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Robert P. Kusy BS MS PhD 《American journal of orthodontics and dentofacial orthopedics》2004,125(6):726-732
Using an earlier model, which described the critical contact angle for binding from second-order angulation alone, a more generalized model is derived that combines the effects of angulation and torque. From this vantage point, the onset of binding is evaluated for 3 scenarios: second-order angulation alone, third-order torque only, and a combination of second-order angulation and third-order torque. These scenarios are detailed by plotting the critical contact angle for binding against the torque angle as a function of 10 wire dimensions (16 x 16, 16 x 22, 17 x 17, 17 x 22, 17 x 25, 18 x 18, 18 x 22, 18 x 25, 19 x 25, and 21 x 25 mil), 4 bracket widths (70, 100, 130, and 160 mil), and 4 bracket slots (18, 20.5, 22, and 24.5 mil). From these plots, we learn that each wire base dimension (eg, an 18-mil base as found in 18 x 18-mil, 18 x 22-mil and 18 x 25-mil archwires) has a common maximum critical contact angle for binding. Moreover, each wire-slot combination has a common maximum torque angle, which is independent of bracket width. Finally, we learn that archwire-bracket combinations that use a metric 0.5-mm slot might have some advantages with regard to torquing--given the current philosophy that light, continuous forces are more favorable. 相似文献
74.
It is known that a number of factors may contribute to heart failure in the course of hypertensive heart disease. The relative importance of these factors, however, has not been established. It is maintained, on the one hand, that myocardial weakness in hypertensive heart disease is due primarily to factors resulting from the hypertension itself, and, on the other, to concominant coronary disease. The purpose of the present study is to throw some light on the relative importance of these factors. 相似文献
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Philip F. Giampietro MD PhD Margaret G. E. Peterson PhD Robert Schneider MD Jessica G. Davis MD Stephen W. Burke MD Oheneba Boachie-Adjei MD Charles M. Mueller PhD RD Cathleen L. Raggio MD 《HSS journal》2007,3(1):89-92
Reduced bone mineral density (BMD) was sporadically reported in patients with Marfan syndrome. This may or may not place the
Marfan patient at increased risk for bone fracture. In comparing the BMDs of our patients with those reported in the literature,
it seemed that agreement between values, and hence the degree of osteoporosis or osteopenia reported, was dependent on the
instrumentation used. The objective of this study was to statistically assess this impression. Bone mineral density measurements
from our previously published study of 30 adults with Marfan syndrome performed on a Lunar DPXL machine were compared with
studies published between 1993–2000 measured using either Lunar or Hologic bone densitometry instruments. The differences
of our measurements compared with those made on other Lunar machines were not statistically significant, but did differ significantly
with published results from Hologic machines (P < 0.001). Before progress can be made in the assessment of BMD and fracture risk in Marfan patients and in the evidence-based
orthopedic management of these patients, standardization of instrumental bone density determinations will be required along
with considerations of height, obesity, age, and sex. 相似文献
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David A. Davis 《Canadian Medical Association journal》2004,171(2):149-150
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