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Biomedical subjects

J F Osborn

Publications and source records attributed to J F Osborn.

At least 19 recordsLinked to original sources
PubMed1991

The effects of the Chernobyl explosion on induced abortion in Italy.

Four regression models have been fitted to data of the monthly number of induced abortions in Italy between January 1984 and April 1986, in order to predict the number which would have occurred in the 5 months following the Chernobyl explosion. In model I the average number of abortions per day in each month was the dependent variable and calendar months, a linear time trend and previous month's value were the independent variables. Model II included a quadratic time trend term in addition to the independent variables used in model I. Models III and IV were like models I and II except that the dependent variable was the average number of abortions per working day in each month and the effect of the previous month's value was omitted. The 4 models all implied that an excess number of abortions were performed in the 5 months following the Chernobyl accident. The mean daily excess was estimated to be 28 and 52 per day for models I and II and the mean excess per working day was estimated to be 20 and 30 by models III and IV, respectively. Clearly the estimated magnitude of the excess depends on whether the quadratic time trend is included among the explanatory variables, but these results imply that the excess is unlikely to be merely due to chance.

Abortion, Induced↗
PubMed1991

Fixation of hip prostheses by hydroxyapatite ceramic coatings.

We report the histological findings in post-mortem specimens obtained ten days, 17 days and seven weeks after implantation of hydroxyapatite-coated femoral components of hip arthroplasties. There was early deposition of woven bone on the hydroxyapatite ceramic, identical to that deposited on surviving cancellous trabeculae. The space between these deposits became bridged from both sides by new trabeculae, and there was no evidence of an inflammatory reaction or of fibrous tissue formation. The use of an hydroxyapatite coating seems to allow early, sound, secondary fixation of implants.

Biocompatible Materials↗
PubMed1991

Minimising errors in clinical studies by proper selection of sample size.

In the planning of a clinical trial, the statistical aspects of the choice of sample size should be considered. The meaning of statistical terms such as Type I and Type II errors, significance and power are explained. Formulae are given for calculating the required sample size for parallel groups' designs (two independent samples) and matched pair or cross-over designs for both quantitative and qualitative responses. Samples size tables are given with instructions for their use and there are four worked examples. The sample size for a trial depends on the specification of the levels of significance and power and the size of the difference the trial is designed to detect, and these can be somewhat arbitrary. Furthermore, it is often necessary to estimate the standard deviation on the basis of limited information. Thus, the sample size required for a trial cannot be determined precisely, and there can be no exactly right or wrong sample size. However, sensible consideration of sample size should ensure that the trial is not so small as to make the results trivial, nor so large as to be unethical or a waste of resources.

Clinical Trials as Topic↗
PubMed1990

General anaesthesia, a risk factor for complication following induced abortion?

Of the 10,000 abortions performed at the Regional hospital at Modena in Italy between 1982 and 1986, 199 (2%) led to early complications. Investigation of the relationship between the risk of haemorrhage, injury, other complications and all complications and eight explanatory variables revealed that the adjusted odds ratio associated with the use of general anaesthetic compared with local anaesthetic was 4.6 (95% CI, 2.2-9.5) for haemorrhage, 1.3 (95% CI, 0.78-2.2) for injury, 1.6 (95% CI, 1.0-2.6) for other complications and 1.8 (95% CI, 1.4-2.5) for all complications. It is speculated that if the relationship between use of general anaesthetic and risk of complication is causal there could be about 40% fewer cases of complications and 75% fewer cases of haemorrhage following induced abortion if local anaesthesia were used rather than general anaesthesia.

Abortion, Induced↗
PubMed1990

Hydroxyapatite ceramic as a bone substitute.

We have used hydroxyapatite ceramic as a bone substitute for grafting in extensive bone replacement. Hydroxyapatite is composed of calcium phosphate and is incorporated into bone as a physiological mineral. It is not antigenic, carcinogenic or osteogenic. The material used in this study differs from other hydroxyapatite ceramics in that it is an interconnected porous system. Between 1981 and 1986 we used this material on forty five occasions in 44 patients. It was combined with autologous cancellous bone graft in 38 cases and used alone in a further seven. It was usually employed to fill defects after removal of bone cysts and for long fusions in patients with scoliosis. It was also used to fill bone defects after trauma, for non-union in the lumbosacral area, for anterior vertebral fusions, in limb sparing operations for malignant bone tumours, and in exchange operations after failed joint endoprostheses. We have not seen incompatibility or rejection of the implanted material. The rate of postoperative infection was higher than usual due to the selection of patients, but did not appear to be connected with the use of hydroxyapatite ceramic. We were able to review 36 patients up to sixty months after operation. The results are encouraging with no difference in progress compared with patients in whom simple autologous bone grafts had been used.

Adolescent↗
PubMed1990

[Osprovit: hydroxylapatite ceramic for the reconstruction of blow-out fractures of the orbital floor].

Common polymeric implantations, in use for the orbital floor reconstruction, form usually a surrounding fissural space and thus tend to dislocations. With the conservative methods that have been available up to now, the Dura Mater cannot be definitely sterilised so that a transmission of a virus may be possible, which causes the Creutzfeld-Jacob Encephalopathy. As an appropriate alternative-both for primary and secondary reconstruction of the orbital floor-an implantation of dense hydroxylapatite ceramics (Osprovit), anatomically shaped, is indicated. According to x-ray techniques of evaluation it presents itself without artifacts. It does not dislocate because it coalesces physiologically with the surrounding tissues and because of its biocompatibility, it is undoubtedly suitable as a permanent implantation. Post-operative examinations of 20 patients showed neither enophthalmus nor diplopia. All patients were without subjective symptoms.

Adult↗
PubMed1989

Measuring diagnostic consistency.

Statistical analysis can only be as reliable as the data analysed. In clinical or epidemiological dental research, variations in the interpretation of diagnostic criteria can have a marked effect on the reliability of subsequent analysis. Methods of measuring examiner consistency in these circumstances are discussed, and illustrative examples provided.

Child↗
PubMed1989

Comparison of several groups.

Techniques for the comparison of several samples are described. If the response is quantitative, comparison of the sample means is achieved by one-way analysis of variance. If the response is qualitative, comparison of several proportions is achieved by chi 2 tests.

Dentistry↗
PubMed1989

Significance tests. Part 3.

A discussion of basic parametric statistical tests of sample proportions and frequencies is concluded with a description of the chi-squared test. The treatment of distribution-free or non-parametric data is then illustrated with examples of the sign test and Wilcoxon's two-sample rank test.

Child↗
PubMed1989

Significance tests. Part 2.

The comparison of two means obtained from either small or large samples and the comparison of two proportions is described, together with the use of logarithmic transformation of quantitative data in order to stabilise variance.

Mathematics↗
PubMed1989

Significance tests.

Simple methods of determining whether the difference between a sample mean and a given standard value is likely to be due only to sampling error, or to be real and/or of practical importance, are described. The use of the null hypothesis and of standard normal deviates is discussed, and examples are provided to illustrate the points made.

Dental Restoration, Permanent↗
PubMed1989

Probability and sampling.

The concept of probability is introduced, and the role of probability distributions in statistical theory is discussed, with particular reference to the Normal distribution and its characteristics. Sampling and sampling variation are described, together with sampling error, the standard error of the mean, and confidence intervals for determining the likely magnitude of a population mean.

Child↗
PubMed1989

Simple summary calculations.

Methods of measuring the general magnitude or central tendency of sets of data are described, including the mean, median and mode. Similarly, methods of determining the degree of dispersion of the observations about the mean, including range, variance, and standard deviation are presented, together with worked practical examples of their use and importance. The use of algebraic notation in statistics is described.

DMF Index↗
PubMed1989

Descriptive statistics.

The importance of a knowledge of statistical methods in relation to most aspects of dentistry is discussed. Definitions of terms used in descriptive statistical techniques are provided, together with a review of the techniques themselves.

Research↗