The Efficacy and Efficiency of Clear Aligners in Comparison to Traditional Fixed Appliances: A Systematic Review Volume 51- Issue 5

Rachid Ait Addi^1,2*, Abdelhafid Benksim^2,3 and Mohamed Cherkaoui²

• ¹Dr AIT ADDI Dental Center, Marrakech, Morocco
• ²Laboratory of Human Ecology, Department of Biology, School of Sciences Semlalia, Cadi Ayyad University, Marrakech, Morocco
• ³High Institute of Nursing and Technical Health, Marrakech, Morocco

Received: July 20, 2023;   Published: July 28, 2023

*Corresponding author: Rachid Ait Addi, Laboratory of Human Ecology, Department of Biology, School of Sciences Semlalia, Cadi Ayyad University, Marrakesh, Morocco

DOI: 10.26717/BJSTR.2023.51.008167

Abstract PDF

Backgrounds: The technology behind clear aligners has seen significant advancements in recent years. The objective of this systematic review was to examine and confirm whether the treatment effectiveness of clear aligners aligns with that of conventional fixed appliances.
Methods: We conducted an electronic search using various databases, including Pubmed, Medline, Embase, Google Scholar, and the Cochrane Central of Controlled Clinical Trials Register between January 1st, 2018, and January 1st, 2023. Included in this analysis were comparative clinical studies that evaluated the effectiveness of clear aligners in comparison to braces.
Results: Five papers were included in the systematic review: a retrospective study and four randomized clinical trials. Clear aligners reduce treatment duration, chairside time, number of nonscheduled, and finishing stage appointments in nonextraction Class I crowding cases. However, Conventional multibrackets appliance showed the highest incisal position variations over treatment.
Conclusion: Both clear aligners and braces demonstrated effectiveness in treating malocclusion. Clear aligners exhibited advantages in terms of segmented tooth movement and shorter treatment duration. However, they were found to be less effective than braces in achieving sufficient occlusal contacts, controlling teeth torque, and maintaining retention.

Keywords: Bracket; Clear Aligner; Orthodontics; Treatment Outcome; Systematic Review

Abbreviations: JBI: Joanna Briggs Institute; RCTs: Randomized Controlled Trials; MBT: McLaughlin Bennett Trevisi; CAT: Clear Aligner Therapy; MAAs: Modified Aligner Appliances with Nickel-Titanium Springs; OGS: Objective Grading System

The technology behind clear aligners has seen significant advancements in recent years. Clear aligners have become a popular choice for many patients due to their enhanced comfort and aesthetics, although ongoing discussions remain regarding their efficacy [1]. The concept of clear orthodontic appliances was first introduced by Kesling in 1946 [2]. In 1998, Align Technology, Inc. introduced Invisalign ®, which revolutionized the field of orthodontics [3]. The utilization of clear aligners has become increasingly prevalent owing to advancements in material technology and computer-aided tooth movement design [4].

Several late investigations have revealed the efficacy of clear aligners in treatment of diverse types of malocclusions with good results [5,6]. However, there are concerns about clear aligners completely replacing traditional orthodontic approaches, as some patients prioritize aesthetically pleasing and comfortable treatment methods. It is important to acknowledge that fixed braces have served as the standard and most effective orthodontic option for more than a century [7]. The question of whether transparent aligners can be a suitable alternative to braces is still a subject of debate within the orthodontic community [8]. Due to the limited conclusive evidence regarding the efficacy of clear aligner treatments, practitioners have relied on their clinical expertise and existing evidence to develop treatment approaches [9]. Further research are fundamental to draw more decisive deductions in the comparison of the efficacy of clear aligners and conventional braces. This systematic review was conducted to furnish an updated comparison of the efficacy and efficiency of clear aligners and traditional braces.

Focused Question

In conducting this systematic review, strict adherence to the PRISMA 2020 guidelines for reporting items for systematic reviews was followed to ensure methodological rigor. The main research query directed in this review referred to the comparison of treatment efficacy and efficiency between clear aligners and conventional braces. To preserve uniformity and clearness all around the review operation, the definitions of population, intervention, comparison, outcome, and study design (PICOS) were established based on (Table 1), which furnished a setting for organizing the review and guarantying a complete exploration of the vacant documentation.

Table 1: PICOs question.

Note: PICOs: Population, intervention, comparison, outcome and study design.

Search Strategies

We directed electronic research utilizing several databases, as well as Pubmed, Medline, Embase, Google Scholar, and the Cochrane Central of Controlled Clinical Trials Register. The search was performed without any restrictions on language or time. The aim was to capture a comprehensive range of relevant studies. For inclusion in our review, studies published between January 1st, 2018, and January 1st, 2023, were considered. This timeframe ensured that we included recent and up-to-date literature to inform our analysis. The detailed search strategies were as follows:

#1 (orthodont* OR clear OR removable) AND aligner*
#2 Invisalign
#3 #1 or #2
#4 conventional orthodontic treatment OR traditional orthodontic
treatment OR brace* OR bracket* OR fixed appliance*
#5 #3 AND #4

Eligibility Criteria

The inclusion and exclusion criteria utilized to choose paper for investigation are summarized in (Table 2). This table provides a clear overview of the criteria employed to determine which studies were included in our review. By establishing these criteria, we aimed to ensure the relevance and quality of the articles included in our analysis while maintaining transparency in our methodology.

Table 2: Inclusion and exclusion criteria.

Study Selection and Data Extraction

To guarantee a strict and unbiased picking operation, two researchers separately tracked down the titles and abstracts of the recognized studies. If a study could not be definitively excluded based on the information provided in the titles and abstracts, it was further assessed through full-text analysis. If there were any discrepancies between the two researchers, a debate was kept with a third researcher to attain consensus. The inter-reviewer trustworthiness of study choice was evaluated by computing the percentage of accordance defining the value of Kappa. Data extraction was directed separately by the two researchers utilizing the PICOs method. Any discrepancies in the extracted data were resolved through discussions with a third investigator. The subsequent information was taken from every enclosed study: the first author’s name, year of publication, country, study design, clinicians involved, inclusion criteria, gender distribution, number of participants, mean age of participants, description of intervention and comparison groups, primary outcomes (specifically treatment effectiveness), treatment duration, and the study’s conclusion. This comprehensive data extraction process aimed to capture key information from each study to facilitate an in-depth analysis and synthesis of the findings.

Quality Assessment

To evaluate the goodness of the enclosed retrospective case-control studies, the Joanna Briggs Institute (JBI) tool was utilized. This tool provided a systematic approach to evaluating the methodological quality of these studies. Additionally, the quality assessment of randomized controlled trials (RCTs) was conducted following the recommendations provided by Cochrane, which sorted rankings founded on seven essential criteria: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other potential sources of bias [10]. The results of these quality assessments are exposed in Tables 3 & 4, providing a transparent overview of the strengths and limitations of the included studies in terms of their methodological rigor.

Table 3: Risk of bias assessment using the RoB2 tool.

Note: Domains:
D1: Bias arising from the randomization process.
D2: Bias due to deviation from the intended interventions.
D3: Bias due to missing outcome data.
D4: Bias in measurement of the outcome.
D5: Bias in the selection of the reported result.
Judgment:
X - High
- - Some concerns
+ - Low

Table 4: The JBI critical appraisal for retrospective case control studies.

Note: JBI: Joanna briggs institute.

Literature Search

Initially, a total of 3299 primary references were identified through the literature search. Following the screening of titles and abstracts, 32 references remained for full-text evaluation. Manual searching of the reference lists of these selected studies did not yield any additional pertinent manuscripts. After the examination of the full-text articles, a total of five papers met the inclusion criteria and were included in our systematic review. The flow diagram representing the literature search process is presented in (Figure 1), providing a visual description of the study selection and inclusion process. This comprehensive approach ensured that the final set of included studies was relevant and met the predetermined criteria for our review.

Study Characteristics and Rob

The studies included in our analysis encompassed a retrospective study conducted in Italy in 2018 and four randomized clinical trials published in 2021, 2022, and 2023, and conducted in India, USA, Syria and Brazil [11-15]. Specialized orthodontist was responsible for treatments and the entire explorations were executed in the universities. The retrospective study aimed to compare the buccolingual inclination of upper incisors in patients treated with clear aligners versus fixed appliances, using radiographic analysis [11]. One randomized clinical trial compared the efficacy and efficiency of clear aligners versus 2 x 4 fixed appliances in correcting irregularities in maxillary incisor position during the mixed dentition phase [12]. A second randomized clinical trial explored the treatment and posttreatment outcomes of traditional braces and compared them with Invisalign aligners associated to Smart Force features and attachments [13]. Another study compared the efficacy of the McLaughlin Bennett Trevisi (MBT) appliance and Clear Aligner Therapy (CAT) in nonextraction Class I crowding cases [14]. Lastly, a randomized clinical trial evaluated the effectiveness of modified aligner appliances with nickel-titanium springs (MAAs) for treating mild mandibular crowding, assessing treatment duration, alignment improvement percentage, and mandibular incisor proclination. [15].

In terms of risk of bias, the study of Jaber ST, et al. (2021) was considered to have a moderate risk of bias based on the RoB2 tool (Table 3). The retrospective case-control study was assessed using the JBI critical appraisal checklist, which had low risk of bias (Table 4). A total of 119 participants were treated with clear aligners, while another 120 participants were treated with fixed braces. The number of patients in each study ranged from 13 to 34. The gender ratio of all included studies was balanced between two groups except one study not reporting the gender of patients [11]. The mean age of patients ranged from 9.33 to 32 years. Four of the studies included nonextraction patients in the research [12-15] and one study included extraction patients [11]. The included patients in three studies were Class I malocclusion [11,12], while the remaining five studies did not mention the classification of malocclusion of patients [13-15]. A summary of the included articles and their key characteristics is provided in Table 5, offering a concise overview of the studies included in our systematic review.

Figure 1

Table 5: A summary of included studies.

Treatment Effectiveness

Two included studies explored the treatment efficacy of clear aligners and braces [12,15]. The first study showed that compared to braces, modified aligner with nickel-titanium springs could be efficacious in lower incisor leveling, associated to lower incisor proclination. The second study discovered equivalent effectiveness in upper incisor rectifications in mixed dentition between 2 X 4 mechanics and clear aligners [12,15].

Treatment Efficiency

Three included studies evaluated the treatment efficiency between aligners and fixed appliances [12-14]. Similar treatment duration between clear aligners and 2 x 4 mechanics in the mixed dentition was found in the first study, while 4.8 months longer treatment times is needed with aligners than traditional braces in the second study with no statistically significant difference in posttreatment modifications of the total objective grading system (OGS) [12,13]. The third study found that Clear Aligner Therapy significantly reduces treatment duration, chairside time, number of nonscheduled/emergency, and finishing stage appointments in nonextraction Class I crowding cases compared to McLaughlin Bennett Trevisi (MBT) preadjusted edgewise appliance [14].

Torque Control of Upper Central Incisors

In our systematic review, a study compared the radiographic buccolingual inclination of upper incisors in patients treated with conventional, self-legating braces and clear aligners. The study discovered that conventional braces showed the highest incisal situation changes during the treatment [11].

This review examined five studies. The first study deduced that clear aligners are less efficacious in treating malocclusion than braces [13]. Another study discovered no statistically significant difference between clear aligners and 2 × 4 mechanics in the mixed dentition [12]. However, two studies showed that clear aligners are more effective and efficient than braces [14,15]. Similarly, in the study of Zheng et al. chair time and treatment duration were less with clear aligners than braces [6]. However, Li et al. discovered that treatment duration was forty-four percent less with braces than clear aligners in extraction cases [17]. The last study included in the review found that conventional fixed appliances provide better torque control of the upper central incisor than clear aligners [11]. Actually Djeu, et al. explained in a study that included non-extraction cases that poor control of root torque is the mean reason for statistically lower scores of clear aligners in 2005 [16]. Nevertheless, no statistically significant difference between clear aligners and braces was discovered in the Li’s study with included extraction cases [17]. This difference could be related to the inclusion of the extraction cases because extraction space may be utilized to correct overjet [18]. In addition, Ke et al., discovered that braces are better in creating sufficient occlusal contacts and controlling posterior buccolingual inclination than clear aligners [18].

Furthermore, in non-extraction cases, clear aligners are more effective in preserving teeth inclination in the time of alignment [19]. Nonetheless, more relapse in tooth alignment occurred in the post-retention period amongst clear aligners patients. Braces, utilizing rectangular archwires, align and expand arches not only by tipping teeth but also by torquing roots [18]. Besides, the success of treatment is fully related to the wearing of clear aligners because they are removable, which makes demanding to have good results. Also, with braces tipping and proclination are done at the same time of alignment because they apply forces to the center of resistance of teeth. Clear aligners reduce the proclination of teeth during alignment which may indicate them more in thin gingival biotypes to prevent receding gums [18]. Likewise, it needs 7-14 days for alveolar bone resorption, and it needs the same duration for periodontal tissue regeneration which explain the need of three weeks to adjust orthodontic devices for repairing procedures. If the orthodontist doesn’t allow sufficient time for this repairing procedures, bone resorptions and teeth harm will appear.

Further, clear aligners adjustments are at two-week intervals while they are at 4-6 weeks amongst braces. This may explain that because of the shortness of clear aligners adjustments for repairing procedures, more relapses may occur than with braces [19]. Nevertheless, clear aligners offer improved aesthetics, comfort, and oral hygiene for patients compared to conventional fixed appliances [19-22]. This systematic review is the first one conducted in Morocco to give an updated comparison of the efficacy and efficiency of clear aligners compared to traditional braces. Nevertheless, there are certain limitations to consider. Eliminating confounding factors present in the included studies proves to be challenging, potentially introducing bias. Additionally, thanks to digital dentistry technologies and Artificial Intelligence progresses, the clear aligners technique is unceasingly developing new methods and accessories to reduce their limitations. Recent research indicates more favorable outcomes with aligner treatment compared to earlier studies. Therefore, it is imperative to conduct additional relevant studies that include subgroup analyses to address confounding factors effectively. Furthermore, given the limited number of included studies (five), further randomized controlled trials are necessary to establish high-quality evidence.

Effectiveness in improving malocclusion in both aligners and braces were proved, but braces were more effective than aligners in establishment of sufficient occlusal contacts, improving transverse width and controlling posterior buccolingual inclination. Also, clear aligners demonstrated good control in maintaining teeth inclination and less treatment duration in nonextraction cases. Therefore, the orthodontist must consider the characteristics of these two orthodontic appliances and use them according to the cases to be treated when making a therapeutic decision.

All data generated or analyzed during this study are included in this published article.

RA: study selection, data extraction, data synthesis, quality assessment, and drafting the manuscript.
AB: research design, study selection, data extraction, and revision of the manuscript.
MC: research design and revision of the manuscript. All authors read and approved the final manuscript.

The authors want to acknowledge the Editorial office of the journal and all the anonymous reviewers.

The authors declare no conflict of interest.

1. Chishti MS, Ahmad T, Harris AM (2015) Clear aligners in orthodontic treatment. Journal of Orthodontics 42(3): 220-226.
2. Kesling HD (1945) The philosophy of the tooth positioning appliance. American Journal of Orthodontics and Oral Surgery, 31(6): 297-304.
3. Sheridan JJ (2004) Led by the nose: the evolution of appliance therapy. Journal of Orthodontics 31(1): 34-47.
4. Djeu G, Shelton C, Maganzini A (2005) Outcome assessment of Invisalign and traditional orthodontic treatment compared with the American Board of Orthodontics objective grading system. American Journal of Orthodontics and Dentofacial Orthopedics 128(3): 292-298.
5. Rossini G, Parrini S, Castroflorio T, Deregibus A, Debernardi CL (2015) Efficacy of clear aligners in controlling orthodontic tooth movement: A systematic review. The Angle Orthodontist 85(5): 881-889.
6. Zheng M, Liu R, Ni Z, Yu Z (2020) Clear aligner treatment for orthodontic patients with mild to moderate crowding: A systematic review and meta-analysis. Journal of Dentistry 98: 103369.
7. Proffit WR, Fields HW, Sarver DM (2018) Contemporary Orthodontics (6^th)., Elsevier.
8. Fleming PS (2021) Clear aligners for orthodontic treatment. Evidence-Based Dentistry 22(1): 2-3.
9. Lombardo L (2017) Clear aligner treatment outcomes: A retrospective study. Journal of Dentistry, p. 67.
10. Higgins JP, Thompson SG, Spiegelhalter DJ (2009) A re-evaluation of randomeffects meta-analysis. J R Stat Soc Ser A Stat Soc 172: 137-159.
11. Maria Francesca Sfondrini, Paola Gandini, Tommaso Castroflorio, Francesco Garino, Luca Mergati, et al. (2018) Buccolingual Inclination Control of Upper Central Incisors of Aligners: A Comparison with Conventional and Self-Ligating Brackets. BioMed Research International 2018: 7.
12. Da Silva VM, Ayub PV, Massaro C, Janson G, Garib D (2023) Comparison between clear aligners and 2 × 4 mechanics in the mixed dentition: a randomized clinical trial. Angle Orthod 93(1): 3-10.
13. Lin E, Julien K, Kesterke M, Buschang PH (2022) Differences in finished case quality between Invisalign and traditional fixed appliances. Angle Orthod 92(2): 173-179.
14. Shiv Shankar Agarwal, Sanjeev Datana, MP Prasanna Kumar, Mohit Sharma, Pushkar Andhare (2021) Comparison of efficacy between MBT preadjusted edgewise appliance and clear aligner therapy among class I crowd cases: A randomized controlled trial, Medical Journal Armed Forces India.
15. Alhafi ZM, Rajeh N (2022) Evaluation of the effectiveness of modified aligner appliance with nickel-titanium springs in treatment of mild crowding of lower incisors: A randomized controlled clinical trial. J World Fed Orthod 11(4): 107-113.
16. Ke Y, Zhu Y, Zhu MA (2019) comparison of treatment effectiveness between clear aligner and fixed appliance therapies. BMC Oral Health 19: 24.
17. Li W, Wang S, Zhang Y (2015) The effectiveness of the Invisalign appliance in extraction cases using the the ABO model grading system: a multicenter randomized controlled trial. Int J Clin Exp Med 8: 8276-82.
18. Hennessy J, Garvey T, Al Awadhi EA (2016) A randomized clinical trial comparing mandibular incisor proclination produced by fixed labial appliances and clear aligners. Angle Orthod 86: 706-12.
19. Isaacson RJ, Lindauer SJ, Davidovitch M (1993) On tooth movement. Angle Orthod 63: 305-309.
20. Proffit WR, Fields HW Jr (2000) Contemporary orthodontics (3^rd )., USA: Mosby 296-361: 594-614.
21. Azaripour A, Weusmann J, Mahmoodi B, Peppas D, Gerhold Ay A, et al. (2015) Braces versus Invisalign(R): gingival parameters and patients' satisfaction during treatment: A cross-sectional study. BMC Oral Health 15: 69.
22. White DW, Julien KC, Jacob H, Campbell PM, Buschang PH (2107) Discomfort associated with Invisalign and traditional brackets: a randomized, prospective trial. Angle Orthod 87: 801-808.