Frictional behavior of stainless steel bracket-wire combinations subjected to small oscillating displacements

A Comparative Evaluation of Frictional Resistance of Various Lingual Brackets With Nitinol (NiTi) Archwires of Different Dimensions: An In Vitro Study

Introduction Orthodontic mechanics involves transferring some of the applied force to the tooth's supporting components via friction, which in turn allows the tooth to move more easily. Aim The purpose of this in vitro experiment was to examine the frictional resistance (FR) of different lingual brackets utilizing Instron universal testing machines and nitinol (NiTi) archwires of varying sizes. Materials and methods Twenty-four sectional anterior die stones were replicated from a study model. They were categorized into eight categories, with the Libral lingual bracket and the JJ lingual bracket having 0.012" and 0.014" inch NiTi archwire, which were further subdivided into six subgroups. Three brackets were bonded to the anterior teeth of the upper and lower segments and replicated on other models with the help of silicon putty. Elastomeric modules were ligated to two diameters of NiTi wire (0.012" and 0.014") in each model. An Instron universal testing machine was used to measure the frictional force. Numerical data and descriptive statistics such as mean and standard deviation have been shown. Results In the overall analysis, it was observed that among JJ Orthodontics samples using 0.012" NiTi archwires, the maxilla exhibited a higher FR (4.205N) compared to the mandible (4.092N). Similarly, in the case of Libral Orthodontics samples with 0.012" NiTi archwires, the maxilla also demonstrated a higher FR (5.10N) than the mandible (4.97N). However, this trend did not hold for samples using 0.014" NiTi archwires. There was a statistically nonsignificant difference (p > 0.05) in the values between all the pairs of groups. Conclusion The present study concludes that Libral lingual brackets produced overall more FR than JJ lingual brackets.

Comparison of the frictional characteristics of aesthetic orthodontic brackets measured using a modified in vitro technique

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 × 0.025-in wire in the 0.018-in slots and a 0.019 × 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 (α = 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 (µ = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (µ = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (µ = 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.

Coating NiTi archwires with diamond-like carbon films: reducing fluoride-induced corrosion and improving frictional properties

This study aims to coat diamond-like carbon (DLC) films onto nickel-titanium (NiTi) orthodontic archwires. The film protects against fluoride-induced corrosion and will improve orthodontic friction. 'Mirror-confinement-type electron cyclotron resonance plasma sputtering' was utilized to deposit DLC films onto NiTi archwires. The influence of a fluoride-containing environment on the surface topography and the friction force between the brackets and archwires were investigated. The results confirmed the superior nature of the DLC coating, with less surface roughness variation for DLC-coated archwires after immersion in a high fluoride ion environment. Friction tests also showed that applying a DLC coating significantly decreased the fretting wear and the coefficient of friction, both in ambient air and artificial saliva. Thus, DLC coatings are recommended to reduce fluoride-induced corrosion and improve orthodontic friction.

Changes in the surface roughness and friction coefficient of orthodontic bracket slots before and after treatment

In this study, we tested the surface roughness of bracket slots and the friction coefficient between the bracket and the stainless steel archwire before and after orthodontic treatment. There were four experimental groups: groups 1 and 2 were 3M new and retrieved brackets, respectively, and groups 3 and 4 were BioQuick new and retrieved brackets, respectively. All retrieved brackets were taken from patients with the first premolar extraction and using sliding mechanics to close the extraction space. The surface roughness of specimens was evaluated using an optical interferometry profilometer, which is faster and nondestructive compared with a stylus profilometer, and provided a larger field, needing no sample preparation, compared with atomic force microscopy. Orthodontic treatment resulted in significant increases in surface roughness and coefficient of friction for both brands of brackets. However, there was no significant difference by brand for new or retrieved brackets. These retrieval analysis results highlight the necessity of reevaluating the properties and clinical behavior of brackets during treatment to make appropriate treatment decisions.

Effects of deflection and archwire dimension on the mechanical performance of two self-ligating orthodontic systems

OBJECTIVES

To analyze the effects of archwire deflection and dimension on the mechanical performance of two self-ligating systems, as passive and active ligation designs.

MATERIALS AND METHODS

An experimental model was used that was designed to resemble the full dental arch and to allow vertical displacement of a canine element. Two self-ligating systems were investigated: 1) a passive system; and 2) an active system, both in combination with three thermoactive NiTi archwires, with round sections of 0.014-in, 0.016-in and 0.018-in. The full loading-unloading cycles consisted of either 3mm or 6mm maximum deflection, performed at 37 °C. During unloading, the deactivation forces and energy were recorded. The ratio between the deactivation and activation energies was used as representative of the mechanical efficiencies of the systems.

RESULTS

The deactivation force increased in combination with larger archwires and greater deflection. The deactivation energy increased in combination with larger archwires only for the 3-mm deflection cycle, while for the 6-mm deflection cycle, the deactivation energy was not influenced by the archwire dimension, and was not greater than that of the 3-mm deflection cycle. The mechanical efficiency decreased in combination with greater deflection and larger archwires, with a maximum decrease of about 12%. Only minor comparative differences were seen between the systems.

CONCLUSIONS

The deflection degree and archwire dimension have large effects on the mechanical performance of self-ligating systems.

The clinical and laboratory effects of bracket type during canine distalization with sliding mechanics

OBJECTIVE

To compare the extent of canine movement with sliding mechanics between a self-ligating (SC) bracket and a modified twin design (MT) bracket. To test the in vitro coefficient of friction (COFs) of these two metal brackets on 0.019- × 0.025-inch, stainless-steel arch wires.

MATERIALS AND METHODS

For the clinical portion of this study, a split-mouth design was used to bond the brackets of 19 patients. Canine distalization was achieved on a 0.019- × 0.025-inch, stainless-steel arch wire with a nickel-titanium, closed-coil spring strained between a mini-screw and a canine bracket. The linear and angular measurements were performed using lateral cephalometric radiographs taken before and after canine distalization. A tribometer was also used to measure the COFs of the bracket types in vitro. For comparisons, Student's t-tests for paired and unpaired samples were used at the 95% confidence level.

RESULTS

The extent of canine movement and the changes in the canine and molar teeth angles were not significantly different between the SC and MT brackets. After 8 weeks, the mean canine movements were 1.83 and 1.89 mm in the maxilla and 1.79 mm and 1.70 mm in the mandible with the SC and MT brackets, respectively. The mean COF of the MT brackets (0.21) was significantly lower than that of the SC brackets (0.37) during in vitro testing.

CONCLUSION

It is suggested that the rate of canine distalization was not different between the two groups, although in vitro COFs of the SC bracket was higher.

In vitro friction of stainless steel arch wire-bracket combinations in air and different aqueous solutions

OBJECTIVES

To investigate the in vitro coefficient of friction of stainless steel arch wire-bracket combinations under fretting contact test conditions performed in air and in different aqueous solutions, like Ringer solution, Ringer with addition of a buffer, Ringer with addition of glucose, and Coca Cola.

METHODS

The fretting test set-up used allowed to control on-line the contact configuration and the positioning of the contacting parts. A specific positioning method was used to achieve a parallel alignment of arch wire and bracket slot. The effect of arch wire size, roughness, and test environment were investigated.

RESULTS

It was found that the aqueous solutions act as a lubricant compared to air. Friction was affected by the arch wire width while the roughness was found to have a limited effect. Stainless steel 0.018'' x 0.025'' arch wires exhibited higher frictional forces than stainless steel 0.017'' x 0.025'' arch wires on sliding against stainless steel 0.018'' x 0.025'' brackets in the selected test environments when tested under identical fretting test conditions. The wear damage on the arch wire after these in-vitro fretting tests was investigated. It revealed that these in-vitro tests are governed by a competition between oxidational wear and abrasive wear taking place at contact areas between brackets and arch wires.

CONCLUSIONS

For all aqueous solutions a lower coefficient of friction was found compared to tests performed in ambient air.

In vitro study of frictional forces during sliding mechanics of "reduced-friction" brackets

This study evaluated the static friction force created between archwires and "reduced-friction" brackets during sliding mechanics. Five different brands of "reduced-friction" brackets were used: group A: NuEdge (TP Orthodontics, LaPorte, Ind); group B: Discovery (Dentaurum, Ispringen, Germany); group C: Synergy (Rocky Mountain Orthodontics, Denver, Colo); group D: Friction Free (American Orthodontics, Sheboygan, Wis); and group E: TIME, a self-ligating bracket (American Orthodontics). Group F (Omni Arch, GAC International, Bohemia, NY) served as a control group. Each group contained 75 stainless steel brackets with.022 x.028-in slots. Three stainless steel wires were tested:.018,.018 x.025, and.019 x.025 in. To take second-order bends into account, the brackets were set at either 5 degrees or 10 degrees to the wires. Each bracket was set in a special device, which was placed on the base of the testing machine. A wire ligated to the bracket was attached to the crosshead of the machine and pulled at a speed of 10 mm/min for a distance of 5 mm. Significant differences were found in the static friction forces among the different groups. Group D (Friction Free) showed the lowest and group E (TIME) showed the highest friction forces (higher than the normal friction brackets [Omni Arch]). This study demonstrates that not all brackets provide "reduced friction," even though the manufacturers describe them as doing so.