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Mercury levels were determined in the urine of seventy dentists and their assistants engaged in full-time restorative dentistry. Twenty nondental personnel were used as controls. The dental personnel were divided among six separate clinics having two basic designs. Ten morning specimens of urine were collected from each subject over a period of 2 weeks, and mercury was determined in duplicate in each specimen by atomic absorption spectrophotometry. Mean urinary mercury values, ranging from 3 to 17 μg per liter and 5 to 124 μg per liter, were obtained for the controls and dental personnel, respectively. Compared to the controls, 65.7 per cent of all personnel and the over-all data from three clinics showed significantly elevated levels of urinary mercury. In one clinic consisting of twelve dental units in one large room, all personnel showed significant elevations in urinary mercury. A comparison of restorative work done in a given period with the mean urinary mercury value for each clinic suggests that, with regard to mercury hygiene, the single-large-room design is less desirable than a situation in which individual dental units are located in separate but adjoining rooms.

This experiment describes resorption rate, light and electron microscopic appearance of the implant site, and tissue distribution and route of elimination of radioactivity from carbon-labelled polylactic acid implants. Fifty-six rats received abdominal implants and were serially sacrificed at 28, 56, 84, 112, 140, 154, and 168 days. Urine and fecal output was measured for radioactivity, along with implant site and several tissues at the time of sacrifice. Tissue distribution of activity was negligible. Resorption rate of the implant was linear with 63.2% remaining after 168 days. Elimination of radioactivity was via respiration, approximately 29.4% by this route. Histologically, the implant was invaded rapidly along septal defects or slowly on broad fronts. Invading cells were characterized either by large double-walled vacuoles or by large accumulations of mitochondria and microvesicles adjacent to the implant surface. The long duration of this type of implant may be an important consideration in surgical applications.

Changes in osseous tissue after injury were studied in monkeys with the use of thermogravimetric analysis (TGA) and mechanical strength measurements. An exponential relationship was found to exist between strength and weight loss for repair tissues 3 to 8 weeks old. The quantitative techniques investigated seem promising for the improved characterization of mineralized tissue.

Young adult guinea pigs maintained on a normal diet were subjected to an experimental bone injury technique and given daily intraperitoneal injections of either a zinc chelate or a zinc salt from the day of injury to death. Animals were sacrificed at four weekly intervals. Bone obtained at the time of injury and repair tissues obtained at death were analyzed for zinc content. Healing was evaluated histologically. The administration of either zinc cysteamine-N-acetic acid (ZnCAA) or zinc sulfate resulted in accelerated bone healing. Best results were obtained with the ZnCAA. There appeared to be a good correlation between increasing levels of zinc accumulation in repair tissues and healing acceleration. Weight gain patterns indicated that there were no toxic effects due to the chelate injections but some possible growth retardation with the levels of zinc sulfate administered.

Lower first molar extractions were performed on white rats given daily intraperitoneal doses, from the day of extraction to sacrifice, of zinc, either as the sulfate or as the chelate complex zinc cysteamine-N-acetic acid. A notable acceleration was seen in the healing of alveolar bone in the zinc-treated animals. The greatest improvement in the rate of healing was seen in the chelate-treated animals. There was some indication, on the basis of animal weights recorded during the experiment, that intraperitoneal injection of ZnSO4 may have had some toxic effect.

Visitors to Italian prisons must be impressed by the fact that the insufficiency and imperfection of their plants are largely compensated by the excellence and ability of their administrative and disciplinary personnel. With notable exceptions, Italian prisons are still housed in more or less ancient buildings; not infrequently they were formerly convents, which, however remodelled and modernized, are structurally unsuited to the best forms of penitentiary construction and unadapted for the installation of helpful hygienic contrivances. On the other hand, the men who superintend and manage them are splendidly equipped for their work. It is not merely that politics plays no part in prison appointments; it is that prison management is a profession and offers a life's career with a pension and certain official honors to those who follow it. Prison directors must be university graduates with a law degree, except in the case of directors of penal institutions for the insane, who must be physicians. All are encouraged to take courses in criminal sociology and penology, and advancement depends on length of service and merit.