Dental syringe safety sheath apparatus

The present invention comprises a sheath for protecting a dental syringe and for preventing residual cross-contamination between successive patients. Means are provided for preventing contaminants from being drawn back into the syringe after application has ceased.

TECHNICAL FIELD 
This invention relates to a dental syringe safety sheath apparatus adapted 
to minimize residual cross-contamination between patients. More 
specifically, the present invention relates to a disposable safety sheath 
which may be placed over the beak of a dental syringe used to apply a 
fluid to the inside of a patient's mouth. 
BACKGROUND ART 
The problem of residual cross-contamination between patients is of serious 
concern to the public and dental profession. This problem has received 
considerable attention due to the publicity of many known illnesses and 
diseases which may be communicated by the transfer of infected body fluids 
between patients. A dental syringe is often used to apply a suction or 
fluid, such as water or air, to the inside of a patient's mouth. Where a 
fluid is dispensed, the syringe is connected to a pressurized delivery 
system. In some dental syringe systems, an optional draw-back apparatus 
may be used with the delivery system. When the application of a liquid 
ceases, the draw-back apparatus produces a partial vacuum within the 
delivery lines, syringe and beak. The partial vacuum draws the liquid 
located within the syringe back into the delivery system, removing the 
liquid from the beak of the syringe. The draw-back apparatus prevents the 
leaking or dripping of liquid from the discharge orifice of the beak when 
the syringe is not used. Unfortunately, when the syringe is released from 
dispensing the liquid, the draw-back apparatus may suck contaminants, such 
as germs, blood, or saliva, from within the patient's mouth into the 
syringe or delivery system. These contaminants remain within the syringe 
or delivery system until liquid is subsequently dispensed, possibly into 
another patient's mouth. 
Devices using sanitary covers have been designed in an effort to reduce the 
occurrence of injuries caused by dental hardware. 
Curry (U.S. Pat. No. 1,485,963) discloses a disposable cover for a dental 
handpiece. The cover protects the handpiece from contacting the hand of 
the user or the mouth of the patient. 
Fehrman (U.S. Pat. No. 2,655,725) discloses a grinding implement for use 
with small animals, particularly chinchillas, having a readily adjustable 
guard for the rotary burr to protect the mouth of the animal against 
injury. 
Ikse (U.S. Pat. No. 2,696,669) discloses a device for supplying liquid 
during dental operations. Ikse ('669) teaches that the nozzle may be 
interchangeable. 
Hawk (U.S. Pat. No. 4,286,950) discloses a removable cover for a dental 
handpiece, to protect the tool and enclose it when not in use. 
These disclosures are believed to illustrate the general scope of the prior 
art in this area of dental technology. The applicant submits that these 
disclosures taken alone or together do not teach the concepts embodied in 
this invention. 
DISCLOSURE OF INVENTION 
It is the general object of the present invention to provide an apparatus 
which helps reduce residual cross-contamination between dental patients. 
A further object is to provide an apparatus to cover and protect the beak 
of a dental syringe. 
A still further object is to provide an apparatus which substantially 
prevents contaminants from being drawn through the discharge orifice into 
the beak of a syringe. 
Another object is to provide an apparatus which is removable and disposable 
after use with each patient, thereby minimizing the need to sterilize the 
beak of the syringe after each use, although, periodic sterilization is 
advisable. 
Another object of the invention is to provide a sheath that can be readily 
engaged with, and disengaged from, the beak of a dental syringe. 
Another object of the invention is to provide a plastic, relatively stiff 
cap-type cover or sheath to protect the syringe, and enclose the beak's 
discharge orifice when fluid is not being discharged. 
The present invention is a dental syringe safety sheath apparatus which 
acts as a protective cover for those portions of a beak of a dental 
syringe which will be used near or be inserted into a patient's mouth. The 
safety sheath apparatus provides a substantially sterile outer-covering 
for the beak and may be disposable after use with each dental patient. 
The safety sheath apparatus has a sheath means, cover, or sleeve into which 
the beak of a dental syringe may be inserted. The sheath means is a 
generally elongated tube or cylinder adapted to substantially fit over and 
cover the beak of a dental syringe from the syringe handpiece to the 
beak's discharge orifice. The sheath is appropriately dimensioned to allow 
for proper, secure fitting on the beak and for easy removal. The sheath 
means is removably attached to the beak and is preferably form fitted to 
the shape of the dental beak. Where the beak has a defined axis, the 
sheath means is positioned coaxially with the axis of the beak. The sheath 
means has an open-end and a terminal-end. An opening in the open-end is 
sufficiently large to allow for the insertion of the beak into the sheath 
means. The terminal-end has an aperture, located near the discharge 
orifice of the beak, which allows fluid to be dispensed from the beak and 
sheath means into a dental patient's mouth. 
A tip may be used independently or with the sheath means. The tip is 
removably attached to the terminal-end of the sheath means. Alternatively, 
the tip is an integral part of the terminal end of the sheath means. The 
tip covers the discharge orifice of the beak. When used together, the tip 
and sheath means provide a substantially sterile outer-covering for the 
beak and discharge orifice. 
The tip has a small, movable valve means positioned near the aperture of 
the sheath means, coincidently with the discharge orifice of the beak. 
When open, the valve means allows a fluid to be dispensed from the beak 
and tip. The valve means closes to cover the aperture when the syringe is 
not being used. The purpose of the valve means is to close or cover the 
aperture when the fluid is no longer being dispensed, thereby, 
substantially preventing contaminants, such as the patient's body fluids, 
from entering or being drawn into the beak through the discharge orifice. 
The valve means may be a flap-valve, hinged to the tip and made of material 
wherein the natural flexible properties of the material allow the 
flap-valve to be at least partially open when the pressure within the beak 
exceeds atmospheric pressure and the fluid is forced outward from the 
discharge orifice. The resiliency of the flexible material urges the 
flap-valve to be at least partially closed when the pressure within the 
beak approaches atmospheric pressure and the fluid no longer is forced 
outward from the discharge orifice. Alternative valve systems may also be 
used if the same effect is substantially achieved. 
The sheath of this invention may extend over the enlarged portion of beak 
having internal threads for attachment to the base of the dental syringe 
to provide more complete coverage of the instrument. 
Another embodiment of this invention utilizes a replaceable beak structure 
in place of the metal beak normally found in a dental syringe. Desirably, 
this replacement beak has an internal valve mechanism to prevent 
aspiration of the fluids back into the syringe. The structure may also be 
provided with an external valving mechanism as described above. 
A drape or sleeve made of a thin flexible material may be provided to cover 
the entire dental syringe extending backwardly from the sheath over the 
body of the syringe. A flexible or flexible and stretchable material may 
be used for this purpose to completely enclose the syringe device. 
Replacement of the sheath and tip with a new sheath and tip after use with 
each patent greatly reduces the possibility of residual 
cross-contamination of body fluids between dental patients. Although 
periodic sterilization of the beak of the syringe may still be advisable 
for absolute safety, the need for sterilization is greatly reduced. 
An alternative embodiment of the present invention encompasses a small, 
movable valve means which is integrally or removably attached to a 
disposable beak. In such an embodiment, the valve means is located 
coincidently with the discharge orifice of the beak and similarly 
functions as described above.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring to the drawings and particularly to FIGS. 1-4, wherein like 
numerals indicate like parts, the dental syringe safety sheath apparatus 
20 comprises a sheath means 26 for sheathing beak 22 of a dental syringe 
24. The sheath means 26 may take the form of a sheath, cover, or sleeve 
into which beak 22 may be inserted. 
Sheath means 26 may be held onto beak 22 and syringe 24 by any conventional 
means which allows relatively easy placement and removal. Sheath means 26 
should not be so loose when attached to beak 22 as to cause a danger of 
falling off beak 22 into the patient's mouth. Sheath means 26 is 
preferably a generally elongated cylinder, form fitted to the shape of 
beak 22, and adapted to substantially fit over and cover beak 22 from 
handpiece 27 to discharge orifice 31. A close fitting between sheath means 
26 and beak 22 also minimizes the amount of contaminants which might 
become entrapped therebetween. 
Sheath means 26 has an open-end 28 and a terminal-end 29. Terminal-end 29 
has an aperture 30 located coincident or near the discharge orifice 31 of 
beak 22. In FIG. 3 the aperture is indicated by a cross-slit 130. 
Cross-slit 130 comprises a single or double incision through sheath means 
26. A double incision forming an x-shape is shown. In FIG. 4 the aperture 
is indicated by an opening 230 which is covered by a hinged valve means 
234. Sheath means 26 is shown in FIG. 5 as having an aperture 330 into 
which a tip 32 is inserted. Tip 32 is juxtaposed between terminal-end 29 
of sheath means 26 and beak 22 near discharge orifice 31. Apertures 30, 
130, 230 and 330 enable the fluid being discharged from dental syringe 24 
to pass into the patient's mouth without excessive pressure being built up 
between beak 22 and sheath means 26. 
These embodiments may incorporate the use of tip 32 and/or a valve means 
wherein apertures 30, 130, 230 or 330 allow a fluid to be dispensed from 
beak 22, but prevent contaminants from entering into discharge orifice 31 
when application of the fluid ceases. The valve means may comprise a 
flap-valve which is only open when the pressure within beak 22 exceeds 
atmospheric pressure and the fluid is forced outward from discharge 
orifice 31. 
The valve means and sheath means 26 may be made of material wherein the 
natural flexible action of the material allows the valve means to open 
when fluid is forced outward from beak 22, and close when the discharge of 
fluid ceases. 
As shown in FIG. 5, tip 32 may comprise a separate device, having valve 
means 334 incorporated therein. Tip 32 attaches or snaps onto terminal-end 
29 of sheath 26. Alternatively, valve means 134 and 234 may be formed as 
an integral part of sheath means 26 as respectively shown in FIG. 3 and 
FIG. 4. In FIG. 3, the valve means comprises the remaining flaps 134 which 
were formed by cross-slit 130. In FIG. 4, the valve means comprises the 
remaining flap 234 which is formed by a semicircular incision creating 
aperture or opening 230. Valve means 234 and 334 comprising a flap-valve 
are shown in FIG. 4 and FIG. 5 respectively. Valve means 234 is shown 
closed in FIG. 4. Valve means 334 is shown open in FIG. 5. 
For a more complete coverage of the beak mechanism of this apparatus the 
embodiment shown in FIG. 6 is provided to encompass the knurled region 29 
of beak 22. The sheath 50 has an enlarged portion 51 which snugly encases 
the tapered handpiece 27 and knurled region 40. Also shown in this 
embodiment is an internal ball-type valve mechanism shown best in FIG. 7 
which includes a ball 55 held within chamber 56 by retainer 57. Since the 
sheath 50 is made of an elastomeric material, ball 55 may be inserted by 
thrusting it axially into the interior of sheath 50 and snapping it past 
retainer 57 into chamber 56. The ball may then move from one end to the 
other of chamber 56 encountering at one end the embossments 58 which 
permits flow of water or air around the embossments 58 through channels 59 
as is best seen in FIG. 8. Whenever back flow occurs, the ball immediately 
travels against the exposed end of beak 22 at aperture 31 and seals there 
against preventing back flow. Alternatively, the device shown in FIG. 6 
may have any of the tip structures shown in FIGS. 2, 3, 4, 5, and 10. 
In the event a replaceable beak structure, as opposed to a covering, for 
the beak is desired, the apparatus shown in FIG. 9 may be utilized. The 
threaded outlet 71 of handpiece 54 is adapted to receive a female threaded 
portion 72 of the replaceable beak structure. As desired, a ball valve 
device may be incorporated within the structure as is shown in FIG. 9. 
Here ball 67 is adapted to seat against and seal aperture 73 preventing 
back flow of fluids into handpiece 54. The forward motion of the ball 67 
when fluid flow occurs is arrested at embossment 68 preventing further 
movement of the ball yet permitting flow of fluid therearound. Depressing 
valve controls 52 permits selected flow of air or water through the 
handpiece. 
In FIG. 10 a slide-on type end valve structure is shown which may be used 
with any of the previously described devices, as desired. An outer sheath 
75 is adapted to slide upon for example beak 62 and provides additional 
valving action in the event of aspiration of water by closure of flap 
valve 64. This device may be used singly or in combination with other of 
the valve mechanisms described above. 
Any of the sheaths or replaceable beaks described herein may also be 
equipped with a drape or flexible sleeve which may be unrolled from the 
beak area backwardly over the body of the syringe to fully encase the 
syringe in a disposable cover. The cover may be a latex rubber type 
material which is stretchable and tightly encases the handpiece or may be 
a drape of non extendible elastomeric film which merely drapes over the 
syringe body. The device shown in FIG. 11 shows drape 80 being extended 
over the top of syringe body 54 and downwardly so that the entire body of 
the syringe is covered. Drape 80 is attached at drape roll 81 to syringe 
cover sheath 20 at roll anchor 81. In FIG. 12 the sheath before attachment 
is shown with the stowed sleeve or drape 80 shown rolled up in roll 83 
prior to installation. Once beak 20 is installed, the drape or sleeve may 
be rolled backwardly over the top of syringe body 54 to fully encompass 
the syringe. Access to valve controls 52 is available by merely depressing 
valves 52 through the drape material. 
In compliance with the statute, the invention has been described in 
language generally specific to structural features. Since the means and 
construction herein disclosed comprise the preferred form of putting the 
invention into effect, it is to be understood the invention is not limited 
to the specific features shown herein. The invention is, therefore, 
claimed in any of its forms or modifications within the legitimate and 
valid scope of the appended claims, appropriately interpreted in 
accordance with the doctrine of equivalents. 
INDUSTRIAL APPLICABILITY 
This invention is particularly adapted for use by dental professionals on 
dental syringe equipment to minimize residual cross-contamination between 
patients. This invention comprises a disposable sheath which covers the 
beak of a conventional dental syringe. A tip may be provided with a valve 
means to allow for disbursement of a fluid from the beak into the 
patient's mouth, but prevent contaminants from being drawn into the 
syringe beak through the discharge orifice when the syringe no longer 
dispenses fluid.