Abstract:
A denture treating apparatus employs a receptacle base with a chamber closed by a rotatable cover. A denture and an effervescing denture treating composition, such as a denture cleaning tablet is place in water in the chamber. When the chamber is closed, the pressure created by the effervescing tablet causes the active ingredients to penetrate small spaces in the denture. A seal is compressed between relative thick peripheral lips on the cover and receptacle base. Thinner sections of the receptacle base can bow under pressure to show that pressure is building up. A shiftable handle on the cover makes it easier for a user to close the cover and compress the seal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is related to the treatment of dentures and especially to more effectively cleaning or deodorizing dentures. This invention is also directed to the removal of biolayers that can build up in confined spaces within a denture and to the capability of denture treatment compositions to wet or contact confined areas where these biolayers can be deposited. 
     2. Description of the Prior Art 
     Many methods and techniques have been suggested to facilitate cleaning and disinfecting dentures. Denture cleaning can be broadly defined as the reduction of a biolayer or biofilm and plaque containing bacteria, fungi and virus and pathogens or debris in general. Generally some method is employed to disrupt the plaque coating or biolayer and to soak the denture to allow chemical solutions to interface with denture surface and with porosities, micro-channels, fissures, cracks, fractures and spaces between teeth and the acrylic that retains the teeth in the gum portion of the denture. Additional pores, micro-channels, fissures, cracks, and fractures can be formed as a denture ages or by scratching, by toothpaste abrasives, and bacterial action that pits the denture surface. 
     One common approach to cleaning dentures is to use effervescent tablets, which foam when placed in water. Conventional tablets contain cleaning agents. Traditionally, these tablets have a composition containing a variety of sulfate salts, such as bisulfates, monopersulfates and sulfates acting as detergents, oxidizers and the like. They have also used alkali metal and alkaline earth metal halides as bleaches. Such compositions have also included perborate, carbonate and phosphate salts in varying amounts to provide effervescence and activation. A discussion of some of these traditional effervescent cleaning compositions can be found in U.S. Pat. No. 4,857,224, which is incorporated herein be reference. 
     Limitations have been encountered with standard prior art methods. Strong solutions containing alcohol adversely affect the acrylic. Some cleaning or treatment solutions are too strong for biocompatibility with oral tissues. Microwaving weakens the dentures and may warp the acrylic due to uneven heat buildup. Mechanical means to scrap the denture surface are incomplete and the size of practical mechanical scraping means is too large to remove plaque in microscopic pores, micro-channels, fissures, cracks, and fractures. Furthermore mechanical means tend to scarify or abrade the denture surface thereby increasing fissures where pathogens may build up. 
     A method for improving the action of standard denture treatment compositions, such as denture cleaners, and an apparatus for use in practicing that method is disclosed in U.S. patent application Ser. No. 10/339,802 filed on Jan. 10, 2003. This pending patent application is entitled Treatment of Dentures at Elevated Pressures. The apparatus disclosed therein has demonstrated the efficacy of employing elevated pressures with standard denture cleaning and treating compositions. However, the apparatus depicted therein, has some practical problems. For instance, it can be difficult to maintain an adequate gas tight pressure seal in a relatively inexpensive pressure containment vessel suitable for use by the average consumer. The rigidity needed for surfaces compressing the seal introduces difficulties because of the limitations imposed by injection molding plastics for such a product. Also, the amount of force that may be needed to adequately compress a seal may be difficult to apply for elderly users who may have inadequate grip strength. It is also important that the pressure generated by effervescent denture cleaning compositions not be lost by a failure to quickly seal the pressure chamber. The denture treatment, pressure containment vessel of the instant invention addresses these and other problems. 
     SUMMARY OF THE INVENTION 
     The denture treating apparatus according to this invention is primarily intended to improve the performance of a conventional denture cleaning tablet by employing a pressure tight container in which the conventional denture cleaning tablet is employed. Pressure in excess of ambient pressure is believed to promote additional penetration of the cleaning agent in a conventional denture treating tablet so that contaminants, especially contaminants located in crevices and confined spaces in a denture, will be more effectively exposed to active cleaning agents. According to the preferred embodiments of this invention, this excess pressure is developed by activation of a conventional denture cleaning tablet within a confined pressure chamber. Effervescence resulting from depositing such a conventional denture cleaning tablet in water can be relied upon to produce this enhanced pressure, but it has been found that to reliably generate effective pressures, the pressure containment vessel must employ a gas tight seal that will not leak when subjected to pressures on the order of ten (10) to twenty five (25) psi above ambient or atmospheric pressure. A practical pressure containment vessel suitable for use with a conventional denture cleaning tablet must not only be capable of maintaining pressures of this magnitude, but the pressure containment vessel must also be relatively inexpensive to produce and must be easy to open and close, especially by an elderly denture wearer. A pressure containment vessel in accordance with this invention is intended to be used by a typical denture wearer, and in order to be cost effective, it would need to be injection molded and mass marketed. However, it has been found that the combination of the required sealing performance with standard, relatively inexpensive manufacturing methods is difficult to achieve. The pressure containment vessel must be sealed and force must be evenly applied to a seal. It has been found that the top of the pressure containment vessel should be screwed to the receptacle base of the pressure containment vessel in order to evenly apply a force around the entire seal. If an effervescent denture cleaning tablet is employed it is also necessary to quickly close the chamber or cavity before significant amounts of gas escapes. It has also been determined that the surface supporting a seal cannot be deformed when pressure is applied by screwing the two vessel components together. Otherwise it would be difficult to maintain intimate contact between a sealing gasket and the surfaces abutting the sealing gasket. Furthermore a gasket forming the seal must have sufficient lubricity to allow the vessel to be closed with an even pressure distribution. Since most denture wearers are elderly, the pressure vessel needs to be configured so that it can be closed by users who may possess less than average strength and may find it difficult to apply the force necessary to maintain an adequate seal. These requirements impose somewhat contradictory limitations of a denture treatment apparatus having the desired capabilities. 
     A denture treating apparatus according to one embodiment of this invention and possessing characteristics sufficient to overcome the enumerated and other difficulties encountered in the development of this apparatus, includes a cover that can be mounted on a receptacle base to enclose a pressure containment chamber or cavity. The receptacle base forms the majority of this chamber, which has an open end at the top of the receptacle base so that the chamber can be filled with water or some other fluid. The receptacle base includes a receptacle base peripheral lip extending around the open end of the chamber. The cover can be secured to the receptacle base over the open end of the chamber, to close the chamber. The cover includes a cover peripheral lip opposed to the receptacle base peripheral lip when the receptacle base is secured to the open end of the chamber. A seal is positioned between the receptacle base peripheral lip and the cover peripheral lip. The cover can be rotated relative to the receptacle base to compress the seal to form a pressure tight chamber in which a denture can be treated or cleaned. The receptacle base comprises a one-piece molded member including a cylindrical outer wall and a bottom wall. The cylindrical outer wall is thicker in a section forming the receptacle base peripheral lip than in a section forming the bottom wall. The thin wall extends over the majority of the receptacle base and are easier to fabricate, but the thicker peripheral lip provides a surface, which will not excessively deform under pressure while in engagement with the seal. The cover can have also employ a relatively thick cover peripheral lip compressing the seal. A relatively thinner receptacle base bottom section can bow outward under pressure to show a user that an effective pressure is being developed within the gas tight chamber. Also a relatively thinner bottom section will relieve stress that would otherwise tend to deform the sealing rim. 
     A denture treating apparatus, that can be closed by a user who may not possess normal grip strength employs handles on the cover and the receptacle base. One handle is attached to the cover and engages the cover to twist the cover relative to the receptacle base to open and close the chamber. This handle is shiftable relative to the cover between multiple positions to improve the ease of manipulating the handles to close the cover. The cover handle imparts rotation in opposite directions to open and close the chamber. 
     The cover of this apparatus may also include a holder in which a denture treatment tablet may be mounted prior to introducing the tablet into water in the receptacle base chamber. In this way an effervescing tablet will only begin to emit gas as the cover encloses the chamber, and gas will not be lost before the chamber is closed. Effective pressure can then be more reliably developed by an inexperienced user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of a pressure treatment vessel according to this invention showing a cover mounted on a receptacle base. 
         FIG. 2  is a view of the receptacle base comprising one part of the vessel of  FIG. 1   
         FIG. 3  is a side view of the receptacle base shown in  FIG. 2 . 
         FIG. 4  is a top view of the receptacle base of  FIGS. 1-3  showing the chamber formed in the receptacle base. 
         FIG. 5  is a view of the cover mountable on the receptacle base. 
         FIG. 6  is a top view of the cover showing radially extending strengthening ribs. 
         FIG. 7  is a side view of the cover handle. 
         FIG. 8  is a top view of the cover handle. 
         FIG. 9  is a bottom view of the cover handle. 
         FIG. 10  is a view of the gasket seal. 
         FIG. 11  is a cross sectional view of the vessel showing a sealed chamber and the water level and the manner in which a denture treatment tablet is introduced into the water. 
         FIG. 12  is a cross sectional view of an alternate embodiment of a denture treating apparatus in which a holder on the interior surface of the cover retains a denture cleaning tablet. 
         FIG. 13  is a view of the interior surface of the cover of the embodiment of  FIG. 12 . 
         FIG. 14  is a view of the receptacle base and the open chamber of the embodiment of  FIGS. 11 and 12 . 
         FIG. 15  is a cross sectional view showing another alternative approach to positioning a denture cleaning tablet on the apparatus cover. 
         FIG. 16  is a view of the interior surface of the cover of the embodiment of  FIG. 15 . 
         FIG. 17  is a view of a third embodiment in which the tablet is positioned within a recess in the cover. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The denture treating apparatus  2  according to the preferred embodiment of this invention can be employed to treat dentures. Normally vessel  2  would be employed to clean a denture using any one of a number of commercially available standard denture cleaning tablets. This invention can be employed to improve the effectiveness of standard effervescent denture cleaning tablets including both cleaning and foaming agents. Conventional tablets, such as Efferdent denture cleaning tablets and Polident denture cleaning tablets could be employed. Efferdent is a trademark of Warner-Lambert and Polident is a trademark of Glaxo Smith Kline. Use of this pressure enhanced denture treatment apparatus  2  is not limited to use of these commercially available compositions. Other treatments, including cleaning, disinfecting, deodorizing, brightening, bleaching or other compositions could also be employed. For example, the treatment agent could include menthol or eucalyptus oil. Other treatment agents could include, but would not be limited to, cetylpyridinum chloride, chlorhexidiene gluconate, eugenol, clove oil or peppermint oil. Chlorine dioxide could be used as the active agent and as the foaming agent for denture treatment in a dentist&#39;s office. As this compound dissociates the chlorine would provide the anti-bacterial agent and the oxygen would increase the pressure within the pressure containment vessel. Other simple foaming agents could also be employed. For example, baking soda and a salt could be used to make the water acidic to release carbon dioxide. In other words, both the materials and the pressure containment structures disclosed herein are merely intended to be representative, and other compositions and mechanical components would be readily apparent to one of ordinary skill in the art. It is believed that this pressure treating vessel would also increase the effectiveness of virtually any denture cleaning or treating solution because the added pressure will disperse the active ingredient into tight spaces in the denture where pathogens or bacteria might not otherwise be exposed to active denture treating or cleaning agents. A pressure treating apparatus according to this invention would therefore even improve the effectiveness of new denture or dental treating agents that may not be currently be commercially available or may not as yet have been developed. 
     As shown in  FIG. 1 , the denture treating apparatus or vessel  2  comprises a receptacle base  10  to which a cover  30  can be secured. The cover  30  can be screwed onto the receptacle base  10  to close a chamber  22 , as shown in  FIG. 2 , formed within the receptacle base  10 . A gasket seal  70  will be compressed between the cover  30  and the receptacle base  10  to provide a pressure tight seal that will prevent the passage of either liquids or gas. The cover  30  can be closed and opened by twisting the cover  30  relative to the receptacle base  10 . A receptacle base handle  20  and a cover handle  50 , both of which protrude radially from the main section of the denture treating vessel  2 , provide sufficient mechanical advantage to allow the cover  30  to be closed tightly so that the gasket seal  70  can be compressed sufficiently to maintain a gas tight seal. This mechanical advantage is important because dentures  84  will normally be worn by older people, many of whom are not capable of exerting a great deal of force to close the chamber  22 . The receptacle base handle  20  will preferably comprise an integral part of a one-piece molded receptacle base  10 , and will therefore be rigid relative to the main cylindrical section of receptacle base  10 . In the preferred embodiment of this invention, the cover handle  50  will be pinned to the cover  30  about a central pivot point  62  so that the cover handle  50  can be rotated relative to the cover  50 , and when placed in the operative position shown in  FIG. 1 , the cover handle  50  can be rotated relative to receptacle base handle  20  to impart rotation of the cover  30  relative to the receptacle base  10 . As will be subsequently discussed in greater detail, the cover handle  50  can be lifted and positioned, relative to receptacle base handle  20 , so that the two handles are in a convenient position for closing or opening the chamber  22  by rotating the cover  20 . Furthermore, the position of the cover handle  50  relative to the remainder of the cover  30  can be changed while the cover is partially closed or open if convenient. 
       FIGS. 2-4  show the receptacle base  10  in more detail. Receptacle base  10  can be injection molded employing a commonly available plastic resin, such as an acrylic. Other materials or manufacturing processes can be employed, but receptacle base  10  is especially adapted to be constructed using a straight pull, injection molding process so that the receptacle base  10  can be economically fabricated. The receptacle base  10  has sufficient strength so that a pressure of at least ten (10) psi above ambient pressure can be maintained within chamber  22 . The chamber  22  is generally cylindrical in shape and is defined by a receptacle base cylindrical outer wall and a flat bottom wall  16  that closes the bottom of chamber  22 . An open upper end  24  has an inner diameter equal to the inner diameter of the remainder of the chamber  22 . Although limited to one particular size, one representative embodiment of receptacle base  10  employs a chamber having a volume of three hundred to five hundred (300-500) cubic centimeters. The volume of the chamber  22  is sufficient to receive a denture  84  or dentures, a denture cleaning tablet and sufficient water with which the denture cleaning tablet will react to effervesce so that pressure can build up in the chamber  22 .  FIGS. 2 ,  3  and the cross section of  FIG. 11  illustrate that the thickness of the cylindrical outer wall  12  varies between the bottom wall  16  and the open chamber end  24 . A thicker peripheral lip section  14  is formed adjacent the upper open chamber end  24 . This thicker lip section forms an upwardly facing ledge  15  that is surrounded by an even thinner receptacle base rim  17 . As will be subsequently discussed in more detail, the peripheral lip  14  and the ledge  15  will support a gasket seal  70 . The thickness of the peripheral lip  14 , which will form a continuous toroidial structure, will be sufficient to prevent deformation of the peripheral lip and ledge  15  when the chamber  22  is pressurized to at least ten (10) psi relative to ambient pressure. A dimensionally stable lip  14  is important for maintaining a gas tight seal with a simple gasket seal  70  of the type employed herein. In one representative embodiment, the thickness of peripheral lip  14  can be approximately five (5) to six (6) mm. In the preferred embodiment of this invention, a three hundred and sixty screw (360) degree thread  18  is formed on the interior of the peripheral rim  14 . 
     The thickness of the remainder, or lower part, of cylindrical outer wall  12  and of bottom wall  16  is less than the thickness of the peripheral lip  14 . One reason for employing thinner wall sections  12  and  16  is to reduce the amount of material needed to fabricate the receptacle base  10  and to reduce the cycle time for molding these parts. A thinner wall section will also cool quicker, and should prevent formation of flaws or warping in the plastic as it cools. A thinner base section will also tend to relieve stress in the base that might otherwise tend to deform the sealing rim. Although it would be possible to fabricate the entire receptacle base  10  with a thickness equal to the thicker peripheral lip  14 , the fabrication would be more difficult and expensive. In one representative embodiment of this invention, the thickness of the cylindrical wall  12  and the bottom wall  14  would be 3 mm. 
     In addition to these practical advantages for using thinner wall sections, there is one functional advantage to employing thin bottom wall  16 . A thinner bottom wall will be more flexible than a thicker wall. Although dimensional stability is important for the peripheral lip  14 , it is not critical for the bottom wall, provided of course that the thickness of the bottom wall  16  is sufficient to maintain the required pressure in chamber  22 . With a thinner wall, the bottom can bow outward when the chamber  22  is pressurized. The thickness of the bottom wall  16  can be chosen so that this outward deformation is noticeable when an effective pressure is developed within chamber  22 . If an initially flat bottom wall  16  bows outwardly, the vessel  2 , under pressure, will not longer sit flat on a horizontal surface. The user can then tell if an effective pressure has been developed in chamber  22  and if the denture treatment apparatus is functioning properly. A simple level-detecting device may even be added on the exterior of the receptacle base  10 , so that a user can easily detect if the device continues to function properly. 
     A representative embodiment of the cover  30  is shown in  FIGS. 5 and 6 . The cover  30  includes a disk section  32  with an annular wall  34  extending around the periphery of the disk  32 . The exterior face  38  of cover  30  faces upward and an interior face  40  faces downward and will form the upper surface of the chamber  22  when closed. A cover peripheral lip  46  extends outwardly from the annular wall  34  and forms a downwardly facing ledge  45 , which will engage a gasket seal  70 , which will be positioned between the cover ledge  45  and the receptacle base ledge  15  when the cover  30  is mounted on the receptacle base  10 . The cover peripheral lip  46  has a thickness that is greater than the thickness of the annular wall  34  or the cover disk  32 , and the cover peripheral lip  46  will not deform when the chamber  22  is pressurized. A plurality of strengthening ribs  44  radiate outwardly from the center of the cover disk  32  to the cover peripheral lip  26  and a series of pie shaped segments  48  are formed between the strengthening ribs  44 . A hub  49  is formed at the center of the radiating strengthening ribs  44 . The center of this hub  49  can be removed or taped so that a cover handle  50  may be mounted on the cover  30 . The cover  30 , including the disk  32 , the annular wall  34 , the peripheral lip  42  and the strengthening ribs  44  can be molded as an integral one-piece member. Threads  36  may be formed on the exterior of the annular wall  34 . Cover threads  36  will mate with receptacle base threads  18 , when the cover  30  is twisted onto or off of the receptacle base  10 . Threads  36  extend completely around the annular wall  46  for 360 degrees for continuous engagement around the pressure containment cavity or chamber to avoid warping. 
     The cover handle  50  is molded separately from the cover  30 , and the cover handle  50  is subsequently attachable to the cover  30  at a center pivot point  62 . Details of cover handle  50  are shown in  FIGS. 7-9 . Cover handle  50  can be injection molded as a one-piece component. Cover handle  50  includes a center post  52  that is employed to mount the handle  50  to the hub  49  at the center of the cover  30 . As shown in the cross sectional view of  FIG. 11 , a hole  54  extends upwardly from the bottom of the center post  52 . As molded this hole  54  is closed at one end, but when a tapping screw is used to attach that cover handle  50  to the cover, the tapping screw will puncture the closed section and will extend through hole  54 . 
     The mechanical advantage provided by the handles  20  and  50  is also important because the lubricity of the seal may be adversely affected by the action of the denture cleaning tablet, making it otherwise difficult to open the cover  30 . Not only must the gasket seal  70  have sufficient lubricity to permit opening and closing, and be capable of withstanding a pressure differential, but the vessel  2  still must be opened after the denture is cleaned, even if there are adverse effects on the seal  70  over time. 
     A relatively thin section is formed next to the center post  52  and this thin section will form a flexible hinge  58  between the center post  52  and a wedge section  56 . The sides of the wedge section  56  are tapered so that the wedge section  56  can fit in any one of the segments  48  defined between the strengthening ribs  44  on cover  30 . A grip section  60  extends outwardly from the wedge section  56 . This hinge  58  is sufficiently flexible and has enough clearance so that the cover handle can be rotated upwardly by a sufficient distance so that the wedge section  56  can clear the cover strengthening ribs  44 . The cover handle  50  can then be rotated about the center pivot point  62  so that the wedge section  56  can be inserted in any of the segments  48 . When the handle  50  is returned to its normal position, the wedge section  56  will fit within the selected segment and will engage the sides of strengthening ribs  44 . Rotation of the shiftable cover handle  50 , in either the clockwise or counterclockwise direction will twist the cover  30  relative to the receptacle base  10 , which remains stationary because the user is simultaneously gripping receptacle base handle  20 . Angular adjustment of the cover handle  50  in this manner makes it easier to orient the cover handle  50  relative to the receptacle base handle  20  so that it will be easier to twist or rotate the cover  30  between the closed and open positions. This will be of special importance when a user, who may have arthritic hands or may have lost grip strength, attempts to close the cover and compress the seal  70 . He or she can choose the most convention orientation of the cover handle  50  relative to the receptacle base handle  10 , and can even adjust the cover handle  50  is a ratchet-like fashion when manipulating the cover  30 . 
     A gasket seal  70  is shown in  FIG. 10 . This seal  70  comprises an annular elastomeric member that will be compressed as the cover  30  is screwed onto the receptacle base  110 . Gasket seal  70  has a flat cross section and can be fabricated from a material such as silicone or Teflon impregnated flexible acrylic. It should be understood that seals having other shapes, such as a circular cross section, could be employed, but it has been found that a seal having the configuration shown in  FIG. 10  is both economical and effective. The cover  30  is screwed to the receptacle base  10  by mating screw threads  18  that extend completely around the periphery of both the receptacle base  10  and the cover  30  so that an essentially uniform pressure will be applied to compress the gasket seal  70 . 
     Compression of the gasket seal between the cover  30  and the receptacle base will to some extent reduce the volume of the chamber  22 . The cover  30  acts as a press. Once the bottom of the gasket seal  70  fully engages the flat ledge  14 , under pressure produced by screwing in the cover  30 , the fluid in the chamber  22  is trapped and pressure within the chamber  22  begins to increase due to the effervescence of the cleaning tablet. As the cover  30  is screwed tighter, the gasket seal  70  is flattened. Approximately 2 to 3 psi can be generated by flattening the gasket seal  70 . Thus a mechanical means can employed to increase the pressure within and enclosed chamber, and to some extent the effectiveness of a denture treating agent in the chamber can be enhanced. A thicker gasket seal  70  would result in even greater pressure, but continued compression of the gasket seal  70  can result in extra drag, making it more difficult to open and close the cover  30 . The lip  17  extending around the periphery of the ledge  17  will, however, trap or capture the gasket seal  70  and will resist excessive compression of the gasket seal  70 , and will therefore limit damage to the seal  70  as well as preventing excessive drag, which would make it more difficult for a user, especially an elderly user to open and close the vessel. 
       FIG. 11  is a cross sectional view of the denture treating apparatus  2  showing the assembled components, including the receptacle base  10 , the cover  30 , the cover handle  50  and the seal  70 . For illustrative purposes the tapping screw attaching the cover handle  50  to the cover  30  is not shown. The cover  30  and the cover handle  50  are shown in their “as molded” state. It should be understood that a tapping screw or other means can be employed to puncture the closed portion of the center handle post  52  and puncture the cover within the hub  49  to hold the center post  52  on the center pivot position so that the cover handle can rotate relative to the cover as previously discussed. As shown in  FIG. 11 , the receptacle base peripheral rim  14  and the cover peripheral rim  46  are both relatively thick in comparison to the remaining sections of the receptacle base  10  and the cover  30 . These rims are therefore relatively rigid and are not subject to deformation when pressure is generated within chamber  22 . The ledges  15  and  45 , engaging opposite flat sides of gasket seal  70  will therefore not deform and will uniformly compress the gasket seal  70  resulting in a gas tight as well as a fluid tight seal that can withstand a pressure of at least ten (10) psi. relative to ambient pressure on the exterior of the vessel  2 . 
     An alternate embodiment of this invention is shown in  FIGS. 12-14 . That denture treating vessel  102  employs a cover  130  that includes a holder  104  mounted on the interior face of the cover  130 . This holder  104  comprises a strap that is large enough to hold a partially exposed denture treatment tablet  80 . Conventional denture treatment tablets can have a diameter of approximately one (1) inch and a thickness of approximately one-tenth (0.1) inch. The holder  104  could be a rigid molded plastic member or an elastomeric member bonded to the cover  130 . A denture treatment tablet  80  can be inserted into holder  104  before the cover  130  is placed onto a receptacle base  110  in which the chamber  122  has been previously filled with water  82 . The denture treatment tablet  80  will then enter the water  82  only as the cover  130  is placed on the receptacle base. The cover  130  can then be quickly screwed onto the receptacle base  110 . Almost no gas effervescing from the tablet  80  (as illustrated by the bubbles shown in  FIG. 12 ) after it has been placed in the water  82  will escape the vessel  102 , and there will be little chance that sufficient overpressure is not developed in the enclosed chamber  122 .  FIG. 12  shows an embodiment in which the holder is positioned so that the denture treatment tablet  80  is in an upright position. In this way, at least a portion of the tablet  80  will enter the water  82 , even if the chamber  122  is not filled to the top. In that eventuality, the remainder of the tablet  80  would subsequently drop into the water as the reaction proceeds. 
     A second alternative embodiment is shown in  FIGS. 15-16 . This denture treating vessel  202  employs a cover  230  that includes a basket  204  mounted on the interior face of the cover  230 . This basket  204  has an opening on its side so that a denture treating tablet  80  can be inserted into the basket  204  and can be positioned so that its circular faces extend parallel to the interior face of the cover  230 . The thickness of basket  204  is only slightly larger than the thickness of the denture treating tablet  80 . In this position, the denture treating tablet  80  will not enter and react with until cover  230  is almost completely closed. There will therefore be less escape of gas emanating from the reaction of the denture treating tablet  80  and water before the cover  230  is closed than with the first two embodiments. Although the upper face of the tablet  80  may initially be flush with the interior cover face, and therefore not completely exposed to the water, the denture treatment tablet will progressively dissolve and the entire tablet will be fully exposed to the water in the chamber. 
       FIG. 17  shows still another alternate embodiment. In this version, the cover  330  includes a recess  304  extending inwardly from the interior face of cover  330 . This recess is sized so that a denture treatment tablet  80  can be located in recess  304 , before the tablet  80  is even partially immersed in water. Clips or other conventional means can be employed to retain the denture treatment tablet  80  in recess  304 . The bottom surface of the tablet  80  is substantially flush with the bottom surface of the cover  330 . With this version the tablet  80  will not enter the water until after the treads on the cover  330  engage the treads on the mating base, which would have the same shape, as base  10  or base  110 . Thus the pressure chamber would be closed before the tablet  80  entered the water. Since there would be insufficient time to develop substantial amount of effervescence, there would be even less gas lost as the cover  330  is secured to the base, resulting in the possibility of an even greater pressure rise, once the pressure chamber has been sealed. 
     The alternate embodiments of  FIGS. 12-17  show modifications to the manner in which the table will be introduced into the water. The embodiment of  FIGS. 12-14  includes a cover handle  150  that is an integral part of the one-piece cover  130 . It should be understood, however, that a shiftable cover handle, such as cover handle  50  employed with the embodiment of  FIGS. 1-11 , could also be used with these alternate embodiments. A denture treatment apparatus incorporating both a shiftable cover handle  50  and a holder  104  would have the advantages of each component, and the shiftable cover handle  50  is not shown in  FIGS. 12-17  in order not to complicate the views of these alternate embodiments. 
     Of course these alternate representative embodiments are not the only options for implementing this invention. For example, other configurations employing primarily mechanical means to reduce the volume of the chamber could be employed to increase the pressure. Other modifications would be apparent to those of ordinary skill in the art, without departing from the invention disclosed herein. It is the claims and not the specific representative embodiments, which define this invention.