###### Abstract  
Objective: To assess the tooth survival rates, adverse events, and need for further treatment of teeth previously treated with regenerative endodontics undergoing orthodontic treatment. Material and Methods: A literature search was performed using MEDLINE, EMBASE, Cochrane, Scopus, and Lilacs databases, grey literature, and endodontic journals, and the date of the last search was 20 April 2022. The included studies involved patients undergoing orthodontic treatment and at least one tooth that was previously treated with regenerative endodontics. A narrative synthesis of the findings was made. The risk of bias and evidence quality were assessed using the Effective Public Health Practice Project tool and the GRADE approach. Results: Five case reports included seven patients and eight teeth with a follow-up of 4 to 11 years. The overall risk of bias was high, and the certainty of evidence was very low. The survival rate was 87.5%. Adverse effects included sinus tracts, root resorption, symptomatology, apical periodontitis, and intracanal tissue necrosis. Five out of eight teeth required further intervention after orthodontics. Conclusions: A high prevalence of adverse effects and further intervention is observed in teeth treated with regenerative endodontics undergoing orthodontic treatment. The low quality of evidence highlights the need for comparative studies and evidence-based guidelines for managing these teeth during orthodontic treatment. adverse effects; orthodontic treatment; regenerative endodontics; revitalization; tooth movement techniques +
Footnote †: journal: Medical  
orthodontic tooth movement of teeth previously treated with regenerative endodontics. These concerns may be due to the possibility of a higher risk of internal root resorption compared to that with physiologically mature teeth and the possibility of devitalizing newly developed vascularized and innervated tissues within the root canal due to tooth movement. The histological evidence after RET demonstrates that root maturation is not based on the apposition of dentin, but rather on the apposition of reparative hard tissues, such as osteedentin and bone-like tissue or cementum-like tissue [11], whereas the secretion of dentin after RET has been reported only in occasional studies [12]. Dentin is a highly organized tissue with a tubule-like structure, while reparative tissues (i.e., cementum and bone) show collagen fibers packed in a disorderly manner and a higher organic composition, with cell lacunae [13]. Moreover, cementum and bone have inferior mechanical properties (i.e., elasticity and hardness) compared to dentin [14]. Thus, the maturation of the root based on reparative hard tissues may affect the performance of the tooth when subjected to mechanical stress due to external forces, such as biting, trauma, or orthodontic loads. Computational studies have shown that physiologically developed teeth distribute mechanical stress more advantageously than teeth that complete root maturation with cementum [15]. Root resorption is a well-known risk of orthodontic treatment [16]. In 2016, the Position Statement on revitalization procedures of the European Society of Endodontology stated that after regenerative endodontics, teeth should be excluded from orthodontic treatment or follow-up intervals should be shortened during orthodontic treatment, since they may be more susceptible to inflammation and apical root resorption [9; 17]. However, RET has recently been proposed as a possible solution for root resorption, since it may arrest the resorption process and allow for the progressive healing and remodeling of the lamina dura [18; 19], possibly due to the immunomodulatory effect of stem cells associated with the treatment. Regarding the loss of pulp vitality during orthodontic treatment, the forces applied to teeth and surrounding structures cause alterations in the pulp tissue [20], such as circulatory disturbances [20; 21], fibrosis and calcification [21], and a decrease in the pulp respiration rate [22].