WO1997009002A1

WO1997009002A1 - Dental prophy cup having a paste-distributing channel arrangement

Info

Publication number: WO1997009002A1
Application number: PCT/US1995/011411
Authority: WO
Inventors: Neil A. Rosenberg
Original assignee: Nar Inc.
Priority date: 1995-09-07
Filing date: 1995-09-07
Publication date: 1997-03-13
Also published as: JPH11512015A; AU4612796A

Abstract

A dental prophylactic cup (100) comprises a flexible body having a cavity (122) formed therein. A rear end of the cavity includes a paste reservoir (126) for storing an abrasive paste. Paste delivery channels extend forwardly from the reservoir and intersect front and rear circumferentially extending paste distribution channels (130, 132). Under the action of centrifugal force occurring during a tooth cleaning procedure, paste if fed forwardly along the delivery channels and is distributed within the distribution channels (130, 132). Between the channels is disposed a pattern of ridges (134, 136) capable of flexing relative to one another to conform to the shape of a tooth surface. A ratio (T2/T1) of a thickness (T2) of a mouth of the cavity to a minimal wall thickness (T1) at a forward-most paste distribution channel is in the range of 0.0 to 0.75. A ratio (T1/L) of the wall thickness (T1) to a length (L) of the cavity is in the range of 0.16 to 0.24.

Description

DENTAL PROPHY CUP HAVING A PASTE-DISTRIBUTING CHANNEL ARRANGEMENT

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.

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 a flexible 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 typically includes 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. In fact, the amount of paste retained at the interface between the cup and tooth surface after one second (25 rotations) is a small fraction of the initial volume. This diminishing of paste results in reduced abrasion and cleaning performance.

In U.S. Patent No. 5,360,339 the present inventor disclosed an improved prophy cup 10 depicted in FIGS. 1-3 wherein the internal cavity 22 is formed by a surface 24 in which there is formed a channel arrangement comprised of paste-delivery channels 28 extending forwardly from the rear portion of the cavity, and circumferentially extending paste-distribution channels 30 and 32 spaced rearwardly from a front end of the body. The paste- delivery channels intersect the paste-distribution channels such that paste is induced to flow along the channel arrangement under the urging of centrifugal force during rotation of the body. The paste is thereby retained within the cavity for an extended period, and is amply distributed within the cavity. The channel arrangement forms a network of rear and front ridges 34, 36. Each ridge has a tooth-engaging surface 38 or 40 which generally faces the axis of rotation when the cup is in a relaxed state.

In use, the cavity 22 is filled with an abrasive paste, the cup is pressed against a patient's tooth surface, and the cup is rotated (preferably at 1500-2000 rpm) . During the application of a normal (moderate) force to the cup (e.g., 0.5 pounds), the cup flexes sufficiently so that the tooth surface is contacted by the surfaces 40 of the front ridges 36 under moderate pressure, and possibly also by the surfaces 38 of the rear ridges 34 under higher pressure.

As the cup rotates, the abrasive paste compressed between the cup and tooth abrades away stains and adherent materials such as plaque and calculus. Centrifugal force causes the paste to travel radially outwardly, and thus longitudinally forwardly, due to the forwardly expanding shape of the cavity surface 24. Some of the paste disposed within the cavity is quickly expelled from the cup by the centrifugal force.

Gradually, replacement paste flows forwardly from a reservoir 26 along the paste-delivery channels 28 and enters the paste-distribution channels 30, 32 for circumferential distribution. Paste which reaches the front paste-distribution channel 32 is obstructed from further forward travel by a front wall 42 thereof. Accordingly, it is ensured that an ample amount of generally uniformly distributed paste resides in the cavity 22 for an extended period. Notwithstanding the improved paste distribution and retention performance achieved by that prophy cup, it may occur that, due to the enhanced flexibility of the cup produced by the presence of the paste-distribution channels, especially the forwardmost channel 32, when the cup is pressed against the tooth surface T, the front end 52 of the cup inverts, i.e., becomes deflected rearwardly as depicted in Fig. 3, even under moderate pressure. That tends to reduce the overall area of contact between the cup and the tooth surface, and undesirably prevents the outer edge from penetrating below the patient's gum line. Therefore, it is an object of the invention to provide a prophy cup of the type having paste delivery and distribution channels and whose outer edge does not invert when subjected to at least moderate pressure. Summary of the Invention

The present invention relates to a dental prophy cup comprising a body having a rear mounting portion adapted to be mounted on a rotary handpiece for rotation about a longitudinal axis of rotation, and a front tooth- engaging portion formed of an elastomeric material and including a cavity for receiving an abrasive paste. The cavity expands toward a front end of the body. The cavity is defined by a surface in which there is formed a channel arrangement comprised of a paste-delivery channel extending forwardly from a rear portion of the cavity, and a circumferentially extending paste-distribution channel spaced rearwardly from a front end of the body. The paste-delivery channel intersects the paste-distribution channel and terminates at the paste-distribution channel such that paste is induced to flow along the channel arrangement under the urging of centrifugal force during rotation of the body. A ratio (T1/T2) of the thickness (Tl) of a mouth of the cavity to a minimal thickness (T2) of a wall of the tooth-engaging portion at the paste-distribution channel is in the range zero to 0.75 and most preferably is about 0.36.

A ratio (Tl/L) wherein L is the length of the cavity is in the range 0.16 to 0.24 and most preferably is about 0.19. A ratio (Tl/R) wherein R is a radius of a mouth of the cavity is in the range 0.2 to 0.3 and most preferably is about 0.24.

A ratio of D/Tl is preferably less than one, where D is a distance extending from a point P on an external surface of the body to a line L' which L' extends parallel to the axis of rotation and passes through a radially outermost portion of a front end of the body; the point P lies on a bisector of the paste-distribution channel. More preferably, D/Tl is 0.25 to 0.75. A ratio of H/Tl is from 1.0 to 2.0 where H is a distance from the front end of the body to a plane C oriented perpendicular to the axis of rotation A and passing through the point P; the dimension H extends parallel to the axis of rotation A. Brief Description of the Drawings

The objects and advantages of the invention will become apparent from the following detailed description of a preferred embodiment thereof in connection with the accompanying drawings in which like numeral designate like elements and in which:

FIG. 1 is a front perspective view of a dental prophy cup disclosed in U.S. Patent No. 5,360,339 and whose outer edge may tend to invert during operation; FIG. 2 is a longitudinal sectional view taken through the cup of FIG. 1;

FIG. 3 is a schematic view depicting the undesired inversion of the outer edge of the prophy cup when placed under pressure; FIG. 4 is a longitudinal sectional view of an improved prophy cup according to the invention for preventing inversion of the outer edge;

FIG. 5 is an enlarged view of a portion of

FIG. 4; and FIGS. 6-8 are schematic views showing the flexing of the cup of FIG. 4 when placed under, light, moderate and heavy pressures, respectively.

Detailed Description of a Preferred Embodiment of the Invention A dental prophy cup 100 depicted in FIGS. 4-8 comprises a body formed of a highly flexible material, preferably polyisoprene. A rear mounting portion 112 of the cup is configured for being mounted to the drive shank of a rotary handpiece (not shown) by screwing, latching, or snap-on, as is conventional.

Projecting forwardly from the mounting portion 112 is a tooth-cleaning portion 120 which forms a cavity 122 configured to be symmetrical about a central axis of rotation of the cup. The cross-sectional area of the cavity expands toward the front of the cup. The cavity 122 is formed by an internal surface 124 which forms a paste reservoir 126 at a rear end of the cavity. Disposed in the surface 124 are four paste-delivery channels (not discemable in FIG. 3, but similar to those shown at 28 in FIG. 1) each extending longitudinally forwardly and radially outwardly from the paste reservoir 126, and two longitudinally spaced, circumferentially extending paste- distribution channels 130, 132. Those channels cooperate to form two sets of circumferentially extending ridges 134, 136. A rear set of the ridges 134 is situated longitudinally rearwardly from a front set of the ridges 136.

The paste-delivery channels 128 are forwardly divergent, whereby the front ridges 136 are longer than the rear ridges 134 in the circumferential direction. Also, the front ridges 136 are spaced farther from the axis of rotation than are the rear ridges 134 when the cup is in a relaxed (unflexed) condition. Thus, it will be appreciated that the paste-delivery channels 128 become progressively shallower toward their front ends.

The front paste-distribution channel 132 is circumferentially continuous, whereas the rear paste- distribution channel 130 is interrupted circumferentially by the paste-delivery channels. The paste-delivery channels 128 thus terminate at the front paste- distribution channel 132, and the front ends of the paste- delivery channels 128 are closed by a circumferentially continuous front wall 142 of the front paste-distribution channel 132.

Extending forwardly from the wall 142 is an outwardly flared surface 144 which terminates forwardly at the radially inner edge of a forwardly facing rim surface 146. An external surface of the cup body includes a cylindrical portion 152 extending rearwardly from a radially outer edge of the rim surface 146, and a concave radiused portion 154 extending from a rear end of the cylindrical portion 152 to a front end of a generally frusto-conical portion 156. The latter portion 156 narrows rearwardly toward an external surface of the mounting portion 12.

The afore-mentioned problem relating to a tendency for the outer end of the prophy cut to invert

(see FIG. 3) has been eliminated by a unique combination of structural features. The new configuration not only eliminates the inverting problem but does so in a manner which enables the cup to perform a subgingival operation, i.e., to penetrate and clean beneath the gum line.

In that regard, a ratio Tl/L of the minimum thickness Tl of the outermost paste distribution channel 130 to the length L of the cavity 122 has been almost doubled, i.e., has been increased from about 0.10 in the previous cup 10 (FIG. 1) to about 0.19 in the new cup 100 (FIG. 4) . Preferably the ratio Tl/L of the new cup 100 is in the range of 0.15 to 0.24.

Also, the ratio of thickness Tl to the radius R of the outer end of the prophy cup 100 has also been doubled, i.e., the ratio Tl/R of the new cup 100 is about 0.24, whereas the ratio Tl/R of the old cup 10 was about 0.125. Preferably the ratio Tl/R of the new cup 100 is in the range 0.2 to 0.3.

Furthermore, a distance D of the prophy cup is defined between a point P and a line L' which extends parallel to the center axis A and passes through a radially outermost edge of the rim surface 146. The point P is a point where a bisector B of the channel 132 intersects the external surface of the cup. The distance D extends perpendicular to the axis A. A dimension H is a distance from the plane of the rim surface 146 to a plane C which lies perpendicular to the axis A and passes through the point P. In the old cup 10, the distance D was greater than the thickness Tl, i.e., D/Tl was about 1.28. However, in the new cup 100, the distance D is less than the thickness Tl, and preferably is less than one- half that thickness. That is, the ratio D/Tl of the new cup is preferably in the range 0.25 to 0.75, and more preferably 0.35 to 0.6, and most preferably about 0.42. In the old cup the dimension H was more than two times the thickness Tl, i.e., H/Tl was about 2.66. However, in the new cup, the dimension H is between one and two times the thickness Tl. More preferably, the ratio H/Tl is 1.25 to 1.50 and most preferably is about 1.35.

In the old cup, the ratio D/H was about 0.48, but in the new cup, that ratio is preferably 0.25 to 0.35 and most preferably is about 0.31.

The increases in the ratios Tl/L and Tl/R have served to stiffen the body of the cleaning portion of the cup, and the reductions in the ratios D/Tl, H/Tl, and D/H have served to stiffen the front end of the cup, thereby resisting a tendency for the front end of the cup to invert as shown in Fig. 3. However, those changes by themselves might tend to inhibit the ability of the front outer edge of the cup to penetrate below the gum line to perform subgingival cleaning. Accordingly, the invention also involves a reduction in the ratio T2/T1, wherein T2 is the thickness of the outer edge 152 of the front end of the cup. That ratio T2/T1 has been reduced to about 0.36 in the new cup 100 from 1.38 in the old cup. Preferably, the ratio T2/T1 in the new cup is less than 1.0 and in the range zero (0.0) to 0.75. In the case where the ratio T2/T1 is zero, the external surface 156 intersects the rim surface 146 as shown in broken lines 170 in Fig. 5. The reduction in the ratio T2/T1 makes the very outer edge of the front end of the cup more flexible and of a size capable of penetrating below the gum line GL as depicted in Figs. 6-8. In use, the cavity 122 is filled with an abrasive paste, the cup is pressed against a patient's tooth surface, and the cup is rotated (preferably at 1500-2000 rpm) . During the application of a light force, only the front surface 144 contacts the tooth (see FIG. 6) . During the application of a normal (moderate) force to the cup, the tooth-cleaning portion 120 flexes to cause the circumferentially continuous front surface 144 and the surfaces 140 of the front ridges 136 to contact the tooth surface T which is from small to moderate curvature, as shown in FIG. 7. When engaging a tooth surface which is from moderate to severe curvature, a higher force is applied to the cup to further cause the surfaces 138 of the rear ridges 134 to also contact that tooth surface as shown in FIG. 8. In each case, the body of the tooth-cleaning portion 120 of the cup is sufficiently stiff to prevent the front end thereof from inverting in the manner shown in FIG. 3. At the same time, however, the outermost edge of the front end of the cup is of suitable size and flexibility to be able to penetrate beneath the gum line GL to perform a subgingival cleaning operation.

As noted earlier, the cup body is preferably formed of polyisoprene. That material can exhibit various degrees of hardness, depending upon its composition, as is known to those skilled in the art. For cleaning regular stains from teeth, there could be used a prophy cup according to the present invention having a durometer value (i.e., hardness) of 30-40; for cleaning heavy stains, such as tobacco stains, the prophy cup could have a durometer value greater than 50 (e.g., 50-70). In accordance with the present invention, a prophy cup is provided which effectively distributes abrasive paste within the cavity and impedes the centrifugally-induced loss of the paste from the cavity. This serves to conserve paste, and also to conserve time by reducing the number of occasions on which the operator must interrupt a tooth-cleaning operation to re-supply the prophy cup with paste. Also, it is less likely that at any given moment the operator will be performing a cleaning operation with an insufficient amount of paste in the cup. Furthermore, it is ensured that the mouth of the cavity 122 will not invert, and will, in fact, penetrate beneath the gum line to perform a subgingival cleaning.

Although the present invention has been described in connection with a preferred embodiment thereof, it will be appreciated by those skilled 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.

Claims

WHAT IS CLAIMED IS:

1. A dental prophy cup comprising a body having a rear mounting portion (12) adapted to be mounted on a rotary handpiece for rotation about a longitudinal axis of rotation (A) , and a front tooth-engaging portion (120) formed of an elastomeric material and including a cavity (122) for receiving an abrasive paste, said cavity expanding toward a front end (146) of said body, said cavity being defined by a surface having formed therein a channel arrangement comprising a paste-delivery channel extending forwardly from a rear portion of said cavity, and a circumferentially extending paste-distribution channel (132) spaced rearwardly from a front end of said body, said paste-delivery channel intersecting and terminating at said paste-distribution channel such that paste is induced to flow within said channel arrangement under the urging of centrifugal force during rotation of said body, characterized in that said body includes a distance D extending from a point (P) on an external surface of said body to a line (L') which extends parallel to said axis of rotation (A) and passes through a radially outermost portion of a front end of said body, said point (P) lying on a bisector B of said paste-distribution channel, a ratio D/Tl being less than 1.0; and a ratio (T2/T1) of a thickness (T2) of a mouth of said cavity to a minimal thickness (Tl) of a wall of said tooth-engaging portion at said paste-distribution channel being in the range zero to 0.75.

2. The dental prophy cup according to claim 1, wherein said ratio (T2/T1) is about 0.36.

3. The dental prophy cut according to claim 1, wherein a ratio (Tl/L) of said minimal thickness (Tl) to a length (L) of said cavity is in the range 0.16 to 0.24, and most preferably is about 0.19.

4. The dental prophy cup according to claim 3, wherein a ratio Tl/R of said minimal thickness (Tl) to a radius (R) of a mouth of said cavity is in the range 0.2 to 0.3 and most preferably is about 0.24.

5. The dental prophy cup according to claim 1, wherein a range Tl/R of said minimal thickness (Tl) to a radius (R) of a mouth of said cavity is in the range 0.2 to 0.3 and most preferably is about 0.24.

6. The dental prophy cup according to claim 1, wherein said ratio D/Tl is preferably 0.25 to 0.75, and more preferably is 0.35 to 0.6, and most preferably is 0.42.

7. A dental prophy cup according to claim 1, wherein said body includes a dimension (H) from said front end to a plane (C) oriented perpendicular to said axis of rotation (A) and passing through said point (P) , said dimension (H) extending parallel to said axis of rotation (A), a ratio H/Tl being in the range 1.0 to 2.0.

8. The dental prophy cup according to claim 7, wherein said range is preferably 1.25 to 1.5, and most preferably is 1.35.

9. The dental prophy cup according to claim 7, wherein a ratio D/H is preferably in the range 0.25 to 0.35 and most preferably is 0.31.

10. A dental prophy cup according to claim 1, wherein said paste-distribution channel includes a circumferentially continuous front wall.

11. A dental prophy cup according to claim 1, wherein there are a plurality of said paste-delivery channels spaced circumferentially apart, and a plurality of said paste-distribution channels spaced longitudinally apart.

12. A dental prophy cup according to claim 1, wherein said paste-distribution channel constitutes a front paste-distribution channel, said cavity further including a rear paste-distribution channel disposed rearwardly of said front paste-distribution channel and extending circumferentially, said rear paste-distribution channel being interrupted circumferentially by said paste- delivery channel.