Dentistry – Orthodontics – Bracket
Reexamination Certificate
2000-11-06
2002-11-26
O'Connor, Cary E. (Department: 3732)
Dentistry
Orthodontics
Bracket
C433S014000
Reexamination Certificate
active
06485299
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to orthodontic devices. More specifically, this invention relates to orthodontic brackets and particularly self-ligating orthodontic brackets.
BACKGROUND OF THE INVENTION
Several types of orthodontic brackets have been used in the prior art, including labial brackets and lingual brackets, which can each be either non-self ligating or self-ligating. As the name implies, labial brackets are positioned on the labial surfaces of a person's teeth. The most conventional type of labial bracket is a symmetric dual-wing bracket as shown in
FIGS. 1 and 2
. Referring to
FIGS. 1 and 2
, this bracket
1
has a bonding pad
4
, a base member
6
, and two opposing wings
12
. An archwire slot
10
is located between the two wings
12
and receives an archwire
8
at a right angle to the plane of the bonding pad
4
. After the archwire
8
is in place within the archwire slot
10
, an O-ring
14
is placed around one of the wings
12
and then stretched over the opposing wing
12
in a single-tie configuration to retain the archwire
8
in place. Because it requires an O-ring to retain the archwire
8
in its slot
10
, this bracket
1
is non-self ligating.
The single-tie O-ring configuration used with this bracket
1
allows the elastic tensile forces of both halves of the O-ring
14
to symmetrically oppose a force (represented by arrow
16
) tending to remove the archwire
8
from the archwire slot
10
. O-rings
14
must typically be replaced at least every six weeks because their elastomeric material degrades over time as a result of the chemical environment of the mouth. When it is time to replace the O-rings
14
, the O-rings
14
are removed and replaced one at a time by simply disengaging the end portions of the O-ring
14
from the wings
12
. The conventional labial bracket
1
is, therefore, fairly simple to use because the replacement of O-rings is straightforward.
Lingual brackets are attached to the lingual surfaces of a person's teeth. Lingual brackets are desirable because they are not readily noticeable to an outside viewer. Unlike the labial brackets described above, however, the conventional lingual brackets, as shown in
FIGS. 3
,
3
A,
4
, and
4
A, are generally difficult or inefficient to use. Referring to
FIGS. 3
,
3
A,
4
, and
4
A, a conventional lingual bracket
20
is asymmetric and comprises a bonding pad
24
, a base member
36
, and opposing occlusal (or incisal) and gingival wings
32
and
38
, respectively.
The conventional lingual bracket also includes an archwire slot
30
located between the two wings
32
and
38
. The archwire slot
30
of these brackets, however, is angled toward the gingival wing
38
. The archwire slot
30
has an entrance in the direction of the gingival wing, opposing first and second walls, and a base located opposite the entrance in the direction of the base member
36
. Examples are shown in U.S. Pat. Nos. 4,337,037 and 4,669,981 to Kurz. The gingival wing
38
can include an elongated extension with a knob end as shown in Kurz '981 or can be T-shaped to serve as a hook for inter-maxillary elastics. These lingual brackets are also non-self ligating because an O-ring
34
is used to secure an archwire
26
in the archwire slot
30
.
FIGS. 3 and 4
show the most typical tying arrangement of the conventional lingual bracket, i.e., double-tied. Referring to
FIGS. 3 and 4
, an O-ring
34
is generally double-tied around the archwire
26
of the conventional lingual bracket
20
. In a double-tie configuration, the O-ring
34
must first be placed around the base
36
of the bracket
20
. Only after the O-ring
34
is positioned around the base
36
is the archwire
26
inserted into the archwire slot
30
in a direction at an acute angle to the plane of the bonding pad
24
.
A second end portion of the O-ring
34
, located between the gingival wing
38
and the bonding pad
24
, is then stretched over the gingival wing
38
, around the archwire
26
and back over the occlusal wing
32
, forming a substantially U-shaped O-ring configuration, as viewed from a side view. The tensile forces of both halves of the O-ring
34
retain the archwire
26
within the archwire slot
30
by nearly symmetrically opposing a force (represented by arrow
22
) tending to disengage the archwire
26
therefrom.
Unfortunately, there are disadvantages with the double-tied lingual bracket of the prior art. First, as with labial brackets, the O-rings of lingual brackets must be replaced frequently. Unlike the single-tied labial brackets, however, the process for replacing the O-ring on a double-tied lingual bracket is complex. To replace the O-ring, the second end portion of the O-ring must first be stretched back over the occlusal and gingival wings such that the O-ring surrounds only the base member. Then, the archwire must be removed from the archwire slot. Only then can the old O-ring be completely removed from the bracket. Finally, a new O-ring must be attached using the steps described above for attaching the original O-ring. This process must be repeated for each of the lingual brackets needing O-ring replacement.
Another serious disadvantage with the use of double-tied conventional lingual brackets is that the O-ring must be stretched much further than that of the labial bracket. Excessive stretching further reduces the life of the O-ring. Furthermore, to accommodate this amount of stretching, the double-tied lingual bracket O-ring must be highly elastic. This increased elasticity adversely affects its tensile strength, and hence its ability to oppose forces that remove the archwire from its slot.
To avoid some of these disadvantages associated with double tying the O-ring of the conventional lingual brackets, a single-tie configuration for the same brackets has been attempted. Although it is possible to single tie the archwire into the archwire slot of the conventional lingual bracket, using a single-tie configuration with the conventional lingual bracket is disadvantageous because it results in a very weak retaining force.
FIGS. 3A and 4A
show a conventional lingual bracket using a single-tie configuration.
As shown in
FIGS. 3A and 4A
, in a conventional lingual bracket
20
with a single-tie configuration, the O-ring
34
is placed over the gingival wing
38
and then stretched over the occlusal wing
32
. In this configuration, a force (represented by arrow
22
) acting to disengage the archwire
26
from the archwire slot
30
is only weakly opposed by the O-ring
34
for several reasons. First, only the portion of the O-ring
34
extending from the occlusal wing
32
has a tensile force which directly opposes movement of the archwire
26
away from the slot
30
. The other portion of the O-ring
34
, attached around the gingival wing
38
at approximately a right angle to the first portion, is free to slide along the gingival wing
38
. It does not, therefore, provide any significant retaining force.
Further disadvantageous is the fact that the O-rings used to single tie the archwire into the archwire slot of the conventional lingual bracket must be replaced more frequently than those used in a double-tie configuration because they only have one portion of the O-ring that directly opposes the force tending to remove the archwire from the archwire slot. These drawbacks associated with conventional lingual brackets have made their use much less desirable than the labial brackets, despite the fact that many people prefer them aesthetically.
U.S. Pat. No. 4,531,911 (“Creekmore”) discloses other single-tie bracket configurations for both labial and lingual applications. Creekmore, and the other dual-wing prior art brackets described above, rely solely on tensile properties of the O-ring to retain the archwire within the archwire slot. They do not contemplate the use of other properties of the O-ring which might aid in retaining the archwire within its slot.
The industry has been unable to provide to the orthodontic profession a simple, lingual bracket which allows easy
Lingual Orthodontics, Ltd.
Marger & Johnson & McCollom, P.C.
O'Connor Cary E.
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