Frictional resistances of metal-lined ceramic brackets versus conventional stainless steel brackets and development of 3-D friction maps

The frictional resistances of 2 metal-lined ceramic brackets (Luxi and Clarity) were compared with 2 conventional stainless steel brackets (Mini-Taurus and Mini-Twin) in vitro. In method 1, we varied the second-order angulation from 0 degrees to 12 degrees while maintaining the normal or ligature force constant at 0.3 kg; in method 2, we varied the ligature force from 0.1 kg to 0.9 kg while maintaining the angulation at theta = 0 degrees or theta = 11 degrees. The hardware simulated a 3-bracket system in which the interbracket distances were always 18 mm. All couples were evaluated at 34 degrees C using the same size stainless steel archwire (19 x 26 mil) and ligature wire (10 mil). In the passive region, the static and kinetic frictional forces and coefficients of friction were key parameters; in the active region, the static and kinetic binding forces and coefficients of binding were critical parameters. From outcomes of methods 1 and 2, the 4 aforementioned parameters, and a knowledge of the critical contact angle for binding, 3-dimensional friction maps were constructed in the dry and wet states from which the frictional resistances could be determined at any ligature force or second-order angulation. Those 3-dimensional maps show that metal-lined ceramic brackets can function comparably to conventional stainless steel brackets and that 18-kt gold inserts appear superior to stainless steel inserts. As the morphologies of metal inserts are improved, these metal-lined ceramic brackets will provide not only good esthetics among ceramic brackets but also minimal friction among conventionally ligated brackets.     

Frictional resistance of ceramic and stainless steel orthodontic brackets

Frictional resistance of orthodontic appliances is recognized by most clinicians to be detrimental to tooth movement. The purpose of this study was to compare planar, static frictional forces among stainless steel and ceramic brackets. Both nitinol and stainless steel rectangular arch wires were passed freely through the slots of a pair of brackets from each type. Tests were carried out in air and in artificial saliva. A 300-gm load was suspended from the arch wire to simulate the normal force, and an incremental horizontal force was applied until movement of the arch wire was initiated. Under all conditions, the stainless steel brackets had lower coefficients of friction than the ceramic brackets. The stainless steel wire generated less friction than nitinol, and friction increased in the presence of artificial saliva in comparison with air alone. These results show that, under experimental conditions, ceramic brackets, nitinol arch wires, and saliva all increase static frictional resistance.     

陶瓷托槽与金属弓丝第二序列成角状态下摩擦性能的研究

目的研究陶瓷托槽与金属弓丝在第二序列成角状态下的摩擦力,探讨影响托槽弓丝间摩擦力的因素。方法进行托槽外观形貌的测量与观察,计算托槽与弓丝第二序列成角下的临界角,并设计带可调节罗盘的载物台,用MTS Tytron250微力试验机体外测试三种陶瓷托槽（A、B、C）和一种金属托槽（D）与0.016英寸不锈钢圆丝（SS）在第二序列成角分别为0度、2度、5度、8度时的最大静摩擦力和滑动摩擦力。结果与0.016英寸SS的摩擦力总体表现出B托槽〉C托槽〉A托槽〉D托槽的趋势,在四种成角状态下的最大静摩擦力随角度加大而增大,总体表现为0度到2度的摩擦力增加没有显著性,增大夹角后摩擦力增加量不同托槽间有差异：A托槽与弓丝在2度到5度成角状态下的摩擦力增加没有显著性,而5度到8度的摩擦力有显著增加;B托槽在2度到5度摩擦力有显著增加,而5度到8度摩擦力增加不显著;虽然2度到5度摩擦力增大没有显著性,但8度与0度状态下相比,C托槽与弓丝间的摩擦力有显著增加;D托槽在2度、5度、8度时摩擦力间差异无显著性。结论选用带金属槽沟的陶瓷托槽,增加陶瓷托槽边缘的圆钝程度等能减缓牙齿移动中托槽-弓丝成角引起的滑动阻力增加;使用传统陶瓷托槽要注意充分排齐。     

Resistance to sliding of self-ligating brackets versus conventional stainless steel twin brackets with second-order angulation in the dry and wet (saliva) states.

The frictional properties of conventional stainless steel brackets that were coupled with rectangular stainless steel archwires and ligated with stainless steel ligature wires and the frictional properties of closed self-ligating brackets coupled with the same archwires were compared in terms of second-order angulation. The slides of these self-ligating brackets passively restrained the archwires within the slots. As a control, the frictional properties of the opened self-ligating brackets, which were ligated with stainless steel ligature wires, were measured. The resistance to sliding of the conventional brackets and the opened self-ligating brackets were measured at ligation forces ranging from 200 to 600 cN and at angles from -9 degrees to 9 degrees. The resistances to sliding of the closed self-ligating brackets were measured at the same angles, but no external ligation forces were applied. In the passive configuration, the conventional brackets exhibited similar frictional resistance as the opened self-ligating brackets, whereas the closed self-ligating brackets exhibited no friction. In the active configuration, all brackets exhibited increased resistance to sliding as the angulation increased. At all angles, the resistances to sliding of the closed self-ligating brackets were lower than those of the conventional brackets because of the absence of a ligation force when the slide restrained the archwire.     

Canine retraction rate with self-ligating brackets vs conventional edgewise brackets

Objective:To compare the rates of retraction down an archwire of maxillary canine teeth when bracketed with a self-ligating bracket was used on one side and a conventional bracket on the other.Materials and Methods:In 43 patients requiring maxillary premolar extraction, a self-ligating bracket (Damon3, SmartClip) was used on the maxillary canine on one side and a conventional bracket (Victory Series) on the other. The teeth were retracted down a 0.018-inch stainless steel archwire, using a medium Sentalloy retraction spring (150 g). The rates of retraction were analyzed using a paired t-test.Results:The mean movement per 28 days for the conventional bracket was 1.17 mm. For the Damon bracket it was 0.9 mm and for the SmartClip bracket it was 1.10 mm. The differences between the conventional and self-ligating brackets were statistically significant: paired t-test, SmartClip, P < .0043; Damon3, P < .0001).Conclusion:The retraction rate is faster with the conventional bracket, probably because of the narrower bracket width of the self-ligating brackets.     

自锁托槽与普通直丝托槽矫治中尖牙远移速度的比较

目的：比较应用自锁托槽矫治器与普通直丝托槽矫治器矫治中尖牙向远中移动的速度。方法：选取需拔除上颌第一前磨牙的安氏Ⅱ1错颌患者40例,同一患者双侧上颌尖牙随机粘自锁托槽或普通直丝托槽,牙列排齐整平后,上颌换0．018英寸的不锈钢圆丝,用镍钛拉簧以150 g的力量,使上颌尖牙向远中移动。患者每隔28 d复诊1次。计算出使用不同托槽后尖牙向远中移动的速度。配对t检验进行统计分析。结果：普通直丝托槽矫治器尖牙向远中移动的速度明显快于自锁托槽矫治器（P﹤0．01）。结论：很多因素可以影响自锁托槽矫治器的摩擦力。     

Influence of ceramic and stainless steel brackets on the notching of archwires during clinical treatment

The surface topography of 100 clinically used archwires of stainless steel, beta-, or nickel-titanium were investigated that had contacted either ceramic or stainless steel brackets. One group consisted of two sets: 60 wires with no treatment records accessed to bias analyses, and 40 wires for which extensive clinical records were available, half of which were used with ceramic or stainless steel brackets. A control group consisted of two sets: 30 unused wires comprised of five round and rectangular wires of each alloy, and four wires that were ligated and immediately removed from patients' mouths. After ultrasonic cleaning, each wire was inspected under an optical and/or a scanning electron microscope. Notches were categorized with regard to frequency, patterns, and severity, and mapped as a function of wire aspect (lingual, facial, and occlusal/gingival) and anatomical regions (molar, premolar, canine, and incisor). From these data the average severity of notch patterns and a notching index were derived. Although no recognizable defect patterns were observed in the control group, seven basic patterns were recognized for each wire cross-sectional shape in the clinically used wires. These wires appeared most damaged on their lingual aspect and least damaged on their facial aspect. With regard to anatomical regions, notching was prevalent in the anterior regions and sparse in the molar regions. The notch activity and the severity were nearly three times greater from ceramic brackets than from stainless steel brackets. Over one-third of all notches documented in ceramic bracket cases had severity numbers of 3 and penetrated at least one-quarter of each wire's dimension, However, over two-thirds of all notches documented in stainless steel bracket cases had severity numbers of 1. From these tabulations a theory of notch formation was proposed in which vertical movement from tooth or wire during mastication caused fretting wear, and horizontal movement during orthodontic procedures such as space closure, tipping, or bodily movement caused sliding wear.     

The shear bond strengths of stainless steel and ceramic brackets used with chemically and light-activated composite resins

Since the introduction of ceramic brackets to orthodontic therapy, a need has arisen to test the manufacturer's claims regarding these brackets. Forty-eight noncarious human canine teeth were divided equally into groups A to D. Brackets were bonded to these teeth with the use of the acid-etch technique and a composite resin according to the manufacturer's instructions. The combination within each group was as follows: A = stainless steel brackets and chemically cured resin; B = ceramic brackets and chemically cured resin; C = ceramic brackets and light-cured resin; D = stainless steel brackets and light-cured resin (via transillumination). After curing, the teeth were stored for 1 week in distilled water at 37 degrees C. The Instron machine was used to test the shear bond strengths of the brackets to the teeth. The brackets were individually tested to failure of the bond, which was recorded along with the site of fracture. The conclusions are as follows: (1) all combinations produced shear bond strengths that were greater than those that are considered clinically acceptable, (2) the ceramic groups exhibited a significantly higher bond strength than that of the stainless steel group, and (3) enamel fractures occurred among the B group in 40% of the samples tested in that group. It is thus apparent that a fracture of enamel is a real possibility during therapy or at debonding of the ceramic brackets, especially if the tooth is nonvital.     

Torque expression of self-ligating brackets compared with conventional metallic, ceramic, and plastic brackets

The purpose of this research was to investigate the torque capacity of active and passive self-ligating brackets compared with metallic, ceramic, and polycarbonate edgewise brackets. Six types of orthodontic brackets were included in the study: the self-ligating Speed and Damon2, the stainless steel (SS), Ultratrimm and Discovery, the ceramic bracket, Fascination 2, and the polycarbonate bracket, Brillant. All brackets had a 0.022-inch slot size and were torqued with 0.019 x 0.025-inch SS archwires. For this purpose, the labial crown torque of an upper central incisor was measured in a simulated intraoral clinical situation using the orthodontic measurement and simulation system (OMSS). A torque of 20 degrees was applied and the correction of the misalignement was simulated experimentally with the OMSS. Each bracket/wire combination was measured five times. Maximum torquing moments and torque loss were determined. The results were analysed with one-way analysis of variance, with the bracket serving as the sole discriminating variable, and the Tukey test at the 0.05 level of significance. The ceramic bracket (Fascination 2) presented the highest torquing moment (35 Nmm) and, together with a SS bracket, the lowest torque loss (4.6 degrees). Self-ligating, polycarbonate, and selective metallic brackets demonstrated almost a 7-fold decreased moment developed during insertion of a 0.019 x 0.022-inch SS wire into a 0.022-inch slot and a 100 per cent increase in loss.     

Elastic flexural properties of multistranded stainless steel versus conventional nickel titanium archwires

Based on a recent investigation that modeled the elastic properties (ie, strength, stiffness and range) of multistranded wires made from linearly elastic materials, three-stranded (triple) and six-stranded coaxial (coax) stainless steel (SS) wires were compared to single-stranded (single) SS and conventional nickel titanium (NiTi) leveling wires. To measure Young's modulus of elasticity (E), flexural tests were performed with an Instron mechanical testing machine in a three-point bending arrangement having a span length of 8.9 mm or 12.5 mm. A strong correlation between wire stiffness and the area moment of inertia demonstrated that strand interaction was negligible at low activations and that E = 199 GPa was constant even for the heavily drawn coax strands. Using the Instron with an extensometer, the 0.1% yield strengths (sigma(YS)) of the single SS wires and the straight inner strands within the coax wires were tested. The ratio of the sigma(YS) to the ultimate tensile strength averaged 0.81 for the single wires, 0.88 for the coax wires, and was subsequently assigned 0.85 for the triple wires. The average sigma(YS) values were 1.88, 1.83, and 1.78 GPa for the single, triple, and coax SS wires, respectively. For each NiTi wire, both the sigma(YS) and the elastic limit (sigma(EL)) via cyclic loading were measured. The conventional NiTi wires displayed nonlinear elasticity, as the average sigma(EL) values (1.10 GPa) were 50% higher than the average sigma(YS) values (0.73 GPa). Compared to the elastic properties of the conventional NiTi wires, the triple and coax SS wires generally matched the stiffness, but had only one-third to one-half of the strength and range. Since the properties of strength and range are both proportional to sigma(YS), fabrication using alloys with enhanced sigma(YS) values would allow multistranded SS archwires to compete better against conventional NiTi products.     

Friction of conventional and silica-insert ceramic brackets in various bracket-wire combinations

OBJECTIVE: To compare the level of friction resistance (FR) of conventional and silica-insert ceramic brackets using various bracket-wire combinations and angulations. MATERIALS AND METHODS: Four types of ceramic brackets were examined: (1) polycrystalline alumina bracket (PCA-C), (2) polycrystalline alumina bracket with a stainless steel (SS) slot (PCA-M), (3) polycrystalline alumina bracket with a silica layer (PCA-S), and (4) monocrystalline sapphire bracket (MCS). A conventional SS bracket was used as the control. The static and kinetic FR in four bracket-wire angulations (0 degrees, 5 degrees, 10 degrees, and 15 degrees) was examined using SS and beta-titanium (beta-Ti) orthodontic wires, 0.019 x 0.025 inches in size, under elastic ligature in the dry state. RESULTS: The FR generated by the PCA-S bracket was significantly lower than that generated with the other ceramic brackets, and was similar to that of the SS bracket. The PCA-S bracket showed the lowest FR with both the SS and the beta-Ti wires at zero bracket angulation. The FR to sliding increased rapidly and nonlinearly when the bracket wire angulation was >5 degrees. The PCS-S bracket showed the lowest FR from 5 degrees to 15 degrees of angulation. The MCS bracket demonstrated the highest increase in FR from 0 degrees to 15 degrees of angulation, showing the highest FR at 15 degrees of angulation. CONCLUSION: PCA-S showed minimal FR among the ceramic brackets, and was comparable to the conventional SS bracket. The silica layer and rounded edges of the ceramic slot lowered FR considerably.     

A 12 month clinical study of bond failures of recycled versus new stainless steel orthodontic brackets

The purpose of this prospective longitudinal randomized study was to compare the clinical performance of recycled brackets with that of new stainless steel brackets (Orthos). Twenty patients treated with fixed appliances were included in the investigation. Using a 'split-mouth' design, the dentition of each patient was divided into four quadrants. In 11 randomly selected patients, the maxillary left and mandibular right quadrants were bonded with recycled brackets, and the remaining quadrants with new stainless steel brackets. In the other nine patients the quadrants were inverted. Three hundred and ten stainless steel brackets were examined: 156 were recycled and the remaining 154 were new. All the brackets were bonded with a self-cured resin-modified glass ionomer (GC Fuji Ortho). The number, cause, and date of bracket failures were recorded over 12 months. Statistical analysis was performed by means of a paired t-test, Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences were found between: (a) the total bond failure rate of recycled and new stainless steel brackets; (b) the upper and lower arches; (c) the anterior and posterior segments. These findings demonstrate that recycling metallic orthodontic brackets can be of benefit to the profession, both economically and ecologically, as long as the orthodontist is aware of the various aspects of the recycling methods, and that patients are informed about the type of bracket that will be used for their treatment.     

Comparison of frictional resistance in titanium and stainless steel brackets.

This study measures and compares the level of frictional resistance generated between titanium and stainless steel brackets. Both 0.018 and 0.022 inch slot size edgewise brackets were tested with different sized rectangular stainless steel wires in a specially designed apparatus. The frictional resistance was measured on Instron Universal testing machine (Instron Corp, Canton, Mass) with a 10 pound load cell. The specimen population was composed of 180 brackets and 180 wire specimens. A completely randomized design (one way) ANOVA was used to test for significant differences among the three bracket/wire types in the 0.018 and 0.022 inch slot sizes. This was followed by the Student Newman Keuls Multiple Comparison of means ranking at P < .05 to determine differences between the different groups. The titanium brackets showed lower static and kinetic frictional force as the wire size increased, whereas stainless steel brackets showed higher static and kinetic frictional force as the wire size increased.     

Bonding of stainless steel brackets to enamel with a new self-etching primer.

The purpose of this study was to measure the shear bond strength of stainless steel brackets bonded to enamel in vitro with a recently developed self-etching primer (Transbond Plus Self Etching Primer, 3M Unitek, Monrovia, Calif). Forty-eight extracted human teeth were obtained and randomly divided into 4 groups of 12: (1) control group with a conventional etchant and separate primer, (2) experimental group with the self-etching primer, left for 15 seconds before bonding, (3) same as group 2, but with the primer left for 2 minutes before bonding, (4) same as group 2, but with the primer left for 10 minutes before bonding. For each group, stainless steel brackets were mounted onto the prepared enamel, stored for 24 hours at 37 degrees C, and tested in a testing machine with a crosshead speed of 1 mm/min. There was no significant difference in the bond strength between the 4 groups as determined by analysis of variance (ANOVA) (P <.05). Under the conditions of these experiments, a 10-minute delay in bonding after application of the self-etching primer might not be deleterious to adhesion.     

Shear bond strength of stainless steel orthodontic brackets with a moisture-insensitive primer.

The purposes of this study were (1) to evaluate the shear bond strength of stainless steel orthodontic brackets bonded to dry and wet (with water and saliva) etched enamel with the use of the moisture-insensitive primer (MIP; Transbond; 3M Unitek, Monrovia, Calif) and (2) to evaluate the effectiveness of MIP with chemically activated (Concise; 3M Dental Products, St Paul, Minn) and light-activated (Transbond XT; 3M Unitek) resin. One hundred forty-four freshly extracted bovine teeth were divided into 12 groups (n = 12 teeth), and brackets were bonded with either of the 2 resins in combination with the conventional primer or MIP in dry or wet enamel surface conditions. The test specimens were mounted in a screw-driven mechanical testing machine (model 4204; Instron Corp, Canton, Mass) and subjected to a crosshead speed of 0.5 mm/min. The data were analyzed by 2-way analysis of variance. MIP with Concise produced slightly higher bond strengths compared with the conventional primers under wet conditions (MIP vs conventional: saliva, P <.001; water, P =.004). However, MIP in combination with Transbond XT produced comparable bond strengths on both the dry and wet etched enamel (dry, 10.14 MPa; water, 9.69 MPa; saliva, 8.90 MPa). The results of this study suggest that MIP be used only with light-activated composite resins.     

Microleakage beneath ceramic and metal brackets photopolymerized with LED or conventional light curing units

OBJECTIVE: To test the null hypotheses that (1) the type of light curing unit used (quartz-tungsten-halogen [QTH] or light-emitting diode [LED]) would not affect the amount of microleakage observed beneath brackets, and (2) the bracket type used (ceramic or metal) would not influence the amount of microleakage observed beneath brackets. MATERIALS AND METHODS: 40 freshly-extracted human premolars were randomly assigned into 4 bonding groups (n = 10/group): group 1, metal bracket + LED-cured Transbond XT; group 2, ceramic bracket + LED-cured Transbond XT; group 3, metal bracket + QTH-cured Transbond XT; and group 4, ceramic bracket + QTH-cured Transbond XT. The teeth were kept in distilled water for 1 month, and thereafter subjected to 500 thermal cycles. Then, specimens were sealed with nail varnish, stained with 0.5% basic fuchsin for 24 hours, sectioned, and photographed under a stereomicroscope. Microleakage was scored with regard to the adhesive-tooth interface and the bracket-adhesive interface at both incisal and gingival margins. Statistical analysis was accomplished by Kruskal-Wallis and Mann-Whitney U-tests with Bonferroni correction. RESULTS: Microleakage was observed in all groups. When an LED curing unit was used for adhesive polymerization, ceramic brackets displayed significantly less microleakage than metal brackets in both tooth-adhesive and bracket-adhesive interfaces. When a QTH curing unit was used, ceramic brackets displayed significantly less microleakage than metal brackets in the bracket-adhesive interface in both gingival and incisal margins. CONCLUSIONS: Ceramic brackets cured with LED units were the best combination, demonstrating the lowest microleakage scores.     

Sliding resistance of polycarbonate self-ligating brackets and stainless steel esthetic archwires

ObjectivesTo compare the sliding resistance forces produced by polycarbonate self-ligating brackets with esthetic archwires.Materials and methodsSamples of Opal, Oyster and conventional Blonde brackets were tested each one with 30 segments of .018x.025-in wires. The archwires were slipped at 8 mm/min for 40 seconds with an universal testing machine. Two way ANOVA with Bonferroni correction were used.ResultsBlonde brackets presented the highest sliding resistance, followed in decreasing order by Oyster and Opal. The TP Shiny Bright Wire produced the highest surface friction, while the lowest was observed for Imagination archwires (except for Opal brackets where the TP Pearltone Wire achieved the best performance).ConclusionsSelf-ligating system is more effective to reduce the sliding force resistance than conventional brackets. Esthetic stainless steel archwires produce less friction resistance than those without surface treatment. Polycarbonate self-ligating brackets are more effective to reduce the frictional forces than esthetic archwires with surface treatment.