WO2012056408A1

WO2012056408A1 - Self ligating orthodontic bracket

Info

Publication number: WO2012056408A1
Application number: PCT/IB2011/054776
Authority: WO
Inventors: Agatino Davide Mirabella; Luca Lombardo
Original assignee: Agatino Davide Mirabella; Luca Lombardo
Priority date: 2010-10-26
Filing date: 2011-10-26
Publication date: 2012-05-03
Also published as: EP2654599A1; ITRM20100567A1

Abstract

The present invention concerns a bracket (1) having a body (2 A) that defines a base (2); a slot (5) formed in said body and designed to accommodate an orthodontic archwire (4), a plurality of wings (3) formed in said body; a plurality of seats (12, 12') formed on one or more of said plurality of wings, each seat defining a bottom (13, 13') and at least one apical tip (14, 15, 16), a locking clip comprising a wire (8A). It is characterized in that it comprises at least one hole (6) formed on one or more of said plurality of wings (3), said locking clip pivoting in said at least one hole (6) relative to said body (2A) between a rest position, in which it disengaged from the bottoms (13, 13') or the apical tips of said plurality of seats to a work position in which it is engaged with a bottom of one of said plurality of seats.

Description

Title: Self Ligating Orthodontic bracket

DESCRIPTION

Field of the invention

The present invention relates to the field of dentistry and particularly orthodontics. The invention namely relates to an improved bracket, or anyway an alternative to prior art brackets.

Background Art

Various types of brackets are known in the art, which are designed to be affixed to a tooth on the vestibular or lingual side thereof. The affixing technique is also known and consists in stably affixing the bracket to the tooth and then introducing the orthodontic archwire into the horizontal groove of the bracket. This is followed by the so-called ligation of the bracket by special ligation wires, which are adapted to prevent the orthodontic arcwire from accidentally coming out of the groove (known as "slot").

Archwires are known to be available in various thicknesses and with different rectangular or circular sections.

The ligation step is rather complex because it has to be carried out on all the brackets of the teeth of the dental arcade under treatment. Means are currently available that allow automatic ligation, but this step is still inconvenient, especially when various patients have to be treated one after another.

For instance, US 6,071,119 discloses, with particular reference to its Figure 12, an orthodontic bracket having a base that is adapted to be fixed to the lingual or vestibular side of a tooth. A body extends from the bracket base, and houses a slot formed in the body and configured to accommodate an orthodontic archwire.

Tiewings are further formed in the bracket body, and have two seats configured to accommodate the wire of a locking clip by form-fit, which is configured to hold the orthodontic archwire, particularly when the locking clip is engaged with the bottom of a seat. For this purpose the orthodontist is expected to insert the clip to the bottom of the seat, and the free ends of the locking clip are laid into a channel (referenced 38e in US 6.071.119) defined in the body of the bracket.

When moving from the bottom of the first seat to the bottom of the second seat to switch the bracket between the active and passive states respectively with respect to the orthodontic archwire, the orthodontist is required to open the free ends of the clip apart from the bracket body to disengage them from the channel. Thereupon, the orthodontist may engage the locking clip with the bottom of the second seat and insert the free ends back into the channel, but in a position other than the previous one.

Since the locking clip is described as being made from a substantially rigid material, then upon displacement between the first and second seats, the free ends of the clip hook onto the channel in a position other than that they had before.

This is because the arms of the locking clip, which extend from the free ends to the portion engaged with the bottom of the seats, have a substantially constant length and hence, as the seat changes, the channel hooking position only changes on the tiewing.

Such configuration is affected by considerable drawbacks, including:

- difficult positioning of the locking clip each time an adjustment has to be made on the orthodontic archwire;

- any deposit in the channel preventing proper hooking of the free ends of the clip, and hence uneven application of holding forces on the orthodontic archwire and

- inconvenient operation, which requires movement of the whole clip relative to the bracket body, and hence involves the risk of causing undesired clip deformation.

Object of the invention

The present invention has, on the one hand, the object of meeting the requirement for a quicker bracket ligation, by providing a bracket having a simple adjustable system, for holding/retaining any type of orthodontic archwire in the horizontal slot thereof, as defined in claim 1.

The system also applies to any type of single or twin brackets, i.e. having either one tiewing or two tiewings.

The system has a simple construction and hence also meets the requirement of not increasing (or anyway moderating) the manufacturing costs of the novel bracket.

Most notably, the present concept is innovative in that it allows the clearance of the orthodontic arch wire to be modulated within the slot, with the holding forces being adjusted in a gradual manner, also according to the type of orthodontic archwire in use, as shown in the following description. This allows modulation of the degree of expression of the information contained in the bracket.

Brief description of the drawings

The present invention will be now described with reference to a particular embodiment thereof, which shall be taken as an example and without limitation of the inventive concept, and is shown in the accompanying figures, in which:

- Figures 1A and IB show a top view and a side view respectively of the bracket, with the locking clip in a disengaged position relative to the bracket body, according to the present invention;

- Figures 2A and 2B show a top view and a side view respectively of the bracket, with the locking clip in an engaged position relative to a first seat, according to the present invention;

- Figures 3A and 3B show a top view and a side view respectively of the bracket, with the locking clip in an engaged position relative to a second seat, according to the present invention.

Detailed description

The present invention will be described by way of example and without limitation by an embodiment thereof, which is shown in the drawings and is currently preferred. To avoid confusion, like or similar parts in the drawings will be always referenced by the same numerals, or by the same numerals with indices, throughout the figures. Also, the description only covers the details that are strictly required for understanding the invention and omits the details that are already known to the skilled person and whose mention would be useless herein.

Particularly, the bracket 1 comprises a body 2 A which defines:

- a base 2 adapted to be affixed on the lingual or vestibular side of a tooth;

- a first side (or front side) 2C projecting out of the base 2;

- a second side (or rear side) 2D opposite to the first side, and also projecting out of the base 2;

- a free side 2E opposite to the base 2, which delimits the bracket 1 at its top and

- two lateral side surfaces 2F, which delimit the periphery of the bracket 1.

For example, in the particular embodiment of the figures, the body 2A is embodied as a parallelepiped in which the first side, the second side, and the side surfaces 2F overhang transverse, preferably perpendicular, to the base 2 which is designed as a flat surface, whereas the free side 2E may extend parallel to the base 2.

A slot 5 is provided in such body 2E, and may be formed therein by known techniques, to extend into the body 2A from the free side 2E towards the base 2.

It shall be noted that the slot 5 is configured to accommodate an orthodontic archwire 4.

As shown in the accompanying figures, the bracket 1 comprises a plurality of wings 3, that may be formed in the first or second side of the body 2A and a plurality of seats 12, 12' formed on one or more of said plurality of wings 3.

Each seat defines a bottom 13, 13' and at least one tip 14, 15, 16.

In the preferred embodiment, two seats 12, 12' are provided, each defining a bottom and two apical tips. In the embodiment of the figures, the wings 3 are formed in the first side 2C and the seats 12, 12' are disposed in side-by-side relation to have a common apical tip (i.e. the one referenced 15 in the figures).

The seats 12, 12' extend into the body 2 A from the first side 2C along the lateral side surfaces 2F towards the second side 2D.

The bracket 1 further comprises a locking clip 8 which is designed to hold the orthodontic archwire 4 when the locking clip 8 is engaged with the bottom 13 or 13' of one of the plurality of seats 12, 12' respectively.

Particularly, the locking clip 8 comprises a wire 8A whose plan shape can be inscribed in a circle having a predetermined diameter D, preferably ranging from 1.5 mm to 5.5 mm.

Advantageously, at least one hole 6 is formed in the body of the bracket 1 , through one or more of said plurality of wings 3.

It shall be noted that the at least one hole 6 is formed on one of the two side surfaces of the bracket 1, on the side away from the one in which the seats 12, 12' are formed.

Preferably, two holes 6 are formed, one for each side surface 2F of the body of the bracket 1, each hole defining an axis of rotation 7 for the locking clip 8.

For example, the axes of rotation 7 may lie on a common plane parallel to the base 2 of the bracket body and hence be coincident or such axes of rotation 7 may lie on two different planes and hence be incident to each other.

The locking clip 8 advantageously pivots in said two holes 6 relative to the body 2A between a rest position (Figure IB), in which it is disengaged from the bottoms 13, 13' or the apical tips 14, 15, 16 of the plurality of seats 12, 12' to a work position (Figures 2B, 3B), in which the clip 8 is engaged with a bottom 13 or 13' of one of the plurality of seats 12 or 12' respectively.

Particularly, each hole 6 defines an axis of rotation 7 of the locking clip 8, i.e. the fulcrum or pivot point of the clip. When the locking clip 8 pivots about the axes of rotation 7 between the rest position (Figure IB) and the work position (Figures 2B, 3B), the elastic material that forms the wire 8 A of the clip causes the wire 8 A to move from the bottom 13 or 13' of the seat 12 or 12' respectively, to the apical tip 14, 15 or 16, thereby deforming along a first axis of deformation X-X for a value Δ equal to the diameter of the wire.

Such first axis of deformation X-X is transverse to the axis of rotation 7.

It shall be noted that the term first axis of deformation X-X of the wire 8A of the clip 8 is intended to designate the axis perpendicular to the direction of projection of the first side 2C and the second side 2D.

In other words, when the wire 8 A of the locking clip 8 moves, for instance, from the bottom 13 of the first seat 12 to the bottom 13' of the second seat 12', it must overcome the common apical tip 15 of the two seats. At the time of such passage, the deformation Δ of the wire 8A along the axis of deformation X-X is at a maximum. This deformation is caused by the elasticity of the material selected for the wire 8 A of the locking clip 8.

It shall be further noted that the wire 8 A of the locking clip has such elasticity that, when the wire 8 A moves from the rest position to the work position, the wire 8A deforms by a value Δ' ranging from once to three times the value of the diameter D of the wire, also along a second axis of deformation Y-Y.

Such axis of deformation Y-Y is substantially parallel to the axis of rotation 7.

It shall be noted that the term first axis of deformation Y-Y of the clip wire is intended to designate the axis perpendicular to the direction of projection of the lateral side surfaces 2F, i.e. the second axis of rotation Y-Y is orthogonal to the first axis of deformation X-X.

In other words, when the wire 8 A moves, for instance, from the configuration of Figure IB (i.e. with the clip disengaged from the seats of the bracket 1) to one of the configurations of Figures 2B and 3C (i.e. with the clip 8 engaged with the bottom 13 of the first seat 12, see Figure 2B, or with the bottom 13' of the second seat 12', see Figure 3B) and particularly passes through the common apical tip 15, then the wire 8 A deforms, along the axis Y-Y, by the value Δ', which reduces the aperture LI (see Figure 2B and Figure 3B) between the lateral side surfaces 2F of the body 2A of the bracket 1 and the outer surface of the wire 8A.

It shall be noted that a portion 11 of the locking clip 8 is actually engaged with the bottom 13, 13' of each seat 12, 12' and that portion 11 locked in the bottom 13, 13' of the seat 12, 12' by form-fit engagement provides the elastic load to be applied to the orthodontic archwire 4.

According to a preferred embodiment, the locking clip 8 has a substantially ring-like shape and may be either:

- an open ring with the free ends spaced by a distance that is much greater than the diameter D of the wire 8 A and pivoting in respective holes 6, or

- an open ring with the free ends close to each other and pivoting in respective holes 6. Particularly, if the ring of the clip 8 has spaced ends, then the two holes 6 are blind holes.

However, if the ring of the clip 8 has ends close to each other, then the two holes 6 are through holes, thereby forming a single hole that extends through the body 2A of the bracket 1 from one lateral side surface to the other.

As shown in the accompanying figures, the bracket 1 has the base 2, which is stably affixed to the tooth surface, and the upper surface having the so-called wings 3 that would be conventionally used to hold the ligatures.

It shall be further noted that the body 2A has an additional wing 17, opposite to the seats 12, which provides undercuts that can hold a traditional ligature if needed.

As shown in the figures, any orthodontic archwire 4, having either a circular or rectangular plan shape is inserted in a conventional slot 5 (here having a slot with a rectangular shape).

The bracket 1 may be of either single or twin type and have, for instance a width ranging from 1.5 mm to 3 mm.

The locking clip 8 has wholly or partially (i.e. in certain parts thereof) an elastically deformable structure, of anyway such a structure as to allow insertion of the portion 11 in a first seat 12 (like in Figure 2B) in which the orthodontic archwire 4 may be tighter than when the portion 11 is inserted in the second seat 12' (Figure 3B).

The accompanying figures clearly show that the choice of inserting the element 11 into one of the two locking seats 12, 12' may be made according to the size of the orthodontic archwire 4 and its section, its shape and especially its desired clearance.

Therefore, the present invention provides two different adjustments of the clip 8, thereby affording optimal adjustment of the tension to be imparted to the orthodontic archwire 4, also considering the section thereof in the slot 5.

Preferably, the diameter of the hole 6 formed in the body of the wing or (in case of a twin bracket) the wings 3 (of gengival or occlusal type) substantially ranges from 0.2 mm to 0.5 mm.

As mentioned above, the hole 6 allows insertion of the free ends of the wire 8 A of the clip 8.

For example, the clip 8 is made from a metal alloy and has a circular plan shape, with a diameter ranging from about 0.2 to 0.5 mm, or a square/rectangular plan shape that can be inscribed in a circle having a diameter ranging from about 0.2 to 0.5 mm.

In order to improve deformability of the clip 8 (having variable shape and size), its continuity may be broken (i.e. the element 11 might be broken so that the remaining portions of the wire 9A would be independently rotatable) or, for the same purpose, such discontinuity might be replaced by a curved or helical portion (whereby the element 11 would not be broken but have a variable shape along its first axis of deformation X-X).

The locking wing 3, i.e. the wing with the seats 12, 12', might also have a single locking seat for the clip 8. The configuration of the seats 12, 12', the element 11 and the deformability of the clip 8 (provided by the material and/or the shape of the clip), provide a press- and/or form-fit, which prevent disengagement (rotation) of the clip and hence release of the orthodontic arch wire 4 from the slot 5.

By way of example and without limitation, the areas of the seats may have the sectional shape of a circular arch, or ellipsoidal shapes with variable radiuses of curvature, or irregular broken polygons. Preferably, the element 11 that engages the seats 12, 12' has a substantially mating shape.

Preferably, the slot 5 of the bracket 1 has a height H ranging from 0.457 to 0.584 mm and a depth P ranging from 0.609 to 1.27 mm.

Figure IB shows dimensions that fall within these ranges (0.058 mm for the height and 1.016 mm for the depth of the slot, if it is formed with a rectangular section 5).

The depth P of the groove 5 is variable according to the degree of retention and clamping to be exerted by the locking clip 8 on the orthodontic archwire 4 and hence according to the orthodontic archwire in use.

The interaction of the clip 8 with the various retention areas (i.e. the seats) 12, 12' on the bracket 1 allows appropriate and gradual modulation of the clearance of the orthodontic archwire in the slot 5 and, as a result, modulation of the degree of expression of the information in the bracket 1.

Those skilled in the art will obviously appreciate that a number of changes and variants may be made to the bracket of the invention as described hereinbefore to meet incidental and specific needs, without departure from the scope of the invention, as defined in the following claims.

Claims

1. An orthodontic bracket (1), comprising:

- a body (2A) that defines a base (2) adapted to be affixed on the lingual or vestibular side of a tooth;

- a slot (5) formed in said body (2A) and configured to accommodate an orthodontic archwire (4),

- a plurality of wings (3) formed in said body;

- a plurality of seats (12; 12') formed on one or more of said plurality of wings (3), each seat (12; 12') defining a bottom (13, 13') and at least one apical tip (14, 15, 16);

- a locking clip (8) designed to hold said orthodontic archwire (4) when said locking clip is engaged with the bottom (13, 13') of one of said plurality of seats (12; 12'), said locking clip (8) comprising a wire (8A) whose plan shape can be inscribed in a circle of predetermined diameter (D);

characterized in that it comprises:

- at least one hole (6) formed on one or more of said plurality of wings (3),

- said locking clip (8) pivoting in said at least one hole (6) relative to said body (2A) between a rest position, in which it is disengaged from the bottoms (13, 13') or the apical tips (14, 15, 16) of said plurality of seats (12, 12') to a work position, in which it is engaged with a bottom (13, 13') of one of said plurality of seats (12, 12'), said at least one hole (6) defining an axis of rotation (7) of said locking clip (8);

- said locking clip (8) having such an elasticity that, when said wire (8A) moves from said bottom (13, 13') to said at least one apical tip (14, 15, 16), said wire (8A) deforms along a first axis of deformation (X-X) transverse to said axis of rotation (7) by a value (Δ) equal to said predetermined diameter (D).

2. An orthodontic bracket (1) as claimed in claim 1, wherein said locking clip (8) has such elasticity that, when said wire (8A) moves from said rest position to said work position, said wire (8 A) deforms by a value (Δ') ranging from once to three times said predetermined diameter (D), along a second axis of deformation (Y-Y) substantially perpendicular to said first axis of deformation (X-X).

3. An orthodontic bracket (1) as claimed in claim 1 or 2, comprising two holes (6), each defining an axis of rotation (7) of said locking clip (8), said axes of rotation (7) lying on a common plane.

4. An orthodontic bracket (1) as claimed in claim 1 or 2, comprising two holes (6), each defining an axis of rotation (7) of said locking clip (8), said axes of rotation (7) lying on two different planes incident to each other.

5. An orthodontic bracket (1) as claimed in any preceding claim, wherein a portion (11) of said locking clip (8) is engaged with said bottom (13, 13') of each respective seat (12, 12') and is locked therein by form- and/or press-fit engagement, i.e. with a given elastic preload.

6. An orthodontic bracket (1) as claimed in any preceding claim, wherein said locking clip (8) has a substantially open-ring shape, with free ends spaced from each other and pivoting in respective holes (6).

7. An orthodontic bracket (1) as claimed in claims 3 or 4 and 6, wherein said two holes are blind holes.

8. An orthodontic bracket (1) as claimed in claims from 1 to 5, wherein said locking clip (8) has a substantially open-ring shape, with free ends close to each other and pivoting in one hole (6).

9. An orthodontic bracket (1) as claimed in claims 3 or 4 and 8, wherein said two holes (6) are through holes.

10. An orthodontic bracket (1) as claimed in claim 1, wherein said locking clip (8) may be adjusted in its position, by insertion thereof in a first seat (12) or a second seat (12') to adjust the clearance of the orthodontic archwire (4) thereby applying different clamping/holding forces to the orthodontic archwire (4).

11. An orthodontic bracket (1) as claimed in claim 6 or 8, wherein said portion (11) of said locking clip is located opposite to said free ends.

12. An orthodontic bracket (1) as claimed in claim 6, 8 or 1 1 , wherein said portion (11) of said locking clip is discontinuous or broken and has two elastically deformable parts, each connected to respective first and second portions of said clip, which rotate independently of each other.

13. An orthodontic bracket (1) as claimed in claim 1, wherein the bracket (1) is of single type.

14. An orthodontic bracket (1) as claimed in claim 1, wherein the bracket (1) is of twin type.

15. An orthodontic bracket (1) as claimed in claim 1 , wherein the locking clip (8) is made from a metal alloy.