In orthodontics, ceramics and plastics are becoming more commonly used in the formation of brackets With the increase in the use of ceramics and plastics, there is a corresponding increase in the frequency of breakage of such brackets Ceramic and plastic brackets tend to break more readily than a similarly designed metallic bracket due to a lack of ductility which is inherent in the materials used. When stress is placed on a metallic bracket, the ductile metal tends to deform or bend rather than crack or break. Contrarily, ceramics and some plastics will tend to crack or break rather than bend. When a bracket breaks due to stress from an orthodontic appliance, the broken portion results in a small jagged piece which is loose in the mouth of a patient.
In an effort to reduce the likelihood of the bracket breaking or cracking, the wire slots have been altered from a standard square or rectangular shape with orthogonally intersecting surfaces to a more rounded or smooth shaped slot. The use of such smooth shaped slots reduces the likelihood of cracks occurring at the orthogonal intersection of the surfaces Unfortunately, whenever a square or rectangularly shaped wire is used in a bracket slot that is rounded, there is an increased tendency for the wire to bind or cause excessive friction at the points of contact between the slot and the wire. Additionally, a square or rectangular shaped wire will not be correctly positioned in a rounded slot as the slot prevents full insertion of the wire which may result in some degree of misapplication of the desired adjusting forces Thus, there is a need for an orthodontic bracket slot which is shaped to take advantage of the stress reducing conditions of a rounded slot and yet allow round and square wires to be properly positioned in the slot.