US3618154A

US3618154A - Brush

Info

Publication number: US3618154A
Application number: US7891A
Authority: US
Inventors: Joseph C Muhler; Paul C Clark; James A Ford
Original assignee: Indiana University Foundation; Plastek Co
Current assignee: Indiana University Foundation; Plastek Co
Priority date: 1970-02-02
Filing date: 1970-02-02
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

An improved brush formed of plastic comprises a base and a plurality of bristles molded integrally with the base, the said base and bristles having incorporated therein up to about 30% by weight of an abrasive material. The bristles are provided in a plurality of cylindrical clusters, with the bristles in each cluster being tapered from the wide bases to relatively narrow tips. By tapering the bristles from relatively wide bases to relatively narrow tips. large numbers of such integrally molded brushes can be reliably manufactured in a short period of time due to the superior metering of plastic material into the tapered bristle-forming cavities in the mold.

Description

NM! 9, 1971 J. c MUHLER ETAL 3,618,154

BRUSH Filed Feb. 2, 1970 4 Sheets-Sheet 1 .2 6 nlllllllllllll:

INVENTORS JOSEPH CIMUHLER PflUL C. CLARK JAMES 4. FORD Filed Feb. 2, 1970 J. C. MUHLER ET AL BRUSH 4 Sheets-Sheet m ILIV VENTORS JOSEPH C. MUHL ER PA UL C. C L A PK JA MES A. FORD Filed Feb. 2. 1970 LER ETAL BRUSH JAMES A. FORD WMJM 4 Sheet s 3 INVENTORS JOSEPH a. MUHL PAUL c. cLARK V0 M971 J c MUHLER ETAL BRUSH Filed Feb. 2, 1970 4 Sheets-Sheet A IIVVEIVTOFS JOSEPH C. MUHLEW PAUL C. CLARK JAMES A. FORD United States each Filed Feb. 2, 1970, Ser. No. 7,891 lint. Cl. A4611 15/00 US. Cl. 15-1167 8 Claims ABSTRACT OF THE DISCLOSURE An improved brush formed of plastic comprises a base and a plurality of bristles molded integrally with the base, the said base and bristles having incorporated therein up to about 30% by weight of an abrasive material. The bristles are prow'ded in a plurality of cylindrical clusters, with the bristles in each cluster being tapered from wide bases to relatively narrow tips. By tapering the bristles from relatively wide bases to relatively narrow tips, large numbers of such integrally molded brushes can be reliably manufactured in a short period of time due to the superior metering of plastic material into the tapered bristle-forming cavities in the mold.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to brushes and more particularly to an integrally molded, one-piece brush, especially a toothbrush, in which the plastic material from which the brush is molded incorporates up to about 30% by weight of an abrasive material, especially a dental abrasive material.

Description of the prior art Typically, toothbrushes and other forms of brushes have been manufactured in large quantities through the use of several complex and inter-related manufacturing steps. First, the brush handle or base is molded, stamped, otherwise suitably formed and then, in a separate manufacturing operation, bristles or bristle tufts are suitably mounted in the brush handle or base. Typically this operation has involved drilling or otherwise mechanically forming suitable openings in the handle or base in which the bristles or bristle tufts are inserted.

While a number of integrally molded, one-piece brushes have heretofore been known, these prior art arrangements have been unsuitable for a number of reasons. These prior art arrangements were particularly unsatisfactory by reason of the complex molding equipment employed or by reason of the design thereof such that quality control and r high speed operation would not be achieved.

Accordingly, a prime object of the present invention is the provision of new plastic molding techniques and new integrally molded brush designs in accordance with which the disadvantages of the prior art approaches may be overcome and whereby simple, economical, one-piece integrally molded brushes may be manufactured in large numbers.

In the dental health held today, toothbrushing is ordinarily accomplished with an inert brushing implement or device which is adapted for use with a dentifrice composition (either a toothpaste or a toothpowder) which contains an abrasive substance or material designed to clean the teeth i.e., to remove stains, plaque, pellicle, and dental calculus (tartar). While presently known dentifrice compositions have not been Wholly satisfactory in this regard, it has been essential that the dentifrice contain such an abrasive material in order for any cleaning to 3,6l8,l54 Patented Nov. 9, 1971 occur. Indeed, while so-called liquid dentifrices (i.e., dentifrice compositions not incorporating an abrasive component) have been known, they have been completely unsatisfactory by reason of their inability to clean the oral hard tissues.

However, as a result of the provision of insoluble mineral components (abrasives) in dentifrice compositions, the therapeutic advantages of water-soluble fluoride and stannous ion containing anticariogenic agents in such dentifrice compositions has been severely limited. The insoluble abrasives exert a deactivating effect on the stannous and fluoride ion components.

Accordingly, another primary object of the present invention is the provision of a one-piece integrally molded plastic toothbrush incorporating an abrasive component capable of cleaning and polishing the teeth.

Yet another object is to provide a brush especially adapted for use with liquid dentifrice compositions containing soluble, anticariogenic agents, but no incompatible abrasive components.

A further object is to provide a toothbrush incorporating an effective amount of a dental abrasive material which is the same as an abrasive component of a dentifrice preparation such that hygienic and therapeutic cleaning and polishing effects of the dentifrice are complemented and enhanced by the common abrasive material provided in the toothbrush and/or bristling material.

Dental research has developed substantial evidence that beyond the age of forty years loss of teeth is predominantly the result of periodontal involvement rather than dental caries. The most important single factor contributing to periodontal disease is the accumulation of dental calculus (e.g., salivary tartar) on the teeth. These deposits result in tissue inflammation of the surrounding gingiva, and, as the condition increases its severity, the supporting bone is also affected. These reactions lead to the destruction of the supporting structures and the sub sequent mass loss of teeth.

Heretofore, available dentifrice systems have exhibited relatively unsatisfactory enamel polishing qualities and consequently have not been wholly elfective in preventing the accumulation of materia alba, oral debris, plaque, pellicle, stains, and dental calculus. While such systems are capable, to varying degrees, of removing materia alba, food particles, exogenous stains, and other tooth surface pigmentations when utilized in ordinary daily brushings, they have not exhibited the ability to remove the more resistant forms of enamel pigments and to produce a smooth tooth surface resistant to dental calculus reformation.

Dental researchers have devoted their efforts almost exclusively to effecting improvements in dentifrice systems by changing or altering the cleaning and polishing constituents thereof. Thus, the present invention has for another primary objective the enhancement of cleaning and polishing through the use of an implement rather than dentifrice systems.

A related object is providing a toothbrushing implement having improved cleaning and polishing performance (especially with respect to the prevention of re-accumulation of dental calculus, pellicle, material alba, and the more resistant forms of oral hard tissue stains and pigmentations Yet another primary object of the present invention is the provision of a dental health implement designed for use in stimulating gingival and thereby to reduce the susceptibility of the user to periodontal disease.

SUMMARY OF THE INVENTION The foregoing and other objects, advantages, and features are achieved with the present invention which comprises a brush formed of synthetic plastic material comprising a base and a plurality of bristles molded integrally therewith, the said base and bristles having incorporated therein up to about 30% by weight of an abrasive material. Preferably, the brush is a toothbrush in which a dental abrasive material, especially zirconium silicate, is incorporated. The bristles are preferably arranged on the base in a plurality of tufts, each tuft comprising a plurality of individually tapered bristles disposed about the periphery of a cylindrical grouping. By tapering the bristles from relatively wide bases to relatively narrow tips, large numbers of such integrally molded brushes can be reliably manufactured in a short period of time due to the superior metering of plastic material into the tapered bristle-forming cavities in the mold.

More particularly, where the integrally molded brush is a toothbrush, the abrasive material is preferably selected from the group consisting of zirconium silicate (ZrSiO calcium pyrophosphate (Ca P O anhydrous calcium hydrogen phosphate (CaHPO calcium hydrogen phosphate dihydrate (CaHPO -2H O), insoluble sodium metaphosphate [(NaPO calcium carbonate (CaCO alumina (A1 tindioxide (SnO talc [Mg Si O (OH and mixtures thereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a toothbrush produced in accordance with the present invention;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a right end view thereof;

FIG. 4 is an enlarged, sectional view taken substantially along line 44 in FIG. 2;

FIG. 5 is an elevational view of a bristle-forming pin used in the manufacture of the brush illustrated in FIGS. 1-4;

FIG. 6 is an enlarged, fragmentary view of the bristleforming pin shown in FIG. 5;

FIG. 7 is a top view thereof;

FIG. 8 is a fragmentary sectional view taken substantially along line 88 of FIG. 7;

FIG. 9 is a partially schematic sectional view taken through a molding apparatus which may be employed in the manufacture of the brush illustrated in FIGS. 1-4;

FIG. 10 is a right-end view of the lower part thereof;

FIG. 11 is a top plan view of one-half of an alternative mold part;

FIG. 12 is a sectional view taken substantially along line '12'12 of FIG. 11;

FIG. 13 is a sectional view of a complementary alternative mold;

FIG. 14 is a perspective view of another form of brush produced in accordance with one aspect of the present invention;

FIG. 15 is a bottom plan view of the brush shown in FIG. 14;

FIG. 16 is a side elevational view of another form of brush produced in accordance with the present invention; and

FIG. 17 is a fragmentary, exploded top plan view thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1-4 illustrate an integrally molded, one-piece plastic brush 20 produced in accordance with the present invention. Brush '20 comprises an elongated handle 22, a narrow neck 24, and a brush head 26, on which are integrally molded a plurality of bristle clusters 28. As best shown in FIG. 4, bristle clusters 28 comprise a plurality of individual bristles 30 disposed in cylindrical fashion. Bristles 30 taper from relatively wide bases 32 (adjacent brush head 26) to relatively thin, flexible tips 34 at their free ends. As Will hereinafter be explained in detail, the tapered bristle structure permits brush 20 to be manufactured in a high volume, automated basis with conventional injection molding equipment. In addition, because of the tapered configuration of bristles 30 (in accordance with which the free ends thereof are relatively flexible), when the brush 20 is used in the oral cavity and the ends of the bristle clusters 28 brush across the gingival tissues, 21 high degree of gingival stimulation occurs, and over time the gingival tissue becomes hyperkeratinized thereby enhancing periodontal health.

Brush 20, as well as the other brushes and bristling material hereinafter described in detail, may be made from any number of suitable plastic materials. Typical materials which may advantageously be employed include polyamides, such as nylon, flexible polystyrene, polyoleflns such as polyethylene and polyprophylene, acetals, urethanes, and the like. Mixtures of resins may be advantageously employed. Acetals, especially those commercially available from Celanese Corporation under the trademark Celcon 17A, 0-121 and M- and mixtures thereof, are preferred plastics for use in producing brush 20 in accordance with the present invention by reason of their strength, resiliency, and compatibility with abrasives as hereinafter described.

As previously noted, a special feature of the brush of the present invention is that up to about 30% by weight of a dental abrasive material is incorporated in the plastic material. The abrasive material may be incorporated into the plastic from which the device is molded in any convenient fashion. For example, the abrasive material may be physically mixed with the plastic material before it is pelletized or, alternatively, plastic pellets and abrasive in suitable quantities may be admixed in a suitable grinder prior to introduction of the plastic into the injection molding apparatus. Substantially any such method may be employed so long as the molten plastic reaching the mold contains up to about 30% by weight of the cleaning and polishing agent.

While up to about 30% by weight of the abrasive material may be used with satisfactory results, best results are achieved with about 5-20% by weight abrasive.

Suitable dental abrasive materials include zirconium silicate, ZrSiO talc [Mg Si O -(OH) calcium pyrophosphate, Ca2P207, calcium hydrogen phosphate dihydrate/ anhydrous calcium hydrogen phosphate,

insoluble sodium metaphosphate (NaPO calcium carbonate, CaCO alumina, A1 0 tin dioxide, SnO and others. Mixtures of these agents may be employed. Zirconium silicate is the especially preferred abrasive for use in practicing the present invention.

Mixtures of zirconium silicate and one or more of the foregoing other dental cleaning and polishing agents may advantageously be employed and such a mixture should comprise in excess of about 1% zirconium silicate and preferably in excess of about 10% zirconium silicate, by weight of the abrasive mixture. Especially good results are achieved with mixtures comprising about 20% and preferably about 25% zirconium silicate (Le, a 1:3 weight ratio of zirconium silicate to the other agent), by weight of the mixture. There is no practical maximum level for the zirconium silicate since as pointed out elsewhere zirconium silicate per se is a dental abrasive agent in its own right.

The size of particles of dental abrasives can be expressed in a number of different ways, one of the most common of which is mean diameter, i.e., the arithmetical average of the diameters of particles in a representative sample. As hereinafter utilized, the. term particle size refers to a mean diameter value.

Zirconium silicate is a well-known industrial abrasive which is used for the grinding and polishing of glass and ceramics, however, prior to the subject invention, this material had not been proposed for use as a cleaning and polishing material incorporated directly in a toothbrush for frequent and direct application to the teeth. The extreme hardness and the abrasion characteristics exhibited by zirconium silicate (e.g., a hardness number of 7.5 on the Mohs scale for commercially available zirconium silicate, such as types used for grinding of glass) would suggest to one skilled in the art that zirconium silicate would seriously damage (i.e., abrade and scratch) tooth structure and would thus be unsuitable for use on the teeth. However, it has been ascertained that it may safely be employed under the conditions of the present invention.

In accordance with the present invention, zirconium silicate, used alone or in combination with other cleaning and polishing agents, has particles distributed in a range of between about and 8 microns particle size. The preparation of suitable particle size zirconium silicate can be accomplished by conventional techniques well known to the art. Basically, these techniques involve milling zirconium silicate ore (zircon), followed by standard screen sieving (or air separation) to segregate the desired particle size. Various milling techniques may be utilized in order to obtain the desired surface configurations for the Zirconium silicate particles. For example, particles may be prepared by a ball and hammer milling technique. Preferably, the cleaning and polishing agent of the present invention comprises a mixture of ball milled and hammer milled particles.

As is well known to the art, hammer mills utilize a high speed rotary shaft having a plurality of hammers or beaters mounted thereon. The hammers may be T- shaped elements, bars, or rings fixed or pivoted to the shaft or to discs pivoted to the shaft. The shaft runs in a housing containing grinding plates or liners. The grinding action results from the impact between the material being milled and the moving hammers. When zircon ore is milled by an attrition technique such as hammer milling, relatively rough, jagged particles are produced. Particles having such jagged surface configurations function from a tooth cleaning standpoint in a relatively superior manner as compared to more smoothly configured particles.

Similarly, a ball mill comprises a cylindrical or conical shell rotating on a horizontal axis which is charged with a grinding medium such as balls of steel, flint, or porcelain. The grinding is accomplished by the tumbling action of the balls on the material to be ground. Particles of zirconium silicate treated in a ball mill of the character described have relatively smooth surface configurations and function better from the polishing standpoint than more jaggedly configured particles. Similar techniques can be employed with the other abrasives employed with the present invention.

The particle size distributions for a preferred abrasive system in accordance with the present invention are set forth in the following examples.

EXAMPLE I Particle size ZrSiO Weight percent 70 5 10 15 EXAMPLE II Another preferred abrasive system comprises a 1:1 weight mixture of alumina, A1 0 (240 mesh) and zirconium silicate particles lying in the range of up to about 8 microns particle size.

Especially good results may be achieved with toothbrushes in accordance with the present invention where the abrasive incorporated in the brush is also used in the dentifrice system employed with the brush.

FIGS. 5-10 illustrate the components of molds which may be employed in a conventional injection molding machine (not shown) to produce the brush similar to brush 20 shown in FIGS. 1-4. As best shown in FIG. 9, the mold arrangement comprises upper mold part 40 and lower mold part 42. Upper mold part 4t), for reasons that will hereinafter appear, comprises a pair of mold blocks 44 and 46, whereas lower mold part 42 comprises a pair of mold blocks 48, 50. Blocks 44, 46 are mounted by means (not shown) so that they may be raised so as to be spaced apart from lower mold blocks 48, 50.

Blocks

44, 46, 48, and 50 are cut away preferably through the use of conventional Elox equipment, to define four brush forming cavities, 52, 54, 56, and 58. When

mold parts

40, 42 are closed as shown in FIG. 9,

cavities

52, 54, 56, and 58 serve to define the handle, neck, and brush head for a brush, such as the brush shown in FIGS. l4.

A plurality of parallel, vertical bores 70 are provided in mold block 48, and bores 78 pass entirely through block 48 and communicate with cavity 58. A plurality of bristle-forming pins 72 are slidably fitted to close tolerances within bores 70. As is best shown in FIGS. 5-8, a plurality of grooves 74 are spaced equidistant about pin 72. Grooves 74 gradually and uniformly taper throughout their length from relatively wide and deep portions 76 adjacent the end of pin 74 to relatively shallow and narrow rounded end portions 78 spaced away from the end of pin 74. At their wide parts, grooves 74 nearly merge so that at their bases the bristles of a brush (such as brush 20 shown in FIGS. l4) almost form a substantially continuous cylinder. Grooves of the desired configuration (i.e., taper) may be provided in pin 74 through the use of Elox mold forming equipment.

When pins 72 are positioned in place in bores 70 in mold block 48, the ends of pins 72 at which wide and deep portions 76 of groove 74 are provided are flushed against the lower edge of cavity 58. Thus, pins 72 in cooperation with bores 70 thereby serve to define a plurality of bristle-forming cavities located peripherally and equidistant about pins 72. In this manner, when the mold parts are closed (as shown in FIG. 9) and heated plastic is injected into the cavity under pressure through a passageway defined by additional cavities 80-82 provided in blocks 44, 48, respectively (see FIG. 9), not only are the handle, neck, and brush head molded, but plastic is forced into the bristle cavities so as to provide integrally formed bristles such as bristles 30, shown in FIG. 4. Suitable gate means, not shown, are provided in the injection molding apparatus in order to properly control metered flow of molten plastic under pressure into the cavities in the mold parts.

In accordance with a prime feature of the present invention, because of the tapering of grooves 74, plastic is properly metered from cavities 58 into the bristle-forming cavities and the bristles are smoothly, efficiently, and reliably formed with none of the difficulties encountered in prior art molding devices in which non-tapered bristles are utilized. Further, because of the precise tolerances between the diameter of pins 74 and bores 70, proper venting of the mold cavities is achieved.

After upper mold part 40 is raised away from a molded brush produced in the foregoing manner, ejection of the molded brush from the lower mold part 42 is accomplished in the following manner. The lower ends of pins 72 are carried by a pair of

blocks

90, 92 which normally rest on a base block 94 separated from mold block 48 by a pair of spacers 96. Suitable means (not shown) are designed to operate sequentially so as to cause

blocks

90, 92 to move upwardly in the direction of an arrow A shown in FIG. 10 so as to cause pins 72 to move upwardly and thereby to push the molded brush upwardly out of

cavities

56 and 58. When block reaches a point adjacent to mold block 48, grooves 72 are positioned completely out of bores 70 in block 48. One or more additional knockout pins 98 (see FIG. 9) provided in bores 100 are adapted by means (not shown) to move upwardly so as to separate the formed bristle components from grooves 74 in pins 72.

The ejection of the integrally molded brush and bristles from the grooves 74 is facilitated by their tapered configuration shown in FIGS. 6 and 8. Furthermore, by

reason of the provision of the previously described abrasive material in the plastic from which the brush is molded, the separation of the molded part is further facilitated.

Thus, because of the configuration of the bristle-forming cavities, not only are the bristles more rapidly and reliably formed, but likewise the ejection and separation of the molded part is also facilitated. Further, as previously noted, the tapered bristles are preferable to non-tapered bristles by reason of their hygienic and therapeutic activity in the oral cavity and elsewhere.

By using upper and lower mold parts comprising separate pairs of blocks to define the handle and brush head, the same brush head may be molded on a variety of different handles. For example, in order to mold a brush with a handle such as that shown in FIGS. 1 and 2, mold blocks such as those shown in FIGS. 11-13 should be employed. FIGS. 11 and 12 show an upper mold block 60 which could be inserted in the molding machinery in place of the block 46 shown in FIG. 9 in order to obtain a manual toothbrush handle. Block 60 thus has a handle defining cavity 62 formed therein which corresponds to a handle of the design of handle 22 shown in FIGS. 1 and 2. Likewise, FIG. 13 shows complementary lower mold block 64 having a handle forming cavity 66 formed therein. In addition, a pair of bores 68 are provided in block 64 to permit knock-out pins (not shown) to operate in removing a molded part from the cavities after the upper and lower mold parts have been separated. By means of the mold part 104 shown in FIG. 9, a suitable attaching handle for use in an automatic toothbrush power handle may be obtained. Thus, by merely shifting from mold blocks such as 60, 64 shown in FIGS. 11-14 to mold blocks 46, 50 shown in FIG. 9, the same basic apparatus may be used to mold both manual toothbrushes and automatic toothbrushes. Further, the highly sophisticated, exact tolerances required for blocks 44, 48 and the associated bores and bristle forming pins need not be changed or duplicated to produce the two types of brushes.

FIGS. 14 and 15 illustrate a brush 110 produced in a similar manner but intended for use in a different fashion. Brush 110, which could be employed as a hairbrush, has a relatively Wide rectangular brush head with a short projecting handle 114 molded integrally therewith. On the face of brush head 112 are provided a plurality of regularly arranged bristle clusters 116, each consisting of a plurality of individual bristles disposed equidistant about the periphery of a cylinder. These bristles taper in the same manner as the bristles on brush shown in FIGS. 14.

As will be obvious to those skilled in the art, substantially any sort of brush could be molded in the foregoing fashion and any arrangement or configuration of bristle clusters on the brush head could be obtained. Indeed, a relatively thin elongated brush head with bristles formed thereon in accordance with the present invention could be attached to a wheel and thereby serve as a buffing brush.

Finally, depending upon the individual use to which the brush may be put, the abrasive component thereof may be omitted, but in accordance with the preferred practice of the present invention, the abrasive component is incorporated even in hairbrushes such as brush 110 shown in FIGS. 14 and 15.

A further aspect of the present invention is shown in FIGS. 19 and 20, in which is illustrated a toothbrush 150 comprising a handle 152 and a detachable brush head 154 having formed integrally thereon in accordance with this invention a plurality of bristle tufts 156. Brush head 154 is detachably mounted so that it may be discarded after use. Thus, a permanent handle 152 could be distributed with a number of replaceable brush heads 154 in order that the user could have the benefit of using a clean, sterile bristle head at each brushing. Advantageously, the in- 8 tegrally molded brush head 154 incorporates a dental abrasive material as described hereinbefore.

While any suitable interlocking arrangement could be employed to attach brush head 154 to handle 152, a preferred arrangement involves forming a recessed slot 158 in the interior of brush head 154, with a mating tongue 160 being provided on handle 152. Tongue 160 may be slidably received in slot 158, with a detent locking arrangement 162, com-prising a stud 164 formed on handle 15 2 and a recess 166 formed in an overhanging end portion 168 of brush head 154, being provided to securely lock the brush head 154 in place. As noted, other interlocking arrangements can be employed so long as the above-described objectives are achieved.

As previously noted, through the use of a toothbrush, preferably an integrally molded, one-piece plastic toothbrush incorporating up to about 30 of a dental abrasive material in accordance with the present invention, substantial and material dental health benefits may be obtained. A clean and very highly polished tooth surface may be achieved (thus reducing the accumulation and reaccumulation of dental plaque, pellicle, and dental calculus), thereby not only contributing to the minimization of periodontal disease, but also serving in reducing the incidence of dental caries. Furthermore, because of the nature of the tapered integrally molded plastic bristles, a superior implement for gingival stimulation is provided and the resulting oral health benefits accruing therefrom may be obtained.

These substantially hygienic and therapeutic oral health benefits have been experimentally verified in the following manner.

EXPERIMENTAL EVALUATIONS The superiority of the abrasive-containing brushes of the present invention has been substantiated by the following experimental evaluations. A definitive laboratory cleaning test procedure has been used to evaluate a number of toothbrushes, among which were brushes produced in accordance with the present invention. This procedure (as set forth and described in Cooley et al. US. Pat. No. 3,151,027) involved the use of polyester plastic blocks specifically designed for use in an electric toothbrushing machine. The blocks are ground smooth, washed, dried, and a thin coating of black lacquer is carefully applied to the surface of the block. The blocks are then inserted in the toothbrushing machine and brushed with the brushes for 3,000 double strokes with a pressure on the lacquer surface of grams. Reflectance measurements of the blocks are then obtained through the use of a reflectometer. The cleaning values for the materials tested are given in Table I, on a scale ranging from 0 to 6.5, a higher value indicating a greater cleaning ability (i.e., higher reflectance produced by greater removal of the lacquer is indicative of better cleaning ability).

Enamel polishing values have also been obtained in accordance with a so-called toothbrush polishing procedure. The lingual surfaces of freshly extracted maxillary anterior teeth are reduced with the aid of a diamond disc, and the teeth are mounted by means of a low melting alloy, such as Woods metal, on hexagonal jigs constructed so as to fit the movable state of a reflectometer. The exposed labial surface of each tooth is mounted in such a manner that the height of the contour is a suitable distance above the base of the jig. Throughout the procedure, care is taken to ensure that the teeth do not become dry in order to prevent damage of the tooth tissues. The exposed enamel surface is then dulled by exposing it to 0.10% hydrochloric acid (pH 2.2) for 30 seconds. Any acid remaining on the tooth surface is neutralized by immediately transferring the tooth to a saturated sodium carbonate solution for 30 seconds. The tooth is then rinsed with water and blotted dry.

The maximum reflectance of the dulled tooth surface is determined by means of a reflectometer especially adapted to detect the changes in the degree of polish of 9 the enamel surface. The refiectometer is constructed so that the enamel is exposed to a beam of polarized light, and the amount of light reflected from the enamel surface is determined by a photoelectric cell which in turn acti- 10 the radioactivity determined. Using this as a standard, the amount of tooth dentin removed during the treatment can be determined by comparing the experimental count with the count of a standard. The results are revates a galvanometer. The smoother the enamel surface, ported numerically, with a high number indicating greater the smaller the amount of diffused and absorbed light abrasion. Enamel abrasion has been determined by the and, hence, the higher galvanometer reading. same procedure using human dental enamel specimens. After the maximum reflectance of the dulled tooth is Cleaning and polishing values and dentin and enamel determined, the tooth is polished with a toothbrush abrasion values have been determined for a number of mounted on an automatic toothbrushing machine for a abrasive-containing integrally molded plastic tooth specified number of strokes. After the tooth has been brushes and for representative conventional brushes. In polished, the enamel surface is rinsed with water so as to many instances, cleaning scores were obtained using a remove any residual particles of the cleaning and polishdistilled water medium and, in addition, a calcium pyroing agent, and the reflectance of the enamel surface is phosphate dentifrice medium. The data, as well as the again measured with the tooth located in exactly the same constituents of the brushes, are reported in Table I. These position as that used to obtain the dull reading. The data support the efficiency of the brushes of this invenabsolute change in the amount of reflectance between the tion as safe cleaning and polising, especially polishing, dulled and polished enamel surfaces is taken as a measaids. In particular, the data demonstrate that without ure of the degree of polishing imparted by the prophylaxis sacrificing cleaning effectiveness and without undue abratreatment. sion, substantial polishing improvements may be achieved.

TABLE I Cone.

percent of Cleaning ratio Polishing Dentin Enamel Polishing polishing score abrasion abrasion Type ofbrush Type ofplastre agent agent H2O CazP2O1 (H) (H20) (H20) Conventional' 1 0.62 48316 1.77i0. 1.1s 49:1;11 3.75i0.52 0.52 nails 3. ssio. 42 0. 5s 415:0 4. 27:10.55 2.22 0.45 29.1=1=1.8 2. 80:1;0. 0.57 0. 33 22. 6:1;1.9 2. 22, 0.23 1.23 0.00 37. 4514.1 2. 05 510. 54 5 2. 4s 0. 00 43. 4i9.8 2. 83:1 0. s4 5 1.11 1.84 29.9i2.9 2.55:1:025 Acetal resin lzAcetal resin II (:50 mixture)" ZrSiOi 5 2.11 2.18 39.9i3.4 2. 83:1- 0. 41 Atetal) resin II: Acetal resin III (50:50 mix- ZrSiOi 5 1.35 2.08 33.43131 3. 63:1:0

D0 Acotal resin III ZrSiO /A1 0 5 1. 03 0. 03 40. 0i3.4 2. 435:0. 29 Do do zrsioi Anw 10 1.71 1.30 37. 5i4.2 2. 3010. 10

1 Standard error of the mean.

2 The Acetal resins Were commercially obtained from Celanese Corporation under the trademarks Golcon 17A, M-90, and (3-121.

In spite of the described excellence of the toothbrushes of the present invention, these devices do not remove substantial amounts of oral hard tissue. Tooth dentin is frequently found exposed at the surface of the teeth near the free gingival margin, particularly in clinical cases where the gingivae have receded. The abrasion of tooth dentin by a cleaning and polishing agent is much greater than the abrasion of tooth enamel by the same agent, i.e., 10-100 times. Consequently, dentin abrasion is considered to be of greater clinical importance than enamel abrasion, and the effect of a cleaning and polishing device on dentin is used as an. important and reliable criterion in the selection of suitable agents. The brushes manufactured in accordance with the subject invention have highly satisfactory dentin abrasion characteristics, a fact which is quite surprising in view of the innate hardness of the materials.

A method for determining dentin abrasion values is as follows. The dentin portions are separated from human central incisors and exposed to neutron radiation whereby a predetermined portion of phosphate content is converted to P Each dentin portion is mounted in a low melting alloy, such as Woods metal, and is submerged in distilled water to be tested. A stimulator mounted in an automatic toothbrushing machine is arranged so that it can be moved back and forth across the surface of the submerged portion of the dentin, and the pressure of this stimulator is adjusted to 150 grams. The tooth dentin is subjected to polishing action for a given number of strokes, and removed from the water. The radioactivity of the water is then determined by conventional means. An equivalent piece of dentin, irradiated concurrently with the dentin portion to be brushed, is weighed, dissolved in hydrochloric acid, and

From. the foregoing it can be seen that the abrasivecontaining brushes of the present invention represent a substantial advance in the dental health arts. The use of this implement permits one to clean and polish the interproximal tooth surfaces so as to remove and inhibit the reformation of interproximal plaque, pellicle, and calculus. Likewise, it provides a safe, sanitary method for mildly stimulating the gingival tissues. Further, through the use of the plastic molding technology of the present invention, superior integrally molded brushes may be obtained.

We claim:

1. In a one-piece molded plastic toothbrush comprising a brush base and a plurality of bristles projecting from and formed integrally with the brush base, the improvement comprising the incorporation in the plastic of which the brush is formed of up to about 30% by weight of a dental abrasive material selected from the group consisting of zirconium silicate (ZrSiO' and mixtures thereof with calcium pyrophosphate (Ca lP O anyhdrous calcium hydrogen phosphate (CaHPO calcium hydrogen phopshate dihydrate (CaHPO -2H O); insoluble sodium metaphosphate [(NaPO calcium carbonate (CaCO alumina (A1 0 talc [Mg Si O (0H) and tin dioxide (SnO the particles of zirconium silicate lying in the range of up to about 20 microns particle size.

2. The improvement, as claimed in claim 1, wherein the dental abrasive material is present in the plastic material of the brush at a level of about 5-20% by weight.

3. An integrally molded plastic brush comprising:

a brush base; and

at least one cluster of bristles on the brush base, each such cluster comprising a plurality of individual bristle members positioned substantially equidistant from adjacent bristles in a generally cylindrical configuration; each bristle member being tapered from a relatively wide base in close proximity with the bases of adjacent bristle members to relatively narrow tips; the said brush base and bristle members being integrally molded in one-piece of plastic material, and up to about 30% by Weight of a dental abrasive material selected from the group consisting of zirconium silicate (ZrSiO and mixtures thereof with calcium pyrophosphate (Ca P O anhydrous calcium hydrogen phosphate (=CaHPO calcium hydrogen phosphate dihydrate (CaHPO -2H O); insoluble sodium metaphosphate [(NaPO' calcium carbonate CaCO alumina (A1 and tin dioxide (SnO' the particles of zirconium silicate lying in the range of up to about 20 microns particle size, being incorporated in the plastic material from which the brush is formed. 4. A brush, as claimed in claim 3, wherein the brush base includes integrally molded handle means.

5. A brush, as claimed in claim 3, wherein the plastic material is nylon.

'6. A brush, as claimed in claim 3, wherein the abrasive material is present in the plastic material at a level of about -20% by weight.

7. A brush, as claimed in claim 3, wherein the brush base is removably mounted on handle means.

8. A brush, as claimed in claim 7, wherein the brush base has a slot means formed therein, with mating tongue means being provided on the handle means, detent locking means being provided for removably securing the tongue means in the slot means.

References Cited UNITED STATES PATENTS 2,279,355 4/1942 Wilensky 15-110 2,328,998 9/1943 Radford 15-l59 A 3,050,072 8/1962 Diener 15110 X 3,252,775 5/ 1966 Tocci-Guilbert 51295 X 3,378,445 4/1968 Muhler 424-49 3,522,342 7/1970 Nungesser et al. 15-159 A X FOREIGN PATENTS 240,817 9/ 1962 Australia 1 6l87 590,097 3/1959 Italy 15-187 PETER FELDMAN, Primary Examiner US. Cl. X.R.