|
 
 |
| ORIGINAL ARTICLE |
|
| Year : 2023 | Volume
: 12
| Issue : 1 | Page : 20 |
|
Comparison of shear bond strength of bonded stainless steel brackets using three different light curing systems: An in vitro study
Shashank Soni1, Richa Shree2, Vijeta Patri3, Gaurav Jasoria4, Sapana Singh5, Ashish Kushwah6
1 Senior Lecturer, Department of Orthodontics and Dentofacial Orthpaedics, Peoples Dental Academy, Bhopal Madhya Pradesh, India
2 Reader, Department of Orthodontics and Dentofacial Orthpaedics, Buddha Institute of Dental Sciences and Hospital, Patna, Bihar, India
3 Senior Lecturer, Department of Orthodontics and Dentofacial Orthpaedics, Hi Tech Dental College and Hospital, Bhubneshwar, Odisha, India
4 Professor and Head, Department of Orthodontics and Dentofacial Orthpaedics, Maharana Pratap College of Dentistry and Research Centre, Gwalior, Madhya Pradesh, India
5 Consultant Orthodontist, Mumbai, Maharastra, India
6 Senior Lecturer, Department of Orthodontics and Dentofacial Orthpaedics, Peoples College of Dental Sciences and Research Centre, Bhopal Madhya Pradesh, India
| Date of Submission | 14-Sep-2022 |
| Date of Decision | 11-Oct-2022 |
| Date of Acceptance | 19-Oct-2022 |
| Date of Web Publication | 18-Mar-2023 |
Correspondence Address:
Ashish Kushwah
FH- 484, Deen Dayal Nagar, Gwalior, Madhya Pradesh – 474 020
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jos.jos_83_22
OBJECTIVES: To evaluate and compare the shear bond strength of stainless-steel brackets using three different light curing units
MATERIAL AND METHODS: Using three LED curing units (3M ESPE Elipar, Ivoclar bluephase, and Woodpecker I LED light cure), 120 precoated metal brackets (Gemini series, 3M Unitek) were cured. The shear bond strength was recorded using a universal testing machine.
RESULT: The shear strength of the bracket in different light-curing systems was examined with ANOVA test. The mean shear strength of group A, group B, and group C were 16.03 ± 14.30 MPA, 16.86 ± 11.89 MPA, and 20.51 ± 19.40, respectively. The result of the analysis shows that there is a major difference in shear bond strength of these three different light-curing systems with F value = 3.94 and P value 0.04
CONCLUSION: We used three LED light-curing units with different intensities and manufacturing companies. The result showed that woodpecker I LED light had significantly highest mean SBS than the other two (Elipar LED curing light and 3M ESPE, Ivoclar bluephase).
Keywords: 3M ESPE Elipar, Ivoclar bluephase, light cure units, shear bond strength, stainless steel brackets, woodpecker
How to cite this article:
Soni S, Shree R, Patri V, Jasoria G, Singh S, Kushwah A. Comparison of shear bond strength of bonded stainless steel brackets using three different light curing systems: An in vitro study. J Orthodont Sci 2023;12:20 |
How to cite this URL:
Soni S, Shree R, Patri V, Jasoria G, Singh S, Kushwah A. Comparison of shear bond strength of bonded stainless steel brackets using three different light curing systems: An in vitro study. J Orthodont Sci [serial online] 2023 [cited 2023 Oct 2];12:20. Available from: https://www.jorthodsci.org/text.asp?2023/12/1/20/371976 |
| Introduction | |  |
Bonding orthodontic attachments directly onto the enamel surface became possible by the introduction of the acid etch technique developed by Buonocore.[1] The first system developed for bracket bonding is chemically cured resin which was followed by light-cured materials.[2],[3] The application of visible light-curable composite for bonding was first described in the 1970s.[4]
Recently, photo-polymerization has become one of the important parts of dentistry. Four essential kinds of curing light are used in practice:
- Halogen light
- Plasma arc curing lights
- Laser lights
- Lights based on light emitting diode.
The first and the last are the most used devices these days.
In the 1960s, materials available for bonding were resin-based tooth-colored materials. These materials polymerized by a chemical reaction, so they are also known as chemical-curing or self-curing composites. The polymerization of self-curing composites depended on radical polymerization, which was initiated by the disintegration of benzoyl peroxide. In 1962, Bowen gave the formulation of monomer with Bis-GMA loaded up with finely ground quartz[5]—a step toward present-day composite definitions.
An ultraviolet (UV)-activated pit-fissure sealant was a pioneering light cure material that phased out into commercially available materials.[6] In 1970, the first commercial UV lights for curing dental restoration were manufactured.[6] Limited penetration ability of the UV light into the material made it inadequate in meeting the limited complexity of the solution.[7] Due to high-frequency energy of ultraviolet lights, it was more harmful to the eyes and other delicate tissues, and possibly had side effects such as corneal irritation and cataract.[8]
The next stage was to present noticeable light-activated composites. Camphor quinone was the photo-initiator most often utilized in these materials.[9],[10] In the late 1970s, in the first reported visible blue light was used to polymerize dental restorative material.[4] Dr. Bassoiuny of Britain used the first light restorative compounds seen in 1976, a quartz–tungsten–halogen (QTH) source consisting of absorbed glass and a band-pass channel that emitted light. The wavelength somewhere in the range of 400 and 550 nm is important for camphor quinone.
Blue light using QTH has been well known since the 1980s. Halogen light is an incandescent light that contains a tungsten filament and a small amount of a halogen within an inert gas, for example, iodine or bromine.[11] During the 1990s, improved and faster light output were used in treatment. The output values were between 400 and 500 mW/cm2 typically and 3000 mW/cm2.[12]
In 1998, plasma arc cure (PAC) illumination was introduced for dentistry.[11] The source consisted of two tungsten anodes enclosed in a heavy gas-filled chamber. A high electric potential is produced between the two terminals that creates an initial ionization gas and provides a conductive path (a plasma) between the electrodes.[9] The plasma also emits a strong light. This high performance induces less curing in a few moments.[11],[13]
Laser lights accomplish a high light power; however, they could not capture the dental light market. They generate heat and tend to be bigger and extremely expensive.[11] In the USA, dental assistants were additionally precluded from utilizing these lights, and accordingly, these lights became obsolete rather rapidly.[14]
Light-emitting diode (LED) lights that discharged blue light were introduced in dentistry in the mid-90s with most economically accessible light in 2000. LED lights available during this period have less optical radiation and are less harmful, much more effective than past light sources utilized in dentistry and lightweight. Furthermore, they can be battery-powered for simplicity in use.[15]
Most create a generally narrow spectrum of light in the 400–500 nm range (with top at around 460 nm).[11]
They are available in numerous varieties: large and small, corded and cordless, and polywave and monowave. Mahn[11] noticed that few investigators have demonstrated that LED lights can polymerize composite materials to an identical depth of fix and with proportionate compressive[16] and flexural strength[17],[18] as this polymerized light-curing material utilize halogen lights at the same light intensity. LED lights have quickly replaced their halogen light forerunners as the standard practice light source.[19]
All these positive aspects make them an excellent alternative to the conventional halogen lamps. Dependability of bonded brackets and the clinical time spent at bracket bonding are major worries for all orthodontists. Consequently, high-intensity LED lights with a significant decrease in the curing time to bond orthodontic brackets are familiar with spare the profitable clinical time. Makers of new-age high-intensity LED units to assert that they join every one of the upsides of their forerunners with a significant decrease in the curing time; however, there aren't much accessible data on their in vitro or in vivo behavior.[17]
This study is an attempt to evaluate and compare the shear bond strength of brackets bonded using three different LED light cure systems to find out whether light intensity or make or build plays any role in aiding the curing of bonding composite or the long-term stability of the bonded bracket. In this study, three reputed brands of LED curing systems have been compared keeping all the other parameters the same.
| Methods and Materials | | |
This is a comparative in vitro study.
Source of the data
The data comprised 120 extracted premolar teeth of patients undergoing fixed orthodontic treatment, collected from the Department of Oral and Maxillofacial Surgery.
Inclusion criteria
- The extracted premolars should have an intact buccal surface.
- Premolar extraction for orthodontic treatment purposes.
Exclusion criteria
- Fractured/chipped/cracked/carious/restored or otherwise damaged premolars.
Methodology
A sample of 120 extracted human premolar teeth was used after the inclusion and exclusion criteria were applied. Soon after the extractions, the teeth were cleaned. Plaster of Paris was used to make the blocks, and all teeth were embedded in these blocks. Transbond XT light cure adhesive system was used to bond all brackets to the teeth.
Bracket used
A total of 120 pre-adjusted edgewise premolar stainless steel brackets with a 0.022″× 0.028″ slot were used in the study (3M Gemini series brackets Roth).
Sample size
A total of 120 premolars are extracted for orthodontic treatment purpose.
Procedure
The sample for the study consisted of 120 extracted human premolar teeth. Immediately after extraction, the teeth were cleaned using distilled water to clean any debris, bloodstain, etc., and were stored in 70% ethyl alcohol. These teeth were mounted as square cubes with plaster of Paris exposing only their crown.
Bonding procedure
The conventional method using 37% phosphoric acid gel was applied to the buccal surface of the tooth for 30 seconds. The tooth was then rinsed with water spray for 20 seconds and dried for 10 seconds until the buccal surface of the etched teeth appeared to be frosty white. After etching, a thin coat of the primer (Transbond XT Primer; 3M Unitek) was applied. The adhesive resin (Transbond XT Primer; 3M Unitek) was placed on the bracket base, and the bracket was positioned on the tooth surface using bracket holding tweezers with optimum pressure. Excess adhesive was removed with an explorer. The adhesive resin was polymerized for a total of 10 seconds. The light cure adhesive was placed on the bracket base. Premolars were divided into three groups, and each group includes 40 teeth. Brackets were bonded with LED. Bonding is done according to the manufacturer's instructions.
Group A - Elipar LED curing light; 3M ESPE
Group B - Ivoclar bluephase
Group C - Woodpecker I LED light cure.
Group A: A total of 40 teeth were treated according to the manufacturer's instructions with Transbond XT adhesive. The conventional adhesive systems use three different agents, i.e., an enamel conditioner, a primer solution, and an adhesive resin. In this group a LED, a light-curing unit (Elipar LED curing light, 3M ESPE) with an output power of 1200 mW/cm2 was used for 10 sec.
Group B: A total of 40 teeth were treated according to the manufacturer's instructions with Transbond XT adhesive. Conventional adhesive systems use three different agents, i.e., an enamel conditioner, a primer solution, and an adhesive resin. In the second group using a LED, a light-curing unit (Ivoclar bluephase) with an output power of 1200 mW/cm2 was used for 10 sec.
Group C: A total of 40 teeth were treated according to the manufacturer's instructions with Transbond XT adhesive. Conventional adhesive systems use three different agents, i.e., an enamel conditioner, a primer solution, and an adhesive resin. In the third group using a LED, a light-curing unit (Woodpecker I LED light cure) with an output power of 3000 mW/cm2 was used for 10 sec.
| Result | | |
The study was conducted to evaluate the shear bond strength of stainless-steel brackets bonded using three different light cure units. To conduct the study, 120 premolars extracted for orthodontic purpose were collected and bonded with pre-adjusted edgewise premolar stainless-steel brackets with a 0.022″× 0.028″ slot and a light cure composite resin system. The teeth were divided into three groups based on the light curing unit used for bonding, i.e., Group A: 3M ESPE Elipar, Group B: Ivoclar bluephase, and Group C: Woodpecker I LED light cure. The shear bond strength was measured using a universal testing machine.
Statistical analysis
The data was translated from a pre-coded survey form on a computer. The data entry, validity checks, and formation of desired results (as per the analysis plan) were done using SPSS (version 22.0). The level of statistical significance was at P ≤ 0.05. The comparison between the shear strength of the different light-curing units was done by using the ANOVA test while the intergroup comparison was done with a t-test. The mean shear strength of Group A was 16.03 ± 14.30 MPA, the mean shear strength of Group B was 16.86 ± 11.89 MPA, and Group C was 20.51 ± 19.40. The analysis shows that there is a significant difference in the shear strength of different light-curing system with F value = 3.94 and P value 0.04 [Table 1]; [Figure 1]. | Table 1: Comparison of shear bond strength of the three light systems used for bonding
Click here to view |
 | Figure 1: Description of shear bond strength of different light-curing systems
Click here to view |
The bond strength of groups A and B compared with student t-test shows that the mean shear strength of Group A was 16.03 ± 14.30 and Group B was 16.86 ± 11.89. The result shows no significant difference between the two groups with t-value of 0.28 and P value of 0.78 [Table 2]; [Figure 2].
The bond strength of groups A and C compared with student t-test shows that the mean shear strength of Group A was 16.03 ± 14.30 and Group C was 20.51 ± 19.40. The result shows a significant difference in mean shear strength between the two groups with t-value of 2.77 and P value of 0.02. [Table 3]; [Figure 3].
The bond strength of groups B and C compared with student t-test shows that the mean shear strength of Group B was 16.86 ± 11.89 and Group C was 20.51 ± 19.40. The result shows a significant difference in mean shear strength between the two groups with t-value of 2.02 and P value of 0.03 [Table 4]; [Figure 4].
| Discussion | | |
Direct bonding in modern-day orthodontic clinical practice owes to the spearheading work by Buonocore in 1955 who particularly maintain the growth of methyl methacrylate resins after a treatment of 85% orthophosphoric acid for 30 seconds which enhance the bond strength. In addition, Bowen produced a bisphenol-A glycidyl dimethacrylate (bis-GMA) resin, which was comparatively more stable than previous resins and had better properties in the oral condition when filled with an inorganic inert filler. Third, the acid etch technique was first used by Newman for dental protection brackets with an epoxy-derived resin. Bowen's bis-GMA resin has sufficient viscosity required to penetrate the etched enamel surfaces to regularly brush and abrasion and join forces to achieve expected quality.
An important improvement in the field of dentistry, including orthodontics, was when epoxy resins were designed by Castan in 1938, which changed due to today's composite resins. In 1955, Buonocore utilized phosphoric acid to condition enamel, which inevitably turned into the reason for bonding brackets and different connections onto the teeth directly. In 1962, Raphael Bowen added another resin, a dimethylacrylate (2,2-bis [4 {2-hydroxy-3-phenyl-propyloxy-methacryloxy}], called bis-GMA. Bis-GMA is the result of a reaction of glycidyl methacrylate and bisphenol A used by many in accomplishing bonding on teeth. Newman presented a light-curing adhesive in orthodontic treatment in 1965, which had relatively faster working time. In 1970, Retief developed an epoxy resin system intended to resist the powers of orthodontics. Likewise, around the same time, Michael Buonocore and L.D.Caulk revealed light-activated composite resins.
UV-cured resins were manufactured in 1972. This treatment allowed a satisfactory working time with the light, the reality being that the setting time was under the control of the doctor. In 1977, primary adhesive with special preservative formula (3M Unitech) and Nuva-tac (Caulk, Milford, Del) were offered. In 1987, methyl methacrylate (MMA) adhesive included ortho-concise, Transbond was available in the market. In 1989, hybrid composites were presented with UGDMA/TEGDMA as the resin matrix. In 1991, Unitek introduced adhesive pre-coated brackets (APCs). In 1996, flowable composite with TEGDMA as resin matrix was introduced.[18]
In 2007, Duncan W. Higgins mentioned a few advantages of light-cured adhesives over the self-cured adhesives. He said that light-cured adhesives had moderately high initial bond strength and an expanded working time.
TQH restoration units have traditionally been used as visible light sources. A broad-spectrum emission is created by TQH, which is an incandescent light. The lamp becomes very hot because most of it is infrared energy, which produces excessive heat. The lifetime of a halogen bulb is about 100 hours, and the power output is reduced to some extent after usage as there result of dissolving components and high temperature.[20] These units emit a 40-second light, and a 400–900 mW/cm2 relief site is programmed to achieve sufficient polymerization per second which is used for curing the light-curing materials.[20],[21]
LEDs, on the other hand, have lifespan of over 10,000 hours and have very little degradation of light output, a particularly favorable position while contrasting it with halogens.[22] Compared to light bulbs, no filter is required by the LEDs to provide blue light under favorable conditions. These LEDs are highly resilient to vibrations and shocks, and their light-emitting medium and low usage make them suitable for manageable application.[23]
The study was carried out keeping all the parameters same except light intensity and make of the LED light-curing unit. In the bonding process, curing time and light intensity are important determinants that influence the shear bond strength. Other factors affecting the shear bond strength are uniform and proper application of bonding composites on the brackets and inconsistent flow/voids in the adhesive layer will lead to bond failures. Also, movements of brackets during the curing process also greatly affect the shear bond strength. The bracket bonding was carried out keeping these factors under control as much as possible.
Newman et al. 's[24] findings suggest that halogen light-curing units have a significantly lower bind than LED LCUs units (p < 0.005). Another study conducted by Jacobson also reported that halogens' light-curing units have lower bond strength in comparison to LED LCUs units (p < 0.005).[25]
Gomes et al.[26] compared high-powered LED curing light and reported that on reducing the exposure time, there is a decrease in the strengthening of the bond. A study by Yagci and Buyuk reported no significant difference between SBS and QTH (40 seconds, 350 mW/cm2) and high-intensity LED (3 seconds, 3,200 mW/cm2).[27] Dongpaiboon et al.[28] do not report existence of a vital difference between QTH (20 seconds, 410 mW/cm2) and high-intensity LEDs (6 seconds, 2230 mW/cm2). Udomthanaporn et al.[29] reported that high intensity with adequate time gives more bond strength because in their study high intensity LED light had a low SBS due to less time. Ward et al.[30] found that there were no significant differences in the degree of bond failure when the different intensity of LED light was used.
In the current study, the correlation of the shear strength of the bracket was analyzed with an ANOVA test for different light-curing systems. The mean shear strength of Group A (Elipar LED curing light; 3M ESPE) is 16.03 ± 14.30 MPAl; of Group B (Ivoclar bluephase) it is 16.86 ± 11.89 MPA; and of Group C (Woodpecker I Led Light Cure) it is 20.51 ± 19.40. The result of the analysis reveals that there are some vital differences between the shear strengths of different light-curing systems with F value = 3.94 and P value 0.04.
The bond strength of Group A with 1200 mW/cm2 intensity and of Group B with the same intensity was compared using student t-test. It shows the mean shear strength of the group is 16.03 ± 14.30 and of Group B is 16.86 ± 11.89. No vital differences are revealed in the results between the two groups with t-value of 0.28 and P value of 0.78.
The bond strength of Group A with 1200 mW/cm2 and Group C with 3000 mW/cm2 was compared using student t-test. It shows the mean shear strength of group A is 16.03 ± 14.30 and Group C is 20.51 ± 19.40. The outcome of the study shows a notable variation in mean shear strength between the two groups with t-value of 2.77 and P value of 0.02.
The bond strength of group B with 1200 mW/cm2 and Group C with 3000 mW/cm2 was compared using Student's t-test. It shows the mean shear strength of Group B is 16.86 ± 11.89 and Group C is 20.51 ± 19.40. The outcome reveals that there is a notable variation in the mean shear strength between the two groups with t-value of 2.02 and P value of 0.03.
Vandewalle et al.,[31] mention that the more severe the light source, the more photons are available for absorption by photosensitizers. The higher the number of photons, the more the camphor quinone molecules is absorbed in the excited state, reacting with amines and forming free radicals for polymerization. This is supported by Mavropoulos et al.[32] and Staudt et al.[33] who explain that SBS is influenced by intensity of the beam in the orthodontic bracket joint. More recently, manufacturers have developed high-intensity LED units that claim to provide a significant reduction in the exposure time required for orthodontic attachments.
In this study, three LED curing units were used with varying intensities and manufacturing companies. Results showed that Woodpecker I LED light has a notably higher SBS mean than the other two (Elipar LED curing lights and 3M ESPE, Ivoclar bluephase).
| Conclusion | | |
Based on the results, the following conclusions are drawn from the study.
- There is a statistically significant difference in the shear bond strength of the three different light-curing systems with P value of 0.04.
- There is no statistically significant difference between Group A and Group B, i.e., Elipar LED curing light, 3M ESPE, and Ivoclar bluephase when compared (p-value 0.78).
- There is a statistically significant difference between Group A and Group C (p-value 0.02.), i.e., Elipar LED curing light, 3M ESPE and Woodpecker I Led Light Cure and in-between Group B and Group C (p-value 0.03), i.e., Ivoclar bluephase and Woodpecker I Led Light Cure.
It is concluded that the Woodpecker I LED Light Cure gives better results when keeping all variables the same; this could be attributed to the high intensity (3000 mW/cm2) of this LED light.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
| 1. | Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res 1955;34:84953.  |
| 2. | JohnsonWT Jr, Hembree JH Jr, Weber FN. Shear strength of orthodontic directbonding adhesives. Am J Orthod 1976;70:55966. |
| 3. | Keizer S, ten Cate JM, Arends J. Direct bonding of orthodontic brackets. Am J Orthod 1976;69:31827. |
| 4. | Bassiouny MA, Grant AA. A visible lightcured composite restorative. Clinical open assessment. Br Dent J 1978;145:32730. |
| 5. | Bowen R. Dental filling material comprising vinyl silane treated fused silica and a binder consisting of the reaction product of Bis phenol and glycidyl acrylate. 1962; Patent No. 3,066,112. |
| 6. | Buonocore M. Adhesive sealing of pits and fissures for caries prevention, with use of ultraviolet light. J Am Dent Assoc 1970;80:324-30. |
| 7. | Tirtha R, Fan PL, Dennison JB, Powers JM. In vitro depth of cure of photo-activated composites. J Dent Res 1982;61:1184-7. |
| 8. | Main C, Cummings A, Moseley H, Stephan KW, Gillespie FC. An assessment of new dental ultraviolet sources and UV-polymerised fissure sealants. J Oral Rehabil 1983;10:215-27. |
| 9. | Rueggeberg FA. State-of-the-art: Dental photocuring--A review. Dent Mater 2011;27:39-52. |
| 10. | Stansbury JW. Curing dental resins and composites by photopolymerization. J Esthet Dent 2000;12:300-8. |
| 11. | Mahn E. Light polymerization. Inside Dentistry. 2011; Vol 7: Iss 2. Aegis online |
| 12. | Caughman WF, Rueggeberg FA, Curtis JW Jr. Clinical guidelines for photocuring restorative resins. J Am Dent Assoc 1995;126:1280-2. doi: 10.14219/jada.archive. 1995.0364. |
| 13. | Hofmann N, Hugo B, Schubert K, Klaiber B. Comparison between a plasma arc light source and conventional halogen curing units regarding flexural strength modulus and hardness of photoactivated resin composites. Clin Oral Investig 2000;4:140-7. |
| 14. | Cassoni A, Rodriques JA. Argon laser: A light source alternative for photopolymerization and in–office tooth bleaching. Gen Dent 2007;55:416-9. |
| 15. | Rueggeberg F. Contemporary issues in photocuring. Compend Contin Educ Dent Suppl 1999;20(Suppl 25):S4-15. |
| 16. | Jandt KD, Mills RW, Blackwell GB, Asworth SH. Depth of cure and compressive strength of dental composites cured with blue light emitting diodes (LEDs). Dent Mater 2000;16:41-7. |
| 17. | Meyer GR, Ernst CP, Willershausen B. Decrease in power output of new light-emitting diode (LED) curing devices with increasing distance to filling surface. J Adhes Dent 2002;4:197-204. |
| 18. | Wahl N. Orthodontics in 3 Millennia. Am J Orthod Dentofacial Orthop 2008;134:707-10. |
| 19. | Keim RG, Gottlieb EL, Nelson AH, Vogels DS 3 rd. 2002 JCO Study of Orthodontic diagnosis and treatment procedures Part 2 breakdowns of selected variables. J Clin Orthod 2002;36:627-36. |
| 20. | Martin FE. A survey of the efficiency of visible light curing units. J Dent 1998;26:239–43. |
| 21. | Rueggeberg FA, Caughman WF, Curtis JW Jr. Effect of light intensity and exposure duration on cure of resin composite. Oper Dent 1994;19:26–32. |
| 22. | Haitz RH, Craford MG, Weissman RH. Light emitting diodes. In: Bass M, editor. Handbook of Optics. 2 nd ed. McGraw Hill Inc; 1995. p. 12.1-39. |
| 23. | Nakamura S, Mukai T, Senoh M. High-Power GaN P-N Junction bluelight-emitting diodes. Jpn J Appl Phys Lett 1991;30:L1998-2001. |
| 24. | Newman SM, Murray GA, Yates JL. Visible lights and visible light-activated composite resins. J Prosthet Dent 1983;50:31–5. |
| 25. | Jacobson A. Comparison of three curing light systems for polymerization of orthodontic adhesives: An in vivo study. Am J Orthod Dentofacial Orthop 2001;120:331-2. |
| 26. | Gomes P, Portugal J, Jardima L. Effect of high-powered LED-curing exposure time on orthodontic bracket shear bond strength. Rev Port Estomatol Med Dent Cir Maxilofac 2014;55:78–82. |
| 27. | Yagci A, Buyuk SK. Shear bond strength and temperature rise of orthodontic brackets bonding by using a new 3-second LED mode. Turk J Orthod 2013;26:45-50. |
| 28. | Dongpaiboon P, Techalertpaisarn P, Promsopa N, Kananurak S. Evaluation of 3 light curing units with different light intensity on initial shear bond strength of orthodontic adhesives. CU Dent J 2014;37:149-60. |
| 29. | Udomthanaporn B, Nisalak P, Sawaengkit P. Shear bond strength of orthodontic bonding materials polymerized by high-intensity LEDs at different intensities and curing times. Key Eng Mater 2017;723:376-81. |
| 30. | Ward JD, Wolf BJ, Leite LP, Zhou J. Clinical effect of reducing curing times with high-intensity LED lights. Angle Orthod 2015;85:1064-9. |
| 31. | Vandewalle KS, Ferracane JL, Hilton TJ, Erickson RL, Sakaguchi RL. Effect of energy density on properties and marginal integrity of posterior resin composite restorations. Dent Mater 2004;20:96-106. |
| 32. | Mavropoulos A, Cattani-Lorente M, Krejci I, Staudt CB. Kinetics of light-cure bracket bonding: Power density vs exposure duration. Am J Orthod Dentofacial Orthop 2008;134:543-7. |
| 33. | Staudt CB, Krejci I, Mavropoulos A. Bracket bond strength dependence on light power density. J Dent 2006;34:498-502. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]
|
Search Pubmed for