UNLABELLEDTo construct a three-dimensional finite element model comparing between one-step and two-step methods in torque control of anterior teeth during space closure.

METHODSDicom image data including maxilla and upper teeth were obtained though cone-beam CT. A three-dimensional model was set up and the maxilla, upper teeth and periodontium were separated using Mimics software. The models were instantiated using Pro/Engineer software, and Abaqus finite element analysis software was used to simulate the sliding mechanics by loading 1.47 Nforce on traction hooks with different heights (2, 4, 6, 8, 10, 12 and 14 mm, respectively) in order to compare the initial displacement between six maxillary anterior teeth (one-step method) and four maxillary anterior teeth (two-step method).

RESULTSWhen moving anterior teeth bodily, initial displacements of central incisors in two-step method and in one-step method were 29.26 × 10⁻⁶ mm and 15.75 × 10⁻⁶ mm, respectively. The initial displacements of lateral incisors in two-step method and in one-step method were 46.76 × 10(-6) mm and 23.18 × 10(-6) mm, respectively. Under the same amount of light force, the initial displacement of anterior teeth in two-step method was doubled compared with that in one-step method. The root and crown of the canine couldn't obtain the same amount of displacement in one-step method.

CONCLUSIONSTwo-step method could produce more initial displacement than one-step method. Therefore, two-step method was easier to achieve torque control of the anterior teeth during space closure.

Cone-Beam Computed Tomography ; Finite Element Analysis ; Humans ; Incisor ; Maxilla ; diagnostic imaging ; Periodontium ; diagnostic imaging ; Software ; Tooth Crown ; diagnostic imaging ; Tooth Movement Techniques ; methods ; Tooth Root ; diagnostic imaging ; Torque

OBJECTIVETo evaluate the accuracy of cone-bean CT (CBCT) on the measurement of the tooth length.

METHODSOne hundred and sixty single root premolars extracted for orthodontic purposes were selected. The tooth length was measured with vernier caliper. The premolars were divided into 10 groups randomly, 16 premolars in each group.In each group, the teeth were lined in molar area, premolar area, canine area and anterior tooth area in maxilla and mandible. Then CBCT was taken, and the tooth length was measured using the software supplied by the manufacturer in coronal and sagittal plane. Accuracy was compared between vernier caliper measurement and CBCT measurement.

RESULTSThe tooth length measured by CBCT was smaller than that measured with the vernier caliper. Significant differences were found in six areas, except the maxillary and mandibular premolar areas. With the increase of mesial-distal inclination or buccolingual torque angle, the difference between tooth length measured by CBCT and that measured with vernier caliper increased. The correlation between buccolingual torque angle (∠X1) and the coronal view of CBCT radiology tooth length (Spearmen index was 7.00, P < 0.001), and the correlation between mesial-distal inclination and the coronal view of CBCT radiology tooth length (Spearmen index was 0.624, P < 0.001) were found.

CONCLUSIONSThe tooth length measured by CBCT was smaller than that measured with vernier caliper.

Adult ; Bicuspid ; anatomy & histology ; diagnostic imaging ; Cone-Beam Computed Tomography ; Female ; Humans ; Image Processing, Computer-Assisted ; Mandible ; anatomy & histology ; diagnostic imaging ; Maxilla ; anatomy & histology ; diagnostic imaging ; Odontometry ; methods ; Radiography, Dental ; Random Allocation ; Tooth ; anatomy & histology ; diagnostic imaging

OBJECTIVETo evaluate the outcome of patients with skeletal Class III malocclusion treated with extraction of mandibular third molars and distalization of molars using implant anchorage combined with MBT appliance.

METHODSFifteen patients (mean age 24.0 ± 5.8) with skeletal Class III malocclusion were selected. The mandibular third molars were extracted and the mandibular molars were moved distally using implant combined with MBT appliance. Cephalometric analysis was carried out before and after treatment.

RESULTSAfter active treatment, ANB, Wits distance, AB-NP and the distance between upper and lower lip position to SnPg' increased by 1.65° ± 1.04°, (4.39 ± 1.93) mm, 3.20° ± 1.61° and (1.13 ± 0.99) mm, respectively. The differences were statistically significant (P < 0.05).

CONCLUSIONSThe skeletal Class III patients in the permanent dentition could be treated successfully with extraction of mandibular third molars and distalization of mandibular molars using implant anchorage combined with MBT appliance. The soft-tissue profile was improved.

Adult ; Cephalometry ; Dentition, Permanent ; Humans ; Incisor ; Malocclusion, Angle Class III ; therapy ; Molar ; Molar, Third ; surgery ; Tooth Extraction ; Tooth Movement Techniques ; methods ; Young Adult