Frictional forces when rectangular guiding arches with varying edge bevel are employed

A Comparison of Surface Characteristics, Coating Stability and Friction Coefficients of Esthetic Archwires: A Comparative Study

Aim:

The aim of this article is to evaluate coated orthodontic aligning archwires for surface characteristics, coating stability, and associated dynamic frictional resistance and to compare and relate these results to each other. Materials and Methods: The archwire investigated were (1) group 1: American orthodontics (0.016 NiTi) (AO); (2) group 2: G and H Wire Company, USA (0.016) (G and H); (3) group 3: Orthosystems (0.016) (OS); and (4) group 4: Forestadent, Bio Cosmetic (0.017) (BC) Surface roughness (ESEM), coating stability, and frictional resistance were tested. Analysis of variance and Bonferroni test were used for analysis.

Results:

Frictional resistance from low to high—BC, AO, OS, G, and H. Coating stability from low to high—BC, AO, G and H, and OS. Surface characteristics from low to high—BC, OS, AO, G, and H.

Conclusions:

The study showed that BC has least friction coefficient, best coating stability, and less surface irregularities. Surface characteristics, friction coefficient, and coating stability may have correlation but are not statistically significant because of multifactorial conditions in the oral environment.

Comparation of three methods for measuring the Edge Bevel Radius of rectangular orthodontic wires: An in-vitro study

OBJECTIVE

To establish a simplified method for measuring the edge bevel radius of 0.019×0.025-in steel rectangular orthodontic wires, achievable in the clinical environment, and to compare it with the photographic method.

MATERIALS AND METHODS

Aided by the AutoCAD™ 2016 software, the theoretical mathematical relationship was determined between the edge rounding radius and cross-sectional dimensions (height, width, diagonals), through rectangle drawings that represent cross-sections. Two hundred segments (n=20) were obtained from the posterior portions of 100 archwires from 10 brands (Dentaurum™; American-Orthodontics™; GAC™; 3M-Unitek™; Abzil™; Morelli™; Orthometric™; Aditek™; A-Company™; Orthomundi™). The cross-sectional measures of each segment were obtained with a micrometer and a caliper, and the edge bevel radii of these segments were calculated with the use of a mathematical formula. For the "gold standard", the segments were included longitudinally in a phenolic resin cylinder, cross-sectioned, polished, and photographed in scanning electron microscope (SEM). The images were amplified 770× and the radii were measured with an acetate template. The micrometer and caliper measuring methods were subjected to Bland-Altman analysis and compared with the gold standard (SEM), considering ±10μm as the maximum acceptable difference between methods.

RESULTS

In the micrometre measurement, 95% of the differences from the standard were within the limits of agreement (-7.21 and 5.56μm). For the caliper method, 95% of the differences were between -5.46 and 19.83μm, which exceeded the fixed limit ±10μm.

CONCLUSION

The calculation method with micrometre measurements is equivalent to the photographic method, but there is no such equivalence for the caliper measurements.

A systematic review and meta-analysis of experimental clinical evidence on initial aligning archwires and archwire sequences

The aim of the study was to assess treatment effects and potential side effects of different archwires used on patients receiving orthodontic therapy. Electronic and manual unrestricted searches were conducted in 19 databases including MEDLINE, Cochrane Library, and Google Scholar until April 2012 to identify randomized controlled trials (RCTs) and quasi-RCTs. After duplicate study selection, data extraction, risk of bias assessment with the Cochrane risk of bias tool, and narrative analysis, mean differences (MDs) with confidence intervals (CIs) of similar studies were pooled using a random-effects model and evaluated with GRADE. A total of 16 RCTs were included assessing different archwire characteristics on 1108 patients. Regarding initial archwires, meta-analysis of two trials found slightly greater irregularity correction with an austenitic-active nickel-titanium (NiTi) compared with an martensitic-stabilized NiTi archwire (corresponding to MD: 1.11 mm, 95% CI: -0.38 to 2.61). Regarding archwire sequences, meta-analysis of two trials found it took patient treated with a sequence of martensitic-active copper-nickel-titanium (CuNiTi) slightly longer to reach the working archwire (MD: 0.54 months, 95% CI: -0.87 to 1.95) compared with a martensitic-stabilized NiTi sequence. However, patients treated with a sequence of martensitic-active CuNiTi archwires reported general greater pain intensity on the Likert scale 4 h and 1 day after placement of each archwire, compared with a martensitic-stabilized NiTi sequence. Although confidence in effect estimates ranged from moderate to high, meta-analyses could be performed only for limited comparisons, while inconsistency might pose a threat to some of them. At this point, there is insufficient data to make recommendations about the majority of initial archwires or for a specific archwire sequence.

Three-dimensional relationship between the critical contact angle and the torque angle

The purpose of this study was to analyze the relationship between the critical contact angle and the torque angle in an orthodontic bracket and archwire assembly in 3 dimensions. Three-dimensional mathematical models were created with geometric bracket-archwire parameters that included 2 slot sizes, 3 bracket widths, and 3 to 4 wire sizes. From this, 3-dimensional mathematical equations (3DMEs) for the critical contact angle and the maximum torque that result in critical contact angles of 0 were derived and calculated. To evaluate the effects of archwire-bracket parameters on critical contact angles, analysis of variance (ANOVA) was performed at the significance level of P < or = .05. For all bracket-archwire combinations, the critical contact angle decreased as bracket width, torque angle, and wire size increased. Therefore, all bracket-archwire parameters except slot height had an effect on the critical contact angle. Results of the critical contact angle produced from our 3DMEs were the same as those produced by 3D computer-aided design (SolidWorks Corp, Concord, Mass), thus confirming the validity of our derived equations. In addition, the effect of a beveled edge was investigated in some archwires. Furthermore, torsional play angles were calculated and found to be similar to those in previous reports. The results of this study provide theoretic and experimental bases for clinical orthodontic practice and indicate that torque angles should be included in the evaluation of the critical contact angle.

Lingual orthodontics (part 2): archwire fabrication

One essential component of a successful lingual treatment concept is the precise calculation and manufacture of individual lingual arch wires. As in several parts of daily life, the use of modern CAD/CAM technology leads in lingual orthodontic treatment to a rationalisation of working processes with maximized precision. The lingual module developed by the author is a new scanner-independent procedure for calculation and manufacture of individual lingual arch wires with the Orthomate/Orthotherm system (OrthoTel, Berlin/Dallas, Tx). Especially the precise individualization of superelastic, shape-memory materials reduces the archwire sequence and simplifies lingual treatment considerably. Individual second and third order overcorrections (incisal torque, reverse curve of Spee) can be programmed into the first archwire, with further three-dimensional corrections being added for each single tooth during finishing. Embedded in a systematic treatment concept, the use of modern CAD/CAM technology for individual lingual archwire production with the Orthomate/Orthotherm system is an important aid to successful integration of lingual orthodontic treatment into routine practice.

The influence of bracket design on frictional losses in the bracket/arch wire system

In arch guided tooth movement, the essential role played by bracket configuration with respect to sliding friction has been recognized by the manufacturers, a fact which has had an increasing impact on the design and marketing of new bracket models in recent years. The aim of the present in-vitro study was to investigate the influence of different bracket designs on sliding mechanics. Five differently shaped stainless steel brackets (Discovery: Dentaurum, Damon SL: A-Company, Synergy: Rocky Mountain Orthodontics, Viazis bracket and Omni Arch appliance: GAC) were compared in the 0.022"-slot system. The Orthodontic Measurement and Simulation System (OMSS) was used to quantify the difference between applied force (NiTi coil spring, 1.0 N) and orthodontically effective force and to determine leveling losses occurring during the sliding process in arch guided tooth movement. Simulated canine retraction was performed using continuous arch wires with the dimensions 0.019" x 0.025" (Standard Steel, Unitek) and 0.020" x 0.020" (Ideal Gold, GAC). Comparison of the brackets revealed friction-induced losses ranging from 20 to 70%, with clear-cut advantages resulting from the newly developed bracket types. However, an increased tendency towards leveling losses in terms of distal rotation (maximum 15 degrees) or buccal root torque (maximum 20 degrees) was recorded, especially with those brackets giving the arch wire increased mobility due to their shaping or lack of ligature wire.