Dentistry – Orthodontics – Bracket
Reexamination Certificate
2001-12-14
2004-05-11
O'Connor, Cary E. (Department: 3732)
Dentistry
Orthodontics
Bracket
C433S010000, C433S017000
Reexamination Certificate
active
06733285
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an appliance that is fixed to a patient's tooth during the course of orthodontic treatment. The appliance has a retaining groove to hold a wire segment or another item connected to the appliance in place.
2. Description of the Related Art
Orthodontic treatment involves movement of malpositioned teeth to desired locations along the dental arches. Orthodontic treatment provides improved occlusion so that the teeth function better together during chewing. Orthodontic treatment can also greatly enhance the aesthetic appearance of the patient's oral cavity by realigning crooked teeth and eliminating gaps or spaces between adjacent teeth.
One common form of orthodontic treatment is carried out by the use of tiny, slotted appliances known as brackets that are secured to the patient's anterior, cuspid and bicuspid teeth. An archwire is received in the slot of the appliances and forms a track to guide movement of the teeth to desired positions. Ends of the archwires are often received in passageways of small appliances known as buccal tubes that are secured to the patient's molar teeth.
Many orthodontic appliances have small, curved protrusions known as tiewings that extend outwardly from a central body of the appliance. For example, certain brackets have two spaced apart tiewings that extend in a gingival direction (i.e., a direction toward the patient's gingiva or gums). Those brackets also often have two spaced apart tiewings that extend in an occlusal direction (i.e., in a direction toward the outer tips of the patient's teeth). The gingival tiewings are connected to a central body of the bracket along a gingival side of the archwire slot and the occlusal tiewings are connected to the bracket body along an occlusal side of the archwire slot.
Tiewings are commonly used by the orthodontist during treatment to hold the archwire in the archwire slot. To this end, a ligature is placed along the back or lingual side of the occlusal tiewings and the gingival tiewings and is also placed over the front or labial side of the archwire. (As used herein, the word “lingual” refers to a direction toward the patient's tongue, while the word “labial” refers to a direction toward the patient's lips or cheeks.) In many instances, the ligature holds the archwire in contact with the bottom or lingual side of the archwire slot. However, in instances where the tooth is significantly maloccluded and initially located some distance from the archwire, the ligature serves to urge the archwire in a direction toward the bottom of the archwire slot.
In general, there are two types of ligatures in widespread use. One type of ligature is in the form of a tiny elastomeric O-ring. The O-ring is sufficiently flexible such that it can be stretched around and behind the tiewings as well as over the front side of the archwire. Once the O-ring is in place, the inherent memory of the elastomeric material tends to return the O-ring toward its normally compact, unstretched configuration. This contracting force urges the archwire toward the bottom of the archwire slot and also helps to retain the ligature in place.
Other types of ligatures are known as wire ties. These ligatures are made from short lengths of wire such as stainless steel wire having a small cross-sectional diameter. In use, the orthodontic practitioner extends the wire ligature around the backs of the tiewings as well as across the front side of the archwire, and then twists the free ends of the ligature together. Once the ends are twisted together and any slack in the ligature has been removed, the archwire is retained in the archwire slot or is urged toward the same.
The tiewings of the orthodontic appliances described above typically have a concavity in the form of a curved groove or notch that extends along the lingual side of the tiewing. For example, many tiewings have a semi-cylindrical lingual concavity that is oriented such that the central axis of the semi-cylindrical shape is approximately parallel to the longitudinal axis of the archwire slot. In some instances, the opposite side (or labial side) of the tiewing is generally flat and co-planar with a labial side of the appliance body. In other instances, the labial side of the tiewing has a curved configuration complemental to the curved concavity of the lingual side, such that the tiewing has an overall, somewhat hook-shaped or “C”-shaped configuration.
The lingual concavity of the tiewings as described above is generally considered important since it helps to retain the ligature in place during the course of treatment. Ligatures that become detached from appliances in use represent a significant nuisance since they may be inadvertently swallowed by the patient. In addition, appliances that are no longer connected to archwires due to missing ligatures are ineffective in moving the associated tooth, and as a result the length of treatment time may be extended.
As a consequence, manufacturers of orthodontic appliances have often designed and constructed tiewings to reduce the likelihood that the ligature will become detached from the appliance during the course of treatment. To this end, the lingual concavity of the tiewings typically is sufficiently large to extend around a substantial portion (such as one-half) of the periphery of the ligature when considered in cross-sectional reference planes. Ligatures that are deeply seated in the concavity during use are less likely to slip off of the tiewing and become disengaged from the appliance.
However, ligatures are available in a wide variety of cross-sectional sizes and shapes. Wire ligatures typically have a round cross-sectional shape with diameters ranging from about 0.008 in. (0.20 mm) to about 0.014 in. (0.36 mm). Ligatures made from an elastomeric material often have a cross-sectional diameter that is much larger, such as about 0.030 in. (0.76 mm) when relaxed and about 0.020 in. (0.5 mm) when in use. Furthermore, elastomeric ligatures are also known having cross-sectional shapes other than circular (see, e.g., U.S. Pat. No. 3,758,947).
As a result, the tiewings of orthodontic appliances are often provided with relatively large lingual concavities in order to accommodate any one of the wide variety of ligature sizes that might be selected by the orthodontic practitioner. This large lingual concavity tends to increase the overall size of the tiewing. Furthermore, tiewings are also designed with relatively thick cross-sections so that they are less likely to fracture and break off from the body of the appliance during use. Strong tiewings are deemed important because the tiewings are sometimes subjected to large forces, such as when a tiewing encounters a relatively hard food object in the oral cavity while the patient is eating.
Consequently, the tiewings of orthodontic appliances are often bulky in relation to remaining structural aspects of the appliance. The relatively large size of the tiewings is considered a disadvantage, however, because it increases the likelihood of contact with opposing dentition or with appliances mounted on opposing dentition. Tiewings may also contact adjacent soft tissue in the oral cavity and cause an irritation.
Manufacturers of orthodontic appliances have sometimes omitted tiewings when designing buccal tubes. The archwire passageways of buccal tubes are often closed along four sides, in contrast to the archwire passageways or slots of orthodontic brackets that are open along one side. When the ends of the archwires are inserted in the closed passageways, ligatures for connecting the archwire to the buccal tube appliance are not needed. The elimination of tiewings from such appliances helps to ensure that the appliance does not unduly bear against other structure in the oral cavity.
However, there are some instances where orthodontic practitioners prefer to use a buccal tube appliance having tiewings. For example, some buccal tubes for first molar teeth have a passageway that can be opened a
Puttler Oliver L.
Verdouw John A.
3M Innovative Properties Company
Christoff James D.
O'Connor Cary E.
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