on the shear punch strength of two composites (Tetric Ceram [TC], Vivadent; Esthet X [EX], Dentsply), a conventional (Compoglass [CG], Vivadent) and a posterior polyacid-modified (Dyract Posterior [DP], Dentsply) composite. Thirty-two specimens (10-mm in diameter and 1.6-mm thick) of each material were made, randomly divided into four groups of eight and conditioned for one week as follows--Group 1 (control): air at 37 degrees C; Group 2: distilled water at 37 degrees C; Group 3: 75% ethanol-water solution at 37 degrees C and Group 4: heptane at 37 degrees C. After conditioning, the specimens were restrained within the test apparatus and subjected to shear punch strength testing using a 3.2 mm diameter punch at a crosshead speed of 0.5 mm/minute. The shear punch strength of the specimens was computed and the data was subjected to ANOVA/Scheffe's tests at significance level 0.05. The effect of food-simulating liquids on shear strength was found to be material dependent. All materials with the exception of EX were significantly weakened by ethanol solution. For DP, a significant increase in strength was observed after conditioning in water. EX was significantly stronger than TC and DY after conditioning in air, water and ethanol solution. The shear punch strength of EX and CG was significantly higher than DY after conditioning in heptane.