Water injection type dental handpiece

A center injection type dental handpiece contains a cutting bar having a hollow axially penetrating the bar, holding means for detachably holding the bar, rotating means for rotating the bar, a water injection nozzle communicating with a cooling water feed source. The water injection nozzle is inserted into the hollow of the bar for injecting a cooling water from tip of the bar. The handpiece further contains a packing for sealing a gap between the outer periphery of the nozzle and the inner periphery of the bar at the proximal end of the bar.

BACKGROUND OF THE INVENTION 
The present invention relates to a water injection type dental handpiece, 
and more particularly to a water injection type dental handpiece capable 
of injecting water through a central bore in a cutting burr which can be 
used for dental implant or the like. 
A water injection type handpiece has hitherto been used for drilling and 
tapping a tooth in dental implantation. In such a prior art handpiece, as 
shown in FIG. 3, a cutting burr 1 such as a drill having a bore 2 axially 
extending in the center thereof is detachably secured in a head 10 and 
rotated. A water injection nozzle 20 communicating with a cooling water 
feed source (not shown) is inserted into the bore 2 from the proximal end 
1' of the burr 1, so that the cooling water can be injected into a cutting 
site through an injection port 2' at the distal end 1" of the burr 1. 
In such a conventional water injection type handpiece, however, when the 
injection port 2' of the burr 1 abuts the cutting site and blocked, the 
cooling water flows in a reverse direction through a small gap between the 
outer surface 10' of the injection nozzle 20 and the inner surface of the 
bore 2, and leaks out of the burr 1 into the interior of the head 10. Such 
water leakage may have an adverse effect on bearings 16, or may generate 
rust on internal parts such as a gear 15. As a result, cutting efficiency 
and durability of the handpiece may be lowered. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a water 
injection type dental handpiece wherein leakage of cooling water from the 
proximal end of the burr into the interior of the head is prevented. 
The present invention provides an improvement over conventional water 
injection type handpiece 5 wherein a water injection nozzle communicating 
with a cooling water feed source is inserted into a bore in a burr for 
injecting water through the distal end of the burr. 
Toward the fulfillment of the above and other objects, according to the 
present invention, there is provided a water injection type dental 
handpiece, which comprises a cutting burr having proximal and distal ends 
and an outer surface and further having a bore axially extending through 
the burr. The bore is provided with an inner surface and proximal and 
distal opening at the proximal and distal ends of the burr. Means are 
provided for detachably holding the burr and for rotating the burr. The 
means for detachably holding the burr includes a push-button having an 
opening with an edge. 
The present invention further includes a water injection nozzle having two 
ends and an outer surface. The nozzle communicates with a cooling water 
feed source at one end and extends into and communicates at the other end 
with the above-noted bore in the burr through the proximal opening of the 
bore for transmitting cooling water from the feed source to the bore in 
the burr. The invention further includes packing for sealing a gap between 
the outer surface of the nozzle and the inner surface of the burr at the 
proximal end of the burr, the packing surface having a groove mating with 
the edge of the opening in the push-button for sealingly fitting within 
the opening in the push-button.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a sectional view of a head 10 of a water injection type dental 
handpiece I of the invention. Same parts as in FIG. 3 are identified with 
the same reference numerals. 
The handpiece I is a contra angle handpiece of a push type, wherein cutting 
burr 1 (schematically shown) of a latch type is detachably held and 
rotated in head 10. The cutting burr 1 has bore 2 extending in the axial 
direction of the burr 1 in the center thereof, into which water injection 
nozzle 20 to be described later is inserted for transmitting cooling water 
to the distal end of the burr. Notch 3 and detent groove 4 are provided 
near the proximal end of burr 1. 
The head 10 has housing 11, which contains burr tube 13, chuck device 14, 
gear 15, and upper and lower ball bearings 16. The burr tube 13 receives 
burr 1 therein for unrotatably holding the burr in cooperation with notch 
3 on burr 1. The chuck device 14 includes latch plate 14' biased radially 
inwardly by a spring (not shown) into engagement with detent groove 4 on 
burr 1 for securing burr 1 in place. The gear 15 is fixed on the outer 
surface of burr tube 13 in the lower (distal) portion thereof and driven 
by a motor (not shown) to rotate the burr tube with burr 1. The upper and 
lower ball bearings 16 rotatably support burr tube 13 and gear 15. 
The head cap 12 is screwed onto head housing 11, and provided with 
push-button 17 which is biased upwardly by spring 18. By pushing button 17 
downwardly, latch plate 14' of chuck device 14 is moved radially outwardly 
and opened, and burr 1 is released from chuck device 14. 
The push-button 17 has opening 17' through which water injection nozzle 20 
is extended as will be described later. Also placed in opening 17' is 
packing 30 for sealing a gap between the edge of opening 17' and the outer 
surface of nozzle 20 as will be described below. 
As shown in FIG. 2, packing 30 has a bore 31 through which injection nozzle 
20 is extended. On the outer surface of packing 30, annular groove 32 is 
provided which mates with the edge of opening 17' in push-button 17 for 
sealing the gap between the edge of opening 17' and outer surface 20' of 
nozzle 20. The lower portion 33 of packing 30 below groove 32 has a 
downwardly tapered surface for sealing the gap between outer surface 20' 
of nozzle 20 and the inner surface of bore 2 in the burr 1 at the proximal 
end of burr 1. 
The packing 30 is made of an elastic material, so that it can easily be 
attached to and detached from opening 17' in push-button 17. Preferred 
examples of the elastic material may include nitrile rubber, silicone 
rubber, and fluororubber. 
Water injection nozzle 20 communicates with a cooling water source (not 
shown) for transmitting cooling water from the source to the interior of 
the bore in the burr. Nozzle 20 is extended through bore 31 in the packing 
30 fit in opening 17' in push-button 17, and then further extended into 
bore 2 in burr 1 for transmitting cooling water to distal end 1" of the 
burr 1 for injection through the injection port 2'. 
According to the present invention, lower portion 33 of packing 30 seals 
the gap between outer surface 20' of injection nozzle 20 and inner surface 
of bore 2 in burr 1 at the proximal end 1' of burr 1 with a slight 
pressure. Therefore, even if injection port 2' at distal end 1" of burr 1 
is blocked, the resulting pressure is not released from proximal end 1' of 
burr 1. Accordingly, gap 40 between outer surface 20' of the injection 
nozzle 20 and inner surface of bore 2 in burr 1 will not serve as a 
leakage path for the cooling water, and thus the leakage of the cooling 
water into the interior of the head 10 is prevented. 
Further, since the handpiece I of the water injection type is intended for 
use in tapping operation, the rotational speed of burr 1 is low, so that 
the packing 30 in contact with the burr 1 is hardly worn due to friction 
between proximal end 1' of the burr and packing 30. 
Although the present invention has been described with reference to the 
preferred embodiment, it should be understood that various modifications 
and variations can be easily made by those skilled in the art without 
departing from the spirit of the invention. Accordingly, the foregoing 
disclosure should be interpreted as illustrative only and is not to be 
interpreted in a limiting sense. The present invention is limited only by 
the scope of the following claims.