Orthodontic Appliance with Reduced Resistance to Sliding

Abstract

The present invention relates to an improved orthodontic bracket mountable on a tooth surface for use in orthodontic mechanics to facilitate movement of teeth along an arch defined by the shape of an arch wire. This orthodontic bracket appliance of the invention provides reduced resistance to sliding during orthodontic tooth movement by incorporating rotating members within the arch wire channel or tube to reduce friction.

Claims

1. An orthodontic device comprising: a baseplate having a top surface and a bottom surface; two at least approximately rectilinear elongated channel wall members having a width, W, a height, H, and a depth, D, wherein one face of each of said members, defined by dimensions W and D (face WD) is attached to the top surface of the baseplate; and wherein said members are each attached to said baseplate such that a separate face of each of the two members, defined by the dimensions W and D (face WD), face one another and are at least approximately parallel and spaced apart by a distance, M, so as to form a channel therebetween, said channel being defined by a portion of the top surface of said baseplate and by the two faces defined by the dimensions H and D of said elongated members (face HD), such that said channel has a volume approximately equal to DHM and such that the channel has a first end and a second end and a top, each of which is not enclosed; and four at least approximately cylindrical rollers, each having a longitudinal axis through the center point of the two at least approximately circular faces of said cylindrical rollers; wherein each of said cylindrical rollers is positioned at least partially within said channel and each is placed such that its longitudinal axis is at least approximately perpendicular to said top face of said baseplate; and wherein two of said cylindrical rollers are each positioned partially within first and second recesses in said face HD of one of said channel wall members, the first said recess approximate at the first end of said channel and the other recess approximately at the second end of said channel; and wherein the other two of said cylindrical rollers are each positioned partially within third and fourth recesses in said face HD of the other said channel wall member, the third said recess approximate at the first end of said channel and the fourth recess approximately at the second end of said channel; and wherein the two said cylindrical rollers approximately at the first end of said channel are separated by a distance, N1, and the other two said cylindrical rollers at the second end of said channel are separated by a distance, N2, where N1 and N2 are each less than said distance M and may be equal or not equal; and wherein one end of each of said cylindrical rollers is positioned in a respective hole in said baseplate; and wherein the other end of each of said cylindrical rollers is positioned partially within said recesses in said face HD of said channel wall members; and wherein said holes and said recesses have dimensions to provide support for said cylindrical rollers to at least approximately maintain the position of said cylindrical rollers while allowing said cylindrical rollers to rotate about their respective longitudinal axes.

2. The orthodontic device of claim 1, wherein said device further comprises an adhesion pad attached to the bottom face of said base plate.

3. The orthodontic device of claim 1, wherein said holes in said baseplate extend from the top surface of the baseplate to the bottom face of the baseplate.

4. The orthodontic device of claim 1, wherein said holes are approximately cylindrical.

5. The orthodontic device of claim 1, wherein said holes are approximately square in cross section.

6. The orthodontic device of claim 1, wherein said recesses are approximately circular in cross section

7. The orthodontic device of claim 1, wherein said recesses are approximately rectangular in cross section.

8. The orthodontic device claim 1, wherein said cylinders are hollow tubes.

9. The orthodontic device of claim 1, wherein said cylinders are solid.

10. The orthodontic device of claim 1, wherein said cylinders are coated with a low friction material.

11. The orthodontic device of claim 10, wherein said low friction material is chosen from the group consisting awl Teflon, parylene, and a fluoropolymer.

12. The orthodontic device of claim 1 wherein said baseplate, elongated members, and cylindrical rollers are composed of metal.

13. The orthodontic device of claim 12 herein said baseplate, elongated members, and cylindrical rollers are independently composed of stainless steel.

14. The orthodontic device of claim 1 wherein said baseplate, elongated members, and cylindrical rollers are independently composed of titanium.

15. The orthodontic device of claim 1 wherein said baseplate, elongated members, and cylindrical rollers are independently composed of ceramic material.

16. The orthodontic device of claim 1 wherein said dimensions L, H, D, M, and N are each less than 5 millimeters.

17. The orthodontic device of claim 1 wherein said dimensions L, H, D, M, and N are each less than 3 millimeters.

18. The orthodontic device of claim 1 wherein said dimensions L, H, D, M, and N are each less than 2 millimeters.

19. The orthodontic device of claim 1 wherein said device further comprises an arch wire retained in said sliding channel.

20. The orthodontic device of claim 19 wherein said arch wire has a circular cross section.

21. The orthodontic device of claim 19 wherein said arch wire has a rectangular cross section.

22. The orthodontic device of claim 19 wherein said arch wire has an oval cross section.

23. An orthodontic device comprising a metal bracket comprising at least one cylindrical roller at least partially defining a sliding channel for an arch wire, wherein said cylindrical roller is retained in position by said metal bracket and is free to rotate about its longitudinal axis.

24. The orthodontic device claim 23, wherein said orthodontic device further comprises an adhesion pad attached to the bottom face of said bracket.

25. The orthodontic device claim 23, wherein said cylinders are hollow tubes.

26. The orthodontic device of claim 23, wherein said cylinders are solid.

27. The orthodontic device of claim 23, wherein said cylinders are coated with a low friction material.

28. The orthodontic device of claim 27, wherein said low friction material is chosen from the group consisting awl Teflon, parylene, and a fluoropolymer.

29. The orthodontic device of claim 23 wherein said device further comprises an arch wire retained in said bracket.

30. The orthodontic device of claim 29 wherein said arch wire has a circular cross section.

31. The orthodontic device of claim 29 wherein said arch wire has a rectangular cross section.

32. The orthodontic device of claim 29 wherein said arch wire has an oval cross section.

33. A method for adjusting the position of teeth in a person, the method comprising: attaching one or more orthodontic devices to one or more teeth of the person, said orthodontic device comprising: a baseplate having a top surface and a bottom surface; two at least approximately rectilinear elongated channel wall members having a width, W, a height, H, and a depth, D, wherein one face of each of said members, defined by dimensions W and D (face WD) is attached to the top surface of the baseplate; and wherein said members are each attached to said baseplate such that a separate face of each of the two members, defined by the dimensions W and D (face WD), face one another and are at least approximately parallel and spaced apart by a distance, M, so as to form a channel therebetween, said channel being defined by a portion of the top surface of said baseplate and by the two faces defined by the dimensions H and D of said elongated members (face HD), such that said channel has a volume approximately equal to DHM and such that the channel has a first end and a second end and a top, each of which is not enclosed; and four at least approximately cylindrical rollers, each having a longitudinal axis through the center point of the two at least approximately circular faces of said cylindrical rollers; wherein each of said cylindrical rollers is positioned at least partially within said channel and each is placed such that its longitudinal axis is at least approximately perpendicular to said top face of said baseplate; and wherein two of said cylindrical rollers are each positioned partially within first and second recesses in said face HD of one of said channel wall members, the first said recess approximate at the first end of said channel and the other recess approximately at the second end of said channel; and wherein the other two of said cylindrical rollers are each positioned partially within third and fourth recesses in said face HD of the other said channel wall member, the third said recess approximate at the first end of said channel and the fourth recess approximately at the second end of said channel; and wherein the two said cylindrical rollers approximately at the first end of said channel are separated by a distance, N1, and the other two said cylindrical rollers at the second end of said channel are separated by a distance, N2, where N1 and N2 are each less than said distance M and may be equal or not equal; and wherein one end of each of said cylindrical rollers is positioned in a respective hole in said baseplate; and wherein the other end of each of said cylindrical rollers is positioned partially within said recesses in said face HD of said channel wall members; and wherein said holes and said recesses have dimensions to provide support for said cylindrical rollers to at least approximately maintain the position of said cylindrical rollers while allowing said cylindrical rollers to rotate about their respective longitudinal axes, and affixing an arch wire to said one or more orthodontic devices within said channel of each orthodontic device such that said orthodontic devices attached to said teeth are able to slide longitudinally along said arch wire.

34-54. (canceled)

55. A method for adjusting the position of teeth in a person, the method comprising: attaching one or more orthodontic devices to one or more teeth of the person, said orthodontic device comprising: a metal bracket comprising at least one cylindrical roller at least partially defining a sliding channel for an arch wire, wherein said cylindrical roller is retained in position by said metal bracket and is free to rotate about its longitudinal axis, and affixing an arch wire to said one or more orthodontic devices such that said orthodontic devices attached to said teeth are able to slide longitudinally along said arch wire.

56-63. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings

[0065] FIG. 1 is an exploded view of one embodiment of the bracket of the invention.

[0066] FIG. 2 is the bracket of FIG. 1 in its non-exploded configuration.

[0067] FIG. 3 is a perspective view of an orthodontic bracket with holes through the base parallel to the walls of the bracket slot according to one embodiment of the invention.

[0068] FIG. 4 is a perspective view of the orthodontic bracket shown in FIG. 3 with rods inserted into the holes;

[0069] FIG. 5 is a view showing the bottom of the orthodontic bracket in FIG. 4.

[0070] FIG. 6 is a perspective top view of the orthodontic bracket with rods shown in FIG. 1 with an archwire inserted into the bracket slot;

[0071] FIG. 7 is a perspective view illustrating a different embodiment of the invention wherein a bracket is constructed similarly to the orthodontic bracket in FIG. 1 but with holes and rods parallel to the floor of the bracket.

[0072] FIG. 8 is a perspective view illustrating a bracket constructed similarly to the orthodontic bracket in FIG. 1 but with the bracket slot covered with a ceiling in accordance with another embodiment of the invention.

[0073] FIG. 9 shows the dependence of the resistance to sliding on the degree of tip of the bracket (bracket angulation) for the combined data from the four bracket types tested.

[0074] FIG. 10 is a chart showing a comparison of the bracket of the invention (Novel Bracket) to the 3M bracket with regard to resistance to sliding.

DETAILED DESCRIPTION OF THE INVENTION

[0075] The present invention is directed to an orthodontic bracket including a bracket base, at least one archwire slot formed in the base adapted to receive and archwire therein, and means for incorporating rotating members into the walls, corners, floor or ceiling of the archwire slot so as to allow for reduced binding and friction as an archwire slides within the archwire slot. The archwire slot is defined by sidewalls disposed on either side of the slot.

[0076] In one embodiment of the invention, the bracket consists of a base plate having a top surface and a bottom surface. The bottom surface of the base plate is generally used to adhere the bracket to the teeth of the patient. On the top surface of the base plate are at least two elongated rectilinear members arranged to form a channel therebetween, the members and base plate adapted to receive an archwire. In use, brackets are placed on several of the patient's teeth, each bracket adapted to receive the archwire. The bracket is adapted to allow the archwire to be movably retained with in the channel such that the teeth can move along the path defined by the archwire the brackets are generally further adapted to allow retaining elements to be attached to the bracket, for example, elastic bands. The present invention provides an improved orthodontic bracket which comprises movable rollers with in the archwire channel to allow movement of the bracket relative to the archwire with reduced friction.

[0077] In a preferred embodiment of the invention the bracket is a monolithic device fabricated from metal. To aid the description of the bracket, the bracket will be described as if it were composed of separate components, although the bracket is preferably a monolithic device. The structure of the monolithic bracket consists of a base plate having two surfaces as shown in FIG. 1. The bottom surface 102 is used for attachment to the tooth, and the top surface 105 is adapted to define an archwire channel 110 defined by two elongated channel wall members 115 formed on the top surface of the base plate 100. The base plate contains four or more circular holes 120 passing through the base plate from the top surface to the bottom surface. The holes in the base plate are adapted to receive rollers 130 which are generally cylindrical in shape and have a length which is greater than the thickness 104 of the base plate. The rollers thus protrude above the top surface of the base plate. The elongated channel wall members which, together with the top surface of the base plate, define the archwire channel. The elongated channel wall members contain recesses 108, which may be rectangular, square, semicircular or quarter-circular in cross section, and are adapted to receive the protruding end of the rollers. The geometric arrangement of the holes, the elongated channel wall members, and the rollers is such so as to form a sliding channel for the archwire which is slightly narrower than the channel defined by the channel wall members themselves. The holes in the base plate and the recesses in the channel wall members are dimensioned so as to support and retain the rollers while allowing the rollers to rotate around their longitudinal axis. In practice, the archwire will generally be slightly narrower than the width of the sliding channel defined by the rollers of the bracket apparatus. The apparatus of the invention thereby forms an orthodontic bracket which will allow [the movement of the bracket and the archwire relative to one another with reduced friction allowed by the movement of the rollers around their longitudinal axes.

[0078] In another embodiment of the invention, the elongated wall channel members further contain protrusions 117 which are adapted to retain elastic bands used in the orthodontic process. In practice, the elastic bands are retained by protrusions on one elongated channel wall member and by protrusions on the second channel wall member, thereby retaining the archwire with in the sliding channel.

[0079] In a further embodiment of the invention, the bracket is adapted to comprise a hinged top plate to retain the archwire within the sliding channel. The top plate is in hingeably attached to one of the channel wall members and/or the base plate so as to allow the top plate to be closed over the sliding channel following insertion of the archwire into the bracket's sliding channel. Once closed, the top plate forms an upper surface for the sliding channel. Generally, the bracket of this embodiment will further comprise a mechanism to latch the top plate in its closed position. Such top plates hingeably attached to orthodontic brackets are known to those skilled in the art, as are latching mechanisms to retain the hinged top plate in its closed position. Brackets of the present invention comprising the hinged top plate do not require elastic bands to retain the archwire within the sliding channel.

[0080] In another embodiment of the invention, the orthodontic bracket may further comprise an attachment plate 140 beneath and attached to the bottom surface of the base plate. The attachment plate is adapted, to provide improved adhesion to the patient's tooth. The attachment plate may be adapted with physical protrusions, surface roughness features, and/or chemical surface modification to allow improved adhesion to the tooth using and adhesive material. Advantageously, the attachment plate will further aid in retaining the rollers in their proper position by closing the bottom end of the holes in the baseplate.

[0081] In a further embodiment of the invention the rollers may be comprised of solid metal, hollow tubes of metal, or of solid rigid plastic. Examples of solid rigid plastic include polycarbonate, nylon, polyester, ABS, poly methyl methacrylate, and, composite plastic materials.

[0082] In yet another embodiment of the invention, the surfaces of the rollers may be coated with a thin layer of a low friction material. Examples of such low friction materials which may be employed in the invention include Teflon, fluorinated polymers, parylene, and polyimide.

[0083] In a further embodiment of the invention, the bracket may comprise greater than four rollers, with their associated holes in the baseplate and recesses in the channel wall members.

[0084] The orthodontic brackets of the present invention are manufactured by any of several techniques known in the art for fabricating small metal or plastic devices. For example, brackets are fabricated using an automated CNC mill. The holes in the bracket are drilled in a separate process into the bottom of the bracket material block prior to machining of the remainder of the bracket. Once drilled, the bracket material block is positioned in the CNC mill and the remaining features are machined from the bracket material block.

[0085] The rollers of the bracket may be machined from metal rod or metal tubing. Such metal rod and metal tubing can be purchased commercially and can be purchased with friction reducing materials on the rod or tubing surfaces.

[0086] The brackets of the present invention can also be fabricated using 3-D printing techniques as are well known in the art. The brackets are designed, drawn, and defined dimensionally using computer aided drafting (CAD) software. Electronic files containing the bracket design are transferred to the 3-D printing machine. The 3-D printer then, builds the bracket by printing thin layers of polymer, or metal, one on top of another. The dimensions of each layer of the material are altered so as to create a three-dimensional object, one layer at a time. The bracket of the present invention is printed using a three-dimensional printer having the ability to print two different materials. The material of the bracket is printed layer by layer along with non-bracket material such that all voids in each layer are filled with non-bracket material. Each layer, thus has a planar surface upon which the next layers may be deposited. Overhanging protrusions of the bracket material can thus be printed on top of non-bracket material which provides support for the bracket material during manufacture. The two-material 3-D printing is used to print the brackets of the present invention where in the recesses in the channel wall members are enclosed at the top of the recess. During 3-D printing, the non-bracket material fills the recess area of each layer. The top layer of the non-bracket material thus supports the first layer off the top of the recess area printed with the bracket material. Following printing, the completed bracket is separated from the non-bracket material.

[0087] The rollers are cut to length from longer rods or tubing using machining techniques familiar to those skilled in the art. The rollers are inserted into the holes of the bracket from the bottom. The optional adhesion plate may then be attached to the bottom of the bracket, conveniently retaining the rollers within the bracket structure, yet free to rotate about their longitudinal axis.

[0088] FIGS. 3 through 8 show various embodiments of the bracket of the invention. FIG. 7 shows one preferred embodiment of the bracket where the bracket comprises six rollers. The two additional rollers are in the floor of the archwire slot to further reduce friction of the archwire to the bracket.

[0089] FIG. 9 shows an additional embodiment of the invention where the archwire slot is covered by a ceiling plate to help keep the archwire in the archwire channel.

[0090] In one embodiment of the invention, the orthodontic device comprises a baseplate having a top surface and a bottom surface; two at least approximately rectilinear elongated channel wall members having a width, W, a height, H, and a depth, D, wherein one face of each of said members, defined by dimensions W and D (face WD) is attached to the top surface of the baseplate; and wherein said members are each attached to said baseplate such that a separate face of each of the two members, defined by the dimensions W and D (face WD), face one another and are at least approximately parallel and spaced apart by a distance, M, so as to form a channel therebetween, said channel being defined by a portion of the top surface of said baseplate and by the two faces defined by the dimensions H and D of said elongated members (face HD), such that said channel has a volume approximately equal to DHM and such that the channel has a first end and a second end and a top, each of which is not enclosed; and four at least approximately cylindrical rollers, each having a longitudinal axis through the center point of the two at least approximately circular faces of said cylindrical rollers; wherein each of said cylindrical rollers is positioned at least partially within said channel and each is placed such that its longitudinal axis is at least approximately perpendicular to said top face of said baseplate; and wherein two of said cylindrical rollers are each positioned partially within first and second recesses in said face HD of one of said channel wall members, the first said recess approximate at the first end of said channel and the other recess approximately at the second end of said channel; and wherein the other two of said cylindrical rollers are each positioned partially within third and fourth recesses in said face HD of the other said channel wall member, the third said recess approximate at the first end of said channel and the fourth recess approximately at the second end of said channel; and wherein the two said cylindrical rollers approximately at the first end of said channel are separated by a distance, N1, and the other two said cylindrical rollers at the second end of said channel are separated by a distance, N2, where N1 and N2 are each less than said distance M and may be equal or not equal; and wherein one end of each of said cylindrical rollers is positioned in a respective hole in said baseplate; and wherein the other end of each of said cylindrical rollers is positioned partially within said recesses in said face HD of said channel wall members; and wherein said holes and said recesses have dimensions to provide support for said cylindrical rollers to at least approximately maintain the position of said cylindrical rollers while allowing said cylindrical rollers to rotate about their respective longitudinal axes.

[0091] In another embodiment, the orthodontic device further comprises an adhesion pad attached to the bottom face of said base plate.

[0092] In still another embodiment of the orthodontic device said holes in said baseplate extend from the top surface of the baseplate to the bottom face of the baseplate.

[0093] In one preferred embodiment of said orthodontic device, said holes are approximately cylindrical or square in cross-section.

[0094] In a particularly preferred embodiment of the orthodontic device, said recesses are approximately circular in cross section or are approximately rectangular in cross section.

[0095] In other preferred embodiments of the orthodontic device, the cylinders are hollow tubes or are solid, or are coated with a low friction material such as Teflon, parylene, or a fluoropolymer.

[0096] In other preferred embodiments of the orthodontic device, the baseplate, elongated members, and cylindrical rollers are composed of metal, most preferably stainless steel or titanium.

[0097] In another embodiment, the baseplate, elongated members, and cylindrical rollers are independently composed ceramic material.

[0098] In a preferred embodiment of the orthodontic device, the dimensions L, H, D, M, and N are each less than 5 millimeters.

[0099] In a more preferred embodiment of the orthodontic device, the dimensions L, H, D, M, and N are each less than 3 millimeters.

[0100] In a particularly preferred embodiment of the orthodontic device, the dimensions L, H, D, M, and N are each less than 2 millimeters.

[0101] In yet another embodiment of the orthodontic device, the device further comprises an arch wire retained in said sliding channel.

[0102] In a more preferred embodiment of the orthodontic device, the arch wire has a circular cross section or a rectangular cross section, or an oval cross section.

[0103] In a preferred embodiment of the orthodontic device, the orthodontic device comprises a metal bracket comprising at least one cylindrical roller at least partially defining a sliding channel for an arch wire, wherein said cylindrical roller is retained in position by said metal bracket and is free to rotate about its longitudinal axis.

[0104] The invention herein described also includes a method for adjusting the position of teeth in a person, where the method comprises attaching one or more of the orthodontic devices described herein in any of the embodiments described, to one or more teeth of the person, said orthodontic device comprises a baseplate having a top surface and a bottom surface; two at least approximately rectilinear elongated channel wall members having a width, W, a height, H, and a depth, D, wherein one face of each of said members, defined by dimensions W and D (face WD) is attached to the top surface of the baseplate; and wherein said members are each attached to said baseplate such that a separate face of each of the two members, defined by the dimensions W and D (face WD), face one another and are at least approximately parallel and spaced apart by a distance, M, so as to form a channel therebetween, said channel being defined by a portion of the top surface of said baseplate and by the two faces defined by the dimensions H and D of said elongated members (face HD), such that said channel has a volume approximately equal to DHM and such that the channel has a first end and a second end and a top, each of which is not enclosed; and four at least approximately cylindrical rollers, each having a longitudinal axis through the center point of the two at least approximately circular faces of said cylindrical rollers; wherein each of said cylindrical rollers is positioned at least partially within said channel and each is placed such that its longitudinal axis is at least approximately perpendicular to said top face of said baseplate; and wherein two of said cylindrical rollers are each positioned partially within first and second recesses in said face HD of one of said channel wall members, the first said recess approximate at the first end of said channel and the other recess approximately at the second end of said channel; and wherein the other two of said cylindrical rollers are each positioned partially within third and fourth recesses in said face HD of the other said channel wall member, the third said recess approximate at the first end of said channel and the fourth recess approximately at the second end of said channel; and wherein the two said cylindrical rollers approximately at the first end of said channel are separated by a distance, N1, and the other two said cylindrical rollers at the second end of said channel are separated by a distance, N2, where N1 and N2 are each less than said distance M and may be equal or not equal; and wherein one end of each of said cylindrical rollers is positioned in a respective hole in said baseplate; and wherein the other end of each of said cylindrical rollers is positioned partially within said recesses in said face HD of said channel wall members; and wherein said holes and said recesses have dimensions to provide support for said cylindrical rollers to at least approximately maintain the position of said cylindrical rollers while allowing said cylindrical rollers to rotate about their respective longitudinal axes, and affixing an arch wire to said one or more orthodontic devices within said channel of each orthodontic device such that said orthodontic devices attached to said teeth are able to slide longitudinally along said arch wire.

[0105] In another preferred method, comprising a method for adjusting the position of teeth in a person, the method comprises attaching one or more orthodontic devices to one or more teeth of the person, said orthodontic device comprises a metal bracket comprising at least one cylindrical roller at least partially defining a sliding channel for an arch wire, wherein said cylindrical roller is retained in position by said metal bracket and is free to rotate about its longitudinal axis, and affixing an arch wire to said one or more orthodontic devices such that said orthodontic devices attached to said teeth are able to slide longitudinally along said arch wire.

Example 1

Bracket Fabrication and Testing in Comparison to Commercial Brackets

Materials and Methods

[0106] Four types of brackets (n=10, each) were tested in this study: a conventional bracket, the Victory Series Low Profile bracket (3M Unitek, Monrovia, Calif.), a passive self-ligating bracket, the Damon Q bracket (Ormco Corp, Orange, Calif.), an active self-ligating bracket, the In-Ovation R bracket (Dentsply GAC, Bohemia, N.Y.), and the bracket of the invention as depicted in FIG. 1.

[0107] The bracket of the invention was manufactured by Micro Precision Parts Manufacturing Ltd. (Qualicum Beach, BC) via CNC-milling technique. The bracket was fitted with polytetrafluoroethylene (PTFE of Teflon) coated stainless steel rollers (Amazon Supply, Seattle, Wash.) positioned precisely at the four corners of the bracket slot (FIG. 1). The walls of the slot were recessed to prevent any contact with an inserted archwire though the rollers were positioned in such a way as to maintain the integrity of the slot dimensions and the pins were hand inserted and individually observed under a microscope to ensure movement of the Teflon roller pins was not inhibited. The Teflon pins were expected to reduce the frictional forces between the bracket and the rolling of the pins with the potential of reducing the overall binding and notching that comprises the majority of resistance to sliding.

[0108] All four bracket types had 0.22 slot widths and were made of stainless steel. The prescription differences of the brackets were non-consequential as all prescribed bracket angulations were compensated for during testing by the design of the testing jig.

[0109] The testing jig used in a previous study by Hamdan and Rock (Hamdan & Rock, 2008, European Journal of Orthodontics, 30(5), 508-514) was utilized in the present investigation by following the same protocol. The jig was custom made so that it could be clamped to a mechanical testing machine (MTS Insight 30 MTS, Eden Prairie, Minn.) and could be manipulated so that tip in 1 increments could be produced at the bracket slot of an upper canine bracket.

[0110] The jig was comprised of two parts. One part, which was firmly mounted to the jig baseplate, was designed to hold a straight wire with variable tension. The length of the test wire was set at 18.4 mm to represent the clinical wire span present during a premolar extraction case and all wires were subjected to a 300 g tensile force as recommended by Kapila et al. (Kapila, Angolkar, Duncanson Jr, & Nanda, 1990, American Journal of Orthodontics and Dentofacial Orthopedics, 98(2), 117-126).

[0111] The other half of the jig was designed to hold the bracket mounted to a stainless steel slug at varying degrees of tip. This part of the jig was hinged which allowed the mounted bracket to be brought to the mounted wire and ligated together (Figure . . . ).

[0112] In the present study, a 0.0210.025 calibration wire was inserted into the jig and tensed to 300 g as measured by the MTS Insight 30. A bracket was then ligated to the wire and a blank mounting rod was inserted into the jig. The large sized wire was used to ensure correct alignment and the removal of all tip and torque. The jig was set to 0 of tip and Transbond XT (3M Unitek, Monrovia, Calif.) light cure adhesive paste was placed on the base of the bracket and the end of the mounting rod. The hinged rod was brought to the vertical so that the composite on the mounting stub united with the composite on the base of the bracket. The bracket was positioned to lie in the center of the mounting rod and the composite was then cured by light activation for 20 seconds on either side of the bracket using a curing light. Forty brackets (n=10 each, for 4 groups) were mounted in one session on the same 0.0210.025 wire to avoid any variation between mountings.

[0113] Once the 0.0190.025 archwire was placed into the jig, cinched into place and tensed to 300 g, one of the previously calibrated brackets was then inserted and tightened into the opposing part of the jig. The hinged rod was then brought to the vertical, bringing the bracket against the wire so that it could be ligated.

[0114] A loop of 0.032 round stainless steel wire, clamped to the upper crosshead of the MTS Insight 30 testing machine was positioned under the bracket tie wings. With the bracket positioned at the bottom of the test wire, the loop was raised until it just touched the bracket so that a reading registered on the MTS Insight 30 dial. The bracket was then moved up by 3.7 mm to represent the distance between the distal edge of an upper second premolar bracket and the mesial edge of a first molar tube. Tip and torque values were then set and the MTS Insight 30 recalibrated to zero to account for the weight of the slide assembly. The initial force peak as well as the maximum and minimum forces was recorded over a wire span of 7 mm at a speed of 10 mm/min.

[0115] Each bracket was tested at 0, 2, 4, 6, and 8 of tip and the 0.0190.025 wire was replaced following each test to account for any wire bending or fatigue during the testing. The bracket testing order and the five different degrees of tip for each bracket was randomized during the experiment.

[0116] The resistance to sliding was measured in Newtons (N) for each experimental condition and the results were analyzed using one-way analysis of variance (ANOVA) in the SPSS statistical program (SPSS, Chicago, Ill.). Post-hoc Students T-test was performed following positive ANOVA tests to identify significance between groups. The level of significance for all the tests was set at P<0.05.

Results

[0117] When the apparatus was tested with a mounted bracket but no archwire, the system consistently demonstrated a resistance to sliding of 0.733N (SD=0.029) and this calibration factor was deducted from all measurements in order to isolate the resistance to sliding of the archwire/bracket/ligature system.

[0118] When each of the bracket types was analyzed individually, the ANOVA confirmed that an increase in tip (bracket angulation) produces a significant change in the resistance to sliding (P<0.001) as shown in FIG. 9 where the data for the four bracket types are combined. Above two degrees of tip, the resistance to sliding increases much more dramatically than below two degrees.

[0119] At 0 of tip, the average amount of resistance to sliding was 0.57N (SD, 0.22N). One-way ANOVA analysis showed a significant difference between the different bracket types. For example, the bracket of the invention (Novel Bracket), at 0.53N had significantly less resistance to sliding than the 3M bracket which had 0.74N of resistance (see FIG. 10).

[0120] The Damon brackets consistently showed a higher standard deviation (1.23N vs. 0.53N) than the other brackets at each of the angles of tip measured.