PubMed · 5266068
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
1969. Editorial: Continuing education.. https://pubmed.ncbi.nlm.nih.gov/5266068/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
STATEMENT OF PROBLEM: The use of endosseous implants to support and retain dental prostheses has become a routine treatment option in many dental practices. Although physical, mechanical, and chemical differences exist among implant systems, survival claims are similar. PURPOSE OF STUDY: This review solicited literature from six implant manufacturers that was thought, by their standards, to be pertinent to the validation of their implant system. METHODS: The literature was reviewed and categorized. CONCLUSION: On the basis of the literature supplied by the manufacturers, only one implant system demonstrated scientifically valid long-term success.
Cyclic fatigue of nickel-titanium, engine-driven instruments was studied by determining the effect of canal curvature and operating speed on the breakage of Lightspeed instruments. A new method of canal curvature evaluation that addressed both angle and abruptness of curvature was introduced. Canal curvature was simulated by constructing six curved stainless-steel guide tubes with angles of curvature of 30, 45, or 60 degrees, and radii of curvature of 2 or 5 mm. Size #30 and #40 Light-speed instruments were placed through the guide tubes and the heads secured in the collet of a Mangtrol Dynamometer. A simulated operating load of 10 g-cm was applied. Instruments were able to rotate freely in the test apparatus at speeds of 750, 1300, or 2000 rpm until separation occurred. Cycles to failure were determined. Cycles to failure were not affected by rpm. Instruments did not separate at the head, but rather at the point of maximum flexure of the shaft, corresponding to the midpoint of curvature within the guide tube. The instruments with larger diameter shafts, #40, failed after significantly fewer cycles than did #30 instruments under identical test conditions. Multivariable analysis of variance indicated that cycles to failure significantly decreased as the radius of curvature decreased from 5 mm to 2 mm and as the angle of curvature increased greater than 30 degrees (p < 0.05, power = 0.9). Scanning electron microscopic evaluation revealed ductile fracture as the fatigue failure mode. These results indicate that, for nickel-titanium, engine-driven rotary instruments, the radius of curvature, angle of curvature, and instrument size are more important than operating speed for predicting separation. This study supports engineering concepts of cyclic fatigue failure and suggests that standardized fatigue tests of nickel-titanium rotary instruments should include dynamic operation in a flexed state. The results also suggest that the effect of the radius of curvature as an independent variable should be considered when evaluating studies of root canal instrumentation.
The FDA Radiology Guideline for the new edentulous patient recommends an initial survey of the arches. In the process of developing this recommendation, the expert panel reviewed the available literature and concluded that there was sufficient evidence to warrant screening radiography rather than selective radiography, which is the principle on which all the other recommendations are based. Our evaluation of the literature used by the panel for the edentulous recommendation identifies critical errors in the analysis of the data. Factors such as a vague definition of abnormality and a geographically diverse sample population might have led the expert panel to suggest a very conservative recommendation for this group of patients. The recommendation failed to consider the treatment impact of findings and was based simply on the large number of observations, regardless of their treatment or pathologic significance. However, in studies in which treatment is considered, it is clear that screening radiography for new edentulous patients does not yield sufficient clinically relevant information to support the guideline.