Determination of the viremia threshold for dental cross-infection in a mouse model.

An animal model of dental virus transmission was developed using the lactate dehydrogenase-elevating virus (LDV) of mice to study cross infection. Mouse-to-mouse cross-infection was carried out by scaling the teeth of LDV-infected donor mice with dental instruments, immediately prior to using the contaminated instruments on the teeth of recipient indicator mice. The level of donor viremia was found to correlate with the rate of virus cross-infection, with a viremia threshold level of 10(7.5) ID50/ml observed for dental cross-infection. The blood volume transferred during dental cross-infection was approximately 10(-4) to 10(-5) ml, demonstrating the inefficiency of virus cross-infection, since deposition of about 1000 virions on dental instruments was associated with the threshold limit. Virus transferred during dental cross-infection rapidly entered the blood circulation, showing that dental cross-infection was not dependent on an oral infection. The results from these model studies predict the general inefficiency of dental instrument virus cross-infection, and a further reduced likelihood of dental cross-infection with appropriately cleaned instruments.

Effectiveness of ultrasonic cleaning of dental instruments.

PURPOSE: To quantitate blood contamination present on dental instruments used for routine prophylaxis and to assess the effectiveness of ultrasonic decontamination in reducing blood and virus contamination on dental instruments. MATERIALS AND METHODS: Human blood contamination present on dental instruments obtained after routine prophylaxis was analyzed using IgG as a blood marker. RESULTS: The estimated contaminating blood volume was found to normally range between 1.4 x 10(-6) to 2.0 x 10(-4) ml. Attempts to saturate the instruments with blood contamination suggested that the maximum possible retained blood volume was about 10-fold higher than the normal levels of contamination. Hand scrubbing of contaminated instruments was both relatively ineffective and inconsistent in removing blood contamination. Decontamination in an ultrasonic cleaner was more effective than hand washing, resulting in greater than a 100-fold reduction of blood contamination. Using a mouse model virus (lactate dehydrogenase-elevating virus, LDV), high levels of virus contamination of dental instruments and dental handpieces were achieved, as determined by assay of residual virus. Ultrasonic treatment reduced the level of virus contamination present on dental instruments by one million-fold, and virus contamination present in dental handpieces was reduced by one thousand-fold. These results provide quantitative estimations of the infection threat and its reduction by ultrasonication, posed by human-exposed dental instruments.

Comparative study: the effects of latex and vinyl gloves on the tactile discrimination of first year dental hygiene students.

The purposes of this study were to determine 1) if there was a significant difference in the tactile discrimination of first year dental hygiene students wearing a vinyl glove as compared to a latex glove; 2) if the subjects' perceptions of their ability to accurately discriminate between surface textures differed when wearing either one of the two gloves; and 3) the individual characteristics of the gloves preferred by the subjects. Twenty-nine first year dental students were randomly assigned to one of the two glove treatment groups. The tactile discrimination ability of each subject was assessed at baseline and three weeks after using the Roughness Discrimination Test (RDT). The subjects wore their assigned gloves when performing laboratory and clinical procedures during the 3-week period. Following this period the RDT was again administered. Subjects then switched gloves for an additional 3-week period, at which time data were collected regarding perceived discrimination ability and glove preference. Data were analyzed using a repeated-measures analysis of variance. Results revealed no significant difference (p less than 0.05) in subject's tactile discrimination ability while 29% indicated that the latex glove had an inhibitory effect. The subjects most frequently preferred the latex glove, citing specific favorable characteristics such as size, fit, comfort and durability while performing clinical procedures. However, the vinyl glove was favored for durability after washing.