Polycarbonate Brackets Research Articles

Analyse des biomechanischen Verhaltens von kieferorthopädischen Brackets mit unterschiedlichen Verschlussmechanismen / Biomechanical analysis of orthodontic brackets with different closing mechanisms

The aim of the present study was to investigate the biomechanical characteristics of orthodontic bracket systems made of metal, ceramics or plastics. Six different types of brackets were studied, including the Hanson Speed- and Damon 2-Brackets, both of which are equipped with specialised closing mechanisms. In addition, two conventional metal brackets (Ultratrimm), Discovery, the ceramics bracket Fascination 2 and the polycarbonate bracket Brillant were investigated. Stainless steel wires with the dimensions 0.40 mmx0.56 mm, 0.46 mmx0.56 mm, 0.46 mmx0.64 mm and 0.48 mmx0.64 mm were used with each bracket type simulating the clinical rotational movement of an upper central incisor in a biomechanical set-up. A buccal crown torque of 20 degrees was applied and the correction of the malposition was simulated experimentally. Each bracket/wire combination was analysed five times. The following parameters were analysed: maximum torquing moment, torque angle correction, and moment/torque ratio. Combining a 0.48 mmx0.64 mm steel wire with the ceramics brackets (Fascination 2) delivered the highest torquing moment (35 Nmm). The best torque correction was achieved with plastic brackets (17 degrees ). The lowest moments were approximately 5.2 Nmm (Damon) 2, 0.40 mmx0.56 mm steel wire), being in the range of the recommended minimum torquing moment (5 Nmm). Discovery brackets delivered similar low moments. Overall, only minor differences exist between the various bracket systems with regard to their efficiency in torque correction. Clinically, the wire/slot play seems to be more important than differences in the bracket designs.

Evaluation of esthetic brackets' resistance to torsional forces from the archwire

The aim of this study was to evaluate the resistance to deformation or fracture of esthetic brackets produced by archwire torsion. Six types of maxillary right central incisor brackets were analyzed: traditional ceramic brackets (cer); ceramic brackets reinforced with a stainless steel slot (cer/ss); ceramic brackets reinforced with a gold slot (cer/gold); traditional polycarbonate brackets (poly); polycarbonate brackets reinforced with a stainless steel slot (poly/ss); and polycarbonate brackets reinforced with ceramic fillers and a stainless steel slot (poly/cer/ss). Stainless steel wire segments were used, and the testing instrument (Emic DL 10000, São José do Rio Preto, PR, Brazil) was moved at a rate of 1 inch per minute to generate the wire torsion. The brackets showed deformation or fracture resistance values (gf x mm) in decreasing order as follows: cer/ss (3528.1 +/- 516.6), cer/gold (2858.7 +/- 611.6), cer (2424.0 +/- 352.1), poly/cer/ss (2279.5 +/- 174.5), poly/ss (2142.0 +/- 275.7), and poly (1463.6 +/- 193.3). The cer/ss ceramic brackets showed the greatest statistically significant (P <0.01) values of resistance to fracture, and the poly brackets had the lowest statistically significant (P <0.01) values of resistance to deformation. The cer brackets showed no significant differences (P >0.01) from the cer/gold, the poly/cer/ss, and the poly/ss brackets. This suggested that the stainless steel slot might enhance resistance to deformation or fracture, although gold slots and ceramic fillers are ineffective for reinforcing esthetic brackets.

Comparative Ex-Vivo Evaluation of the Frictional and Debonding Characteristics of Composite (Metal Inserted Plastic) Brackets.

The quest for increased esthetic demands in clinical orthodontic practice has lead to the development of tooth colored attachments like ceramic and polycarbonate bracket systems. First generation brackets of both these systems suffered a lot of shortcomings, which were rectified in successive generations. One such advancement is development of composite brackets and the present study is aimed at to compare 0.56 X 0.71 mm (0.022 X 0.028 inches) slot size, composite brackets - Classic‘ (Gold inserted), Elation‘ (Stainless steel inserted) and Spirit MB‘ (Stainless steel inserted) for the following parameters � (1) Frictional characteristics using 0.43 X 0.64 mm (0.017 x 0.025 inches) Stainless steel & Nitanium TM arch wires; (2) Tensile shear bond strength using Rely-a-bond! as bonding adhesive and (3) Surface characteristics. Conventional stainless steel bracketsGemini! was used as a control group. An instron universal testing machine was used to evaluate frictional characteristics and tensile shear bond strength. Stereo photomicroscope was used, to evaluate the extension and relation of the metal inserts to their respective slots, from the proximal and facial aspects of the brackets. Scanning electron microscope was used, for the surface characteristics evaluation of bracket slots before and after sliding the wires through slot. The results clearly indicated

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.

Evaluation of failure characteristics and bond strength after ceramic and polycarbonate bracket debonding: effect of bracket base silanization

The objectives of this study were to evaluate the effect of silanization on the failure type and shear-peel bond strength (SBS) of ceramic and polycarbonate brackets, and to determine the type of failure when debonded with either a universal testing machine or orthodontic pliers. Silanized and non-silanized ceramic and polycarbonate brackets (N = 48, n = 24 per bracket type) were bonded to extracted caries-free human maxillary central incisors using an alignment apparatus under a weight of 750 g. All bonded specimens were thermocycled 1000 times (5-55 degrees C). Half of the specimens from each group were debonded with a universal testing machine (1 mm/minute) to determine the SBS and the other half by an operator using orthodontic debonding pliers. Failure types of the enamel surface and the bracket base were identified both from visual inspection and digital photographs using the adhesive remnant index (ARI) and base remnant index (BRI). As-received ceramic brackets showed significantly higher bond strength values (11.5 +/- 4.1 MPa) than polycarbonate brackets [6.3 +/- 2.7 MPa; (P = 0.0077; analysis of variance (ANOVA)]. Interaction between bracket types and silanization was not significant (P = 0.4408). Silanization did not significantly improve the mean SBS results either for the ceramic or polycarbonate brackets (12.9 +/- 3.7 and 6.3 +/- 2.7 MPa, respectively; P = 0.4044; two-way ANOVA, Tukey-Kramer adjustment). There was a significant difference between groups in ARI scores for ceramic (P = 0.0991) but not polycarbonate (P = 0.3916; Kruskall-Wallis) brackets. BRI values did not vary significantly for ceramic (P = 0.1476) or polycarbonate (P = 0.0227) brackets. Failure type was not significantly different when brackets were debonded with a universal testing machine or with orthodontic debonding pliers. No enamel damage was observed in any of the groups.

Shear bond strength of orthodontic brackets to enamel under different surface treatment conditions

The purpose of the present study was to evaluate the shear bond strength to enamel and the adhesive remnant index (ARI) of both metallic and polycarbonate brackets bonded under different conditions. Ninety bovine permanent mandibular incisors were embedded in acrylic resin using PVC rings as molds and assigned to 6 groups (n=15). In Groups 1 (control) and 3, metallic and polycarbonate orthodontic brackets were, respectively, bonded to the enamel surfaces using Transbond XT composite according to the manufacturer's recommendations. In Groups 2 and 4, both types of brackets were bonded to enamel with Transbond XT composite, but XT primer was replaced by the OrthoPrimer agent. In Groups 5 and 6, the polycarbonate bracket bases were sandblasted with 50-μm aluminum-oxide particle stream and bonded to the enamel surfaces prepared under the same conditions described in Groups 3 and 4, respectively. After bonding, the specimens were stored in distilled water at 37°C for 24 hours and then submitted to shear bond strength test at a crosshead speed of 0.5 mm/min. The results (MPa) showed no statistically significant difference between Groups 4 and 6 (p>0.05). Likewise, no statistically significant differences (p>0.05) were found among Groups 1, 2, and 5, although their results were significantly lower than those of Groups 4 and 6 (p<0.05). Group 3 had statistically significant lower bond strength than Groups 2, 4, and 6, but no statistically significant differences were found on comparison to Groups 1 and 5. A larger number of fractures at the bracket/composite interface were evidenced by the ARI scores. OrthoPrimer bonding agent yielded higher bond strength in the groups using either conventional or sandblasted polycarbonate brackets, which was not observed in the groups using metallic brackets.

Torque capacity of metal and polycarbonate brackets with and without a metal slot.

The aim of the present study was to investigate slot deformation and the equivalent torque capacity of polycarbonate brackets with and without a metal slot in comparison with those of a metal bracket. For this purpose, the expansion characteristics and, in a further investigation, the labial crown torque of an upper central incisor, were measured in a simulated intra-oral clinical situation, using the orthodontic measuring and simulation system (OMSS). Three types of bracket with a 0.018 inch slot were tested: polycarbonate Brillant without a metal slot, Elegance with a metal slot and the metal bracket, Mini-Mono. For testing purposes the brackets were torqued with 0.016 x 0.022 inch (0.41 x 0.56 mm) and 0.018 x 0.022 inch (0.46 x 0.56 mm) ideal stainless steel archwires. In the activating experiments, significantly higher torque losses and lower torquing moments were registered with both rectangular archwires with the polycarbonate brackets than with the metal bracket. In the simulation tests, significantly higher torquing moments were registered with the metal bracket than with the polycarbonate brackets. The values for the Elegance bracket were between those of the Mini-Mono and Brillant brackets. The OMSS model approximates the clinical situation, with the torque loss being notably higher than in the in vitro activating experiments. This is due to the adjacent teeth giving the archwire additional play. In addition, the torquing process may twist the archwire, resulting in subsidiary forces. On the basis of the present results, all three brackets can be recommended for torquing. However, in view of the high torque losses, the torques programmed in the straightwire technique must be seen as questionable. Data should be provided by the manufacturer on the bending to be expected in polycarbonate brackets, which has to be offset by additional torque, or the bracket torque should be omitted from the technical specifications.

Bonding polycarbonate brackets to ceramic: Effects of substrate treatment on bond strength

This study evaluated the effects of 5 different surface conditioning methods on the bond strength of polycarbonate brackets bonded to ceramic surfaces with resin based cement. Six disc-shaped ceramic specimens (feldspathic porcelain) with glazed surfaces were used for each group. The specimens were randomly assigned to 1 of the following treatment conditions of the ceramic surface: (1) orthophosphoric acid + primer + bonding agent, (2) hydrofluoric acid gel + primer + bonding agent, (3) tribochemical silica coating (silicon dioxide, 30μm) + silane, (4) airborne particle abrasion (aluminum trioxide, 30μm) + silane, and (5) airborne particle abrasion (aluminum trioxide, 30μm) + silane + bonding agent. Brackets were bonded to the conditioned ceramic specimens with a light-polymerized resin composite. All specimens were stored in water for 1 week at 37°C and then thermocycled (1000 cycles, 5°C to 55°C, 30 seconds). The shear bond strength values were measured on a universal testing machine at a crosshead speed of 1 mm/min. Brackets treated with silica coating with silanization had significantly greater bond strength values (13.6 MPa, P = .01) than brackets treated with orthophosphoric acid (8.5 MPa). There was no significant difference ( P = .97) between the bond strengths obtained after airborne abrasion with aluminium trioxide particles followed by silanization (12 MPa) and hydrofluoric acid application (11.2 MPa) (ANOVA and Tukey test). Although brackets conditioned with orthophosphoric acid exhibited only adhesive failures of the luting cement from the ceramic surface, other conditioning methods showed mixed types of failures. Airborne particle abrasion with aluminium trioxide or silica coating followed by silanization gave the most favorable bond strengths. The types of failures observed after debonding indicated that the critical parameter was the strength of the adhesive joint of the luting cement to both the bracket and the ceramic.

Bonding polycarbonate brackets to ceramic

Bonding polycarbonate brackets to ceramic

Bayer’s Aura technology enables processors to colour already-moulded plastics

The aim of the study was to evaluate the biological effects of water eluents from polycarbonate based esthetic orthodontic brackets.The composite polycarbonate brackets tested were Silkon Plus (SL, fiber-glass-reinforced), Elan ME (EL, ceramic particle-reinforced) and Elegance (EG, fiber-glass-reinforced). An unfilled polyoxymethylene bracket (Brilliant, BR) was used as control. The brackets’ composition was analyzed by ATR-FTIR spectrometry. The cytotoxicity and estrogenicity of the eluents obtained after 3 months storage of the brackets in water (37 °C) were investigated in murine fibroblasts (NIH 3T3), breast (MCF-7) and cervical cancer (CCl-2/Hela) cell lines.SL and EG were based on aromatic-polycarbonate matrix, whereas EL consisted of an aromatic polycarbonate-polyethylene terepthalate copolymer. A significant induction of cell death and a concurrent decrease in cell proliferation was noted in the EG eluent-treated cells. Moreover, EG eluent significantly reduced the levels of the estrogen signaling associated gene pS2, specifically in MCF7 cells, suggesting that cell death induced by this material is associated with downregulation of estrogen signaling pathways. Even though oxidative stress mechanisms were equally activated by all eluents, the EG eluents induced expression of apoptosis inducing factor (AIF) and reduced Bcl-xL protein levels.Some polycarbonate-based composite brackets when exposed to water release substances than activate mitochondrial apoptosis.

Torsional creep of polycarbonate orthodontic brackets

Objective. Polycarbonate materials are known to exhibit creep. The purpose of this study was to investigate torsional creep of polycarbonate orthodontic brackets. Methods. Four polycarbonate, one metal, and one ceramic brackets were tested. An in vitro torque apparatus was constructed which applied 2000 g-mm of torque to the bracket slot via a cantilever beam perpendicular to the bracket face. The apparatus was placed in a 37°C water bath. Measurements of the angle of the cantilever beam were made at various times from 1 to 28 d. The initial angular change on loading and subsequent changes with time were compared with ANOVA and Tukey tests at p < 0.5. Results. All but one bracket showed the majority of creep by 2 d. Creep was not judged to be clinically significant for the metal, ceramic and the metal slot-reinforced brackets. The polycarbonate bracket without metal slots demonstrated significantly more creep (p < 0.05) than the polycarbonate reinforced with a metal slot, metal and ceramic brackets. Significance. Clinically significant bracket slot angle (torque) change due to creep can occur when using polycarbonate brackets without metal slot reinforcement.

Shear bond strength of a new polycarbonate bracket—an in vitro study with 14 adhesives

Shear bond strength of a new polycarbonate bracket—an in vitro study with 14 adhesives

Retention capacity of the bracket bases of new esthetic orthodontic brackets

Tensile bond strength and bond failure locations were evaluated in vitro for three types of direct bonding cements (self-cured diacrylate, dual-cured diacrylate, and dual-cured glass ionomer) with four types of brackets (stainless steel, polycarbonate, ceramic, and ceramic-polycarbonate) by using a plastic cylinder as the substrate. A highly filled, self-cured diacrylate cement gave the highest bond strength values with the polycarbonate, stainless steel, and ceramic-polycarbonate brackets. A dual-cured diacrylate cement gave the highest bond strength with a mechanically retained ceramic bracket. The dual-cured glass ionomer cement gave the highest bond strength values with a silanated ceramic bracket. All bond failures occurred at the bracket/cement interface with the stainless steel bracket, whereas failure locations were at the bracket/cement interface and within the cement with the polycarbonate bracket. Bond failures occurred between bracket and cement, within the cement, and within the bracket with the ceramic brackets. (A M J O RTHOD D ENTOFAC O RTHOP 1995;107:596-603.)

In vitro torque-deformation characteristics of orthodontic polycarbonate brackets

The purpose of this study was to investigate the torque-deformation characteristics of the following four types of polycarbonate brackets: (1) pure polycarbonate, PPC (anterior Miura, RMO, Denver, Colo.), (2) ceramic reinforced polycarbonate, CRPC (Silkon bracket, American, Sheboygan, Wis.), (3) metal slot reinforced polycarbonate, MRPC (Plastic bracket, Tella Tech, Miami, Fla.), and (4) metal slot and ceramic reinforced polycarbonate, MCRPC (Spirit, Ormco, Glendora, Calif.). A stainless steel bracket, (Mini Diamond, Ormco, Glendora, Calif.), was used as a control. Ten brackets of each type were tested. Each bracket was bonded to a porcelain tooth and engaged in a torquemeter. The tooth-bracket assembly was made stationary by embedding it in die stone. Torsion was applied to the bracket at 4 degrees per minute and the resultant torque (grams.centimeters) and deformation (degree) were measured. For optimum labiolingual tooth movement for a maxillary incisor at 175 grams . centimeters, the amount of angular deflection necessary for the different polycarbonate brackets was the following: (a) 15 degrees for MRPC, (b) 17 degrees for MRPC, (c) 24 degrees for CRPC, and (d) > 30 degrees for PPC. The amount of deformation at this deflection was the least for MRCP followed by MCRPC, CRCP, and PPC. When compared with the stainless steel bracket, all polycarbonate brackets showed significantly (p < 0.0001) higher deformation and lower torque. Within the polycarbonate group, there was a significant difference (p < 0.0001) between each bracket for both measurements. The MRPC produced the highest torque and lowest deformation values followed by the MCRPC, CRCP, and PPC. It appears that only the metal slot reinforced brackets are clinically capable of torquing teeth sufficiently.

The dynamnic frictional resistance between orthodontic brackets and arch wires

Limited published research on friction deals mainly with conventional stainless steel brackets and arch wires. However, the clinician can choose from a range of modern materials in determining arch wire and bracket combinations. This study quantifies the dynamic frictional force of sliding between different modern orthodontic brackets and arch wires. From the multitude of factors involved in the frictional process, the following were selected for investigation: arch wire material, bracket material, bracket-to-arch wire angulation, and lubrication (artificial saliva). The frictional force involved in sliding a ligated arch wire through a bracket slot was measured with a universal materials testing machine. A four-way analysis of variance was used to assess the results. Of the four factors investigated, all were found to have a significant influence on friction. Polycarbonate brackets showed the highest friction and stainless steel brackets the lowest. Friction increased with bracket-to-arch wire angulation. Lubrication significantly reduced friction. A range of 0.9 to 6.8 N frictional force was recorded. The actual force values recorded were most useful for comparing the relative influence of the factors tested on friction, rather than as a quantitative assessment of friction in vivo. The forces observed suggest that friction may be a significant influence on the amount of applied force required to move a tooth in the mouth. Hence, arch wire and bracket selection may be an important consideration when posterior anchorage is critical. (A M J O RTHOD D ENTOFAC O RTHOP 1994;106:131-8.)

Direct bonding of polycarbonate orthodontic brackets: An in vitro study

One hundred four polycarbonate brackets were bonded to extracted premolars with four direct bonding resins, coded N, D, G, and O. The procedures necessary for direct bonding of plastic brackets clinically were duplicated in vitro. The adhesion of a minimum of ten bracket/enamel interfaces per material was tested in shear after both 7 and 30 days' storage in artificial saliva at 37 °C. Preliminary characterization of the bond failures was performed at low-power magnification, but final characteristics of the fractured bonds were analyzed under the scanning electron microscope. Statistical analysis of the shear strength data was carried out with the exclusion of the failures attributable to defective brackets. The results were as follows: After 7 days' storage in Ringer's solution, D and G resins showed a significantly greater shear bond strength than the N system, while system O occupied an intermediate position. D, O, and N showed a significant decrease in mean shear bond strength from 7 to 30 days, while G maintained its initial good strength through that period. In addition, it was found that EDX analysis showed only one of the four materials tested (N system) had a ceramic filler. SEM analysis revealed that most bonds which appeared to be of an adhesive nature when viewed under low magnification actually turned out to have a cohesive component when viewed under higher magnification.

Effect of temperature and humidity on the adhesive strength of orthodontic direct bonding materials.

The effects of temperature and humidity on the adhesive strength of two direct bonding orthodontic materials were investigated. Tensile testing showed that the adhesive bond was much stronger than the polycarbonate brackets. There is a significant increase in tensile and shearlike strength after 15-, 22-, and 30-day incubation at 37 C and 100% humidity, as compared with initial strength (after 30 minutes) at room temperature.