The orthodontic treatment of a patient concerns the movement of teeth through the application of forces to bring them into ideal arch and occlusion position. Forces are applied to the teeth by mounting brackets on the teeth and interconnecting the brackets with archwire which is activated to apply forces to effect teeth movement. While other auxiliaries are also used to effect teeth movement, primary forces are generated by one or more archwires which are made of a spring-like metal. Thus, connecting the archwire to teeth requires the mounting of brackets to the teeth which include archwire slots for receiving the archwire. Brackets are mounted on teeth by either attaching the brackets to bands that are in turn cemented to teeth or attaching the brackets to direct bonding bases which are then direct bonded by a suitable adhesive to the teeth.
There are two primary methods or techniques utilized to orthodontically treat patients. They are the light wire technique or system and the edgewise technique or system. The light wire technique basically uses light wire brackets and round archwire and depends upon the generation of light forces to effect teeth movement. The round archwire is usually secured to the brackets by lock pins that allow free tipping between the archwire and the teeth. Edgewise brackets and rectangular archwire provide the basic items used for the edgewise system. The rectangular wire is matingly received in rectangular archwire slots of the brackets to define a rigid connection. Suitable elastic or wire ligatures are applied over the archwire and their brackets for securing the archwire to the brackets. This technique is dependent upon much heavier forces to effect teeth movement.
Each of the techniques has its advantages and disadvantages. For example, in the light wire technique the interconnection between the archwire and the bracket can be made to permit the tooth freedom of rotation and tipping. The interaction between an edgewise archwire and an edgewise bracket is a more rigid system which allows for more precise control of tooth movement to the final position.
During the treatment of a patient, the advantages of both systems can be utilized to effect the most efficient overall treatment of any one patient. However, it is not practical to remove brackets for use in one system and thereafter apply brackets for use in another system because of the expense and time restraints.
Heretofore, various appliances have been designed for use in both methods of treatment. For example, combination brackets having the capability of receiving light wire or edgewise wire by virtue of having two different archwire slots for these wires have been well known, as shown in U.S. Pat. Nos. 3,163,933 and 3,178,822. These appliances have not been completely satisfactory because there is a need for more flexibility in usage than is possible with them. Moreover, they are bulky and cannot place the archwires at the same level, thereby requiring the mounting of the bracket at an offset position on the tooth, making it more difficult to apply forces.
It has also been known to provide an edgewise wire appliance where the appliance includes a two-piece unit with one piece being attached to a tooth and the other piece being detachably mounted on the first piece, wherein the detachable member includes an archwire receiving slot that may be designed to provide different degrees of angulation and torque in the receiving slot. Detachable members designed to accomplish various functions can then be interchangeably mounted on the fixed piece that is mounted on the tooth. Such an appliance is shown in U.S. Pat. No. 2,908,974. However, this appliance does not have the capability of being used for the light wire technique.
Another attempt to provide an appliance that is capable of mixing the techniques utilizes a standard edgewise bracket having a bandside occlusogingivally extending slot for receiving a light wire insert pin. The tail of the pin is bent over the bracket to secure it in place and the head of the pin includes a round archwire slot vertically displaced from the rectangular arch wire slot and which is open labiobuccally but may be closed following the disposition of an archwire in the slot. This appliance can therefore be converted for use in the edgewise system to use in the light wire system by utilization of the light wire insert pin. This appliance is not acceptable because the light wire slot is at a substantially different level from the rectangular wire slot.
It has also been known to provide an appliance that may be converted from a light wire appliance to a rectangular appliance, as shown in U.S. Pat. No. 4,212,638. This appliance in its initial form is a light wire bracket suitable for use in the light wire technique and to have a round wire secured to it by a suitable lock pin. Alternative to securing a round archwire to the light wire bracket, an edgewise insert is provided which may be locked to the light wire bracket to convert it into an edgewise appliance. This appliance is likewise objectionable in that the archwire for the light wire technique is at a substantially different level on the appliance than an edgewise wire used in the edgewise technique. Moreover, the addition of the edgewise attachment for converting the appliance to an edgewise appliance elongates the appliance, thereby making it bulky for the mouth. By virtue of the different levels for the archwire, it becomes necessary to place this appliance near the gingival and away from the incisal edge to avoid subjecting it to occlusion forces.