Aortic valve atresia: a new classification based on necropsy study of 73 cases.

Certain clinical and morphologic observations are described in 73 necropsy patients with aortic valve atresia. The mean age at death was 5 days; 80 percent died during the first week of life, and 70 percent were boys. Of the 73 patients, 69 (95 percent) had a hypoplastic left ventricle with intact ventricular septum and either an atretic (25 patients) or hypoplastic (44 patients) mitral valve. The other four patients had a well developed left ventricle with one or more defects in the ventricular septum and either an atretic (one patient) or well developed (three patients) mitral valve. Review of previous reports on aortic valve atresia disclosed that a well developed left ventricle or ventricular septal defect in association with absence of the aortic valve was extremely rare. A new classification for aortic valve atresia is presented based on the status of the ventricular septum, which in turn appears to determine the size of the left ventricular cavity. The predilection for male subjects for all types of aortic valve disease, including atresia, is emphasized.

Clinical study of dental cements. VII. A study of bridge retainers luted with three different dental cements.

In a clinical study of three luting cements, 547 bridges and 162 crowns were permanently cemented. Patients were recalled at 6-month intervals and the restorations were examined for looseness. A pattern of retainer type, cement type and retainer success was demonstrable.

Clinical study of dental cements. VI. A study of zinc phosphate, EBA-reinforced zinc oxide eugenol and polyacrylic acid cements as luting agents in fixed prostheses.

A clinical trial for the final cementation of crowns and bridges with a reinforced zinc oxide and eugenol cement, a polyacrylic acid cement and a zinc phosphate cement was made over a 3-year period. The study involved 441 patients for whom 547 bridges and 162 single restorations were cemented. The patients were recalled at 6-month intervals for the duration of the study and the restorations were examined for looseness. Of the 547 bridges 520 remained firmly cemented to the abutment teeth. Of 1,082 bridge retainers, 1,049 remained in position; success and failure by types of retainer will be the subject of a subsequent paper. Of the 162 single restorations 159 remained in place.

Clinical studies of dental cements: V. Recall evaluation and a zinc phosphate cement.

Patients with restorations cemented with a reinforced zinc oxide-eugenol cement and a zinc phosphate cement were recalled after a four- to seven-year interval. No significant differences in clinical success were observed between restoration luted with the two cements. No significant difference in the incidence of caries at the restoration margins was noted between the cements.

Survival of pathogenic bacteria in crude oil.

The survival of three strains of Staphylococcus aureus and one strain each of Pseudomonas aeruginosa, Bacillus subtilis and Clostridium sporogenes has been investigated in samples of seven different crude oils obtained from Alberta oil fields. One strain each of Staphylococcus aureus, Pseudomonas aeruginosa, Clostridium sporogenes and Bacillus subtilis survived for longer than three years in three of the seven crude oils tested. The majority (four out of six) of the species of test micro-organisms remained viable for over two years in six out of the seven crude oils tested. Paraffinic or asphaltic-naphthenic base crude oils were better suited for the survival of the bacteria employed in these tests than were naphthenic-paraffinic or aromatic-paraffinic base oils. Only Clostridium sporogenes survived longer than three days in one of the crude oils (No. 7) which contained considerably more aromatic material than any of the other oils tested. The public health implications of the experimental results are discussed.

Cimetidine (Tagamet) combined with steroids and H1 antihistamines for the prevention of serious radiographic contrast material reactions.

Cimetidine has recently proved useful in the prophylaxis of certain allergic and other histamine-mediated reactions. We have encountered a patient who had a serious cutaneous and respiratory reaction to Renografin-76 during cardiac catheterization. For the four days preceding his second catheterization, the patient was treated with prednisone, 30 mg daily, diphenhydramine, 25 mg orally, three times a day, intravenous diphenhydramine, 25 mg, three times a day, and Solu-Cortef, 500 mg, intravenously, every six hours. Despite this preparation, he developed an intense reaction to Renografin-76, which did not respond to further doses of Solu-Cortef and diphenhydramine in the catheterization laboratory. Cimetidine, 300 mg, in 100 ml of D5W over 15 minutes, rapidly reversed the entire cutaneous and respiratory phenomenon. In the future, strong consideration should be given to using cimetidine, in its intravenous form, as a routine medication in angiographic laboratories where radiographic contrast materials (RCM) are used. It may be helpful as a pretreatment for recognized RCM reactive patients when catheterization is essential.

An analytical model of the counter-current heat exchange phenomena.

An analytical model for the counter-current heat exchange mechanism in animals has been formulated and a solution has been obtained. The nondimensional parameters that govern the mechanism have been determined in terms of the properties of the animal. The normalized temperatures are functions of normalized distance and, in general, three nondimensional heat transfer conductances. Graphical results are presented for two representative physiological systems. These results allow a delineation of those situations in which counter-current heat transfer is important, and also a quantitative prediction of the heat transfer and temperature distributions. The theory is compared to the available experimental results.

Movement of abutment teeth in spring cantilever bridges: a laboratory study.

The extent and directions of movements of spring bridge abutments were studied on acrylic casts with resilient steep and shallow palates and containing human molar and premolar abutments with compressible 'periodontal ligaments'. Bridges with rigid bars and 'flexible' standard, long and short lengths were cast in Type IV gold, and soldered to Type III gold retainers which were pinned to the abutments. The pontic on each bar was depressed a standard 0.2 mm, and the movement of the abutments registered on a dial gauge resting against the mesio-buccal corner of each retainer. The combination of bar length and palatal contour causing least movement of an abutment was the shortest bar to the molar abutment in the shallow palate model; indeed all bars on this model deflected the molar abutment less than similar bars on the steep palate model. Differences in palatal contours did not affect the extent of movements of the premolar abutments which were comparable to molar movements in the steep palate model. Abutment teeth moved mesio-buccally when the pontic was depressed, and the elbow of the bar usually moved off the palate indicating the fulcrum was positioned along the anterior section of the bar.

Effects of occlusal therapy on pantographic reproducibility of mandibular border movements.

A clinical experiment was undertaken to study the relationship between occlusal therapy and pantographic reproducibility. Twenty-six subjects were categorized according to their ability to reproduce pantographic border movements and were put into either a control nonreproducible, control reproducible, or experimental nonreproducible group. From each subject a sequence of five pantographic surveys consisting of two morning and two afternoon pantographic recordings was taken. Each survey period lasted a minimum of 30 days. The experimental subjects alone were given occlusal splint therapy and occlusal adjustment therapy during the sequence of recall periods. The relationship between the effect caused by occlusal therapy and pantographic reproducibility was analyzed. For the purpose of analysis, the pantographic recordings were assessed a numerical score using a pantographic reproducibility index. A double-blind technique was used until all data were collected.