Biomechanical characterization of the periodontal ligament: Orthodontic tooth movement.

Objective: To quantify the biomechanical properties of the bovine periodontal ligament (PDL) in postmortem sections and to apply these properties to study orthodontic tooth intrusion using finite element analysis (FEA). We hypothesized that PDL's property inherited heterogeneous (anatomical dependency) and nonlinear stress-strain behavior that could aid FEA to delineate force vectors with various rectangular archwires.

Materials And Methods: A dynamic mechanical analyzer was used to quantify the stress-strain behavior of bovine PDL.

Three-dimensional evaluation of changes in lip position from before to after orthodontic appliance removal.

Introduction: Our objectives were to develop a reproducible method of superimposing 3-dimensional images for measuring soft-tissue changes over time and to use this method to document changes in lip position after the removal of orthodontic appliances.

Methods: Three-dimensional photographs of 50 subjects were made in repose and maximum intercuspation before and after orthodontic appliance removal with a stereo camera. For reliability assessment, 2 photographs were repeated for 15 patients.

Biomechanical reevaluation of orthodontic asymmetric headgear.

Objective: To investigate the distribution of distal and lateral forces produced by orthodontic asymmetric headgear (AHG) using mathematical models to assess periodontal ligament (PDL) influence and to attempt to resolve apparent inconsistencies in the literature.

Materials And Methods: Mechanical models for AHG were constructed to calculate AHG force magnitudes and direction using the theory of elasticity. The PDL was simulated by elastic springs attached to the inner-bow terminals of the AHG.

Treatment of pain after initial archwire placement: a noninferiority randomized clinical trial comparing over-the-counter analgesics and bite-wafer use.

Introduction: Pain is a major concern of patients before orthodontic treatment. Currently, the most frequently recommended treatments for pain after archwire placement or appliance adjustment are over-the-counter (OTC) analgesics. Although the overuse of OTC medications and their potential side effects are concerns, particularly for children, no study to date has investigated a nonpharmacologic option for pain management as an alternative for these analgesics.

The apparent contact dimension and covariates among orthodontically treated and nontreated subjects.

Unlabelled: The apparent contact dimension (ACD), a determinant of dental esthetics, has been purported to exhibit an esthetic relationship termed the "50:40:30" rule, implying that in an esthetic smile, the ACD between the central incisors, central and lateral incisors, and lateral incisor and canine would be 50, 40, and 30% of the height of a central incisor, respectively. This study assessed the existence of this proportion using casts of orthodontically treated (N = 40) and nontreated (N = 27) subjects deemed to possess excellent occlusion. Covariates studied included tooth size, tooth shape, tip, and torque.

Accuracy of measurements of mandibular anatomy in cone beam computed tomography images.

Objectives: Cone beam computed tomography (CBCT) images of ideally positioned and systematically mispositioned dry skulls were measured using two-dimensional and three-dimensional software measurement techniques. Image measurements were compared with caliper measurements of the skulls.

Study Design: Cone beam computed tomography volumes of 28 skulls in ideal, shifted, and rotated positions were assessed by measuring distances between anatomic points and reference wires by using panoramic reconstructions (two-dimensional) and direct measurements from axial slices (three-dimensional).

Accuracy of measurements of mandibular anatomy and prediction of asymmetry in panoramic radiographic images.

Objectives: Measurements of ideally positioned and systematically mis-positioned skulls were used to evaluate errors in linear measurements and symmetry ratios made with panoramic X-ray images.

Methods: Digital panoramic images of 30 skulls placed in ideal, shifted and rotated positions, were assessed by measuring distances between anatomic points and fiducial references. Differences between photographic measurements (control) and radiographic measurements were compared.