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Quintessence International



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Quintessence Int 31 (2000), No. 1     1. Jan. 2000
Quintessence Int 31 (2000), No. 1  (01.01.2000)

Page 33-39, doi:10.3290/j.qi.a28179

In vitro study of needle deflection: A linear insertion technique versus a bidirectional rotation insertion technique
Hochman, Mark N. / Friedman, Mark J.
Objective: Deflection of dental needles during tissue penetration has been associated with a failure to achieve successfui anesthesia. The purpose of this study was to determine whether needle deflection in a tissuelike substance could be minimized through the use of a bidirectional rotation insertion technique.
Method and materials: Three in vitro deflection test models were constructed, each incorporating a different tissuelike substance of a different density. Each substance was tested with 3 different needle sizes (30-gauge, 27-gauge, and 25-gauge). A customized dental surveyor allowed for standardized needle insertions to a standardized depth of 20 mm. Two different insertion techniques, a linear insertion technique and a newly described bidirectional rotation insertion technique, were tested. Radiographic analysis was performed after each insertion.
Results: The bidirectional rotation insertion technique described was consistently more effective in minimizing needle shaft deflection for 30-, 27-, and 25-gauge needles. The differences were statistically significant. Each of the different tissuelike substances consistently demonstrated this reduction in needle deflection.
Conclusion: The factor that most greatly affects the path taken by a needle through a tissuelike substance is the force vectors that act on the needle's beveled surface. The use of a bidirectional rotation insertion technique minimized needle deflection, resulting in a straighter tracking path for 30-, 27-, and 25-gauge dental needles, in 3 different tissuelike substances tested in this study.

Keywords: computer-controlled drug delivery system, deflection, force penetration, insertion technique, local anesthesia, needle