Cephalometric Evaluation of Maxillary Incisors Torque and Vertical Changes Utilizing Standard Edgewise Mechanics

Abstract

In 1995 Gebeck & Merrifield studied a successful and unsuccessful treated Class I and Class IIÕs samples; they found a -1.33 mm intrusion in the former and a 0.80 mm extrusion in the latter. The purpose of this article was to perform a cephalometric evaluation of maxillary incisors torque and vertical changes. We studied a sample of 129 patients, 30 males and 99 females, taken from The Charles H. Tweed Foundation Long Term Study, at tretreatment mean age 12.93 years, posttreatment mean age 16.19 years and follow up post retention mean age 29.83 years, a 13.88 years interval. The records were collected from private practitioners across the North American continent who used Standard Edgewise Mechanics and were members of the Charles H. Tweed Foundation. All patients were Class I and II American whites treated with the extraction of 4 premolars. We found an Upper anterior incisal edge to PP vertical linear measurement 28.7 and 29.2 mm, +0.53 mm (p<0.019) from pretreatment to posttreatment. The average Upper 1 to SN angle was 103.2° at pretreatment and 100.1° at posttreatment, -3.2° (p<0.000), Upper 1 to PP 111.0° and 108.9°, -2.2° (p<0.000), the three of them statistically significant. Conversely, Upper 1 to commissure was not. The four measurements were also statistically significant posttreatment to follow up, upper anteriors kept losing torque after posttreatment, and less upper anteriors surface was below the commissure. Some torque loss and vertical extrusion can be expected while treating patients with extractions of four premolars, therefore, upper incisor inclination increase and vertical change by itself cannot determine the success of treatment