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Biomedical subjects

J C Austin

Publications and source records attributed to J C Austin.

At least 55 records · Page 3Linked to original sources
PubMed1982

The effect of experimental ligation of the external carotid artery and its major branches on haemorrhage from the maxillary artery.

The effect of ligation of the external carotid artery and its major branches on blood flow from the maxillary artery was investigated in four Chacma baboons. The left common carotid artery and its branches were surgically exposed and the maxillary artery was isolated, sectioned and cannulated. Blood flow from the proximal segment of the maxillary artery was determined with and without occlusion of the common carotid artery, the external carotid artery above and below the origin of the linguo-facial trunk and the posterior auricular occipital trunk. Ligation of the external carotid artery below and above the origin of the lingual and facial arteries reduced maxillary artery blood flow by 40% and 73% respectively. Ligation of the external carotid artery above the origin of the lingual and facial vessels, together with ligation of the posterior auricular occipital trunk reduced maxillary artery blood flow by 99.2%. On the basis of these experimental findings, it is suggested that maxillary artery haemorrhage in man may be most effectively controlled by ligation of the external carotid artery in the retromandibular fossa, distal to the origin of the posterior auricular artery, combined with ligation of the superficial temporal artery at the root of the zygoma.

Animals↗
PubMed1981

Effect of surface contamination on band retention.

Laboratory investigations on the retention of orthodontic bands have been concerned with testing the retentive strength of different cements. This study reported here was designed to evaluate the effect of tooth-surface contamination on band retention. Zinc phosphate, silicophosphate, and polycarboxylate (powder: liquid ratio 1.5:1 and 1:1) cements were each tested on different groups of ten teeth. Preformed bands were selected, prepared, and cemented under controlled conditions. Specially designed jigs were used for cementing and for testing. For each cement, the tooth surfaces were pretreated prior to cementing as follows: (1) cleaned with pumice, (2) covered with wet saliva, (3) covered with saliva which was allowed to dry, and (4) covered with liquid paraffin. All specimens were stored in water at 37 degrees C. for 1 week prior to testing. Retention values were established by determining the tensile load required to dislodge the band divided by the surface area of the band. The retention of bands cemented with zinc phosphate and silicophosphate cements was unaffected by contamination of the enamel. The presence of dry saliva and of liquid paraffin significantly reduced the retention of bands cemented with polycarboxylate (P:L 1,5:1) (P less than 0.01). Only the presence of dry saliva reduced band retention when polycarboxylate (P:L 1:1) was used (P less than 0.05).

Acrylic Resins↗
PubMed1981

A simple air sampling technique for monitoring nitrous oxide pollution.

A simple, inexpensive device for the continuous low-flow sampling of air was devised to permit monitoring of pollution by gaseous anaesthetics. The device consisted of a water-filled Perspex cylinder in which a double-walled flexible-film gas sample collection bag was suspended. Air samples could be aspirated into the collection bag at flow rates of as low as 1 ml min-1 by allowing the water to drain from the cylinder at a controlled rate. The maintenance of sample integrity with aspiration and storage of samples of nitrous oxide in air at concentrations of 1000, 100 and 30 p.p.m. v/v was examined using gas chromatography. The sample bags retained a mean 94% of the nitrous oxide in air samples containing nitrous oxide 25 p.p.m. over a 72-h storage period.

Air Pollutants↗
PubMed1981

Effect of cutting speeds and a cavity liner on the pulpal response to Nobetec.

The investigation was undertaken to determine the response to Nobetec, a modified zinc oxide-eugenol cement, widely used as a negative control material in pulpal studies, under conditions of high- and low-speed cavity preparation, with and without a cavity liner Dycal. The pulpal responses were evaluated at intervals of 2 days, 2 weeks and 8 weeks in the permanent maxillary and mandibular incisors in 26 vervet monkeys using labial Class V cavities prepared in 208 teeth. Nobetec was found to be more irritant to the dental pulp than Dycal although this difference was not statistically significant and the degree of irritation was low. The pulpal irritation caused by high- and low-speed cavity preparation was similar and choice of speed should be a matter of personal preference.

Animals↗
PubMed1981

The effects of cavity smear layer removal on experimental marginal leakage around amalgam restorations.

Unvarnished freshly-packed dental amalgam restorations leak initially. However, with time, a marginal seal is usually effected. It is not known whether the smear layer which forms during cavity preparation is associated with this leakage pattern. This study was undertaken to evaluate experimental marginal leakage around amalgam restorations (left in situ for one and 12 wk) which had been placed in cavities prepared with and without removal of the smear layer in vital and devitalized teeth. The cavities were obturated with two types of dental amalgams, a conventional and a dispersed-phase amalgam. The excised teeth restorations were subjected to a fluorescent dye marginal leakage experiment. All of the short-term specimens leaked severely, but some of the long-term specimens displayed significant sealing properties. No significant differences were found between the two types of amalgams. However, the non-vital tooth specimens and cavities without smear layers displayed significantly improved sealing properties.

Animals↗
PubMed1980

Avascular necrosis of the mandibular ramus in the baboon (Papio ursinus) following orthognathic surgery.

The maintenance of an adequate blood supply to the mandible following orthognathic surgery is of extreme importance if satisfactory healing is to be achieved. With this object in mind, this study was undertaken to assess the effects of disrupting the blood supply of the baboon mandible by means of L- and C-osteotomies. Ten adolescent baboons of the species Papio ursinus were used as the experimental animals for the study. On five of them a modified vertical subsigmoid osteotomy (L-osteotomy) and on five a C-osteotomy of the mandibular ramus were performed. In each experimental animal the osteotomy was undertaken on one side of the mandible only, the other side serving as a control. After a postoperative period of 14 days the animals were killed, the entire mandible removed, and the tissues prepared for examination with the light microscope. Histometric analysis revealed a significant degree of avascular necrosis in certain areas of the proximal or condylar fragments and to a lesser extent in the distal fragment. Avascular necrosis was also seen on the control side. It was also revealed that the periosteum and attached muscles of mastication play a role in the blood supply of the mandible and that the additional attachment of the temporalis muscle to the proximal fragment is of no advantage in enhancing the vascularity of that fragment.

Animals↗