WO2010117927A1 - Appareil orthodontique usiné intégral comportant un crochet avec arbre à coupe transversale circulaire - Google Patents

Appareil orthodontique usiné intégral comportant un crochet avec arbre à coupe transversale circulaire Download PDF

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Publication number
WO2010117927A1
WO2010117927A1 PCT/US2010/029913 US2010029913W WO2010117927A1 WO 2010117927 A1 WO2010117927 A1 WO 2010117927A1 US 2010029913 W US2010029913 W US 2010029913W WO 2010117927 A1 WO2010117927 A1 WO 2010117927A1
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WO
WIPO (PCT)
Prior art keywords
hook
shank
bracket
bracket base
recited
Prior art date
Application number
PCT/US2010/029913
Other languages
English (en)
Inventor
Paul E. Lewis
Dwight P. Schnaitter
V. Timothy Wood
Michael J. Krumpelmann
Original Assignee
Ultradent Products, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ultradent Products, Inc. filed Critical Ultradent Products, Inc.
Publication of WO2010117927A1 publication Critical patent/WO2010117927A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
    • A61C7/12—Brackets; Arch wires; Combinations thereof; Accessories therefor
    • A61C7/28—Securing arch wire to bracket
    • A61C7/30—Securing arch wire to bracket by resilient means; Dispensers therefor
    • A61C7/303—Elastic bands

Definitions

  • the present invention relates to orthodontic brackets.
  • Orthodontics is a specialized field of dentistry that involves the application of mechanical forces to urge poorly positioned or crooked teeth into correct alignment and orientation. Orthodontic procedures can be used for cosmetic enhancement of teeth, as well as medically necessary movement of teeth to correct underbites or overbites. For example, orthodontic treatment can improve the patient's occlusion and/or enhanced spatial matching of corresponding teeth.
  • Orthodontic brackets are small slotted bodies configured for direct attachment to the patient's teeth or, alternatively, for attachment to bands which are, in turn, cemented or otherwise secured around the teeth.
  • a curved arch wire is inserted into the bracket slots.
  • the arch wire acts as a template or track to guide movement of the teeth into proper alignment.
  • End sections of the arch wire are typically captured within tiny appliances known as tube brackets or terminal brackets, which are affixed to the patient's bicuspids and/or molars.
  • the remaining brackets typically include open arch wire slots and apply orthodontic forces by means of ligatures attached to the brackets and arch wire (e.g. , by means of tie wings on the brackets).
  • Some brackets often include a straight hook extending from the bracket on which the practitioner can attach an elastic. Such hooks are bent intraorally by the practitioner in a labial-lingual direction, and sometimes a mesial-distal direction to provide the desired orientation. Such bending of the hook may often be performed 4- 5 cycles during a typical orthodontic treatment. Breakage of the hooks during bending is a problem, as it requires removal and replacement of the bracket.
  • the present invention is directed to machined metal orthodontic brackets including a hook having a circular cross-sectioned shank that is integrally machined with the bracket base.
  • a hook and bracket provides significantly increased strength, reducing the tendency of the hook to break during bending.
  • Existing brackets include hooks that are soldered or brazed onto the bracket base, which can easily be broken off, as well as metal injection molded brackets in which the bracket base and hook may be integrally injection molded from a metal powder and a binder. After molding, the "green" bracket is sintered, causing the metal powder particles to adhere to one another.
  • Such hooks also tend to easily break off, as the strength of the sintered metal powder particles is limited as a result of poor particle adhesion and the formation of micro-voids within the article.
  • the machined orthodontic brackets include a bracket base including an arch wire slot formed therein, and a hook disposed on the bracket base and extending away from the arch wire slot.
  • the hook includes an elongate shank at a proximal end of the hook that is integrally attached to the bracket base. At an opposite distal end, the hook includes an enlarged head.
  • the shank of the hook is machined so as to be substantially circular in cross-section. This advantageously allows bending of the shank (and thus the hook) in any direction, requiring a given level of bending force no matter the direction of the bend.
  • the hook exhibits significantly greater strength as compared to hooks attached by soldering or brazing, as well as hooks integrally formed with the bracket base by metal injection molding.
  • brackets make it easier for the practitioner to bend the hook in any desired direction, while also reducing or eliminating the possibility that the hook will break off during the intraoral bending that typically occurs several times during the course or orthodontic treatment.
  • Figure 1 is a perspective view of an exemplary orthodontic bracket with a hook in which the shank of the hook has a circular cross section;
  • Figure 2A is a cross-sectional view through the entire hook of the bracket of
  • Figure 2B is a cross-sectional view through the shank portion of the hook of the bracket of Figure 1 ;
  • Figure 3 is a perspective view the bracket of Figure 1 attached to a tooth
  • Figure 4A is a side view of the attached bracket of Figure 3 after having been bent buccally, away from the tooth and gingiva;
  • Figure 4B is a side view of the attached bracket of Figure 4A after having been bent lingually, towards the attachment tooth and gingiva.
  • the machined orthodontic brackets of the present invention include a bracket base having an arch wire slot formed therein and a hook disposed on the bracket base and extending away from the arch wire slot.
  • the hook includes an elongate shank at a proximal end of the hook that is integrally attached to the bracket base.
  • the hook includes an enlarged head.
  • the shank of the hook is machined so as to be substantially circular in cross-section. This advantageously allows bending of the shank (and thus the hook) in any direction, requiring a given level of bending force no matter the direction of the bend.
  • the hook exhibits significantly greater strength as compared to a hook attached by soldering or brazing, as well as a hook integrally formed with the bracket base by metal injection molding.
  • Bracket 100 includes a bonding surface 102 and a bracket body 104 including an arch wire slot 106 formed in the body 104.
  • Arch wire slot 106 is formed so as to extend mesially-distally through body 104.
  • slot 106 may alternatively comprise a hole of a tube bracket, for example, in which the labial side of the slot 106 is closed, forming a hole extending mesially- distally through the body 104.
  • the term "slot" encompasses both arch wire slots and arch wire holes.
  • Body 104 includes a plurality of tie wings 108.
  • the illustrated embodiment includes four tie wings, two of which are on occlusal side 105, and two of which are on gingival side 107 of bracket body 104.
  • One of the gingival tie wings 108' serves as a hook attachment tie wing, such that a proximal end 110 of straight gingival hook 112 is attached to hook attachment tie wing 108'.
  • Proximal end 1 10 extends gingivally away from gingival tie wing 108', transitioning to elongate cylindrical shank 114.
  • At the distal end 116 of hook 112 is an enlarged head 118.
  • the transitions from the attachment tie wing 108' to shank 1 14, as well as from the shank 114 to enlarged head 118, may be tapered as shown, resulting in a smoothed transition.
  • Illustrated hook 112 is straight, i.e., the shank 114 and head 118 are co-linear, without any bend formed therein during manufacture.
  • hook 112 is shown on gingival side 107, it may also be possible to provide an alternative embodiment in which the straight hook is disposed on one of the occlusal tie wings 108 on occlusal side 105.
  • hook 112 is integral with tie wing 108' and bracket base 104, as the entire bracket 100 is machined from a single bulk piece of metal (e.g., stainless steel).
  • hook 112 is not soldered or brazed to bracket body 104, which would result in an interface between the attachment point of the hook 112 and the bracket body, which attachment interface is prone to fracture when bending the hook during use.
  • shank 114 of hook 112 is machined so as to have a substantially circular cross- section. Providing a substantially circular cross-section results in a shank being capable of bending in any direction with substantially equal force required, no matter the direction of the bend.
  • the shank 114 of hook 112 can be bent buccally, lingually, mesially, and/or distally, and the force required to effect such a bend is the same, because the cross-sectional radial thickness of the shank as measured from a longitudinal axis of the shank from center point C out to the external surface of shank 114 is equal in every direction.
  • This equal force bending characteristic is advantageous over brackets having hook shanks with non-circular cross sections, in which the force required to effect a bend depends on the direction of the bend. Bending such brackets can be unwieldy, as a bend may tend to form in the direction of least resistance, rather than the direction desired by the practitioner.
  • An exemplary shank 114 may be machined so as to have a diameter of about 0.015 inch, while the overall length of the hook and its adjacent attachment tie wing 108' may be about 0.11 inch from arch wire slot 106 to the tip of enlarged head 118.
  • the length of shank 1 14 and head 118 may be about 0.055 inch.
  • the diameter of enlarged head 118 may measure about twice that of the shank 114. It is noted that the given values are only exemplary. For example, each value may more generally range within the given value plus or minus about 25%, more preferably plus or minus about 10%, and most preferably plus or minus about 3%. The given values are preferred as they have been found to provide sufficient strength to the hook, while also minimizing the overall dimensions and size of the brackets.
  • FIG 3 illustrates an exemplary bracket 100 attached to a canine 150.
  • the practitioner has bent hook 112 bucally away from canine 150 and gingiva 152.
  • the bend is formed near a proximal end of shank 114.
  • Such a bend may be formed to move head 118 temporarily away from gingival 152 (e.g., to allow better access to the gingival tissue 152 by the patient for improved hygiene).
  • the hook 112 may be bent lingually, as shown in Figure 4B, after which an elastic is hooked over head 118 of hook 112.
  • shank 114 is substantially a uniform circle, bending in any direction (i.e., buccally, lingually, mesially, distally, or any direction in between) is accomplished with application of the same force. In other words, no more or less force is required to form a buccal-ungual bend as a mesial-distal bend.
  • Hook 112 may undergo 4-5 bending cycles or more over the course of a typical orthodontic treatment. The increased strength of hook 1 12, its resistance to breakage, and its uniform bending force characteristics are distinct advantages to the practitioner and patient.
  • the arch wire slot or hole may be machined through the use of drill bits and/or end mills as described in United States Patent Application No. 61/159,859 filed March 13, 2009 and entitled METHODS OF MANUFACTURING ORTHODONTIC BRACKETS INCLUDING A RECTANGULAR ARCH WIRE HOLE, herein incorporated by reference.
  • the other bracket structures including the shank 114 and enlarged head 118 of hook 112, may also be machined using end mills and/or other suitable tools.
  • Such tools preferably include a carbide coating (e.g., titanium carbide and/or tungsten carbide).
  • Providing an integral machined hook with a circular cross-sectioned shank as described herein allows a practitioner to easily bend hook 112 in any desired direction.
  • hooks Because the hook structures arc machined, tight tolerances with respect to the hook dimensions are possible. Although it may be possible to form similar shaped hooks through metal injection molding, such hooks differ significantly in the dimensional tolerances of the hook structures, as well as the strength of the hook and its ability to bend repeatedly without breaking. For example, because of the formation of voids as well as the nature of metal injection molding, in which the powdered metal particles are fused together (albeit relatively weakly) during sintering, such a superficially similar hook would not have similar strength and would be significantly more likely to break during repeated bending.
  • any such superficially similar metal injection molded bracket must have larger dimensions (e.g., larger diameter hook shank, thicker bracket body, etc.) with respect to every bracket structure in order to work within the dimensional tolerances available in metal injection molding, as well as to provide sufficient strength to the bracket structures. Machining allows for further miniaturization of the bracket structures, including the hook as compared to a superficially similar metal injection molded bracket because of the greater strength provided by the bulk metal material as well as the tighter available dimensional tolerances. By way of further example, machining the brackets rather than metal injection molding allows for the use of stronger, more dense metal materials, which materials are not suitable in metal injection molding.
  • 17-4 and 17-7 class stainless steels may be heat treated after machining to further increase strength. Such heat treatments are not possible using classes of stainless steels suitable for use in metal injection molding.
  • metal injection molded brackets are formed from stainless steel powder materials (e.g., 303, 304, and/or 316L class stainless steels) which, although better suited for powderization and sintering, exhibit less strength and lower finished article density compared to 17-4 and 17-7 class stainless steels.
  • the strength and density of actual finished brackets formed by metal injection molding are less than the bulk strength and density of machined metal material, as micro air pockets routinely form during molding and sintering, and the strength of the finished article may be reduced as the sintering process may result in weak bonding of the metal powder.
  • Such reduced strength in the region of the shank of the hook could be problematic to the practitioner, if not catastrophic.
  • Such issues are minimized when machining the bracket and hook from a bulk metal material.
  • 17-4 and 17-7 stainless steels have a bulk density of about 7.75 g/cm 3 .
  • 316L stainless steel has a somewhat higher bulk density (about 7.95 g/cm 3 ), in practice the bulk density of the finished brackets formed from these materials will differ.
  • Brackets machined from 17-4 and/or 17-7 stainless steel can be expected to have a density substantially equal to the bulk density of the material, i.e., about 7.75 g/cm 3 .
  • brackets formed by a MIM technique will have a significantly lower density than the 7.95 g/cm 3 bulk density of the metal material, and likely even lower than the 7.75 g/cm 3 density of the machined brackets.
  • MIM manufactured brackets may exhibit a density that is at least about 5- 10% lower than that of the bulk material because of the presence of micro-voids within the article. The presence of such micro-voids and the resulting reduction in density significantly affects the strength of critical bracket structures (e.g., the hook).
  • the dimensional tolerances of the hook structure are significantly tighter with machined brackets as compared to brackets formed by metal injection molding.
  • the dimensions of the shank and head can be carefully controlled. Tighter dimensional tolerances with respect to the hook 112 result in the ability to form an overall smaller hook 112, takes up less space within the patient's mouth, and can be very helpful when attaching brackets to closely crowded teeth. Such control over dimensional tolerances is simply not possible with metal injection molding, where the sintering process results in an unpredictable amount of shrinkage.
  • the inventive integrally machined metal brackets including a hook having a shank with circular cross-section will exhibit significantly greater strength, increasing the cycles that such a hook can be bent back and forth without breaking as compared to a metal injection molded bracket and hook.
  • the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics.
  • the described embodiments are to be considered in all respects only as illustrative and not restrictive.
  • the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. What is claimed is:

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  • Health & Medical Sciences (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Dentistry (AREA)
  • Epidemiology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Dental Tools And Instruments Or Auxiliary Dental Instruments (AREA)

Abstract

L'invention porte sur des appareils orthodontiques usinés (100) comprenant une base d'appareil (104) comportant une fente en fil métallique en forme arc (106) ménagée dans celle-ci, et un crochet (112) disposé sur la base de l'appareil (104) et s'étendant loin de la fente en fil métallique en forme d'arc (106). Le crochet (112) comprend un arbre allongé cylindrique (114) à une extrémité proximale du crochet (112), fixé d'un seul tenant à la base d'appareil (104). A une extrémité libre distale opposée du crochet (112) se trouve une tête élargie (118). Du fait que l'arbre (114) est circulaire en coupe transversale, ceci permet de façon avantageuse la courbure de l'arbre (114) (et ainsi du crochet 112) dans n'importe quelle direction, ce qui nécessite un niveau donné de force de courbure quelle que soit la direction de la courbure. De plus, du fait que l'arbre (114), la tête (118) et la base de l'appareil (104) sont usinés à partir d'une seule pièce de matériau métallique brut, le crochet (112) présente une résistance significativement supérieure par comparaison à des crochets fixés par brasure ou soudure, ainsi qu'avec des crochets formés d'un seul tenant avec la base de l'appareil (104) par moulage par injection de métal.
PCT/US2010/029913 2009-04-10 2010-04-05 Appareil orthodontique usiné intégral comportant un crochet avec arbre à coupe transversale circulaire WO2010117927A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16848609P 2009-04-10 2009-04-10
US61/168,486 2009-04-10

Publications (1)

Publication Number Publication Date
WO2010117927A1 true WO2010117927A1 (fr) 2010-10-14

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180271621A1 (en) * 2017-03-22 2018-09-27 World Class Technology Corporation Adjustable hook for orthodontic brackets

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5306142A (en) * 1992-08-07 1994-04-26 Tp Orthodontics, Inc. Crimpable orthodontic hook
US5395237A (en) * 1994-01-06 1995-03-07 Minnesota Mining And Manufacturing Company Orthodontic bracket with integral ball hook and method of making
US20090004619A1 (en) * 2007-06-28 2009-01-01 Ormco Corporation Self-ligating orthodontic bracket and devices for deploying same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5306142A (en) * 1992-08-07 1994-04-26 Tp Orthodontics, Inc. Crimpable orthodontic hook
US5395237A (en) * 1994-01-06 1995-03-07 Minnesota Mining And Manufacturing Company Orthodontic bracket with integral ball hook and method of making
US20090004619A1 (en) * 2007-06-28 2009-01-01 Ormco Corporation Self-ligating orthodontic bracket and devices for deploying same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180271621A1 (en) * 2017-03-22 2018-09-27 World Class Technology Corporation Adjustable hook for orthodontic brackets
US11612457B2 (en) * 2017-03-22 2023-03-28 World Class Technology Corporation Adjustable hook for orthodontic brackets

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