How well does the Chemiclave sterilize handpieces?

Using the Food and Drug Administration's protocol for testing health care sterilizers, the author investigated the ability of chemical vapor and steam to sterilize handpieces. Five internal sites of six high-speed handpiece models and four internal positions of one low-speed handpiece model were each inoculated with 10(6) Bacillus stearothermophilus spores. Half-cycle challenges were conducted with Chemiclave models EC 5500 and 8000 (Barnstead/Thermolyne) and with two autoclaves, Tuttnauer 2540M (large chamber) (Tuttnauer USA Co., Ltd.) and Statim Cassette (SciCan USA). Experiments with spores either openly exposed or partially enclosed prove that chemical vapor is an excellent lethal agent, but strongly suggest penetration weakness [corrected].

The emergence of load-oriented sterilization.

Achieving maximum equipment sterilization is critical. Factors that contribute to sterilization efficiency are covered, including sterilization accuracy level, chamber loading and biological indicators.

Failure of the STER-O-LIZER MD 200 to pass the EPA sporicidal test.

The U.S. Environmental Protection Agency (EPA) officially licenses and authorizes use of commercial gas and liquid sterilants. Products registered by the EPA include ethylene oxide gas, formalin-alcohol vapor, glutaraldehyde liquid, and chlorine dioxide liquid. One product that is exempted from EPA registration is the STER-O-LIZER MD 200, in which the active component is electropotentiated saline solution. The manufacturer of the STER-O-LIZER claims that the device sterilizes surgical instruments in 2 minutes. Sterilization claims for the product are based on a test selected by the manufacturer. The EPA, however, is not concerned about the use of the STER-O-LIZER because it is non-toxic to humans. This study tested the validity of the manufacturer's claim by using EPA standards.

Format selection in machine-scored classroom achievement tests.

Performance on classroom achievement tests should reflect student accomplishment on a targeted set of instructional objectives. One prerequisite for meaningful edumetric assessment is the structuring of each component item in an appropriate format. In a comparative study measuring the effect of item format on student performance, incorrect choices were selected 2.4-fold more frequently on multiple choice items than on their content-identical, multiple true-false derivatives. On similar trials, scores on complex multiple-choice items ranged upward of 20 percent higher than on their content-identical, multiple true-false counterparts. The strengths and weaknesses of various test item formats are discussed and specific recommendations for format selection are made.

Effects of sterilization on periodontal instruments.

The sharpness of surgical instruments is of particular importance to the periodontist. In order to study the effects of sterilization on the cutting edges of periodontal curets and scalers, new sharpened instruments were sterilized 10 cycles with saturated steam, formalin-alcohol vapor or dry heat. The instruments were evaluated before and after sterilization with a scanning electron microscope. No visual damage to the cutting edges of stainless steel instruments was evident after sterilization by saturated steam at 250 degrees F, formalin-alcohol vapor at 270 degrees F or dry heat up to 340 degrees F. Carbon steel instruments were not damaged by formalin-alcohol vapor at 270 degrees F or dry heat up to 340 degrees F. Saturated steam caused oxidation and dulling of carbon steel instruments.

Bacteriocin typing of streptococcal isolates from endocarditis.

A typing system based on bacteriocin production and sensitivity for Streptococcus sanguis strains was devised. Bacteriocin producer strains were grown (37degrees C) anaerobically on brain heart infusion-yeast extract agar for 18 h. Bacteriocin indicator strains were suspended to molten brain heart infusion-yeast extract agar and then overlayed onto the producer strain. After an additional 18 to 24 h of incubation, zones of bacteriocin inhibition were recorded. After establishment of the typing system, eight Streptococcus strains from bacterial endocarditis patients were characterized by the typing system. Four patient strains had identical bacteriocin reduction patterns but could be differentiated by differences in their bacteriocin sensitivity. Two isolates from the same patient had identical production and sensitivity patterns. By including both bacteriocin production and bacteriocin sensitivity, all seven epidemiologically unrelated isolates could be differentiated. On the basis of these results, there does not appear to be a correlation between bacteriocin production and infectivity, but the usefulness of the application of a typing system to a clinical situation is demonstrated.

Strain typing of oral streptococci by the use of bacterial antagonism.

Strain-typing methods utilizing microbial antagonism have been developed for S sanguis and for S mutans. The inhibition observed resembled that of bacteriocins. Inhibition within the species S sanguis was obtained with group D streptococci and facultative members of the genus Bacillus. Thirty-three inhibitors were paired (not in all possible combinations) with 37 isolates of S sanguis. Depending on the inhibitor, growth of between 15 and 85% of the sensitive indicators was halted. Three of the inhibitors manifested identical patterns of inhibition. Of the 37 S sanguis isolates, 34 exhibited individual patterns of inhibition. The three exceptions could be differentiated by their antagonism against sensitive indicators of S mutans. Variations in susceptibility to antagonism produced by group D streptococci allowed each of ten strains of S mutans to be typed. Present work for typing the oral streptococci is focused on computer-assisted searches for minimal typing sets. S mutans is sensitive to inhibition by some members of the species S sanguis. From a group of 58 challengers, 44 inhibited at least one of ten strains of S mutans, and 11 strains of S sanguis were able to halt the growth of half or more of the sensitive indicators. These results are useful not only for strain typing but form the basis for in vivo competition studies.