Residual Dentin Thickness in Bifurcated Maxillary Premolars after Cervical Preflaring Preparation: A CBCT Analysis

Gilberto Siebert Filho1, Orlando Aguirre Guedes2, *, Thiago Machado Pereira1, Fabio Luís Miranda-Pedro1, Andreza Maria Fábio Aranha1, Helder Fernandes de Oliveira2, Jesus Djalma Pécora3, Álvaro Henrique Borges1
1 Department of Endodontics, Dental School, University of Cuiabá, Cuiabá, Mato Grosso, Brazil
2 Department of Endodontics, Dental School, Evangelical University of Goiás, Anápolis, Goiás, Brazil
3 Department of Restorative Dentistry, Dental School, University of São Paulo, Ribeirão Preto, São Paulo, Brazil

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© 2021 Filho et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Endodontics, Dental School, Evangelical University of Goiás, Av. Universitária, Km 3,5, Cidade Universitária, 75083-515, Anápolis, Goiás, Brazil; Tel: +55 62 3310-6630; E-mail:



This study evaluated the residual dentin thickness (RDT) of maxillary premolars after the use of different cervical preflaring (PF) drills by using cone-beam computed tomography (CBCT).


Eighty bifurcated maxillary premolars were accessed and randomly divided into 5 groups (n=16). PF was performed with Gates-Glidden #1, #2, and #3 (group 1), Largo #1 and #2 (group 2), and LA Axxess #20/.06 (group 3), #35/.06 (group 4), and #45/.06 (group 5). CBCT images were acquired before (preoperative) and after (postoperative) PF. Initial and final cervical dentin thickness was measured at the buccal, palatal, mesial, and distal aspects, 0.5 mm coronally to the furcation, on both buccal and palatal roots, using CBCT’s image analysis software. The percentage of removed dentin after PF preparation was also calculated. Data were analyzed using ANOVA followed by Tukey’s test at a significance level of P < 0.05.


No statistically significant differences were found among the groups for preoperative or postoperative RDT (P > 0.05). LA Axxess #20/.06 (group 3) removed significantly less cervical dentin at all root canal aspects on both buccal and palatal roots. The mesial aspect of the buccal root and distal aspect of the palatal root were significantly reduced after the use of LA Axxess #45/.06 (group 5) and Largo #1 and #2 drills (group 2), respectively (P < 0.05).


PF in bifurcated maxillary premolars should be performed with LA Axxess instrument #20/.06. The use of Gates-Glidden #1, #2, and #3, Largo #1 and #2, and LA Axxess #45/.06 drills should be done with caution.

Keywords: Bifurcated maxillary premolars, Cervical preflaring, Cone-beam computed tomography, Coronal flaring, Residual dentin thickness, Vertical root fracture.