Bonding of restorative resins to dentin by means of methacryloylchloride and methacryloyl-R-isocyanate

Abstract – The bonding of restorative resins to dentin by means of an intermediary monomer containing a carboxylic acid chloride or an isocyanate group was investigated. Such intermediary monomers are supposed to react with the organic constituent of dentin. Bond strengths were enhanced by the use of the intermediary monomers, resulting in mean bond strengths of 0.13 kg/mm2. Bond strengths of this order of size are probably too low to be of clinical interest.     

Protective value of sympathectomy of the ear in noise

Noise-induced hearing loss was assessed in unilaterally sympathectomized rats exposed one month to 100 dB L_eq(lin) noise. The systolic blood pressure of these animals was in the range of 110–140 mmHg. Auditory sensitivity was determined electrophysiologically by brainstem response audiometry to 1/3-octave filtered clicks. The results showed that the loss of sensitivity was about 10 dB smaller (p<0.01) on the sympathectomized side. This observation may partially explain the individual differences in susceptibility to noise-induced hearing loss and point towards protective measures and therapeutic possibilities through manipulation of sympathetic activity in the inner ear.     

The Effect of Intravenous Injection of Purified Human Tissue Thromboplastin in Rats

As a background for the development and testing of phospholipase C in the therapy of post-traumatic and post-surgical intravascular coagulation, highly purified tissue thromboplastin was injected i.v. into rats. The levels of factor V, VII, VIII and blood platelets and the activity of the intrinsic coagulation pathway in general (the cephalin test) were followed. Histological examination of pulmonary, kidney and liver tissue was carried out. The dose-response was highly dependent on the injection rate. A marked activation of factor VII and a fall in the activities of factors V and VIII as well as in thrombocyte counts were observed. Very few or no thrombi were seen beyond the pulmonary circulation. The main changes (fibrin-containing thrombi and platelet aggregates) were observed in the lungs during the first 15 min after injection. After 15 min virtually no thrombi or platelet aggregates could be detected. The effect of tissue thromboplastin was counteracted by large doses of antithrombin III.     

A methodological study of errors in vertical measurements of edentulous ridge height on orthopantomographic radiograms

The purpose of this methodological investigation was to study the relative magnitude of the various errors in vertical ridge measurements from orthopantomograms of edentulous patients. The study was divided into two parts, Part I and Part II. Part I included eleven patients. Two standard orthopantomograms were taken of each patient. Part II included five of the eleven patients in Part I. Here, a third X-ray taken with the mouth open was added to the X-rays from Part I. The X-rays were traced by three dentists. Twelve vertical measurements in the maxilla and in the mandible were made. The variance produced by the patients (morphological variance) and those produced by the dentist, the X-ray, the interaction patient-dentist, the interaction dentist-X-ray and the random variance (methodological variances) were separately estimated on the basis of a three-way mixed analysis of variance model. In Part I, on the average, the sum of the methodological variances constituted 1·7 % and 2·5 % of the total variance in the maxilla and in the mandible respectively. The X-ray produced the greatest single variance component, averaging 1·1 % in both jaws. Although generally statistically significant, the remaining methodological variances were of low magnitude. The interaction patient-dentist, however, was not significant in most cases. In Part II, on the average, the sum of the methodological variances increased to 38·8 % in the maxilla and 4·6 % in the mandible, mainly caused by an increase in the variance produced by the X-ray.     

Cavity preparation for restorative resins used with dentin adhesives

The marginal adaptation of Silux used with and without previous application of different dentin adhesives was analyzed for correlation between maximum marginal contraction gap (MG) and different combinations of one or more of the following variables: area of cavity walls (A), the total area of cavity bottom and cavity walls (B), cavity depth (h), area of cavity surface (S) and cavity volume (V), The best fit to linear regression was found with MG = a + b V/A with the mean of the correlation coefficients being 0.907. The statistical analysis showed that in order to maintain the V/A ratio at a minimum, root caries lesions should not be prepared after excavation if the retention of the restorative resin can be ensured with an effective dentin adhesive. The greatest influence on the V/A ratio was found to be exerted by the radius of the cavity bottom; variation of the radius of the surface of the cavity also influenced the V/A ratio, but to a minor degree.