Humans ; Orthodontic Appliance Design ; Orthodontic Wires

OBJECTIVETo study the influence of two slot size brackets on torque control when teeth interacted in the same arch.

METHODSAfter the upper arch was aligned and leveled in Typodont study, the inclinations of upper teeth 5 +/- 5 were measured when 0.457 2 mm x 0.635 0 mm OPA-K brackets and 0.558 8 mmx0.711 2 mm OPA-K brackets were filled with 0.431 8 mm x 0.635 0 mm stainless steel wire. This experiment was duplicated 10 times. The inclin of each tooth were transformed to the absolute values of the torque play angle psi by computing program, and paired-t test was used.

RESULTSThe two kinds of slot size brackets were different with statistical significance on torque control. When the brackets were filled with 0.431 8 mm x 0.635 0 mm stainless steel wire, the absolute values of the angle psi in 0.558 8 mm x 0.711 2 mm and 0.457 2 mm x 0.635 0 mm slot size brackets were 6.140 degrees +/- 3.758 degrees and 2.608 degrees +/- 1.479 degrees respectively, and the average difference of that between the two slot size brackets was 3.532 degrees. The absolute values of the angle psi in the upper left and right canine brackets were 2.560 degrees +/- 2.605 degrees, 4.230 degrees +/- 2.817 degrees, 1.260 degrees +/- 0.747 degrees and 2.070 degrees +/- 0.663 degrees respectively, and average differences between them were smaller than that in the other teeth.

CONCLUSIONThere was difference between the two kinds of slot size brackets on torque control, and 0.457 2 mm x 0.635 0 mm slot size bracket controls torque better when filled with the same size wire. In this study, the teeth interaction in the same arch probably caused the result that the difference of two slot size brackets on torque control was less than the study results of the theory calculations and material studys before.

OBJECTIVETo investigate the effect of loop configuration on appliance stiffness of stainless steel round wire.

METHODSSome stainless steel round wires with various cross-sectional dimension (0.36, 0.41, 0.46 mm) were selected. Box loops, double horizontal loops, and double vertical loops were manufactured according to established parameters, and loading experiments were carried out with a micro-orthodontic archwire testing apparatus.

RESULTSWhen the cross-sectional dimension and the span were identical, the appliance stiffness of the box loops, double horizontal loops, and double vertical loops increased successively.

CONCLUSIONConfiguration of loops exert a great influence on appliance stiffness, and the mechanical properties of box loop are optimal. The force generated by box loop was lighter, slowly decreasing, and easier to be controlled. The activation range of box loop (0.41 mm) was appropriate when the produced optimal moment was between 0.01-0.02 N.m. Box loop (0.41 mm) is preferred to rectify the individual tooth with mild or moderate mesiodistal displacement.

OBJECTIVETo evaluate the properties of orthodontic rectangular arch wires in torsion.

METHODSTo measure and analyze the torsional moments and angles of 0.46 mm x 0.63 mm rectangular orthodontic arch wires in single 0.022 inch bracket of the maxillary central incisor with a torsion measurement apparatus.

RESULTS(1) The torsional stiffness of stainless steel arch wires, Chinese nitinol arch wires, 7.0 mm vertical loop arch wires, 3.0 mm and 6.0 mm horizontal loop arch wires is 4.909, 1.325, 4.137, 3.448 and 3.024 Nmm per degree, respectively. (2) The arch wires will be twisted 19.143, 36.832, 19.851, 21.812 and 22.418 degrees; respectively to obtain optimal force. (3) Vertical and horizontal loop decreased the torsional stiffness of the rectangular stainless steel arch wire.

CONCLUSIONThe straight rectangular stainless steel arch wire is not well suitable for the torque control of the incisor. Loop design in arch wire is capable of decreasing torsional stiffness. The horizontal loop is more effective than vertical loop.

OBJECTIVEThis study investigated the influence of Hawley retainer and vacuum-formed retainer on the articu-lation of Chinese speech of adult orthodontic patients.

METHODSA total of 20 volunteers were recruited in this randomized controlled trial in accordance with the inclusion criteria. Participants were randomly distributed into two groups, namely, the Hawley retainer group and the vacuum-formed retainer group. Speech performance was evaluated at the following time inter-vals: before wearing retainers (T0), immediately after wearing both upper and lower retainers (T1), 24 h later (T2), 1 week later (T3), and 1 month later (T4). The phonetic parameters were acquired through the use of computer-based voice analysis software Praat version 5.4.21, and the final data were analyzed using SPSS 19.0.

RESULTSBoth retainers can influence the phonetic parameters of vowels /e/, /i/, and /ü/ and consonants /s/, /f/, /x/, /t/, /j/, and /q/. However, the Hawley retainer showed a more remarkable effect on the articulation of Chinese speech, and the distortion of /i/, /ü/, and /s/ sounds can last for more than 1 month. Nevertheless, the recovery period of the patients' phonetic function in the vacuum-formed retainer group was within 1 month.

CONCLUSIONSBoth retainers can induce distortion of some Chinese vowels and consonants in the speech of adult orthodontic patients, but the Hawley retainer can more significantly influence the articulation of Chinese speech than vacuum-formed retainer.
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A double labial-arch retaining appliance to retain the treatment effective of Class III osteal malocclusion were introduced and used to retain 60 patients with Class III osteal malocclusion. At the same time, 60 patients with Class III osteal malocclusion were retained with conventional Hawley retainer as the control group. The results indicated that the double labial-arch retaining appliance has good effect to the retain of Class III osteal malocclusion.
Cephalometry ; Humans ; Male ; Malocclusion, Angle Class III ; Orthodontic Appliance Design

OBJECTIVETo measure the orthodontic forces exerted on the upper right central incisor with the increase of the distance of tooth movement and the thickness of the aligner.

METHODSThe labial movement of upper right central incisor at various distances (0.3, 0.6, 0.9, 1.2, 1.5, 1.8 mm) was designed and the stereolithography model (2 times bigger than the original model) was created with 3-D scanning and tomography output. These models were used to fabricate the aligners with different thicknesses (0.8, 1.0, 1.5 and 2.0 mm) of the thermoplastic materials (6 samples for various distances of tooth movement and thicknesses). Orthodontic forces exerted on the upper right central incisor were measured with the micro-stress sensor measurement system.

RESULTSThe orthodontic forces increased with the increase of the thickness of the aligner at the same distance of tooth movement (P < 0.05). The orthodontic force was (1.237 ± 0.082), (1.543 ± 0.059), (3.602 ± 0.102), (6.734 ± 0.063) N when the labial movement of upper right central incisor was 0.3 mm with the aligner of 0.8, 1.0, 1.5, 2.0 mm. The orthodontic forces also increased with the increase of the distance of the tooth movement at the same thickness of the aligner(P < 0.05). The orthodontic force of the aligner of 0.8 mm were (1.354 ± 0.039), (1.288 ± 0.037), (1.479 ± 0.031), (1.799 ± 0.039) N when the upper right central tooth labial movement at 0.6, 0.9, 1.2, 1.5 mm.

CONCLUSIONSThe orthodontic forces increased with the increase of the distance of tooth movement and the thickness of the aligner.

Humans ; Malocclusion, Angle Class I ; therapy ; Orthodontic Appliance Design

It is to address torquing an individual tooth using a gate spring. The gate spring is made of a rectangular stainless steal wire, in the shape of a gate, which is incorporated to the archwire by spot welding. Torque is generated by the combined effects of the gate spring and the archwire. After 2-3 months, the gate spring can obviously torque individual tooth.
Orthodontic Appliance Design ; Orthodontic Brackets ; Orthodontic Wires ; Tooth ; Tooth Movement Techniques ; Torque

Z2 appliance is the pre-adjusted appliance designed for Chinese orthodontic patients. The prescription of the appliance is based on Chinese normal occlusion, which is much different from the West in the first and the second orders as well as the third one. The appliance routinely includes 20 brackets and 8 molar buccal tubers with 3 standard arch forms. Clinically, continued light force is used in whole treatment. The side-effects such as forward tipping of incisors, bite deepening and loss of molar anchorage are reduced further due to fewer tips built into the anterior brackets as well as lower friction elastometric modules used during aligning and leveling. In condition of arch are leveled completely, 0.48 mm x 0.64 mm stainless steel archwire with 1.47 N retraction force is the best combination for sliding mechanics, which is proved by 3D nonlinear finite element study. Self drilling micro-screw is used for maximum anchorage. In finishing stage 0.53 mm x 0.64 mm NT arch wire is added in order to get full torque expressing. The research of Chinese pre-adjusted appliance has been lasted for more than 10 years in the department and clinical studies on Z2 appliance show that with minimal wire bending, treatment is more efficient and result is high quality and more consistent for Chinese orthodontic patients.
Dental Occlusion ; Friction ; Humans ; Incisor ; Molar ; Orthodontic Appliance Design ; Orthodontic Brackets ; Orthodontic Wires ; Stainless Steel