Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
ORTHODONTIC BRACKET AND ARCH ~IRE
The present invention is concerned with improvements
in or relating to orthodontic brackets that are employed in
procedures for applying corrective moving forces to teeth.
The invention is also concerned with improvements in or relating
to arch wires for use with such a bracket.
It is now almost universal practice in orthodontic
procedures that each tooth to be moved has a bracket fastened
thereto, the brackets being connected together by a thin springy
arch wire that applies the required forces thereto. The bracket
is usually fastened to a tooth band that is mounted around the
tooth but increasingly, with the development of suitable cement
systems, the brackets are cemented directly to the tooth surfaces
by means of a bonding pad.
There is disclosed and claimed in my U.S. Patent Serial
No: 3,772,787, issued 20th November 1973, an orthodontic bracket
comprising a bracket body having base, gingival, labial, occlusal,
distal and mesial surface portions and a mesial-distal extending
arch wire slot opening to the labial surface portion; a retainer
member mounted on a bracket ~ody, the retainer member having two
opposed portions thereof in embracing sliding engagement with
corresponding body surface portions with a portion thereof shaped
to extend over the labial surface portion to close the corres-
ponding side of the arch wire slot for retention of the wire
therein, the retainer member being movable with said embracing
sliding engagement on the body between two positions in which the
-- 1 --
, .
. ...
~16~3~35
slot labial side opening is respectively open and closed; and
means for positively retaining the member in at least the said
slot closed position.
It is an object of the present invention to provide
a new orthodontic bracket that is an improvement over that
disclosed in my earlier patent.
In accordance with the present invention there is provided
a new orthodontic bracket comprising a bracket body having lingual,
labial, gingival, occlusal, distal and mesial surface portions
lQ and a mesial-distal extending arch wire slot opening to the labial
surface portion, and a retainer member of resilient material
having opposed labial and lingual portions thereof in embracing
sliding engagement with corresponding labial and lingual body
; surface portions, the retainer member being movable on the body
between two positions in which the labial side of the slot is
respectively open and closed, the retainer member labial portion
being so shaped that in the slot-closed position it extends over
the body and has its free end protruding into the arch wire slot
so as to engage an arch wire therein and urge it towards the
lingual and occlusal walls of the slot, the movement of the
retainer member away from the slot-closed position toward the
slot-open position taking place against the resilience of the
retainer member owing to movement apart of the said opposed
portions thereof by the interposed engaged part of the bracket
body as the said free end of the protruding labial portion is
moved out of the arch wire slot.
The use o~ the brackets of the invention is found to
result in greatly expedited procedures, owing to the elimination
of the previously-used tie wires that must be individually tied
in the mouth and severed. Changes in arch wire are also greatly
expedited, since they require merely the retainer members to be
snapped to the open position, the wire changed, and then the
retainer members to be returned to the closed position, so that
there is a corresponding marked reduction in patient discomfort.
There is also a considerable reduction in the amount of manual
dexterity required of the orthodontist in the performance of
these procedures, the elimination of the need for chair-side
assistance, as well as the considerable saving of time resulting
in greater productivity. A cosmetic advantage is also obtained
in that it has been found the brackets can be made smaller than
hitherto which, together with the elimination of the somewhat
unsightly and potentially uncomfortable tie wires, results in an
improved appearance of the patient.
Particular preferred embodiments of the invention will
now be described, by way of example, with reference to the
accompanying diagrammatic drawings wherein:-
FIGURE 1 is a side elevation with part broken away ofmy prior bracket construction, as shown and claimed in my U.S.
Patent Serial No: 3,772,787,
~16~3~
Figure 2 i5 an exploded perspective view of a bracket
which is a first embodiment of the present invention,
Figure 3 is an exploded view of the bracket body of
the embodiment of Figure 2, together with an attachment pad
employed in securing the bracket to a tooth by cementing,
Figure 4 is a view similar to Figure 2 showing the
bracket assembled and with the retainer member in the slot-open
position,
Figure 5 is a view similar to Figure 4 showing the
retainer member in the slot-closed positisn and with an ar~h
wire fully retained in the slot,
Figure 6 is a view similar to Figure 5, showing the
effect on the retainer member of an arch wire that cannot be
fully retained in the slot as shown in Figure 5,
Figure 7 shows the use of the bracket with a
rectangular arch wire of the invention in the slot,
Figure 8 shows the manner in which the bracket of
the invention is employed with a tie wire when the arch wire
is entirely outside the slot,
Figure 9 is a vertical cross-section taken on the
line 9-9 of Figure 5, with a cementing attachment pad in
positio~,
Figure 10 is the same cross-section as in Fiqure 9.
but with the retainer member in the slot-open position,
Figure 11 is another vertical cross-section of a further
embodiment intended for use with a rectangular cross-section
arch wire of the invention showing in broken lines modification8
-- 4
... .
lJ~16~
made thereto to adapt i~ for moving a tooth to a predeterminte
inclined angle, and illustrating the manner in which it can be
used in combination with an arch wire of circular cross-section.
Figure 12A shows the combination of a bracket of Figure
11 with a new r~ctangular cross-section arch wire of the
invention employed for applying positive torque to a tooth
about the mesial-distal axis,
Figure 12B is similar to Figure 12A and shows the
combination employed when no mesial-distal torque is required,
and Figure 12C is similar to Figures 12A and 12B and showsthe
combination employed for applying negative torque to the tooth
about the mesial-distal axis.
Similar parts are given the same reference number in
all the figures of the drawings.
Each bracket comprises a body 20 which must be mounted on
the respective tooth, either by attaching it to a tooth-
embracing band 21, as shown with the prior art embodLment of
Figure 1, or by cementing it directly to the tooth. Thus, the
body is provided with oppositely-extending flanges 22 so as to
have a sufficiently large lingual surface 24 (Fig. 3) for
secure fastening of the bracket, for example by welding, to the
tooth embracing band, or to a cementing pad 26, illustrated in
Figures 3, 9 and 10. The cementing pad covers the bracket
lingual surface 24 and in turn provides a lingual surface 28
which is formed in some suitable manner, e.g. of foil mesh, or
by having recesses 30 formed therein, to facilitate adherence
of the cement.
For convenience in description the exterior ~urface
of the bracket body 20 is regarded as comprising a labial
surface portion 32, occlusal and gingival surface portions 34
and 36 respectively connected by the labial portion, and two
spaced mesial-distal surface portions 38, also connected by the
labial portion. A lingual surface portion 40 opposite to the
labial portion also joins the occlusal and gingival portions and
the two mesial-distal portions. It will be understood that the
,
body surface may be so smoothly contoured that adjoining surface
portions merge with one another with no specific demarcation
junction between them.
The body is provided with a mesial~distal-extending
slot 42 of rectangular cross-section opening in the labial
surface portion 32 and receiving an arch wire. In the prior
art drawing Figure 1 and in Figures 7 and 12 a rectangular cross-
section arch wire 44 is illustrated, while the wire 46 shown
in Figures 5, 6 and 8 to 11 is of circular cross-section. It
is of course part of the expertise of the orthodontist to
select a wire of appropriate cross-section and dimension from
the many different ones available, depending upon the forces
. that are required to be applied to the tooth to be moved~
Means for retaining the arch wire in the slot, while
permitting relative movements in the required directions
between the bracket and the arch wire, comprise a retainer
member 48 of thin flat resilient material, usually stainless
steel, shaped to embrace the body 20 and to conform closely
while in the slot-closed position with the labial,occlusal and
~ 68 ~ S
lingual portions thereof. For convenience in description the
retainer member will be regarded as comprising opposed labial
and lingual portions 50 and 52 respectively, each in embracing
sliding engagement with the respective bracket body portion,
and a connecting occlusal portion 54. As with the body, these
different portions of the retainer member merge smoothly into
one another with no specific line of demarcation between them.
The retainer member is movable by sliding and embracing movement
on the body between a slot-open position illustrated in Figures
4 and 10 and a slot-closed position illustrated in Figures 5 to
9 and 11. In the prior art Figure 1 the retainer member i8
shown in broken lines in slot-closed position and in ~olid
lines in slot-open position.
In the embodiments illustrated the retainer member
lingual portion 52 is relatively straight and terminates in a
free end 56, while the occlusal portion is approximately semi-
circular. The labial portion 50 immediately adjacent to the
occlusal portion is concave toward the body in conforming
closely thereto as described, while the remaining portion that
terminates in a free end 58 is relatively straight and pro-
trudes deeply into the slot 42. In the slot-closed position
the free end 58 abuts against a long gingival wall 60 of the
slot 42, this long gingival wall being provided by a labially-
extending portion 62 of the body projecting from the body below
the slot on the gingival side thereof. It will be seen that in
the slot-closed position the straight part of the retainer
member labial portion protrudes progressively deeper into the
-- 7
slot in the occlusal to gingival direction, and the extent of
this protrusion is made such that i~ will abut firmly again3t
an arch wire of circular cross-section of diameter for which
the slot is intended. As the result of this relatively deep
protrusion into the slot, any movement of the retainer member
away from the slot-closed position can only take place aga1nst
the resilience of the retainer member, particularly of the
labial and occlusal parts thereof, owing to the need for the
straight labial portion and the opposed lingual portion to
move apart from one another in sliding over the body part
which they embrace.
Therefore, the resilience of the springy material of
the retainer member provides a force at all times urging the
retainer member to move to the slot-closed position, where the
free edge 58 contacts the slot gingival wall 60. The lingual
portion 52 of the retainer member moves in a slot 64 in the
bracket lingual surface, and a recess 66 connecting with the
slot opens to the bracket lingual and gingival surfaces. The
free retainer member end 56 has a part 68 thereof struck out
of its general plane, so that the part cannot enter the slot 64,
but can move freely in the recess 66 during movement of the
member between its two extreme positions. The maximum move-
ment of the retainer member away from slot-closed position is
therefore determined by engagement of the part 68 and the
bracket body at the junction of the recess and the slot. It
will be seen that the retainer member can readily be moved out
of slot-closed position by the orthodontist inserting a simple
- 8
pusher tool into the recess to engage the part 68 and push it
upwards to the maximum extent. The tool can be for example a
plaque scaler, which is always available in a dental operatory.
In the full slot-open posi.tion illustrated by
Figures4 and 10 the labial retainer member free end 58 sits on
a mesial-distal extending so-called "parkingt' land 70. This
land is a discontinuity in the labial surface portion and i8 -
disposed at such an inclination to the remainder of the surface
that any force component caused by the retainer member
resilience and tending to urge the member to the slot-closed
position is not able to move the end off the parking land, 80
that the member is retained sufficiently securely in the slot-
open position. Usually the land will be located to correspond
with the maximum slot-open position set by the part 68, as
described above. It will usually be sufficient to make the
land 70 parallel to the bracket lingual surface for adequate
retention, but as illustrated, the land surface 70 preferably
is.inclined at between 10 and 20, more preferably at about
15,to the parallel position, while the resultant joining
surface 72 will be inclined to conform as closely as possible
to the shape of retainer member in this position; with the
preferred land surface inclinations described above the
inclination of surface 72 will usually be at about 15 to 25
to the paraliel position and opposite to that of the surface
70. The presence of the land 70 and surface 72 is also found
to reduce mechanical interference that otherwise can occur
between the retainer member and the junction of the body labial
'
g
39~
and occlusal surfaces as the retainer member moves between its
slot-open and -closed positions, the member being readily moved
off the parking land to the slot-closed position.
In use the brackets are fastened to the respective
teeth and one end of the arch wire is locked to the end-most
bracket by any suitable means (not illustrated). All the
retainer members are placed in the slot-open position, the
arch wire is inserted into the slots, if possible, and the
retainer members are then moved to the slot-closed positions.
The retainer members are of adequate strength and rigidity
to retain the wire in the slots but permit free movement of the
bracket along the wire and, with circular cross-sections, will
allow various rotations of the bracket relative to the wire.
Any force tending to urge the arch wire out of the slot force~
it against the inclined surface of the inwardly-protruding
part of the retainer member labial portion, resulting in a
force at all times positively urging the retainer member to
move to the slot-closed posLtion, at least considerably
reducing, if not completely eliminating, the possibility that
under the extremely arduous and unpredictable conditions to
which the apparatus is subjected, any of the retainer members
can spring open and allow the arch wire to escape. It has been
found with a particular embodiment that the force required to
open the slot is about 9-10 times the force required to clo~e it.
Referring now to Figures 5, 7, 9 and 10, it will be
seen that a circular cross-section wire of the size intended to
be used in the slot 42 is engaged by the end of the member
- la -
protruding into the slot, while the slot is sufficiently deep
to accommodate a rectangular cross-section wire, so that either
can be employed with the same bracket. Figure 6 illustrates
the fact that the springy retainer member is able to operate
with a wire that is skewed in the slot and partly protruding
therefrom, and will apply a desired rotation force to the
bracket and the tooth, obviating the need in many instances of
the use of a wide double bracket as illustrated in my prior
patent specification.
10The brackets of the invention are particularly suited
for use with rectangular arch wires, in that such a wire is
retained in the slot against rotation about its own longitudinal
axis, and the wire and springy retainer member are able ts
cooperate in applying torgue to the bracket body and thus to
the tooth, extending the nature and type of corrective force
that the orthodontist is able to apply with a single bracket.
: This extended application is facilitated by use of a wire 44
of cross-section as illustrated by Figure 7, which is pxovided
in its labial face closely adjacent to the junction of the
labial and gingival faces with a v-shaped groove constituted
by a "parking land" gingival groove face 76 (Figure 7) and a
connecting labial groove face 78, the latter face conforming
to the shape of the adjacent part of member 50, and into which
groove the retainer member free end 58 can protrude with its
extreme end face but~ing over its entire surface against the
land 76. The groove in the wire provides an improved positive
connection between the wire and the springy retainer member,
895
and thus between the wire and the bracket body, the incllnatlon
of the face 78 assisting in maintaining the retainer member in
the slot-closed position.
The considerable extension of the body part beyond
the slot to provide the gingival slot surface 60 ensures
that the retainer member end 58 is always shielded against the
possibility of snagging, or being snagged, even when the part
50 has been forced away from the body by an arch wire that is
skewed in the slot, as illustrated by Figure 6. Moreover, this
surface facilitates the insertion of a wire into the slot,
since the wire can be moved in the gingival direction to
engage the surface and then slid along the surface into the
slot. Figure 8 illustrated the procedure if the wire cannot
be inserted in the slot of one bracket. Each bracket is
provided with a mesial-distal extending passage 74 of
rectangular cross-section at the junction of the body lingual
and occlusal surface portions, through which passage a tie
wire 76 can be passed to secure the wire to the bracket. The
passage 74 could be of any suitable cross-section if it is
2Q required only to pass a thin tie wire, ~ut it is found
advantageous to make this passage also of rectangular cross-
section so that a rectangular cross-section wire placed therein
is constrained against rotation relative to the bracket. Such
wires can therefore be employed to provide additional corrective
forces.
- 12
~J 16~;15 9~
Pi~Jures 11, 12~-12C show an embodiment of the invention
intended for use with a generally rectangular cross-section
arch wire ~0 of the invention. In order to increase the torque
available by use of this wire its width is made such that, when
fully inserted in the slot 42, there is present some small
lateral displacement of the retainer member away from the bracket
body, so that the spring force of the retainer member is applied
between the wire and the body.
As illustrated, the preferred cross-section of the
wire is with a convex curved labial face 82 and with an occlusal
face 84 longer than the gingival face 86 and a lingual face
88 inclined lingually toward the occlusal fac~, the junction 90
of the occlusal and labial faces e~tending further in the labial
direction than the junction 92 of the gingival and labial
faces. The inclined lingual face cooperates with the occlusal
face so as to form a tapered wedge-shaped profile terminating
in a tip 94 at the junction of the faces. The lingual surface
of the slot 42 is inclined lingually to conform with the
inclination of the lingual face 88. A clearance is provided
between the wire and the slot in the gingival-occlusal direction,
so that the wire is capable of a small degree of rotation in
the s~ot. The clearance also permits the wire to be more
readily inserted into and withdrawn from the slot. Figure 12A
illustrates the manner in which the engagement of the springy
retainer member with the arch wire will apply a positi~e
rotating torque to the bracket 20 and thus to the tooth to which
it is attached, as illustrated by the arrows, while Figure 12C
- 13
~1~9~ ,
illustrates the manner in which this engagement can apply a
negative torque to the bracket and thus to the tooth~ The
effect in ~oth cases is for the wedge-shaped portion of the arch
wire to be moved into snug engagement with the corresponding-
shaped portion of the slot 42.
Figures 11, 12A-12C also illustrate how the bracket
can ~e modified to be used with the rectangular cross-section
arch wire to cause the required tooth movements. Thus the slot
42 can be inclined from the horizontal neutral position shown in
Figure 12B and in solid lines in Figure 11 to any of a number
of inclined positions, clockwise as shown in Figure 12A and
in chain broken lines in Figure 11, or anti-clockwise as shown
in Figure 12C and in broken lines in Figure 11. With the
clockwise-rotated slot of Figure 12A the arch wire will apply
a positive torque to the bracket until the tooth surface is
~ inclined at a predetermined angle to the vertical, while with the
,~ 'anti-clockwise rotated slot of Figures 12C the wire will apply
a negative torque to the bracket. The orthodontist can be
'~ provided with a selection of brackets ,in which the slots are at
different inclinations at predetermined intervals, extending
- over a range of positive angles through zero (neutral) and over
a range of negative angles, the orthodontist selecting the
bracket with the angle required to achieve the desired tooth
orientation.
It will be noted that as the slot is rotated clockwise
from the neutral position of Figure 12B its width is increased,
while its width is decreased upon anti-clockwise rotation to
the negative torque configuration of Figure 12C, this effect
- 14
being progressive with the change in torque angle. If the
lingual wall of the slot 42 were maintained uninclined as shown
in Figures 2-6 and 8-10, then at some rotation of the slot its
width would become such that a circular cross-section arch
wire 46 would be free to move laterally therein, so that it
would not be positively contacted by the retainer 20 to enable
use to be made of the springyness of the retainer member and its
relative sensitivity to lateral displacement. The wedge-shaped
configuration of the occlusal-labial junction permits this
undesirable effect to be avoided, and it is found possible with
all the required bracket configurations to provide for adequate -
engagement between the wire 46 and the retainer 50, the wire
being urged by the retainer into the wedge-shaped portion of
the slot 42.
