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The Needle

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					The Needle
 -most needles are stainless steel and disposable

-reusable needles have no place in the practice of
                     Dentistry

-plastic hubs are not pre-threaded; metal hubs are
                    pre-threaded

-a needle whose point is more centered on the long
  axis will have less deflection upon entry into soft
             tissues than a beveled needle
All needles have these components in common:
1) Bevel: point or tip of needle; long, medium and
                          short
        2) Shaft: long portion of the needle
               (diameter of lumen)
3) Hub: plastic/metal piece that attaches the needle
                  to the syringe
   4) Cartridge Penetrating End: perforates the
            diaphragm of the cartridge
            The Gauge
-the diameter of the lumen of the needle; the smaller the
  number the greater the diameter of the lumen; 30-gauge
   needle has a smaller internal diameter than a 25-gauge
  needle; needles in the U.S. are color coded by diameter

 30 Gauge (Blue)
27 Gauge (Yellow)
 25 Gauge (Red)
-Dentists think that using smaller gauge needles
     will result in a less traumatic injection
    experience by the patient which is false

 -In 1972, Hamburg proved that patients could
     not differentiate between 23, 25, 27 and
                30-gauge needles
  Larger gauge needles have advantages over
           smaller gauge needles:

1) less deflection of the needle tip results in greater
                        accuracy

  2) less chance of needle breakage (separation)

  3) easier aspiration of blood through the larger
                       lumens

 4) undetectable pain differences between 25 and
                30-gauge needles
-25 gauge is the needle of choice for injections that
    have a high potential for a positive aspiration
          (PSA, IANB and Mental Block)

 -30-gauge needles are not recommended for any
                specific injection
  Rotational Insertion Technique
      (minimizes deflection)
  Bi-rotational insertion technique
the operator rotates the needle in a back-and-forth
  rotational movement while advancing the needle
 through the tissues; traditional hand-held syringes
   cannot be rotated in this manner, however, The
  Wand can be rotated in this fashion results in less
      deflection, less force is needed for needle
                      penetration
                     Length
-there   are three lengths to dental needles: long, short
                        and ultrashort

-average length of short needles: 20 mm (hub to tip)

-average length of long needles: 32 mm (hub to tip)

 -needles should not be inserted to the hub unless
     absolutely necessary for the success of the
                      injection
-hub is the most common area for breakage because
       this area has the highest level of stress

-when a needle is separated the elastic properties of
 the tissues permit a rebound effect that completely
             covers the needle (buries it)

-25 gauge long needle is the only needle any Dentist
needs to perform any dental injections per Malamed
        (25 or 27-gauge short possible too)
                Problems
 -Stainless steel needles dull after 3-4 penetrations into
       soft tissue causing more pain/post-operative
              discomfort; change your needle

  -If needles are to be penetrated into soft tissue more
       than 5 mm then the needle should not be bent;
               bending needles weaken them

-No attempt should be made to change the direction of a
   needle when it is embedded into tissue; you should
       remove the needle and reinsert it completely

  -Of 60 needles that separated and lead to litigation,
       59 of them were 30-gauge short needles
  (probably inserted too far and above rules broken)
Separated Needle
                  Problems
 -Pain on withdrawal of needle could be due to “fishhook”
   barbs due to errors in manufacturing or too hard contact
                          against bone

-Needle should be recapped immediately after it is withdrawn
      from a patients mouth; avoids unintentional sticks

  -Never put an uncapped needle on the tray for yourself or
   someone else to inadvertently be stuck; always recap the
          needle after you have given any injection
                    References
Malamed, Stanley. Handbook of Local Anesthesia. 5th Edition. Mosby.
                               2004

				
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posted:9/12/2011
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