Is the reciprocating movement per se able to improve the cyclic fatigue resistance of instruments?

AIM: To compare cyclic fatigue resistance of two geometrically similar nickel-titanium instruments, used in conditions similar to clinical use in reciprocating and continuous rotary motion. METHODOLOGY: Four groups of eighteen instruments each, Reciproc(®) files sizes ISO 25 and 40 (R25 and R40) and Mtwo(®) files sizes ISO 25 and 40 (M25 and M40), were tested in reciprocating and continuous rotary motion, employing a novel experiment device. An artificial root canal (diameter, 1.4 mm; angle of curvature, 60 °; and curvature radius, 5 mm) was milled into a stainless steel block. To simulate clinical conditions, instead of rotating the file in static position, the set-up was designed to produce a continuous up-and-down pecking motion along the vertical axis of the instrument. Time to fracture (TTF) and push-pull cycles (PPC) were recorded, the number of cycles to fracture (NCF) was determined, and fractured instrument surfaces were examined under a scanning electron microscope (SEM). RESULTS: Mean time to fracture was 34.44 ± 8.58 min for R25 in reciprocation motion, 35.77 ± 4.82 min for R40 in reciprocation motion, 12.15 ± 1.74 min for M25 in continuous rotary motion and 13.27 ± 2.02 min for M40 in continuous rotary motion, whereas 28.52 ± 3.27 min for R25 in continuous rotary motion, 23.87 ± 1.52 min for R40 in continuous rotary motion, 31.07 ± 1.79 min for M25 in reciprocation motion and 31.08 ± 3.26 min for M40 in reciprocation motion. There was a significant difference (P < 0.0001) for the cyclic fatigue resistance between the reciprocation motion and the continuous rotary motion groups. Reciproc(®) files in reciprocating movement had a significantly higher NCF than Mtwo(®) files, when used in continuous rotation. The highest resistance to failure was shown by Reciproc(®) files in reciprocation movement, followed by Mtwo(®) files in reciprocation and Reciproc(®) files in continuous motion. Mtwo(®) files in continuous rotary movement had the least resistance. SEM analysis of the fracture surface confirmed typical features of cyclic fatigue failure. CONCLUSION: Reciprocating movement increased the cyclic fatigue resistance of NiTi instruments.

Are ball pits the playground for potentially harmful bacteria?

Ball pits, enclosed play areas with padded floors and pits of small plastic balls, have become popular features for children at fast food restaurants. This pilot study sought to identify and confirm bacterial organisms that place children at a potential health risk in three play pits within fast food restaurants. Data for this descriptive study were randomly collected from restaurants offering play pits with multicolored, round, hollow, plastic balls within urban communities of the Tidewater region of Virginia. Specimens were collected from entrances into the ball pits as well as various areas of the bottom lining to incur a representative sample. Results indicated an increased level of normal flora as well as nonhuman flora, demonstrating that bacteria are present within the ball pits. The results question the safety of these play pits for both health care providers and parents. Nurses play a vital role in public awareness through health education. Disinfection protocol and proper handwashing are the keys to making ball pit play areas safe for children.