Palatal arch expander assembly and method of adjusting

A palatal arch expander assembly provides low, constant expansion forces to the palatal arch and provides individual corrective forces to either the first or second molars. A shape memory or superelastic archwire can be cooled below its transition temperature so that it is easily bendable for insertion into the mouth. After insertion, the archwire warms to a temperature above its transition temperature and provides low, continual expansion forces throughout the treatment period without requiring further adjustment. A pair of adjustment wires are bendable and provide individual corrective forces to either the first or second molars. The adjustment wires can be readjusted at any point during the treatment period. The archwire can be formed from a nickel-titanium alloy wire or superelastic material and the adjustment wires can be formed from nicoloy, stainless steel, or similar metal wire.

FIELD OF THE INVENTION 
The present invention relates generally to orthodontic appliances to move 
teeth. More specifically, a palatal arch expander assembly is provided to 
expand the palatal arch and provide corrective forces to the molars. 
BACKGROUND OF THE INVENTION 
The field of orthodontics is directed primarily to movement of teeth for 
various reasons, including correcting for malocclusions, expansion of the 
palatal arch, and moving the teeth en mass. Current orthodontic practice 
includes use of brackets that are bonded to the buccal surface of the 
teeth and an archwire attached to the brackets to reposition teeth. There 
are numerous prior art brackets and archwires available to accomplish the 
objective, some of which may include so called shape memory or 
superelastic alloy archwires or the more common stainless steel archwire. 
The shape memory archwires generally provide low but constant corrective 
forces throughout the treatment period without removing the wire to add 
different bending forces. The shape memory wires attempt to return to 
their original configuration and in so doing, provide the desired 
corrective forces. On the other hand, stainless steel archwires must be 
continually readjusted during the treatment period since they lose their 
tension once the teeth have been moved a prescribed amount. The stainless 
steel wires provide high corrective forces immediately after adjustment 
and these forces diminish as the teeth move toward the prescribed 
position. The stainless steel wires can cause discomfort to the patient 
immediately after adjustment because the corrective forces are highest at 
this point. 
It is sometimes necessary to provide corrective forces to the palatal arch, 
generally to expand the arch to add space and to align the molars and the 
premolars. Prior art devices include use of an archwire attached to the 
lingual surface of the molars and then providing expansion forces to move 
the teeth. The purpose in expanding the arch generally is to provide space 
for the molars or the premolars or to provide space between the teeth when 
crowding occurs. Some prior art devices include a stainless steel archwire 
used in conjunction with spreader bars or jackscrew devices which can be 
adjusted to provide expansion forces and create the necessary spacing 
between the teeth. These prior art devices typically require numerous 
visits to the orthodontist so that the device can be readjusted throughout 
the treatment period and after each visit the patient may experience 
discomfort due to the large corrective forces resulting from the 
adjustment. 
Other prior art devices include use of a shape memory archwire to expand 
the arch and provide the desired spacing between the teeth. The benefit of 
using a shape memory archwire is that it provides low, constant forces and 
it does not require as many visits to the orthodontist for readjustment. 
One problem that arises when using a shape memory archwire is that it is 
difficult to work with in terms of attaching it to the molars. It 
generally cannot be bent at severe angles (i.e., 180.degree.) and it 
cannot be heated above certain temperatures, otherwise it will lose its 
shape memory characteristics. 
Other disadvantages of the prior art palatal expansion archwires made from 
shape memory metals include the inability to readjust the forces 
distributed to the molars during the treatment period. Once a shape memory 
archwire is inserted, it will continuously provide constant corrective 
forces as the archwire attempts to return to its original shape. 
Unfortunately, the shape of the archwire may not always be the desired 
shape and there is almost always a need to correct the alignment of the 
first or second molars by tipping (angulation), rotating, or torquing 
them. In fact, it may be necessary to correct the alignment of one molar 
for rotation, and the opposed molar for tipping. The prior art stainless 
steel and shape memory archwires cannot achieve the most desired result of 
expanding the palatal arch with low, continuous forces and provide a means 
of aligning the molars as needed, independent of the forces on each molar 
and independent of the forces created by the archwire. The present 
invention satisfies these needs and provides a novel solution to the 
problems faced by the prior art devices. 
SUMMARY OF THE INVENTION 
The present invention solves the problems encountered by the prior art 
devices by allowing the orthodontist to expand the palatal arch using low, 
continual expansion forces and to align the molars independent of each 
other and independent of the archwire expanding the arch. The present 
invention provides an apparatus and method of treatment that is novel and 
accomplishes what the prior art devices cannot. It is noted that the 
reference to "molars" is intended to mean either the first molars or the 
second molars. Thus, for example, when it is said that sheaths are 
attached to the molars, it is intended that the sheaths are attached to 
either opposed first molars or opposed second molars, but not both sets of 
first and second molars. 
The present invention provides a palatal arch expander assembly which is 
inserted into the mouth of a patient and is easily removed when 
adjustments are required or when the treatment period is complete. The 
assembly includes an archwire having shape memory or superelastic 
properties to expand the palatal arch. It also includes a pair of 
adjustment wires attached to the molars so that each molar can be 
individually aligned without affecting the opposing molar. 
More particularly, the palatal arch expander assembly has an archwire made 
from an alloy of nickel-titanium (NiTi) which will expand the palatal arch 
with low, continuous forces. The assembly also includes a pair of 
adjustment wires attached to the distal ends of the archwire. The 
adjustment wires can be formed from nicoloy, stainless steel, or a similar 
material. Each of the adjustment wires has a bend formed in its distal end 
which can be adjusted to impart corrective forces to the individual 
molars. 
The archwire ends and the distal end of each of the adjustment wires are 
attached by inserting the ends into a crimp tube and crimping them until 
they are securely attached. At least a portion of the adjustment wires are 
inserted into a pair of stems having somewhat of a bayonet configuration. 
The stems are adapted to insert into sheaths which are mounted on the 
lingual surface of the molars. Each of the adjustment wires has a bend, 
which can be approximately 180.degree., and which is positioned between 
the crimp tube and the stem. With the bend so positioned, the adjustment 
wires can be easily adjusted by adjusting the amount of angulation in the 
bend and by twisting the bend outwardly toward the buccal. By adjusting 
the bend angulation corrective forces are imparted directly to the molars. 
The bend angles can impart rotational, angulation, and torquing forces in 
the molars. 
A novel method of insertion and adjustment is provided by the present 
invention. The palatal arch expander assembly is cooled prior to insertion 
into the patient's mouth, allowing the NiTi wire to twist and deform so 
that it can be easily positioned in the mouth. The stems are then aligned 
with and inserted into the sheaths so that the assembly is removeably 
attached to the molars. After insertion, the NiTi archwire warms from body 
heat and it transforms from its martensitic state to its austenitic state 
where it will attempt to return to its original shape. In its austenitic 
state, the NiTi archwire is somewhat stiff and inflexible and it provides 
low, continual forces to expand the palatal arch. Once inserted, the bends 
in the adjustment wires can be readjusted to rotate, torque or angulate 
the molars. 
The palatal arch expander assembly is easily removed by pulling the stems 
out of the sheaths and removing the assembly from the patient's mouth. If 
desired, the bends can be readjusted while the assembly is out of the 
patient's mouth and then reinserted to continue the treatment process. 
These and other features and advantages of the present invention will 
become apparent to persons of ordinary skill in the art upon reading the 
detailed description of the invention in connection with the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As used herein, references to "molars" is intend to mean either the first 
molars or the second molars. 
The present invention has fulfilled a need that was lacking in the prior 
art palatal arch expanders, two of which are depicted in FIGS. 1 and 2. 
The prior art device shown in FIG. 1 is an example of a palatal arch 
expander made generally of stainless steel. These types of expanders are 
difficult to insert into the patient's mouth because they are somewhat 
inflexible. A further disadvantage is that once installed and adjusted to 
spread or expand the arch, the forces at the beginning of the treatment 
are high and the teeth will move quickly, which can cause discomfort to 
the patient. These types of expanders also must be frequently readjusted 
requiring many visits to the orthodontist. 
The palatal arch expander depicted in FIG. 2, shows an archwire made from a 
shape memory alloy which will provide low, continual forces to expand the 
arch, thereby preventing the patient discomfort caused by the stainless 
steel arch expander. A major disadvantage of the FIG. 2 device is that 
once installed in the mouth, it cannot be further adjusted, which may be 
necessary since no two people have the same treatment prescription. More 
specifically, it is almost always necessary to adjust the position of the 
molars independently of the expansion of the palatal arch. The prior art 
devices lack this treatment capability. 
FIG. 3 depicts a typical palatal arch depicting opposed second molars 1, 2, 
opposed first molars 3, 4, and opposed premolars 5, 6. When crowding 
occurs between the teeth in the palatal arch, the molars and other teeth 
must be spread or expanded toward the buccal. 
The present invention, as depicted in FIGS. 4-7, provides a novel apparatus 
and method of treatment to expand the palatal arch and allow independent 
adjustment of the molars. As seen in the drawings, in a preferred 
embodiment, the palatal arch expander assembly 10 has an archwire 11 that 
is depicted as having a generally M-shape when viewed as in FIG. 4. 
Archwire 11 can have other configurations (not shown) and still provide 
the desired expansion forces. It also is preferred that archwire 11 have a 
concave shape, as shown in FIG. 6, so that it can approximate the 
curvature of the palatal arch. It is desirable to position archwire 11 
close to the roof of the mouth so that it does not interfere with the 
tongue, eating, and speech. 
Archwire 11 has a pair of ends 12, 13, which are used to attach the 
archwire to the rest of assembly 10. It is preferred that archwire 11 be 
formed from a shape memory alloy such as nickel-titanium (hereafter NiTi) 
which can be obtained from many sources, such as Raychem Corporation of 
Menlo Park, California. Products, such as archwires, made from NiTi have 
an austenitic state and a martensitic state and a transition temperature 
therebetween. Shape memory alloys are known in the art and are discussed 
in Shape-Memory Alloys, Scientific American, Vol. 281, pages 74-82 
(November 1979), which is incorporated herein by reference. 
Shape memory alloys, like NiTi, undergo a transition between an austenitic 
state and a martensitic state at certain temperatures. Thus, when in the 
martensitic state, an archwire made of NiTi will be deformable and easily 
manipulated. When heated to the transition temperature, however, the 
archwire attempts to return to its original configuration and it becomes 
highly flexible, but difficult to bend to different shapes. The 
temperature at which these transitions occur are affected by the nature of 
the alloy and the condition of the material. NiTi alloys generally have a 
transition temperature somewhat below body temperature, which is preferred 
for the present invention. 
The palatal arch expander assembly also includes adjustment wires 14, 15, 
each of which has a bend 16, 17 for adjusting the molars. Adjustment wires 
14, 15 have distal ends 18, 19 and proximal ends 20, 21, respectively. The 
proximal ends 20, 21 extend anteriorly for a distance, along the lingual 
surface of the premolars, while distal ends 18, 19 terminate at bends 16, 
17. The adjustment wires are attached to the archwire by crimp tubes 22, 
23. Distal ends 18, 19 of the adjustment wires and ends 12, 13 of the 
archwire are received in crimp tubes 22, 23 and the crimp tubes are then 
partially crushed so that the walls of the tubes firmly hold ends 12, 13 
and distal ends 18, 19. The adjustment wires 14, 15 preferably are made of 
a metal alloy sold under the tradename "Nicoloy" by Elgiloy Ltd., Elgin, 
Ill. The nicoloy alloy generally has about 39.72% cobalt, 19.92% chromium, 
15.24% nickel, 7.27% molybdenum, 2.03% manganese, 0.057% carbon, and the 
balance made from traces of beryllium, iron, sulfur, phosphorus and 
silicon. Those having skill in the art will appreciate that the particular 
nicoloy alloy disclosed here is preferred, however, it is only an example 
of the many alloy compositions available having similar properties. 
The nicoloy alloy permits the adjustment wires 14, 15 to be bent and 
adjusted either before or after assembly 10 is inserted in the patient's 
mouth. A nicoloy wire is preferred since it is adjustable and it retains 
its shape after it is bent so that it will provide corrective forces to 
the molars as will be described. Adjustment wires 14, 15 also can be made 
from stainless steel or metal alloys having similar properties. 
In keeping with the preferred embodiment, and as is most clearly seen by 
reference to FIG. 4, adjustment wires 14, 15 extend through stems 24, 25 
and are firmly attached thereto either by soldering, welding, brazing, or 
similar methods of attachment. As will be seen, stems 24, 25 are used to 
removeably attach palatal arch expander assembly 10 to the molars. Stems 
24, 25 can be made from stainless steel or similar materials. 
Turning to FIGS. 8 and 9, palatal arch expander assembly 10 is depicted as 
it is inserted into sheaths 26, 28, which are mounted on the lingual 
surfaces of opposed molars 31, 32. In keeping with the preferred method of 
inserting and adjusting assembly 10, prior to insertion the assembly 10 is 
cooled, and specifically NiTi archwire 11 is cooled with, for example, a 
refrigerant spray. Once cooled, archwire 11 becomes highly pliable and can 
be twisted to reduce its size for insertion into the patient's mouth. It 
also is important to be able manipulate the stems and guide them into 
sheaths 26, 28. Accordingly, when archwire 11 is sufficiently cooled below 
its transition temperature to its martensitic state, it can be easily 
manipulated so that stems 24, 25 can be aligned with and inserted into 
sheaths 26, 28. A locking detent 35 or similar locking device can be used 
to ensure that stems 24, 25 do not inadvertently back out of sheaths 26, 
28 during the treatment period. The orthodontist also can wire the stems 
into the sheaths or can use elastics, both of which should prevent stems 
24, 25 from inadvertently pulling out of sheaths 26, 28. 
After inserting palatal arch expander assembly 10 into the patient's mouth, 
body heat from the patient will warm archwire 11 so that its temperature 
will rise above the transition temperature of the NiTi to the austenitic 
state where it is relatively stiff. The NiTi archwire will then try to 
return to its original configuration which is to expand outwardly toward 
the buccal. The archwire will provide low, continuous expansion forces to 
molars 31, 32, and to the premolars 33, 34 which are in contact with a 
portion of adjustment wires 14, 15. In this manner, the palatal arch is 
slowly expanded and the patient should not experience discomfort because 
the expansion forces are small but continuous. 
In keeping with the preferred embodiment, as seen in FIGS. 10A through 12B, 
means are provided to impart corrective forces to molars 31, 32, 
independent of the forces imparted by archwire 11. The bends in the 
adjustment wires can be adjusted and readjusted to impart rotation, 
torque, and angulation in molars 31, 32. Referring to FIGS. 10A and 10B, 
rotation is imparted to molars 31, 32 by adjusting bends 16, 17 inwardly 
or outwardly, i.e., by increasing or decreasing the bend angle. Thus, by 
way of example, if the bend angle starts out at 180.degree., and it is 
desired to rotate the molars about their long axis 40, then bends 16, 17 
can be decreased to say 175.degree. which will impart rotation to the 
molars a specific amount. Conversely, the bend angle can be increased to 
impart similar but opposite rotation to the molars. Bend angles may range 
from about 30.degree. to 210.degree. of angulation. 
Similarly, and with reference to FIGS. 11A and 11B, the molars can be 
torqued independently of the forces imparted by archwire 11. Adding 
torquing forces requires adjusting bends 16, 17 along an arc 41 so an 
angle of, for example, 100.degree. from the vertical is created. Thus, the 
crown of the molar essentially is moving toward or away from the buccal a 
prescribed amount. 
Also in keeping with the preferred embodiment, and as shown in FIGS. 12A 
and 12B, angulation forces can be imparted to molars 31, 32 by adjusting 
bends 16, 17. Angulation forces are imparted to the molars by adjusting 
proximal ends 20, 21 of the adjusting wires up or down as depicted in FIG. 
12A. This in turn cause bends 16, 17 to adjust upwardly or downwardly and 
the same holds true for stems 24, 25. Since stems 24, 25 are attached to 
the sheaths on the molars, the molars will receive the angulation forces 
as depicted. 
In the preferred embodiment, archwire 11 and adjustment wires 14, 15 have a 
round cross-section. Other cross-sections, however, are contemplated, such 
as rectangular or square. 
As is known by those having ordinary skill in the art, each patient will 
require different prescriptions for rotating, torquing, and angulating the 
molars, thus the amount of correction is left to the orthodontist. It 
should also be understood that due to the nature of either nicoloy or 
stainless steel, it may be necessary for the patient to have readjustments 
made during the treatment period to obtain the optimum rotation, torque 
and angulation on the molars. 
From the foregoing it is apparent that there is described and provided an 
improved palatal arch expander and method for inserting and adjusting the 
assembly. While the particular embodiments that have been disclosed are 
illustrative of an assembly that achieves the advantages of the invention, 
the disclosed embodiments are illustrative and not intended to limit the 
invention as it is otherwise defined in the claims.