ORIGINAL ARTICLE Reciprocating instrumentation in a maxillary primary central incisor: A protocol tested in a 3D printed prototype Rafael dos Reis Moraes 1 | Thaís Maria Pires dos Santos 2 | Marília Fagury Marceliano-Alves 3 | Andreá Vaz Braga Pintor 1 | Ricardo Tadeu Lopes 2 | Laura Guimarães Primo 1 | Aline de Almeida Neves 1 1 Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 2 Laboratory for Nuclear Instrumentation, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil 3 Department of Dental Clinics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil Correspondence Aline de Almeida Neves, Department of Pediatric Dentistry and Orthodontics, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil. Email: aline.neves@odonto.ufrj.br Funding information Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Grant/Award Number: E-26/202.542/2017, E-26/203.185/2016 Summary Background: Efficient endodontic instrumentation of primary teeth is a challenge for paediatric dentists. Aim: To evaluate biomechanical outcomes of endodontic instrumentation with a reciprocating system in a polymer‐prototyped primary maxillary central incisor. Design: The specimen was systematically instrumented and micro‐CT scanned before and after each file. The amount of debris, percentage of non‐instrumented areas, removed dentin volume, and lower dentin thickness at specific points along the root canal were analyzed. Results: A 10% increase in removed dentin volume was observed when R40 was compared to R25 (14.5% vs 4.2%). When comparing R50 with R40, this increase was only 3.4% (17.9% vs 14.5%). In the root cervical third, there was substantial reduction in dentin thickness with R50 (48.8%), followed by R40 (39.5%) and R25 (18.6%). There was no difference between R25 and R40 in the removal of dentin at the apical third (15.8%), while R50 resulted in 39.8% reduction in dentin thickness. Percentage of non‐instrumented areas were the same for all files. Accu- mulated debris with R40 and R50 was the same (0.19 mm³) while for R25 was 0.11 mm³. Conclusions: The Reciproc ® system was effective for instrumentation of a proto- typed primary maxillary central incisor. The most suitable file for apical prepara- tion was R40. KEYWORDS endodontic instrumentation, primary central incisor, pulpectomy, Reciproc 1 | INTRODUCTION Keeping sound and/or infection‐free primary teeth in the oral cavity during the childhood period is the main objec- tive of the paediatric dentist. In fact, these teeth keep the necessary space for the permanent successors and partici- pate in many physiological oral functions, such as swallow- ing and vocalization, contributing thus to the general development of the child. 1 Pulpectomy is the procedure of choice for primary teeth with irreversible pulpitis or signs of necrosis. Throughout this procedure, the root canals are cleaned and shaped before being filled with a resorbable sealing/antibacterial paste. This technique has been tradi- tionally advocated in primary teeth with the aid of manual stainless steel endodontic files. 2 The use of nickel‐titanium (NiTi) motor‐driven rotary files in primary teeth, although not yet popular among pae- diatric dentists, has long been described. In fact, several Received: 10 April 2018 | Revised: 15 August 2018 | Accepted: 6 September 2018 DOI: 10.1111/ipd.12429 Int J Paediatr Dent. 2018;1–8. wileyonlinelibrary.com/journal/ipd © 2018 BSPD, IAPD and John Wiley & Sons A/S. Published by John Wiley & Sons Ltd | 1