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Biomedical subjects

M E Olsen

Publications and source records attributed to M E Olsen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Effect of varying etching times on the bond strength of ceramic brackets.

Damage to the enamel surface when debonding orthodontic ceramic brackets has been a clinical concern. Ideally, bond failure at the bracket-adhesive interface should occur without damaging the enamel surface. The purpose of this study was to determine the shear bond strength and debonding failure modes of ceramic brackets with varying etching times. Sixty freshly extracted human premolars were pumiced and divided into six groups of 10 teeth. Each group was assigned an etching time interval of either 30, 20, 15, 10, 5, or 0 seconds with 37% phosphoric acid. Ceramic orthodontic brackets were bonded to each etched tooth by using the same orthodontic bonding system. The teeth were mounted in phenolic rings and stored in deionized water at 37 degrees C for 48 hours. A Zwick universal testing machine (Zwick GmbH and Co., Ulm, Germany) was used to determine shear bond strengths. The residual adhesive on the enamel surface was evaluated with the Adhesive Remnant Index. The results of the analysis of variance indicated that there were significant differences in bond strengths between the various etching times (p=0.0001). The Duncan multiple range test revealed that the 5-second and no etch group exhibited significantly lower bond strengths. The results of the Chi square test evaluating the residual adhesives on the enamel surface also revealed significant differences (p=0.0001). However, when the 5- and 0-second groups were dropped from the test, the Chi square test revealed no significant differences between the 30-, 20-, 15-, and 10-second groups (p=0.211). In conclusion, decreasing etching time between 30 and 10 seconds does not significantly affect either bond strength or the site of bond failure.

Acid Etching, Dental↗
PubMed1996

Effects of fluoride application on shear bond strength of orthodontic brackets.

The purpose of this study was to determine the shear bond strength and debonding failure modes of orthodontic brackets bonded to teeth that have been treated with various fluoride concentrations. Thirty-six recently extracted human premolars were divided into three groups: prophylaxis with pumice only, prophylaxis using a 13,500 ppm fluoridated pumice, and prophylaxis with pumice followed by application of a 2500 ppm fluoridated paste. The teeth were etched with a 37% phosphoric acid gel, then bonded with a metal orthodontic bracket. The teeth were mounted in phenolic rings and stored in de-ionized water at 37 degrees C for 72 hours. A Zwick Universal Testing Machine was used to determine shear bond strengths. The residual adhesive on the enamel surface was estimated using the Adhesive Remnant Index. Analysis of variance was used to compare the various groups, and significance was predetermined at p < or = 0.5. The results indicate that there were no significant differences in bond strengths between the treated and untreated teeth (p = .233). The Chi Square test evaluating the residual adhesive on the enamel surfaces also showed no significant differences (p =.456). In conclusion, the use of fluoridated prophylactic pastes with varying fluoride concentrations does not significantly affect shear bond strength or bond failure location.

Acid Etching, Dental↗
PubMed1996

Effect of applying chlorhexidine antibacterial agent on the shear bond strength of orthodontic brackets.

The purpose of this study was to determine whether the application of chlorhexidine as an antibacterial agent affects the shear bond strength and debonding failure modes of orthodontic brackets. Thirty-six recently extracted human premolars were cleaned and randomly assigned to one of three groups: prophylaxis with pumice only prophylaxis using a 13,500 ppm fluoridated pumice, and prophylaxis with pumice followed by application of 0.12% chlorhexidine paste. All teeth were etched with a 37% phosphoric acid gel and metal orthodontic brackets were bonded to each tooth using the same bonding system. The teeth were mounted in phenolic rings and stored in deionized water at 37 degrees C for 72 hours. A Zwick Universal Testing Machine was used to determine shear bond strengths. The residual adhesive on the enamel surfaces was estimated using the Adhesive Remnant Index. The analysis of variance was used to compare the various groups. Significance was predetermined at P < 0.05. The results indicated that there were no significant differences in bond strengths between the chlorhexidine-, fluoride-, and nonfluoride-treated teeth (P = 0.233). The Chi-Square test evaluating the residual adhesive on the enamel surfaces also showed no significant differences (P = 0.456) between the various groups. In conclusion, the use of chlorhexidine and/or fluoride prophylactic pastes does not significantly affect shear bond strength nor bond failure location of orthodontic brackets.

Acid Etching, Dental↗
PubMed1996

Prevalence of left ventricular hypertrophy in a hypertensive population.

AIMS: This investigation was set up to study the prevalence of left ventricular hypertrophy in a hypertensive population with reference to a normotensive control group. From the general population 3498 men and women aged 35, 45, 55 and 65 years old were invited to a health examination. Participants with blood pressure above 160 mmHg systolic or 95 mmHg diastolic or those taking antihypertensive medication or having done so during the previous 6 months were asked to undergo an echocardiographic examination. Normotensive controls were randomly selected from the same population. Of 552 participants in the final study population, 194 were normotensive controls and 358 were in the hypertensive group. Echocardiographic measurements were made according to the Penn conventions and indexed for body surface. Cut-off values for left ventricular hypertrophy were 134 g.m-2 for males and 102 g.m-2 for women. RESULTS: Overall, the prevalence of left ventricular hypertrophy was 14%/20% (men/women) in normotensives and 25%/26% in hypertensives (P < 0.01). After subdivision by age and sex, there was a significant difference in the prevalence of left ventricular hypertrophy between normotensives and hypertensives only in the 65-year-old group (P < 0.02 for males and P < 0.05 for females). CONCLUSIONS: The association between blood pressure and left ventricular hypertrophy in the general population is weak. Left ventricular hypertrophy is only significantly more frequent among hypertensives as compared to normotensives in older people.

Adult↗
PubMed1994

Casual blood pressure in a general Danish population. Relation to age, sex, weight, height, diabetes, serum lipids and consumption of coffee, tobacco and alcohol.

A population survey was conducted on 3608 randomly selected Danes aged 30, 40, 50 and 60 years respectively. Of these, 3400 were not in medical treatment for arterial hypertension. The following parameters were investigated: sex, age, serum lipid levels (total cholesterol, HDL cholesterol, triglycerides), presence of diabetes mellitus, height, body mass index (BMI), and average daily consumption of coffee, tobacco and alcohol. Analysis with multiple linear regression showed that all variables with the exception of triglycerides, HDL cholesterol and height were significantly associated with systolic blood pressure. Likewise all factors except diabetes, triglycerides and height were significantly associated with diastolic blood pressure. Further analysis in which the effect of each parameter was corrected for by the effects of the remaining variables, demonstrated that apart from age and sex only BMI and high alcohol consumption were positively associated with differences in blood pressure greater than a few mmHg. However, the variation in both systolic and diastolic blood pressures was only partly accounted for by the parameters studied--in the covariates analysis R2 for systolic blood pressure was 0.28 and R2 for diastolic blood pressure was 0.30. In conclusion, this investigation demonstrated that blood pressure is relatively independent of other factors important in the development of cardiovascular disease. Of the above-mentioned factors with some influence on blood pressure only age, BMI and high alcohol consumption have potential clinical importance.

Adult↗
PubMed1994

Preconception evaluation and intervention.

Many pregnancies are predisposed to complications by events that occur in the first weeks of gestation. In fact, these complications may occur prior to the time that a woman knows she has become pregnant. Preconception care offers patients the opportunity to address these conditions before conception; the potential for a satisfactory pregnancy outcome is thereby increased. In the following report, I summarize current understandings in preconception care. Recent advances in preconception care have expanded the opportunities for preventing adverse reproductive outcome. Although the study of preconception care is a relatively new innovation, recent studies have shown the value of preconception intervention.

Female↗
PubMed1994

Failed prostaglandin abortion associated with placenta accreta. A case report.

Prostaglandin E2 vaginal suppositories are a highly effective method of second-trimester pregnancy termination. Management of a failed prostaglandin abortion must include a search for the cause of the failure. This case report is the first description of a failed prostaglandin abortion associated with placenta accreta.

Abortion, Therapeutic↗
PubMed1994

Bilateral twin ectopic gestation with intraligamentous and interstitial components. A case report.

Twin ectopic gestations are rare; the majority involve one or both fallopian tubes. The case presented is the first known report of a bilateral twin ectopic pregnancy of this type. The patient experienced a concurrent right broad ligament ectopic pregnancy along with a left interstitial pregnancy. Her history was significant for a left cornual resection eight years previously. This case is additionally noteworthy in that intraligamentous gestations are rare, while interstitial pregnancies following cornual resection are even more uncommon.

Adult↗
PubMed1992

Prenatal care and delivery in an agoraphobic woman. A case report.

Agoraphobia is a psychiatric illness that can cause patients to become functionally homebound. Although the obstetric care of women with agoraphobia has not been described previously, it is likely that the problem is more prevalent than recognized. A pregnant woman initially believed she would be unable to travel to the hospital for delivery. She was given prenatal care and psychotherapy at home; a safe hospital delivery was achieved. The management plan included the in-depth involvement of two physicians, physician preparation for a potential home delivery, patient education about obstetric risks and the harmlessness of agoraphobic panic attacks, and psychologic and marital therapy. Strategies for minimizing medicolegal risks were employed.

Adult↗
PubMed1987

Interaction between renal prostaglandins and angiotensin II in controlling glomerular filtration in the dog.

Although previous studies suggest that the renal vasoconstrictor effects of angiotensin II (ANG II) are normally confined to the efferent arterioles, the mechanisms that prevent ANG II from constricting preglomerular vessels are still unclear. In the present study, the role of prostaglandins (PG) in protecting preglomerular vessels from ANG II constriction was examined in dogs with normal or non-filtering kidneys in which ANG II formation was blocked with captopril and renal artery pressure was servo-controlled at 75-80 mmHg. Before PG blockade (n = 6), ANG II infusion (20 ng min-1 kg-1) decreased renal blood flow (RBF) by 54 +/- 4%, but did not change glomerular filtration rate (GFR) significantly. After PG blockade (n = 6), ANG II infusion decreased GFR by 37 +/- 7% and RBF by 56 +/- 6%, while increasing calculated preglomerular resistance much more than before PG blockade. In another group of dogs, secondary changes in renal resistances, due to tubuloglomerular feedback, were prevented by occluding the ureter during mannitol diuresis until glomerular filtration ceased. After inhibition of tubuloglomerular feedback in non-filtering kidneys (n = 7), ANG II decreased RBF by 40 +/- 3% and increased glomerular hydrostatic pressure, estimated from stop-flow ureteral pressure and plasma colloid osmotic pressure, by 8.7 +/- 1.7 mmHg. Postglomerular resistance increased by 91 +/- 12% while preglomerular resistance was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1985

Angiotensin II natriuresis and antinatriuresis: role of renal artery pressure, renal hemodynamics, and tubular reabsorption.

The aim of this study was to determine the role of changes in renal artery pressure (RAP), renal hemodynamics, and tubular reabsorption in mediating the natriuretic and antinatriuretic actions of angiotensin II (AII). In anesthetized dogs, endogenous AII formation was blocked with SQ-14225 and AII was infused i.v. at rates of 5-1215 ng/kg/min while RAP was either servo-controlled at the normal level or permitted to increase. When RAP was servo-controlled to prevent a rise i RAP, AII infusion at all rates from 5-1215 ng/kg/min decreased urinary sodium excretion (UNaV) and fractional sodium excretion (FENa), while increasing fractional reabsorption of lithium (FRLi), an index of proximal tubule fractional sodium reabsorption and distal fractional sodium reabsorption (FRDNa): When RAP was permitted to increase, AII infusion rates up to 45 ng/kg/min decreased UNaV, and FENa, while increasing FRLi and FRDNa. However, at 135 ng/kg/min and above, UNaV and FENa increased while FRLi and FRDNa decreased when RAP was allowed to rise, even though RBF and FF were not substantially different from the values observed when RAP was servo-controlled. Filtered sodium load was slightly higher when RAP was permitted to increase during AII infusion, compared to the dogs in which RAP was servo-controlled, although the differences were not statistically significant. Thus, even very large doses of AII cause antinatriuresis when RAP was prevented from increasing. The natriuretic effect of high dose of AII is caused by increased RAP which decreases fractional sodium reabsorption in proximal and distal tubules and causes slight increases in sodium delivery to the tubules.

Absorption↗
PubMed1985

Mechanisms of angiotensin II natriuresis and antinatriuresis.

The aim of this study was to determine the role of changes in renal arterial pressure (RAP), renal hemodynamics, and tubular reabsorption in mediating the natriuretic and antinatriuretic actions of angiotensin II (ANG II). In seven anesthetized dogs, endogenous ANG II formation was blocked with captopril, and ANG II was infused intravenously at rates of 5-1,215 ng X kg-1 X min-1 while RAP was either servo-controlled at the preinfusion level or permitted to increase. When RAP was servo-controlled, ANG II infusion at all rates from 5-1,215 ng X kg-1 X min-1 decreased urinary sodium excretion (UNaV) and fractional sodium excretion (FENa) while increasing fractional reabsorption of lithium (FRLi) (an index of proximal tubular fractional sodium reabsorption) and causing no change in calculated distal tubule fractional sodium reabsorption (FRDNa). When RAP was permitted to increase, ANG II infusion rates up to 45 ng X kg-1. min-1 also decreased UNaV and FENa while increasing FRLi and causing no change in FRDNa. However, at 135 ng X kg-1 X min-1 and above, UNaV and FENa increased while FRLi and FRDNa decreased when RAP was allowed to rise, even though renal blood flow and filtration fraction were not substantially different from the values observed when RAP was servo-controlled. Filtered sodium load was slightly higher when RAP was permitted to increase during ANG II infusion compared with when RAP was servo-controlled, although the differences were not statistically significant. Thus, even very large doses of ANG II cause antinatriuresis when RAP is prevented from increasing.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1985

Protection of preglomerular vessels from angiotensin II vasoconstriction by renal prostaglandins.

Previous studies suggest that the renal vasoconstrictor effect of angiotensin II (ANG II) is confined primarily to efferent arterioles, with little direct action on preglomerular vessels. The present study examined the role of prostaglandins (PG) in protecting preglomerular vessels from ANG II constriction. In dogs in which ANG II formation was blocked with captopril and renal artery pressure was servo-controlled, i.v. ANG II infusion (20 ng/kg per min) decreased renal blood flow (RBF) by about 50% while causing no significant change in glomerular filtration rate (GFR) and increasing filtration fraction (FF). After PG blockade, ANG II infusion decreased GFR by more than 30% and RBF by more than 50%, while causing much greater increases in calculated preglomerular resistance (RA) than in dogs without PG blockade. To prevent secondary changes in renal resistances via tubuloglomerular feedback (TGF), glomerular filtration was stopped by occluding the ureter during mannitol diuresis. After inhibition of TGF, ANG II decreased RBF markedly and increased glomerular hydrostatic pressure by 8-10 mmHg due to large increases in postglomerular resistance (RE) with no change in RA. After PG blockade and inhibition of TGF, ANG II decreased RBF by about the same amount as in control dogs but did not change glomerular hydrostatic pressure due to marked increases in both RA and RE. These data suggest that PGs selectively protect preglomerular vessels from ANG II constriction but do not interfere with the effect of ANG II on efferent arterioles.

Angiotensin II↗
PubMed1985

Physiological responses to angiotensin II infusion during chronic angiotensin converting enzyme inhibition in dogs on normal, low and high sodium intake.

The function of the renin-angiotensin system (RAS) is influenced by changes in sodium balance and angiotensin II (ANG II) levels. In previous studies it has been difficult to assess the physiological effects on blood pressure homeostasis of different rates of ANG II infusion and of different levels of sodium in the diet. The present study examined the quantitative effects of ANG II in conscious dogs on low, normal and high sodium intake with the endogenous RAS blocked by continuous intravenous infusion of enalapril [MK-421,N-(1(S)-carbethoxy-3-phenyl propyl)-L-alanyl-L-proline maleate]. Conscious dogs on three different sodium diets, low, normal and high (5, 30 and 250 mmol/day), were infused continuously with enalapril, 4 mg/kg/day, and studied with superinfused ANG II at rates of 0, 1, 3, 6 and 12 ng/kg/min, each period lasting 1 week. Converting enzyme inhibitor (CEI) decreased mean arterial blood pressure (MAP) equally in dogs on low and normal sodium intake by 20 mmHg, but did not have a significant effect in dogs on high sodium intake. The initial infusion of ANG II at the lowest rate had a pronounced effect on MAP in dogs on normal and high sodium, but had no effect in the sodium depleted dogs. However, at the higher rates of infusion, the angiotensin increased the pressure equally at all levels of sodium intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldosterone↗
PubMed1984

Pituitary-ovarian function in mothers who have had two sets of dizygotic twins.

Serum gonadotropin and estradiol levels were measured in 14 women with regular menses during the early and midfollicular phases. Early follicular follicle-stimulating hormone and, to a lesser extent, luteinizing hormone levels were significantly higher in a group of eight women who had had at least one set of dizygotic twins (six of whom had had two sets) than in a control group of six women with no dizygotic twins. Estradiol levels also tended to be higher in mothers of twins, particularly in the midfollicular phase. The two groups of women did not differ in age, height, weight, or parity.

Adolescent↗
PubMed1984

Gonadotropin levels in mothers who have had two sets of DZ twins.

Serum gonadotropin, estradiol, prolactin and alpha-1-antitrypsin levels were measured in the first four days of the menstrual cycle in 14 women who were cycling normally. FSH, and to a lesser extent LH levels, were significantly higher in a group of 8 women who had at least one set of DZ twins (6 of whom had 2 sets) than in a control group of 6 women with no DZ twins. Estradiol levels also tended to be higher in mothers of twins but there were no significant differences in prolactin or alpha-1-antitrypsin concentrations. There were no differences between the means of the two groups in age, height, weight or number of pregnancies.

Adult↗