Root dentine thickness in C-shaped lower second molars after instrumentation: A CBCT and micro-CT study

The Impact of Coronal Flaring Files on Pericervical Dentin Thickness in Mandibular Molars

INTRODUCTION

This study aimed to assess the influence of different coronal flaring files on dentin removal in mandibular teeth using cone-beam computed tomographic (CBCT) images.

METHODS

CBCT images of 48 mandibular molar teeth were acquired and randomly divided into 2 main groups, with each main group further divided into 3 subgroups. In the first main group, root canal preparation was performed using TruNatomy (Dentsply Sirona, Ballaigues, Switzerland), ProTaper Gold (Dentsply Sirona), and One Curve (Micro-Mega, Besancon, France) files without the use of coronal flaring files. In the second main group, root canal preparation was performed using the same files with the use of coronal flaring files. After the completion of root canal preparation, a second set of CBCT images was obtained. Subsequently, the dentin removal and remaining critical dentin were assessed by measuring at 4 distinct points below the furcation level. Data were compared between groups using the Mann-Whitney U and Kruskal-Wallis tests with alpha set at 5%.

RESULTS

The ProTaper Gold files demonstrated higher dentin removal compared with the TruNatomy files. In the no-flaring groups, the One Curve files exhibited greater dentin removal than the TruNatomy files at specific levels. The use of coronal flaring files generally did not significantly impact dentin removal, except for certain cases in the TruNatomy and ProTaper Gold groups.

CONCLUSIONS

The TruNatomy instrument group was more effective in preserving pericervical dentin compared with the other instrument groups. Coronal flaring files can be confidently used to preserve critical dentin during root canal treatment.

Endodontic treatment of a C-shaped mandibular second molar with narrow dentinal thickness: A case report

Formulating an effective root canal treatment plan necessitates clinician awareness of the complexities of the root canal system and possible anatomic challenges. The C-shaped canal variation accompanying the radicular lingual groove makes the lingual dentinal wall so thin that cleaning and shaping of canals require accurate management. This report presents endodontic treatment of a C-shaped mandibular second molar diagnosed with pulpal necrosis and asymptomatic apical periodontitis, that initial radiographic assessment revealed extremely thin (0.3 mm) width of the lingual wall of the canals prone to perforation. Mechanical preparation was performed through the anti-curvature technique and basically by chemical irrigation rather than mechanical instrumentation. The C-shaped isthmus was prepared up to 25/02 rotary system without dentinal defect while maintaining adequate dentin thickness so as to not significantly reduce the strength of the root. Follow-up radiographs showed normal periodontal ligament and lamina dura indicating significant healing of the periapical lesion.

Assessment of the root filling volume in C-shaped root canal on cone-beam CT and micro-CT in relation to nano-CT

AIM

To assess the observed volume of filled C-shaped root canals from different CBCT and micro-CT having nano-CT as a reference.

MATERIALS AND METHODS

Twelve extracted mandibular molars with C-shaped root canals were endodontically treated using Reciproc Blue R25 (VDW GMBH, Munich, Germany) in a reciprocating system and filled with gutta-percha (Dentsply Maillefer) and AH Plus sealer (Dentsply DeTrey, Konstanz, Germany). CBCT scans were performed using 3 units-3D Accuitomo 170 (J. Morita, Kyoto, Japan), ProMax 3D Max (Planmeca, Helsinki, Finland), and NewTom VGi EVO (Cefla QR, Verona, Italy)-at two resolution modes: standard and high. Micro-CT and nano-CT scans were also obtained. The volume of all filled C-shaped root canals was obtained using CTAn software (Bruker, Kontich, Belgium), and the blooming artifact, in relation to nano-CT volume, was calculated. The data were evaluated by the Bland-Altman plots and ANOVA two-way for repeated measures (α = 0.05).

RESULTS

All CBCT units and micro-CT showed significantly larger observed volume of root canal filling when compared to nano-CT. The blooming artifact of root canal filling in standard resolution was significantly larger than that in high resolution (p < 0.05) in all CBCT units.

CONCLUSIONS

Endodontic filling material with AH Plus sealer causes blooming artifacts in CBCT units and micro-CT.

CLINICAL RELEVANCE

Considering the anatomical complexity of C-shaped root canals and the challenges associated with endodontic treatment, CBCT is frequently recommended for follow-up evaluations. However, the presence of endodontic filling material can result in blooming artifacts that may potentially impact the accurate diagnosis of endodontic complications.

Microcomputed tomography analysis of the radicular residual dentin thickness in mandibular second molars after virtual fiber post placement: Identification of danger zones

STATEMENT OF PROBLEM

Mandibular second molars have variable root, pulp chamber floor, and radicular groove morphologies, potentially affecting residual dentin thickness and post placement suitability. However, an identification of the danger zones is lacking.

PURPOSE

The purpose of this in vitro study was to investigate the residual dentin thickness in the danger zone of mandibular second molars after virtual fiber post placement by using a simulation method based on microcomputed tomography (μCT).

MATERIAL AND METHODS

A total of 84 extracted mandibular second molars were scanned using μCT and classified according to root morphology (separate or fused) and pulp chamber floor morphologies (C-shaped, non-C-shaped, or no pulp chamber floor). Fused-root mandibular second molars were further classified based on the radicular groove type (V-, U-, or Ω-shaped). All specimens were accessed, instrumented, and rescanned with μCT. Two types of commercial fiber posts were also scanned. Clinical fiber post placement was simulated in all prepared canals by using a multifunctional software program. The minimum residual dentin thickness of each root canal was measured and analyzed by using nonparametric tests to identify the danger zone. Perforation rates were calculated and recorded.

RESULTS

Larger fiber posts decreased minimum residual dentin thickness (P<.05) and increased perforation rate. In regard to mandibular second molars with separate roots, the distal root canal exhibited a significantly higher minimum residual dentin thickness than the mesiobuccal and mesiolingual root canals (P<.05). However, no significant difference in minimum residual dentin thickness was found between the different canals in fused-root mandibular second molars with C-shaped pulp chamber floors (P<.05). Fused-root mandibular second molars with Ω-shaped radicular grooves had a lower minimum residual dentin thickness than those with V-shaped radicular grooves (P<.05) and demonstrated the highest perforation rate.

CONCLUSIONS

The morphologies of the root, pulp chamber floor, and radicular groove were correlated with residual dentin thickness distribution in mandibular second molars after fiber post placement. A comprehensive understanding of mandibular second molar morphology is essential for determining the suitability of post-and-core crown restorations after endodontic treatment.

Impact of several NiTi-thermally treated instrumentation systems on biomechanical preparation of curved root canals in extracted mandibular molars

AIM

To evaluate the shaping ability of several heat-treated nickel-titanium systems used to prepare root canals with moderate and severe curvature, in extracted mandibular molars, by micro-computed tomography, considering their variation in kinematics and design.

METHODOLOGY

Curved-mesial roots of mandibular molars were randomly selected and assigned into 4 balanced experimental groups (n = 10), established by determining homogeneous 3D parameters of volume and surface area: R-Motion (RM) size 30, 0.04 taper (RM; FKG Dentaire), Reciproc Blue (RCB) size 25, 0.08 taper (RCB; VDW GmbH), HyFlex CM (HFX) size 30, 0.04 taper (HFX; Coltène Whaledent) and XP-endo Shaper size (XPS) 30, 0.01 taper (XPS; FKG Dentaire). The volume of irrigation was established at 10 ml of 2.5% NaOCl. Throughout the entire root canal preparation procedures, the samples were fixed in a vice submerged in a container with water monitored at 37°C. Dimensional cross-sectional measures of area, perimeter, roundness, major/minor diameters and 3-dimensional (volume, surface area, structure model index - SMI) parameters as well as the smallest dentine thickness along the cervical and middle root thirds were evaluated by micro-CT. Data were analysed using analysis of variance and post hoc Tukey tests (α = 5%).

RESULTS

Reciproc Blue and XPS had significantly greater mean increases in cross-sectional area measurements, only in the middle third, when compared with RM and HFX (p < .05). RM, RCB and XPS had a similar increase in measurements of length and width of perimeter (p > .05), and HFX had significantly lower mean increases in perimeter values only when compared with XPS (p < .05). RCB and XPS had significantly greater mean increases in volume when compared with RM and HFX (p < .05). RM had a significantly lower difference in SMI after preparation, compared with RCB, HFX and XPS (p < .05). The smallest dentine thickness was observed after the use of RCB (p < .05), in the danger and safety zones.

CONCLUSIONS

XP-endo Shaper and RM had a shaping ability similar to that of instruments with larger tapers, achieved with less dentine removal in danger and safe zones in curved-mesial canals of extracted molar teeth treated on a laboratory benchtop.

FEATURES OF THE VARIATIVE MORPHOLOGY OF THE MANDIBULAR SECOND MOLAR USING CONE-BEAM COMPUTED TOMOGRAPHY IMAGING

OBJECTIVE

The aim: To characterize the variations in the anatomical structure of the second lower molar.

PATIENTS AND METHODS

Materials and methods: In order to determine the topography of the roots and root canals of the mandibular second molar, modern imaging methods were used: orthopan¬tomography and cone-beam computed tomography.

RESULTS

Case report: During the analysis of the orthopantomogram of the patient, the three-root morphology of the root system of 37 teeth was revealed. That is, three roots were clearly visualized. After detecting an atypical shape of the root system of the mandibular second molar in the panoramic image, the patient was offered to perform cone-beam computed tomography (CPCT) for diagnostic purposes. Analysis by cone-beam computed tomography showed the presence of four mature roots of normal length, which were arranged in the shape of a diamond.

CONCLUSION

Conclusions: The four-root configuration is considered a rare form for mandibular molars, but it should be considered in endodontic interventions and, if possible, in the planning of such interventions, use cone-beam computed tomography.