1 CLASSIFICATION AND MAIN PARTS OF DENTAL ANAESTHETIC CARTRIDGE SYRINGES

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.