The first syringe endo, as far as I can determine, was done in the U.S. Navy in about 1946 by an oral surgeon named Van Zyl.
He used a ZOE cement and injected it using a tuberculin syringe with a specially modified needle.
The needle was removed from the hub, the hole soldered shut and then reattached at right angles to the hub, thus making it possible to get into molars.
The diameter of the needle was about 22 Gauge or more.
This is not hard to understand given the pressures needed to flow ZOE through any needle with a smaller bore.
In the article written at that time, over 50 years ago, a root canal was prepared, and apico done and cement injected through the canal from coronal to apical with the syringe.
The excess was then wiped off the apex and the wound sutured.
In about 1960, two pedodontists, Drs. Alvin Krakow and Harold Burke at Tufts University developed a syringe called the "Pressure Filling Syringe", which is still on the market, sold by PCA Corporation.
This syringe is essentially an internally threaded tube with a threaded rod as a piston.
It is about 6 inches long but the internal, threaded portion is only about 1 inch long.
It uses a special endodontic needle, blunt ended, with a threaded hub, (10-32 for you techies).
This syringe was revolutionary for it's day but today leaves a lot to be desired.
For instance, there was no seal between the internal threads of the barrel and the external threads of the piston.
Therefore the sealer leaked between these threads. Depending on the viscosity of the cement, more or less leaked and thus it was impossible to know, for a given amount of plunger travel, how much cement was being extruded.
Furthermore, after each use the cement had to be dissolved out of the inside threads usually with orange solvent, washed with hot soapy water, rinsed, dried and cooled to prepare it for the next use.
In about 1980 there was a product called Hydron, which was an auto-curing ethyl methacrylate (similar to soft contact lens material) mixed with barium sulfate, that was touted as the ideal root canal filling material. (It is no longer on the market).
The syringe solved the cleaning problem by separating the threads from the plunger. The hub of the disposable needle WAS the barrel and apical end of the plunger was made of nylon which fit the hub snugly.
The inside diameter was 0.25" and the plunger had about a 20 pitch thread.
It was a rather cumbersome device but was on the right track.
In 1978, Dr. Jack Jacklich invented the first
Precision Endo Syringe.
The barrel was about 2.5 inches long and the interior diameter was 0.119" which is slightly less than 1/8 inch (0.125").
To push the cement through, behind the cement was a 0.125" nylon ball (ball valve we called it).
This was pushed through the barrel with a 40 pitch threaded rod, extending through a knurled knob on the distal of the barrel.
Since there was no leakage and the barrel was small, we finally had some control of flow rate. i.e. a given amount of turn produced a given amount of cement.
A few years later, a lever-assisted hypodermic syringe was marketed by Centrix.
It used regular anesthetic needles and had an interior diameter of 1/4 inch.
Combining the lack of micrometer screw control and having double the diameter and thus four times the flow rate per unit of plunger travel made this difficult to control.
This syringe was discontinued in about 1994.
In 1994, Dr. Jack Jacklich invented the
Multi_Mode Syringe to replace the Precision Endo Syringe, which is no longer manufactured.
Instead of one large barrel (cement cylinder), the Multi_Mode has several small replaceable barrels and separates the threaded driver from the plunger.
The advantage is that now, instead of having to empty and clean the barrel, autoclave it, cool it, dry it and reload it, which could take over an hour, it is now possible to flash sterilize the syringe, and replace the cement chamber with one previously loaded.
One of the features of the Multi_Mode and in fact the reason it is called the Multi_Mode is that instead of using the micrometer screw to push on the ball valve, you can replace it
with the driver mechanism of the
PDL Intraligamentary Syringe which allows faster extrusion (but with less accuracy) for rapid back filling.
Many dentists find this such an aid to efficiency that they have one Multi_Mode syringe with a 30 gauge needle for filling the apex and another with the PDL driver attached with a 25 gauge needle for back filling.
In fact one of the prime uses of the PDL/25 gauge combination is to back fill after inserting a gp plug in the apex with the warm gp method.
This is currently in the Beta release stage and will soon be available commercially.
The latest version dubbed the MM-C for Multi-Mode Cartridge Syringe replaces the Multi-Mode which will be discontinued as soon as production quantitites of the MM-C are available.
The advantages of the new system are that there is no needle-cartridge interface to leak and no delrin washer needed.
The cartridges are easier to load and can be preloaded and refrigerated to slow down the setting, warming them up just prior to use.
Loading the injector is simple...
And it uses the same ball valves as previous syringes...
and inserting the injector into the syringe is even easier.
then simply turning the plunger extrudes the cement.
The cartridges are made of aluminum and are designed to withstand any amount of pressure the syringe can apply.
When the canal is filled, the cartridge is simply discarded.
Since no cement gets on the body of the syringe, clean-up is reduced to simply rinsing before autoclaving or dry heat sterilizing.
Needles are available in both 30 gauge and 27 gauge sizes. Larger sizes are planned for the near future.
As with the MM version, the MM-C will also attach to the PDL driver for rapid back filling.
To facilitate the changeover in thousands of dental offices across the U.S. and Canada upgrades of both the Multi_Mode and the older Precision Endo Syringe will be available.
For a limited time, with the purchase of the first 100 needle-cartridges for the MM-C a free exchange will be done on the MM at no charge.
The charge for upgrades on the older Precision Endo Syringe going back to 1977 will be an additional $50.
Although the price is higher $4 each vs. about $0.70, a ball valve comes with each cartridge and there is no need for a washer.