Apical root canal anatomy in the mesiobuccal root of maxillary first molars: influence of root apical shape and prevalence of apical foramina – a micro‐CT study

Abstract

Aim To determine whether a relationship exists between the apical shape of roots and root canal system complexity by performing a micro‐computed tomography analysis. Methodology One hundred extracted permanent maxillary first molars were scanned using a micro‐computed tomography device at 19.6 μm voxel size. Two groups of mesiobuccal roots were formed according to the root aspect ratio value in the apical 3‐mm cross‐sectional level (‘<2 and ≥ 2.00’). Data were recorded regarding the number and presence of accessory canals and their location, isthmus, presence of the mesiobuccal canal and dentine thickness. Depending on the analysed variable, Mann–Whitney U test and Z‐test for proportions were used to compare groups. The significant level was set at 5%. Results Mesiobuccal roots with an aspect ratio ≥ 2.00 at the apical 3‐mm cross‐sectional level had higher percentages of accessory canals, apical foramina and MB2 root canals in the apical 3 mm. The vertical average distance from the accessory foramina and origin from the anatomic apex was 1.40 and 2.19 mm, respectively. Overall, 21.8% of the accessory canals had their origin coronal to a 3‐mm root resection line. There was no difference between the groups regarding dentine thickness. Conclusion The shape of the apical 3 mm of maxillary first molar mesiobuccal roots was a predictive factor for the presence of complex root canal systems. Roots with a lower aspect ratio had less complex apical anatomy.

A critical analysis of laboratory and clinical research methods to study root and canal anatomy

“…With the different types of micro-CT machines available in the market, it is not possible to recommend definite parameters for scanning; a pilot examination is usually needed for optimisation of the scanning parameters in terms of the amount of noise, contrast between dental tissues and clarity of structures, with considerations to the time per scan, storage and cost (Chavez et al, 2021). Indeed, information provided in related literature is also helpful-as an example, the voxel size for a human tooth ranges from <10 µm to about 30 µm (Ordinola-Zapata et al, 2019;Versiani et al, 2012Versiani et al, , 2016aZhang et al, 2014), which can be optimised based on the tooth type, study objectives and details needed for qualitative and quantitative analysis. The scanning itself is done automatically with no user interaction, but frequent supervision is advisable as several errors may occur such as X-ray source instability (du Plessis et al, 2017).…”

“…Micro‐CT technology provides opportunities for a wide range of measurements. The shape of a given object has indices for 2D measurements such as perimeter (P), area (A), form factor (FF), roundness (R), aspect ratio (AR), ellipticity/eccentricity (E), curvature (C), tortuosity (T) in addition to parameters related to 3D measurements such as volume (V), surface area (SA) and structure model index (SMI) (Filpo‐Perez et al, 2015; Ordinola‐Zapata et al, 2019; Versiani & Keleş, 2020; Versiani et al, 2011; Wirth, 2004). The algorithms and measurements used in micro‐CT software allow detailed quantitative descriptions of root and canal anatomy (Table 1, Figures 20–22), besides the high‐resolution qualitative presentations of the main and fine details.…”

“…The algorithms and measurements used in micro‐CT software allow detailed quantitative descriptions of root and canal anatomy (Table 1, Figures 20–22), besides the high‐resolution qualitative presentations of the main and fine details. For instance, one study reported that an increased aspect ratio (≥ 2 – ratio between maximum and minimum diameters) at the apical third of the MB roots in maxillary first molars has higher possibilities for more complex canal morphology compared to MB roots with lower aspect ratio (Ordinola‐Zapata et al, 2019) (Figure 21). Roundness and form factor provide quantitative analyses on the shapes of the root canal axial sections.…”

“…Awareness of this anatomy also provides explanations for the development of combined periodontal-endodontic lesions which can occur through a patent lateral apical foramen (Ahmed, 2012;Versiani et al, 2016b). Aspect ratio is another parameter which provides information about the complexity of the canal anatomy in the apical third of the root (such as MB root in maxillary molars); this has clinical implications related to the root resection level in root-end surgery F I G U R E 3 1 Micro-CT reconstructed images of a three-rooted maxillary molar tooth with complex canal anatomical variations in each of the MB, DB and P roots procedures (Ordinola-Zapata et al, 2019). Values obtained from roundness and form factor parameters can provide recommendations for the instrumentation technique to prevent leaving prepared canals with untouched walls (Filpo-Perez et al, 2015).…”

Effectiveness of photon-initiated photoacoustic streaming in root canal models with different diameters or tapers

“…In recent years, great progress has been made in the mechanical preparation of root canals; however, these methods are still unable to completely eradicate the bacteria within the root canal [ 3 , 4 ]. Irrigation is complementary to instrumentation in facilitating the removal of bacteria, debris, and the smear layer [ 5 ]. Previous studies have shown that instrumentation and irrigation with NaOCl eliminates bacteria in 50–75% of infected root canals at the end of the first treatment session, whereas the remaining root canals contain recoverable bacteria [ 6 ].…”