Influence of cervical preflaring and root canal preparation on the fracture resistance of endodontically treated teeth

Abstract

Background: Evaluate the fracture resistance of endodontically treated teeth after cervical preflaring and root canal preparation and to assess the volume of the root canal and the amount of remaining root dentin before and after cervical preflaring. Methods: Forty-four mandibular incisors were selected using micro-CT scanning and distributed into 4 groups (n = 11) according to the instrument used for cervical preflaring: control group -no cervical preflaring; Gates Gliddenburs size #2 and #3; WXN -25.07 Navigator instrument; and Easy -25.08 ProDesign S instrument. Coronal opening was performed, and the canals were prepared with Wave One Gold Primary and filled with an epoxy-resin based sealer and gutta-percha cones. Micro-CT scans were performed before and after root canal instrumentation. All images were reconstructed and assessed for the thickness of mesial and distal root dentin at 3 mm and 5 mm from the cement -enamel junction and for the volume of cervical portion of the canal after preparation. Fracture resistance test was performed applying compressive loads at a crosshead speed of 0.5 mm/min, applied on the palatal aspect of specimens at 135°along the long axis of the tooth. The data were analyzed using ANOVA and Tukey's test (P = .05). Results: Cervical preflaring and canal preparation reduced the dentin thickness (P < .05) and increased the canal volume (P < .05) in all groups at 3 mm an 5 mm. Cervical preflaring with Gates Gliden burs reduced the fracture resistance of endodontically treated teeth (P < .05). Conclusions: All instruments reduced the dentin thickness and increased the canal volume in the cervical at 3 mm and 5 mm. Gates Glidden reduced fracture resistance of mandibular incisors submitted to cervical preflaring, whereas NiTi instruments did not. Clinical relevance: Cervical preflaring assumes particular importance previously to the root canal preparation because it minimizes the occurrence of operative accidents, and permits more accurate determination of working length and the apical diameter.

Micro‐CT evaluation of ‘danger zone’ and microcrack formation in mesial root canals of primary teeth with single‐file rotary and reciprocating systems

“…[2][3][4][5] It is reported that additional effects from occlusal forces will result in vertical root fractures due to thinning of dentin walls with excessive shaping of the root canal, and microcracks occurring in these root walls. [7][8][9]30 It is stated that the thickness of the root dentin in the furcation area is considerably reduced, especially in the lower primary molars, and these areas should be considered danger zones. 5 It has been reported that this variation is more common and diversified in mesial roots, and angulation is also higher.…”

“…Besides anatomical vulnerability to weakness, it is also stated that the working principles of the rotary systems and the designs of the files may cause overpreparation or microcracks in the dentin walls. [7][8][9] There is no consensus on whether file designs and movement properties cause dentin defects or complications. Some researchers claim that there is no causal relationship, 10 whereas others claim that the stress created at the root is affected by these variables and that there is a potential relationship between them.…”

Assessment of the shaping ability of three systems used in long oval canals

“…In addition, the preparation tends to preserve the original root canals anatomy (Vertucci, 2005). Also, the preflaring is a fundamental step in the treatment, as in addition to removing the most infected dentin portion, it favors the establishment of the WL and the anatomical diameter (Borges et al, 2018;da Silva et al, 2020;Plotino et al, 2020), factors that better adjust the file in the apical region (Barroso, Guerisoli, Capelli, Saquy, & Pécora, 2005).…”

“…Since the cervical third of the root canal is the most contaminated region, efforts are made to minimize this condition. Thus, cervical preflaring favors the determination of working length (WL) and anatomical diameter, and minimizes accidents (Borges, Damião, Pereira, Filho, Miranda-Pedro, Luiz de Oliveira da Rosa, Piva, & Guedes, 2018;da Silva, Duarte, Alcalde, Duarte, Vivan, da Rosa, Só, & do Nascimento, 2020;Plotino, Nagendrababu, Bukiet, Grande, Veettil, De-Deus, & Aly Ahmed, 2020). Despite being the region that generally suffers the most from the instruments, da Silva et al (2020), in a study with mandibular incisors, concluded that preflaring and root canal preparation itself reduced dentinal thickness, however, NiTi instruments were not able to change the fracture resistance of these teeth.…”

Stress Concentration of Endodontically Treated Molars Restored with Transfixed Glass Fiber Post: 3D-Finite Element Analysis

“…The loss of dental structure caused by endodontic treatment is responsible for a decrease in tooth resistance, which increases susceptibility to fracture [ 1 ]. The longevity of endodontically treated teeth is influenced by several factors, such as, the preservation of remaining dental tissue, effectiveness of restorative procedures and occlusal force [ 2 ].…”