A micro-computed tomography study

OBJECTIVE

To evaluate and compare several anatomical parameters of mandibular first premolars from individuals from different Latin American countries using micro-computed tomography.

DESIGN

Five hundred extracted mandibular first premolars from Brazilian, Argentinian, Chilean, Colombian, and Ecuadorian individuals were scanned using micro-computed tomography (n = 100 teeth/country). Root canal configurations were classified according to established parameters. Analyses also included: canal volume and surface area, structure model index, distances from the apical foramen to the root apex or the cementoenamel junction, major/minor apical canal diameters, canal orifice shape, and prevalence of ramifications.

RESULTS

A single root was the most common anatomy in all countries (range, 97%-100%). Vertucci's type-I canal was the most frequent configuration (range, 36%-66%), followed by C-shaped and type-V canals. The oval-shaped canal orifice was the most predominant in all countries (range, 34%-58%), followed by the circular shape (range, 16%-47%). C-shaped canals occurred in all subpopulations (range, 14%-26%), always associated with radicular grooves. Ranges for canal ramifications were as follows: accessory canals, 36%-73%; lateral canals, 4%-12%; and apical delta, 4%-14% of the teeth. Many anatomic parameters differed significantly between countries (P < .05).

CONCLUSIONS

Vertucci's types-I and -V, and C-shaped canals were the most prevalent configurations in the subpopulations investigated. Accessory canals and several complex anatomies were found, with some significantly different frequencies between countries.

CBCT and Micro-CT analysis of the mandibular first premolars with C-shaped canal system in a Chinese population author

OBJECTIVES

The purpose of this study was to survey the prevalence of C-shaped root canal system in mandibular first premolar in Chinese population by reading Cone-beam computed tomography (CBCT) images and to analyze its anatomical characteristics by CBCT and Micro-computed tomography (Micro-CT).

METHODS AND MATERIALS

The prevalence and the morphologic features of C-shaped root canal system were evaluated by observing CBCT images of 760 patients (1520 mandibular first premolars). 66 mandibular first premolars with C-shaped root canal system were scanned by Micro-CT. The morphologic features including radicular groove, C-shaped root canal categories in the cross-sections and in the 3D models, accessory and connecting canals, apical foramina and accessory foramina, were analyzed using image software.

RESULTS

C-shaped root canal system was identified in 16.9% of mandibular first premolars. The minimum mesial wall thickness most commonly occurred at the lingual site (69.7%). Regarding to the cross-sectional classification, the maximum was C2 (41.5%). In the 3D classification, the most common was S (34.8%). Accessory canals were observed in 36.4% of the samples and occurred mostly in the middle and apical regions. 42.4% samples had 1-3 variable connecting canals, and 40.9% samples had only one apical foramen.

CONCLUSIONS

The incidence of C-shaped root canal system in mandibular first premolars was 16.9% in the Chinese population. The anatomy was very complex and variable, mostly distributed in the middle and apical regions of the root canal. The mesial wall of C-shaped canal was extremely thin on the lingual side.

Root canal narrowing patterns of mandibular first premolars on panoramic radiographs according to the number of root canals diagnosed on cone beam computed tomographic images

Understanding the variations in root canal morphology is important for successful endodontic treatment. Mandibular first premolars have a single root in 98% of cases, and multiple root canals are found in approximately 20% of cases. However, the details of these characteristic findings in panoramic radiography and their diagnostic accuracy are unknown. This study aimed to investigate the characteristic radiographic findings of mandibular first premolars possessing multiple root canals and determine the diagnostic accuracy using panoramic radiography. Four radiologists evaluated 347 mandibular first premolars in 186 patients who underwent panoramic radiography and dental cone beam computed tomography (CBCT). Two radiologists confirmed the existence of single or multiple root canals using CBCT. The remaining two radiologists evaluated the imaging findings of the root canal morphology and classified them into two patterns: gradual narrowing and sudden narrowing. In the case of the sudden narrowing pattern, the location of sudden narrowing was also evaluated. A gradual narrowing pattern was observed in 56% of teeth with a single root canal, and a sudden narrowing pattern was observed in 83% of teeth with multiple root canals. When sudden narrowing between the cervical and apical 1/4 of the root canal was used as the diagnostic criterion for multiple root canal teeth, the highest diagnostic performance was observed (sensitivity, 76.1%; specificity, 73.9%). The sudden narrowing between the cervical level and the apical 1/4 level of the root canal is a practical diagnostic criterion for mandibular first premolar with multiple root canals.

Preparation of the lingual canal in mandibular first premolar with canal bifurcation

The aim of this study was to establish an effective method of locating and negotiating the lingual canal in mandibular first premolars with two canals during root canal preparation. A total of 125 mandibular first premolars with radicular grooves were collected, and after micro-computed tomography scanning, 50 mandibular first premolars with a Vertucci V/III canal form were selected based on the inclusion criteria. Access cavities were prepared, and the lingual canals (LCs) were searched in four following steps: step 1 direct vision and a straight K-file; step 2 stereomicroscopy and a straight K-file; step 3 stereomicroscopy and a pre-curved K-file; and step 4 a long-neck bur. After localization, the LCs were instrumented. In most cases, access to the LC was achieved by step 2 (19/50, 38%) or step 3 (22/50, 44%). In three cases (6%), step 1 alone was enough to achieve access to the orifice, and in six cases (12%), access to the lingual canal was not achieved until step 4. Overall, 43 of the 50 mandibular first premolars (86%) were successfully instrumented, and the remaining seven failed. Two cases failed in the process of negotiating the canal to full length and five cases failed due to procedural errors (ledge formation, canal perforation, vertical fracture, or instrument separation). The LC in mandibular first premolars is a major endodontic challenge. A stereomicroscope and a pre-curved K file are suggested to be valuable tools for detecting and accessing the extra LC.

Occlusal Stress Distribution on the Mandibular First Premolar - FEM Analysis

OBJECTIVE

The aim of this paper was to analyze the distribution of stress and deformation on the mandibular first premolar under two types of loading (axial and para-axial load of 200 N) using the FEM computer method.

MATERIALS AND METHOD

For this research a µCT scan of the first mandibular premolar was used, and the method used in this research was FEM analysis under two types of loading.

RESULTS

The values of the von Mises stress measured in the cervical part of an intact tooth under axial load were up to 12 MPa, and under paraaxial load over 50 MPa. The values of the stress measured on the bottom of the noncarious lesion are very high ≈ 240 Mpa. Stress values in the cervical part of the intact tooth are higher in the zone of the sub-surface enamel. The deformation values of the tooth under para-axial loading were ≈ 10 times higher than the value of the deformation under axial load. The greatest deformations were seen in the area of the tooth crown.

CONCLUSIONS

Occlusal loading leads to significant stress in the cervical part of teeth. The values of the measured stress are greater under the action of paraxial load. The values of stress in abfraction lesions measured under a paraxial load are extremely high. Exposing the lesion to further stress will lead to its deepening. The total deformation of the entire tooth under paraxial load was ≈ 10 times higher compared to the deformation value of the tooth under axial load.

Methodological Approach to the Endodontic Treatment of First Premolars with Three Root Canals: Two Case Reports

AIM

The aim of this article was to promote a methodology in the endodontic management of complex premolars with multiple root canals Background: The success of endodontic treatment depends on a meticulous clinical and radiographic analysis, the creation of a suitable access cavity and chemical and mechanical preparation, followed by three-dimensional filling of the entire root canal system. Consequently, it is essential to look for the presence of additional root canals to prevent endodontic treatment failure Case description: Two cases are presented. The first case concerned a 50-year-old male patient of North African origin who consulted in the context of a global prosthetic restoration including endodontic treatment of the maxillary left first premolar (tooth no. 24). The second case concerned a 29-year-old male patient of North African origin who was referred to us by his primary care practitioner in an urgent context of pain and infection present for two weeks (tooth no. 44). In both cases, it was the in-depth radiographic analysis, combined with manual exploration under the surgical micro- scope, that led to the relatively rare identification of a third root canal. Shaping, disinfection and three-dimensional filling of the entire root canal system were then performed in accordance with widely validated protocols.

CONCLUSION

The maxillary and mandibular premolars, due to their highly variable root canal system configuration and a number of root canals and roots, appear to be teeth for which treatment is potentially complex. The acuteness of digital-tactile sense and the advent of 3D imaging and optical aids optimize the treatment of all the root canals of a tooth Clinical significance: These case reports demonstrate the importance of clinical and radiographic inspections to guide practitioners in the search for additional root canals in premolars and promote a methodological approach.

Canal configuration of mandibular first premolars in an Egyptian population

The purpose of this study was to investigate canal configuration of mandibular first premolars in an Egyptian population. Two hundred fifty human extracted mandibular first premolars were collected from Egyptian patients and a small hole in the center of the occlusal surface of each tooth was made perforating the roof of the pulp chamber. Teeth were decalcified by immersing in nitric acid and dehydrated in ascending concentrations of ethyl alcohol. A waterproof black ink was passively injected from the occlusal hole into pulp system and stained teeth were immersed in methyl salicylate solution for clearing. Standardized pictures of the cleared teeth were obtained and anatomical features of the root canal were observed. The average length of the mandibular first premolar teeth was 22.48 ± 1.74 mm, one-rooted teeth were 96.8% and the two-rooted were 3.2%. Vertucci Type I canal configuration represented the highest percentage (61.2%) followed by Type V (16.4%), Type IV (13.2%), Type II (5.6%) and Type III (2.8%). Vertucci Type VI canal configuration represented the lowest percentage (0.4%) and a complex configuration was found in one tooth. Accessory canals were detected in 22.8% and inter-canal connections were observed in 24.8% while 54% showed apical delta. Such knowledge is clinically useful for localization and negotiation of canals of mandibular first premolar, as well as their subsequent management in Egyptian population.

Root canal morphology of mandibular first premolar in a gujarati population - an in vitro study

BACKGROUND

Knowledge about root canal morphology and its frequent variations can exert considerable influence on the success of endodontic treatment. The aim of this study was to survey the root canal morphology of mandibular first premolar teeth in a Gujarati population by decalcification and clearing technique.

METHODS

One hundred thirty eight extracted mandibular first premolar teeth were collected from a Gujarati population. After decalcifying and clearing, the teeth were examined for tooth length, number of cusps and roots, number and shape of canal orifices and canal types.

RESULTS

The average length of mandibular first premolar teeth was 21.2 mm. All the teeth had 2 cusps. One hundred thirty four teeth (97.1%) had one root, and just 4 teeth (2.89%) had two roots. Mesial invagination of root was found in 21 teeth (15.21%). One canal orifice was found in 122 teeth (88.4%) and two canal orifices in 16 teeth (11.59%). Shape of orifices was found to be round in 46 teeth (33.33%), oval in 72 teeth (52.17%) and flattened ribbion in 20 teeth (14.49%). According to Vertucci's classification, Type I canal system was found in 93 teeth (67.39%), Types II,III,IV,V,and VI in 11 teeth (7.97%), 5 teeth (3.62%), 4 teeth (2.89%), 24 teeth (17.39%), and 1 tooth (0.72%) respectively.

CONCLUSION

Mandibular first premolar teeth were mostly found to have one root and Type I canal system.