Please cite this article in press as: Olsson B, et al. MSX1 is differentially expressed in the deepest impacted maxillary third molars. Br J Oral Maxillofac Surg (2020), https://doi.org/10.1016/j.bjoms.2020.04.006 ARTICLE IN PRESS YBJOM-5980; No. of Pages 6 British Journal of Oral and Maxillofacial Surgery xxx (2020) xxx–xxx Available online at www.sciencedirect.com ScienceDirect MSX1 is differentially expressed in the deepest impacted maxillary third molars B. Olsson a , R.D. Calixto a , N.C.S. Machado b , M.N. Meger b , F.W.G. Paula-Silva c , N.L.B. Rebellato a , D.J. Costa a , E.C. Küchler b , R. Scariot a,b,* a Department of Stomatology, Oral and Maxillofacial Surgery, Federal University of Paraná, Av. Prefeito Lothário Meissner, 632, Jardim Botânico, Curitiba, PR, 80210-170, Brazil b Department of Oral and Maxillofacial Surgery, Positivo University, Professor Pedro Viriato Parigot de Souza, 5300, Campo Comprido, Curitiba, Paraná, 81280330, Brazil c Department of Pediatric Dentistry, University of São Paulo, Av. do Café, Subsetor Oeste-11 (N-11), Ribeirão Preto, SP, 14040-904, Brazil Abstract An impacted third molar is one of the most common dental abnormalities. Among the reasons for impaction the most common are: insufficient space, time of eruption, improper position of the tooth bud, and genetic disruptions. To investigate if runt-related transcription factor 2 (RUNX2), bone morphogenetic protein 2 (BMP2), and msh homeobox 1 (MSX1) are differently expressed depending on the position of the molar, we studied 32 patients who had been referred for surgical removal. An orthopantomogram was used to separate them according to Winter’s, and Pell & Gregory’s, classifications. Bone samples were harvested during the operation for gene expression assay. The Kruskal–Wallis, Dunn’s post hoc, and Spearman’s correlation, tests were used to assess the significance of differences. No correlations were found in expression of the genes, and no differences between expression in maxillary and mandibular third molars, nor were they expressed differently according to Winter’s or Pell and Gregory’s classifications or in relation to impaction of the mandibular ramus. However, MSX1 was expressed differently when account was taken of the depth of impaction in maxillary third molars (p = 0.029), but there was no difference in expression of RUNX2, BMP2, and MSX1 for the Pell and Gregory classification of depth of impaction. We conclude that MSX1 is expressed differently depending on the depth of maxillary impaction phenotypes. © 2020 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved. Keywords: Gene expression; third molar; impacted tooth; transcription factor; MSX1 * Corresponding author at: 5300 Professor Pedro Viriato Parigot de Souza St. Campo Comprido, Curitiba, Paraná, 81280330, Brazil. Tel.: +55 (41) 3526-5124. E-mail addresses: bernardo.olsson@gmail.com, bernardo.olsson@ufpr.br (B. Olsson), robsonzahaila@hotmail.com, robsonzahaila@ufpr.br (R.D. Calixto), nilza.n@hotmail.com (N.C.S. Machado), michellemeger@hotmail.com (M.N. Meger), franciscogarcia@forp.usp.br (F.W.G. Paula-Silva), rebelato@ufpr.br (N.L.B. Rebellato), delsoncosta@ufpr.br (D.J. Costa), erikacalvano@gmail.com, erika.kuchler@up.edu.br (E.C. Küchler), rafaela scariot@yahoo.com.br, rafaela.moraes@up.edu.br (R. Scariot). Introduction Craniofacial development is a complex process that involves many molecular aspects. 1 Maxilla, mandible, and teeth are closely related with regards to their development, sharing the same time and molecular aspects. 1,2 Third molars are com- monly affected by developmental dental alterations, such as congenital absence 3 ; abnormal shape, size, and position; and no pattern of eruption chronology. 4 Many genes involved in the morphoregulation of craniofacial development could have a role in dental alterations, 5 including runt-related tran- scription factor 2 (RUNX2), bone morphogenetic protein 2 (BMP2) and msh homeobox 1 (MSX1). 1 https://doi.org/10.1016/j.bjoms.2020.04.006 0266-4356/© 2020 The British Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.