OBJECTIVE To examine the intra- and interexaminer reliability of assessing rotation of teeth on photographed study casts. In addition, the reliability parameters of two examiners scoring in mutual consultation were compared with the reliability parameters by one observer. MATERIALS AND METHODS Standardized photographs of sets of maxillary and mandibular plaster casts of 10 patients before tre...

A three-dimensional finite element model was created to analyze the influence of periodontal ligament (PDL) fibers on orthodontic tooth movement. Parametric studies were performed to ascertain the importance of fiber Young's modulus and orientation on the locations of the centers of rotation and resistance of a single-rooted tooth under a mesio-distal orthodontic load. If the Young's modulus is...

BACKGROUND This study used the 3D finite element method to investigate canine's displacements and stresses in the canine's periodontal ligament (PDL) during canine's translation, inclination, and rotation with transparent tooth correction treatment. METHODS Finite element models were developed to simulate dynamic orthodontic treatments of the translation, inclination, and rotation of the left...

OBJECTIVE To investigate the precise longitudinal change in the periodontal ligament (PDL) space width and three-dimensional tooth movement with continuous-force magnitudes in living rats. MATERIALS AND METHODS Using nickel-titanium closed-coil springs for 28 days, 10-, 25-, 50-, and 100-g mesial force was applied to the maxillary left first molars. Micro-CT was taken in the same rat at 0, 1,...

A palato-radicular groove (PRG) is a developmental anomaly primarily found in the maxillary lateral incisors. It is a potential communication path between the root canal and the periodontium that decreases the survival prognosis of the affected tooth, therefore compromising the stability of the dental structure in the oral cavity. The aim of this case report is to present an original technique ...

Granular ratchets are well-known devices that when driven vertically produce a counterintuitive horizontal transport of particles. Here we report the experimental observation of a complementary effect: the striking ability of circular ratchets to convert their vertical vibration into their own rotation. The average revolution speed shows a maximum value for an optimal tooth height. With no spec...

In the present study, the exact mathematical definitions of concepts of a “center of resistance” and a ”center of rotation of a tooth” are introduced. These concepts are widely used in the literature on orthodontic biomechanics, however they are nonstrictly defined. A center of resistance and a center of rotation are shown to exist only in particular cases. The conditions of their existence and...

BACKGROUND Many reports have indicated the treatment for permanent teeth with disturbed eruption due to the presence of supernumerary teeth. However, successful treatment for an unerupted maxillary incisor with severe rotation and another maxillary incisor with disturbed eruption by a supernumerary tooth is quite rare. CASE REPORT We treated a 7-year-old Japanese male with an unerupted and se...

The cephalometric records of sixty-four Class II, Division 1 cases treated exclusively with removable orthodontic appliances have been used in a study of the manner in which maxillary central incisors tilt. The center of rotation was most frequently located in the middle third of the incisor root. The longer the time interval between the pre- and posttreatment cephalograms, the more apical was ...