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Year : 2022  |  Volume : 7  |  Issue : 1  |  Page : 16-18

Enamel conditioning in orthodontics ‒ A literature review

1 PG Student, Aditya Dental College, Beed, Maharashtra, India
2 Senior Lecturer, Department of Conservative Dentistry and Endodontics, Aditya Dental College, Beed, Maharashtra, India
3 Reader, Department of Orthodontics and Dentofacial Orthopedics, Aditya Dental College, Beed, Maharashtra, India

Date of Submission23-May-2022
Date of Acceptance03-Jun-2022
Date of Web Publication30-Jun-2022

Correspondence Address:
Dr. Komal Nalawade
Department of Orthodontics and Dentofacial Orthopedics, Aditya Dental College, Beed, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmo.ijmo_12_22

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The strength of the bond between the bracket and the enamel surface depends on three factors, namely, the retention mechanism of the bracket base, the adhesive material or bonding resin, and the preparation of the tooth surface. Commonly used adhesive systems employ an enamel conditioner, a primer solution, and an adhesive resin to bond the orthodontic brackets to the enamel surface. The aim of this study was to compare the effects of different enamel conditioning techniques for bracket bonding.

Keywords: Adhesive, bonding, orthodontics, resin

How to cite this article:
Nalawade K, Sarda AS, Dogra B, Hundiwale P, Khan R, Handa A. Enamel conditioning in orthodontics ‒ A literature review. Int J Med Oral Res 2022;7:16-8

How to cite this URL:
Nalawade K, Sarda AS, Dogra B, Hundiwale P, Khan R, Handa A. Enamel conditioning in orthodontics ‒ A literature review. Int J Med Oral Res [serial online] 2022 [cited 2022 Dec 4];7:16-8. Available from: http://www.ijmorweb.com/text.asp?2022/7/1/16/349241

  Introduction Top

The invention of acid etching of enamel and dentin led to the opening of various pathways in dentistry that proved to be way more efficient than the traditional methods. The shortcoming of materials due to lack of adhesion to the tooth surface was overcome by enamel conditioning. Acid etching of enamel by Buonocore in 1955 was a breakthrough in dentistry. Composites are widely used for bonding in orthodontics and pretreatment of enamel increases penetration depth and bond strength of composites exceedingly. Enamel conditioning can be brought about by various regimens that are invented and researched for regular use in orthodontic bonding practice. Buonocore was the first one to use phosphoric acid for enamel etching, and various other alternative acids and chelating agents have been studied.[1] There were many iatrogenic effects of conventional acid-etching techniques that led to contrived various new techniques. This article comprises various techniques of enamel conditioning that were adapted for better adhesion of adhesives. The creation of microporosities is fundamental to efficient bonding in orthodontics. Widely used methods of enamel conditioning comprise the usage of various acids in different concentrations, application of crystal growth phenomenon in conditioning, air blasting or sandblasting of the tooth surface, and use of laser for enamel etching.

  Acids for Etching Top

Phosphoric acid

Chow and brown reported that a concentration <27% produces monocalcium phosphate calcium and a concentration of more than 27% produces dihydrate phosphate calcium. The former was readily soluble and was expected to be completely washed away in clinical situations and the latter was found to be insoluble.[2] With an increase in the amount of H3PO4, the amount of calcium also increased reaching a concentration of maximum with 40%. Further increase in the concentration of acid resulted in a decrease in the total calcium dissolved. The amounts of subsurface calcium dissolved with the use of phosphoric acid concentrations ranging from 10% to 60% were not significantly different.[3]

Self-etching primer

To minimize the complexity of various steps and to reduce the clinical time, self-etching primers (SEPs) were introduced. They combine conditioning and priming into a single treatment step. The active ingredient used in SEPs is methacrylated phosphoric acid ester, which etches and primes the enamel simultaneously. Calcium is dissolved and removed from hydroxyapatite by the phosphate group of the methacrylated phosphoric acid ester. However, rather than being rinsed away, calcium forms a complex with the phosphate group and becomes incorporated into the network when the primer polymerizes.[4] The demand for reduced technique sensitivity, shorter clinical application time, and less incidence of postoperative sensitivity have made self-etch systems a more accepted approach.[5]

Fluoridated phosphoric acid

The use of mixed phosphoric acid 37% with NaF gel 1.23% for 30 s (0.863%F-) has proven to be useful in preventing demineralization or caries under and around orthodontic brackets bonded to enamel. Mixed phosphoric acid 25% with NaF% gel (0.694% F-) results in reducing shear bond strength it may have a better clinical application in the prevention of demineralization by minimizing enamel loss and fluoride effect.[6],[7] Other acids used are 50% H3PO4 attenuated with 7% zinc oxide and 50% citric acid.[8]

Crystal growth theory

The technique of crystal growth was demonstrated by Smith and Cartz. Crystal bonding solutions are based on a mixture of polyacrylic acid and residual sulfate ions. The action of ionic salts such as sodium sulfate in crystal bonding solutions has been investigated. Since then, several different ionic solutions produce crystal growth.[9]


Phosphoric acid etching is a good method of preparing tooth enamel for bonding resins and orthodontic attachments. However, a demerit is a decalcification, which leaves the enamel susceptible to caries attack, especially under orthodontic attachments. Lasers have therefore been introduced in dentistry, surfaces etched with erbium, chromium-doped: Yttrium scandium-gallium-garnet (Er, Cr: YSGG) lasers show microirregularities with no smear layer. Laser etching inhibits caries, which is also of great importance in orthodontics. The results show that enamel etching with a 1.5-W laser-produced adequate bond strength and could be a viable alternative to other methods.[10] The mean shear bond strength and enamel surface etching obtained with Er, Cr: YSGG laser (operated at 1 W or 2 W for 15 s) is comparable to acid etching.[11]

Air abrasion/sandblasting

Air abrasion was first described by Black (1945) as a method of preparing cavity forms. Several studies were carried out to analyze the effects on the enamel bond strength of acid etch alone versus a combination of air abrasion and acid etching. Listed in decreasing order, was to use 100 mm aluminum oxide air abrasion treatment, followed by 50 mm aluminum oxide air abrasion treatment, followed by 25 mm aluminum oxide air abrasion treatment, or no air abrasion treatment.[12] Both the use of conventional acid etching and pumicing with conventional acid etching produced equivalent tensile strength values. Sandblasting enamel alone yielded the lowest bracket strength. The pattern of debond failure indicated that all specimens that were sandblasted alone debonded totally at the tooth/resin interface. Air abrasion is used to clean or roughen surfaces in various procedures of dentistry. As a result, attempts were made to use the procedure to condition the enamel surface for bonding procedures. Because the concept of sandblasting the enamel surface is unique, a conservative approach (only 2–3 s) was taken to determine whether sandblasting is a viable alternative to acid etching.[13]

  Special Considerations Top


The prevalence of enamel fluorosis is on the increase in many parts of the world. Diagnosis of fluorosis must be made before treatment according to Thylstrup and Fejerskov index (TFI). The enamel with more fluorosis required more etching time which showed little correlation between the mean depth of etch. The depth of etch of fluorosed enamel with TFI_1–3 is not significantly different from that in nonfluorosed teeth and generally increases with etching time. When enamel with TFI_4 is etched for 15 s, the depth of etch is extremely shallow, but at an etching time of 30 s, the depth of etch is not significantly different from that obtained for teeth with TFI_1–3. In contrast, the depth of etch obtained for enamel with TFI_5 and 6 correlates poorly with the etching time.[14]

Etching of young versus old enamel

Wear and maturation of the enamel on old permanent teeth do not seem to have a negative influence on the result of etching, as has been suggested. The results indicate that 60 s of etching provides better results than 15 s. The retentive conditions were better on the old teeth after 60 s of acid application than those on the young permanent teeth.[15]

Porcelain surface conditioning

To achieve bonding of orthodontic brackets to porcelain surfaces, it is necessary to change the inert characteristics of the surface to achieve clinically acceptable bond strength. This alteration is established by either increasing the roughness of the porcelain surface mechanically, for example, by either microetching or the use of strong etchants such as hydrofluoric acid (or both), together with a silane coupling agent. The most reliable procedure for bonding orthodontic brackets to porcelain surfaces is through either microetching with the use of hydrofluoric acid and a silane coupler or the use of the Clearfil self-etch primer/silane/adhesive.[5],[6],[7],[8],[9] Microetching and the use of hydrofluoric acid produce the greatest damage to the porcelain surface even after polishing when compared with the new self-etch/silane/adhesive combination.

  Enamel Hypoplasia Top

Molar incisor hypomineralization is a condition of systemic origin that is often associated with affected incisors and molars. When compared to normal enamel (NE), hypomineralized enamel (HE) exhibited a mean reduction of about 28% in its mineral content, 80% more carbonated apatite, and a 3–15-fold increase in its protein content. A systematic review on bonding to HE concluded that resin dental adhesives achieved an inferior bonding to HE when compared to NE. Furthermore, another review stated that enamel deproteinization with 5% sodium hypochlorite before the adhesive application procedure may enhance the bonding of resin dental adhesives to HE.[7],[8],[9],[10],[11],[12]

Etch‒bleach enamel

Intrinsic staining of HE defects manifests as a mottled white to variable degrees of yellow brown. Several treatment approaches have been proposed, that included bleaching to restorative techniques. Clinically, 1–2 applications of etchant ‒ 5% sodium hypochlorite is used for bleaching of HE lesions. Treatment using this approach has proven successful in removing yellow-brown discolorations from lesions in young permanent teeth.[3],[4],[5],[6],[7] Young permanent incisors with yellow-brown intrinsic discolorations can be often treated by a simple and conservative bleaching protocol using sodium hypochlorite.

  Conclusion Top

Various procedures in dentistry require prior etching due to the nonadhesive nature of the restorative materials. It is important to know the various techniques and concentration of acid that is required for different tooth types under variable oral conditions.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Sheridan JJ. Guidelines for contemporary air-rotor stripping. J Clin Orthod 2007;41:315-20.  Back to cited text no. 1
Bolton A. Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod 1958;28:113-30.  Back to cited text no. 2
Rossouw PE, Tortorella A. Enamel reduction procedures in orthodontic treatment. J Can Dent Assoc 2003;69:378-83.  Back to cited text no. 3
Zachrisson BU, Nyøygard L, Mobarak K. Dental health assessed more than 10 years after interproximal enamel reduction of mandibular anterior teeth. AJODO 2007;131:162-9.  Back to cited text no. 4
Zachrisson BU. Interdental papilla reconstruction in adult orthodontics. World J Orthod 2004;5:67-73.  Back to cited text no. 5
Lombardo L, Guarneri MP, D'Amico P, Molinari C, Meddis V, Carlucci A, et al. Orthofile(R): A new approach for mechanical interproximal reduction: A scanning electron micro- scopic enamel evaluation. J Orofac Orthop 2014;75:203-12.  Back to cited text no. 6
Lapenaite E, Lopatiene K. Interproximal enamel reduction as a part of orthodontic treatment. Stomatologija 2014;16:19-24.  Back to cited text no. 7
Livas C, Jongsma AC, Ren Y. Enamel reduction techniques in orthodontics: A literature review. Open Dent J 2013;7:146-51.  Back to cited text no. 8
Arman A, Cehreli SB, Ozel E, Arhun N, Cetinsahin A, Soyman M. Qualitative and quantitative evaluation of enamel after various stripping methods. AJODO 2006;130:131.  Back to cited text no. 9
Danesh G, Hellak A, Lippold C, Ziebura T, Schafer E. Enamel surfaces following interproximal reduction with different methods. Angle Orthod 2007;77:1004-10.  Back to cited text no. 10
Hudson AL. A study of the effects of mesiodistal reduction of mandibular anterior teeth. AJODO 1956;42:615-24.  Back to cited text no. 11
Stecksén-Blicks C, Renfors G, Oscarson ND, Bergstrand F, Twetman S. Caries-preventive effectiveness of a fluoride varnish: A randomized controlled trial in adolescents with fixed orthodontic appliances. Caries Res 2007;41:455-9.  Back to cited text no. 12
Kirschneck C, Christl JJ, Reicheneder C, Proff P. Efficacy of fluoride varnish for preventing white spot lesions and gingivitis during orthodontic treatment with fixed appliances – A prospective randomized controlled trial. Clin Oral Investig 2016;20:2371-8.  Back to cited text no. 13
Bonetti G, Zanarini M, Incerti Parenti S, Marchionni S, Checchi L. In vitro evaluation of casein phosphopeptide- amorphous calcium phosphate (CPP-ACP) effect on stripped enamel surfaces. A SEM investigation. J Dent 2009;37:228-32.  Back to cited text no. 14
Grippaudo C, Cancellieri D, Grecolini ME, Deli R. Comparison between different interdental stripping methods and evaluation of abrasive strips: SEM analysis. Prog Orthod 2010;11:127-37.  Back to cited text no. 15


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