Excessive forces may cause root resorption and insufficient forces would introduce no effect in orthodontics. The objective of this study was to investigate the optimal orthodontic forces on a maxillary canine, using hydrostatic stress and logarithmic strain of the periodontal ligament (PDL) as indicators. Finite element models of a maxillary canine and surrounding tissues were developed. Distal translation/tipping forces, labial translation/tipping forces, and extrusion forces ranging from 0 to 300 g (100 g=0.98 N) were applied to the canine, as well as the force moment around the canine long axis ranging from 0 to 300 g·mm. The stress/strain of the PDL was quantified by nonlinear finite element analysis, and an absolute stress range between 0.47 kPa (capillary pressure) and 12.8 kPa (80% of human systolic blood pressure) was considered to be optimal, whereas an absolute strain exceeding 0.24% (80% of peak strain during canine maximal moving velocity) was considered optimal strain. The stress/strain distributions within the PDL were acquired for various canine movements, and the optimal orthodontic forces were calculated. As a result the optimal tipping forces (40-44 g for distal-direction and 28-32 g for labial-direction) were smaller than the translation forces (130-137 g for distal-direction and 110-124 g for labial-direction). In addition, the optimal forces for labial-direction motion (110-124 g for translation and 28-32 g for tipping) were smaller than those for distal-direction motion (130-137 g for translation and 40-44 g for tipping). Compared with previous results, the force interval was smaller than before and was therefore more conducive to the guidance of clinical treatment. The finite element analysis results provide new insights into orthodontic biomechanics and could help to optimize orthodontic treatment plans.
Biomechanical Phenomena ; Computer Simulation ; Cuspid ; anatomy & histology ; physiology ; Dental Models ; Finite Element Analysis ; Humans ; Imaging, Three-Dimensional ; Maxilla ; Orthodontic Friction ; physiology ; Periodontal Ligament ; physiology ; Rotation ; Stress, Mechanical ; Tooth Movement Techniques ; statistics & numerical data

OBJECTIVE: This study aimed to compare the frictional force (FR) in self-ligating brackets among different bracket-archwire angles, bracket materials, and archwire types. METHODS: Passive and active metal self-ligating brackets and active ceramic self-ligating brackets were included as experimental groups, while conventional twin metal brackets served as a control group. All brackets were maxillary premolar brackets with 0.022 inch [in] slots and a -7degrees torque. The orthodontic wires used included 0.018 round and 0.019 x 0.025 in rectangular stainless steel wires. The FR was measured at 0degrees, 5degrees, and 10degrees angulations as the wire was drawn through the bracket slots after attaching brackets from each group to the universal testing machine. Static and kinetic FRs were also measured. RESULTS: The passive self-ligating brackets generated a lower FR than all the other brackets. Static and kinetic FRs generally increased with an increase in the bracket-archwire angulation, and the rectangular wire caused significantly higher static and kinetic FRs than the round wire (p < 0.001). The metal passive self-ligating brackets exhibited the lowest static FR at the 0degrees angulation and a lower increase in static and kinetic FRs with an increase in bracket-archwire angulation than the other brackets, while the conventional twin brackets showed a greater increase than all three experimental brackets. CONCLUSIONS: The passive self-ligating brackets showed the lowest FR in this study. Self-ligating brackets can generate varying FRs in vitro according to the wire size, surface characteristics, and bracket-archwire angulation.
Bicuspid ; Ceramics ; Friction* ; Humans ; Orthodontic Wires ; Stainless Steel ; Torque

OBJECTIVE: The coefficients of friction (COFs) of aesthetic ceramic and stainless steel brackets used in conjunction with stainless steel archwires were investigated using a modified linear tribometer and special computer software, and the effects of the bracket slot size (0.018 inches [in] or 0.022 in) and materials (ceramic or metal) on the COF were determined. METHODS: Four types of ceramic (one with a stainless steel slot) and one conventional stainless steel bracket were tested with two types of archwire sizes: a 0.017 x 0.025-in wire in the 0.018-in slots and a 0.019 x 0.025-in wire in the 0.022-in slot brackets. For pairwise comparisons between the 0.018-in and 0.022-in slot sizes in the same bracket, an independent sample t-test was used. One-way and two-way analysis of variance (ANOVA) and Tukey's post-hoc test at the 95% confidence level (alpha = 0.05) were also used for statistical analyses. RESULTS: There were significant differences between the 0.022-in and 0.018-in slot sizes for the same brand of bracket. ANOVA also showed that both slot size and bracket slot material had significant effects on COF values (p < 0.001). The ceramic bracket with a 0.022-in stainless steel slot showed the lowest mean COF (micro = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (micro = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (micro = 0.85). CONCLUSIONS: Brackets with stainless steel slots exhibit lower COFs than ceramic slot brackets. All brackets show lower COFs as the slot size increases.
Aluminum Oxide ; Ceramics ; Friction* ; Orthodontic Brackets* ; Stainless Steel

OBJECTIVEFrictions of Lock-loose brackets with ligated main wings or all six wings were measured as they slid along archwires in dry and artificial saliva environments. The Lock-loose brackets were then compared with traditional brackets and self-ligating brackets.

METHODSThe surface states of the stainless steel archwires were observed with atomic force microscopy before and after mechanical traction. The Lock-loose brackets, traditional brackets, and self-ligating brackets used in this study were composed of 0.406 4 and 0.457 2 mm stainless steel round archwires and 0.457 2 mm x 0.634 9 mm and 0.482 6 mm x 0.634 9 mm stainless steel rectangular archwires. Two different ligating methods were applied to the Lock-loose brackets, i.e., main wings ligated and all six wings ligated. Frictions were measured by using an electronic universal testing machine.

RESULTSNo significant differences were found between the roughness of different archwires before and after mechanical traction in different brackets (P > 0.05). When the main wings of the Lock-loose brackets were ligated, the frictions of the four different stainless steel archwires were close to zero, and the difference with frictions of traditional brackets was significant (P < 0.05). When using 0.457 2 mm x 0.634 9 mm rectangular archwires, maximum friction (P < 0.05; significantly different from those of other brackets) was reached when all six wings of the Lock-loose brackets were ligated. Frictions in the dry state were higher than those in the wet state (P < 0.05).

CONCLUSIONThe Lock-loose brackets can adjust the friction efficiently with different ligating methods, thus solving the problem of low friction and strengthening anchorage.

OBJECTIVE: The purpose of this study was to evaluate the difference in frictional resistance among metal, ceramic, self-ligation brackets and coated or non-coated Ni-Ti archwires at various bracket-archwire angulations during the sliding movement of an orthodontic archwire, using an orthodontic sliding simulation device. METHODS: Four types of bracket (Micro-arch Perpect Clear2 Clippy-C and Damon3 and 5 types of orthodontic archwire (0.014", 0.016", and 0.016" x 0.022" inch coated Ni-Ti, and 0.016" and 0.016" x 0.022" inch Ni-Ti) were used. Further, the bracket-archwire angles were set at 4 different angulations: 0degrees, 3degrees, 6degrees, and 9degrees. RESULTS: The frictions from all the experimental groups were found to be significantly increased in order of self-ligation brackets, Micro-arch and Perpect Clear2 (p < 0.001). The presence of a coat had no effect on the friction of the same sized archwires at 0degrees and 3degrees bracket-archwire angles (p < 0.001). Coated archwires had significantly higher frictions than the same sized non-coated archwires at 6degrees and 9degrees bracket-archwire angles (p < 0.001). The frictions increased significantly as the bracket-archwire angles were increased (p < 0.001). CONCLUSIONS: The use of self-ligation brackets will be beneficial in clinical situations where a low frictional force is required. Further, in cases where crowding is not severe, the use of coated archwires should not cause problems. However, more additional explanation is required considering the fact that the damage of coated archwire and exposure of the metal portion in case of binding and notching and the effects of saliva were not taken into account.
Ceramics ; Crowding ; Friction ; Nickel ; Orthodontic Brackets ; Saliva ; Titanium

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

OBJECTIVETo measure the frictions between FAS bracket and stainless steel wire under different two conditions, and compare two traditional self-ligating brackets.

METHODSFAS bracket was a new-style self-ligating bracket with a friction adjusting system (FAS) to adjust the friction as the wires slide in the bracket. Firstly, FAS bracket 20 times of original size was made, then the frictions were measured respectively made by the steel round wires of diameters 8.128 0 mm or the steel square wires in size of 9.1440 mm x 12.7000 mm. It was divided into two adjusting states, and used the same method to measure Damon III and SPEED bracket in 20 times of original size.

RESULTSWith the shim entirely drew in, all the frictions of the arch wire had no significant difference with the Damon III. When 8.1280 mm stainless steel round wire was used, SPEED bracket had no significant difference with FAS. When 9.1440 mm x 12.7000 mm square wire was used, they had significant difference (P < 0.05). On turning half a circle, all the frictions of the arch wire had significant difference with two tradition bracket (P < 0.01).

CONCLUSIONThe new-style FAS bracket can adjust the friction efficiently. Under no pressure state, the friction force is similar to Damon III. Under pressure state, FAS bracket locks the wires, and provides the sliding of wires.

OBJECTIVE: The purpose of this study was to compare changes in frictional resistance between the bracket and wire under dry and wet conditions according to a change in moment. METHODS: A stainless steel bracket of 0.022" x 0.028" slot, and 0.019" x 0.025" stainless steel, beta-titanium, and nickel-titanium wires were used. A 10 mm length lever was attached to the test (sliding) brackets to generate a moment. The experimental model was designed to allow tipping until contacts were established between the wire and the mesiodistal edges of the bracket slot. The moment was generated by suspending a 100 g or 200 g weight on the end of the lever. The moments applied were 1000 g.mm (100 g x 10 mm) and 2000 g.mm (200 g x 10 mm). The test brackets were ligated with elastomeric ligature for a constant ligation force and the fixed brackets were ligated with stainless steel ligature. Brackets were moved along the wire by means of an universal testing machine, and maximum frictional resistances were recorded. RESULTS: Stainless steel wire showed least frictional resistance and there was no significant difference between beta-titanium and nickel-titanium except at 2000 g.mm moment in wet conditions. Frictional resistance of all wires increased as the moment increased from 1000 g.mm to 2000 g.mm. Under wet conditions, the frictional resistance of stainless steel wires increased in both 1000 g.mm and 2000 g.mm moment conditions, but frictional resistance of nickel-titanium and beta-titanium increased only in 2000 g.mm conditions. CONCLUSION: These results indicated that various conditions influence on frictional resistance. Therefore, laboratory studies of frictional resistance should simulate clinical situation.
Elastomers ; Friction* ; Ligation ; Models, Theoretical ; Orthodontic Wires* ; Stainless Steel*

The purpose of this study was to measure and compare the level of frictional resistance generated from three currently used ceramic brackets; 1, Crystaline V(R), Tomy International Inc., Tokyo, Japan; 2, Clarity(R), 3M Unitek, Monrovia, CA, USA; 3, Inspire(R), Ormco, Orange, CA, USA; with composite resin brackets, Spirit(R), Ormco, Orange, CA, USA; and conventional stainless steel brackets, Kosaka(R), Tomy International Inc., Tokyo, Japan used as controls. In this experiment, the resistance to sliding was studied as a function of four angulations (0 degrees, 5 degrees, 10 degrees, and 15 degrees) using 2 different orthodontic wire alloys: stainless steel (stainless steel, SDS Ormco, Orange, CA, USA), and beta-titanium (TMA, SDS Ormco, Orange, CA, USA). After mounting the 22 mil brackets to the fixture and .019 x .025 wires ligated with elastic ligatures, the arch wires were slid through the brackets at 5 mm/min in the dry state at 34 degrees C. Silica-insert ceramic brackets generated a significantly lower frictional force than did other ceramic brackets, similar to that of stainless steel brackets. Beta-titanium archwires had higher frictional resistance than did stainless steel, and all the brackets showed higher static and kinetic frictional force as the angulations increased. When the angulation exceeded 5 degrees, the active configuration emerged and frictional force quickly increased by 2.5 to 4.5-fold. The order of frictional force of the different wire-bracket couples transposed as the angle increased. The silica-insert ceramic bracket is a valuable alternative to conventional stainless steel brackets for patients with esthetic demands.
Alloys ; Ceramics* ; Citrus sinensis ; Family Characteristics ; Friction* ; Humans ; Japan ; Ligation ; Orthodontic Wires ; Stainless Steel ; Steel

The object of this study was to evaluate how friction that occurs during the sliding movement of an orthodontic archwire through orthodontic brackets is differently affected by variant designs and ingredients of brackets and archwires and bracket-archwire angles. In order to simulate the situations which could occur during orthodontic treatment with fixed appliances, 4 types of brackets (Gemini(R), a stainless steel twin bracket; Mini Uni-Twin(R), a stainless steel bracket with a single bracket design and narrow mesio-distal width; Clarity(R), a metal-reinforced ceramic bracket; Transcend(R), a ceramic bracket) and 3 types of orthodontic archwires (0.016", 0.016 x 0.022" stainless steel, 0.016" Nitinol) were used and the bracket-archwire angles were controlled as 0 degrees, 3 degrees, 6 degrees, and 9 degrees, Gemini(R) significantly showed the lowest static and kinetic frictions (P < 0.001). Clarity showed the highest static and kinetic frictions with a bracket-archwire angle of 0 degrees, and Transcend at 6 degrees and 9 degrees (P < 0.001). An 0.016 x 0.022" stainless steel rectangular archwire significantly showed the highest static and kinetic frictions (P < 0.01). The lowest static and kinetic frictions were observed when the bracket-archwire angles were 0 degrees and 3 degrees with 0.016" stainless steel round archwires (P < 0.01), and 6 degrees and 9 degrees with 0.016 Nitinol (P < 0.001). The static and kinetic frictions were increased as the bracket-archwire angles were increased (P < 0.001).
Ceramics ; Friction* ; Humans ; Orthodontic Brackets* ; Stainless Steel