Device for correcting teeth irregularities

A supplementary device for use in a device for correcting teeth irregularities includes a bracket having a slit with a T-shaped section and a wire to be inserted into the slit and engaged with the bracket. The wire has an elongated projection, and the supplementary device includes a wire engaging slit having substantially the same shape as the slit in the bracket. At least one protrusion is adapted for engaging a resilient band, and the bracket is slidable along the wire.

BACKGROUND OF THE INVENTION 
The present invention relates to a device for correcting teeth 
irregularities (malalignment), and more particularly, to a correcting 
device which can correct malalignment with no need of tying a wire to 
brackets. 
A conventional correcting device has, for example, as shown in FIG. 21, 
brackets 52, a wire 53 and strings 54 for tying the brackets to the wire. 
Each bracket is provided with a slit (wire-engaging-slit) 51 for catching 
the wire 53. The wire 53 is inserted through a series of the slits of the 
brackets 52, and is supported thereby. 
The wire 53 has a generally round shape in cross section, and sometimes a 
square shape. 
In use of the device, each bracket 52 is fixed on each tooth T of the 
malalignment. The wire 53 is inserted through the series of slits 51 of 
brackets 52, and then, the wire 53 is bent in such way that spring force 
of the wire 53 is applied upon the teeth to correct the alignment, and the 
wire is tied on the brackets by means of the strings 54 with utilizing 
grooves 55 in the side surfaces of the brackets 52. 
In the conventional device, it is very complicated to fasten the wire 53 to 
each bracket 52 and high skill is required, and moreover it takes much 
time to perform the fastening work. Especially, during the correction of 
malalignment, which may take a few months, the wire has to be changed to a 
new wire having higher elastic force several times, since the elastic 
force becomes weakened by gradual moving of the teeth. 
Consequently, both the orthodontist and the patient complicated and 
laborious procedure whenever the wire is changed. 
Further, in case a correcting torque is applied against the bracket by 
utilizing a square sectional wire in order to correct an inclination or 
twist of teeth, it is difficult to fasten the wire to the bracket, and 
highly refined technique is required for fixing the wire such that torque 
is sufficiently transmitted. 
In addition, since the conventional wire is made of a metal, the wire is 
bright and conspicuous, and the appearance is bad in use. Further, users 
may have an adverse feeling about the wire. 
In the conventional device, special brackets having cylindrical shape are 
used in order to fix both ends of the wire, and consequently, the patient 
feels disconfort in the mouth. 
A main object of the present invention is to delete the above-mentioned 
problems and to provide a device for correcting teeth irregularities, 
which is easily attached to the teeth facilitates changing a wire, and 
creates a less adverse feeling in use. 
Another object of the present invention is to provide a device for 
correcting teeth irregularities by using a plastic wire which has high 
resistance to creep and has large geometrical moment of inertia of its 
cross sectional area. 
In the conventional correcting method, it is difficult to fix the bracket 
to the tooth, wherein a twisted angle, inclined degree and the like are 
large and each shape is different, in the appropriate location and a 
angle. 
Many kind of the bracket having different shapes of the surface to be 
contacted with the tooth have been conventionally prepared or processed in 
accordance with the shape of the tooth. 
The object of the present invention is to provide a device for correcting 
teeth irregularities wherein the device corresponds to a tooth one-to-one 
and can be easily installed by providing the bracket with the base plate 
which can be easily processed so as to have a shape corresponding to each 
tooth. 
As the tooth to be corrected, there are such case where the tooth is 
twisted, inclined, oblique, or a clearance between teeth is large. When 
the clearance between teeth is large, a sliding operation is required. 
When the twisted tooth is corrected, it sometimes happens that the sliding 
operation is required in the correcting step. 
When one tooth is corrected by the sliding operation, the brackets which 
are fixed to the other teeth are corded up by a resilient material such as 
a rubber band to create the force of the sliding operation. 
However, since the bracket is small (width is in the range from 1 to 5 mm, 
length is in the range of 1 to 5 mm), the rubber band is difficult to 
engage and sometimes slips off. 
The present invention provides a supplementary device wherein an 
installation and removal can be easily performed. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a device for 
correcting teeth irregularites, comprising a bracket to be fixed on a 
tooth, said bracket having a slit with a T-shaped cross section, and a 
wire to be inserted into said slit and thereby be engaged with said 
bracket, said wire being provided with an elongated projection and having 
a "T" like shape in section.

DETAILED DESCRIPTION 
Referring to FIGS. 1 and 2, construction of a correcting device of the 
present invention is explained hereinafter. 
FIGS. 1 and 2 show a main part of a correcting device A which is an 
embodiment of the present invention. The numeral 2 shows brackets attached 
to teeth T, and the numeral 4 shows a wire inserted through slits 
(wire-engaging-slits) 3 of the brackets 2. In the embodiment of FIG. 1, 
the correcting device A comprises the brackets 2 and the wire 4. 
The bracket 2 has a flat base part 2a which is to be attached to the tooth 
T, and a pair of L-shaped nails 2b arranged on both the upper and the 
lower ends of the base part 2a respectively, so that they are facing each 
other. As a result, the pair of nail parts 2b build up a T-shaped slit 3 
therebetween. 
The bracket 2 can be made of dental alloy, ceramics, plastics or the like. 
As the plastics material, dental resin such as polymethyl methacrylate, 
polyoxymethylene, polycarbonate, and the like, which has high strength, 
less moisture absorption and anti-plastic-deformation even in a moist 
atmosphere at 80.degree. C. are preferably used. 
However, another synthetic resin such as polyolefin, polyvinyl chloride, 
polyester and the like can also be used. Further, various fibrous or 
powdery fillers of ceramics, metal, glass and the like can be blended in 
the above-mentioned polymeric materials. 
Metalic brackets are preferably to be coated with ceramics or plastics so 
as to become a neutral color (i.e. white, cream, or the like). 
The above-mentioned wire 4 can be made of the same material as the bracket. 
However, materials having high resistance to creepage (advancing 
deformation due to stress), low sliding frictional coefficient and high 
durability against various germs or dirt in mouth are more preferable. 
For example, a plastic tape molded together with (a) plastic filaments such 
as various kinds of polyester filaments, (b) the above-mentioned plastic 
filaments which are reinforced by blending inorganic crystal powder, 
organic powder, or inorganic or organic fine fibers, (c) glass fibers for 
core member, or the like can be preferably used. 
Through various experiments, it is demonstrated that creep resistance 
(anti-creep strength) of bending stress of a plastic extruded wire often 
lessens due to extension of the wire. 
Therefore, for instance, there is such a case that it is preferable that a 
plastic wire which is made by only extruding without extension, or which 
is obtained by extruding a plastic material, heating the extruded wire to 
the recrystallizing temperature thereof, and by cooling and curing. The 
mechanism of improving resistance to creep due to the heat treatment is 
not clear. However, it is considered that the directions of molecules of 
the plastics which has been oriented by extrusion become random when they 
are crystallized (unoriented crystallizing: a state that fine crystals are 
arranged in disorder) by the heat treatment. For example, as to polyester, 
preferable condition of thermal curing is approximately 30 sec to 2 
minutes at 160.degree. C. 
As shown in FIGS. 3 to 4, a shape of the wire 4, wherein wire has an 
elongated projection on one side of surface thereof and has a "T" like 
shape in section, is employed. A geometrical moment of the inertia of such 
the wire having the elongated projections and having "T" like shape in 
section 2 to 8 times as large as the wire which has a rectangular shape in 
section. With respect to the above wire, which has the projection, the 
tooth of the malalignment can be corrected in multiple directions 
(three-dimensionally). 
According to the present invention, the wire which has the projection has 
the shape in section as follows. A height of the protrusion ranges 
preferably from 0.1 to 1 when a widthwise length of the wire is 1. When 
the wire has the rectangular shape (width is 1.5 mm, thickness is 0.3 mm), 
the geometrical moment of the inertia of the wire is 0.0034 mm.sup.4. On 
the contrary, when the wire is provided with the elongated projection 
(height of the projection is 0.3 mm, width is 0.4 mm), the geometrical 
moment of the inertia of the wire is 0.0128 mm.sup.4. When the wire is 
provided with the elongated projection (height of the projection is 0.6 
mm, width is 0.4 mm), the geometrical moment of the inertia of the wire is 
0.0423 mm.sup.4. Further, with respect to the wire having an elongated 
groove as shown in FIG. 5, the wire is preferably provided with the 
groove, wherein width ranges from 0.1 to 0.5 mm and depth ranges from 
0.005 to 0.3 mm, substantially in the center of the other side of the 
surface of the wire. 
Further, as shown in FIG. 5, when a wire 4 having a groove 6 extending 
along a longitudinal direction of the wire is used, the wire can be easily 
and straightly folded as shown in FIGS. 19 by means of fingers F or the 
like. 
With respect to the wire shown in FIG. 6, the wire is provided with two 
elongated projections 5 on the one side of the surface of the wire and the 
elongated groove 6 on the other side of the surface of the wire. The wire 
may be provided with the groove between two projections. 
Hereinafter, the function and manner of use of the above-mentioned 
correcting device is described. 
Firstly, bracket 2 is adhered to each tooth T as shown in FIG. 20. In such 
case, in accordance with the judgement of a dentist, the postures of 
brackets 2 are adjusted and lined in such manner that the spring force of 
the wire becomes useful for correcting the alignment of teeth, and fixed 
there by means of resin adhesive. 
Next, the wire 4 is inserted through the series of slits 3 of the brackets 
2 in order as shown in FIG. 1. At the time, the wire 4 can be set by 
inserting the end portion thereof from a T-shaped side openings of the 
slit 3 which is adhered to the back tooth which is in the deepest such as 
a molar. However, since the clearance between adjacent brackets 2 is 
narrow, it is convenient to insert the wire, and then to push the wire 4 
in the slits 3 from the front openings thereof such that the wire is 
folded (FIG. 19) in the longitudinal direction by means of fingers F or a 
pair of tweezers. 
The wire 4 pushed in the brackets 2 returns to the original flat shape soon 
due to elasticity thereof. And both side edges are caught with the nails 
2b. 
The wire 4 might be previously bent a U-shape as shown in FIG. 20, and 
might be partially bent in smaller radius of curvature or is partially 
deformed, inclined, twisted or the like at regions corresponding to the 
teeth to be moved. 
Only by inserting the wire 4 through all brackets 2 as shown in FIG. 20, is 
attaching of the correcting device is finished. That is to say, it is not 
necessary to fasten the wire 4 to the brackets 2 with strings or the like, 
since the wire 4 is securely caught by the nails 2b. In addition, it is 
not necessary to fix the ends of the wire 4 with special brackets having a 
cylindrical shape which is necessary in conventional manner so that the 
wire 4 cannot slip along slits, in the brackets 2. 
If the occasion arises, the ends of wire 4 might be folded and set with 
heat. 
After installation of the wire 4, spring reaction force of the wire 4 is 
transmitted to the teeth Ta to be moved through the brackets 2. 
Consequently, the force (for example, about 20 to 200 g) shown in FIG. 20 
by an arrow N is applied to the teeth Ta for a long time. As a result, the 
teeth Ta are moved in the direction of the arrow N gradually. 
And besides, when a correcting torque in the twisting direction is 
required, a suitable correcting torque can be applied by merely changing 
the direction of the bracket 2, to be fixed on the tooth Ta, or by merely 
changing the shape of curvature of the wire 4. As the tooth Ta moves and 
then the wire 4 returns back to the original shape thereof, the spring 
force, i.e. correcting force, becomes weaker. In such condition, only the 
wire is changed for a new one with high stiffness, leaving the brackets 2 
as they are. The old wire can be easily removed by catching the end and 
drawing out of the slits. If required, the wire can be previously cut into 
some pieces. 
The new wire can be attached to the brackets 2 not only in such manner as 
shown in FIG. 19, but also by drawing out the old one after connecting 
with the old one. 
The wire is generally changed about once per several weeks as occasion 
demands. That is to say, during the whole treatment period, a half to two 
years, the wire is changed several times. 
In the above-mentioned embodiments, the brackets 2 are directly fixed on 
teeth as shown in FIG. 12. 
However, it is more preferable that the bracket 2 is adhered to each tooth 
T through a base plate 15. 
In this case, as a material of the base plate 15, it is advantageous for 
the device to employ material which is easily prepared. The base plate can 
be made from hard resin. The base plate is advantageously made from easily 
plastically deformable resin. The easily plastially deformable resin is a 
resin having a plasticity which is soft in beginning or which becomes 
plastic by applying heat. A thickness of the base plate ranges 
approximately from 0.5 to 5 mm in consideration of workability. 
Next, a function of the base plate, which is made from easily plastically 
deformable resin, or the present invention will be explained in accordance 
with FIG. 7. FIGS. 7(a) to 7(d) are schematic plan views illustrating 
working steps wherein molding is performed to the tooth Ta to be corrected 
by using the base plate 15 and the base plate 15 is fixed to the tooth. 
The base plate 15 mounted on the base part 2a of the bracket 2 is abutted 
to the tooth (FIGS. 7(a) to 7(b)) to which the bracket 2 is fixed so that 
the base plate 15 is firmly molded. Since the base plate 15 has easily 
plastic deformability, the base plate 15 can be easily deformed and 
closely contacted with the surface of the tooth. In order that the base 
plate 15 is easily deformed, heat may be applied, if desired. When the 
material of the base plate does not have an adhesion property relative to 
the tooth, the molding work can be directly on the tooth of a patient 
without any pain. When the material of the base plate has the adhesion 
property relative to the tooth, or the tooth to be corrected is located in 
the place where molding work is hard to be performed, teeth irregularities 
are molded by using a gypsum beforehand. 
The molded base plate 5 together with the bracket 2 are removed from the 
tooth (FIG. 7(C)), then cured. With respect to the resin having curing 
property, as means for curing, the means which has been conventionally 
used in the field of prosthodontia can be employed using heat, light, and 
the like. With respect to thermoplastic resin, the resin is cured by 
cooling. 
As shown in FIG. 7(d), the bracket 2 having the cured base plate 15 is 
fixed to the corresponding tooth Ta by means of an adhesive (not shown). 
In the conventional technique wherein the bracket is fixed to the tooth by 
means of the adhesion, it is very difficult to adjust a quantity of the 
adhesive and a gap between the tooth and the bracket. On the contrary, 
according to the present invention the bracket can be easily fixed to the 
tooth with a slight adjustment. The wire is inserted into the slit of each 
bracket 2 which is respectively fixed to the tooth so that the plate of 
correcting teeth irregularities is created (FIG. 7(d)). The base plate 
which is made from easily plastically deformable resin can be applied to 
not only the conventional bracket but also the bracket which uses the wire 
having a rectangular shape in section. 
The base plate is composed of the easily plastically deformable resin. As 
the easily plastically deformable resin, dental materials e.g. 
thermosetting resin such as epoxy resin, acrylic resin, phenolic resin, 
photocurable resin such as epoxy resin, acrylic ultraviolet crosslinking 
resin, thermosetting resin such as polyolefin resin, polyester resin, 
polyamide resin, polyimide resin, polycarbonate resin, which are 
conventionally known, can be employed. 
As the adhesives, the adhesives which is conventionally known may be 
selected in accordance with the materials of the base plate. According to 
the present invention, the base plate has a surface wherein its shape can 
be closely contacted with the tooth so that the quantity of the adhesive 
is not great, a processing or a modification after bonding is remarkably 
reduced. 
Next, a supplementary device for correcting teeth irregularities of the 
present invention will be concretely explained in accordance with FIG. 12. 
The supplementary device is useful for a sliding operation of the tooth 
when the supplementary device is used together with the above-mentioned 
correcting device (e.g. FIG. 14 or FIG. 15). 
As shown in FIG. 12, the supplementary device 25 is provided with a 
wire-engaging-slit 26 having substantially the same shape as the slit 3 in 
the bracket so that the wire 4 is engaged with the slit 26. The engaging 
state of the supplementary device is the same as that of the bracket and 
the supplementary device is allowed to slide only in the direction along 
with the wire thereon. The slit 26 of the supplementary device 25 involves 
a nail part 25b and a base part 25a so that the slit is formed into a "T" 
shape. As shown in FIG. 12, the nail part 25b is provided with a 
protrusion 27 having a projecting edge which is vertically extending. As 
shown in FIG. 12, the nail part 25b may be provided with two protrusions 
27 in both the upper and the lower marginal edges. The nail part 25b may 
have only one protrusion either in the upper or the lower marginal edge. 
In any case, a force applied to the tooth can be adjusted by selecting a 
location or combination of the protrusion 27 (e.g. FIG. 14). An elastic 
material such as rubber band 28 is engaged with the protrusion 27 so that 
a shrinkage force originates between two supplementary devices (referring 
to FIG. 14) each of which is stopped by the correcting device so as to be 
corded up. 
Since the supplementary device 25 is slidable on the wire, the bracket 
plays the part of a stopper (FIGS. 13 and 14). 
One feature of the present invention lies in that after the correcting 
device is once assembled and mounted on the tooth, the supplementary 
device is easily combined with the correcting device. That is to say, the 
wire 4 is pinched by a finger and a thumb so as to be bended (or folded) 
in the widthwise direction, and the wire 4 is engaged with the slit 23 of 
the supplementary device 25 so that the supplementary device 25 can be 
easily installed in the wire 4. Accordingly, when the twisted wire is 
returned to the normal posture and subjected to a sliding operation, 
installation and removal can be easily performed. In FIG. 14, a state of 
the supplementary device, which is installed by the rubber band 28 and 
combined with the bracket 2 and the wire 4, is illustrated. The rubber 
band 28 may be engaged with the protrusions 27 in parallel with the wire. 
The rubber band may be engaged with the protrusion diagonally. A schematic 
plan view of the supplementary device and the bracket, which are installed 
on the teeth, the illustrated in FIG. 15. 
The supplementary device of the present invention can have several kind of 
features other than the device shown in FIG. 12. 
For instance, as shown in FIG. 16, the supplementary device may have a 
shape, wherein the protrusion 27 is combined with a recessed portion 29, 
so that the rubber band is surely engaged with the protrusion. As shown in 
FIG. 17, the protrusion 27 may be formed on the nail part 25b near a 
location wherein the bracket is to be contacted. 
As shown in FIG. 18, the protrusion 27 may be shifted in the widthwise 
direction. The force applied to the tooth can be adjusted by changing the 
location of the protrusion. According to FIGS. 13 and 14, the 
supplementary device is installed in the wire so that the base part is 
opposed to the tooth (the base part is on the reverse side). 
The supplementary device can be installed in the wire so as to be turned 
over. The protrusion is normally formed in side face 30 (FIG. 18) of the 
supplementary device so as to be in the direction extending across the 
wire in consideration of a strength and an easiness of producing the 
supplementary device. Any protrusion, wherein the rubber band can be 
engaged, may be employed. The supplementary device has preferably a 
dimension as follows. A width is in the range from 2 to 6 mm, a length is 
in the range from 1 to 5 mm and a thickness is in the range from 1 to 2 
mm. 
As the wire applied to the supplementary device, the wire having 
rectangular shape in section as well as the wire having an elongated 
projection or a groove can be employed. 
The supplementary device can be used so as not to be fixed to the tooth. 
However, the wire is not excluded from being used so as to be fixed to the 
tooth. When the correction of the tooth is limited to the sliding 
operation, the bracket can be provided with the protrusion. The same 
effect is achieved from the correction of the tooth point of view. In the 
view point of a diversity of using and a treatment, the supplementary 
device is more advantageous. 
The supplementary device can be made from the same materials as the 
bracket. Since the supplementary device is used for a relatively short 
period and is seldom fixed to the tooth compared with the bracket, the 
strength is not necessarily high. The base part can be relatively thin, 
then the supplementary device can be installed in the wire by bending the 
base part and opening the slit. 
As mentioned above, the correcting device of the present invention has an 
advantage that setting of the device and changing of a wire is very easy 
due to the shape of bracket and cross section of the wire. 
Therefore, a synthetic resin with rather less in anti-creepage property can 
be used as a material of the wire, since such disadvantage can be 
compensated by adding frequency of change of wires. 
Therefore, since various synthetic resins having clear or white color can 
be freely used as a material of the wire, the present invention can 
satisfy a demand to use an incouspicuous wire. 
According to the present invention, the bracket is firmly fixed to the 
tooth and a workability of installing the bracket on the tooth is 
improved. 
Though several embodiments of the invention are described above, it is to 
be understood that the present invention is not limied to the 
above-mentioned embodiments, and various changes and modifications may be 
made in the invention without departing from the spirit and scope thereof.