Permanent Mandibular Premolars Research Articles

Geometric Morphometric Shape Analysis of Mandibular Post-Canine Dentition

Background: Genetic and epigenetic alterations have significant impacts on the morphology of permanent mandibular premolars and molars. Geometric morphometry is a powerful technique, which can be utilized to identify specific landmarks that exhibit variation and that are associated with ancestry and dimorphism. Methods: The geometric and anatomic landmarks of mandibular premolars and molars were extracted from 3D digital replicas of diagnostic dental casts prepared for model analysis (n = 160). Tooth shape analysis was conducted using various techniques, including Procrustes superimposition, Procrustes ANOVA, discriminant function analysis, and the regression of shape over the centroid size. Results: Procrustes ANOVA showed that centroid size was not significantly different between the two sexes, but shape was significantly different in the two-cusp-type second premolars (p = 0.0035) and in the first/second molars (p < 0.001). The three-cusp type of the second premolars showed the highest degree of allometry, with 3.35%, followed by the mandibular second molars, with 3%, indicating that distal class types have a tendency to exhibit allometry. The distal and lingual components of the tooth showed more variability, and females tended to have sharper cusp configurations. Conclusions: This study shows how landmarks vary in permanent human post-canine dentition, a crucial finding for anatomic reconstruction and restorative dentistry. In particular, the molars and premolars of the mandible post-canine teeth are critical for achieving optimal masticatory efficiency and overall health. Additionally, a higher degree of allometry and the later formation of cusps correlate with greater shape variation, particularly on the distal and lingual sides. For precise restorative procedures, a thorough understanding of the anatomy of these teeth is required.

Comparative evaluation of remaining dentin thickness, canal centering ability and apical deformity between ProFit S3 and Protaper gold – A nano CT study

PurposeFor the root canal treatment to be successful, the root canal system must be cleaned and shaped, and must be gradually widened from the apical to the coronal region in order to preserve dentin thickness. ProFit S3 (Profit Dental, India) patented rotary file with variable taper design preserves dentin. The study employs ultra-high-resolution nano-computed tomography to assess the volumetric changes of two new rotary files in permanent mandibular premolars. Materials and methodsBased on inclusion and exclusion criteria, this in-vitro investigation used extracted premolars. Before the pre-operative scan, samples were made and the working length was determined using a high-precision nano-CT (SkyScan 2214, Bruker, Kontich, Belgium). A single skilled pediatric dentist used ProFit S3 (Profit Dental, India) and Protaper Gold (PTG; Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) to prepare the canals. Post-op scans were similar to pre-ops. For 3D root canal visualization and analysis, NRecon software was used to rebuild images. ResultsProfit S3 has a mean value of 0.65500 and Protaper gold 1.38800, indicating a significant range. Protaper gold followed Profit S3 in canal volume differential. The two rotating file systems differed significantly (p 0.05). ProFit S3 maintained mesiodistal and buccolingual dentin thickness at 4 mm, 8 mm, and 12 mm, followed by Protaper Gold. ConclusionsProFit S3 exhibited the lowest mean canal volume difference compared to Protaper gold. Unlike Protaper Gold, ProFit S3 offers a variable taper design that preserves root canal anatomy, peri cervical dentin, and dentin thickness.

An Evaluation of the Fracture Resistance of Endodontically Treated Teeth Restored With Two Types of Posts (Diamond Posts and Fiber Posts): An In Vitro Study.

The aim of this study is to compare the fracture resistance and the mode of failure of endodontically treated permanent mandibular premolars restored with two types of posts: diamond posts and glass-fiber posts. Fortyhuman mandibular premolars indicated for orthodontic extraction were collected for this studyand were similar in shape, size, and length. The teeth were sectioned horizontally, 1 mm above the cementoenamel junction.Root canal treatment was carried out on all specimens, and obturation was done by lateral condensation. The teeth were randomly divided into two groups. The post space was prepared in the first group to receive the diamond posts and in the second group to receive the fiber posts. A dual-cure resin material was used for cementing the posts and building up the cores. Then, they were subjected to a compressive load at a cross-head speed of 1 mm per minute and at an angle of 135 degrees to the long axis of the tooth until a fracture occurred using a universal testing machine. Fracture resistance and the mode of failure were assessed. The fracture above the acrylic block level was considered favorable, and the fracture below the acrylic block level was considered unfavorable. The data were analyzed statistically. The statistical analysis of fracture resistance between the two groups was carried out with a t-test. The statistical analysis for the failure mode of the teeth was carried out with a chi-square test. There was a statistically significant difference showing that the diamond posts had better fracture resistance when compared with glass-fiber posts, while there was no statistically significant difference in terms of the failure mode between the two posts. Within the limitations of this study, it can be concluded that diamond posts showed higher fracture resistance than glass-fiber posts. Glass-fiber posts showed more favorable failure modes but were statistically insignificant compared to diamond posts.

Dens Invaginatus of Mandibular Premolars and Maxillary Anterior Teeth: A Case Report in Three Brothers

Dens invaginatus (DI), also known as dens in dente, is a developmental anomaly of teeth with enamel and dentin layers folded into the pulp cavity. This case report is about three brothers without any systemic diseases or syndromes. They all have DI on the permanent mandibular premolars and permanent maxillary anterior teeth. Several teeth needed root canal treatment due to this dental anomaly. Some DI can be difficult to detect and can progress to severe cavities and periapical abscesses without notice. Most of these diseases were detected unexpectedly through radiographic examination.

Effectiveness of moringa oleifera leaf extract nanoparticles in cleaning smear layer on the apical third of root canal walls

Objective: To evaluate the cleanliness smear layer on the apical third of the root canal wall in teeth irrigated with 5% and 10% Moringa leaf extract nanoparticles. Method: Vitro experimental laboratory with posttest control group design. A total of 30 mandibular permanent premolars were decorated to an average tooth length of 13 mm. The teeth were divided into 5 groups, with 6 samples per group and each sample was irrigated with 5 ml for 5 minutes. Group I (negative control) irrigated with aquadest steril, group II (positive control) irrigated with NaOCl 5,25%, group III (positive control) irrigated with a combination of NaOCl 5,25% and EDTA 17%, group IV (test group) irrigated with Moringa leaf extract nanoparticles 5% and group V (test group) irrigated with Moringa leaf extract nanoparticles 10%. All samples were tested for cleanliness of the smear layer on the apical third of the root canal wall using CLSM. Result: Average score cleanliness of the smear layer on the apical third of the root canal wall the highest are groups IV and V but not significantly different from group III. Groups IV and V were significantly higher than groups II and I, while the lowest was group I. Conclusion: Moringa leaf extract nanoparticles 5% and 10% were effective in cleaning the smear layer on the apical third of the root canal wall. Keywords: Moringa oleifera, nanoparticles, smear layer, Confocal Laser Scanning Microscope

Evaluation of root and canal morphology of mandibular premolar amongst Saudi subpopulation using the new system of classification: a CBCT study

BackgroundThe clinician should have complete knowledge of the normal anatomy of the root as well as complexities in the root canal configuration for a better outcome, as missed or improper handling of the canal system can lead to the failure of an entire endodontic procedure. The present study aims to assess the morphology of roots and canals in permanent mandibular premolars in the Saudi subpopulation with a new classification system.MethodsThe present study includes 1230 mandibular premolars (645 first premolars and 585-second premolars) from 500 CBCT images of the patients, including retrospective data. iCAT scanner system (Imaging Sciences International, Hatfield, PA, USA) was used to obtain the images; scanning of 8 × 8 cm images was performed at 120 KVp and 5–7 mA with a voxel size of 0.2 mm. The new method of classification presented by Ahmed et al. 2017 was used to record and classify the root canal morphology, followed by recording the differences regarding the age and gender of the patients. Comparison of canal morphology in lower permanent premolars and its association with gender and age of the patients was done by Chi-square test/ Fisher exact test; the significance level was set at 5% (p ≤ 0.05).ResultsThe left mandibular 1st and 2nd premolars with one root were 47.31%, with two roots were 2.19%. However, three roots (0.24%) and C-shaped canals (0.24%) were reported only in the left mandibular 2nd premolar. The right mandibular 1st and 2nd premolars with one root were 47.56%, with two roots were 2.03%. The overall percentage of the number of roots and canals in the first and second premolars 1 PM 1 (88.38%), 2 PM 1 B 1 L 1 (3.5%), 2 PM B 1 L 1 (0.65%), 1 PM 1–2−1 (3.08%), 1 PM 1–2 (3.17%), 1 PM 1–2−1–2 (0.24%), 3 PMMB 1 DB 1 L1 (0.48%). However, the C-shaped canals (0.40%) were reported in right and left mandibular second premolars. No statistically significant difference was reported between mandibular premolars and gender. A statistically significant difference was reported between mandibular premolars and the age of the study subjects.ConclusionType I (1 TN 1) was the major root canal configuration in permanent mandibular premolars, which was higher among males. The CBCT imaging provides thorough details about the root canal morphology of lower premolars. These findings could support diagnosis, decision-making, and root canal treatment, for dental professionals.

Case report of an Afro-Caribbean adolescent with moderate hypodontia managed with a partial flexible denture

A 14-year-old male of Afro-Caribbean descent presented with moderate hypodontia, missing some of the permanent mandibular premolars and the lower central incisors, which was a rare finding. There were no apparent associated systemic or syndromic relationships. The main dental concerns were aesthetics, function and space maintenance until adolescent craniofacial bone growth had ceased. Thus, an initial intervention entailed provision of a unilateral removable partial flexible denture that was acceptable to the patient and provided a suitable aesthetic result for the young person. This approach was preferred to a ‘band and loop’ appliance proposed in the literature because the removable partial denture supported function and aesthetics. CPD/Clinical Relevance: Unilateral removable partial flexible dentures may be useful in mid-adolescent cases of hypodontia.

Dens Evaginatus of Bilateral Permanent Mandibular Premolars with Pulpal Involvement: A Case Report

Dens evaginatus (DE) is a rare developmental anomaly resulting in an extra cusp in teeth. This odontogenic malformation occurs during morphodifferentiation before the mineralization of hard tissue. We report an interesting case of an 11-yearold Asian boy who presented with acute pain and tooth mobility on permanent mandibular premolars due to bilateral DE. Radiographic evaluation revealed acute periapical radiolucency indicative of an abscess. Permanent mandibular right first premolar (an immature apex tooth) was treated with apexification while permanent mandibular left second premolar (a mature apex tooth) was treated with conventional root canal treatment. The differential treatments based on the degree of root formation led to favorable outcomes of preserving the teeth. Appropriate DE diagnosis is vital to timely treatments and positive prognosis while avoiding unnecessary extractions.

Comparative Assessment of Novel Collagen Cross-linking Agents on Push-out Bond Strength of Two Different Sealers: An In Vitro Study.

To assess the push-out bond strength and tubular penetration of resin-based and bioceramic sealers after employing two collagen cross-linking agents, namely, cashew nut shell liquid (CNSL) and epigallocatechin-3-gallate (EGCG) on sodium hypochlorite treated root canal dentin. Fifty human permanent mandibular premolars selected were decoronated at CEJ, this was followed by cleaning and shaping protocols, root canals were enlarged up to 20 sizes with 6% taper and were randomly divided into the following 5 groups with 10 samples each based on the cross-linking agent and the sealer: • Group I: Irrigation with saline (control). • Group II: Irrigation with cashew nut shell liquid followed by bioceramic sealer obturation. • Group III: Irrigation with cashew nut shell liquid followed by resin-based sealer obturation. • Group IV: Irrigation with EGCG followed by bioceramic sealer obturation. • Group V: Irrigation with EGCG followed by resin-based sealer obturation. Five specimens in each group were evaluated for push-out bond strength with the universal testing machine while the remaining five specimens in each group were evaluated for depth of sealer penetration by a scanning electron microscope (SEM). The data was recorded, tabulated, and statistically analyzed. The push-out bond strength was found to be maximum in the apical region in all the five groups followed by the middle third and coronal region. The maximum push-out bond strength was seen in group II followed by groups III and IV, and least in group V. The mean depth of tubular penetration of sealers was found to be effective in the coronal portion followed by the middle third while the apical third region showed the least depth penetration of sealers into the tubules. The maximum penetration of sealers was revealed in group V followed by groups III and IV, and least in group II. Within the limitations of this study, it can be concluded that push-out bond strength was found to the maximum in specimens irrigated with cashew nut shell liquid and obturated with bioceramic sealer. The maximum push-out bond strength was seen in the apical third of all root canals followed by the middle and coronal region. The scanning microscopic analysis revealed maximum mean tubular penetration in the coronal portion followed by the middle third and apical third. A greater penetration was seen in specimens irrigated with EGCG and obturated with hybrid sealer. Selection of sealers plays a pivotal role in the success of endodontic therapy. Leakage-related issues can compromise the bond strength enhancing the bond strength can be achieved through the addition of cross-linking agents.

Roots and Root Canals Characterization of Permanent Mandibular Premolars Analyzed Using the Cone Beam and Micro Computed Tomography—A Systematic Review and Metanalysis

This current paper aims to review the literature on the root canal configuration (RCC) and root structure of permanent mandibular premolars. To find the published scientific literature on the RCC of mandibular premolars up to July 2022, a systematic search of four electronic databases was performed. The studies were selected, rendering to a predetermined point of reference: "mandibular 2nd premolar", "root and canal system", "morphology of root and canal", "root and canal configuration", and "morphology", along with "anatomy" and "mandibular premolars". Cross-referencing along with screening through the bibliographies of the chosen articles resulted in the identification of further studies. In the current study, we examined 30 different articles, and we chose them based on the quality of research investigations. From 3471 retrieved studies, a total of 15981 mandibular 2nd premolars were observed in 30 studies. The mean JBI score for studies assessing the structure of the root, as well as the root canal of the mandibular 2nd premolar, was 7.78 ± 0.81. We have found a pooled prevalence of 91.82% for Vertucci class I root canal morphology and 78.63% pooled prevalence of single-rooted mandibular second premolar. A total of 8677 mandibular 1st premolars were observed in 22 studies. The mean JBI score for studies assessing the structure and anatomy of the root, as well as root canal of mandibular 1st premolar, was 7. 95 ± 0.85. We have found a pooled prevalence of 74.34% for Vertucci class I root canal morphology and 85.20% pooled prevalence of single-rooted mandibular 1st premolar. Mandibular first and second premolars were mostly single-rooted teeth (89.5-100%). The most frequently seen RCC is a 1-1-2-/2 (type V-Vertucci's), followed by 1-1-2-/1 (type IV- Vertucci's; type III-Weine's), and finally RCC 2-2-2-1 (type IV-Vertucci's; type III-Weine's). Presently, the imaging of CBCT is the most used research approach for studying Mn2Ps' structural characteristics.

To Compare and Evaluate the Shear Bond Strength of Sixth- and Seventh-generation Bonding Agents.

To compare and evaluate the shear bond strength of sixth and seventh-generation dentin bonding agents. Around 75 extracted permanent mandibular premolars were selected and assigned into two groups. The samples were cleaned, cavities were prepared, and the bonding agent was applied and stored in distilled water for 24 hours. Shear bond strength testing was done using a universal testing machine at the crosshead speed of 1 mm/minute. Data were analyzed statistically by one-way analysis of variance (ANOVA) and paired test. The greatest mean shear bond strength to dentin was exhibited by the sixth-generation dentin bonding agent due to the solvent present, which has a low concentration and low hydrophilicity than the seventh-generation. Sixth-generation adhesives showed significantly higher mean shear bond strength to dentin than seventh-generation adhesives. Bond strength values are gross assessing tools for evaluating the efficacy of restorative bonding materials to dentin. And as the shear bond strength is less technique sensitive to perform, it will highlight the strength at the bonded interface. Adyanthaya BR, Gazal S, Mathur M, et al. To Compare and Evaluate the Shear Bond Strength of Sixth- and Seventh-generation Bonding Agents. Int J Clin Pediatr Dent 2022;15(5):525-528.

Root and root canal morphology of permanent mandibular premolars in Saudi Arabian population: A literature review

Root and root canal morphology of permanent mandibular premolars in Saudi Arabian population: A literature review

APPLICABILITY OF TANAKA JOHNSTON METHOD ON PAKISTANI POPULATION


 
 
 Tanaka and Johnston method is commonly used to predict the sizes of unerupted canines and premolars at mixed dentition stage. The accuracy of this method varies among different populations. The aim of this study was to derive the new regression equations for Pakistani population. The study models of 200 patients were selected. The mesiodistal widths of the permanent mandibular incisors, all canines and premolars were measured. Regression analyses were used to derive new regression equations for Pakistani population. The estimated mesiodistal widths of the maxillary and mandibular canines and premolars derived through Tanaka and Johnston method were significantly greater than the actual measured mesiodistal width of these teeth. The Tanaka and Johnston prediction equation overestimated the mesiodistal widths of canine and premolars in Pakistani population. The new prediction equations derived from this study would be more accurate for Pakistani population.
 
 

Prevalence and correlation of C-shaped root canals of mandibular premolars and molars in Eastern Chinese individuals

The aim of this study was to investigate the prevalence, correlation, and differences of C-shaped root canals (CSRCs) morphology in permanent mandibular premolars and molars in Eastern Chinese individuals using cone-beam computed tomography (CBCT). A total of 8000 mandibular first premolars (MFPs), mandibular second premolars (MSPs), mandibular first molars (MFMs), and mandibular second molars (MSMs) CBCT images from 1000 patients (692 females and 308 males) were collected. The prevalence, correlation, bilateral/unilateral presence, the morphology of CSRCs, level of canal bifurcation, gender differences, and location of radicular grooves (RGs) were evaluated. The prevalence of CSRCs in MFPs, MSPs, MFMs and MSMs were 10.25%, 0.25%, 0.55% and 47.05%, respectively. The prevalence of CSRCs in MFPs of males was higher than that in females, while the prevalence of CSRCs in MSMs of females was higher than that in males (P < 0.05). The bilateral symmetry presence of CSRCs in MSMs was significant but not in MFPs, MSPs, and MFMs. RGs were predominantly found on the mesiolingual (ML) surface of premolars and the lingual surface of molars. There was a high prevalence of CSRCs in MFPs and MSMs in the Eastern Chinese population, but there was no correlation. The prevalence of CSRCs in MFPs and MSMs differ significantly by gender (P < 0.05).

Accuracy of dental calcification stages for the identification of craniofacial pubertal growth spurt: proposal of referral parameters.

This study primarily aimed to assess the accuracy of radiographic dental calcification parameters for the identification of specific craniofacial growth stages. Permanent mandibular canines, premolars, and second molars of 288 patients, from 6 to 15years old, were analysed on randomly selected panoramic radiographs, and categorised according to two calcification methods. Reproducibility analyses and data derived from panoramic records were correlated with the gold-standard method, as evaluated from lateral cephalometric teleradiographs. Accuracy tests were finally calculated, considering several cutoff points. Dental calcification methods showed "strong" to "almost perfect" intra- and inter-examiner reproducibility. Significant, although weak correlations were observed for all parameters. Canine and first premolar calcification stage 8 and second premolar and second molar stage 7 showed higher sensitivity rates for identifying the pubertal growth spurt period, as well as the stage F for these teeth. Canine and first premolar stages 10 and H obtained higher specificity rates for identifying the absence of post-pubertal period. The dental calcification parameters showed adequate reproducibility, in addition to significant correlations with cervical vertebrae stages. Radiographic dental calcification parameters used for the mandibular first premolar obtained high accuracy rates and were recommended for identifying specific craniofacial growth periods.

Unilateraly erupted mandibular supernumerary premolar with dilacerated root: A case report

A healthy 33 years old male was reported to the Department of Oral Medicine and Radiology, Sri Sukhmani Dental College and Hospital, Dera Bassi, Punjab, India whose chief complaint was the presence of irregularly placed tooth in the lower right back region of the mouth. His dental, medical and family history was not relevant. On Intraoral examination, an erupted supernumerary tooth was found lingual to first and second right permanent mandibular premolars. It was irritating the tongue as told by the patient, hence was decided to extract it. After extraction, the root of the supernumerary tooth was found to be dilacerated. This report presents a case of unilaterally erupted Mandibular supernumerary premolar tooth with dilacerated root, which is a rare condition.

Seçilen bir Türk popülasyonunda koni-ışınlı bilgisayarlı tomografi kullanılarak mandibular birinci ve ikinci premolarların kök kanal morfolojisi ve literatür taraması

Objectives: To investigate the root canal morphology of permanent mandibular premolars using cone-beam computed tomography (CBCT) in the selected population and to review previous studies regarding other selected Turkish subpopulations. Materials and Methods: The sample for this retrospective study included 1048 CBCT images of 672 females and 376 males representing 1613 mandibular first and 1461 second premolars. Pubmed and Google Scholar were used to search previous literature with selected keywords. Results: The incidence of single root in mandibular first and second premolars was 99.75% and 99.38%, respectively. Complex root canal anatomy was evident in the first premolars compared to second premolars and in males than females (p&amp;lt;0.05). Eight studies have previously evaluated the root canal anatomy of mandibular premolars of other Turkish subpopulations by clearing or CBCT images. The prevalence of 2 or more root canals was found between 5.80% - 39.50% in mandibular first premolars and 1.1% -29% in mandibular second premolars in these studies. Conclusions: More attention should be paid to the detection of additional canals during root canal treatment of mandibular premolars, especially in male patients. The symmetrical morphology of the premolars may guide the practitioners during the root canal treatment. Evaluation methods could affect the results regarding root canal anatomy.

The Effects of Short-Term Calcium Hydroxide Application on the Strength of Dentine

The purpose of this study was to see how a short-term application of calcium hydroxide affected the dentine strength of adult human permanent teeth. Materials and methods: We selected 15 disease-free permanent mandibular premolars extracted from humans. The root canals were prepared using rotary equipment and divided into three groups at random. In one group, the root canals were filled with a calcium hydroxide paste (RC Cal) and in another group the root canals were filled with a calcium hydroxide paste (NEO Cal). Canals of teeth in the control group were left empty. All teeth were stored in normal saline for 14 days and then coronal third root dentin cylinders were created by removing the crown and apical portions of the teeth. The compressive forces required to shatter the dentin cylinders were measured using an Instron machine (UNIVERSAL TESTING MASCHINE), and the data was analysed using the Anova test. Results: The calcium hydroxide-filled teeth had a considerably lower mean compressive force than the control teeth (P &lt; 0.005). Conclusion: Teeth that had been exposed to calcium hydroxide for 14 days needed less compressive force to shatter root dentin cylinders. Further research is needed to see if impact testing will provide similar results.

Root Canal Morphology of Mandibular First Premolars using Radiography: An in vitro study

Objective: The goal of this study was to document the Root Canal morphology of the first mandibular premolars using radiography.&#x0D; Materials and Methods: The trial took place at the LUMHS Operative Dentistry Department. Two hundred removed permanent mandibular first premolars that met all of the study's inclusion criteria were gathered from LUMHS Jamshoro/Hyderabad and nearby private dental clinics in Hyderabad. All debris, soft tissues, and calculus were removed from the teeth, which were then preserved in a 10% formalin solution. Each tooth's length was measured from the crown's tip to the root's apex. An removed tooth, on the other hand, was examined from all angles, including buccal, lingual, and proximal. Root concavities and grooves, as well as bifurcation and apical curvature, were found.&#x0D; Results: Comparison between both views showed 189 teeth have 1 root in and 186 have 1 canal in buccolingual view, while 182 teeth have 1 root and 179 have 1 canal in mesiodistal view. 11 teeth on buccolingual and 18 teeth on mesiodistal view showed 2 roots and 14 teeth on buccolingual and 21 teeth on mesiodistal view showed 2 canals. 110 teetj showed type I canal pattern.&#x0D; Conclusion: It is concluded that mandibular first premolar teeth have a wide range of radicular traits, with the majority of them having one root and one canal.

Morphological Assessments of Root Apex of Permanent Mandibular First and Second Premolars in a Turkish Population

There is no apical morphological data being available for mandibular first or second premolars in the Turkish population. The aims of the study were (I) to assess apical morphological data of mandibular first and second premolars in a Turkish population at a young-adult age range (II) to analyze potential correlations between the size and position of the apical foramina (AF). Extracted sound teeth were collected from an adult volunteer population as willing to donate. Morphological data were obtained from specimens using a stereomicroscope. The number, size, shape, and position of AF and frequency of accessory foramina were quantified. Mann-Whitney U and Spearman's rank correlation tests were performed (α=0.05). A total of 237 teeth were investigated. The majority of the specimens had one major AF. The frequency of major AF was between 1–3 for both groups. The median AF size in mandibular first and second premolars were 55,180 µm2 and 67,483 µm2, respectively. The majority of foramina shape was irregular for the mandibular first premolars whereas, was oval for the second premolars. The median location of AF with respect to the anatomic apex was 664 µm in mandibular first premolars and 677 µm in mandibular second premolars. The size and location of AF mostly overlap between the mandibular first and second premolars. The shape of the AF might be the only relevant variation concerning the apical morphology between the mandibular first and second premolars in young adults. The interaction between the size and location of AF in mandibular premolars of young adults seems not significant