2013, Number 2
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ABSTRACTIntroduction: Needle deflection during insertion can, in itself, be a cause of anesthetic failure. Objective: To determine the degree of deflection of 27-gauge and 30-gauge needles using three insertion techniques on a simulated tissue model. Materials and methods: Controlled, experimental in vitro study in which, with the aid of a parallelometer, controlled insertions in hydrocolloids were performed to a depth of 20 mm using 27-gauge and 30-gauge needles (n = 15). Three different insertion techniques were assessed: the direct insertion technique (DIT), the bidirectional rotation insertion technique (BRIT), and a technique proposed in this study, called modified rotational insertion technique (MRIT). The deflection suffered by the needle and its direction were observed under stereomicroscopy. Results: The modified rotational insertion technique was significantly more effective, presenting the lowest needle deflection (p = 0.000). The direction of deflection was directly related to the position of the beveled face of the needle. Conclusions: The vector forces exerted by simulated tissue on the beveled face of the needle during insertion are responsible for the deflection. Using the modified rotational insertion technique, a balance between these forces is achieved when inserting 27-gauge and 30-gauge needles in hydrocolloids.
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