Research Article EffectofMethotrexateInjectiononOrthodonticToothMovement: An Experimental Study on Rats Amin Golshah , 1 Khaled Omidi , 2 Nafiseh Nikkerdar , 3 Hedaiat Moradpoor , 4 and Fatemeh Ghorbani 1,5 1 Department of Orthodontic, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran 2 Student Research Committee Kermanshah University of Medical Sciences, Kermanshah, Iran 3 Department of Maxillofacial Radiology, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran 4 Department of Prosthodontics, School of Dentistry, Kermanshah University of Medical Sciences, Kermanshah, Iran 5 Medical Biology Research Center, Health Technology Institute, Kermanshah University of Medical Sciences, Kermanshah, Iran Correspondence should be addressed to Fatemeh Ghorbani; tima.ghorbani@gmail.com Received 6 July 2021; Revised 27 September 2021; Accepted 22 October 2021; Published 8 November 2021 Academic Editor: Alejandro Pelaez Vargas Copyright©2021AminGolshahetal.isisanopenaccessarticledistributedundertheCreativeCommonsAttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Introduction. Knowledge about the effects of medications, vitamins, and various supplements on orthodontic tooth movement (OTM) is imperative for orthodontists. is study aimed to assess the effect of methotrexate (MTX) injection on OTM in rats. Materials and Methods. Twenty-eight male Wistar rats were randomized into four groups (n � 7). e first molar and central incisor were connected using a nickel-titanium (NiTi) coil spring with a 50g load in each rat. e two experimental groups received 0.75 mg/kg and 1.5 mg/kg MTX, respectively, intraperitoneally for 21 days. e negative control group did not receive any injection and did not undergo orthodontic treatment. e positive control group underwent orthodontic treatment and received 0.9% saline (NaCl) injections for 21 days. All rats were sacrificed with chloroform inhalation after 21 days; their maxilla was resected, and the mean number of Howship’s lacunae, blood vessels, osteoclasts, and resorption lacunae was counted. e reduction in bone volume (bone volume to total volume ratio (BV/TV)) at the site of the maxillary molar was quantified by microcomputed tomography (micro-CT). Results. OTM, the number of osteoclasts, and the number of blood vessels significantly increased in rats treated with MTX (P < 0.05). However, the increase in the number of Howship’s lacunae and resorption lacunae was not significant (P > 0.05). Lower BV/TV in the MTX groups was in agreement with the increased number of osteoclasts. Conclusion. Injection of MTX can significantly increase OTM and decrease root resorption in rats. 1. Introduction Orthodontic tooth movement (OTM) occurs as the result of simultaneous modeling and remodeling of bone and the periodontal tissue. Orthodontic force application also alters the blood vessels in the periodontal tissue and subsequently the blood supply, resulting in local synthesis and release of different molecules [1]. e balanced activity of osteoclasts and osteoblasts plays a fundamental role in this respect [2]. In the process of OTM, osteoclasts are induced to resorb the old bone while osteoblasts are attracted to the areas re- quiring bone deposition [3]. e proliferation rate of os- teoclasts can be used as an important indicator of the level of OTM [4]. e regeneration of periodontal tissue is the basis of OTM. e pressure applied to the alveolar bone induces OTM and tissue regeneration. When the teeth reach their desired position, the alveolar bone and periodontal ligament regain their normal structure [5]. Orthodontic treatment often lasts for 1 to 2 years. us, it is imperative for orthodontists to have adequate knowl- edge about the effects of medications, vitamins, and various supplements on OTM. ey should efficiently communicate with patients in this respect, since many patients take dif- ferent medications for the prevention or treatment of their medical conditions. ese medications can reach the peri- odontal tissue, affected by the orthodontic forces, via the Hindawi International Journal of Dentistry Volume 2021, Article ID 8451522, 8 pages https://doi.org/10.1155/2021/8451522