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Biomedical subjects

D C Smith

Publications and source records attributed to D C Smith.

At least 343 records · Page 19Linked to original sources
PubMed1981

Variables influencing the bond strength of metal orthodontic bracket bases.

The purpose of this study was to examine the retention variables that exist between commercially available bracket bases. Premolar bracket bases from seven manufacturers were examined in the scanning electron microscope (SEM) as received. They were then bonded to human premolars with Dynabond and, after storage in water for 24 hours, tested to failure in shear. The bond-fracture surfaces were also examined in the SEM. Comparison of the SEM observations and shear strength data led to the following conclusions: (1) Weld spots reduce the retentive area. (2) Weld spurs could be responsible for lower bond strengths in some foil-mesh samples. (3) Weld spots on the edges of attachment bases should be avoided to prevent a poor marginal resin-mesh seal. (4) Bracket bases should be designed to prevent air entrapment under the base. (5) The best resin penetration and bond strength were obtained with a fine mesh bracket base of the woven mesh type.

Adhesives↗
PubMed1981

Oestrogen-receptor status and endocrine therapy of breast cancer: response rates and status stability.

The concentration of cellular oestrogen receptor (RE) was measured in both the soluble and nuclear-pellet fractions of biopsies from 1,000 breast cancers. Data suggest that functional steroid RE is always in equilibrium between the soluble and nuclear fractions. However, biopsies from only one-third of patients contained detectable amounts of high-affinity RE in both fractions. Thirty patients out of 42 (71%) whose biopsies contained RE in both fractions, showed objective remission after receiving some form of hormonal manipulation as sole treatment. Response rates in the other categories ranged from 9% for those whose biopsies contained no detectable RE to 24% for those who displayed soluble RE alone. The presence of RE in both fractions of primary disease, whereas RE-negativity was maintained during progression from primary to secondary disease. Other aspects of RE status in relation to stage of disease are analysed.

Adult↗
PubMed1981

Soluble and nuclear oestrogen receptor status in human breast cancer in relation to prognosis.

The relationship between oestrogen receptor (RE) content of primary breast cancer and subsequent prognosis was examined with regard to nodal status. It was found that, within a particular nodal group, patients with tumours containing fully functional RE experienced a longer disease-free interval than those with RE- disease. An earlier observation that RE- primary disease gave rise to distant metastases as first site of recurrence more frequently than did RE+ disease, was not sustained. However, patients with RE+ primary disease had a much reduced chance of dying from cancer within a 3-year period.

Adult↗
PubMed1981

A 5-year clinical evaluation of the effectiveness of a fissure sealant in mentally retarded Canadian children.

The occlusal fissures of 812 permanent and primary posterior teeth were sealed with an ultraviolet polymerisable resin. A half mouth technique was used to evaluate the effectiveness of the sealant in the prevention of fissure caries. At the end of 5 years 19.3% of 409 teeth in 103 children had the sealant completely intact and fissures were partially sealed in 20.8%. Retention was greatest in the mandibular pre-molars. The decay rate was less than half in the treated teeth compared to the control teeth. The net gain was 62 teeth and the percent effectiveness was 57.9%. Thus there was still a highly significant effect of a single application of the fissure sealant after 5 years. Simple cost benefit calculations indicate that the technique is not suitable as a public health measure but has merit for mentally retarded persons and in private practice situations.

Acrylates↗
PubMed1981

Safe and effective catheter angiography through prosthetic vascular grafts.

A new technique for effective percutaneous catheter angiography through prosthetic vascular grafts is described. This method uses overdilatation of the puncture tract and was used safely in 30 angiographic procedures in 27 patients. Good control and easy withdrawal of the catheter were achieved in each case.

Angiography↗
PubMed1981

Endometrial carcinoma: histopathology, survival, and exogenous estrogens.

Pathologic material was reviewed and survival data were obtained on 182 of the endometrial cancer patients reported in our previous study (1975) to compare histopathologic characteristics and clinical behavior (survival) between endometrial adenocarcinoma in estrogen users and nonusers. In addition, relative risk estimates of estrogen-associated endometrial carcinoma were calculated from review results. This work identifies estrogen users as having a significant higher frequency of low-grade tumor with an associated improved survival even when numerous clinical parameters are taken into account. Other histologic or clinical characteristics of the disease did not relate significantly to estrogen use after taking account of histologic grade. The marked increase in endometrial cancer risk among estrogen users was confirmed by the pathology review (relative risk 6.44) and is evident even when attention is restricted to disease that has invaded the myometrium (relative risk 6.09).

Adenocarcinoma↗
PubMed1981

Ivalon breast prostheses: evaluation 19 years after implantation.

Ivalon sponge prostheses, which had been removed from a patient after 19 years, were studied mechanically by light microscopy, by scanning electron microscopy, and by dot map x-ray microanalysis. This study revealed the following. The firmness of these implants was due entirely to their external fibrous capsule, which was 4 to 5 mm in thickness. Once this capsule was incised through, the mechanical compression properties of the implants were identical to fresh unused Ivalon sponge. Contrary to previous observations that Ivalon sponge becomes extensively infiltrated with fibrous tissue, the present implants demonstrated fibrous tissue ingrowth only 2 to 3 mm into the sponge. The open porous nature of the sponge had been preserved after the 19-year implantation period. Whereas extensive calcium and phosphate deposition had previously been demonstrated when Ivalon was implanted into animals, no significant deposition of these ions was observed in the present study.

Breast↗
PubMed1980

Visual acuity following binocular deprivation in the cat.

Threshold visual acuity for three cats which were reared from birth to 4--12 months of age with bilateral lid closure was measured and compared to visual acuity in three cats which had the use of a non-deprived eye. The results indicate that binocular deprivation (BD) results in significant deficits in visual acuity which are proportional to the duration of deprivation. Threshold visual acuities were 3.7 cycles/deg. following 4 months of BD, 3.25 cycles/deg. following 7 months of BD and 2.55 cycles/deg. following 12 months of BD compared to acuities of 6.0, 6.5 and 6.8 cycles/deg9 for cats using a non-deprived eye. All BD cats had recovered from the initial visuomotor deficits, seen in these cats and reported in the literature, following lid-parting. The implication of such deficits in visual acuity on visual discrimination learning in BD cats is discussed.

Animals↗
PubMed1980

The use of the Simmons "Sidewinder" catheter in percutaneous transluminal angioplasty of the renal arteries.

Percutaneous transluminal angioplasty of the renal arteries is a simple procedure that promises to significantly change the patterns of treatment for renovascular hypertension. This paper reports a technique which utilizes the Simmons "sidewinder" catheter for predilatation of a renal artery stenosis or occlusion, and allows subsequent passage of a Grüntzig balloon dilatation catheter in selected difficult cases.

Aged↗