###### Abstract  
The objective of this article was to systematically review the literature to determine how effective tooth whitening procedures are when carried out in tandem with orthodontic clear aligners. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Online searches of PubMed, Medline via Ovid, Science Direct, the Cochrane database of systematic reviews via Ovid, Scopus, and Google Scholar as well as manual searches of the references of the selected articles were conducted. Clinical studies which assessed the efficacy of dental bleaching using orthodontic clear aligners were included in the present study. Data from the included studies were extracted and assessed for risk of bias using the Cochrane risk of bias tool. Three studies met the inclusion and exclusion criteria and were included in this study. One study compared the efficiency of tooth bleaching between clear aligners and conventional bleaching trays. One study evaluated the effectiveness of dental bleaching using clear aligners by comparing the tooth shade of those patients to a control group of patients who did not receive dental bleaching during orthodontic clear aligner treatment. One study evaluated the effectiveness of different concentrations of different bleaching agents using clear aligners. All the included studies showed an improved tooth shade when using clear aligners as bleaching trays.  
tooth whitening; dental bleaching; carbamide peroxide; clear aligners; Invisalign +
Footnote †: journal: Medical  
Orthodontic treatment with clear aligners has shown advantages over traditional fixed appliances, such as aesthetic comfort and increased patient acceptance [7; 15; 16; 17]. In addition, clear aligners are more convenient for eating and brushing since the aligners can be removed by the patients [12; 13; 14; 18]. Furthermore, tooth bleaching is frequently requested by orthodontic patients. One study showed that 88% of orthodontic patients asked for tooth whitening during or after orthodontic treatment [19; 20]. Another study reported higher patient satisfaction when dental bleaching was combined with orthodontic treatment when compared to orthodontic treatment only [21].  
At-home tooth whitening (Figure 3) has been a common approach to whiten the teeth since its introduction in 1989 by [PERSON] [22; 23; 24]. This is attributed to its efficiency, lower cost, feasibility, and reduced adverse effects such as tooth sensitivity and soft tissue burns [25; 26; 27; 28].  
Before the introduction of clear aligners, tooth bleaching was delayed until after the orthodontic treatment with a fixed appliance. This is for many reasons, including that tooth alignment achieved after the orthodontic treatment facilitates achieving a uniform tooth whitening. Moreover, waiting two weeks after finishing the orthodontic treatment with a fixed appliance would allow some time for the gingvae to heal in case of gingvitis, which would worsen if the tooth whitening started during the orthodontic treatment while the gingvae are still inflamed [29; 30].  
With the emergence of clear aligners, it is now possible to have the teeth bleached during the clear aligner therapy by using the aligner as a bleaching trap at night. This is also possible as studies have shown that bleaching using non-scalloped and non-reservoir trays is safe and effective [31; 32; 33; 34]. However, the question remains whether tooth bleaching performed using clear aligners during the orthodontic treatment is an effective treatment modality or whether dental bleaching should be postponed until after the completion of orthodontic treatment. Therefore, this systematic review aimed to evaluate the effectiveness of dental bleaching using orthodontic clear aligners for tooth shade improvement.  
Figure 3: Home bleaching kit with a tray which is worn at night until the desired tooth shade is achieved.  
Figure 2: A 3 Shape software used in this example to design a maxillary clear aligner.