Axes of resistance for tooth movement: does the center of resistance exist in 3-dimensional space?

Introduction: The center of resistance is considered the most important reference point for tooth movement. It is often stated that forces through this point will result in tooth translation. The purpose of this article is to report the results of numeric experiments testing the hypothesis that centers of resistance do not exist in space as 3-dimensional points, primarily because of the geometric asymmetry of the periodontal ligament.

Polyphenylene polymers as esthetic orthodontic archwires.

Introduction: There is continuing interest in an esthetic, effective labial archwire. In this study, we evaluated the potential of new, high-strength polyphenylene polymers to fill this need.

Methods: Polyphenylene (Primospire, Solvay Advanced Polymers, Alpharetta, Ga) polymer was extruded into wires with clinically relevant round and rectangular cross sections.

Viscoelastic properties of an aesthetic translucent orthodontic wire.

The objective of this study was to evaluate the time-dependent viscoelastic properties of an aesthetic orthodontic archwire. The wire is based on a recently developed translucent polyphenylene thermoplastic, whose rigid molecular structure provides high strength. While the wire has good instantaneous mechanical properties, over time all polymers may relax so it is important to understand the potential impact of the relaxation on orthodontic force systems.

Miniscrews in orthodontic treatment: review and analysis of published clinical trials.

Introduction: A systematic review of effects related to patient, screw, surgery, and loading on the stability of miniscrews was conducted.

Methods: Reports of clinical trials published before September 2007 with at least 30 miniscrews were reviewed. Parameters examined were patient sex and age, location and method of screw placement, screw length and diameter, time, and amount of loading.

Sagittal and vertical load-deflection and permanent deformation of transpalatal arches connected with palatal implants: an in-vitro study.

Introduction: The purposes of this laboratory investigation were to (1) measure the sagittal and vertical deflection of loaded transpalatal arches (TPAs) connected to a palatal implant, (2) measure the extent of permanent deformation of the connecting TPA in the sagittal and vertical directions, (3) test various wire dimensions in terms of deflection behavior, and (4) evaluate soldering vs laser welding vs adhesive bonding of TPAs in terms of load deflection behavior.

Methods: Stainless steel wires of 6 dimensions were tested: 0.8 x 0.

Initial changes of centres of rotation of the anterior segment in response to horizontal forces.

This study investigated the changes in the initial centres of rotation (Crot) of the upper six anterior teeth in response to a horizontal load. Six upper anterior teeth were extracted, splinted as a unit, and embedded in dental stone after the roots were uniformly coated with silicone. An aluminium fixture was bonded to the anterior segment and three linear variable differential transformers (LVDTs) were attached to measure the microdisplacement of the segment.

Influence of buccal segment size on prevention of side effects from incisor intrusion.

Introduction: Deep overbite can be corrected by maxillary incisor intrusion. The purpose of this study was to determine whether the size of the maxillary buccal segment influences the amount of steepening, extrusion, or narrowing of the buccal segments, or the rate of intrusion that occurs with maxillary incisor intrusion.

Methods: Twenty patients, 9 to 14 years of age, seeking treatment at a private practice, were divided into 2 groups.

Controlled space closure with a statically determinate retraction system.

We designed a variant of a cantilever spring, the statically determinate retraction system, and studied its mechanical characteristics. This novel system consisted of a single-force cantilever arm made of 0.017 x 0.