==== Front BMC Oral Health BMC Oral Health BMC Oral Health 1472-6831 BioMed Central London 37393280 3103 10.1186/s12903-023-03103-x Research Shear bond strength of metallic brackets bonded to enamel pretreated with CPP-ACP: a systematic review and meta-analysis of in vitro studies Yacout Yomna M. yomna.yacout@alexu.edu.eg 1 Nabawy Yomna A. yomna.atef@aast.edu 2 El-Harouni Nadia M. 3 Yousry Tarek N. 3 1 grid.7155.6 0000 0001 2260 6941 Department of Orthodontics, Faculty of Dentistry, Alexandria University, Champollion St, Azarita, P. O. Box: 21521, Alexandria, Egypt 2 grid.442567.6 0000 0000 9015 5153 Department of Orthodontics, College of Dentistry El Alamein, Arab Academy for Science, Technology and Maritime Transport (AASTMT), El Alamein, Egypt 3 grid.7155.6 0000 0001 2260 6941 Department of Orthodontics, Faculty of Dentistry, Alexandria University, Alexandria, Egypt 1 7 2023 1 7 2023 2023 23 44019 12 2022 2 6 2023 © The Author(s) 2023 https://creativecommons.org/licenses/by/4.0/ Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Background Development of white spot lesions (WSLs) is common among orthodontic patients. Several measures have been introduced to prevent and remineralize the lesions. Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is used for both prevention and remineralization. The effect of its application before bonding is controversial. This systematic review was conducted to investigate the most up to date available literature regarding the effect of CPP-ACP enamel pre-treatment on shear bond strength (SBS) of metallic orthodontic brackets. Methods A search was conducted in electronic databases (MEDLINE (via PubMed), Scopus, Cochrane Library, Web of Science and Google scholar (grey literature)) up to March 29th, 2023. The inclusion criteria included in vitro studies comparing the SBS of metal orthodontic brackets following pre-treatment of enamel using CPP-ACP versus control. The exclusion criteria included study types other than in vitro studies, studies conducted on non-human enamel, or studies using CPP-ACP in combination with another intervention. The included studies were analysed by two reviewers, independently. The risk of bias assessment was done using a modified risk of bias tool. A Meta-analysis was performed. I2 values and Q-test were used for assessment of heterogeneity. Results were displayed in forest plots with a random-effects model. Standardized mean difference, standard error (SE) and 95% confidence intervals were calculated for all studies. Results The search resulted in 76 articles. After duplicate removal and assessment for eligibility, 15 studies were included in the review. High statistical heterogeneity was found among the included studies using I2 values and Q-Test (I2 = 95.147%; Q = 288.456; df = 14; P < 0.001). The overall effect of CPP-ACP pre-treatment on the SBS of metal orthodontic brackets was not significant (Mean difference = 1.163 MPa, SE = 0.757, 95% CI = -0.321, 2.648, p value = 0.125). The use of CPP-ACP for prevention of WSLs did not significantly affect the SBS of brackets (Standardized mean difference = 1.009, SE = 0.884, 95% CI = -0.723, 2.740, p value = 0.254). No significant change was found when CPP-ACP was used for remineralization of WSLs (Standardized mean difference = 1.501, SE = 1.087, 95% CI = -0.630, 3.632, p value = 0.167). Conclusions Within the limitations of the study, the evidence suggests that the use of CPP-ACP for either prevention or remineralization of WSLs before bonding does not affect the SBS of metal orthodontic brackets. Supplementary Information The online version contains supplementary material available at 10.1186/s12903-023-03103-x. Keywords Shear bond strength Casein phosphopeptide-amorphous calcium phosphate CPP-ACP Orthodontic brackets Alexandria UniversityOpen access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2023 ==== Body pmcBackground White spot lesions (WSLs) are a common risk during and after orthodontic treatment especially, in poor oral hygiene patients [1, 2]. These milky white opacities may appear around orthodontic brackets within only 4 weeks of starting treatment [3]. The presence of fixed orthodontic brackets and auxiliaries hampers the maintenance of good oral hygiene, thus resulting in increased food accumulation which increases the risk of WSLs development [2, 4]. In addition, the acid-etching procedure required for bonding orthodontic attachments removes 10–20 μm of the enamel surface, which may increase the risk of enamel demineralization [5]. Furthermore, the increase in the levels of acidogenic bacteria, such as Streptococcus mutans and lactobacilli, in orthodontic patients after placement of fixed orthodontic appliances lowers the pH of the oral cavity thus favoring enamel demineralization [6, 7]. WSLs may progress into cavitation thus affecting aesthetics and reducing patient satisfaction with the final orthodontic treatment results [8]. Prevention of WSLs starts by educating and motivating the patient to maintain good oral hygiene and consume non cariogenic diet [9]. However, additional preventive measures are often needed to reduce the risk of enamel demineralization in high-risk patients, thus reducing the risk of WSLs formation [10]. One of these measures is the use of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) [10]. CPP-ACP is a milk-derived bioactive peptide that is available in different forms such as topical dental cream [11], mouth rinse [12], chewing gum [12, 13], and lozenges [14], and it has shown an efficient preventive and remineralizing potential. The suggested anticariogenic mechanism of the CPP-ACP is that it can stabilize calcium and phosphate and preserve them in a soluble form, called amorphous calcium phosphate, providing a reservoir [15]. CPP-ACP can also bind to enamel surface, dental pellicle and dental plaque, thus maintaining a state of calcium and phosphate supersaturation in a close proximity to the tooth structure and a pH buffering action in dental plaque, hence decreasing enamel demineralization and enhancing remineralization [16]. The preservation of sound enamel surface, on the one hand, is important during and after orthodontic treatment. On the other hand, the preventive measures used should not negatively affect the bond strength of the orthodontic brackets. Ideally, the orthodontic bracket shear bond strength (SBS) should range between 5.9 and 7.8 Megapascals (MPa) [17] to withstand the orthodontic and masticatory forces without failure throughout the treatment period and to allow debonding at the conclusion of the treatment without causing enamel damage [18]. Multiple studies have been conducted to evaluate the effects of CPP-ACP pre-treatment on the SBS of orthodontic brackets, however, the results of these studies were controversial. Systematically reviewing the published literature and statistically pooling the data obtained from previous research allows analysis of a larger sample, thus allows the clinician to make evidence-based decisions [19]. Hence, the aim of this systematic review and meta-analysis was to investigate the most up to date available literature regarding the effect of CPP-ACP enamel pre-treatment on the SBS of metallic orthodontic brackets. The review aims to answer the question whether applying CPP-ACP on the enamel for the prevention or treatment of WSLs before bonding affects the SBS of metallic orthodontic brackets. Methods The review and analysis were conducted and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [20]. Eligibility criteria The inclusion criteria were experimental studies conducted on extracted permanent human teeth. The characteristics of the included studies based on PICO [21] were:Population (P): Enamel of extracted permanent human teeth. Intervention (I): Enamel treatment with CPP-ACP before bonding metallic orthodontic brackets. Comparison (C): No enamel pretreatment before bonding metallic orthodontic brackets or treatment with another material. Outcome (O): Shear bond strength. The exclusion criteria included case reports, letters to editor, commentaries, editorials, animal studies, in vivo studies, literature reviews, systematic reviews, and meta-analyses. In addition, studies conducted on non-human enamel, or studies that used CPP-ACP in combination with another intervention were excluded. Information sources and search strategy The detailed search strategy shown in Table 1, was developed with no language, country or publication date restrictions. Five different electronic databases were screened: MEDLINE (via PubMed), Scopus, Cochrane library, Web of Science and Google scholar (Gray literature). To find research that may have been overlooked in the electronic database search, the reference lists of relevant papers were hand-searched. In addition, "Citation Networks" of relevant papers in Web of Science database were checked. Two independent reviewers (YN and YY) searched the literature to find the relevant published studies from the inception of each database up to March 29th, 2023.Table 1 Literature search conducted to identify studies. (Last search date March 29th, 2023) Database Search Search strategy Hits MEDLINE (via PubMed) #1 "shear strength"[MeSH Terms] OR "shear strength"[Title/Abstract] OR "bond strength"[Title/Abstract] OR "shear bond strength"[Title/Abstract] 21,679 #2 caseins[MeSH Terms] OR "casein phosphopeptide amorphous calcium phosphate nanocomplex"[Supplementary Concept] OR "casein phosphopeptide amorphous calcium phosphate"[Title/Abstract] OR "cpp acp"[Title/Abstract] 17,173 #3 "orthodontic brackets"[MeSH Terms] OR "orthodontic bracket*"[Title/Abstract] OR "orthodontic brace*"[Title/Abstract] OR "metal bracket*"[Title/Abstract] OR "metal brace*"[Title/Abstract] OR "metallic bracket*"[Title/Abstract] 5,521 #4 #1 AND #2 AND #3 24 Scopus #1 TITLE-ABS-KEY (“shear strength” OR “shear bond strength” OR “bond strength”) 130,011 #2 TITLE-ABS-KEY (“casein phosphopeptide-amorphous calcium phosphate” OR “CPP-ACP”) 820 #3 TITLE-ABS-KEY ("orthodontic brackets" OR “orthodontic braces” OR “metal* bracket*” OR “metal* brace*”) 6,117 #4 #1 AND #2 AND #3 22 Cochrane #1 [mh "Shear Strength"] OR “shear strength”:ti,ab,kw OR “bond strength”:ti,ab,kw OR “shear bond strength”:ti,ab,kw 1,149 #2 [mh "caseins"] OR “casein phosphopeptide-amorphous calcium phosphate”:ti,ab,kw OR “CPP-ACP”:ti,ab,kw 623 #3 [mh "Orthodontic Brackets"] OR orthodontic NEXT bracket*:ti,ab,kw OR orthodontic NEXT brace*:ti,ab,kw OR metal* NEXT bracket*:ti,ab,kw OR metal* NEXT brace*:ti,ab,kw 981 #4 #1 AND #2 AND #3 1 Web Of Science #1 (((((TI=("shear strength")) OR TI=("shear bond strength")) OR AB=("shear strength")) OR AB=("shear bond strength")) OR AK=("shear strength")) OR AK=("shear bond strength") 47,946 #2 (((((TI=("casein phosphopeptide-amorphous calcium phosphate")) OR TI=("CPP-ACP")) OR AB=("casein phosphopeptide-amorphous calcium phosphate ")) OR AB=("CPP-ACP")) OR AK=("casein phosphopeptide-amorphous calcium phosphate")) OR AK=("CPP-ACP") 549 #3 (((((((((((TI=("orthodontic bracket*")) OR TI=("orthodontic brace*")) OR AB=(" orthodontic bracket*")) OR AB=("orthodontic brace*")) OR AK=(" orthodontic bracket*”)) OR AK=("orthodontic brace*")) OR TI=("metal* bracket*")) OR TI=("metal* brace*")) OR AB=("metal* bracket*")) OR AB=("metal* brace*")) OR AK=("metal* bracket*")) OR AK=("metal* brace*") 2,433 #4 #1 AND #2 AND #3 22 Google scholar https://scholar.google.com.eg/ allintitle: ("shear strength" OR "shear bond strength") AND ("casein phosphopeptide-amorphous calcium phosphate" OR "CPP-ACP") AND ("orthodontic bracket" OR "metal bracket" OR "orthodontic brackets" OR "metal brackets") 7 Study selection The relevant articles were imported into EndNote X9™ reference manager (Clarivate™, Philadelphia, PA). Duplicates were removed using EndNote’s “Find Duplicates” function and any missed duplicates were removed manually. The titles and abstracts of the articles were then reviewed by two authors (YN and YY) independently to exclude any article that does not follow the inclusion criteria. The full text of potentially eligible articles was assessed for eligibility by the same two reviewers. Any disagreement between the two reviewers was solved by discussion. If the disagreement regarding the eligibility of the studies persisted, a third reviewer opinion (NE) was obtained. Data extraction The data were collected from eligible articles by one author (YN) and revised by another (YY). A data extraction form was created using Microsoft 365® Excel® software (Microsoft Corporation, Redmond, WA). The form included the following information: authors’ names, publication year, total sample size, number of groups, number of samples per group, condition of enamel before bonding, protocol of CPP-ACP application, duration of CPP-ACP application, number of CPP-ACP applications, protocol implemented in control groups, and mean and standard deviation (SD) of SBS in MPa. If any relevant data was missing from a paper, the corresponding author of said paper was contacted by e-mail. If no response was obtained within 2 weeks, another e-mail was sent. Risk of bias assessment Two reviewers (YN and TY) performed the risk of bias assessment independently using a modification of the Risk of Bias tool suggested by Sarkis-Onofre et al. [22]. The risk of bias was assessed based on the description of the following parameters in the article: 1- description of sample-size calculation, 2- randomization of teeth, 3- presence of a control group, 4- using teeth free of caries or restorations, 5- description of sample preparation (handling, cleaning and storage of the teeth), 6- using the materials according to the manufacturer’s instructions, 7- blinding of the outcome assessor, 8- bonding procedure executed by a one investigator. If the parameter was reported by the authors, the specific parameter was marked as “Yes”. If it was not reported or no information could be found, it was marked as “No”. Articles reporting three or less parameters were considered to have a high risk of bias, four or five parameters a medium risk of bias, and six or more parameters a low risk of bias. If no consensus regarding the risk of bias of any article could be reached between the two reviewers (YN and TY), a third reviewer (NE) was consulted. Synthesis of results Meta-analysis was performed using OpenMeta[Analyst] software [23]. For assessment of heterogeneity of the studies I2 values and Q-Test were used. The I2 Index measures the percentage of variation across studies and represents the heterogeneity (25% corresponds to low heterogeneity, 50% to moderate heterogeneity, and 75% to high heterogeneity). Forest plots with a random-effects model were used in the current study due to the high heterogeneity found among the studies. Standardized mean difference, standard error (SE) and 95% confidence interval (CI) were calculated for all studies. Results Study selection The process of study selection is shown in Fig. 1. Screening the databases using the search strategy identified 76 publications: 24 from MEDLINE, 22 from Scopus, 1 from Cochrane library, 22 from Web of Science and 7 from grey literature. After duplicates exclusion 27 articles remained. Four articles were excluded based on their title and abstract. The full texts of the 23 potentially eligible articles were analysed, out of which, 8 full text articles were excluded because CPP-ACP was combined with bleaching[24] or combined with fluoride [25–31]. A total of 15 papers were deemed eligible for the systematic review[32–46].Fig. 1 Flowchart showing the study selection process based on the PRISMA statement Study characteristics The characteristics of the 15 studies included in the systematic review are summarized in table 2. Of the 15 studies, 6 studies evaluated the effect of CPP-ACP on the SBS when used as a preventive measure on sound enamel before bonding brackets [40–45]. In addition, 8 studies evaluated the effect of CPP-ACP on the SBS of brackets when used as a remineralizing agent on demineralized enamel [32, 33, 35–39, 46]. One study reported the SBS of brackets after using CPP-ACP for both prevention and remineralization of WSLs [34]. The SBS of 365 tooth specimens in the test groups (treated with CPP-ACP) was compared to the SBS of 1014 tooth specimens in the control groups (No pre-treatment or treatment with a different material). Separate teeth were used as controls, and none of the studies used different surfaces of the same tooth as both test and control. Twelve studies used CPP-ACP in the form of a paste [32–36, 38–41, 43, 44, 46], while the remaining three studies used a solution of CPP-ACP diluted using artificial saliva [42, 45] or deionized water [37].Table 2 Summary of the characteristics of the 15 studies included in the systematic review Authors names Year Total sample size Groups Test group sample size Enamel condition in test group CPP- ACP protocol of application Duration of application Number of applications SBS (MPa) Control group sample size Enamel condition in control group Control groups protocol SBS (MPa) Mean SD Mean SD Xiaojun et al . 2009 72 4 18 Sound Solution (Tooth Mousse+ artificial saliva, 1:10) before phosphoric acid etching + light cure adhesive (Blugloo) 60 mins 5 20.89 4.93 18 Sound No pretreatment + Artificial saliva + phosphoric acid etching + light cure adhesive (Blugloo) 17.12 5.57 18 Sound Solution (Tooth Mousse+ artificial saliva, 1:10) before phosphoric acid etching + chemical cure adhesive (Unite Bonding Adhesive) 60 mins 5 27.98 9.16 18 Sound No pretreatment + Artificial saliva + phosphoric acid etching + chemical cured adhesive (Unite Bonding Adhesive) 26.38 7.58 Tabrizi and Cakirer 2011 80 4 20 Sound Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Light Bond) 3 mins NR 22.57 4.32 20 Sound No pretreatment +phosphoric acid etching + light cure adhesive (Light Bond) 21.02 5.24 20 Sound 5% NaF varnish (Duraphat) +phosphoric acid etching + light cure adhesive (Light Bond) 14.02 4.64 20 Sound 5% NaF varnish (Duraphat) + CPP-ACP (GC Tooth Moose) + phosphoric acid etching + light cure adhesive (Light Bond) 21.69 3.57 Uysal et al 2011 80 4 20 Demineralized Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 5 mins 10 22.0 3.6 20 Sound No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 24.1 4.0 20 Demineralized No pretreatment + Artificial saliva + phosphoric acid etching + light cure adhesive (Transbond XT) 6.6 3.9 20 Demineralized Flouride gel (Fluoridin N5) + phosphoric acid etching + light cure adhesive (Transbond XT) 17.1 2.9 Baysal andUysal 2012 100 5 20 Demineralized Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 5 mins 10 22.0 3.6 20 Sound No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) 24.1 4.1 20 Demineralized No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) 6.6 3.9 20 Demineralized Microabrasion + phosphoric acid etching + light cure adhesive (Transbond XT) 16.2 1.5 20 Demineralized Microabrasion + CPP-ACP Gel (GC Tooth Mousse) + phosphoric acid etching + light cure adhesive (Transbond XT) 24.3 1.9 Çehreli et al 2012 66 6 10 Sound Paste (MI Paste) before phosphoric acid etching + light cure adhesive (Transbond XT) NR NR 5.74 1.67 10 Sound No pretreatment+ phosphoric acid etching + light cure adhesive (Transbond XT) 8.88 1.61 10 Sound Paste (MI Paste) before self etching adhesive (Transbond Plus) NR NR 7.33 2.2 10 Sound No pretreatment + self etching adhesive (Transbond Plus) 9.08 1.45 10 Sound CPP-ACPF (MI Paste plus) + phosphoric acid etching + light cure adhesive (Transbond XT) 8.82 1.54 10 Sound CPP-ACPF (MI Paste plus) + self etching adhesive (Transbond Plus) 8.11 1.59 Park et al 2013 60 4 15 Sound Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 3 mins 28 18.48 2.19 15 Sound No pretreatment+ phosphoric acid etching + light cure adhesive (Transbond XT) 18.66 2.31 Sound Paste (GC Tooth Mousse) before self etching primer (Transbond Plus) + light cure adhesive (Transbond XT) 3 mins 28 15.51 1.71 15 Sound No pretreatment + self etching primer (Transbond Plus) + light cure adhesive (Transbond XT) 15.75 1.77 Al-Kawari and Al-Jobair 2014 112 7 16 Sound Paste ( MI Paste ) before phosphoric acid etching + light cure adhesive (Transbond XT) 33 mins 1 13.37 4.79 16 Sound No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 11.25 4.27 16 Sound Paste ( MI Paste ) after phosphoric acid etching + light cure adhesive (Transbond XT) 33 mins 1 15.65 5.87 16 Sound CPP-ACPF (MI paste plus) before phosphoric acid etching + light cure adhesive (Transbond XT) 11.05 4.85 16 Sound CPP-ACPF (MI paste plus) after phosphoric acid etching + light cure adhesive (Transbond XT) 16.35 3.81 16 Sound 5% NaF varnish (Fluoraphat) before phosphoric acid etching + light cure adhesive (Transbond XT) 8.86 4.35 16 Sound 5% NaF varnish (Fluoraphat) after phosphoric acid etching + light cure adhesive (Transbond XT) 12.56 3.74 Ladhe et al 2014 120 6 20 Sound Solution (GC Tooth Mousse+ artificial saliva, 1:10) before phosphoric acid etching + light cure adhesive (Transbond XT) 60 mins 5 9.76 3.33 20 Sound No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 10.67 4.6 20 Sound Solution (GC Tooth Mousse+ artificial saliva, 1:10) before phosphoric acid etching + chemical cured adhesive (Unite Bonding Adhesive) 60 mins 5 7.52 1.51 20 Sound No pretreatment + phosphoric acid etching + chemical cured adhesive (Unite Bonding Adhesive) 10.12 4.04 20 Sound CPP-ACPF (GC Tooth Mousse Plus) + phosphoric acid etching + light cure adhesive (Transbond XT) 12.07 2.96 20 Sound CPP-ACPF (GC Tooth Mousse Plus) + phosphoric acid etching + chemical cured adhesive (Unite Bonding Adhesive) 7.36 2.54 Baka et al 2016 140 7 20 Demineralized Paste (GC Tooth Mousse) before self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 5 mins 10 9.04 2.64 20 Sound No pretreatment + Self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 10.21 2.26 20 Demineralized No pretreatment+ Self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 2.26 1.46 20 Demineralized Fluoride gel (Bifluorid 12) + self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 7.92 2.12 20 Demineralized Microabrasion (Cuxhaven) + self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 6.18 1.65 20 Demineralized Microabrasion (Opalstrue) + self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 6.54 1.83 20 Demineralized Resin infilteration (Icon) + self etching primer (Transbond Plus)+ light cure adhesive (Transbond XT) 10.06 2.08 Velİ et al 2016 140 7 20 Demineralized Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 5 mins 10 16.2 1.4 Sound No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 18.8 2 Demineralized No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 6.8 1.1 Demineralized Fluoride varnish (Bifluoride 12) + phosphoric acid etching + light cure adhesive (Transbond XT) 11.5 1.2 Demineralized Microabrasion (prepared mixture) + phosphoric acid etching + light cure adhesive (Transbond XT) 12.6 1.5 Demineralized Microabrasion (Opalustre) + phosphoric acid etching + light cure adhesive (Transbond XT) 14.8 1.1 Demineralized Resin infilteration (Icon) + phosphoric acid etching + light cure adhesive (Transbond XT) 19.1 1.4 Farhadian et al 2017 80 5 16 Demineralized Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 7 mins 20 12.53 7.16 16 Demineralized No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 9.53 6.0 16 Demineralized CO2 laser irradiation + phosphoric acid etching + light cure adhesive (Transbond XT) 20.62 8.64 16 Demineralized CO2 laser irradiation before CPP-ACP (GC Tooth Mousse) + phosphoric acid etching + light cure adhesive (Transbond XT) 9.04 4.46 16 Demineralized CO2 laser irradiation through CPP-ACP (GC Tooth Mousse) + phosphoric acid etching + light cure adhesive (Transbond XT) 9.96 4.54 Gulec and Goymen 2019 80 4 20 Demineralized Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 5 mins 28 4.8 1.97 20 Sound No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) 16.83 4.75 20 Demineralized No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) 13.07 3.73 20 Demineralized Resin infilteration (Icon) + phosphoric acid etching + light cure adhesive (Transbond XT) 4.36 2.24 Topsakal and Amuk 2019 150 10 15 Demineralized Paste (GC Tooth Mousse) after phosphoric acid etching + light cure adhesive (Transbond XT) 3 min NR 18.35 5.87 15 Sound No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 17.96 5.26 15 Demineralized Paste (GC Tooth Mousse) after phosphoric acid etching + resin-modified GIC (Fuji Ortho LC) 3 min NR 11.74 4.94 15 Sound No pretreatment + resin-modified GIC (Fuji Ortho LC) 10.86 5.42 15 Demineralized No pretreatment + phosphoric acid etching + light cure adhesive (Transbond XT) 16.37 6.78 15 Demineralized No pretreatment + resin-modified GIC (Fuji Ortho LC) 10.87 6.88 15 Demineralized 5% NaF varnish (Duraphat) + phosphoric acid etching + light cure adhesive (Transbond XT) 22.99 5.16 15 Demineralized 5% NaF varnish (Duraphat) + resin-modified GIC (Fuji Ortho LC) 130.07 5.14 15 Demineralized Fluoride gel (Gelato APF gel) + phosphoric acid etching + light cure adhesive (Transbond XT) 15.66 5.37 15 Demineralized Fluoride gel (Gelato APF gel)+ resin-modified GIC (Fuji Ortho LC) 11.67 5.61 Uy et al 2019 80 10 8 Demineralized Solution (1 gm GC Tooth Mousse + 4 ml deionized water) before phosphoric acid etching + light cure adhesive (Transbond XT) + thermocycling 24 hours 30 8.84 0.94 8 Sound No pretreatment + Light cure adhesive (Transbond XT) + thermocycling 9.64 0.45 8 Demineralized Solution (1 gm GC Tooth Mousse + 4 ml deionized water) before phosphoric acid etching + light cure adhesive (Transbond XT) No thermocycling 24 hours 30 9.04 2.1 8 Demineralized No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) + thermocycling 3.29 0.28 8 Demineralized 0.21% NaF (ClinPro Tooth Crème) + phosphoric acid etching + light cure adhesive (Transbond XT) + thermocycling 8.09 1.37 8 Demineralized CPP ACPF (GC Tooth mousse plus) phosphoric acid etching + light cure adhesive (Transbond XT) + thermocycling 9.73 0.61 8 Sound No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) No thermocycling 11.65 1.15 8 Demineralized No pretreatment + Phosphoric acid etching + light cure adhesive (Transbond XT) No thermocycling 4.47 0.83 8 Demineralized 0.21% NaF (ClinPro Tooth Crème) phosphoric acid etching + light cure adhesive (Transbond XT) No thermocycling 9.64 1.14 8 Demineralized CPP ACPF (GC Tooth mousse plus) phosphoric acid etching + light cure adhesive (Transbond XT) No thermocycling 11.73 1.07 Daneshkazemi et al 2021 160 8 20 Sound Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 5 mins 5 13.69 4.25 20 Sound No pretreatment + light cure adhesive (Transbond XT) 12.82 2.73 20 Demineralized Paste (GC Tooth Mousse) before phosphoric acid etching + light cure adhesive (Transbond XT) 5 mins 5 12.39 2.52 20 Demineralized No pretreatment + light cure adhesive (Transbond XT) 3.51 1.37 20 Sound 5 % NaF varnish (FlouroDose) + light cure adhesive (Transbond XT) 9.97 3.03 20 Sound Resin infilteration (Icon) + light cure adhesive (Transbond XT) 13.73 2.19 20 Demineralized 5 % NaF varnish (FlouroDose) + light cure adhesive (Transbond XT) 8.34 1.66 20 Demineralized Resin infilteration (Icon) + light cure adhesive (Transbond XT) 12.34 4.47 CPP-ACP Casein phosphopeptide amorphous calcium phosphate, CPP-ACPF Casein phosphopeptide amorphous calcium phosphate fluoride, MPa Megapascals, NaF Sodium Fluoride, NR Not reported, SBS Shear bond strength, SD Standard Deviation Risk of bias within studies The risk of bias assessment for each of the included studies is presented in table 3. Seven of the studies showed a low overall risk of bias [32–36, 38, 39], and 7 studies showed a medium risk [37, 40, 41, 43–46]. Only one study [42] was rated as having a high overall risk of bias. All the 15 studies [32–46] used teeth free of caries and restorations, reported randomization of the teeth to the study groups, and compared the test groups to control groups. All the studies rated as having a low risk of bias reported sample size calculation and described the procedure of sample preparation [32–36, 38, 39]. Only 7 of the studies used the CPP-ACP according to the manufacturer’s instructions [32–35, 38, 39, 43]. None of the studies reported blinding of the outcome assessor, and only one study mentioned that the bonding procedure was performed by the same investigator [36].Table 3 Risk of bias assessment of the included studies Authors Year Description of sample-size calculation Teeth randomization Presence of a control group Using sound teeth Description of sample preparation Using the materials according to the manufacturer’s instructions Blinding of the outcome assessor Bonding procedure executed by one investigator Risk assesment rank Xiaojun et al 2009 no yes yes yes yes no no no medium Tabrizi and Cakirer 2011 no yes yes yes yes no no no medium Uysal et al 2011 yes yes yes yes yes yes no no low Baysal and Uysal 2012 yes yes yes yes yes yes no no low Çehreli et al 2012 no yes yes yes yes no no no medium Park et al 2013 no yes yes yes yes yes no no medium Al-Kawari and Al-Jobair 2014 no yes yes yes yes no no no medium Ladhe et al 2014 no yes yes yes no no no no high Baka et al 2016 yes yes yes yes yes yes no no low Velİ et al 2016 yes yes yes yes yes yes no no low Farhadian et al 2017 no yes yes yes yes no no no medium Gulec and Goymen 2019 yes yes yes yes yes yes no no low Topsakal and Amuk 2019 yes yes yes yes yes no no yes low Uy et al 2019 no yes yes yes yes no no no medium Daneshkazemi et al 2021 yes yes yes yes yes yes no no low Results of individual studies and Synthesis of results The SBS was the outcome evaluated in all the included studies. A summary of the findings is presented in table 2. The use of CPP-ACP prior to bonding orthodontic brackets resulted in conflicting results. The effect estimates and confidence intervals for each study are shown in Fig. 2. The overall effect of CPP-ACP on the SBS of metal orthodontic brackets was not significant with a mean difference of 1.163 MPa (SE = 0.757, 95% CI = -0.321, 2.648, p value = 0.125). Subgroup analysis showed that the use of CPP-ACP for prevention of WSLs before bonding did not significantly affect SBS of brackets as shown in Fig. 3 (Standardized mean difference = 1.009, SE = 0.884, 95% CI = -0.723, 2.740, p value = 0.254). Likewise, no significant change was found when CPP-ACP was used for remineralization of WSLs as shown in Fig. 4 (Standardized mean difference = 1.501, SE = 1.087, 95% CI = -0.630, 3.632, p value = 0.167).Fig. 2 Overall forest plot comparing the reviewed studies based on standardized mean difference using a random-effects model Fig. 3 Forest plot comparing the studies using CPP-ACP for prevention of WSLs Fig. 4 Forest plot comparing the studies using CPP-ACP for remineralization of WSLs Risk of bias across studies Evidence of high heterogeneity among the included studies was detected using I2 values and Q-Test (I2 = 95.147%, Q = 288.456; df = 14; P < 0.001). Similarly, significant heterogeneity was observed when the use of CPP-ACP for prevention and remineralization was asssessed separately (Prevention: I2 = 89.736%; Q = 58.456; df = 6; P < 0.001, Remineralization: I2 = 96.278%; Q = 214.961; df = 8; P < 0.001). Discussion The risk of development of WSLs during and after fixed orthodontic treatment has increased the demand for better preventive and remineralization methods. One such method is the use of CPP-ACP which can bind to the tooth surface, soft tissues and to the bacteria in the dental pellicle and plaque [15, 16]. The anti-carcinogenicity of CPP-ACP may be explained by its ability to provide a calcium reservoir creating a supersaturation state that enhances remineralization and decreases demineralization [15]. The use of CPP-ACP not only favours enamel remineralization and decrease demineralization but it may also affect the bacterial microflora [47], and result in a delay in the formation of dental biofilm [48]. The exact mechanism through which CCP-ACP affects the bacteria is uncertain but the existing evidence showed that CPP-ACP could inhibit bacterial adhesion, provide a buffering effect, and produce biofilm disruption and bacteriostatic/bactericidal effects [47]. The effect of CPP-ACP enamel pre-treatment on SBS of orthodontic brackets is debatable. Thus, this systematic review and meta-analysis was conducted to review the available literature regarding the effect of CPP-ACP enamel pre-treatment, as a preventive or remineralization method, on the SBS of metallic orthodontic brackets. Only studies performed on human enamel were included in the current review. Studies performed on bovine teeth were not included because bovine and human enamel yield significantly different SBS results due to the differences in their structural compositions[49, 50]. Screening the literature revealed 15 eligible publications [32–46]. The papers were analysed and divided according to the use of CPP-ACP into two subgroups: prevention and remineralization. Statistical analysis was conducted to compare all the eligible articles as well as each subgroup independently. Forest plots with a random-effects model were used in the current study due to the high statistical heterogeneity found among the studies. The risk of bias of the individual studies was assessed using a modified version of the Risk of Bias tool suggested by Sarkis-Onofre et al. [22]. A recent systematic review that investigated the different tools used for quality assessment in systematic reviews of in vitro studies has highlighted the lack of a standard assessment tool [51]. The most commonly used tool was the one used in the current study [51]; however, it was modified to suit the requirements of the current investigation. Based on the risk of bias assessment, only one study was ranked as having a high risk of bias mainly due to lack of blinding of the outcome assessor, lack of description of sample size calculations or sample preparation, not using CPP-ACP according to the manufacturer’s instructions, and not reporting whether the bonding procedure was executed by one investigator. Seven of the studies were ranked as low risk as they fulfilled 6 or more parameters. All the low-risk studies described sample-size calculation, teeth randomization, and sample preparation, had a control group, and used sound teeth at the start of the study. According to the current meta-analysis, the use of CPP-ACP, for either prevention or remineralization of WSLs, did not significantly affect the SBS of metal orthodontic brackets. Nevertheless, when CPP-ACP was used for remineralization of WSLs, the effect estimates of the majority of the included studies were positive indicating higher SBS compared to the control [32–34, 36–39, 46]. Only one study[35] was an outlier which showed a negative effect estimate. The increase in SBS when CPP-ACP was applied to demineralized enamel may be related to the ability of CPP-ACP to remineralize the subsurface lesions which increases the mineral content of the enamel, and consequently increases the bond strength(34). On the other hand, when CPP-ACP was used for prevention of WSLs the results were controversial; with four studies [34, 40, 44, 45] demonstrating positive standardized mean difference, and three studies [41–43] demonstrating negative standardized mean difference. The SBS values reported in the 15 studies included in the current meta-analysis, following enamel pre-treatment using CPP-ACP, ranged between 4.8 MPa [35] and 27.98 MPa [45]. Clinically satisfactory orthodontic bonding has been previously reported with in vitro bond strength of 4.9 MPa [17], thus the minimum value reported by Gulec and Goymen [35], following pre-treatment of demineralized enamel using CPP-ACP, lies within the clinically accepted range of bond strength. The wide range of reported SBS values may be explained by the inconsistency in the application protocol of CPP-ACP among the included studies. The duration of application of CPP-ACP in the form of a paste ranged between 3 min [36, 43, 44] and 33 min [40]. Other studies applied CPP-ACP in the form of a solution for 60 min [42, 45] or 30 days [37]. Several of the reviewed studies did not fully disclose the application parameters such as the duration and number of applications [36, 41, 44]. In addition, the sequence of application of CPP-ACP relative to the acid-etching procedure may have affected the SBS values. Although most of the studies included in the current review applied CPP-ACP before etching the enamel surface[32–35, 37–39, 41–46], one study applied the remineralizing agent after etching [36], and another study applied the paste before etching in one group and after etching in another group [40]. Applying CPP-ACP before performing the etching procedure may result in an enamel surface that is more resistant to acid, which may consequently affect the bonding procedure and lower the SBS values [40]. Another factor that may affect the SBS of orthodontic brackets is the type of adhesive used for bonding and the duration of photopolymerization of light-cured adhesive, where a longer polymerization time increases the SBS[18]. Moreover, the storage medium used to store the teeth during the experimental procedures may affect the results. A previous systematic review has shown that the bond strength decreased by 10.7 MPa when the samples were stored in water [18]. Thermocycling was performed as an aging process in some of the included [32, 34, 39–41] studies to evaluate the long-term bonding effectiveness. According to a previous systematic review[52], thermocycling results in a reduction in the SBS of orthodontic brackets. Another consideration is the variable speed of the crosshead of the testing machine, where a faster speed results in a lower SBS of orthodontic brackets [53]. A speed of 0.5 mm/min [33, 38, 39, 43], 1 mm/ min [32, 34–37, 40, 41, 44–46], or 3 mm/min [42] was used in the different studies. The aforementioned disparate experimental conditions could help explain the statistically significant heterogenous results revealed during the analysis of the risk of bias across the studies. Limitations One of the limitations of the current systematic review is that all the included studies were in vitro studies which do not fully simulate the conditions of the oral environment. In addition, the experimental conditions varied widely across the studies, especially the application protocol of CPP-ACP and the sequence of application of CPP-ACP relative to the acid-etching procedure. Nevertheless, it was not practical to perform separate analysis for each protocol because the number of studies analysed in the subgroups would have been inadequate. Hence, the relevance of the results of the current study to the clinical situation should be interpreted with caution. Future research should aim at mimicking the oral environment following standard guidelines to verify the results of the current systematic review and obtain clinically relevant information[18]. Conclusions Within the limitations of the study, the evidence suggests that the use of CPP-ACP for either prevention or remineralization of WSLs before bonding does not affect the SBS of metal orthodontic brackets. Supplementary Information Additional file 1. Additional file 2. Abbreviations CI Confidence Interval CPP-ACP Casein phosphopeptide amorphous calcium phosphate MPa Megapascals PICO Population Intervention Comparison Outcome PRISMA Preferred Reporting Items for Systematic Reviews and Meta-Analyses SBS Shear bond strength SD Standard deviation SE Standard Error WSL White spot lesions Acknowledgements The authors wish to thank Assist. Lect. Nourhan M. Aly (Department of Paediatric Dentistry and Dental Public Health, Faculty of Dentistry, Alexandria University) for performing the statistical analysis, and Prof. Nasrin Farhadian (First author of reference #46) for providing the SBS data obtained in their study. Authors’ contributions All authors have read and approved the final manuscript. YN and YY screened the literature. YN extracted the data. YY revised the extracted data. TN and YY assessed the risk of bias. YN and YY wrote the manuscript and revised the statistics. NE discussed all the steps, was the third author opinion to resolve any disagreement during data extraction and revised the manuscript. Funding Open access funding provided by The Science, Technology & Innovation Funding Authority (STDF) in cooperation with The Egyptian Knowledge Bank (EKB). Availability of data and materials All the data analysed during the study are included in the article. Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests. Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. ==== Refs References 1. Tufekci E Dixon JS Gunsolley JC Lindauer SJ Prevalence of white spot lesions during orthodontic treatment with fixed appliances Angle Orthod 2011 81 2 206 210 10.2319/051710-262.1 21208070 2. Lucchese A Gherlone E Prevalence of white-spot lesions before and during orthodontic treatment with fixed appliances Eur J Orthod 2013 35 5 664 668 10.1093/ejo/cjs070 23045306 3. Øgaard B Arends J Orthodontic appliances and enamel demineralixation Part 1. Lesion development Am J Orthod Dentofacial Orthop. 1988 94 68 73 10.1016/0889-5406(88)90453-2 3164585 4. Gwinnett AJ Ceen RF Plaque distribution on bonded brackets: A scanning microscope study Am J Orthod 1979 75 6 667 677 10.1016/0002-9416(79)90098-8 377979 5. Powers J, Messersmith M. Enamel etching and bond strength. Orthodontic Materials: Scientific and Clinical Aspects. edn. Edited by Brantley W, Eliades T. New York. Thieme; 2001; 107-12. 6. Scheie AA Arneberg P Krogstad O Effect of orthodontic treatment on prevalence of Streptococcus mutans in plaque and saliva Scand J Dent Res 1984 92 3 211 217 6589736 7. Lundström F Krasse B Streptococcus mutans and lactobacilli frequency in orthodontic patients; the effect of chlorhexidine treatments Eur J Orthod 1987 9 2 109 116 10.1093/ejo/9.2.109 3472888 8. Øgaard B Prevalence of white spot lesions in 19-year-olds: A study on untreated and orthodontically treated persons 5 years after treatment Am J Orthod Dentofacial Orthop 1989 96 5 423 427 10.1016/0889-5406(89)90327-2 2816842 9. Lovrov S Hertrich K Hirschfelder U Enamel demineralization during fixed orthodontic treatment - Incidence and correlation to various oral-hygiene parameters J Orofac Orthop 2007 68 5 353 363 10.1007/s00056-007-0714-1 17882363 10. Sudjalim TR Woods MG Manton DJ Prevention of white spot lesions in orthodontic practice: a contemporary review Aust Dent J 2006 51 4 284 289 10.1111/j.1834-7819.2006.tb00445.x 17256301 11. Bailey DL Adams GG Tsao CE Hyslop A Escobar K Manton DJ Reynolds EC Morgan MV Regression of post-orthodontic lesions by a remineralizing cream J Dent Res 2009 88 12 1148 1153 10.1177/0022034509347168 19887683 12. Reynolds EC Cai F Shen P Walker GD Retention in plaque and remineralization of enamel lesions by various forms of calcium in a mouthrinse or sugar-free chewing gum J Dent Res 2003 82 3 206 211 10.1177/154405910308200311 12598550 13. Shen P Cai F Nowicki A Vincent J Reynolds EC Remineralization of enamel subsurface lesions by sugar-free chewing gum containing casein phosphopeptide-amorphous calcium phosphate J Dent Res 2001 80 12 2066 2070 10.1177/00220345010800120801 11808763 14. Cai F Shen P Morgan MV Reynolds EC Remineralization of enamel subsurface lesions in situ by sugar-free lozenges containing casein phosphopeptideamorphous calcium phosphate Aust Dent J 2003 48 4 240 243 10.1111/j.1834-7819.2003.tb00037.x 14738126 15. Reynolds EC Remineralization of enamel subsurface lesions by casein phosphopeptide-stabilized calcium phosphate solutions J Dent Res 1997 76 9 1587 1595 10.1177/00220345970760091101 9294493 16. Rose RK Binding characteristics of Streptococcus mutans for calcium and casein phosphopeptide Caries Res 2000 34 427 431 10.1159/000016618 11014910 17. Reynolds IR A review of direct orthodontic bonding Br J Orthod 2016 2 3 171 178 10.1080/0301228X.1975.11743666 18. Finnema KJ Özcan M Post WJ Ren Y Dijkstra PU In-vitro orthodontic bond strength testing: A systematic review and meta-analysis Am J Orthod Dentofacial Orthop 2010 137 5 615 622 10.1016/j.ajodo.2009.12.021 20451780 19. Liberati A Altman DG Tetzlaff J Mulrow C Gøtzsche PC Ioannidis JP Clarke M Devereaux PJ Kleijnen J Moher D The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate health care interventions: Explanation and elaboration J Clin Epidemiol 2009 62 10 e1 34 10.1016/j.jclinepi.2009.06.006 19631507 20. Page MJ McKenzie JE Bossuyt PM Boutron I Hoffmann TC Mulrow CD Shamseer L Tetzlaff JM Akl EA Brennan SE The PRISMA 2020 statement: an updated guideline for reporting systematic reviews BMJ 2021 372 n71 10.1136/bmj.n71 33782057 21. Page MJ Moher D Bossuyt PM Boutron I Hoffmann TC Mulrow CD Shamseer L Tetzlaff JM Akl EA Brennan SE PRISMA 2020 explanation and elaboration: updated guidance and exemplars for reporting systematic reviews BMJ 2021 372 n160 10.1136/bmj.n160 33781993 22. Sarkis-Onofre R Skupien JA Cenci MS Moraes RR Pereira-Cenci T The role of resin cement on bond strength of glass-fiber posts luted into root canals: A systematic review and meta-analysis of in vitro studies Oper Dent 2014 39 1 E31 44 10.2341/13-070-LIT 23937401 23. Wallace B Dahabreh I Trikalinos T Lau J Trow P Schmid C Closing the gap between methodologists and end-users: R as a computational back-end J Stat Softw 2012 49 1 5 10.18637/jss.v049.i05 24. Amuk NG Baysal A Üstün Y Kurt G The effects of different desensitizer agents on shear bond strength of orthodontic brackets after home bleaching: an in vitro study Eur Oral Res 2018 52 2 69 74 30775705 25. Akin M Baka ZM Ileri Z Basciftci FA Can demineralized enamel surfaces be bonded safely? Acta Odontol Scand 2014 72 4 283 289 10.3109/00016357.2013.823646 23964632 26. Ekizer A Zorba YO Uysal T Ayrikcila S Effects of demineralizaton-inhibition procedures on the bond strength of brackets bonded to demineralized enamel surface Korean J Orthod 2012 42 1 17 22 10.4041/kjod.2012.42.1.17 23112927 27. Enan E Tawfik MA Mehesen R Basha S Remineralization potential and shear bond strength of surface treated hypomineralized enamel in bonding of orthodontic brackets: An in vitro study J Adv Oral Res 2021 12 1 127 133 10.1177/2320206820977734 28. Khargekar NR Kalathingal JH Sam G Elpatal MA Hota S Bhushan P Evaluation of different pretreatment efficacy with fluoride-releasing material on shear bond strength of orthodontic bracket: An in vitro study J Contemp Dent Pract 2019 20 12 1442 1446 10.5005/jp-journals-10024-2697 32381847 29. Mishra S. Comparative evaluation of shear bond strength of orthodontic brackets on pretreatment with CPPACP, Fluor protector and Phosflur: An in-vitro study. J Clin Diagn Res. 2014;8(5):ZC01-5. 30. Nimbalkar S, Lim LH, Lee ZT, Lim KH, Sia SY. Efficacy of three enamel protecting agents on shear bond strength of orthodontic brackets bonded to demineralised enamel with conventional adhesive. J Clin Diagn Res. 2021;15(12):18-21. 31. Awad S El-Bialy A Hafez A El-Wassefy N Shamaa M Effect of remineralizing agents with/without laser irradiation on enamel properties and shear bond strength Int J Med Dent 2022 26 2 248 255 32. Baka ZM Akin M Ileri Z Basciftci FA Effects of remineralization procedures on shear bond strengths of brackets bonded to demineralized enamel surfaces with self-etch systems Angle Orthod 2016 86 4 661 667 10.2319/041515-247.1 26524389 33. Baysal A Uysal T Do enamel microabrasion and casein phosphopeptide-amorphous calcium phosphate affect shear bond strength of orthodontic brackets bonded to a demineralized enamel surface? Angle Orthod 2012 82 1 36 41 10.2319/041211-265.1 21787200 34. Daneshkazemi P Sadeghian S Khodaei M Shear bond strength of orthodontic brackets on intact and demineralized enamel after application of resin infiltrant, fluoride varnish and casein phosphopeptide-amorphous calcium phosphate remineralizing agents: in-vitro study Int Orthod 2021 19 2 259 268 10.1016/j.ortho.2021.03.001 33775598 35. Gulec A Goymen M Assessment of the resin infiltration and CPP-ACP applications before orthodontic brackets bonding Dent Mater J 2019 38 5 854 860 10.4012/dmj.2019-021 31434834 36. Topsakal KG Amuk NG Effects of different remineralisation agents and adhesives around orthodontic brackets: Is there a relationship between remineralisation and shear bond strength? Oral Health Prev Dent 2019 17 6 567 577 31631193 37. Uy E Ekambaram M Lee GHM Yiu CKY Remineralization potential of calcium and phosphate-based agents and their effects on bonding of orthodontic brackets J Adhes Dent 2019 21 3 219 228 31165104 38. Uysal T Baysal A Uysal B Aydınbelge M Al-Qunaian T Do fluoride and casein phosphopeptide-amorphous calcium phosphate affect shear bond strength of orthodontic brackets bonded to a demineralized enamel surface? Angle Orthod 2011 81 3 490 495 10.2319/090510-520.1 21261484 39. Veli I Akin M Baka ZM Uysal T Effects of different pre-treatment methods on the shear bond strength of orthodontic brackets to demineralized enamel Acta Odontol Scand 2016 74 1 7 13 10.3109/00016357.2014.982703 25892478 40. Al-Kawari HM Al-Jobair AM Effect of different preventive agents on bracket shear bond strength: in vitro study BMC Oral Health 2014 14 28 10.1186/1472-6831-14-28 24678892 41. Çehreli SB Şar C Polat-Özsoy O Ünver B Özsoy S Effects of a fluoride-containing casein phosphopeptide-amorphous calcium phosphate complex on the shear bond strength of orthodontic brackets Eur J Orthod 2012 34 2 193 197 10.1093/ejo/cjq183 21317209 42. Ladhe KA Sastri MR Madaan JB Vakil KK Effect of remineralizing agents on bond strength of orthodontic brackets: An in vitro study Prog Orthod 2014 15 1 28 10.1186/s40510-014-0028-y 24935482 43. Park SY Cha JY Kim KN Hwang CJ The effect of casein phosphopeptide amorphous calcium phosphate on the in vitro shear bond strength of orthodontic brackets Korean J Orthod 2013 43 1 23 28 10.4041/kjod.2013.43.1.23 23504444 44. Tabrizi A Cakirer B A comparative evaluation of casein phosphopeptide-amorphous calcium phosphate and fluoride on the shear bond strength of orthodontic brackets Eur J Orthod 2011 33 3 282 287 10.1093/ejo/cjq062 20651043 45. Xiaojun D Jing L Xuehua G Hong R Youcheng Y Zhangyu G Sung J Effects of CPP-ACP paste on the shear bond strength of orthodontic brackets Angle Orthod 2009 79 5 945 950 10.2319/101108-573.1 19705946 46. Farhadian N Rezaei-Soufi L Jamalian SF Farhadian M Tamasoki S Malekshoar M Javanshir B Effect of CPP-ACP paste with and without CO2 laser irradiation on demineralized enamel microhardness and bracket shear bond strength Dental Press J Orthod 2017 22 4 53 60 10.1590/2177-6709.22.4.053-060.oar 28902250 47. Philip N Walsh L The potential ecological effects of casein phosphopeptide-amorphous calcium phosphate in dental caries prevention Aust Dent J 2019 64 1 66 71 10.1111/adj.12661 30375646 48. Rahiotis C Vougiouklakis G Eliades G Characterization of oral films formed in the presence of a CPP-ACP agent: An in situ study J Dent 2008 36 4 272 280 10.1016/j.jdent.2008.01.005 18291571 49. Rüttermann S Braun A Janda R Shear bond strength and fracture analysis of human vs. bovine teeth PLoS One. 2013 8 3 e59181 10.1371/journal.pone.0059181 23527125 50. Yassen GH Platt JA Hara AT Bovine teeth as substitute for human teeth in dental research: a review of literature J Oral Sci 2011 53 3 273 282 10.2334/josnusd.53.273 21959653 51. Tran L Tam DNH Elshafay A Dang T Hirayama K Huy NT Quality assessment tools used in systematic reviews of in vitro studies: A systematic review BMC Med Res Methodol 2021 21 1 101 10.1186/s12874-021-01295-w 33964880 52. Ahmed T Fareen N Alam MK The effect of surface treatment and thermocycling on the shear bond strength of orthodontic brackets to the Y-TZP zirconia ceramics: A systematic review Dental Press J Orthod 2021 26 5 e212118 10.1590/2177-6709.26.5.e212118.oar 35640082 53. Bishara SE Soliman M Laffoon J Warren JJ Effect of changing a test parameter on the shear bond strength of orthodontic brackets Angle Orthod 2005 75 5 832 835 16279831