The influence of proteolytic enzyme activity from cultures of Bacillus subtilis on decalcified dental tissue

From the culture medium of the Bacillus subtilis strain ATCC 6633 the proteolytic enzyme activity was isolated by ammonium sulphate precipitation and acetone treatment. In the case of the isolated activity it is a question of a serine protease with a pH optimum of 10, which is inhibited by diisopropyl fluoro-phosphate and sodium ethylene diamine tetra-acetic acid and is not influenced by o-phenanthroline. With the enzyme preparations thus obtained, decalcified sections of caries-free human teeth were incubated at pH 7.0 and 37 °C both with and without di-isopropyl fluoro-phosphate. Under the influence of the enzyme action there were changes in the matachromatic structures and finally the disintegration of the decalcified dental tissue. Propitious points of attack are the cement-dentine boundary and the central sections of the globuli. The isolated enzyme thus leads to the same decomposition phenomena as the direct incubation with Bacillus subtilis. With this enzymatic decomposition of the dental tissue, determinable quantities of nitrogen are released biochemically in the incubation solution. It is assumed that the hydrolysed substance is a glycoproteid with a non-collagenic protein component.     

A comparative analysis of the accuracy of implant transfer techniques

Four different implant transfer techniques using two master cast systems (solid cast and Zeiser system) were evaluated and compared with respect to the accuracy with which abutment positions were reproduced. A stainless steel experimental analogue with two anterior and two posterior fixtures and abutments was fabricated. Polyether impressions (14 each) were made by use of four techniques, (I) nonsplinted, (II) splinted with dental floss and acrylic resin, (III) splinted with orthodontic wire and acrylic resin, and (IV) splinted with acrylic resin alone. The fourteen impressions of each technique were divided into two equal groups: group 1, solid cast system, and group 2, Zeiser system. The abutments of each master cast were measured vertically and horizontally with a profile projector. Statistical analysis indicated no significant difference between the splinted and nonsplinted techniques. The Zeiser system provided more accurate interabutment relationships for the posterior region than the solid cast system.     

Magnesium in bone mineral: an in vitro study.

The solubility of magnesium in bone mineral from control and magnesium-dificient rats receiving varying fluoride intakes was assessed. Evidence for the existence of a fluoride-related pool of skeletal magnesium possessing a diminished solubility was obtained.     

A 2-year report on caries prevention by fluoride varnishes in a community with fluoridated water

The benefit of semi-annual applications of sodium fluoride varnish (Duraphat) and silane fluoride varnish (Fluor Protector) was studied in 11-13 year-old children with life-long exposure to fluoridated drinking water (1-1.2 parts/10(6)). Annual clinical and radiographic examinations were made on 67 children in the Duraphat group and 71 children in the Fluor Protector group. Fluoride varnish was applied semi-annually using the half-mouth technique. At the end of 2 years, the mean overall DMFS-increments on the control side and test side of the Duraphat group were 5.0 and 3.8 (p less than 0.01), respectively, and of the Fluor Protector group 3.7 and 3.3 (NS). The caries reductions were 24% and 12%, respectively. Since there were no differences between initial mean DMFS scores of the groups, it was assumed that lower increments in the Fluor Protector group were due to Fluoride ions crossing the midline and providing protection on the control side as well. When increments in the Duraphat control side and the Fluor Protector test side were compared, the caries reduction of Fluor Protector was 35% (p less than 0.01). Fluoride varnishes provide additional benefit even when fluoride intake from drinking water is optimal.