A MAXILLARY PROTRACTION DEVICE WITH CHIN-CUP

A MAXILLARY PROTRACTION DEVICE WITH CHIN-UP

The present invention relates to a Modified Maxillary Protraction Device (MMPD) designed for the treatment of growing skeletal and dental open-bite cases accompanied by maxillary development deficiency.

Since a long time, the treatment of skeletal Class III malocclusions only by using orthodontical methods has been accepted to be difficult and subject to obstinancy. Before 1970's Class III problems were defined mainly as mandibular prognatisms and maxilla has not been very much emphasized, in the literature. Later studies have shown that a real isolated mandibular prognatism constitutes only 20-25 % of Class III cases.

According to Sinclair and Proffit (Sinclair, P.M.; Proffit, .R.: Class III Problems: Mandibular Excess/Maxillary Deficiency, in Surgical-Orthodontic

Treatment, (ed.) Proffit, W.R.; White, R.P. St. Louis: Mosby,1991,CH.14, ρ:428-

482.)among the class III anomalies, 20-25 % of the Class III population exhibited only maxillary deficiency, whereas 50-60 % exhibited maxillary deficiency, together with mandibular prognatism. This rate increases up to 32-43 % in the Japanese society wherein the incidence of Class III anomalies is quite high

(Takada, K.; Petdachai, S.; Sakuda, M.; Changes in Dentofacial Morphology in

Skeletal Class III Children Treated by a Modified Maxillary Protraction Headgear and a Chincup: A Longitudinal Cephalometric Appraisal, Eur. X Orthod. 15:211-

221, 1993.).

Excessive vertical development of the mandible, as well as its excessive forwards development, is quite common in Class HI abnormality groups and constitutes a combination that can be seen in 6 % of the patients.

The treatment plan for a skeletal Class III open-bite patient, during his/her growth period, should be aimed at both saggital and vertical anomalies, and excessive vertical growth of mandible must be prevented while the forwards- downwards growth of the maxilla is encouraged.

In the devices used in the state of art, the forwards development of the maxilla is provided and the forwards development of the mandible is inhibited. However, with the usage of maxillary protraction appliances, as the downwards growth of the mandible is not prevented, the length of the face increases. This situation may lead to the 'long-face syndrome' wherein chin-face (cranio facial) surgical operations may be required in skeletodental open-bite cases. For such a surgical intervention the patient has to wait until he/she is 18 years old or a multiphase orthodontic treatment that may last for many years with separate applications for the maxilla and mandible, has to be employed. During the multiphase orthodontical treatment, first a reverse head gear is implemented in order to increase the forwards maxillar development, however, the vertical open- bite status cannot be controlled by this implementation. Therefore the open-bite treatment is postponed to a later phase and requires the use of a separate apparatus.

Some orthodontists deem it convenient to wait until the completion of the growth of the Class III open-bite patients, without any interventions and upon the completion of their growth, to employ surgical methods to correct said anomalies. In the state of art, in EU Patent No. 445492, the mandible is connected to the magnets fastened by means of correcting levers to a control box. However here, only a vertical force is exerted on the chin.

In the Spanish Patent Application No.97/43975 a similar device is disclosed, whereby only a force in vertical direction is applied on the chin by using correcting elements. Furthermore, the correcting elements have no length adjustment and movement possibilities. In both applications, conformity to all types of patient faces cannot be provided.

The object of the present invention, is to prevent excessive vertical growth of the mandible and to provide an enhanced and rapid forward growth of maxilla, without causing facial elongation in the growing individuals with Class III open- bite anomalies.

Another object of the present invention is to provide a simultaneous exertion of a horizontal- forwards force and a vertical-upwards force.

One other object of the present invention is to be able to terminate the exertion of the horizontal - forward force by removing the hooks when a sufficient relationship in forwards-backwards direction, between the mandible and the maxilla is established.

Yet another object of the present invention is to be able to adjust the device in line with the facial structure of the individual.

Another object of the present invention is to realize the treatment in a short time, without subjecting a growing individual with many tiring procedures.

The maxillary protraction device realized in order to attain the objects of the present invention has been illustrated in the drawings, wherein :

Figure 1, is the exploded perspective view of the maxillary protraction device;

Figure 2, is the profile view of the maxillary protraction device; Figure 3, is the perspective view of the maxillary protraction device.

The components shown in the drawings have been separately enumerated as listed below : 1. Chin - cup

2. Front hook

3. Linear section of the front hook 4, Curved section of the front hook

5. Lateral hook

6. Front recess

7. Lateral recess

8. Fastening member 9. Fixing member (Screw)

10. Fixing member (Screw) hole

11. Head - piece

12. Maxillary protraction device

13. Anchorage unit.

The maxillary protraction device (12) comprises a chin-cup (1); one or more front hooks-levers (2) on the front section of said chin-cup (1) to exert a forqe horizontally and forwards to the chin; at least two lateral linear hooks (5) located at the sides of the chin-cup (1) to exert an upwards force to the chin orthogonally; a stationary or movable anchorage unit (13) placed on the upper palate; a headpiece (11) to be placed on the head; front recesses (6) and lateral recesses (7) to be used for engaging the hooks (2 and 5) to the chin-cup (1), in the same number as that of hooks; and fixing members (9) in the same number as that of hooks.

The head-piece (11) can be made in various shapes provided that it tightly fits onto the head. At the ear level, the head-piece is provided with a flexible fastening member (8) to be connected to the lateral hook in order to exert an upwards force to the mandible.

The chin-cup (1) has a structure in conformity of the patients' chin structure.

Said recesses (6 and 7) are adapted for the engagement of the hooks (2 and 5) and are provided with a fixing iriember hole (10) on them in order to fix the engaged hooks (2,5) in the recess (6,7).

The front hook consists of a linear - section (3) and a curved - section (4). Said linear section (3) is attached to the front recess (6) and is fixed by means of the fixing member (9).

The hook (5) with a lateral - linear form is attached to the lateral recess (7) and is fixed by means of the fixing member (9).

Said front and lateral hooks are preferably made of metal. The front recess

(6) and the lateral recess (7) form a protrusion on the chin-cup (1). The front recess (6) has a length at least equal to the linear section (3) of the front hook whereas the lateral recess (7) is at least as long as the lateral - linear hook. Said hooks enter the recesses from one end and exit from the other end.

The chin-cup is connected to a head-piece by means of lateral hooks (5) a rubber piece that will exert a force of 400-450 gf is provided between the headpiece and the lateral hooks. The free ends of the lateral hooks are attached to the lateral recesses (7) of the chin-cup, according to the facial dimensions of the patient and fixed by means of the fixing member (9). The removable or fixed anchorage unit (13) is placed to the upper palate. The upper hooks are attached to the front recess (6) after being adjusted according to the facial structure of the patient and fixed by means of the fixing member (9).

A fastening member (8) made of a flexible material such as rubber, is placed between the front hooks and the anchorage unit within the mouth, on both sides, i.e at left and right, in such a manner that they will each exert a force of 350 gf.

The treatment is continued until an adequate vertical and horizontal closure between the upper and lower incisors is obtained. When an adequate closing in horizontal direction is obtained, the front hooks (2) are removed but as the vertical growth and development take more time, the lateral hooks (5) are used for a longer time. The device can be adapted to a smaller size by removing the unused hooks (2,5) from the chin-cup (1).

In another embodiment of the present invention, lateral hooks are permanently fixed on the chin-cup.

With this invention, in the skeletal and dental open-bite cases accompanied by maxillary development deficiency in growing individuals, the maxillary forward development is obtained and the sagging of the mandible downwards due to excessive growth of the mandible in the vertical direction is inhibited. The device according to the present invention is easy to manufacture and has a low Cost of production.