Dental prophy cup having a microcellular polishing surface and method of making

A dental prophy cup includes a polishing surface formed by a plurality of annular ridges spaced along a longitudinal axis of rotation of the prophy cup. Each ridge includes a generally forwardly facing side which has a micro-cellular texturing capable of retaining abrasive paste. The cup is molded of a solid elastomeric material in a mold which forms the micro-cellular texturing on the polishing surface.

BACKGROUND OF THE INVENTION 
The present invention relates to a dental prophy cup used in dental 
prophylaxis procedures and, in particular, to a novel configuration and 
construction of such a cup, as well as to a method of making a dental 
prophy cup. 
A dental prophylaxis procedure typically involves the application of an 
abrasive paste (i.e., a paste containing abrasive particles) to a tooth 
surface upon which pressure and rotational motion are applied. The removal 
of plaque, calculus and stains is facilitated by the resultant abrasion at 
the interface between the abrasive particles and tooth surface. 
The pressure and rotational motion are applied to the abrasive paste by 
means of a prophy cup which comprises an elastic cup-shaped element of 
about one-quarter inch diameter. A rear portion of the cup is mounted on a 
drive shaft which rotates the cup at high speed, e.g., about 1500 rpm. The 
front portion of the cup forms an internal cavity which receives the 
paste. The wall of the cavity may include a plurality of fins extending in 
a front-to-rear direction. An operator presses the front portion of the 
cup against a tooth following the insertion of abrasive paste into the 
cavity. The paste serves as a lubricant, and the abrasives in the paste 
function to abrade away plaque, calculus, and stains from the tooth 
surfaces. 
This procedure has traditionally exhibited certain shortcomings. For 
example, the centrifugal force generated by a prophy cup rotating at 1500 
rpm causes the paste to be displaced from the cavity. Since the surface of 
the cup which engages the tooth is smooth, only minimum resistance to the 
displacement of the paste is presented. The displacement of paste results 
in reduced abrasion and cleaning performance. 
Also, abrasive particles of the paste disposed between the smooth cup 
surface and the tooth surface can produce excessive scratching of the 
tooth surface. 
Disclosed in U.S. Pat. Nos. 5,078,754 and 5,369,916 is a dental prophy cup 
formed of a polyurethane foam wherein the foaming process creates air 
pockets or voids throughout the foam and at the cup surface. The pockets 
at the cup surface would inherently form a texturing capable of retaining 
abrasive paste, and more effectively resisting outward displacement of the 
paste better than a smooth surface. However, due to the presence of air 
pockets throughout the foam, the cup would not be firm enough, i.e., it 
would be too pliable to transmit sufficient pressure to the teeth. 
Therefore, it would be desirable to provide a dental prophy cup which 
increases the residence time of abrasive paste therein, while being 
capable of transmitting sufficient pressure to the teeth, without 
producing excessive scratching of the teeth. 
SUMMARY OF THE INVENTION 
These and other objects are achieved by the present invention which relates 
to a dental prophy cup comprising a body having a rear mounting portion 
and a front polishing portion formed of one piece with the mounting 
portion. The mounting portion is adapted to be mounted on a handpiece for 
rotation about a longitudinal center axis of the body. The polishing 
portion includes a front surface forming a forwardly open center cavity 
for receiving abrasive paste. The body is formed of a solid elastomeric 
material, whereby the polishing portion is elastically flexible in 
response to being pressed against a tooth to enable the front surface to 
generally conform to a contour of the tooth. The front surface possesses a 
micro-cellular structure for retaining abrasive paste during a 
tooth-polishing operation. 
Preferably, the micro-cellular texture of the front surface is defined by 
generally semi-spherical cells, each cell having a radius in the range of 
about 80 to 300 microns. 
The front is surface preferably comprised of a plurality of annular ridges 
spaced along the center axis. The ridges are of progressively larger 
radius toward a front end of the cavity. Each ridge includes a generally 
forwardly facing side possessing the micro-cellular texturing.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION 
Depicted in FIGS. 1-4 and 6 is a dental prophy cup comprising a body 10 
having a rear mounting portion 12 and a front polishing portion 14. The 
mounting portion includes a recess 16 adapted to be attached to a 
conventional handpiece (not shown) for rotation about a longitudinal axis 
A of the body (see FIG. 6). 
The polishing portion 14 includes a front surface 18 forming a forwardly 
open center cavity 19 for receiving abrasive paste. The body 10 is formed 
of a solid elastomeric material, preferably polyisoprene having a 
durometer value of 55-75, so that the polishing portion is elastically 
flexible in response to being pressed against a tooth, to enable the front 
surface 18 to flex and generally conform to a contour of the tooth. 
The front surface 18 has a microcellular texture so as to be capable of 
retaining abrasive paste and resist outward displacement thereof. Yet, 
because the body 10 is formed of a solid elastomeric material instead of, 
for example, a foamed elastomeric material, the polishing surface is able 
to transmit sufficient pressure to the tooth surface. 
The texturing is formed by microcells of generally semi-spherical shape, 
although other cell shapes are possible. Alternatively, the microcellular 
texturing could be formed by tiny, short, spaced-apart fingers (not shown) 
which project forwardly from the front surface. 
The cup is made by a flashless molding process in which a face 20 of a mold 
22 which forms the microcellular textured tooth engaging surface of the 
cup is itself textured as shown in FIG. 5. That is, the face 20 is 
provided with generally semi-spherical bumps 24 each having a radius in 
the range of about 140 microns (0.0055 inch). 
The bumps 24 are arranged in annular rows, each row being coaxial with a 
longitudinal center axis of the mold cavity C. The bumps of each row are 
spaced apart by about 0.001 to 0.002 inches, although the bumps could 
instead be arranged in immediate contact with one another. The rows of 
bumps disposed nearest to the front end of the mold cavity C are spaced 
apart by a larger distance than are the rows spaced farther from that 
forward end. For example, the front rows are spaced apart by a distance x 
of about 0.0030 inch, whereas the remaining rows are spaced apart by 
distance y of about 0.0020 inch. 
When elastomeric material is injected into the mold cavity C and becomes 
hardened, a cup will be formed wherein the front surface 18 has cells or 
pores 30 corresponding in size and location to the bumps 24. Thus, the 
cell 30 are of generally semi-spherical shape, each with a radius is in 
the range of about 80 to 300 microns, preferably about 140 microns (about 
0.0055 inch). 
The front surface 18 is comprised of a plurality of annular ridges 32A, 
32B, 32C arranged coaxially with respect to the axis A. The ridges are of 
larger diameter in a direction toward the front end of the cavity 19. Each 
ridge includes a generally forwardly facing side 34A, 34B, 34C in which 
the cells 30 are formed in annular rows. Each cell includes an outer edge 
40 lying flush with the front surface 18. That is, an imaginary plane 
(FIG. 6) extending perpendicular to the center axis A intersects the front 
surface 18 and a plurality of cells disposed therein. The entire portion 
of the front surface 18 that is intersected by the plane (i.e., the 
portion of surface 18 extending from one intersected cell to another) is 
spaced at a constant distance from the center axis (the distance being 
measured in a direction perpendicular to the axis A). The cells 30 in each 
row are spaced apart by about 0.001 to 0.002 inch, although if the bumps 
24 were in immediate contact with one another, there would be no spacing 
between the cells. The rows of cells located in the front side 34C of the 
ridge 32C are spaced apart by the distance x of about 0.0030, whereas the 
remaining rows of cells in the sides 34A and 34B are spaced apart by the 
distance y of about 0.0020 inch. 
The overall height H of the cup is about 0.3277 inch, and the front 
diameter D of the polishing portion is about 0.25 inch. 
The bumps 24 are preferably formed in the mold face 20 by a conventional 
photochemical machining process for precision material removal. In that 
process, resists are used to copy an image from a mask or pattern 
generator onto the mold surface. The surface is covered by a thin layer of 
the resist which is a radiation-sensitive material. This material is then 
selectively exposed to radiation and the image is thus copied into the 
resist, which is later developed by removing the portions of the resist 
that were made more soluble when exposed to the radiation (e.g., electron 
or x-ray irradiation). 
Other methods for forming bumps 24 on the mold surface 20 might be 
practicable, such as flame spraying steel beads onto a smooth mold 
surface, or possibly by the use of CNS or EDM machining. 
In use of the cup, the abrasive paste is inserted into the cavity 19, and 
the cup is pressed against a tooth surface with sufficient force (e.g., 
0.5 lb) to elastically flex the front surface 18 into general conformance 
with the contour of the tooth surface. As the cup is rotated, the paste 
produces a polishing action against the tooth surface to remove plaque, 
calculus, and stains. Any tendency for the paste to be displaced outwardly 
by centrifugal force is resisted, because the paste is retained in the 
cells 30 of the front surface 18. Also, abrasive particles disposed within 
the cells have less of a tendency to excessively scratch the tooth surface 
as compared to the case where particles are disposed between a smooth 
(non-textured) cup surface and the tooth surface. 
Importantly, since the cup is formed of a solid (non-foamed) elastomeric 
material, the cup possesses a sufficient modulus of elasticity to transmit 
the requisite pressure against the tooth surface. 
Although the present invention has been described in connection with a 
preferred embodiment thereof, it will be appreciated by those skill in the 
art that additions, deletions, modifications, and substitutions not 
specifically described may be made without departing from the spirit and 
scope of the invention as defined in the appended claims.