The Armamentarium
4 PARTS:
1) The Syringe
2) The Needle
3) The Cartridge
4) Preparation
The Syringe
Standard of Care  aspirating dental
syringes are the standard of care due to
their ability to aspirate blood if the tip
of the needle is located intravascularly
ADA Standards for Injection Syringes
1. They must be durable and able to withstand repeated
sterilization without damage
2. They should be capable of accepting a wide variety of
cartridges and needles from different manufacturers and
permit repeated use
3. They should be inexpensive, self-contained, lightweight
and simple to use with one hand
4. Provide aspiration so blood can be seen through the glass
cartridge
Breech-Loading, Metallic, Cartridge-Type,
Aspirating #1 Used Syringe In Dentistry
-breech loading implies that the dental cartridge is
loaded from the side
-a needle is attached to the barrel of the syringe at the
needle adaptor
-the needle passes into the barrel and pierces the
diaphragm of the local anesthetic cartridge
Aspirating Syringe
-the needle adaptor is sometimes inadvertently
discarded along with the disposable needle
-the harpoon is a sharp tip attached to the piston
and is responsible for penetrating the thick
silicone rubber stopper (bung) at the other end
of the cartridge
- negative pressure is applied to the thumb ring by the
administrator, if blood enters the glass local anesthetic
cartridge (carpule) then the tip of the needle is
inserted into the lumen of a blood vessel
• chrome-plated brass and stainless steel
-incidence of positive aspiration is between 10-15%
for some injections
-aspiration before injection of local anesthetic is
accepted in the practice of dentistry and is
overlooked to a great extent
-these syringes use the elasticity of the rubber
diaphragm in the anesthetic cartridge to obtain the
necessary negative pressure for aspiration
-multiple aspirations are possible with very little
effort due to a small metal projection that applies
pressure to the rubber diaphragm when the thumb
ring is depressed  negative pressure  aspiration
-this type of aspiration is as reliable as using the
harpoon to check for blood aspiration
Self-Aspirating Syringes
-Major factor for aspiration is the gauge of the
needle being used
-Most doctors using the harpoon-type syringe, retract
the thumb ring back too far and with excessive force
which frequently disengages the harpoon from the
silicone rubber stopper of the cartridge
-1st generation self-aspirating syringes required a thumb disk
which forced the operator to remove their index and middle
fingers from the thumb ring to the thumb disk to aspirate
-2nd generation self-aspirating syringes have removed this
thumb disk
-Dentists only need to stop applying pressure to the thumb
ring for aspiration; aspiration becomes very easy to do
Pressure Syringes
-PDL (intraligamentary) injections make it
possible to achieve single tooth pulpal
anesthesia in the mandible when, in the past,
complete IANB was necessary
-pressure syringes can allow too easy of an administration of
local anesthetic producing pain and post-operative discomfort
-pressure syringes are expensive > $200.00
-can shatter glass cartridge if too much pressure is applied too
quickly
2000 psi Jet Syringes ($1,600)
-needle-less injection
-liquids forced through very small openings, called
jets, at very high pressure can penetrate skin or intact
mucous membrane
-Syrijet is the most popular used today
-Syrijet holds any 1.8 ml cartridge of local anesthetic
-Syrijet is calibrated to deliver .05 to .2 ml of solution at
2000 psi; traditional syringes deliver 600 psi maximum
-primary use is to obtain topical anesthesia before using a
needle
-regional nerve blocks/supraperiosteal injections are still
necessary
-topical anesthetics provide the same effect at a fraction of
the cost
-patients complain of soreness where the 2000 psi hit their
tissue
Safety Syringe
-Aspiration is possible
-some brands come with an autoclavable
plunger and disposable self-contained
injection unit
-all dental safety syringes are made to be single use items
-sliding the index and middle finger forward against
the front collar of the guard makes the needle “safe”
by sliding a protective plastic sheath over the
needle tip that locks into place
-more expensive than reusable syringe units
-large disadvantage arises when it comes to reinjecting; complication ensues due to the needle
tips newly acquired safety coping
CCLAD (Computer Controlled
Local Anesthetic Delivery
-designed to improve ergonomics and precision of injection
technique
-foot activated delivery of solution using finger tip precision
-pen-like grasp offers increased tactile sensation
The Wand
-flow rates of solution delivery are computer
controlled and remain consistent
operator is able to focus attention on the position of
the needle tip while the motor of the machine delivers
local anesthetic at a preprogrammed rate of flow
50 Dentists were injected with traditional syringes and
The Wand; 48 of 50 Dentists preferred to be injected
again themselves with The Wand due to a reported
threefold decrease in the interpretation of pain
-The Wand is less threatening to the patients visually
-allows two rates of delivery:
1) Slow: .5 ml/minute
2) Fast: 1.8 ml/minute
-releasing the foot rheo-stat will tell the machine to
aspirate automatically; the aspiration cycle is
approximately 4.5 seconds
-extremely high pressure in non-resilient
tissues cause (traditional syringe)
moderate/severe pain in most patients
The Wand eliminates a lot of this
discomfort by maintaining constant
pressure delivery of the solution
-less painful PDL, palatal, attached gingiva
injections
References
Malamed, Stanley: Handbook of Local Anesthesia. 5th Edition. Mosby. 2004