Min Young Kim
5th year, 14 gr.
COMPARISON OF FRICTION AND SHEAR BOND
STRENGTH CHARACTERICSTICS BETWEEN
AESTHETIC AND METAL BRACKETS
Master’s Thesis
Kaunas, 2017
LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY
FACULTY OF ODONTOLOGY ORTHODONTIC CLINIC
COMPARISON OF TOOTH-COLOURED BRACKETS WITH METALLIC BRACKETS IN ORTHODONTIC TREATMENT
Master’s Thesis
The thesis was done
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Kaunas, 5th year
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requirements and evaluation Yes Partially No 1 Summary (0,5 point)
Is summary informative and in compliance with the thesis content and
requirements?
0,3 0,1 0
2 Are keywords in compliance with the
thesis essence?
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3
Introduction, aim and tasks
(1point)
Are the novelty, relevance and significance of the work justified in the
introduction of the thesis?
0,4 0,2 0
4 Are the problem, hypothesis, aim and
tasks formed clearly and properly?
0,4 0,2 0
5 Are the aim and tasks interrelated? 0,2 0,1 0
6 Selection criteria of the studies, search methods and strategy (3.4 points)
Is the protocol of systemic review present?
0,6 0,3 0
7 Were the eligibility criteria of articles
for the selected protocol determined (e.g., year, language, publication
condition, etc.)
0,4 0,2 0
8 Are all the information sources
(databases with dates of coverage, contact with study authors to identify additional studies) described and is the
last search day indicated?
0,2 0,1 0
9 Is the electronic search strategy
described in such a way that it could be repeated (year of search, the last search day; keywords and their combinations;
number of found and selected articles according to the combinations of
keywords)?
0,4 0,1 0
10 Is the selection process of studies
(screening, eligibility, included in systemic review or, if applicable,
included in the meta-analysis)
described?
11 Is the data extraction method from the
articles (types of investigations, participants, interventions, analysed
factors, indexes) described?
0,4 0,2 0
12 Are all the variables (for which data
were sought and any assumptions and simplifications made) listed and
defined?
0,4 0,2 0
13 Are the methods, which were used to
evaluate the risk of bias of individual studies and how this information is to be used in data synthesis, described?
0,2 0,1 0
14 Were the principal summary measures
(risk ratio, difference in means) stated?
0,4 0,2 0 15 Systemiza-tion and analysis of data (2.2 points)
Is the number of studies screened: included upon assessment for eligibility
and excluded upon giving the reasons in each stage of exclusion presented?
0,6 0,3 0
16 Are the characteristics of studies
presented in the included articles, according to which the data were extracted (e.g., study size, follow-up period, type of respondents) presented?
0,6 0,3 0
17 Are the evaluations of beneficial or
harmful outcomes for each study presented? (a) simple summary data for
each intervention group; b) effect estimates and confidence intervals)
0,4 0,2 0
18 Are the extracted and systemized data
from studies presented in the tables according to individual tasks?
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19
Discussion (1.5 points)
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20 Are the limitations of the performed
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22
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Additional sections, which may increase the collected number of points 29
Annexes Do the presented annexes help to understand the analysed topic?
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30
Practical recommen-dations
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31 Were additional methods of data
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32 Was meta-analysis applied? Are the
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34 Is the thesis volume increased
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(not evaluated)
40 Is the content (names of sections and
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and aims?
-0.2 point -0.5 points
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TABLE OF CONTENTS
ABSTRACT... 1
INTRODUCTION... 2
MATERIALS AND METHODS... 3 RESULTS... 6 DISCUSSION... 9 CONCLUSIONS ... 16 REFERENCES... 16 TABLE…... 19
COMPARISON OF FRICTION AND SHEAR BOND STRENGTH CHARACTERISTICS BETWEEN TOOTH-COLOURED BRACKETS AND METALLIC BRACKETS IN
ORTHODONTIC TREATMENT: A SYSTEMATIC REVIEW
ABSTRACT
Objectives: The aim of this study is to compare the characteristics of esthetic brackets and
stainless steel braces used recently in orthodontic treatment.
Methods: Articles were searched the PubMed databases from 2006 up to March 2017 with the
key words or combinations: esthetic bracket, polycarbonate bracket, ceramic bracket. Data from the included studies were listed, including study name and author, year of publication, participations (plastic and ceramic brackets), intervention (tested mechanical and biomechanical properties) and outcome. Risk of Bias was included in the extraction procedure with ROB tool.
Results: 20 studies were included in this systematic review and data for friction forces in 11
studies and date for shear bond strength from 3 studies were extracted for narrative analysis. Frictional forces of glass fiber or filler reinforced plastic brackets is significant higher than that of metallic brackets, however, brackets with metal slots created remarkable lower frictional force compared to stainless steel brackets. Polycrystalline brackets created significant higher frictional forces than stainless steel brackets, monocrystalline, metal slot reinforced and self ligating ceramic brackets. All designs of ceramic brackets have significant higher shear bond strength compared to stainless steel brackets, except for polycrystalline brackets with polymer mesh base. Bond strength of plastic brackets was significant lower than that of metallic brackets.
Conclusions: This study is an overview about the properties of all esthetic brackets compared to
traditional metallic ones, especially the frictional force and shear bond strength.
Keywords: esthetic brackets, polycarbonate bracket, ceramic bracket, mechanical properties,
INTRODUCTION
"Beauty is a greater recommendation than any letter of introduction", Aristotle, a famous Greek philosopher, said. Undeviatingly, beauty has a great influence on human feeling and judgments. Therefore, man has had a long sought to improve his appearance, including the beauty of smile and teeth, one of the first things someone will notice about others. Orthodontic treatment appears as a way to help achieve harmony and balance of face, consequently bringing people more confidence in communication.
Evidence of orthodontics, first appeared about 3,000 years ago, was found out with the discovery of archaeologists that there were mummified remains with crude metal bands wrapped around individual teeth with catgut, which is thought to have been used to apply forces (1). Later, in 400-500 BC, Hippocrates and Aristotle both mentioned in their writings the correction of tooth irregularities. Orthodontic treatment has gradually developed and improved noticeably, as well as the development in the design of orthodontic appliances. There are two broad categories of appliances: fixed and removable. Removable appliances are known to be simple and do not affect much the esthetic appearance of patient during treatments, but it just can be applied in the minor cases of malocclusion with the cooperation of patients. In contrast, fixed appliances are the kind that the orthodontist attaches and remain on until they are removed from the teeth so they do not need the patient cooperation and can give greater range of movement of teeth to treat more complicated cases of tooth irregularities but less esthetic than the removable ones.
Recently, with the improvement in awareness related to oral health and developments of equipment, methods and techniques in orthodontics, new field of adult orthodontics have opened, aside from orthodontic therapy was for children and young adults. However, the adult patients as well as any orthodontic patient who give importance to their appearance and for social or work reasons both have higher demands for aesthetic results, especially during the treatment phase. Therefore, they would probably refuse visible orthodontic treatment therapy. For these cases, there is a growing request for esthetic orthodontic appliances (2). By the effect of this demand, most of the companies produced many new esthetic appliances. From the limited options of fixed
appliances made from metallic materials, which is easily visible and less esthetic, nowadays, orthodontics has greatly developed regarding esthetic materials. Orthodontic brackets are becoming smaller and more diverse. Moreover, the esthetic appliances has been designed and broadly applied as an alternative for patients that are unwilling to use metallic appliances. Lingual orthodontics, clear plastic aligners (Invisalign) and esthetic braces, including esthetic brackets and esthetic archwires, are becoming the promising esthetic appliances of modern orthodontics.
Several published studies have attempted to compare mechanical properties and clinical performances of esthetic brackets (also known as tooth-colored brackets) with traditional metal brakets - the golden standard of orthodontic care - as well as among esthetic brackets themselves. As known, esthetic brackets are obviously more transparent than metal brackets and thus more adaptable to the tooth’s natural color. However, these brackets still exhibit many problems, such as the discoloration caused by water absorption (3, 4), tie-wing fracture and slot tie-wing fracture and slot distortion due to lack of strength and stiffness, increased slot roughness (5), and generate significantly higher frictional forces than mental brackets (6-9). To overcome the shortcomings of esthetic brackets, self –ligating brackets have been introduced and shown to have outstanding advantages compared to conventional brackets (10, 11).
However, up to now, there was no overview about comparison the properties of all esthetic brackets and traditional metallic appliance. Thus, the aim of this study is to compare the characteristics of esthetic brackets used recently in orthodontic treatments and stainless steel braces. This systematic review might provide evidence to help an orthodontic decide which tooth-colored bracket is appropriate for a particular patient.
MATERIALS AND METHODS
This study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) (12)
Search strategy for the identification of studies
The following search strategy was used for the identification of studies: Electronic databases, from PubMed, up to March 2017 were searched with these key words or combinations: esthetic
bracket, polycarbonate bracket, ceramic bracket. Titles and abstracts of all the studies were read by examiner without prejudiceabout the names of the authors or the publication dates. The full-text articles of the studies with the inclusion criteria were re-evaluated before the final decision. The search was completed with a review of the references cited in the selected articles to identify additional studies not found in the initial search.
The PICO question (Population, Intervention, Comparison and Outcome) was determined according to PRISMA statement in order to obtain a clear clinical question and better suitability for studies inclusion. The "population" refers to types of esthetic brackets. “Intervention" is the mechanical and biomechanical properties in vitro and in vivo of esthetic brackets. The "comparison" is the comparison of esthetic brackets and traditional appliances. And finally, the "Outcome" evaluated was the presence of a comparison between esthetic and traditional brackets in mechanical and biomechanical properties.
Study screening criteria
Before the study, a screening protocol was developed, and the following inclusion criteria were established.
1. Studies were reported in English, which was clinical research from 2007 to 2017.
2. Studies comparing mechanical properties and biomechanical properties of esthetic brackets in comparison with stainless steel brackets.
Studies were included which were review or were not reported in English, do not involve the topic of study (mechanical and biomechanical properties), do not have full-text or do not have the control group to compare. The authors of the publications were contacted for more information when necessary.
All the articles selected in the electronic and manual searches were evaluated in accordance with the established inclusion criteria. Any disagreements between the examiners were resolved by consensus or by consulting another examiner.
Data collection process
Data extraction was performed, and data from the included studies were entered on a customized data collection form for details, including study name and author, year of publication, participations (aesthetic brackets), intervention (tested mechanical and biomechanical properties) and outcome.
Risk of bias assessment
Risk of Bias was included in the extraction procedure with The Cochrane Risk of Bias Tool that include 5 processes: selection bias, performance bias, detection bias, attrition bias, reporting bias and each process assessed as low risk, high risk, and unclear.
Table 1- Risk of bias assessment
Study Random sequence generation Allocation concealment Incomplete outcome data Double blind study Other sources of bias T.K.S Fidalgo
et al. 2011 (15) Low Low Low Low Low S.H. Choi et al.
2014 (16) Low Low Low Low Low Vanessa Nínia
Correia Lima et al. 2010 (17)
Low Low Low Low Low
John C. et al.
2009 (20) Low Low Low Low Low B Sunil Kumar
et al. 2014 (22) Low Low Low Low Low Claire L
Williams et al. 2016 (21)
Low Low Low Low Low
Valiollah Arash et al.
2015 (24)
Low Low Low Low Low
Azam Pasha et
al. 2015 (25) Low Low Low Low Low Y.G.Reddy et
al.2014 (26) Low Low Low Low Low M.Y.Ansari et
al. 2016 (27) Low Low Low Low Low Javad Chalipa
Synthesis of results
Relevant data of interest on the previously stated variables (Journal-author, Composition, Tested properties, outcome) were collected and organised into table. (Table 2 and 3)
RESULTS
Electronic databases were searched with keywords and combinations, resulted in 228 studies, in which 28 studies were for the key word “polycarbonate bracket”, 200 studies were for “ceramic bracket”. After removing 20 studies which were duplicated, 177 studies which were not relevant to the topic, 31 were selected in accordance with inclusion and exclusion criteria. After complete reading, 8 studies were excluded for not having the control group as mentioned in study screening criteria method. In addition, 7 of the selected studies were excluded because of lacking the full-text and it was impossible to contact the authors for more information. Therefore, 16 studies were included in this systematic review and data was extracted in Table 2 and Table 3.(14-17, 19-27)
It can be seen in Table 2 in Table 3 that friction force is a characteristic of brackets that are especially concerned in studies of brackets. As known, friction force at bracket/archwire interface on the sliding mechanics plays an important role in the translation of tooth movement along the archwire Frictional forces should be understood and controlled because their increase may be an advantage when used for anchorage, but harmful because of their effects in sliding mechanics (29). Thus, to have a more reliable confirmation about frictional properties of esthetic brackets in comparison with traditional metallic brackets, the data of friction force in 3 studies of plastic brackets and 7 studies of ceramic brackets was extracted and listed in Table 4 and 5 after changing to the same unit of force, Newton (N).
Meta-analysis cannot be performed due to the different conditions that were set up in each study (in special environment as artificial saliva or with various kinds of archwires and ligations). Based on the outcome of the studies listed in Table 4, it can be seen that the frictional forces of glass fiber or filler reinforced plastic brackets is significant higher than that of metallic brackets. Thus, adding ceramic and glass fibers to polycarbonate brackets have no benefit in terms of
frictional forces. On the other hand, plastic brackets with metal slots created remarkable lower frictional force compared to stainless steel brackets.
Table 4- Friction forces of plastic brackets compared with metallic brackets (N)
Study Polycarbonate Brackets (PB) Metal slot reinforced Polycarbonate Brackets (MRPB) Glass-reinforced Polycarbonate Brackets (GRPB) Filler-reinforced Polycarbonate Brackets (FRPB) Stainless steel Brackets (SSB)
n Mean (30) n Mean (30) n Mean (30) n Mean (30) n Mean (30)
T.K.S.Fi dalgo et al. 2011 (15) 15 1.48 (0.62) - - - 15 1.37 (0.26) S.H.Choi et al.2014 (16) - - 8 1.931 (0.261) 8 3.113 (0.17)* 8 2.797 (0.208)* 8 2.149 (0.137) V.N.C.Li ma et al. 2010 (17) - - - - 60 0.759 (0.011)* - - 60 1.511 (0.022)
Star sign (*) indicates a significant difference between intervention group and control group ( stainless steel brackets) (p<0.05)
In Table 4, shows that polycrystalline brackets created significant higher frictional forces than stainless steel brackets in most of the studies while there is no significant difference between monocrystalline brackets and metallic ones. Furthermore, both the advanced pol ycrystalline brackets, metal slot reinforced and self ligating ceramic brackets, were reported to have the frictional force comparable to stainless steel brackets (p>0.05)
Table 5- Friction forces of ceramic brackets compared with metallic brackets (N)
Study Monocrystalline ceramic brackets ( MCB) Polycrystalline ceramic brackets (PCB) Metal slot reinforced (MRCB) Self ligating ceramic brackets (SLCB) Stainless steel brackets (SSB)
n Mean (30) n Mean (30) n Mean (30) n Mean (30) n Mean (30)
Fidalgo et al. 2011 (15) S.H.Cho et al 2014 (16) 8 4.052 (0.47) - - - 8 2.149 (0.137) J.C. Vou douris et al. 2009 (19) 10 0.98 (0.5027) 10 1.8515 (0.404) - - 10 0.0833 (0.0693)* 10 1.5484 (0.3272) B.S.Kum ar et al. 2014 (21) - - 10 6.04 (0.392)* 10 4.44 (0.587) - - 10 4.02 (0.539) C.L.Will iams et al. 2016 (20) - - 4.68 (0.6)* 2.55 (1.1) 2.92 (0.5) 3.63 (0.77) V.Arash et al. 2015 (23) 10 3.479 (0.3894) 10 4.147 (0.3723)* - - - - 10 3.283 (0.2244) A.Pasha et al. 2015 (24) - - - - 40 0.943 (0.16244) 20 1.05206 (0.16533) 40 1.5525 (0.32644)
Star sign (*) indicates a significant difference between intervention group and control group (stainless steel brackets) (p<0.05)
Shear bond strength also play an important role in orthodontic treatment. An ideal esthetic bracket not only need to be aesthetically appealing but also be able to bond to tooth surface with adequate strength to accomplish the treatment and that bond can be broken at debond without tooth/restoration surface damage, moreover, possible for rebonding. So the information about shear bond strength of various esthetic ceramic brackets in comparison with stainless steel brackets was collected and listed in Table 6. It can be seen that all designs of ceramic brackets have significant higher shear bond strength compared to stainless steel brackets, except for polycrystalline brackets with polymer mesh base. For plastic brackets, only one study was found of MM Pitchon et al. that compared the bond strength of plastic brackets and metallic one. Bond strength of plastic brackets was reported to be 15.25±0.3 Mpa, which was significant lower than that of metallic brackets, 24.30±3.0 Mpa.
Table 6- Shear bond strength of ceramic brackets and stainless steel brackets (Mpa) Study Monocrystalli ne ceramic brackets ( MCB) Polycrystallin e ceramic brackets (PCB) Polycrystalli ne ceramic brackets with adhesive precoated base Polycrystalline with microcrystalli ne mechanical base Polycrystallin e with polymer mesh base Stainless steel brackets (SSB) n Mean (30) n Mean (30) n Mean (30) n Mean (30) n Mean (30) n Mean (30) Y.G.Redd y et al.2014 (25) - - 20 20.68* - - - - 20 12.15 M.Y.Ansa ri et al. 2016 (26) 10 23.45 (5.09)* 10 20.13 (5.2)* 10 27.26 (1.73)* 10 17.54 (1.91) 10 17.5 (2.41) Javad Chalipa et al.2016 (27) 8 10.74 (3.18) - - - 8 24.92 (6.37) DISCUSSION
Tooth colored brackets are a low-visibility alternative to traditional metal braces. Plastic and ceramic brackets have minimal visual impact and much less noticeable than metal braces, even up close. Therefore, these esthetic braces are largely responsible for the increase in popularity of orthodontic treatment in teens and adults.
Figure 1 – Plastic orthodontic brackets
Plastic brackets, initially made of polycarbonate and plastic molding powder, were first established in the early 1970s as the aesthetic alternative to metal brackets (30). Plastic brackets are obviously more transparent than metal brackets and thus more adaptable to the tooth’s natural color. It was also reported that there is no difference in cell viabily and oxidative stress between conventional plastic or self-ligating plastic brackets and metallic brackets (18). In addition, the shear bond strength of plastic brackets was shown to be significant lower than that of metallic brackets, thus, these brackets may not affect the enamel surface and is clinically acceptable (14). However, these polycarbonate brackets still exhibited many problems, such as increasing of bracket width and displacement of bracket wings, which is significant higher than stainless steel backets (13).
To overcome the shortcomings of esthetic brackets made of polycarbonate alone, there has been several research undertaken to improve mechanical strength employing new polymers with increased stiffness (30), incorporation of smooth metallic slots (5) , and polymer reinforcement with fiberglass (31) or ceramic (32) . Furthermore, the shape of the bracket bases was modified to increase resin bonding without primers, promote bracket debonding during treatment completion, and minimize enamel damage related with debonding procedures (32).
Brackets reinforced with ceramic or fiberglass fillers and/or metal slots have been recently announced and are considered as prominent appliances in aesthetic orthodontics. However, adding ceramic and glass fibers to polycarbonate brackets was reported to have no benefit in terms of frictional forces (Table 4).
Figure 2- Metal slot-reinforced polycarbonate brackets
On the other hand, from data we collected, metal slot-reinforced polycarbonate brackets (Figure 2) appear to be capable of generating the desired torque on teeth under clinical conditions (33-36) as well as having lowest slot roughness (37), which was considered to affect sliding mechanics (38). A study of Choi et al.2014 suggested that a metal slot inserted into a plastic bracket may be the best choice among plastic brackets for low frictional resistance and to avoid damage from the sliding movements of the arch wire (16).
Self-ligating brackets are further recent developments. These brackets, introduced as Russel's accessories in the mid-1930s, are systems that have a mechanical device designed to close the edgewise slot (39). The polycarbonate ligatureless system (Figure 3) have been shown to have significantly lower frictional forces compared to conventional brackets (Table 4) resulting in a shorter treatment time (40, 41). Thus, their use has become common in recent years.
CERAMIC BRACKETS
Figure 4- Ceramic orthodontic brackets
In the mid 1980’s, the first brackets made of ceramic materials were introduced into the field of orthodontics (42). All currently available ceramic brackets are mainly made of aluminium oxide. However, depending their distinct differences in method of fabrication, there are two types of ceramic brackets, that are polycrystalline and monocrystalline ceramic brackets (43, 44). The producing process is important to make differences in the clinical performance among ceramic brackets of distinct manufacturers. The production of polycrystalline brackets (Figure 5) is less complicated than monocrystalline ones, and thus these brackets are more popular at present (45, 46). The most apparent difference between the two is their optical clarity. Monocrystalline ceramic brackets are noticeably clearer than polycrystalline brackets and hence are translucent. Moreover, the tensile strength is much higher in single crystal alumina than in polycrystalline
alumina, and both of them are significantly more than stainless steel (42, 43). This is the reason that the only Siamese ceramic brackets have been produced from monocrystalline alumina (43).
Figure 5- Polycrystalline ceramic brackets
Ceramic brackets have been claimed to offer many advantages over the traditional aesthetic appliances, such as color stability and strength (Figure 4). Ceramic brackets were reported to have no significant difference in cell viability compared to metallic brackets (18). Futhermore, there is clinical acceptable increase of bracket width and displacement of bracket wings of ceramic brackets (13)
However, the frictional force of conventional polycrystalline brackets is significant higher than metallic brackets (Table 5). Polycrystalline ceramics with their rougher surface have a higher coefficient of friction than monocrystalline ceramics.The frictional resistance offered by ceramic brackets used in combination with wires of different alloys and sizes, such as Stainless steel, cobalt-chromium, beta-titanium, and nickel-titanium wires, is significantly stronger than stainless steel brackets (47-50).
Figure 6- Ceramic bracket with metal slot
Manufacturers have made an effort to improve the frictional characteristics of polycrystalline ceramic brackets by adding metal lined/reinforced archwire slots (Figure 6). It is claimed to offer smoother sliding mechanics and additional strength, to endure torque forces, but still preserve the esthetic appeal.Various metal slot reinforced polycrystalline brackets are currently introduced to the market.
The shear bond strength of ceramic brackets also hase been reported by several studies to be significant higher than metallic brackets, except ceramic bracket with polymer mesh base (Table 6). The excessive bond strength and frictional forces may result in fragments on the tooth surface or even peeling of enamel or cracking due to debonding frequently, bracket breakage and fracture.
An ideal ceramic bracket not only need to be aesthetically appealing but also be able to bond to tooth surface with adequate strength to accomplish the treatment and that bond can be broken at debond without tooth/restoration surface damage, moreover, possible for rebonding (54). To cement ceramic bracket to tooth surface, an adhesive should be used. However, aluminium oxide composition in ceramic brackets makes them not be able to have chemical bonding with acrylic and diacrylate adhesives. Therefore, a silane coupling agent was used as a chemical mediator
between the early ceramic brackets and the adhesive resins. The ceramic bracket with this chemical retention exhibited significantly high bond strength (Table 6) that caused the enamel/adhesive interface to be stressed during debonding, thus, was able to damage irreversibly the enamel (53).
To address this problem, various new designs of ceramic bracket with mechanical base are now introduced, such as microcrystalline, mechanical ball, dovetail, dimpled chemo/mechanical, silane coated buttons and polymeric bases. Through these mechanical retentions, ceramic brackets are cemented to tooth surface, using standard light or chemically cured adhesives, without additional bonding agents. It is claimed that this kind of retention remains consistent bond strengths and debonding characteristics comparable to that of metal brackets base (51, 52). It have shown that ceramic bracket with polymer mesh base had adequate bond strength and caused less enamel damage at debond compared to the chemically retained one (Table 6). Type of adhesive, condition of enamel and etching time also have effects on bondingstrength (53, 54).
Despite of their unattractive appearances, mental appliances have been the mainstay of the orthodontic armamentarium for centuries. Recently, ceramic and polycarbonate brackets with their advanced esthetics compared to conventional stainless steel have been well accepted by patients and even positively sought after. However, many orthodontic practioners are not willing to accept them becauce of their perceived unfavourable clinical characteristics. Though, they are reported to be effective and reliable at correcting malocclusions.
The technology has rapidly improved so that there are now viable aesthetic appliance alternatives which can approach both the patient’s and practitioner’s treatment goals.The disadvantages of friction, bond strength and force control have been solved by modification of the arch wire slot, new bracket base design and updated manufacturing processes. Further development and research will eventually introduced aesthetic brackets which performance is perfectly comparable to the current “Gold Standard” stainless steel bracket.
This review of aesthetic orthodontics hopefully provide basic informations for orthodontists on choosing appliances for patients who pursue an esthetic orthodontic treatments.
CONCLUSION
This study is an overview about the properties of all esthetic brackets compared to traditional metallic ones, especially the frictional force and shear bond strength. However, there is not enough sources of data to do a meta-analysis to give a more accurate conclusion about these properties of esthetic brackets in comparison with metallic ones. Further studies should be focused on these characteristics of esthetic brackets and their effect on clinical treatment in comparison with traditional brackets since these characteristics of brackets play an important roles in the successful to orthodontic treatment. This systematic review might provide evidence to help an orthodontist decide which tooth-colored bracket is appropriate for a particular patient.
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TABLES
Table 2- Studies of plastic brackets characteristics in comparison with traditional metallic brackets
Journal- Author Esthetic Bracket -Composition
Tested properties Outcome
Shear bond strength of orthodontic brackets to enamel under different surface treatment conditions. Pithon MM et al. 2007 (14) Polycarbonate bracket (Morelli): Composite
Shear bond strength Metallic and polycarbonate brackets showed clinically acceptable shear bond strengths
Friction between different wire bracket
combinations in
Pure polycarbonate bracket (American Orthodontics)
Friction force There is no significant
difference between plastic and stainless steel bracket when combined with stainless steel
artificial saliva – an in vitro evaluation T.K.S Fidalgo et al. 2011 (15) or titanium-molybdenum alloy wires Surface roughness of three types of modern plastic bracket slot floors and frictional resistance
Sung-Hwan Choi et al. 2014 (16)
1. Image (Gestenco International) : glass fiber-reinforced polycarbonate
2. Silkon M (American Orthodontics ): filler-reinforced polycarbonate
3. Esther MB (Tomy): hybrid polymer composed of polycarbonate and polyethylene terephthalate with an inserted metal slot
Frictional force The frictional force of glass fiber-reinforced or filler-reinforced polycarbonate bracket is significantly higher than that of metallic bracket.
However, there is no
significant difference between the frictional force of metal slot plastic bracket and metallic one.
Frictional forces in stainless steel and plastic brackets using four types of wire ligation
Vanessa Nínia Correia Lima et al. 2010 (17)
Glass- reinforced plastic bracket : polycarbonate composite reinforced with
30% glass fiber
Frictional force Plastic brackets generated less friction than metal brackets.
Table 3- Studies of ceramic brackets characteristics in comparison with traditional metallic brackets
Journal- Author Esthetic Bracket -Composition
Tested properties Outcome
Friction between different wire bracket combinations in artificial saliva – an in vitro evaluation T.K.S Fidalgo et al. 2011 (15) Ceramic bracket (American Orthodontics)
Friction force Ceramic bracket combined with
stainless steel wire created significant higher friction force compared to stainless steel bracket with stainless steel wire.
However, there is no significant difference between ceramic and metallic bracket when combined to titanium-molybdenum alloy wires
Surface roughness of three types of modern plastic bracket slot
Inspire Ice (Ormco): monocrystalline ceramic bracket
Frictional force The frictional force of ceramic bracket is significantly higher than that of metallic bracket.
floors and frictional resistance
Sung-Hwan Choi; Da-Young Kang; Chung– Ju Hwang (16) Self-Ligation Esthetic Brackets with Low Frictional Resistance John C. Voudouris et al. 2009 (19) Mystique (Dentsply) : ceramic Clarity (3M/Unitek) : ceramic
Friction force Ceramic brackets created significant higher friction force compared to metallic bracket when combined with both stainless steel and esthetic coated wires.
Comparative Evaluation of
Friction Resistance of Titanium, Stainless Steel, Ceramic and Ceramic with Metal Insert Brackets with Varying Dimensions of Stainless Steel Wire: An In vitro Multi-center Study
B Sunil Kumar et al. 2014 (21)
Ceramic bracket (3M Unitek)
Friction force Ceramic brackets created significant higher friction force compared to stainless steel bracket.
Frictional Resistance of Three Types of Ceramic Brackets Claire L Williams et al. 2016 (20) Mystique : self-ligating ceramic bracket
Clarity™ : metal slot ceramic bracket system Conventional ceramic bracket
Friction force Self ligating ceramic bracket system (Mystique® and neoclip, GAC International, Bohemia, NY, USA) and metal slot ceramic bracket system (Clarity™; 3M Unitek, Monrovia, CA, USA) generate significantly less resistance to sliding than conventional ceramic bracket systems (GAC International, Bohemia, NY, USA) with both 0° and 7° wire angulations. The friction level is comparable with that of conventional metal bracket systems. Comparison of the frictional characteristics of aesthetic orthodontic brackets measured using a modified in vitrotechnique Clarity (3M/Unitek): ceramic bracket with stainless steel slots
Pure (Ortho Technology): monocrystalline alumina
Friction force
Monocrystalline and polycrystalline bracket created significant higher friction force compared to stainless steel bracket.
Ceramic bracket with metal slot have no difference in friction force when compared to metallic bracket.
Nursel Arici et al. 2015 (22) ceramic bracket Transcend (3M/Unitek) and InVu (TP Orthodontics): polycrystalline alumina ceramic brackets. In vitro evaluation of frictional forces of two ceramic orthodontic brackets versus a stainless steel bracket in combination with two types of archwires Valiollah Arash et al. 2015 (23)
MA (Ormco) :
Monocrystalline
and PA (Forestadent) : Polycrystalline
Friction force The lowest mean frictional forces with round wire belonged to the SS bracket, and then polycrystalline and monocrystalline bracket. The highest mean frictional forces recorded with rectangular wire belonged to the polycrystalline, and then SS and monocrystalline brackets Comparison of Frictional Forces Generated by a New Ceramic Bracket with the Conventional Brackets using Unconventional and Conventional Ligation System and the Self-ligating Brackets: An In Vitro Study Azam Pasha et al. 2015 (24)
Clarity(3M Unitek): Conventional Ceramic bracket with metal slot Clarity™ ADVANCED(3M Unitek): advanced Ceramic Brackets
Clarity SL (3M
Unitek): Ceramic self ligating bracket
Friction force When combined with Ni-Ti wire, the friction force created by all kind of ceramic bracket is similar to that of metallic bracket.
However when combined with stainless steel wire, ceramic bracket with metal slot created the maximum friction force, followed by advanced Clarity and ceramic self ligating bracket.
The Shear Bond Strengths of Metal and Ceramic Brackets: An in-Vitro Comparative Study Y G Reddy, Rohit Sharma et al. 2013 (25) Transcend series 6000 (3M Unitek) : Ceramic
Shear bond strength Ceramic brackets are aesthetically superior and they provide greater bond strength as compared to the metallic brackets.
Shear Bond Strength of Ceramic Brackets with Different Base Designs:
1. Clarity Advanced (Unitek/3M Monrovia): Polycrystalline
Shear bond strength Ceramic brackets provide significant greater bond strength as compared to the metallic brackets.
Comparative In-vitro Study Mohd. Younus Ansari et al. 2016 (26) 2. Clarity Advanced (Unitek/3M Monrovia): Polycrystalline 3. InVu (TP Orthodontics La Porte): Polycrystalline 4. Inspire Ice (Ormco): Monocrystalline with Sapphire Comparison of Bond Strength of Metal and Ceramic Brackets Bonded with Conventional and High-Power LED Light Curing Units Javad Chalipa et al. 2016 (27)
Radiance Plus (American Orthodontics): Ceramic brackets
Shear bond strength The SBS of both brackets (metal and ceramic) by use of high-power and conventional LED units was the same.
