Dentistry – Orthodontics – By mouthpiece-type retainer
Reexamination Certificate
1998-09-29
2001-10-09
Smith, Jeffrey A. (Department: 3732)
Dentistry
Orthodontics
By mouthpiece-type retainer
C433S008000, C433S007000, C433S002000
Reexamination Certificate
active
06299438
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of dental articles, such as orthodontic archwires and brackets. More specifically, the invention relates to dental articles and brackets having a hard metallic friction-reducing coating.
BACKGROUND OF THE INVENTION
Orthodontic tooth movement in mechanotherapy depends on the ability of a clinician to use controlled mechanical forces to stimulate biologic responses within the paradental tissues surrounding the roots of treated teeth. The most common orthodontic technique consists of an edgewise bracket that slides along an archwire. The sliding arch-guided system, or sliding mechanics, can be influenced by counteracting frictional forces at the interface of the bracket, archwire, and ligature. Thus, the basic principle of orthodontic appliances in the continuous archwire technique is to apply mechanical forces on teeth so that movement will occur in every desirable spatial direction. The forces are applied during the various stages of treatment by a variety of appliances, which include several kinds of archwire, ligatures, and bands.
Friction among appliances used for orthodontic correction of teeth is recognized by clinicians as a hindrance to tooth movement. Friction reduces the effective force, which is applied to the tooth from the wire. In the case of sliding mechanics, excessive friction, brought about by the angle between the wire and the slot of the bracket, slows tooth movement down substantially or even halts it. It would be of great clinical advantage to minimize this friction so that the clinician can accurately estimate the amount of force transmitted to each tooth. Unimpeded tooth movement would reduce the time needed for treatment, thereby reducing the risks of adverse effects of wearing orthodontic braces on the teeth and surrounding tissues. It would be desirable to minimize the effect of any factors over which a clinician has no control, including the amount of friction between the archwire and the bracket.
There are several variables that affect the amount of friction between orthodontic appliances, most prevalent of which is the composition of the wire and bracket material. The problem of friction is compounded by the desire for aesthetically pleasing appliances such as ceramic brackets, which have greater friction toward all types of archwires than stainless steel brackets. Archwires made of beta-titanium have desirable properties such as good flexibility, spring force and biocompatibility, and are the only orthodontic wires containing no nickel. However, these materials are soft, have poor frictional characteristics and are very susceptible to adhesive wear. Orthodontic tooth movement in mechanotherapy depends on the ability of a clinician to use controlled mechanical forces to stimulate biologic responses within the tissues surrounding the roots of treated teeth, most commonly by way of an edgewise bracket sliding along an archwire. Frictional forces at the interface of the bracket, archwire, and ligature can hinder these sliding mechanics.
The friction coefficients between bracket and various wire materials have been measured extensively. Wires made out of such popular shape memory materials such as titanium-molybdenum alloy (TMA) and Ni—Ti (nickel-titanium) alloys tend to be softer than stainless steel and tend to have higher coefficients of friction against stainless steel than does stainless steel itself, which has a high coefficient of friction. This is true particularly at high (~80 N) normal forces.
Coating thin films of various materials onto archwires has been previously suggested as a way to reduce friction and to improve their aesthetic appearance. U.S. Pat. No. 5,288,230 to Nikutowski et al. describes applying a coating of diamond-like carbon (DLC) onto archwires to serve as a barrier to diffusion of nickel and chromium from the wire, which causes allergic reactions in the patient. The DLC coatings also provide a hard, friction-reducing surface. The appearance of the DLC films, however, ranges from black to interference rainbow colors, and is not aesthetically pleasing. U.S. Pat. No. 5,454,716 to Banerjee et al. describes a coating of a plastic-ceramic composite, which is aesthetically pleasing, but is susceptible to localized abrasion over time.
Ion implantation has been used to modify orthodontic materials with the goal of reducing friction. For example, alumina, which is a commonly used ceramic in bracket manufacture, has been implanted with titanium with a resulting decrease in its coefficient of friction with beta-titanium wire. (Kusy et al.,
Dental Material
8:167-172, 1992). Friction reduction was observed for alumina flats coated with DLC. (R. P. Kusy et al., (1993) J. Am. Ceram. Soc., 76[2], 336-342 Implantation of beta-titanium wires with nitrogen reduced the friction due to formation of hard titanium oxy-nitride on the wire. (R. P. Kusy et al., Nanda, 215-221 (1993); R. P. Kusy et al., Dental Mater., 8, 167-172 (1992); R. P. Kusy et al., (1993) J. Am. Ceram. Soc., 76[2], 336-342).
SUMMARY OF THE INVENTION
The present invention relates to dental articles having improved properties and to systems and methods for coating dental articles to improve their mechanical and physical properties. The dental articles of the present invention generally comprise metal and/or ceramic articles designed for temporary or permanent placement in the mouth having a hard friction-reducing coating. The article further may comprise at least one interlayer between the article and the outer, friction-reducing coating. In some embodiments of the invention, the presence of the interlayer improves adhesion of the outer, friction-reducing layer to the surface of the article.
The articles may comprise, for example, orthodontic devices such as archwires, brackets, retainers and palate expanders. The adhesion layer comprises any metallic material which has the effect of improving adhesion of the outer, friction-reducing layer to the article. The friction reducing coating comprises a biocompatible metallic or ceramic coating capable of reducing the surface friction of the coated article (compared to the uncoated article) so that pieces of the dental article which are connected together and cooperate with each other, e.g., archwires and brackets, can slide past each other more easily, thereby allowing for easier and more precise adjustment by the orthodontist or dentist. The coating preferably also has the properties of being resistant to mechanical wear and sufficiently inert to resist degradation in the harsh environment of the mouth.
The method of the invention generally comprises applying a friction-reducing coating to a metal and/or ceramic dental article. In a preferred embodiment of the present method, the article first is coated with an adhesion layer or interlayer, followed by deposition of an outermost, friction-reducing coating. The adhesion layer can be any metallic material which has the effect of improving the bonding of the outer, friction-reducing layer to the substrate. The adhesion layer and the friction reducing coating may be applied by any technique which is useful for depositing metallic and/or ceramic coatings onto metallic or ceramic substrates, for example, sputtering, chemical vapor deposition, ion beam enhanced deposition, plasma-assisted vapor deposition, cathodic arc deposition, ion implantation and evaporation.
The continuous coating on the article reduces adhesive wear and friction on the article, and the frictional and wear properties of the article thus are significantly improved.
REFERENCES:
patent: 4197643 (1980-04-01), Burstone et al.
patent: 4626209 (1986-12-01), Tsai et al.
patent: 4818226 (1989-04-01), Berendt et al.
patent: 4902224 (1990-02-01), Collins et al.
patent: 4946387 (1990-08-01), Adell
patent: 5032080 (1991-07-01), Hakansson et al.
patent: 5080584 (1992-01-01), Karabin
patent: 5167499 (1992-12-01), Arndt et al.
patent: 5167500 (1992-12-01), Miura
patent: 5232361 (1993-08-01), Sachdeva et al.
patent: 5288230 (1994-02-01), Nikutowski et al
Armini Anthony J.
Sahagian Richard
Foley Hoag & Eliot LLP
Implant Sciences Corporation
Smith Jeffrey A.
LandOfFree
Orthodontic articles having a low-friction coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Orthodontic articles having a low-friction coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Orthodontic articles having a low-friction coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2555108