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 and30-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

ReferencesMalamed, Stanley. Handbook of Local Anesthesia. 5th Edition. Mosby.

2004