Monocrystalline Ceramic Brackets Research Articles

Correlating Frictional Forces Generated by Different Bracket Types during Sliding and Surface Topography Using Scanning Electron Microscopy and Optical Profilometer.

The study aims to correlate the frictional forces (FF) of four different types of commercially available ceramic brackets to their surface topography. Two monocrystalline (MC) brackets (CLEAR™, Adanta, Germany; Inspire ICE™, Ormco, USA), one polycrystalline (PC) bracket (Symetri Clear™, Ormco, USA), one clear hybrid esthetic bracket (DISCREET™, Adanta, Germany), and a stainless-steel (SS) bracket (Victory™, 3M Unitek, USA) served as control. Both static friction (SF) and kinetic friction (KF) were recorded during sliding using an Instron universal machine in dry settings. The bracket slot surface topography was evaluated. A scanning electron microscope (SEM) and a profilometer machine were used for assessment before and after sliding. Frictional forces values during sliding were as follows in descending order; Inspire ICE™, CLEAR™, DISCREET™, Symetri Clear™, and, lastly, Victory™. Also, DISCREET™ scored the highest in surface roughness (Sa) values followed by Symetri Clear™. None of the correlations were statistically significant. Frictional forces produced during sliding were not always directly related to surface roughness. Monocrystalline ceramic brackets appeared to have the greatest FF and a low surface roughness. Furthermore, DISCREET™ scored a very low frictional value comparable to metal brackets yet showed the highest surface roughness. Metal brackets exhibited the greatest surface smoothness before sliding and the least SF. Predicting the FFs produced during sliding mechanics would help the practitioner while choosing the bracket system to be used, and while planning the treatment mechanics, how much force to deliver, and how much tooth movement to expect. How to cite this article: AlBadr AH, Talic NF. Correlating Frictional Forces Generated by Different Bracket Types during Sliding and Surface Topography Using Scanning Electron Microscopy and Optical Profilometer. J Contemp Dent Pract 2024;25(1):41-51.

Comparison of Friction Produced at Backet-Wire Interface in Monocrystalline Ceramic Brackets of 8 Different Brands: An In Vitro Study

ABSTRACT Introduction: The esthetic during the various orthodontic treatments has led to the invention of the brackets. When different ceramic brackets and archwires are used, the different frictional forces may result in the different outputs. Hence, in the present study, we evaluated and compared the frictional resistance between eight standard monocrystalline ceramic bracket models and each of the archwires of four different alloys. Materials and Methods: Frictional force was tested using Instron testing machine, in vitro, for eight types of monocrystalline ceramic bracket, and four types of archwires beta-titanium, NiTi, copper-nickel-titanium, and stainless steel statistical analysis were done using various tools, and significance value of <0.05 was considered. Results: Ormco and AO (Radiance) monocrystalline ceramic brackets created lesser frictional resistance than other monocrystalline ceramic brackets. Stainless steel archwire generates lesser static friction. Beta-titanium archwire created higher static friction. A 0.017 × 0.025 inch stainless steel archwire generates lesser static friction to 0.019 × 0.025 inch TMA. Conclusion: It can be concluded that Ormco and AO (Radiance) monocrystalline ceramic brackets, with stainless steel archwires and of size 0.017 × 0.025 inch, can generate better forces when used for the orthodontic tooth movements.

Static friction, surface roughness, and antibacterial activity of orthodontic brackets coated with silver and silver chitosan nanoparticles

To determine the effect of silver and silver chitosan nanocoatings on monocrystalline ceramic, polycrystalline ceramic, and metallic brackets regarding friction, roughness, and antibacterial effect against Streptococcus mutans. A total of 99 upper right premolar brackets with a 0.022 × 0.025 -inch slot were divided into three groups, each 33 according to coating material; the non-coated group, silver nanoparticles (AgNPs), and silver chitosan nanoparticles (Ag-CsNPs) groups. Each group was equally subdivided into the following three subgroups regarding bracket materials: monocrystalline ceramic, polycrystalline ceramic, and metallic brackets. A universal testing machine determined static friction on a custom-made acrylic jig. Then a profilometer machine was used to collect roughness data, and finally, the anti-cariogenic effect was measured with the disc diffusion technique's "minimum zone of inhibition" against Streptococcus mutans. Two-way ANOVA was used to compare data between groups and subgroups, followed by the Bonferroni test for multiple pair-wise comparisons. The nanocoating effect on ceramic brackets' static friction was non-significant. The AgNPs and Ag-CsNPs coated metallic group revealed a significant increase in static friction-a significant effect of the nanocoating in the surface roughness of monocrystalline and polycrystalline ceramic brackets. A significant favorable effect of AgNPs and Ag-CsNPs against Streptococcus mutans was observed. AgNPs and Ag-CsNPs coats are unsuitable for decreasing friction in metallic brackets or improving roughness in polycrystalline ceramic brackets. Nano coating can improve roughness in monocrystalline ceramic brackets. Coating brackets with AgNPs and Ag-CsNPs has a tremendous antibacterial effect on Streptococcus mutans, a substantial factor in the incidence of dental caries.

Laser Er:YAG-Assisted Debonding May Be a Viable Alternative to the Conventional Method for Monocrystalline Ceramic Brackets.

In orthodontic practice, due to the increased interest among patients in smile aesthetics, different types of brackets are now being used, with those most frequently applied being ones made of polycrystalline and monocrystalline ceramic. The aim of this study was to evaluate the laser Er:YAG-assisted debonding technique compared to conventional methods for removing monocrystalline ceramic brackets from human teeth. The study sample included 60 vital teeth (frontals of the upper jaw) from 10 patients who had monocrystalline ceramic brackets and were in the final phase of orthodontic treatment. The debonding procedure was carried out following a split-mouth study design, using either the conventional technique or laser Er:YAG 2940 nm radiation. For each tooth, three variables were evaluated: the patient's sujective tooth sensitivity associated with the debonding, the time required for debonding, and pulp blood flow microdynamics after the debonding. Three evaluation instruments were used to assess and quantify the treatment effects: (i) the Wong-Baker FACES Pain Rating Scale for pain assessment; (ii) a digital stopwatch/timer to measure the time required to remove the bracket; and (iii) laser Doppler flowmetry (LDF) for recording the pulp blood flow evolution. The statistical analysis of the recorded data showed a statistically significant difference between the two debonding methods regarding the tooth sensitivity during the debonding and the time required for the procedure. The subjective tooth sensitivity was reduced from a mean ± standard deviation of 3.07 ± 1.46 to 0.47 ± 0.86 on the Wong-Baker FACES scale (Wilcoxon signed rank, p < 0.001). The necessary time for debonding was reduced by 0.697 ± 0.703 s per tooth (paired t-test, p < 0.001). There was no difference in the blood microdynamics between the two debonding techniques. According to the results of this study, the laser Er:YAG-assisted debonding technique may be a viable alternative to the conventional method for monocrystalline ceramic brackets.

Comparitive evaluation of antimicrobial effectiveness of titanium oxide coatings on different types of ceramic brackets against Streptococcus mutans

Nanomaterials are widely used in modern clinical dentistry. They improve various properties, such as antimicrobial properties, durability of materials. These particles do not exceed 100 nm, due to they obtain a better ratio between the surface and mass. Nanomaterials are used in many areas of dentistry, such as conservative dentistry, endodontics, oral, and maxillofacial surgery, periodontics, orthodontics, and prosthetics. One of the most important complications of fixed orthodontic treatment is enamel demineralization. Brackets and orthodontic accessories facilitate plaque accumulation and compromise oral hygiene maintenance which lead to an increase in oral bacteria count during orthodontic treatment. 30 MBT 0.022’’ monocrystalline ceramic brackets and 30 MBT 0.022’’ polycrystalline ceramic brackets (Metro Orthodontics) which are randomly divided into 4 groups: 2 control groups (group-1=15 uncoated monocrystalline and group-2=15 uncoated polycrystalline) and 2 experimental groups (group-3=15 silver oxide coated monocrystalline and group-4=15 silver oxide coated polycrystalline). S.mutans counts were significantly less in the experimental groups than control groups. Titanium oxide coatings on ceramic brackets reduced the colony forming units of S. mutans. Reduced number of colony forming units was seen in both the monocrystalline and polycrystalline coated brackets than their control groups.

Comparitive evaluation of antimicrobial effectiveness of silver oxide coatings on different types of ceramic brackets against Streptococcus mutans

The historical aspect of nanotechnology dates back to 600 BC. Taniguchi was the first to use the term nanotechnology in 1974, originating from a Greek word meaning “dwarf”. Nanotechnology when combined with dentistry and medicine created an interdisciplinary field i.e., nanodentistry and nanomedicine and this combination gets engineers, chemists, physicians on a single platform having various applications in detection, imaging and drug delivery devices.With respect to orthodontics, the nanoparticle coated archwires, adhesives, temporary anchorage devices, brackets, orthodontic wires with shape memory and biofilm control features have been applied. Silver nanoparticles are combined with different accessory orthodontic materials which results in the addition of more antimicrobial properties which inturn decreases the biofilm formation and maintain better oral health. Antibacterial effectiveness of nanosilver coated materials has been shown with and without the release of nanosilver ions in in vitro studies. In addition, long-term inhibitory effects against S.mutans have been found while no nanosilver ions were released. 30 MBT 0.022’’ monocrystalline ceramic brackets and 30 MBT 0.022’’ polycrystalline ceramic brackets (Metro Orthodontics) which are randomly divided into 4 groups: 2 control groups (group-1=15 uncoated monocrystalline and group-2=15 uncoated polycrystalline) and 2 experimental groups (group-3=15 silver oxide coated monocrystalline and group-4=15 silver oxide coated polycrystalline). S.mutans counts were significantly less in the experimental groups than control groups. Silver oxide coatings on ceramic brackets reduced the colony forming units of S. mutans. Both monocrystalline and polycrystalline coated brackets showed reduced number of colony forming units than their control groups.

Comparative Evaluation of Frictional Resistance Between Different Types of Ceramic Brackets and Stainless Steel Brackets With Teflon-Coated Stainless Steel and Stainless Steel Archwires: An In-Vitro Study.

BackgroundOrthodontic tooth movement relies on sliding mechanics usually achieved by sliding the archwire through brackets. Sliding causes friction which is a force resisting the relative motion of two contacting objects. Frictional resistance is undesirable in orthodontic tooth movement because the archwire might bind with the bracket and prevent tooth movement. In addition, friction causes bending of the archwire leading to unwanted tooth movement or space loss through anchorage interference, prolonging the treatment time and root resorption. This study was performed to compare the frictional resistance produced by different types of ceramic brackets and stainless steel brackets with Teflon-coated stainless steel and stainless steel archwires. The surface texture of the wire before and after friction test was also evaluated using a scanning electron microscope (SEM).MethodologyA total of 48 samples were tested. In total, 12 premolar brackets each of stainless steel (Ortho technology, Carlsbad, CA, USA), monocrystalline ceramic (Ortho technology, Carlsbad, CA, USA), polycrystalline ceramic (Ortho technology, Carlsbad, CA, USA), and ceramic bracket with a metal slot (Ortho technology, Carlsbad, CA, USA) having an 0.022-inch slot were coupled with 0.019 × 0.025-inch stainless steel and Teflon-coated stainless steel wires. Each bracket-wire assembly was vertically mounted and clamped to the jaws of the universal testing machine. The wire was pulled across the bracket with a cross head speed of 10 mm per minute. The readings obtained were recorded. To evaluate the surface roughness, wires were examined using an SEM (in four magnifications 250×, 500×, 1,000×, and 5,000×) before and after testing.ResultsUnder the testing conditions, the stainless steel bracket-stainless steel wire combination produced the least frictional resistance, and the polycrystalline ceramic bracket-stainless steel wire combination produced the highest frictional resistance. Ceramic brackets with a metal slot generated lesser friction than other types of ceramic brackets but more friction than stainless steel brackets. Moreover, for all bracket-archwire combinations, Teflon-coated wires generated reduced frictional resistance compared to stainless steel wires. The surface examination of Teflon-coated stainless steel wire and conventional uncoated stainless steel wire revealed that Teflon-coated wire had a smoother surface compared to uncoated stainless steel wire.ConclusionsWithin the limitations of this study, it was concluded that the stainless steel bracket produced the lowest frictional resistance and the polycrystalline ceramic bracket produced the highest frictional resistance. Ceramic brackets with a metal slot showed a coefficient of friction that was more than but comparable to that of stainless steel brackets. Monocrystalline ceramic brackets generated lesser friction compared to polycrystalline ceramic brackets. Further, Teflon coating of stainless steel archwires can reduce frictional resistance compared to conventional uncoated stainless steel archwires. The surface of Teflon-coated stainless steel wires was found to be smoother than uncoated stainless steel wires.

Cytotoxic effects of titanium alloy orthodontic mini-screw implants: Clinical prospective study

Objectives: to evaluate possible cytotoxic effects of titanium alloy (Ti alloy) orthodontic mini-screw implants on the surrounding oral mucosal cells. Materials and Methods: Thirty orthodontic mini-screw implants (MSIs) installed to serve as anchorage for maxillary canine retraction after maxillary first premolar extraction. Fifteen female orthodontic patients with mean age of 16.11 ± 1.68 years were consented to participate in the study, which ran for four months. The orthodontic appliance consisted of direct-bonded Roth monocrystalline ceramic brackets, and teflon-coated preformed archwires. Clinical evaluation of MSIs and oral hygiene condition were evaluated throughout the study period. Percentage of oral mucosa cells’ DNA fragmentation were analyzed before insertion of MSIs, after one week, one month, three months and four months of MSIs insertion with the Comet assay analysis. Results: ANOVA test showed statistically significant decrease in oral hygiene condition during the study period. Statistically insignificant difference was evident in DNA fragmentation index of the collected oral mucosal cell in different time intervals. Conclusions: Orthodontic titanium alloy MSIs were biocompatible and demonstrated no cytotoxic effects on oral mucosal cells.

Reasons influencing the preferences of prospective patients and orthodontists for different orthodontic appliances.

ObjectiveTo evaluate the reasons influencing the preferences for a certain type of orthodontic appliance over another among prospective patients (PP) and orthodontists.MethodsA total of 49 PP and 51 orthodontists were asked about their preferences for the following appliances clear aligners (CA), lingual metallic brackets (LMB), polycrystalline and monocrystalline ceramic brackets, and buccal metallic brackets (BMB). The participants rated the importance of 17 potential reasons that would explain their choices. The reasons that contributed most to these preferences were identified. Non-parametric tests (Fisher’s exact, χ2 and Mann–Whitney tests) and multivariate analyses (regression and discriminant analysis) were used to assess the data (α = 0.05).ResultsCA and BMB were the most chosen appliances by PP and orthodontists, respectively. LMB was the most rejected option among both groups of participants (p < 0.001). Rates of the importance of pain/discomfort, smile esthetics, finishing details, and feeding/speech impairment showed the highest differences between PP and orthodontists (p < 0.0005). Discriminant analyses showed that individuals who considered treatment time and smile esthetics as more important were more likely to prefer CA, while those who prioritized finishing details and cost were more likely to choose BMB (p < 0.05).ConclusionsReasons related to comfort and quality of life during use were considered as more important by PP, while those related to the results and clinical performance of the appliances were considered as more relevant by orthodontists.

Comparison of frictional resistance between four types of brackets in combination with stainless steel and beta-titanium archwires

Objectives: The objective of the study was to evaluate and compare the frictional resistance generated by four different types of brackets in combination with stainless steel (SS) and titanium molybdenum alloy (TMA) archwires. Materials and Methods: Maxillary premolar brackets were used in this study. These brackets were divided into eight groups comprising seven samples each. Of the eight groups, four groups were combined with SS and four groups were combined with TMA archwires. The testing was done in the presence of human saliva. The static frictional resistance was calculated for each group. One-way ANOVA and post hoc Tukey tests were done to compare the friction generated by each group. Results: There was a statistically significant difference between the friction generated by the monocrystalline brackets and the other bracket groups (P &lt; 0.001). There was no statistically significant difference in static friction generated between self-ligating and conventionally ligated brackets. There was a statistically significant difference between the frictional resistance produced by SS and TMA wires (P = 0.02) with regard to monocrystalline ceramic brackets only. Conclusion: Monocrystalline ceramic brackets (Radiance) were found to generate the highest frictional resistance during sliding mechanics when compared to other brackets in combination with both SS and TMA wires. Self-ligating brackets did not show a statistically significant reduction in friction when compared to conventional ligation. There was a statistically significant difference between SS and TMA wires when used with monocrystalline brackets.

Colour change of ceramic brackets with the use of coloured beverages in adolescent patients: A randomized clinical trial

To clinically evaluate colour change of ceramic orthodontic brackets with the use of coloured beverages as ceramic brackets' resistance to discoloration has become a major concern. A prospective two parallel groups-split mouth randomized trial with a 1:1 allocation ratio. Two equal groups including 40 adolescent patients from the orthodontic department (Faculty of Dentistry, Mansoura University, Egypt), scheduled for maxillary premolar extractions were bonded with 2 types of mono-crystalline ceramic brackets: Type 1 (Inspire ICETM) and Type 2 (Radiance PlusTM). Participants in each group were asked to rinse with either black tea or Cola. After extraction, the colour of the 80 debonded brackets was compared to that of 20 control brackets from each type by spectrophotometer according to the international standard CIELAB colour space (CIE L*a*b*). The latter consists of three coordinates: L* (lightness value), a* and b* (the colour channels). The total colour difference ΔE* is the distance between two colours in this three-dimensional colour space. The colour change was also assessed by digital image analysis according to the RGB model. Type 1 brackets showed mean ΔE* values of 2.24±0.25 in black tea and 1.76±0.1 in Cola groups (P<0.001), while Type 2 brackets showed means of 1.99±0.15 in black tea and 1.56±0.1 in Cola groups (P<0.001). The mean RGB values were 174.3±12.02 in black tea and 185.6±6.9 in the Cola groups of type 1 brackets (P<0.001), while were 166.5±17.8 in black tea and 190.8±8.9 in Cola groups of type 2 brackets (P<0.001). Black tea showed more significant effect than Cola on the two bracket types. Bracket type affected the colour change in each beverage group.

Attractiveness of different esthetic orthodontic wires.

ABSTRACTObjective: The aim of this study was to evaluate the attractiveness of different types of esthetic orthodontic wires by laypeople and dentists. Methods: Five different types of orthodontic wires were evaluated: three esthetic wires (Teflon-coated, epoxy resin-coated and rhodium-coated wires), and two metallic wires (stainless steel and NiTi), as control. Monocrystalline ceramic brackets were installed in the maxillary arch of a patient presenting good dental alignment. The five evaluated wires were attached to the orthodontic appliance with an esthetic silicone elastic and photographed. The photographs were evaluated by 163 individuals, 110 dentists and 53 laypeople. The data were statistically evaluated by two-way ANOVA and one-way ANOVA, followed by Tukey tests. Results: There was a statistically significant difference in the attractiveness among the wires evaluated; the most esthetic was the rhodium-coated wire, followed by the epoxy resin-coated wire and, finally, the Teflon-coated wire, with no significant difference from the stainless steel and NiTi control archwires. There was no significant difference between the groups of evaluators. Conclusion: The most attractive was the rhodium-coated wire, followed by the epoxy resin-coated wire and, finally, the least attractive wire was the Teflon-coated wire, without statistically significant difference to the stainless steel and NiTi wires, used as control.

In vitro Evaluation of Static Frictional Forces at the Bracket-archwire Interface

The aim of this research is to compare the static frictional forces generated by different bracket-archwire couples. The study group consisted of three types of ceramic brackets (polycrystalline alumina with stainless steel slot, polycrystalline alumina and monocrystalline alumina), one stainless steel bracket and two types of archwires (0.016` NiTi and 0.019x0.025` SS). Brackets corresponding to the upper right quadrant (form upper right central incisor to the upper right second premolar) were bonded on standardized maxillary models and elastomeric ligatures were used to secure the archwire to the bracket system. An in-vitro experiment was conducted using a testing machine designed to measure the compression and traction force, both in dry and wet testing conditions. The results indicated statistically significant differences between most bracket-archwire groups. According to the data obtained, stainless steel brackets produced the lowest static frictional forces, regardless of test conditions and orthodontic archwire type. Polycrystalline ceramic brackets with stainless steel slot generated higher static frictional forces than stainless steel brackets, but lower than ceramic brackets when combined with the 0.019`�0.025` SS archwire. No significant differences were found between polycrystalline and monocrystalline ceramic brackets. Experiments performed with 0.019�0.025` SS archwire produced greater static frictional forces than those with 0.016` NiTi wire. Static frictional forces were not significantly influenced by the test conditions.

Fracture strength of monocrystalline and polycrystalline ceramic brackets during archwire torque

Abstract Introduction In recent years, there has been an increasing demand for esthetic treatments, especially among orthodontic patients. Objective This study determined the fracture strength of monocrystalline and polycrystalline ceramic brackets of different manufacturers during archwire torque. Material and method Sixty ceramic brackets (Roth, right upper central incisors, 0.022 x 0.028-inch slot) were allocated into two groups (30 specimens per group) according to the type of ceramics: monocrystalline and polycrystalline. Subsequently, the groups were divided into three subgroups (n = 10) according to the manufacturer: Orthometric, Eurodonto and Ortho Technology. Sixty PVC cylinders were filled with chemically activated acrylic resin (CAAR), the brackets were fixed with CAAR onto the cylinder surface and the excess material was used to partially cover the base of the bracket. After 24h, the U-shaped wire base (0.019 x 0.025 inches; 6 mm height and width) was inserted into the bracket slot and fixed thereon with a stainless-steel wire. Vertical folds were made at the ends of the “U” to support the universal test machine chisel. The fracture strength test was performed at a speed of 1.0 mm/min until fracture into a universal test machine (Instron). The data were recorded, transformed into g.mm and submitted to two-way ANOVA followed by Tukey’s post-hoc test (SAS Institute Inc., Cary, NC, USA, version 9.3) (α=5%). Result Monocrystalline brackets showed a higher fracture strength than polycrystalline brackets, regardless of the manufacturer (p&lt;0.05). The highest fracture strength values were observed in Ortho Technology and Orthometric brackets, with no significant difference between them (p&gt;0.05). Conclusion Monocrystalline ceramic brackets have a higher fracture strength than polycrystalline brackets, with significant manufacturer-dependent differences.

Evaluating the Type of Light Transmittance in Mono Crystalline, Poly Crystalline and Sapphire Brackets- An Invitro Spectrofluorometer Study.

Most of the patients seek orthodontic treatment to improve the smile, which improves the facial profile by means of fixed appliances i.e., brackets and wires. The brackets are of different types like stainless steel and ceramic. Ceramic brackets were considered as aesthetic appliance which was divided into mono-crystalline, polycrystalline and sapphire brackets. The light transmittance might influence the degree of curing adhesive material in mono crystalline, polycrystalline and sapphire brackets. The aim of the present study was to evaluate the translucency and intensity of three different aesthetic brackets (mono crystalline, poly crystalline and sapphire ceramic brackets) and to determine their influence on shear bond strength of the brackets. The adhesive remnant index was also measured after debonding of the brackets from the tooth surface. Twenty six samples each of monocrystalline, polycrystalline and sapphire brackets (total 78 ceramic brackets) were used for the study. The bracket samples were subjected to optical fluorescence test using spectrofluorometer to measure the intensity of the brackets. Seventy eight extracted premolar teeth were procured and divided into 3 groups. The brackets were then bonded to the tooth using Transbond XT (3M Unitek) light cure composite material and cured with new light cure unit (Light Emitting Diode) of wood pecker company (400-450nm) for 30 seconds, and these samples were subjected to shear bond strength test with Instron Universal Testing Machine (UNITEK-94100) with a load range between 0 to 100 KN with a maximum cross head speed of 0.5mm/min. ARI (Adhesive Remnant Index) scores were evaluated according to Artun and Bergland scoring system using stereomicroscope at 20x magnification. The light absorption values obtained from spectrofluorometeric study were 3300000-3500000 cps for group 1 (monocrystalline ceramic brackets), 6000000-6500000 cps for Group 2 (polycrystalline ceramic brackets) and 2700000 -3000000 cps for Group 3 (sapphire ceramic brackets) i.e., Group 2 showed the highest light absorption and the least translucency followed by groups 1 and 3. Shear bond strength results were 2.4 mpa, 1.9 mpa and 3.6 mpa for groups 1,2 and 3 respectively. Superior shear bond strength was recorded in group 3 (sapphire ceramic brackets). ARI results showed that group 3 had increased bond between bracket adhesive interfaces when compared to the other 2 groups. From this study, it has been concluded that sapphire ceramic brackets (Group 3) was superior in translucency and shear bond strength followed by monocrystalline and polycrystalline ceramic brackets.

Frictional resistance of aesthetic brackets

The aim of this study was to evaluate and compare the static frictional forces produced by monocrystalline ceramic (sapphire) bracket and polycrystalline ceramic bracket. Materials and methods: one hindered twenty brackets/segment of archwire combinations were used, each bracket/segment of archwire combination was tested 10 times. The tests were performed in a universal testing Instron machine. The data was submitted to in depended t-test. Results: The independent sample t-tests showed a highly significant difference in the static frictional forces between monocrystalline ceramic (sapphire) bracket and polycrystalline ceramic bracket. Conclusion: According to the biomechanical result gained from the present study, the monocrystalline ceramic (sapphire) brackets produced lower static friction level than polycrystalline ceramic bracket.

In vitro study of color stability of polycrystalline and monocrystalline ceramic brackets

ObjectiveThe aim of this in vitro study was to analyze color stability of monocrystalline and polycrystalline ceramic brackets after immersion in dye solutions.MethodsSeven ceramic brackets of four commercial brands were tested: Two monocrystalline and two polycrystalline. The brackets were immersed in four dye solutions (coffee, red wine, Coke and black tea) and in artificial saliva for the following times: 24 hours, 7, 14 and 21 days, respectively. Color changes were measured by a spectrophotometer. Data were assessed by Multivariate Profile Analysis, Analysis of Variance (ANOVA) and Multiple Comparison Tests of means.ResultsThere was a perceptible change of color in all ceramic brackets immersed in coffee (ΔE* Allure = 7.61, Inspire Ice = 6.09, Radiance = 6.69, Transcend = 7.44), black tea (ΔE* Allure = 6.24, Inspire Ice = 5.21, Radiance = 6.51, Transcend = 6.14) and red wine (ΔE* Allure = 6.49, Inspire Ice = 4.76, Radiance = 5.19, Transcend = 5.64), but no change was noticed in Coke and artificial saliva (ΔE < 3.7).ConclusionCeramic brackets undergo color change when exposed to solutions of coffee, black tea and red wine. However, the same crystalline structure, either monocrystalline or polycrystalline, do not follow the same or a similar pattern in color change, varying according to the bracket fabrication, which shows a lack of standardization in the manufacturing process. Coffee dye produced the most marked color changes after 21 days of immersion for most ceramic brackets evaluated.

Surface roughness of three types of modern plastic bracket slot floors and frictional resistance

To quantitatively analyze the surface roughness of the slot floors of three types of modern plastic brackets and to measure static frictional force during sliding mechanics in vitro. Control groups comprised stainless steel brackets and monocrystalline ceramic brackets. Test groups comprised three types of 0.022-in slot, Roth prescription, plastic, maxillary right central incisor brackets. Test groups included glass fiber-reinforced polycarbonate, filler-reinforced polycarbonate, and hybrid polymer with inserted metal slot brackets. The static frictional resistance caused by sliding movements with an archwire (stainless steel) in vitro was quantitatively analyzed. Both scanning electron microscope and three-dimensional optical surface profiling were used. Scanning electron microscope and three-dimensional optical surface profiler revealed that all as-received brackets had irregular slot floor surfaces, and both irregularity and roughness increased after the archwire sliding test. The ceramic brackets in the control group showed significantly lower surface roughness values and higher frictional values during the archwire sliding test compared with the other brackets. The glass or filler-reinforced plastic brackets exhibited significantly higher static frictional values than the metallic slot type brackets (P < .001). The hybrid polymer with inserted metal slot brackets showed relatively lower surface roughness and frictional values compared with the stainless steel control bracket. Glass or filler-reinforced plastic brackets showed higher frictional resistance than metallic slot-type brackets. A plastic bracket with inserted metal slot may be the best choice among plastic brackets for low frictional resistance and to avoid damage from sliding movements of the archwire.

Frictional resistance in monocrystalline ceramic brackets with conventional and nonconventional elastomeric ligatures

BackgroundThe objective of this study was to compare the frictional forces generated by three types of monocrystalline ceramic brackets coupled with conventional elastomeric ligatures (CEL) and nonconventional elastomeric ligatures (NCEL) during the alignment of apically displaced teeth at the maxillary arch.MethodsAll tests (a total of 480 tests) were carried out in a dry state on a universal testing machine with a testing model consisting of three 0.022-in. monocrystalline ceramic preadjusted brackets (from the maxillary right second premolar through the right central incisor). The canine bracket was bonded to a sliding bar that allowed for different vertical positions. The frictional forces generated by a 0.012- and 0.014-in. superelastic nickel titanium wire (SENT) with conventional and nonconventional ligatures at various amounts of canine misalignment (1.5, 3.0, 4.5, and 6.0 mm) were recorded. Comparisons between the different types of bracket-wire-ligature systems were carried out by means of analysis of variance on ranks with Tukey's post hoc test (P < 0.05).ResultsNo significant differences were assessed among the three types of monocrystalline brackets with NCEL when coupled with 0.012-in. SENT. Radiance brackets with NCEL coupled with 0.014-in. SENT showed significantly greater frictional force than Inspire Ice brackets and Pure brackets with NCEL. A significantly greater amount of frictional force was generated with CEL when compared with NCEL for all the tested variables, with the exception of the Pure brackets with 0.012-in. SENT at 1.5 and 3.0 mm of canine misalignment where similar frictional forces were found.ConclusionsNonconventional elastomeric ligatures are able to reduce friction in monocrystalline ceramic brackets.

Effect of tribochemical silica coating on the shear bond strength of rebonded monocrystalline ceramic brackets

본 연구는 탈락된 세라믹 브라켓을 tribochemical silica coating하고 nano-filled flowable composite resin(Transbond Supreme LV, 3M Unitek, Monrovia, Calif, USA)을 이용하여 재접착하였을 때 교정치료에 충분한 접착강도를 얻을 수 있는지 평가하기 위해 시행하였다. 총 60개의 소구치를 준비하여 다음의 4개 군으로 나누었다:Tribochemical silica coating (TC) + Transbond Supreme LV (LV), TC + Transbond XT (XT), Sandblast treatment(SA) + LV, SA + XT. 재처리된 세라믹 브라켓은 각각의 접착제를 이용하여 치아에 부착하였다. 시편들을 상온의 생리식염수에 1주일간 보관한 뒤 열순환을 시켰다. 만능시험기로 전단접착강도를 측정한 뒤 파절양상을 평가하였다. TC군은 임상적으로 충분한 강도를 보였다(TCLV: 10.82 ± 1.82 MPa, TCXT: 11.50 ± 1.72 MPa). 하지만 SA군은 TC군에 비하여 유의하게 낮은 전단접착강도를 보였다(SALV: 1.23 ± 1.16 MPa, SAXT: 1.76 ± 1.39 MPa, p ＜ 0.05). LV군과 XT군의 전단접착강도는 유의한 차이가 없었다. TCLV, TCXT군 모두 시편의 77%가 접착제에서의 파절을 보였고, 각 군당 1개씩의 시편에서 법랑질 파절이 관찰되었다. SA군은 모든 파절이 브라켓과 접착제 계면에서 발생하였다. LV군과 XT군의 탈락양상에는 유의한 차이가 없었다. 이상의 연구 결과에서 보면 nano-filled flowable composite resin과 tribochemical silica coating 처리를 이용하여 세라믹 브라켓을 재접착하면 충분한 전단접착강도를 얻을 수 있다. 단 법랑질 파절의 가능성이 있으므로 탈접착 시 적절한 기구와 기술을 이용해 주의깊게 브라켓을 제거해야 한다. (대치교정지 2010;40(3):184-194)