1 CLASSIFICATION AND MAIN PARTS OF DENTAL ANAESTHETIC CARTRIDGE
SYRINGES
Luca
Martinelli
Basics
of dental anaesthetic cartridge syringes
Publication
no. 1 - 31st October 2012
1. CLASSIFICATION AND MAIN
PARTS OF DENTAL ANAESTHETIC CARTRIDGE SYRINGES
The dental cartridge
syringes are used to perform local anaesthesia.
Requirements and test
methods of syringes are specified in EN ISO 9997 rule.
Dental cartridge
syringes are so called as they use an anaesthetic placed in a tubular vial
whose appearance resembles a firearm cartridge.
With these syringes it
is possible to perform intra-oral anaesthesia such as:
1 by infiltration (submucosa, para-periosteal, intra-osseous, intra-ligament,
intra-papillary);
2 by conduction (truncal or plexus).
1.1 Classification according to the type of aspiration
The dental cartridge
syringes are classified according to the following types:
Type 1: non-aspirating;
Peripress type
Fig. 1
Examples of some types of non-aspirating syringes.
Type 2: aspirating.
Type 2a: with aspiration due to the plunger puling from the needle;
Fig. 2
Examples of some types of aspirating syringes.
The couplings of the tubular vial rubber plunger are many and distinguished by shape and type depending on the manufacturer, the choice must then be made by the dentist.
Fig. 3
Examples of some types of anchor of the syringe plunger for
coupling to the tubular vial rubber plunger
Type
2b: Self aspirating due to the deflection of the tubular vial
rubber diaphragm.
Fig. 4
Examples of some types of self aspirating syringes.
The syringes may be fitted with 1.8 ml
tubular vial or with a longer barrel (a tube housing the cartridge) and
plunger, 2.2 ml tubular vial, the threading of the needle is of the metric
type, but also syringes with "Imperial" (in this case often the name
is also used to refer to the syringe itself) or Whitworth thread type are
available, and some make it possible to interchange the tip.
1.2
Classification according to the loading system
There is also a classification according to the type of loading
of the tubular via, as follows:
1 - Side-loading syringes;
Fig.
5
Example of some side-loading
syringes
1 - Rear-loading syringes;
Fig. 6
Example of a type of
rear-loading syringe
1 - Front-loading syringes.
Fig.
7
Example of some front-loading
syringes
Beyond the various types of syringe, the choice between them
depends on the type of anaesthesia that must be performed.
In the case of anaesthesia by infiltration the front-loading
syringes of the type shown in Fig. 7 can be used, but of course all the other
syringes.
The anaesthesia by conductions requires an aspirating syringe
and therefore all those not allowing aspiration are to be excluded.
1.3 The main parts of the syringe
Fig.
8
Example of aspirating syringe
Fig.
9
Example of self-aspirating
syringe
2.
CONSTITUENT MATERIAL
Generally, dental cartridge syringes are made of nickel-plated
brass (formerly chrome) with parts made of other metals, is now increasingly
used stainless steel, typically an AISI 303 or 304 type.
Some syringes have constructional details such as the finger
grip and the handle of the plunger black coloured, obtained by laying surface
deposits, or made of plastic material (mostly polypropylene) as well as the
protective tubes (explosion-proof) of the vial.
However, there are types of syringes made of "plastic",
usually disposable.
Fig. 10
Example
of syringe made of plastic material.
3. INSERTING THE TUBULAR VIAL
NTO THE VARIOUS TYPES OF SYRINGE
3.1
Side-loading syringes
After
having retracted the plunger of the syringe, insert the tubular vial and then
the anchor of the syringe plunger into the rubber stopper of the tubular vial,
then insert the needle into the syringe, leaving it covered.
Fig. 11
3.2
Rear-loading syringes
Open the hinge of the syringe and after having bent the barrel
fits the tubular vial, from the side of the aluminium capsule, close the
syringe and align the plunger proceeding as in the previous case.
Open the hinge of the syringe and after having bent the barrel
fits the tubular vial, from the side of the aluminium capsule, close the
syringe and align the plunger proceeding as in the previous case.
Fig. 12
3.3
Front-loading syringes
Unscrew the barrel of the syringe, insert the tubular vial and
re-tighten the barrel to the handle, slightly push the plunger and insert the
needle.
Please remember that in the "pen" syringes without the
retracting button of the plunger rack, the latter must be completely removed
from the front and then re-inserted from the rear.
It should be added that the syringes fitted with rack deliver an
"x" amount of anaesthetic per each "click" made.
This amount is not the same for all
syringes (it depends on the manufacturer) since the quantity is determined by
the distance that the plunger covers into the barrel and therefore into the
tubular vial.
Since the size of the rack geometry is known, the amount of
anaesthetic in a tubular vial could be divided depending on the number of
"clicks" a syringe allows, but undoubtedly the best procedure is that
involving the information directly given by the manufacturer, it must be
considered that, in principle, the amounts of anaesthetic delivered with a
"gun" syringe corresponds to about 0.20 ml per "click" and
about 0.05/0.06 ml in case of a "pen" syringe.
Obviously, these values vary from model to model depending on
the different constructive geometry, it is then important to get the
information from the manufacturer of the syringe.
