[Show abstract][Hide abstract] ABSTRACT: Various ligation techniques and materials have been shown to affect the frictional resistance and the rate of tooth movement with sliding mechanics for space closure. The aim of this study was to evaluate the clinical efficiency of nonconventional elastomeric ligatures and conventional elastomeric ligatures during the canine retraction phase by comparing the rates of canine retraction.
The 20 patients (12 female, 8 male) in our sample had individual canine retraction (in the first premolar extraction space) in each quadrant (2 maxillary, 2 mandibular) with nonconventional elastomeric ligatures and conventional elastomeric ligatures on either side of the arch. The amount of canine retraction in each interval of 1 month was determined. The rate of canine retraction was calculated and subjected to statistical calculations.
The rates of canine retraction were higher with the nonconventional elastomeric ligatures. However, no statistically significant difference was observed in relation to the maxillary arch. Clinically, in most instances, canine retraction was completed in the same interval in both groups.
No significant difference in the rate of canine retraction was observed between the nonconventional elastomeric ligature and conventional elastomeric ligature groups in the maxillary arch. Clinically, the nonconventional elastomeric ligature group showed no reduction in time required for complete canine retraction in the maxillary and mandibular arches.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 06/2012; 141(6):715-22. DOI:10.1016/j.ajodo.2011.12.023
[Show abstract][Hide abstract] ABSTRACT: One of the many indications for dental arch expansion in treating malocclusion is to achieve arch compatibility, especially in surgical cases with severe Bolton discrepancies or collapsed arches due to congenitally missing anterior teeth. These cases usually require expansion in both the sagittal and transverse plane to achieve normal arch compatibility. Arch compatibility can be achieved by either dentoalveolar or skeletal expansion or both. Orthodontically, dentoalveolar expansion can be achieved by means of expanded arch form, vertical loops, or an added assembly such as a quad helix or Ni-Ti expander from the palatal or lingual aspect of the arch. However, these modalities normally provide expansion along transverse plane. If any expansion along sagittal plane is required, then additional appliances such as TransForce or modifications in the appliance system (eg, a quad helix with extension on anterior teeth) are necessary. Vertical loops do overcome these drawbacks to a certain extent; however, at the expense of generating moments during preactivation, which may lead to tipping of segments adjacent to the loop and precludes its use for larger changes of arch dimension. This article describes a new loop design-the KD loop-that increases the arch perimeter by sagittal and transverse expansion without generating significant moments along vertical plane.
[Show abstract][Hide abstract] ABSTRACT: To check the reliability of panoramic radiographs in assessing mesiodistal angulations while considering the true long axes of teeth in relation to a horizontal reference archwire.
A clear anatomical typodont with removable teeth was used with 0.8-mm chromium steel balls glued over the incisal/occlusal and apical/furcal portions of teeth to serve as reference markers for representing true long axes of teeth on radiographs and photographs. A photograph of each tooth was taken with a particular technique to serve as a medium through which to measure true mesiodistal angulations of teeth.
Only overall maxillary teeth angulations significantly correlated to true mesiodistal angulations. Radiographic relationship of the long axes of adjacent teeth (convergence or divergence) in the mandibular as well as the maxillary arch did not show any significant correlation to true degree of convergence or divergence and displayed a tendency to accentuate the maxillary canine to premolar divergence and mandibular lateral incisor to canine convergence.
Panoramic radiographs provide a poor representation of the mesiodistal angulations of teeth and require cautious use with clinical judgment and adjunctive procedures to ascertain root angulations.
[Show abstract][Hide abstract] ABSTRACT: The size of the envelope of tooth movements using fixed mechanotherapy has been increased with the use of temporary anchorage devices (TADs). Orthodontic mini-implants, a form of TADs, have been successfully used for achieving a variety of tooth movements, such as bodily retraction, extrusion, protraction, and even intrusion of maxillary molars. However, the use of orthodontic mini-implants for intruding mandibular molars is questionable due to anatomical constraints. Skeletal anchorage systems (SASs), another form of TADs, overcome these limitations to give promising results for mandibular molar intrusion. The following case report shows the use of unilateral SAS for intruding two mandibular molars and extruding a maxillary molar of the same side to establish a stable occlusal plane. The amount of intrusion achieved in relation to mandibular molars was evaluated by comparing panoramic images. The mandibular left first and second molars were intruded by approximately 1.6 and 2.5 mm, respectively, in relation to the occlusal plane.