Formative orthodontic appliance

An improved means of providing adjustable relative pressure between teeth in a fixed-type formative orthodontic appliance employed to increase dental arch size in a treatment plan to overcome crowding or malocclusion is defined. The mechanism is attached to a tooth band means and includes a special screw and arm assembly which is connected to an appropriate tooth pressure-applying clasp. Adjustment of the device may be accomplished by other than a skilled practitioner due to the tooth-band-mounting of the adjustment mechanism. Incorporation of the mechanism in an orthodontic appliance permits desirable reduction in the required bulk of the appliance.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention pertains to a mechanism usable in a formative orthodontic 
appliance. More specifically, it pertains to an adjustably-biasing, 
band-mounted mechanism joining pressure-applying members of such an 
appliance. 
Orthodontics is a specialized field of dentistry which often involves the 
use of special appliances to be worn in a patient's mouth and to provide 
corrective forces to teeth to modify their relative positions or their 
orientations within the mouth. These appliances, commonly known as braces, 
include a wide diversity of treatment approaches other than the familiar 
wire-and-bracket assemblies. Two such approaches, commonly used in Europe 
for more than 50 years and more recently in the United States, involve the 
use of removable appliances or functional appliances. 
Removable appliances typically include molded-acrylic sections contoured to 
fit against the hard palate in the case of upper jaw appliances, or to fit 
lingually on the lower dental arch in the case of lower jaw appliances. 
The acrylic sections form a base from which tooth pressure applying 
archwires, clasps, and the like extend to contact select teeth. Adjustment 
of the pressures from these acrylic sections is facilitated by 
manufacturing each section in two or more segments. Adjacent segments are 
joined with guide posts consisting of a pair of hollow cylinders in one 
segment and mated pistons in the other segment. An expansion screw 
assembly installed between the guide posts provides the necessary 
adjustment. An adjustment is usually made by first removing the acrylic 
section from the patient's mouth and then turning the expansion screw to 
change the appliance pressure as desired. 
Functional appliances are usually more complex than removable appliances 
and are employed to correct upper and lower jaw relative positions as well 
as to modify tooth positions. These appliances also may include 
molded-acrylic sections, screws, wires, and clasps similar to removable 
appliances. 
In typical orthodontic practice, treatment consists of installing an 
appliance in the patient's mouth and then making periodic adjustments to 
the appliance over a period of months, or even years, gradually to correct 
the condition under treatment. Appliances are categorized, inter alia, as 
being either fixed or removable. A fixed appliance is designed to be worn 
continuously by the patient and should be removed by the orthodontist 
only. A removable appliance is designed so that the patient may, himself 
or herself, remove all or part of the appliance to facilitate oral 
hygiene, to provide periodic respites from the treatment, or to make 
adjustments to the appliance. 
Other forms of orthodontic appliances are available that utilize metallic 
tooth bands to which bracket structures and archwires are attached. One 
embodiment of prior art, as disclosed in U.S. Pat. No. 4,468,196, issued 
to Keller on Aug. 28, 1984, provides a tooth-pressure-applying mechanism 
in the form of an archwire attached to a tooth band with adjustably-biased 
coil spring means. As with other prior art devices, the archwire assembly 
of this device must be removed in order to make an adjustment thereto. 
It is therefore a general object of the invention to provide access to the 
tooth pressure adjustment such that the adjustment may be made while the 
appliance is in place in the patient's mouth. 
Another object of the invention is to reduce the bulk of the appliance 
required for a given treatment plan so that the appliance is not 
physically distracting and does not impair normal speech or oral hygiene. 
A further object is to provide a fixed orthodontic appliance to be worn 
continuously, thereby reducing overall treatment time, and to eliminate, 
as a factor in treatment, patient cooperation in following a schedule 
having periodic installation intervals. 
These and other objects and advantages which are attained by the invention 
will become manifest as the description which now follows is read in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An adjustably-biasing band-means-mounted mechanism constructed in 
accordance with the present invention may be incorporated as part of a 
formative orthodontic appliance either designed to be installed on a 
patient's upper jaw or a patient's lower jaw. Although the upper jaw 
appliance is considerably different than the lower jaw appliance, the 
mechanism is substantially the same for either configuration; accordingly, 
a detailed description is provided for the mechanism as incorporated on a 
lower jaw appliance after the following general overview of both 
appliances. Operation of mechanisms on both appliances will then be 
described. 
Referring to the drawings, specifically to FIG. 1, a formative orthodontic 
appliance, as seen from below, is shown generally at 20 installed on an 
upper jaw dentition, shown generally at 21. Inasmuch as this appliance 
consists essentially of two mirror-like halves with corresponding 
construction and operation, the following description will reference 
components on only one side of the appliance. Appliance 20 includes a 
mechanism, indicated generally at 22, constructed in accordance with the 
present invention. 
Referring now also to FIGS. 2 and 3, a palate-nestled acrylic section, 
indicated generally at 23, is also included in appliance 20. This section 
comprises two segments 24, 26 adjoined to one another by an expansion 
adjustment assembly 28. The acrylic section is contoured to the wearer's 
hard palate and is held in place by an arm 30 which is fixedly adjoined to 
segment 24 at what is referred to as a first end 30a of the arm. Arm 30 
generally follows the transversal contour of the hard palate and forms a 
loop 30b at its end lingually near a first molar 32. Also adjoined to 
segment 24 is a dental archwire 34 which extends from the segment 
adjacently and parallel to arm 30 to the gum line. It then bends sharply 
and extends generally anteriorly toward the lingual surfaces of incisors 
36 where an incisor-contacting arcuate section is formed which follows 
generally parallel to an upper dental arch 37. 
Referring specifically to FIGS. 1 and 2, molar 32 is seen to be encircled 
by a band 38 which is formed to the outside surface of molar 32 and 
cemented thereto. Fixedly adjoined to band 38 is a clasp 40 which extends 
anteriorly and forms a loop around adjacent premolars 42 and 44. A 
generally cylindrical body 46 is attached lingually to band 38 and extends 
along a longitudinal axis 48 which is generally parallel to dental arch 
37. Body 46 contains a threaded bore along longitudinal axis 48 into which 
a mating screw portion 52d of an adjustment pin 52 is inserted. Pin 52 is 
also referred to as adjustable joining means. The anterior end of pin 52, 
as oriented in operative position, includes a spool-like section 
comprising spaced-apart coaxial collars 52a, 52b separated by an 
intermediate portion 52c. Posterior collar 52a includes two diametric 
holes perpendicular to one another and to longitudinal axis 48. These 
holes will be described further as part of the lower appliance discussed 
hereinafter. Intermediate portion 52c rotatably retains loop 30b of arm 30 
as shown in FIG. 3. 
The preferred embodiment of the instant invention as part of a lower jaw 
formative orthodontic appliance will now be described. As before, only 
one-half of the appliance will be discussed due to the characteristic 
mirror-image design of the appliance. 
A formative orthodontic appliance, as seen from above, installed on a lower 
jaw dentition 50 is shown generally at 51 in FIG. 4. Appliance 51 includes 
a mechanism, indicated generally at 53, constructed in accordance with the 
present invention. 
A band 54 is attached and cemented to a first molar 56. Fixedly attached to 
band 54 is a clasp 58 which extends anteriorly and lingually along the gum 
line past premolars 60, 62 and arches buccally at its anterior end 58a 
into the interproximal space of premolar 60 and a canine 64. An archwire 
66 extends transversally and generally parallel to a dental arch 68, 
lingually contacting incisors 70, 72, 74, 76. At incisor 70, the archwire 
bends posteriorly orthogonal to the dental arch and adjoins to an arm 67. 
The arm extends sagittally and forms a loop 67a at its posterior end, as 
shown. 
Referring now to FIGS. 4 and 5, mechanism 53, similar to mechanism 22, is 
seen to include a body 78 which is disposed along a longitudinal axis 79 
and contains a threaded bore. The body is fixedly attached to the lingual 
side of band 54. A screw portion 80d of an adjustment pin 80 is inserted 
into body 78. Affixed anteriorly to screw portion 80d is a spool-like 
section comprising collars 80a, 80b and an intermediate section 80c. Body 
78 and pin 80 on the lower jaw appliance are identical in construction to 
body 46 and pin 52 on the upper jaw appliance, as shown in FIGS. 1 and 2. 
Arm 30, shown in FIGS. 1, 2, and 3, on the upper appliance, serves an 
analogous function to arm 67, shown in FIGS. 4, 5, and 6, on the lower jaw 
appliance. Posterior collar 80a contains two diametric holes 82 
perpendicular to one another and to longitudinal axis 79 as shown in FIGS. 
5 and 7. As noted earlier, pin 80 is identical to pin 52 and therefore 
holes 82 detailed in FIG. 7 are featured on collar 52a, as generally shown 
in FIGS. 1 and 2. 
Operation of the Mechanism 
The operation of the mechanism will now be described. It will be recalled 
that on a lower jaw appliance 51, the mechanism comprises body 78, pin 80, 
including screw portion 80d and a spool-like section with collars 80a, 80b 
and intermediate portion 80c, arm 67, and loop 67a as shown in FIGS. 4 and 
5. For purposes of illustration, it will be assumed that the desired goal 
of appliance 51 is to increase dental arch size 68 at canine 64 to open a 
space between premolar 60 and incisor 70 in order to allow canine 64 to 
migrate lingually and posteriorly to a new position. The appliance shown 
accomplishes this result by anteriorly biasing the incisors with archwire 
66, and posteriorly biasing premolar 60 and molar 56 with band 54 and 
clasp 58, respectively. The structure of archwire 66 and arm 67 forms a 
spring which is compressed generally sagittally when positioned as shown. 
Energy stored in the spring thus provides sagittal forces; following 
principles of statics, anterior force must be neutralized by opposite, 
hence posterior, force of equal magnitude. Anterior force applied to the 
incisors by archwire 66 is neutralized by an equal posterior force against 
the mechanism by means of arm 67 and loop 67a acting against pin 80. (For 
clarity in the drawings, loop 67a is shown in the middle, or neutral, 
position of intermediate section 80c of pin 80. In fact, in operation, 
loop 67a abuts collar 80a as a result of the described forces.) 
The posterior force applied to pin 80 is transferred via body 78 to band 54 
and first molar 56. Clasp 58 retains premolar 60 and transfers posterior 
force from band 54 to that premolar. Premolar 62 must follow any posterior 
migration of premolar 60 due to interproximal contact between the 
premolars. Similarly, a second molar 83 must migrate posteriorly with 
first molar 56. Thus, it is seen that appliance 51 posteriorly biases 
teeth 56, 60, 62 and 83 and anteriorly biases teeth 70, 72, 74 and 76. 
Continuing to refer to FIGS. 4 and 5, mechanism 53 is seen to provide a 
means for varying the sagittal position of arm 67a; turning pin 80 such 
that it moves anteriorly increases the compression of the spring formed by 
archwire 66 and arm 67. From Hooke's Law, we know that force exerted by a 
spring varies in proportion to compression thereof within the elastic 
region of the spring. Therefore, the increased spring compression 
increases the sagittal forces to the teeth as described supra. 
Contrariwise, turning pin 80 such that it travels posteriorly, or into 
body 78, reduces the spring compression, yielding a corresponding decrease 
in the sagittal forces. Holes 82, as best seen in FIG. 7, provide a means 
for applying rotational force to adjust pin 80 via collar 80a with an 
external tool of the type that may be employed to adjust the expansion 
adjustment assembly of the acrylic section discussed previously. 
Adjustments to pin 80 may be made while the appliance is installed in the 
wearer's mouth due to the accessible location of collar 80a. 
Operation of the upper jaw appliance is analogous to the operation of the 
lower appliance described supra. As shown in FIGS. 1 and 2, clasp 40, 
analogous to clasp 58 on the lower appliance, forms a loop around 
premolars 42 and 44. The function of this loop is similar to the function 
of clasp 58, that is, to retain the premolars and to transfer thereto any 
sagittal force from the band. Archwire 34 is structured to form a spring 
analogous to the spring formed by archwire 66 and arm 67 on the lower jaw 
appliance. On the upper jaw appliance, posterior force from the spring, 
archwire 34, is applied to section 23. The arcuate anterior portion of 
archwire 34 provides anterior force to incisors 36. 
Arm 30 is also structured to form a spring which applies posterior force 
via loop 30b to pin 52 and corresponding anterior force to section 23. 
This anterior force neutralizes the force from archwire 34 to the section. 
The arm also provides palatal force to section 23 to hold the section in 
place against the wearer's hard palate. 
Adjustment of pin 52 changes the combined compression of the springs formed 
by archwire 34 and arm 30 and thereby provides the desired control over 
the pressures on the teeth involved in a treatment plan. As on the lower 
jaw appliance, adjustment to pin 52 may be made while the appliance is 
installed in the wearer's mouth due to the accessible location of collar 
52a. 
Changes and modifications to the preferred embodiment described herein will 
be apparent to those skilled in the art; these changes and modifications 
can be made without departing from the spirit and scope of the present 
invention. It is therefore intended that such changes and modifications be 
subsumed by the following claims.