Warm water dental syringe

The specification discloses a dental syringe with a tubular handle adapted to pre-heat water before it is delivered through the syringe tip into a patient's mouth. Water and air supply hoses are connected to the handle, and electric heater and thermostat elements are mounted within the handle for maintaining the temperature of the water therein at from about 95.degree. F. to about 105.degree. F.

BACKGROUND OF THE INVENTION 
The present invention relates to dental syringes, and more particularly to 
a dental syringe with a handle adapted to pre-heat water from a supply 
hose before it is delivered through the syringe tip into a patient's 
mouth. 
Dental syringes are widely used by dentists, dental hygenists, dental 
assistants and the like. They are hand-held instruments which deliver 
water and air into a patient's mouth for washing and drying purposes. One 
such dental syringe is disclosed in U.S. Pat. No. 3,698,088. It includes a 
head, a handle coupled to the head, an elongate discharge tip, and a 
coupling for mounting the tip on the head. Supply hoses for air and water 
extend through the handle and are connected to the head. Valves in the 
head are selectively hand operated to discharge water, air, or both 
through the distal end of the tip. 
Patient comfort is a very important objective in modern dentistry. The 
delivery of cold water into a patient's mouth during treatment can be 
discomforting when the patient's teeth or gums are sensitive to sudden 
changes in temperature. This is especially so when, for example, a 
hygenist is scaling plaque off of the teeth below the gum line. Even when 
local or general anesthetic has been used, e.g. during the performance of 
certain dental surgical operations such as a root canal, exposed tissues 
and nerve endings may be subjected to thermal shock if washed with cold 
water. 
Therefore it is desirable to pre-heat the water before it is delivered into 
the patient's mouth. However, the water must not be too hot or similar 
undesirable effects will result. Lukewarm water at or near body 
temperature is preferred. 
Heretofore, a number of apparatus have been developed for supplying warm 
water through a dental syringe. One apparatus included a remote water 
reservoir or tank, a heater element in the tank, a thermostat for 
regulating the temperature of the water in the tank, and a pump for 
pumping water from the tank through a water supply hose to a dental 
syringe. However, the water supply hose must be at least several feet in 
length in order for the syringe to be easily manipulated. The water cools 
while in the hose. Since the syringe is operated to deliver water 
intermittently, water frequently stands in the supply hose. The longer it 
stands, the more it cools. This problem has been alleviated somewhat by 
continuously recirculating the water, however such a design has 
necessitated the use of an additional water supply hose. In addition, it 
has been difficult to regulate the temperature of the water delivered with 
this design. The temperature fluctuates depending upon the length of the 
water supply hose and the amount of heat dissipated therefrom. 
Another apparatus included a heater wire which runs the length of the water 
supply hose. The heater wire must either be mounted externally of the hose 
or embedded therein during the extrusion of the hose. High production cost 
has been a principal drawback of this design. 
Yet another apparatus included an electric heater element in the head of 
the dental syringe which keeps the head warm. The shortcoming of this 
design is that only the initial squirt of water discharged from the 
syringe is warm, having stood in the head a sufficient length of time to 
be pre-heated to the desired temperature. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a dental syringe 
adapted to pre-heat water from a supply hose before it is delivered 
through the syringe tip into a patient's mouth. 
It is another object of the present invention to provide a dental syringe 
handle including a water chamber having heater and thermostat elements 
mounted therein. 
It is yet another object of the present invention to provide a warm water 
dental syringe which will discharge water at a temperature of from about 
95.degree. F. to about 105.degree. F. 
It is still another object of the present invention to provide a dental 
syringe adapted to pre-heat air from a supply hose before it is delivered 
through the syringe tip into a patient's mouth. 
The present invention provides a warm water dental syringe including a 
head, a tip extending from the head, and handle means extending from the 
head. The head has a water passage therethrough which communicates with a 
water passage through the tip. The handle means includes a water chamber 
which communicates with the water passage through the head. An electric 
heater element heats water in the chamber. The handle means further 
includes connecting means for attaching a water supply hose so that water 
can flow therefrom into the chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, the illustrated embodiment of a warm water dental 
syringe constructed in accordance with the present invention includes a 
head 10, a handle 12 coupled to the head, and elongate tip 14, and a 
coupling 16 for mounting the tip on the head. A flexible tube 18 encloses 
a water supply hose 20, an air supply hose 22, and electric wires 24 which 
are connected to the lower end of the handle 12. 
Water and air are supplied from the hoses 20 and 22, through the handle 12 
in which the water is heated, to water and air connector pipes 26 and 28 
at the upper end of the handle as will be described. The connector pipes 
26 and 28 are inserted into water and air passages 30 and 32 (FIG. 2) in 
an externally threaded shank 34 (FIG. 1) at the bottom of the head 10. The 
water and air passages 30 and 32 extend from the end of the shank 34 
through the head 10 to an internally threaded cylindrical cavity (not 
shown) in the top frontal surfaces of the head in which the coupling 16 is 
suitably secured as, for example, in the manner shown in co-pending 
application Ser. No. 974,366. 
The tip 14 (FIG. 1) comprises inner and outer elongate, co-axial spaced 
apart pipes which define water and air passages which communicate with the 
water and air passages 30 and 32 respectively through the head 10 in the 
manner also described in co-pending application Ser. No. 974,366. Push 
buttons 36 and 38 on the top rear surface of the head 10 are coupled to 
suitable, normally closed valves (not shown) mounted in the water and air 
passages 30 and 32 so as to be selectively handoperated in order to 
discharge water, air, or both through the distal end 40 of the tip 14. 
Referring to FIG. 1, the handle 12 includes an outer elongate cylindrical 
tube 42 adapted to be grasped by the user's hand. The tube 42 has upper 
and lower ends in the form of cylindrical plugs 46 and 48 (FIG. 5) which 
fit tightly into the ends of the tube. The interior bore of the tube 
between the plugs 46 and 48 defines a water chamber 49. Sealant such as 
solder may be applied to the plugs to ensure a leak-proof water chamber. 
The tube 42 is preferably formed from brass tubing having an inside 
diameter of nearly three-quarters of an inch. The length of the water 
chamber 49 is approximately three and five-eighths inches. The volume of 
the water chamber is large enough, after subtracting the volume of the 
hereafter described elements mounted therein, to allow numerous successive 
squirts of heated water to be discharged through the tip. 
As shown in FIG. 5, the lower plug is provided with connecting means for 
attaching the water and air supply hoses 20 and 22. Side-by-side water and 
air passages 50 and 52 extend through the lower plug 48. Tubular water and 
air supply barbs 54 and 56 are tightly fit into the lower ends of the 
water and air passages 50 and 52 respectively. The water and air supply 
hoses 20 and 22 are tightly fit over the supply barbs 54 and 56 
respectively (FIG. 1). The lower portion of the plug 48 is externally 
threaded and an internally threaded ring 58 attached to the hose 18 is 
screwed over the plug 48 to shield the supply hose and electric wire 
connections. 
The upper plug 46 (FIG. 5) is provided with coupling means for releasably 
securing the upper end of the handle 12 to the shank 34 of the head 10. 
Side-by-side water and air passages 60 and 62 extend through the upper 
plug 46. The air passage 62 is formed by drilling slightly offset upper 
and lower holes 62a and 62b partially into opposite ends of the plug 46 so 
that they meet. The water and air connector pipes 26 and 28 are tightly 
fit into the upper ends of the water and air passages 60 and 62 
respectively. The upper and lower ends of an air conduit pipe 64 inside 
the water chamber 49 are tightly fit into the air passages 62 and 52 
respectively. The pipe 64 has a bend in its intermediate portion so that 
it clears the casing of the thermostat later described. Air from the 
supply hose 22 can thus be delivered directly through the handle 12 to the 
syringe head 10. Heat from the water inside the chamber is conducted 
through the pipe 64 and warms the air therein. 
The upper portion of the upper plug 46 has an annular groove 66 in its 
outer periphery. A conventional slip ring 68 having a segment missing from 
its body is expanded and slid over the upper plug 46 until it seats in the 
groove 66. Thereafter a tubular sleeve 70 having an annular groove 71 in 
its inner surface is slid over the upper plug 46 and the slip ring 68 by 
slightly compressing the slip ring. When the slip ring 68 seats in the 
groove 72 in the sleeve it slightly expands to lock the sleeve in position 
about the upper plug 46. The sleeve 70 has internal threads 74 adapted to 
be threadedly engaged with the external threads on the shank 34 of the 
head 10. 
The handle 12 and the shank 34 must be aligned so that the connector pipes 
26 and 28 (FIGS. 1, 3 and 5) will be received in the passages 30 and 32 
(FIG. 2) in the shank. Elastomeric O-rings 76 (FIGS. 3 and 5) surround the 
connector pipes 26 and 28 and are seated in annular cavities 77 formed in 
the plug 46. The O-rings 76 are squeezed between the upper plug 46 and the 
shank 34 to provide water and air seals. 
Referring to FIGS. 1, 4 and 5, an electric heater element of the resistance 
type is mounted inside an elongate cylindrical casing 78 mounted within 
the water chamber 49. The lower end of the casing 78 is tightly fit into 
and extends through a mounting hole 79 (shown in phantom lines in FIG. 5) 
which extends through the lower plug 48 on the side thereof opposite from 
the water passage 50. Preferably the casing 78 is formed from copper 
tubing and extends axially within the tube 42 over substantially the 
entire length of the water chamber 49 so that the water within the chamber 
can be heated more uniformly. 
An electrical thermostat of the bi-metal type is mounted inside an elongate 
cylindrical casing 80 (FIGS. 1, 4 and 5) also mounted within the water 
chamber 49. The casing 80 is also preferably formed from copper tubing. 
The lower end of the casing 80 is tightly fit into and extends through a 
mounting hole 81 (shown in phantom lines in FIG. 5) which extends through 
the lower plug 48 on the side thereof opposite from the air passage 52. 
The casing 80 is spaced from the casing 78 so that the thermostat 
contained therein will monitor the water temperature within the chamber 49 
rather than the temperature of the casing 78. The electric wires 24 are 
connected to the heater and thermostat elements within the casing 78 and 
80 and extend from the lower ends of the casings. 
FIG. 6 shows an example of a simple electric circuit for the warm water 
dental syringe of the present invention which will accomplish the desired 
regulation of the temperature of the water within the chamber 49. A 120 
volt AC electric power source is connected to the primary leads of a 
transformer 82 which steps the voltage down to 24 volts. A bi-metal 
thermostat 84 (inside the casing 80) and a heater element 86 (inside the 
casing 78) are connected in series to the secondary winding of the 
transformer 82. 
In operation, when the heater element 86 is energized it heats the water 
within the chamber 49 until the water has been heated to the upper 
temperature limit of the thermostat 84. At this time the thermostat 84, 
which functions as a temperature sensitive switch, opens. The heater 
element 86 is de-energized and the water within the chamber 49 cools until 
the lower temperature limit of the thermostat 84 is reached. At this time 
the thermostat 84 closes, energizing the heater element 86 which heats the 
water within the chamber 49 until the upper temperature limit of the 
thermostat 84 is once again reached. In this manner, the temperature of 
the water within the chamber 49 is regulated so that it is always between 
the upper and lower temperature limits of the thermostat. 
It is preferred to deliver water through the dental syringe at body 
temperature, i.e. 98.6.degree. F. However, due to the nature of the 
circuit, the temperature of the water within the chamber must necessarily 
fluctuate above and below this desired temperature. It is preferable to 
use a thermostat element with upper and lower temperature limits near 
98.6.degree. F. However, thermostats which can detect very small 
variations in temperature are typically more expensive. Therefore, it is 
acceptable to use a thermostat element which will maintain the temperature 
of the water within the chamber at from about 95.degree. F. to about 
105.degree. F. 
From the foregoing, it will be apparent that the invention permits of 
modification in arrangement and detail. For example, the tip and the 
handle can be integrally formed to the head. The tube 42 defining the 
water chamber 49 can have a layer of thermal insulation material. Various 
types of thermostats may be used, e.g. one made of a material having a 
negative coefficient of resistance. However, such adaptations and 
modifications, as well as others, are within the spirit and scope of the 
present invention.