Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems

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

Transport kinetics of chromium in perfused human placental lobule in late gestation: in vitro study

Objective: Reports relating to maternal-fetal transport kinetics of chromium, an essential trace element in the human pregnancies are scanty. Hence, we thought it interesting to investigate the transport kinetics of this trace element in the human placenta in late gestation in vitro. Methods: Human placentae were collected immediately after delivery from normal uncomplicated pregnancies. Chromium chloride solution (GFS Chem Inc, Ohio, USA) at 10 times the physiological concentrations and antipyrine (Sigma Chem Co., St. Louis, USA) as internal reference marker was injected as a single bolus (100 µl) into the maternal arterial circulation of perfused placental lobules and perfusate samples were collected from maternal and fetal circulations over a study period of 5 minutes. National culture and Tissue collection medium, diluted with Earle's buffered salt solution was used as the perfusate. Serial perfusate samples were collected from fetal venous perfusate for a period of 30 minutes. Chromium concentration in perfusate samples was determined using atomic absorption spectrophotometry and the concentration of reference marker, antipyrine was measured by spectrophotometry. Transport kinetics and transport parameters of study and reference markers were assessed using well-established parameters. Results: Differential transport rates of chromium and antipyrine in 10 perfusions differed significantly for 10 and 50% efflux fractions (ANOVA test, p < .05) while those of 25, 75, and 90% efflux fractions were not significantly different between the study and reference substances. Chromium transport fraction (TF) averaged 54.9% of bolus dose in 10 perfusions while that of antipyrine averaged 89% of bolus dose, representing 61.80% of reference marker TF. The difference observed in TF values of chromium and antipyrine was statistically significant (Student's t-test, p < .05). Pharmacokinetic parameters such as area under the curve, clearance, absorption rate, elimination rate of chromium compared to reference marker was significantly different (ANOVA test, p < .05) between the study and reference substances. Conclusions: Our studies report for the first time maternal-fetal transport kinetics of chromium in human placenta in vitro. Considering the restricted transfer of this essential trace element from maternal to fetal circulation despite its small molecular weight, we hypothesize an active transport of chromium across the human placental membrane. Further studies relating to placental transport kinetics of this trace element in various pregnancy-related disease states are in progress.

Maternal–fetal status of copper, iron, molybdenum, selenium and zinc in patients with gestational diabetes

OBJECTIVE

The status of essential trace elements such as copper, iron, zinc, selenium and molybdenum was investigated in gestational diabetic pregnancies at term, and data were compared to control pregnancies. Fetal/maternal ratios of the elements and copper/zinc ratio were also computed in control and study populations.

METHODS

Samples from maternal venous, umbilical artery and umbilical vein were collected from gestational diabetic and control pregnant women, at the time of spontaneous delivery or Cesarean section, and concentrations of various trace elements were determined by atomic absorption spectrophotometry.

RESULTS

The concentrations of copper, iron, molybdenum, selenium and zinc averaged 2156.2 microg/l, 2020.1 microg/l, 13.1 microg/l, 102.3 microg/l and 656.2 microg/l, respectively, in maternal venous blood in control pregnant women at term (n=15) while in the corresponding gestational diabetic group (n=15), concentrations of the trace elements averaged 2345.8 microg/l, 2061.6 microg/l, 15.0 microg/l, 75.2 microg/l and 610.3 microg/l, respectively. Student's t test showed that the selenium concentration was significantly lower (p<0.05)in the diabetic group compared to controls. Values of other elements were not significantly different. Umbilical blood/maternal blood ratios of the trace elements showed varying differences. The Cu/Zn ratio was found to be significantly different between umbilical and maternal samples of control and study groups, indicating a possibility of compromised antioxidant function in diabetic pregnancies.

CONCLUSIONS

We speculate that altered maternal-fetal status of some essential trace elements in gestational diabetes patients could have deleterious influences on the health of the mother as well as the fetus and newborn.

Effect of methotrexate administration on status of some essential trace elements and antioxidant enzymes in pregnant rats in late gestation

OBJECTIVE

Folate antagonists are widely used in the treatment of various cancerous states. Paucity of data on effect of administration of one such widely used drug, methotrexate (MTX), on the status of essential trace elements and antioxidant enzymes in pregnant women or in pregnant animals prompted us to undertake this study.

METHODS

MTX at a concentration of 5 mg/kg body weight was administered intraperitoneally as single dose to pregnant Sprague-Dawley rats for three consequitive days from day 17 of pregnancy. Control group of pregnant rats received single dose of saline instead of the anti-cancer drug on all the 3 days. After receiving the third dose of drug, the treated rats and control group rats were sacrificed, 1 h after intraperitoneal injection of a cocktail of essential trace elements namely, Cu, Se and Zn administered as a single bolus dose. Blood samples were collected 30 min of trace element cocktail injection, after decapitation and concentrations of trace elements in serum samples were determined by atomic absorption spectrophotometry. Concentrations of antioxidant enzymes, such as superoxide dismutase, glutathione peroxidase and total antioxidant status were determined by specific analytical kits, using spectrophotometry.

RESULTS

In control group(n = 6), serum concentrations of Cu, Se and Zn averaged 2330.5, 614.8 and 2773.2 microg/l, while in study group (n = 6) the concentrations of trace elements averaged 2294, 596 and 2713 microg/l, respectively. Student's t-test did not show any statistical significance (p > 0.05) between various trace element concentrations in control and treated groups. Cu:Zn ratios of control and treated group of rats did not vary significantly as well. Concentrations of superoxide dismutase, glutathione peroxidase in whole blood samples in control rats averaged 165 and 43,260 U/ml, respectively, while in MTX-treated group of animals the corresponding antioxidant enzymes averaged 330.6 and 67,101 U/ml respectively. SOD and GPX values were significantly higher in drug-treated animals compared to controls (Student's t-test, p < 0.05) However, total antioxidant activity was shown to be significantly lower (Student's t-test; p < 0.05) in the drug-treated group compared to control.

CONCLUSIONS

We report for the first time that effect of MTX administration in pregnancy is not associated with significant alteration in disposition of essential trace elements. However, the effect of drug administration on antioxidant enzyme status in pregnant women cannot be excluded while using the drug in clinical states.

Maternal-foetal status of copper, iron, molybdenum, selenium and zinc in obese gestational diabetic pregnancies

Obesity is well known to be a contributory risk factor for several disease states, including diabetes mellitus. Paucity of data on maternal-foetal status of essential trace elements in obese diabetic pregnancies prompted us to undertake this study. Maternal venous and umbilical arterial and venous blood samples were collected from obese gestational diabetic patients (Body Mass Index (BMI) >30) and control obese pregnant women (BMI>30) at time of spontaneous delivery or caesarean sections and concentrations of essential trace elements such as Cu, Fe, Mo, Se and Zn were determined in various samples by atomic absorption spectrophotometry. Activities of antioxidant enzymes, superoxide dismutase (SOD), glutathione peroxidase (GPX) and total antioxidant (TAO) in maternal and umbilical blood were assessed using appropriate reagent kits. Maternal-foetal disposition and exchange parameters of elements studied were assessed using established criteria. Concentrations of Cu, Fe, Mo, Se and Zn in serum of control obese pregnant women (n=10) averaged 2404, 2663, 11.0, 89.0 and 666 microg/l respectively, while in the obese diabetic group (n=11), the corresponding values averaged 2441, 2580, 13.3, 85.1 and 610 microg/l respectively. Activities of antioxidant enzymes such as SOD, GPX and TAO were not significantly different in maternal veins of control and diabetic groups. Varying differences were noted in the case of antioxidant enzyme activities in umbilical blood samples of control and study groups. We conclude that obesity is not associated with significant alterations in antioxidant enzyme status in gestational diabetes and only with relatively minor alterations in status of some essential trace elements.

Effect of hyperglycaemic load on maternal-foetal transport of L-leucine in perfused human placental lobule: in vitro study

The effect of hyperglycaemic loads on L-leucine transport in the maternal-foetal direction has been investigated in human placenta in vitro, using perfusion of isolated placental lobules. National Culture and Tissue Collection medium diluted with Earle's buffered salt solution was used as the perfusate. (14)C-labelled L-leucine along with tritiated water as reference were injected as a 100-microl bolus into the maternal circulation and serial perfusate samples were collected over a 5-min study period. In 6 successful perfusions, the differential transport rate of leucine for 10, 25, 50, 75 and 90% of efflux in the foetal vein averaged 1.26, 1.10, 1.19, 1.10 and 1.04 times respectively that of reference in the control euglycaemic phase. In the experimental hyperglycaemic phases of 27.8 and 55.6 mM/l, leucine transport for the corresponding efflux periods averaged 1.37, 1.33, 1.28, 1.22 and 1.26 times and 1.16, 0.97, 1.08, 1.08 and 1.08 times respectively that of the reference marker. Analysis of variance (ANOVA) test showed that the difference between the three groups was not statistically significant. In the control euglycaemic phase, leucine transport fraction (TF) averaged 40.90+/-3.51% of corresponding water TF while in experimental hyperglycaemic phases, TF of the amino acid averaged 37.80+/-4.82% and 35.61+/-3.21% of water TF respectively. The difference between the control and hyperglycaemic perfusion phases was not statistically significant. Further, no statistical difference could be shown between the two hyperglycaemic perfusion series themselves. Similarly, kinetic parameters such as absorption rate, elimination rate and absorption rate:elimination rate ratio were not significantly different in the hyperglycaemic perfusion phases compared to control phase. Our studies seem to indicate that leucine transport kinetics in in vitro conditions are not altered significantly in placentas exposed to hyperglycaemic loads.

Maternal-fetal transport kinetics of L-Leucine in vitro in gestational diabetic pregnancies

OBJECTIVE

Paucity of data relating to transport of amino acids in gestational diabetic pregnancies prompted us to undertake this study. Transport kinetics of a model amino acid, L-leucine was investigated in gestational diabetic pregnancies in vitro, using perfusion of isolated placental lobules.

METHODS

Placentae from diabetic and control pregnant women were collected post-partum. Suitable placental lobules were then perfused, using National Culture and Tissue Collection (NCTC) medium, diluted with Earle's buffered salt solution as perfusate. 14C-labelled L-leucine along with tritiated water as reference were injected as a 100 ul bolus into the maternal circulation and serial perfusate samples collected over a 5-minute study period.

RESULTS

In 6 successful perfusions, differential transport rate of L-leucine for 10, 25, 50, 75 and 90% of efflux in the fetal vein averaged 1.17, 1.12, 1.22, 1.20 and 1.17 times respectively that of reference in the diabetic group. In the control group (n=6), leucine transport indices for the corresponding efflux periods averaged 1.13, 1.15, 1.18, 1.17 and 1.16 times respectively that of the reference marker. Student's 't' test showed that the difference between the two groups was not statistically significant (p > 0.05) for all the efflux fractions studied. In the diabetic series, leucine transport fraction (TF) averaged 41.2 +/- 4.5% of corresponding water TF while in control group, the amino acid TF averaged 46.5 +/- 6.5% of water TF. The difference between the two series, however was not statistically significant (p > 0.05). Similarly, kinetic parameters as area under the curve, clearance, elimination constant, time for maximum response, absorption rate, and elimination rate in the diabetic and control groups, were not significantly different (p > 0.05) as well.

CONCLUSION

Our study seems to indicate that transport kinetics of leucine under in vitro conditions, do not differ significantly in placentae of gestational diabetic women compared to controls.

Assessment of maternal-fetal status of some essential trace elements in pregnant women in late gestation: relationship with birth weight and placental weight

OBJECTIVE

The status of the essential trace elements copper (Cu), iron (Fe), zinc (Zn), selenium (Se) and molybdenum (Mo) has been investigated in maternal and umbilical cord blood in control, uncomplicated pregnancies at term, and the possibility assessed of a relationship between blood levels of these trace elements and newborn weight and placental weight. Fetal-maternal ratios of the elements were also computed to establish baseline values for the Kuwaiti obstetric population.

METHODS

Blood samples were collected from a maternal vein, the umbilical artery and umbilical vein of normal pregnant women at the time of spontaneous delivery or Cesarean section, and the concentrations of various trace elements determined by atomic absorption spectrophotometry.

RESULTS

The concentration of Cu, Fe, Mo, Se and Zn averaged 2406.1, 3252.1, 11.6, 107.3 and 696.2 microg/l, respectively, in maternal venous blood in the pregnant women (n=39) at term. Umbilical venous/maternal venous ratios of Cu, Fe, Mo, Se and Zn averaged 0.32, 1.96, 1.03, 0.83 and 1.55, respectively. Neonatal birth weight did not correlate with maternal blood levels of the trace elements (p>0.05) in the mother-child pairs studied. However, neonatal weight correlated negatively (p<0.05) with umbilical venous Cu level. Placental weight correlated positively (p<0.05) with Fe and Mo levels and negatively with Zn level in umbilical venous blood.

CONCLUSIONS

Our results indicate an active placental transport for Fe and Zn, while Cu, Mo and Se appear to be exchanged passively between mother and fetus. Evaluation of Fe, Mo, Se and Zn levels in maternal and umbilical cord blood does not appear to be useful in the assessment of fetal growth.