Microbial contamination of samples of dental unit water systems in Saudi Arabia

The purpoe of this study was to investigate contamination of the dental unit water systems in a sample of dental clinics in Saudi Arabia. A total of 270 water samples [200mL/sample] was collected from the handpieces line, air-water spray and tap water sources of the dental clinics. Microorganisms were identified using established culturing techniques [Analytab Products Inc.] The prevalence of bacterial contamination was 84% in dental unit water lines of handpieces and 64% in air-water spray, while it was 10% in tap water samples. Bacillus and Pseuodmonas were found to be the predominant [52%] pathogenic microorganisms. The results indicated that dental unit water systems tested were contaminated. Therefore, more effort should be directed to reduce [if not totally eliminate] the number of pathogens in the dental unit water systems

Wear rats of posterior composite resin restorations

The purpose of this study was to determine the wear rates of different posterior composite resin restoration in class I cavities. Conservative class I cavities were prepared in 32 freshly extracted human molar teeth. The teeth were divided into eight groups and restored with the following materials: Concise [c], Adaptic [a], Fulfill [f], Quantum PAC [QP], Occlusion [O], Estilux Posterior [EP], P10 and P50. The specimens were stored in distilled water for 24 hours at room temperature then subjected to mechanical stress for 200.000 cycles, using the Fatigue Stress Apparatus at a rate of one stroke/0.6 sec. and a force of 55 N. During the study, the specimens were thermocycled at temperatures between 5C and 65C. The amount of water was measured after 50.000, 100.000, and 200.000 cycles using the M.L. Scale and the mean value was taken for each group. Reprosil impression of the specimens were made and replicas poured using epo- kwick resin, then the replicas were sputter-coated and examined using the scanning electron microscope. The amount of wear measured for the materials after 50.000, 100.000 and 200.000 cycles were as follows: P50 [35M, 50M, 67.5M], F [75M, 112.5M], A [150M, 175M, 200M], QP [87.5M, 112.5M, 137M], EP [67.5M, 100M, 150M], P10 [75M, 87.5M, 100M]. SEM examination revealed that P50 showed the minimum degree of wear, while A presented the maximum