Precision endodontic syringe

A precision endodontic syringe is provided of leak-proof construction which is adapted for precise injection of a paste root canal sealer into the apical part of root canal of a tooth as in root canal work.

SUMMARY OF THE INVENTION 
The present invention relates to a precision endodontic syringe which is 
adapted for the injection of a root canal sealer ordinarily a heavy paste 
into the root canal of a tooth as in root canal work. 
Various syringes have been proposed in the past but they have not been 
fully satisfactory. In accordance with the present invention, a syringe is 
provided which has a fine threaded plunger thereon so that the amount of 
material which is injected can be precisely controlled. 
Another objective of the invention is to provide a syringe of leak-proof 
construction. Certain prior art syringes are adapted for the injection of 
paste or semi-solid materials but will leak and not give precise results 
because of the leakage. The present invention employs a resilient ball 
which forms a tight fit in a mirror-smooth passage through a heavy walled 
cylinder, obviating the danger of leakage and permitting the syringe to be 
used with liquids as well as semi-solid materials without danger of 
breakage. 
An object of the present invention is also to provide a reusable syringe 
which is easy to clean. The internal passage has a mirror-smooth surface 
and extends from one end of the barrel to the other and has no 
obstructions or crevices of any kind therein. Thus, the barrel can be 
easily swabbed completely clean as there are no crevices or the like which 
can collect foreign materials. Further, a replaceable ball is employed 
which acts as the sealing element within the syringe so that this can be 
discarded after a single usage. 
Another object of the present invention is to provide a syringe that can be 
easily manufactured utilizing standard metal turning techniques, ordinary 
bar stock, eliminating the need of expensive molds and the like in 
fabricating a syringe. 
Various other objects and advantages of the invention will be brought out 
in the balance of the specification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings by reference characters, there is shown a 
syringe which includes a thick-walled stainless steel barrel, generally 
designated 5, a needle base 7, a cap 9, a threaded member 11, and a 
resilient ball 13. 
The barrel 5 has a proximal end 15 and a distal end 17. The proximal end 15 
has external threads 19 thereon and a smooth portion with no threads for 
ease in loading. The distal end 17 has a reduced diameter portion 
terminating in a shoulder 21 and having external threads 23 on the reduced 
diameter portion. The barrel includes a mirror-smooth inner cylindrical 
passage 25 which extends completely from one end to the other of the 
barrel. 
The needle holder (hub) 7 has an internal passage 27 having threads to mate 
with threads 23 and further has a smooth passage 29 forming a smooth 
continuation of the passage 25 as is best seen in FIG. 2 The usual needle 
8 is connected to the needle holder 7. 
The cap 9 is larger in diameter than the barrel and has a first set of 
internal threads 31 adapted to mate with the threads 19. The cap also 
includes a second set of threads of reduced diameter designated 33 adapted 
to mate with the threaded member 11. The threaded member 11 has lands 35 
which form a somewhat snug fit with the internal passage 25 of barrel 5. 
The proximal end of the threaded member 11 has a handle 37 thereon so that 
it can be easily grasped by the fingers and turned. 
A resilient ball 39 forms a tight fit within the barrel 25. This ball 39 is 
made of an inert resilient plastic such as nylon or teflon and can be 
replaced after a single use. 
Near the distal end of the barrel 5 are one or more flat spots 41 so that 
the barrel can be easily grasped by forceps. 
It is believed apparent that the syringe described offers a number of 
advantages over syringes heretofore known. The needle base 17 and cap 9 
are easily removed from the barrel without the use of a tool and ball 39 
discarded. Since the passage 25 is continuous from one end of the barrel 
to the other, it is easy to swab out as there are no crevices to collect 
dirt or other residue. Since the parts are of metal in the preferred 
embodiment, they can be easily sterilized and will not explode under 
normal rise. Obvious, the threaded member 11 does not come in contact with 
the material being dispensed so that there is no possibility of the 
plunger causing contamination. 
In addition the distance between 37 and 9 gives a reliable indication of 
the material remaining in the barrel 25.