07/07/2018
Tooth angulation and dental arch perimeter-the effect of orthodontic bracket prescription
Angle developed the fixed orthodontic appliance that became known as the Edgewise appliance (1). In this system, tooth angulations of 3 degrees were established in the upper central and lateral incisors, while angulations of 5 degrees were established in the upper canines. In 1972, Andrews developed the Straight-wire appliance, in which pre-adjusted orthodontic brackets have in-built torque, tip and in-out prescriptions that are optimized for average cases (2, 3). In comparison to the original standard Edgewise technique, Andrews’ system results in an increased tooth angulation.
Several additional Straight-wire bracket prescriptions have since been developed. Roth modified Andrews’ original prescription into a more widespread form, the fully adjustable second-generation type (4). In his system, Roth increased the angulation of upper canines to 13 degrees.
There are argumentations that the changes introduced by the Roth system produced undesirable effects because increased angulation of canines promotes anchorage loss. Furthermore, we frequently observe a proximity between the roots of canines and first premolars on radiographs (5). Thus, MBT released the versatile unit, and the angle was decreased to 4 degrees in the upper central incisors and to 8 degrees in the upper lateral incisors and upper canines. Capelozza questioned the use of an upper canine angulation of 11 degrees, reporting that it was not unusual that bends or rebonds be required to compensate for excessive angulation (6). Thus, he suggested that the angle values for the upper incisors should be equal to Andrews’ original values and decreased the angle values of the upper canines to 8 degrees. The goal of these adjustments was to promote a more appropriate relationship between the roots of the canines and the first premolars.
Despite the great variation in the bracket characteristics of each prescription, few studies have examined the effects that such variations have on dental arch morphology, particularly on dental arch perimeter. Theoretically, an increase in the angulation of approximately rectangular teeth should increase the space requirements, leading perhaps to an increased need for extractions in borderline cases. Information on the effects of increased angulation on the root area is also lacking.
The aim of this study was to evaluate the effects of upper incisor and canine angulations introduced by standard Edgewise orthodontic brackets and by four Straight-wire bracket prescriptions (Andrews, Capelozza, Roth, and MBT) on dental arch perimeter.
Read more at:
-------------------------------
http://ejo.oxfordjournals.org/content/early/2014/10/13/ejo.cju055
-------------------------------
