Contraction Stress Research Articles

Effect of fiber incorporation on the contraction stress of composite materials.

This study aimed to assess the effects of fiber incorporation on the contraction stress (CS), time to gelation (TG), and temperature rise (TR) features of two experimental resin-based composites (RBCs) in comparison to those of bulk-fill RBCs and conventional RBCs in simulated, clinically relevant cavities. CS over 300s, TG and TR were assessed by a stress-strain analyzer (SSA T80) in two cavity configurations (2 × 4 × 4mm3/4 × 4 × 4mm3/configuration value [Formula: see text] and [Formula: see text]) for two experimental RBCs, eight bulk-fill RBCs (EverX Posterior, Filtek Bulk Fill, SDR, SonicFill, Tetric EvoCeram Bulk Fill, Venus Bulk Fill, X-tra base, and X-tra Fill) and one RBC (Filtek Supreme XTE) by light curing (1200mW/cm2) (n = 10). The experimental materials used were based on EverX Posterior with modifications made to the fiber and filler content. Statistical analyses were performed via ANOVA; multiple pair-wise comparisons were performed via Tukey's test, and homogeneous subsets were identified ("multcomp" package, R). CS values ranged from 1.00 to 4.07MPa (2 × 4 × 4mm3) and from 0.97 to 2.49MPa (4 × 4 × 4mm3); TG values ranged from 1.31 to 4.05s (2 × 4 × 4mm3) and from 1.39 to 3.84s (4 × 4 × 4mm3). SDR values showed lowest stress values in both cavity configurations. The experimental composite with fibers presented significantly higher stress values than did the experimental composite without fibers. Bulk-fill RBCs showed lower levels of stress than did conventional RBCs. The incorporation of fibers had no positive impact on the CS and TG. Appropriate material selection may be essential to clinical success because certain RBCs exhibit higher CS, TG, and TR values.

Dental Resin Cements-The Influence of Water Sorption on Contraction Stress Changes and Hydroscopic Expansion.

Resin matrix dental materials undergo contraction and expansion changes due to polymerization and water absorption. Both phenomena deform resin-dentin bonding and influence the stress state in restored tooth structure in two opposite directions. The study tested three composite resin cements (Cement-It, NX3, Variolink Esthetic DC), three adhesive resin cements (Estecem, Multilink Automix, Panavia 2.0), and seven self-adhesive resin cements (Breeze, Calibra Universal, MaxCem Elite Chroma, Panavia SA Cement Plus, RelyX U200, SmartCem 2, and SpeedCEM Plus). The stress generated at the restoration-tooth interface during water immersion was evaluated. The shrinkage stress was measured immediately after curing and after 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Water sorption and solubility were also studied. All tested materials during polymerization generated shrinkage stress ranging from 4.8 MPa up to 15.1 MPa. The decrease in shrinkage strain (not less than 57%) was observed after water storage (56 days). Self-adhesive cements, i.e., MaxCem Elite Chroma, SpeedCem Plus, Panavia SA Plus, and Breeze exhibited high values of water expansion stress (from 0 up to almost 7 MPa). Among other tested materials only composite resin cement Cement It and adhesive resin cement Panavia 2.0 showed water expansion stress (1.6 and 4.8, respectively). The changes in stress value (decrease in contraction stress or built up of hydroscopic expansion) in time were material-dependent.

A numerical study on the effect of trapezium stenosis shape on the axisymmetric flow field around stenosis

Numerical simulations on the pulsatile flow in stenosed tubes were conducted to investigate the effect of trapezium shape of stenosis on the flow field around stenoses. Four trapezium shapes of stenoses were considered by varying contraction, plateau, and expansion parts of stenoses for different stenosis area reduction ratios. The Galerkin finite element method based on the P2P1 mixed element was employed to solve the axisymmetric incompressible Navier-Stokes equations and the continuity equation. The proposed numerical method was validated by solving a benchmark problem of stenotic flow. It was found that the average pressure profile along the centerline was more affected by the contraction shape than the expansion shape. It was also revealed that the average wall shear stress of mild contraction was greater than that of sudden contraction around the stenotic region. Furthermore, the pressure drop across the stenosis was found to be associated with the form drag experienced by the stenosis.

Can Fetal Heart Rate Responses to Maternal Exercise Be Used for Antepartum Surveillance?

The contraction stress test (CST) is currently the only modality used to test for placental insufficiency. It is rarely used due to possible complications. We propose a new test to assess placental reserves by measuring fetal heart rate (FHR) fetal responses to maternal exercise (FRME). A cohort of 640 term patients underwent FRME for accepted clinical indications. There was a total of 1680 tests, performed using a motorized treadmill in a moderate exercise regimen. Monitoring was provided by using standard Philips equipment (Avalon CTS and FM40). FRME was interpreted as negative (absence of decelerations, possible presence of accelerations), positive (presence of late decelerations or sustained bradycardia), or inconclusive. The results demonstrated 1506 tests were negative, 58 were positive, and 312 were inconclusive. If the test was negative, only 2% of the fetuses experienced adverse outcomes, versus 14%, when the test was positive. Positive tests were associated with 29% of category III FHR tracing, 11.6% of 5-minute Apgar score of less than 7, 9.8% admissions to the intensive care nursery, 2.2% of growth restrictions, and 1.2% of fetal or early neonatal demises. FRME if positive is associated with adverse perinatal outcome and could be included into the armamentarium of fetal testing.

Formation of Slivers in the Extended Cross‐Section Platforms of Ni‐Based Single Crystal Superalloy

A model with rejoined platforms is designed to study the casting defects in the platforms of Ni‐based single crystal superalloy. The results of this study indicate the formation of sliver defects in different regions of the platforms. In the platforms, the dendrite deviation started at the section extension region and the misoriented dendrites could continue to grow into the platform to form sliver defects through the competitive growth with the adjacent dendrites. Furthermore, sliver defects formed as a result of the deformation of secondary dendrites induced by the thermal contraction stress based on the polar diagram analysis and the finite element simulation results. Finally, three different factors contributing to the formation of sliver defects in the extended cross‐section platforms are speculated as follows: the orientation of the deformed dendrites, the local thermal field condition, and the sufficient growth space.

Efficient estimation of personalized biventricular mechanical function employing gradient-based optimization.

Individually personalized computational models of heart mechanics can be used to estimate important physiological and clinically‐relevant quantities that are difficult, if not impossible, to directly measure in the beating heart. Here, we present a novel and efficient framework for creating patient‐specific biventricular models using a gradient‐based data assimilation method for evaluating regional myocardial contractility and estimating myofiber stress. These simulations can be performed on a regular laptop in less than 2 h and produce excellent fit between measured and simulated volume and strain data through the entire cardiac cycle. By applying the framework using data obtained from 3 healthy human biventricles, we extracted clinically important quantities as well as explored the role of fiber angles on heart function. Our results show that steep fiber angles at the endocardium and epicardium are required to produce simulated motion compatible with measured strain and volume data. We also find that the contraction and subsequent systolic stresses in the right ventricle are significantly lower than that in the left ventricle. Variability of the estimated quantities with respect to both patient data and modeling choices are also found to be low. Because of its high efficiency, this framework may be applicable to modeling of patient specific cardiac mechanics for diagnostic purposes.

Management of fetal growth restriction using the contraction stress test: a case-control study

Purpose: Fetal growth restriction (FGR) is a concerning health issue. However, studies on FGR management are limited due to its rarity. We aimed to evaluate the efficacy of the contraction stress test (CST) for FGR management.Materials and methods: A case-control retrospective study design. Our institute innovated CST in FGR management in 2017. We included women in their 33rd–40th week of pregnancy with a diagnosis of FGR and retrospectively divided them into groups: the CST group (FGR management with CST) and no CST group (FGR management without CST) before and after CST development. Neonatal outcome, pH, and pO2 of umbilical artery (UA) were compared between the two groups.Results: No significant differences in the rate of birth weight, Apgar score <7 (5 minutes), neonatal death, hospitalization to newborn childhood intensive care unit (NICU), and UA pH were found between groups. Average UA pH was 7.29 ± 0.05 and 7.29 ± 0.04 in the CST and no CST groups, respectively (p = .864). Average UA pO2 values were 21.1 ± 8.6 and 15.7 ± 5.0 mmHg in the CST and no CST groups, respectively (p = .016), showing significant differences.Conclusions: Neonatal outcomes and UA pH were slightly different between the groups managed with and without CST. However, UA pO2 values significantly differed between the groups. For FGR management, the use of a CST may allow for early intervention before fetal acidemia and acidosis. For establishing the effects of a CST for FGR management, analysis including several cases and investigation of long-term outcomes of newborn infants is necessary.

A Role for Resistance Exercise in Cancer: Destruction of Circulating Tumor Cells in Contracting Muscle

OBJECTIVEAt the Roswell Park Cancer Institute in the 1980s, Leonard Weiss explored why muscle tissue gets few cancer metastases, despite its large blood flow. (Weiss, L., 1992. Biomechanical interactions of cancer cells with the microvasculature Cancer Metastasis Rev, 11(3), pp.227–235). He found that circulating tumor cells were destroyed in contracting quadriceps muscles and cardiac tissue, and during maximal lung inspiration. He further showed that as cancer cells squeeze through the much smaller capillaries, they elongate to the maximum extension of the cell membrane and hypothesized that additional forces on the cancer cell wall caused cell rupture. We analyzed Weiss' published lung data during a maximal inspiration, and found this induces radial stress of 8.7 KpA on a 4.6 mm diameter lung capillary. In our study, mathematical models were applied to ultrasound generated architectural data of the contracting biceps muscle, to determine radial stress under different exercise conditions.METHODS12 healthy males age 20–30 were asked to flex the right elbow from 5° to 90°, with no load, and then with a 10 pound weight, in supine and standing. Longitudinal 2D B‐mode ultrasound was performed of the long head of the biceps brachii muscle at specific measured locations based upon its proximal portion at the intertubercular groove and distal region at the anterior elbow joint line. Muscle length and maximum diameter was recorded and the truncated cone of the muscle image was converted to a cylinder of the same maximum diameter and shorter length (to keep constant volume). Odegard's strain energy function for small and large deformations associated with the active and passive response of transversely isotropic skeletal muscle was used to determine longitudinal and radial strain and stress, Young's modulus, and stiffness.RESULTSWe found the radial stress during biceps contraction to be: 1) 46 ± 26 KpA with the elbow unloaded at 90°; 2) 42 ± 17 KpA with participant in supine, the elbow at 90° and a 10 pound load on the biceps; and 3) 48±24 KpA with the participant standing and the biceps loaded with 10 pounds. With the elbow in 5° flexion, the radial stress is much lower, (15 KpA), at both loads and in both supine and standing.CONCLUSIONSShortening of biceps muscle results in radial stress well above the level calculated to rupture circulating tumor cells in the lungs. Muscle capillaries have stiffening of their wall, so the high radial stress of a short length contraction may be necessary for tumor cell destruction in muscle tissue. Large muscle metastases are found in very few persons with common cancers – lung (2%), colon (1%), breast and prostate (&lt;.5%). In contrast, extraocular muscles rarely contract to their shortest, and metastases are found here in 6% of persons with locally advanced or metastatic breast cancer, and in 12% of all persons dying of cancer. Normal resting cardiac output (CO) is 5 l/min, with a pulse of 80 and a blood volume of 5 liters. Resistance exercise sufficient to raise pulse rate 50% to 120 will raise CO similarly 50% to 7.5 liters/min, with 1/3 the cardiac output now going through the exercising muscle. Every minute of exercise thus leaves 2/3 blood volume unfiltered. After a short 7 minutes of this level of exercise, all but .677 or 0.02% of the blood volume will have passed through the exercising muscle. We suggest design of exercise for persons with cancer based on aspects of muscle and capillary architecture.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

No. 197a-Fetal Health Surveillance: Antepartum Consensus Guideline.

This guideline provides new recommendations pertaining to the application and documentation of fetal surveillance in the antepartum period that will decrease the incidence of birth asphyxia while maintaining the lowest possible rate of obstetrical intervention. Pregnancies with and without risk factors for adverse perinatal outcomes are considered. This guideline presents an alternative classification system for antenatal fetal non-stress testing to what has been used previously. This guideline is intended for use by all health professionals who provide antepartum care in Canada. Consideration has been given to all methods of fetal surveillance currently available in Canada. Short- and long-term outcomes that may indicate the presence of birth asphyxia were considered. The associated rates of operative and other labour interventions were also considered. A comprehensive review of randomized controlled trials published between January 1996 and March 2007 was undertaken, and MEDLINE and the Cochrane Database were used to search the literature for all new studies on fetal surveillance antepartum. The level of evidence has been determined using the criteria and classifications of the Canadian Task Force on Preventive Health Care (Table1). This consensus guideline was jointly developed by the Society of Obstetricians and Gynaecologists of Canada and the British Columbia Perinatal Health Program (formerly the British Columbia Reproductive Care Program or BCRCP) and was partly supported by an unrestricted educational grant from the British Columbia Perinatal Health Program. RECOMMENDATION 1: FETAL MOVEMENT COUNTING: RECOMMENDATION 2: NON-STRESS TEST: RECOMMENDATION 3: CONTRACTION STRESS TEST: RECOMMENDATION 4: BIOPHYSICAL PROFILE: RECOMMENDATION 5: UTERINE ARTERY DOPPLER: RECOMMENDATION 6: UMBILICAL ARTERY DOPPLER.

Betulinic acid lessens oxidative stress and impairment of aortic contraction induced by lipopolysaccharide in rats

Betulinic acid lessens oxidative stress and impairment of aortic contraction induced by lipopolysaccharide in rats

124: The role of the contraction stress test in deliveries with oligohydramnios

To examine the implementation of the contraction stress test (CST) to decide the mode of delivery in pregnancies with oligohydramnios. Retrospective cohort study. Once labor induction was indicated, CST was performed to all women from 34 gestational weeks with oligohydramnios (AFI<5cm) between 2005-2011. Women with abnormal CST (i.e positive or equivocal), underwent cesarean delivery (CD) without a trial of labor and those with negative CST had a trial of labor. Patients' flow chart is described in the figure. Among 1221 patients with oligohydramnios, a CST was performed in 987 patients (80%). Eighteen patients (1.8%) were operated on due to the CST results without a trial of labor. The rest (N=969; 98.2%) were allowed a trial of labor. Significant risk factors for abnormal CST were primiparity, increased gestational week and IUGR fetuses (table). Among the negative CST cases, 95 (11%) delivered by CS. of them, 78 (69%) women were operated on due to non reassuring fetal monitoring. Seventy (90%) women were operated on in the latent phase, while only 6 (8%) and 2 (3%) women were operated on in the active phase and second stage of labor, respectively. Negative CST in oligohydramnios is associated with favorable delivery outcome, particularly once the woman has entered the active phase of labor. It is a poor predictor for fetal compromise during labor in women with oligohydramnios, however, it may be beneficial when oligohydramnios is associated with primiparity, increased gestational week or IUGR fetuses.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Shrinkage stress of high and low viscosity bulk-fill composites with incremental and bulk fill techniques

Purpose Evaluate shrinkage stress of incremental and bulk filling techniques of high and low viscosity bulk fill nanohybrid resin-based composites (RBCs) by assessing cuspal deflection, microleakage, and gap formation. Flexural modulus of different RBCs was also studied. Patients and methods Eighty molars were divided into four groups according to the type of RBCs. Each group subdivided into two subgroups (n = 10) depending on application techniques; A: bulk fill and B: incremental filling. Buccal and palatal cuspal deflection was measured by strain gauge. All teeth were subjected to several steps to evaluate cervical microleakage% by Stereomicroscope. Scanning electron microscope was used to estimate gap formation%. Flexural modulus was measured by three-point bending test. Kruskal–Wallis's test was used for comparison of quantitative variables and post hoc test was used for multiple comparisons. χ2 test was used to test the qualitative data. P value less than or equal to 0.05 was considered statistically significant. Results Cuspal deflection: bulk filled teeth of low viscosity SDR flow (group III) and incremental filled teeth of the four groups were not significantly different from each other and were significantly lower than bulk filled teeth of high viscosity materials. Cervical microleakage%: the lowest scores were recorded in group II and group III which were not significantly different between both application techniques. Gap formation%: the two lowest means % were recorded for bulk filled teeth of group III and incremental filled teeth of group IV. There was a positive correlation between cuspal deflection, cervical microleakage% and gap formation%. Flexural modulus of group III was significantly lower than other groups which were not significantly different from each other. Conclusion Incremental filling technique was the best technique to decrease contraction stress and its complications. Bulk filling technique of low viscosity SDR achieved comparable results to incremental filling technique.

515: The role of the contraction stress test for improving obstetrical outcomes in pregnancies with small for gestational age fetuses

515: The role of the contraction stress test for improving obstetrical outcomes in pregnancies with small for gestational age fetuses

Effect and Safety of Labor Epidural Analgesia with Intermittent Boluses of 0.1% Bupivacaine with Fentanyl on Fetal and Maternal Outcomes and Wellbeing.

Background:Labor analgesia has been shown to have few undesirable effects on the course and outcome of the labor as well as on the fetal well-being.Aims:This study aims to assess neonatal outcome following lumbar epidural analgesia with intermittent boluses of 0.1% bupivacaine with fentanyl. The secondary objectives included assessment of maternal analgesia, complications, and outcome of labor.Setting and Design:Prospective observational study conducted at a tertiary care teaching institute.Subjects and Methods:Sixty-three patients for labor epidural analgesia were recruited. Epidural catheter was inserted in L4–L5 or L3–L4 interspace. After confirmation of the position of catheter, 3 mL of 0.5% bupivacaine with 20 μg of fentanyl made to 15 mL was administered. After 30 min, efficacy of analgesia was assessed by visual analog scale (VAS). The same bolus dose was repeated after 90 min if the patient complained of pain. A maximum of five top-up doses were allowed.Statistical Test Used:Mean and standard deviation, number and percentageResults:After 30 min of first bolus dose, 93.3% had VAS score of <4. More than 90% patients had adequate analgesia till 4th epidural bolus. During contraction stress test, only two fetuses had late deceleration. About 80% and 98.3% newborns had Apgar of >7 at 1 and 5 min, respectively. Umbilical cord blood pH was ≥7.1 in 98.3% neonates with base excess of >−12. 58.3% delivered normally, 23.3% had instrumental vaginal delivery, and 18.3% required cesarean section.Conclusion:Lumbar epidural analgesia with 0.1% bupivacaine with fentanyl provides optimal neonatal outcome, labor analgesia, and labor outcome.

Closure type effects on the structural pattern of an inverted extensional basin of variable width: Results from analogue models

In order to further understand the controls on the structural configuration of inverted basins, previous research has vastly explored the role of rift-stage stress field variations on the resulting structure produced by basin inversion. Analogue modeling has broadly enabled geoscientists to gain insight into the controls on the structural evolution during basin inversion, such as: the inherited structural array of the basin, sedimentary load or sedimentary thickness, plan-view shape of the basin (length and width), and variations on the governing stress field, among other factors. This work sheds light on the influence exerted by the closure style on inversion of an elongated model basin with a variable width, generated by differential extension. We subsequently induced inversion by modifying the orientation of the post-rift contractional stress field: (i) in a first model, contraction is homogeneous along-strike (parallel to the major axis of the basin); and (ii) in a second model, contraction is heterogeneous along-strike and exerted in the same orientation and amount in which extension was induced (about a pivot point). We focus on the three-dimensional geometry of the structures generated by inversion, their vergence and surficial trace, and where they are prone to concentrate within the basin, to finally analyze and compare our results with natural examples of inverted Andean basin systems. Our results indicate that most of the contractional deformation imposed in the analog models is absorbed in the interiors of the basin in its widest zones by means of inverted normal faults and backthrusts. However, when the amount of shortening is higher than extension, deformation is propagated outside the basin where shortcuts and new oblique reverse faults are dominant, which promote a major uplift.

The Influence of Water Sorption of Dental Light-Cured Composites on Shrinkage Stress.

The contraction stress generated during the photopolymerization of resin dental composites is the major disadvantage. The water sorption in the oral environment should counteract the contraction stress. The purpose was to evaluate the influence of the water sorption of composite materials on polymerization shrinkage stress generated at the restoration-tooth interface. The following materials were tested: Filtek Ultimate, Gradia Direct LoFlo, Heliomolar Flow, Tetric EvoCeram, Tetric EvoCeram Bulk Fill, Tetric EvoFlow, Tetric EvoFlow Bulk Fill, X-tra Base, Venus BulkFil, and Ceram.X One. The shrinkage stress was measured immediately after curing and after: 0.5 h, 24 h, 72 h, 96 h, 168 h, 240 h, 336 h, 504 h, 672 h, and 1344 h by means of photoelastic study. Moreover, water sorption and solubility were evaluated. Material samples were weighted on scale in time intervals to measure the water absorbency and the dynamic of this process. The tested materials during polymerization generated shrinkage stresses ranging from 6.3 MPa to 12.5 MPa. Upon water conditioning (56 days), the decrease in shrinkage strain (not less than 48%) was observed. The decrease in value stress in time is material-dependent.

Model-based inverse estimation for active contraction stresses of tongue muscles using 3D surface shape in speech production

This paper presents a novel inverse estimation approach for the active contraction stresses of tongue muscles during speech. The proposed method is based on variational data assimilation using a mechanical tongue model and 3D tongue surface shapes for speech production. The mechanical tongue model considers nonlinear hyperelasticity, finite deformation, actual geometry from computed tomography (CT) images, and anisotropic active contraction by muscle fibers, the orientations of which are ideally determined using anatomical drawings. The tongue deformation is obtained by solving a stationary force-equilibrium equation using a finite element method. An inverse problem is established to find the combination of muscle contraction stresses that minimizes the Euclidean distance of the tongue surfaces between the mechanical analysis and CT results of speech production, where a signed-distance function represents the tongue surface. Our approach is validated through an ideal numerical example and extended to the real-world case of two Japanese vowels, /ʉ/ and /ɯ/. The results capture the target shape completely and provide an excellent estimation of the active contraction stresses in the ideal case, and exhibit similar tendencies as in previous observations and simulations for the actual vowel cases. The present approach can reveal the relative relationship among the muscle contraction stresses in similar utterances with different tongue shapes, and enables the investigation of the coordination of tongue muscles during speech using only the deformed tongue shape obtained from medical images. This will enhance our understanding of speech motor control.

Metabolic Stress-Induced Activation of AMPK and Inhibition of Constitutive Phosphoproteins Controlling Smooth Muscle Contraction: Evidence for Smooth Muscle Fatigue?

Metabolic stress diminishes smooth muscle contractile strength by a poorly defined mechanism. To test the hypothesis that metabolic stress activates a compensatory cell signaling program to reversibly downregulate contraction, arterial rings and bladder muscle strips in vitro were deprived of O2 and glucose for 30 and 60 min (“starvation”) to induce metabolic stress, and the phosphorylation status of proteins involved in regulation of contraction and metabolic stress were assessed in tissues under basal and stimulated conditions. A 15–30 min recovery period (O2 and glucose repletion) tested whether changes induced by starvation were reversible. Starvation decreased basal phosphorylation of myosin regulatory light chain (MLC-pS19) and of the rho kinase (ROCK) downstream substrates cofilin (cofilin-pS3) and myosin phosphatase targeting subunit MYPT1 (MYPT1-pT696 and MYPT1-pT853), and abolished the ability of contractile stimuli to cause a strong, sustained contraction. Starvation increased basal phosphorylation of AMPK (AMPK-pT172) and 3 downstream AMPK substrates, acetyl-CoA carboxylase (ACC-pS79), rhoA (rhoA-pS188), and phospholamban (PLB-pS16). Increases in rhoA-pS188 and PLB-pS16 would be expected to inhibit contraction. Recovery restored basal AMPK-pT172 and MLC-pS19 to control levels, and restored contraction. In AMPKα2 deficient mice (AMPK), the basal level of AMPK-pT172 was reduced by 50%, and MLC-pS19 was elevated by 50%, but AMPK did not prevent starvation-induced contraction inhibition nor enhance recovery from starvation. These results indicate that constitutive AMPK activity participates in constitutive regulation of contractile proteins, and suggest that AMPK activation is necessary, but may not be sufficient, to cause smooth muscle contraction inhibition during metabolic stress.

The influence of delayed light curing on the degree of conversion and polymerization contraction stress in dual-cured resin luting agents

The aim of the study was to assess the effect of delayed photo-initiation on the polymerization contraction stress (PCS) and degree of conversion (DC) of a dual-cure resin-luting agent. Thirty-five disk (6 mm × 1 mm) samples (n = 10 each group) of dual cure resin luting agent for PCS assessment were fabricated and polymerized using two illuminated quartz rods. Based on the delay in photo-initiation, 30 disks were divided among six groups [group A-0 min (min) delay, group B-2 min, group C-4 min, group D-6 min, group E-8 min and group F-10 min]. A non-photoinitiated group (group G – chemical cure – n = 5) was included as control. The PCS for all specimens was assessed using a Tensometer. For DC evaluation thirty-five specimens were divided into seven groups with delays in photo-initiation (group H-0 min, group I-2 min, group J-4 min, group K-6 min, group L-8 min and group M-10 min, group N-chemical cure). DC was assessed using attenuated total reflectance spectroscopic technique. Statistical comparison among groups was performed using analysis of variance (α = 0.05). The maximum and minimum PCS and DC values with delayed photo-initiation was observed in group-C (3.34 MPa) & group-F (2.44 MPa); and group-M (0.78 MPa) and group-H (0.55 MPa) respectively. Chemically cured samples showed the least PCS (group-G, 1.94) and DC (group-N, 0.53) values in their respective categories. PCS significantly decreased with delayed photo-initiation. A significant increase in DC was noticed when photo-initiation was delayed in the dual cure resin luting agent.

Antiasthma activity of Eucalyptus grandis essential oil and its main constituent: Vasorelaxant effect on aortic smooth muscle isolated from nomotensive rats

Asthma is a chronic inflammatory disorder of the airways. It is characterized by an inflammation of the airways causing dysfunction. Asthma is associated with widespread airflow obstruction and increase in airway responsiveness to a variety of stimuli. An asthma attack is accompanied by wheezing, shortness of breath, chest tightness and coughing. The anti-asthmatic and anti-cough activities of the essential oils and 1,8-cineole on rats were assessed. These activities were induced and challenged with histamine and acetylcholine using an ultrasonic nebulizer for asthma and exposure to ammonia for coughs. Anti-inflammatory activities of the essential oils and 1,8-cineole were determined using the cotton pellet granuloma test. Muscle contraction studies where carried out using the vascular reactivity on aortic smooth muscle. The oils exhibited concentration dependent anti-asthma and anti-cough activities. Significantly, 1,8-cineole isolated and purified from the essential oil showed a concentration dependent anti-inflammatory, anti-cough and anti-asthma activity and The essential oils showed vasorelaxant activity. The ability of the essential oils and 1,8-cineole to directly dilate smooth muscle and relieve the stress of bronchial contraction and obstruction of the airways passage validates the use of Eucalyptus grandis as an anti-asthmatic and anti-cough agent. It is concluded that the essential oils have the potential to be used as an anti-asthma and anti-cough therapy. This study also justifies its use by traditional healers in the treatment of asthma and coughs in Zulu folklore medicine.