Drug – bio-affecting and body treating compositions – Dentifrices – Fluorine or fluorine compound containing
Reexamination Certificate
2001-08-13
2002-08-27
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Dentifrices
Fluorine or fluorine compound containing
C523S116000, C433S228100
Reexamination Certificate
active
06440398
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition of a novel fluoride-releasing dental amalgam restorative material, which provides the capability to reduce the possibility of secondary decay approximate to a restoration as a result of fluoride release.
BACKGROUND OF THE INVENTION
Dental amalgam is one of the oldest of restorative material for direct replacement of missing tooth structure, and is still widely used today. Since its inception at the turn of the century, little significant change has been made to its composition, with the exception of the use of high copper materials during the last quarter century. It is one of the most technique-forgiving materials, and has met with long-term clinical success. One of the problems with this material is that it has no capacity to prevent formation of secondary decay in tooth structure surrounding the restoration. There are currently other classifications of dental restorative materials in use which offer such protection as a result of the slow release of fluoride from the material surface or bulk. Glass ionomer materials are one such type material, as well as various resin based products which have fluoride incorporated either into the polymer matrix, or in the inorganic filler particles. Compared to dental amalgam, however, glass ionomers are much more technique sensitive, and do not provide as good wear resistance in areas of high occlusal force.
The prior art of amalgam restoration placement involves preparing the remaining tooth structure to provide adequate resistance and retention form for the restorative material to prevent its loss via physical dislodgment during function. Such planning is required because dental amalgam is not chemically adherent to tooth structure. After preparation of the tooth tissues, it is typical that a lining material be placed over the cut tooth to provide for an early sealing effect. Such materials as copal varnish and more recently synthetic polymers have been used. Attempts at incorporating fluoride into this sealing agent have been performed to provide for fluoride release and provision of some degree of cariostatic action. However, some of these lining materials have been shown to dissolve over time, and are replaced by corrosion products of the dental amalgam, which then help to form a seal between prepared tooth tissue and the dental amalgam restoration. Also, materials used as restorative bases to provide thermal insulation to the tooth have been manufactured with fluoride as a potential leachable product. The concept of these materials is that if fluids and bacteria should migrate to this area, fluoride would be released and result in bacterial membrane instability, resulting in cell death.
If means to prevent recurrent decay from developing in a tooth fail, the entire restoration requires removal and replacement, resulting in enlargement of the preparation through the removal of additional tooth structure. It is not uncommon that this process would be repeated more than once, if an amalgam is placed at an early age. Thus, secondary decay around an amalgam restoration necessitates a possible series of replacements, each removing more tooth structure, resulting in a greatly weakened tooth. Indeed, it has been documented that approximately 53%-58% of the reasons for replacement of existing amalgam restoration in adult patients has been attributed to secondary caries (recurrent decay). See Mjör I A,
Tandläkartdin
, 71, 552-556, (1979) and Dahl J E., et al.,
Scand. J. Dent. Res
., 86, 404-407, (1978). Replacement of existing amalgam restorations in deciduous teeth has also been highly correlated with secondary caries: 51% of the reason for amalgam replacement. See Mjör, I A., et al.,
NTF's Tidende
, 96, 109-112, (1986).
Several studies have looked at the effect of fluoride releasing amalgams on the inhibition of caries. One study used calcium fluoride as the fluoride source in amalgam alloys and observed the effects of mercury, lactic acid, and fluoride concentration on fluoride release in the amalgam alloys. Fazzi, R.,
J. of Prosthetic Dent
., 38, no. 5,526-531 (1977). Another study compared the fluoride release from a fluoride containing amalgam, a silicate cement and a glass ionomer cement. This study concluded that the silicate cement and glass ionomer cement exhibited greater fluoride release than the fluoride containing amalgam. This study also indicated that less fluoride could be extracted from the glass ionomer cement powders. See Tveit, A. B. et al,
J. of Oral Rehabilitation
, 8, no. 3,237-241, (1981). A later study by Skartveit, L., et al.,
Scandanavian journal Dent. Research
, 93, no. 5, 448-452, (1985) reported that the release of fluoride (SnF
2
) from an amalgam for a few weeks was probably sufficient to enhance remineralization.
U.S. Pat. No. Re. 32073 discloses a dental filling composition comprising a polymerizable resin binder and an inorganic glass filler which imparts opacity to X-rays.
U.S. Pat. No. 4,738,722 discloses a buffered glass ionomer cement which can be used as a base or liner under restorative materials, a luting cement and a core material for a cast restoration.
U.S. Pat. No. 5,252,121 teaches tooth restoration comprising the application of a wet glass ionomer cement on a tooth lesion and placing an improved wet amalgam restorative on the wet glass ionomer cement and hardening.
U.S. Pat. No. 5,273,574 ('574) teaches a tooth restoration comprising a layer of glass ionomer cement bonded to the tooth and a layer of amalgam disposed on the layer of glass ionomer cement. U.S. Pat. No. '574 states that it is known in the art to add a silver alloy powder to glass ionomer cements, which are subsequently used as bases for amalgam restoratives. U.S. Pat. No. '574 also states that the corrosion that occurs as a result of the silver alloy additive might be overcome by the addition of a non-corrosive additive.
Currently, there are no commercial dental amalgam restorative materials which release fluoride. Development of such a material could greatly decrease the need for use of fluoride-releasing liners and bases, which may only provide temporary protection. If the component which releases fluoride is chemically bonded to the metallic portion of the amalgam matrix, the potential for fluoride release will not be lost. Should the outer surface become abraded or worn away, there will be additional bonded glass particles at the new surface to provide for fluoride release. Also, if the glass particle leaches fluoride in increased amounts upon acidic exposure, the released fluoride is correlated with environments which are most prone to result in tooth decalcification and overt decay. An additional benefit of the system is that the leached fluoride can be replenished in the glass particle as a result of the use of a fluoride containing dentrifice or the use of a topical fluoride treatment, as is commonly performed at periodic dental hygiene appointment.
None of the above-cited documents disclose compositions or methods, which achieve the above proposed system to solve the previously discussed problems in the art, such as those claimed herein.
SUMMARY OF THE INVENTION
The above-mentioned disadvantages with respect to the potential for secondary caries of dental amalgam restorative material are overcome by the use of the present invention. Specifically, the present invention consists of combining concepts of two major families of existing dental restorative materials, amalgams and glass ionomer.
In one embodiment the invention provides a fluoride releasing dental amalgam composition comprising a dental amalgam alloy material and the glass particulate powder component of a fluoride-containing acid etchable glass ionomer cement.
In another embodiment, the invention provides a method of preventing or reducing secondary caries around an existing tooth restoration comprising the step of placing the fluoride releasing dental amalgam composition in a prepared cavity area prone to tooth decalcification and/or overt decay.
Additional advantag
Mettenburg Don
Rueggeberg Fred
Whitford Gary
MCG Research Institute Medical College of Georgia
Needle & Rosenberg P.C.
Page Thurman K.
Ware Todd D
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