Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-29
2003-06-03
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S115000, C523S117000, C523S438000, C522S077000, C522S100000, C522S109000
Reexamination Certificate
active
06573312
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
1. The present invention relates to a photo-cured dental pit and fissure sealant composition for caries prevention having improved physical and mechanical properties, and biocompatibility, and long time sustainability after operation. More specifically, the invention relates to new photo-cured dental pit and fissure sealant composition for caries prevention, i) based on the multifunctional prepolymer mixture of 2,2-bis-(4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl)propane (“Bis-GMA”) and multifunctional prepolymer formed by substituting hydrogen atoms in hydroxyl group with methacrylate groups in the Bis-GMA molecules; and ii) comprising a diluent, an inorganic filler, a photoinitiation system, and other additives.
2. Description of the Prior Art
2. Eighty-four percent (84%) of all caries occur in the dental pits and fissures of molar chewing surface, i.e., the biting surface, which occupies about 12 % of the total tooth surface. There are dental pits and fissures of various shapes, such as V-, U-, and bottleneck-shaped, in tooth biting surfaces where food residue or intraoral bacteria are deposited, and caries occur. Methods for preventing caries include prophylactic odontomy, invented in 1936, and the prophylactic filling method invented in 1965, both of which have the shortcoming of deleting tooth constitution and are no longer used. Nowadays, dental bacteria control, fluorine use, diet control, the dental pit and fissure sealing method, etc. are being used, of which the dental pit and fissure sealing method is the most recent invention.
3. A dental pit and fissure sealant fills narrow and deep pits and fissures without artificial grinding of the tooth and prevents bacteria or food residues from gathering so as to prevent caries. The dental pit and fissure sealant includes a cyanoacrylate-based sealant, a glass-ionomer cement sealant and a Bis-GMA resin-based sealant.
4. Buonocore announced in the early of 1960s that he invented a cyanoacrylate-based dental pit and fissure sealant that is effective in reducing caries. Accordingly, the cyanoacrylate-based dental pit and fissure sealant were used, but are no longer used since cyanoacrylate quickly polymerizes under moist conditions and is liable to harden so that it is difficult to obtain the satisfactory results.
5. The glass-ionomer cement dental pit and fissure sealant is chemically bonded with calcium ion component of enamel and releases fluorine -ion, which is deposited on enamel so as to prevent caries. However, this sealant bonds more weakly than resin based sealant, which bonds by means of acid corrosion. Also, it is difficult to use the sealant in bottleneck-shaped dental pits and fissures due to high viscosity and a low rate of permeation into said dental pits and fissures; whereas it is effective in V-shaped dental pits and fissures. Also, the glass-ionomer cement has a high initial solubility. Thus, if the glass-ionomer cement is contaminated by contact with moisture before being cured, the cement clinically fails. Also, if too much liquid is used to lower viscosity, the physical properties weaken. Accordingly, the viscosity should not be controlled with liquid.
6. Bis-GMA-based dental pit and fissure sealant invented by Bower is a reaction product of bisphenol A and glycidyl methacrylate. The Bis-GMA-based dental pit and fissure sealant has the advantages of good adhesive strength, low polymerization shrinkage, and intraoral cure easiness. However, because the viscosity of the Bis-GMA-based sealant is too high to permeate into dental pits and fissures, a diluent to lower the viscosity of the sealant, such as methyl methacrylate (MMA) or glycol dimethacrylate (GDMA), should be added to the Bis-GMA-based sealant. The addition of the diluent permits the Bis-GMA-based sealant to be used as the dental pit and fissure sealant. In the present invention, a reaction accelerator activates a reaction initiator and the activated reaction initiator polymerizes Bis-GMA-based dental pit and fissure sealant. In cases where the reaction accelerator is a chemical additive, the sealant is a chemically cured dental pit and fissure sealant. In cases where the reaction accelerator is a visible ray, the sealant is a photo-cured dental pit and fissure sealant. Current dental pit and fissure sealants are mostly Bis-GMA-based sealant.
7. Results from clinical tests on the use of dental pit and fissure sealants to prevent caries shows that the cyanoacrylate-based dental pit and fissure sealant exhibits a 92% reduction in biting surface caries and an 80% rate of preservation 6 months after application. Also, the results shows an 86% reduction in biting surface caries and a 71% rate of preservation 12 months after application. With the glass-ionomer cement dental pit and fissure sealant, however, only 20% of this sealant remains 6 months after application and is completely abraded after 3 years. On the other hand, Bis-GMA resin based dental pit and fissure sealant has the most reliable clinical results and has a caries prevention rate of at least 85% in portions where the sealant is preserved.
8. Bis-GMA resin-based dental pit and fissure sealant itself has high viscosity. Therefore, in order to reduce the viscosity of the sealant, a diluent is added. Bis-GMA resin-based dental pit and fissure sealants are classified as being a chemically-cured or self-cured sealants, or as photo-cured sealants depending on the curing method. Also, depending on the addition of the inorganic filler, sealants are classified as either an inorganic filler-added sealant or an inorganic filler non-added sealant. The chemically cured sealant is mostly the inorganic filler non-added sealant, and the photo-cured sealant is divided into the inorganic filler added sealant and the inorganic filler non-added sealant. The chemically cured sealant has a satisfactory permeation rate, but has the shortcomings of high water absorption, heat expansion, and abrasion. On the other hand, the inorganic filler-added sealant of the photo-cured sealant has a low permeation rate, and good physical properties, such as very low levels of water absorption, heat expansion, and abrasion.
9. A photo-cured dental pit and fissure sealant composition for caries prevention comprises an inorganic filler, such as a surface treated silica, a prepolymer of multifunctional methacrylate, a diluent, a photoinitiation system (a photoinitiator and a reductant), and other additives. The composition should meet the requirements of a viscosity low enough to permeate into a base portion of the dental pit and fissure, which provides a high caries prevention effect, the mechanical strength to support the high biting pressure generated when chewing food, an abrasion rate low enough to extend the preservation time, a coefficient of heat expansion similar to the tooth, and a polymerization shrinkage low enough to inhibit exfoliation from the tooth upon polymerization-curing. Together with its physical properties, the composition should also be the same color and gloss of the natural tooth, and provide a natural tongue-touch feeling. The dimethacrylate, 2,2-bis-(4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl)propane (Bis-GMA) is most generally used as a prepolymer of a photo-cured dental pit and fissure sealant composition for caries prevention. Bis-GMA is principally low in volatility and polymerization shrinkage. A polymer prepared from Bis-GMA has the advantages of superior strength. Thus, Bis-GMA is used as a matrix resin. U.S. Pat. No. 4,102,856, U.S. Pat. No. 4,131,729, and U.S. Pat. No. 3,730,947 and so on describe the use of Bis-GMA. Also, the dental pit and fissure sealant should permeate into the base portion of the dental pit and fissure to improve caries prevention effect, which requires the addition of a diluent, such as triethylene glycol dimethacrylate (TEGDMA). The dental pit and fissure sealant is abraded due to the chewing of food, and the brushing of and rubbing of a person's teeth. In order to provide a sealant with abrasion resistance,
Ahn Kwang-Duk
Han Dong-Keun
Jeong Jin-Hee
Dentkist Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Yoon Tae H.
LandOfFree
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