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Female, Humans, Middle Aged, Mandible diagnostic imaging, Cone-Beam Computed Tomography, Magnetic Resonance Imaging, Radiography, Panoramic, Temporomandibular Joint, and Temporomandibular Joint Disorders

Purpose: The double coronoid process (DCP) is a very unusual feature in patient. The literature, which briefly describes just only one case. Being this a very unusual feature, the aim of the paper is to describe the finding, discuss the anatomic, radiological, and clinical characteristics of a DCP.
Methods: A 61-year-old-woman with no significant medical history, extraoral and intraoral examination was unremarkable. Following panoramic radiography (PR) for assessment of periodontal support and pre-implant planning suspicious radiopaque area in the mandibular notch on the left side was observed. Cone-Beam Computed Tomography (CBCT) and Magnetic resonance imaging (MRI) were subsequently performed.
Results: No signs and symptoms of syndromes or medical records with a relevant contribution to the DCP existence and the patient denied any type of facial trauma. CBCT image showed the structure found on the PR was indeed a DCP and it was not superimposed on the mandibular notch area, MRI was performed to investigate soft tissue components and temporomandibular joint (TMJ) or other alterations.
Conclusion: DPC is extremely rare with the only case reported in the literature within the same comparison parameters. In this case images revealed the muscles, articular surfaces and articular disc were well preserved, and no other alterations were found.
(© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Humans, Cone-Beam Computed Tomography methods, Prospective Studies, Retrospective Studies, Mandible diagnostic imaging, Mandible anatomy histology, and Surgery, Oral

Introduction: A foramen in the coronoid process of the human mandible is a recently identified anatomic variant. The authors in this script aim at presenting a detailed assessment of the coronoid foramen terming it as '''foramen of Nyer' (FN) based on the person first identifying it.
Methods: Mandibular cone beam computed tomography scans from a total of 2168 patients were evaluated on a prospective and retrospective scale for confirmation of the coronoid foramen after first identification over a panoramic radiograph.
Results: The coronoid foramen was found and confirmed in 96 (4.4%) patients. This script identifying the coronoid foramina of mandible becomes requisite research as a foundation for further analysis due to the scarcity of literature on this recent find.
Discussion: This anatomical-radiological study aims to explore the variant foramina using cone beam computed tomography while determining its prevalence and evaluating its variability in terms of unilateral, bilateral, or gender predilection and propose the significance of this unique anatomic finding.
Clinical Consequences: The lack of information about the presence of such variant foramina may lead to emergence of clinical morbidities such as increased risk of intra osseous hemorrhage and tumor spread due to presence of accessory blood vessels.
(© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Humans, Adult, Male, Female, East Asian People, Cephalometry methods, Mandible diagnostic imaging, Mandible anatomy histology, Cone-Beam Computed Tomography, Sex Characteristics, and Malocclusion, Angle Class I

Introduction: The morphology of the human face varies broadly, with genetic and environmental factors determining these variations. Examining variations in the 3-dimensional (3D) craniomandibular morphology and identifying related factors (eg, sex differences) are important in orthodontic clinics. This study observed shape variations in the 3D facial morphology of Japanese adults showing skeletal Class 1 malocclusion and examined the association of sexual dimorphism with shape variations.
Methods: Sixty cone-beam computed tomography images of Japanese adults (30 males and 30 females) with skeletal Class I malocclusion were employed. In each cone-beam computed tomography image, wire mesh fitting was conducted as previously described. A principal component (PC) analysis after Procrustes registration and the PC clustering method was conducted to observe the shape variations. A PC regression analysis was conducted to determine the sexual morphologic characteristics.
Results: Nine PCs depicting 62% of the morphology were determined. Four typical phenotypes were found, mainly related to mandibular protrusion (PC1) and the vertical divergence of the face (PC2). PCs related to sex determination were PC3 (robustness of the mandibular angle in males), PC5 (greater size and shape of the coronoid and mastoid processes in males), and PC7 (greater maxillary width in males), accounting for 16% of total variations.
Conclusions: The major shape variations in skeletal Class 1 subjects were related to nonsexual dimorphic characteristics (ie, mandibular protrusion and facial divergence). Sexual dimorphic characteristics were evaluated in detail and accounted for 16% of total morphologic variations.
(Copyright © 2022 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.)

Humans, Child, Retrospective Studies, Radiography, Panoramic methods, Bone Density, Mandible diagnostic imaging, Fractals, and Familial Mediterranean Fever diagnostic imaging

Aim: It was aimed to evaluate the bone microarchitecture of children with FMF in the city of Tokat, where the disease is highly prevalent, in Turkey, one of the countries where familial Mediterranean Fever (FMF) disease is the most common, using mandibular indexes and fractal dimension analysis on panoramic radiography.
Methods: In this retrospective study, the results were evaluated and compared using the mandibular cortical index (MCI), the mental index (MI), the panoramic mandibular index (PMI), and the fractal dimension analysis of six different regions (condyle, angulus, and interdental) on dental panoramic radiographs in 124 children with FMF and 124 healthy children. The data were analyzed using the IBM SPSS V23.
Results: The distribution of MCI in children with FMF was similar to the control group (p > 0.05). The mean MI (3.59) values in FMF patients were statistically higher than the control group (p = 0.016). No statistically significant difference was found in PMI between the patients with FMF and the control group (p > 0.05). No statistically significant difference was found between the mean fractal dimension (FD) values according to the groups (p > 0.05).
Conclusion: Trabecular bone microarchitecture of children with FMF is similar to healthy children. There is no correlation between the duration of colchicine use and bone microarchitecture.
(© 2022. The Author(s) under exclusive licence to Japanese Society for Oral and Maxillofacial Radiology.)

Humans, Male, Mandible diagnostic imaging, Mandible surgery, Mandible abnormalities, Computers, Zygoma diagnostic imaging, Zygoma surgery, Zygoma abnormalities, and Jaw Abnormalities

Congenital fusion of the jaws (syngnathia) is a rare facial malformation with an unknown etiology. This disease may vary in severity with adhesion of soft tissue and bony fusion. It can be anterior fusion, unilateral or bilateral fusion, and complete fusion. The main problem of these patients is the difficulty of airway maintenance and feeding, and the most common postoperative complication is the relapse of bony fusion. Here, we report a young male patient with bony syngnathia, involving bilateral fusion of the ascending ramus and body of the mandible with the maxillary complex. We performed bone isolation by computer-assisted preoperative planning and used an insertional temporalis flap to fix the wound surface to prevent refusion of bone.

Humans, Retrospective Studies, Mandible diagnostic imaging, Mandible surgery, Osteotomy methods, Cephalometry methods, Genioplasty methods, and Fractals

Background: It is aimed to investigate whether there was a difference in radiographic changes in the operational areas between genioplasty alone and genioplasty combined with mandibular advancement and to evaluate the fractal dimension (FD) to assess trabecular changes after genioplasty surgery.
Methods: Preoperative-(T0) and postoperative-(T1) panoramic radiographs of 26 patients without any complications who underwent genioplasty combined with bilateral sagittal osteotomy and mandibular advancement or genioplasty alone were selected. In the panoramic radiographs of both groups, the genial segment, mandibular angulus, and surgical osteotomy line were examined using FD. The box-counting method was used for FD evaluation.
Results: It was determined that FD values before and after treatment were similar in both groups for all regions where measurements were made. After surgery, the FD values of the middle region of the genial segment were found to be significantly lower than the other regions. At T1, the FD values at the osteotomy area were found to be significantly higher than those in the middle region of the genial segment.
Conclusion: Trabecular structure does not differ in patients undergoing genioplasty alone or in combination with mandibular advancement osteotomy. The middle region of the genial segment heals later than other regions.
(© 2023. The Author(s).)

Humans, Adult, Female, Temporomandibular Joint, Mandible diagnostic imaging, Mandible pathology, Alveolar Process pathology, Mandibular Condyle diagnostic imaging, Mandibular Condyle pathology, and Temporomandibular Joint Disorders pathology

Background: This study aimed to determine the differences among various volumes of condylar osseous patterns and the corresponding dentoskeletal characteristics based on the risk of temporomandibular disorder.
Methods: Craniofacial spiral computed tomography data of 60 Class II hyperdivergent female adults were divided into normal, resorptive, flattened, and osteophyte groups based on condylar osseous forms. The condylar volumes of each group were compared, and their correlations with the dentoskeletal characteristics were assessed in three dimensions. Pairwise least significant difference tests were used to examine individual pairwise differences between groups, and one-way analysis of variance was used to measure differences among multiple groups. Pearson correlation and Spearman rank correlation analyses were used to determine the correlation between condylar volume and dentofacial characteristics. Statistical significance was established at p < 0.05.
Results: The condylar volume in the normal group was significantly greater than that in the changed groups, with no significant differences between the subgroups. The decrease in condylar volume was associated with a retruded and clockwise-rotated mandible with shorter rami. Condylar volume was negatively correlated with overjet, the alveolar height of the lower anterior and posterior teeth, sagittal inclinations of the lower teeth, intermolar width of the mandibular first molars, and width between the corresponding alveolar crests.
Conclusion: Multiple three-dimensional dentoskeletal characteristics of Class II hyperdivergent female adults are correlated with condylar bony changes, regardless of the form. These results could be helpful in indicating potential pathological changes in the temporomandibular joint and in making proper treatment plans for these patients.
(© 2023. The Author(s).)

Humans, Adult, Mandible diagnostic imaging, Molar diagnostic imaging, Tooth Crown, Cone-Beam Computed Tomography methods, Molar, Third diagnostic imaging, and Tooth, Impacted

Background: The anatomical position of the mandibular third molars (M3s) is located in the distal-most portions of the molar area. In some previous literature, researchers evaluated the relationship between retromolar space (RS) and different classifications of M3 in three‑dimensional (3D) cone-beam computed tomography (CBCT).
Methods: Two hundred six M3s from 103 patients were included. M3s were grouped according to four classification criteria: PG-A/B/C, PG-I/II/III, mesiodistal angle and buccolingual angle. 3D hard tissue models were reconstructed by CBCT digital imaging. RS was measured respectively by utilizing the fitting WALA ridge plane (WP) which was fitted by the least square method and the occlusal plane (OP) as reference planes. SPSS (version 26) was used to analyze the data.
Results: In all criteria evaluated, RS decreased steadily from the crown to the root (P < 0.05), the minimum was at the root tip. From PG-A classification, PG-B classification to PG-C classification and from PG-I classification, PG-II classification to PG-III classification, RS both appeared a diminishing tendency (P < 0.05). As the degree of mesial tilt decreased, RS appeared an increasing trend (P < 0.05). RS in classification criteria of buccolingual angle had no statistical difference (P > 0.05).
Conclusions: RS was associated with positional classifications of the M3. In the clinic, RS can be evaluated by watching the Pell&Gregory classification and mesial angle of M3.
(© 2023. The Author(s).)

Humans, Image Processing, Computer-Assisted methods, X-Rays, Algorithms, Mandible diagnostic imaging, and Deep Learning

Many studies in the last decades have correlated mandible bone structure with systemic diseases like osteoporosis. Mandible segmentation, as well as segmentation of other oral structures, is an essential step in studies that correlate oral structures' conditions with systemic diseases in general. However, manual mandible segmentation is a time-consuming and training-required task that suffers from inter and intra-user variability. Further, the dental panoramic x-ray image (PAN), the most used image in oral studies, contains overlapping of many structures and lacks contrast on structures' interface. Those facts make both manual and automatic mandible segmentation a challenge. In the present study, we propose a precise and robust set of deep learning-based algorithms for automatic mandible segmentation (AMS) on PAN images. Two datasets were considered. An in-house image dataset with 393 image/segmentation pairs was prepared using image data of 321 image patient data and the corresponding manual segmentation performed by an experienced specialist. Additionally, a publicly available third-party image dataset (TPD) composed of 116 image/segmentation pairs was used to train the models. Four deep learning models were trained using U-Net and HRNet architectures with and without data augmentation. An additional morphological refinement routine was proposed to enhance the models' prediction. An ensemble model was proposed combining the four best-trained segmentation models. The ensemble model with morphological refinement achieved the highest scores on the test set (98.27%, 97.60%, 97.18%, ACC, DICE, and IoU respectively), with the other models scoring above 95% in all performance metrics on the test set. The present study achieved the highest ranked performance considering all the previously published results on AMS for PAN images. Additionally, those are the most robust results achieved since it was performed over an image set with considerable gender representativeness, a wide age range, a large variety of oral conditions, and images from different imaging scans.
(© 2023 IOP Publishing Ltd.)

Humans, Male, Female, Incisor diagnostic imaging, East Asian People, Root Canal Therapy, Mandible diagnostic imaging, Dental Pulp Cavity diagnostic imaging, Dental Pulp Cavity anatomy histology, Tooth Root diagnostic imaging, and Tooth Root anatomy histology

Background: Comprehensive understanding of the root canal system complexity is critical important for successful root canal therapy. A double root canal system may be present in permanent mandibular incisors with a variable incidence in different ethnic populations. Ignorance or improper management of this canal variation can lead to treatment failure. This in vitro study aimed to identify the anatomic features of root canal systems in the mandibular incisors in a Chinese population by using micro-CT.
Methods: A total of 106 permanent mandibular incisors (53 central incisors and 53 lateral incisors) were collected from a native Chinese population. The teeth were scanned by a micro-CT scanner and then reconstructed three-dimensionally. The canal configurations were detected by Vertucci's classification, and the number and location of the accessory canals were also identified. The long (D) and short diameters (d) of the main and accessory canals were measured and D/d ratio was calculated at different root levels (cemento-enamel junction [CEJ] level, mid-root level and 1, 2, 3 and 4 mm from the apex). The root canal curvatures in the double-canaled mandibular incisors were measured at the proximal view by using modified Schneider's method. Chi-square test or Fisher's exact test was used for comparison of occurrence rates. Comparison of means from multiple groups was performed by using one-way ANOVA and LSD post-hoc test.
Results: In regard to the occurrence of double root canals, gender difference was neither detected in the mandibular central (16.0% [male] vs 14.3% [female]; p = 0.862), nor in the mandibular lateral incisors (26.9% [male] vs 33.3% [female]; p = 0.611). Age group difference was also not detected in the mandibular central (p = 0.717) and lateral incisors (p = 0.521). The incidence of double root canals was 15.1% (8/53) in the central incisors, and 30.2% (16/53) in the lateral incisors, but the difference did not reach statistical significance (p = 0.063). The most frequent non-single canal type was the type III (1-2-1) (18.9% [20/106]), and the other types identified included 1 case of type II (2-1) and 3 cases of type V (1-2). The incidence of accessory canals was 17.9% (19/106), with a mean level of 1.92 ± 1.19 mm from the apex. The frequency of long-oval (2 ≤ D/d < 4) and flattened canals (D/d ≥ 4), as well as the mean value of D, d and D/d ratio increased from the apical 1 mm to the apical 4 mm level (the D/d ratio increased from 1.9 to 2.9 for the single canals, from 1.4 to 3.3 for the buccal canals and from 1.2 to 2.3 for the lingual canals), and the D/d ratio reached the peak at the mid-root level. Double curvatures were detected in 33.3% (8/24) of the buccal canals and 37.5% (9/24) of the lingual canals, and the difference has no statistical significance (p = 0.063). The degrees of the primary curvatures were 21.5 ± 7.1 degrees for the buccal and 30.1 ± 9.2 degrees for the lingual canals, and the degrees of secondary curvatures were 27.0 ± 11.4 degrees for the buccal and 30.5 ± 12.5 degrees for the lingual canals in the double curvatures. The degrees of the single curvatures were 14.2 ± 6.3 degrees for the buccal and 15.6 ± 6.0 degrees for the lingual canals. Significant difference was detected among above 6 groups of canal curvatures (p = 0.000), and severe curvatures (≥ 20 degrees) were more frequently detected in the double curved canals.
Conclusions: Double-canaled mandibular incisors were not uncommon in the Chinese population, and type 1-2-1 was the most frequent non-single canal type. Gender and age did not significantly impact the occurrence of a second canal in mandibular incisors. Long-oval and flattened canals were very common at different root levels and their incidence increased from apex to the mid-root level. Severe curvatures were frequently detected in the double canal systems, especially in those canals with double curvatures.
(© 2023. The Author(s).)

Adult, Humans, Adolescent, Young Adult, Middle Aged, Aged, Aged, 80 and over, Cross-Sectional Studies, Prevalence, Mandible diagnostic imaging, Mandible anatomy histology, Mandible surgery, Cone-Beam Computed Tomography methods, Dental Implants, and Spiral Cone-Beam Computed Tomography

Objective: Dental implant procedure is the most common way to restore missing teeth but also comes with several complications. Success rates for dental implants are expected to be good when proper diagnosis and planning, study of bone morphology and closeness of implant with vital structures, such as nerves and blood vessels, are made pre-surgery.
Patients and Methods: This cross-sectional study involved 636 adult patients, aged 18-80 years old, that came for dental implants in screening clinics or referred to specialty clinics in Jeddah, Saudi Arabia for the year 2019 to 2020. Instead of conventional Computed Tomography (CT), Cone Beam Computed Tomography (CBCT) X-Rays have been used to evaluate mandibular lingual concavities.
Results: Prevalence and measurement of lingual concavities were determined. Type U mandibles with a lingual concavity, were found to have a higher chance of lingual cortical plate but this may still vary on factors such as type of population and ethnicity. The typical finding in the mandibular posterior region is the lingual undercut.
Conclusions: CBCT is a great tool used to study mandibular lingual concavities and it is essential prior the installation of dental implant to prevent life-threatening complications.

Female, Humans, Aged, Radiography, Panoramic methods, Bone Density, Absorptiometry, Photon, Mandible diagnostic imaging, Osteoporosis, Postmenopausal, and Osteoporosis diagnostic imaging

Objective: The aim of this study was to investigate the diagnostic efficacy of the radiomorphometric indices of mandibular cortical width (MCW) and mandibular cortical index (MCI) of cortical erosion for osteoporosis screening in adults (≥40 years) and older adults (≥65 years) to determine whether adding a fracture risk assessment tool (FRAX) would improve efficacy.
Study Design: One observer measured MCW and assessed MCI on dental panoramic radiographs acquired for patients in the Tromsø study. These indices, alone and with FRAX scores, were evaluated for efficacy in predicting osteoporosis, which was diagnosed by bone density measurement at the femoral necks with dual-energy X-ray absorptiometry.
Results: MCW ≤3 mm and MCI indicating heavily eroded cortices (C3) had accuracies of 68.8% and 83.6%, respectively, in identifying osteoporosis. In females >65 years, MCW ≤3 mm and C3 produced higher sensitivities but lower specificities, with slightly lower accuracies (61.4% and 79.8%, respectively) compared with all females. The addition of FRAX scores >15% improved the accuracy of MCW ≤3 mm (81.7%) and C3 (87.9%), resulting in high specificity (86.6% and 95.4%). Combining MCW ≤3 mm or C3 with FRAX >15% increased the probabilities of detecting osteoporosis by increasing positive likelihood ratios.
Conclusions: MCW ≤3 mm or MCI C3, when combined with FRAX >15%, showed superior diagnostic efficacy, with high specificity in detecting females without osteoporosis.
(Copyright © 2022. Published by Elsevier Inc.)

Humans, Fractals, Cancellous Bone diagnostic imaging, Mandible diagnostic imaging, Periodontium diagnostic imaging, Radiography, Panoramic methods, and Aggressive Periodontitis diagnostic imaging

Objective: The aim was to perform fractal analysis (FA) to compare differences in trabecular microarchitecture in interdental and antegonial regions on panoramic radiographs in periodontally healthy patients and those with stage III/IV, grade C periodontitis, and to compare the effects of patient age and sex on FA results.
Study Design: Clinical and radiographic records from 33 periodontally healthy individuals and 28 individuals with aggressive periodontitis were obtained from the faculty archives. Three regions of interest (ROIs) were chosen bilaterally from interdental bone around the mandibular first molar and canine and the antegonial region. The mean fractal dimension (FD) values of the ROIs were calculated. Significance of differences was established at P < .05.
Results: FD values of all 3 ROIs in the periodontitis group were significantly lower than values in the control group (P ≤ .004). FD was not affected by patient age (P = .357) or sex (P = .216). There were no significant correlations between FD and age in either group (P ≥ .093). FD values differed significantly between sexes in only one ROI.
Conclusions: FA can effectively detect trabecular microarchitectural differences in patients with aggressive periodontitis compared to periodontally healthy individuals. This technique might be useful in predicting the susceptibility of patients to periodontal disease.
(Copyright © 2022 Elsevier Inc. All rights reserved.)

Pregnancy, Female, Humans, Autopsy, Mandible diagnostic imaging, Maxilla diagnostic imaging, Gestational Age, Ultrasonography, Prenatal methods, and Face diagnostic imaging

Objective: To describe and model the normal growth of fetal facial bones and angles.
Material and Methods: A total of 118 fetal CT scans obtained at 19 to 41 weeks gestation after in utero fetal death or late miscarriage were analyzed. CT scan was followed by autopsy and pathological examination and only fetuses free from brain disease or abnormal craniofacial development were included. The measurements were taken using software for frontal, sagittal and 3D reconstruction from native axial sections. The optimal plane for bone analysis was chosen and the measurements made by multiplanar reconstruction.
Results: There was a statistically significant increase (P<0.001) in all measurements regardless of gestational age (GA) except those of the mandibulo-fronto-maxillary angle (P=0.412), the naso-mandibulo-maxillary angle (P=0.828) and mandibular width (P=0.86). There was no significant difference according to fetal sex. Based on these results, the corresponding growth curves were created. The anteroposterior mandibular diameter (APD) was very strongly correlated with GA (R=0.926, P<0.001). The following equation: GA=(8.187×APD)+4.257 can be used to estimate GA with a confidence interval (CI) of±2.42. The same applies to maxillary width (MW) (R=0.922; P<0.001). The equation GA=(11.059×MW)+7.571 can be used to estimate GA with a CI of 2.17.
Conclusion: The growth of the mandible, maxilla, zygomatic bone and orbits was measured and the corresponding growth curves were established. Several measurements were strongly correlated with gestational age.
(Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Humans, Retrospective Studies, and Mandible diagnostic imaging

Competing Interests: Competing interests: None declared.

Female, Humans, Pregnancy, Case-Control Studies, Mandible diagnostic imaging, Retrospective Studies, Ultrasonography, Prenatal, Airway Obstruction, Micrognathism diagnostic imaging, Pierre Robin Syndrome diagnostic imaging, and Pierre Robin Syndrome surgery

Background: Pierre Robin Sequence (PRS) is characterized by micrognathia, glossoptosis, and upper airway obstruction. Early recognition and appropriate perinatal management is crucial for optimizing outcomes. This study aimed to evaluate 20-week fetal ultrasounds to determine if specific mandibular measurements could predict PRS diagnosis and disease severity.
Methods: A retrospective case-control study of 48 patients with PRS and gender-matched controls was performed. Medical records were reviewed for respiratory and surgical interventions. Three parameters to assess micrognathia were measured on mid-sagittal profile ultrasound images: frontal nasal-mental angle (FNMA), facial-maxillary angle (FMA), and alveolar overjet. Student's t-test and univariate logistic regression was performed. P ≤ 0.05 was considered statistically significant.
Results: Patients with PRS demonstrated a significantly smaller mean FNMA compared to the control group, 129.3 ± 8.6° and 137.4 ± 3.2°, respectively (p < 0.0001), as well as significantly smaller mean FMA, 63.2 ± 9.2° and 74.8 ± 6.1°, respectively (p < 0.0001). The PRS group also demonstrated significantly larger mean alveolar overjet compared to the control group, 3.9 ± 1.4 mm and 2.1 ± 0.9 mm, respectively (p < 0.0001). The odds of respiratory intervention increased among cases when FMA was <68°. Additionally, there was a significant difference in median overjet between patients with PRS who did and did not require respiratory intervention.
Conclusions: Mandibular features on the 20-week ultrasound can be measured to predict diagnosis and severity of PRS. This is an important first step to prepare for potential respiratory intervention at delivery to minimize perinatal hypoxia. Alveolar overjet, previously not described in prenatal ultrasound literature, is measurable and has utility in prenatal screening for PRS, as do FMA and FNMA.

Humans, Cross-Sectional Studies, Iran, Cone-Beam Computed Tomography, Dentin diagnostic imaging, Dentin anatomy histology, and Mandible diagnostic imaging

Background: Mandibular first molars appear to be the most commonly tooth subjected to a root canal treatment, therefore a better understanding of the anatomy critical zones for resistance of this teeth may decrease the treatment's failure rate. So, this study was conducted to evaluate the dentin thickness of the danger zone in mesial roots of mandibular first molars using cone beam computed tomography in an Iranian population.
Methods: In this cross-sectional study, 210 Cone Beam Computed Tomography acquisition of the mandibular first molars were collected from a radiology center in Qazvin. The dentin thickness of the mesial roots (mesiobuccal and mesiolingual canals) was measured from the furcation to 5 mm below. The relationship between the dentin thickness in the danger zone and parameters, like age, gender, placement side, root length, the curvature of the canal, canal type, presence of middle mesial canal, and distance between the orifices of the mesial canals was investigated. Frequency, mean and standard deviation for variables were calculated, and data analysis was done by SPSS using simple and multiple linear regression and Pearson correlation coefficient. Also, two-sample t -test was used to compare mesiobuccal and mesiolingual on two sides. The significant level was also considered at ( p < 0.05).
Results: The average minimum thickness of danger zone dentin was found to be 0.885 ± 0.259 mm in the mesiobuccal canal and 0.906 ± 0.206 mm in the mesiolingualcanal. Also, the minimum thickness of dentin in the mesiobuccal and mesiolingual canals in the range of 0 to 1 mm from the furcation was more than in other areas. There was no significant relationship between the minimum dentin thickness of the danger zone with gender, placement side, root length, canal type, and mesial canal entrance distance. But with increasing age, the thickness of dentin in the danger zone in the mesiolingualcanal increased significantly ( p = 0.008). It was also observed that with the increase in the curvature of the canal, the thickness of the dentin in the danger zone in the mesiobuccal canal decreased (moderately curved ( p = 0.008), severely curved ( p = 0.046)). In addition, the thickness of the dentin in the mesiobuccal and mesiolingual canal was less in the samples with the middle mesial canal ( p = 0.047, 0.044).
Conclusions: Less dentin thickness in the danger zone in the mesial roots of mesiolingual mandibular first molars was seen in younger patients in mesiolingual canal, with a greater degree of canal curvature in the mesiobuccal canal and teeth with a middle mesial canal. Therefore, it is suggested that large taper instruments should be used with more precision to prevent complications.
Competing Interests: The authors declare no conflict of interest. Luca Testarelli is serving as one of the Editorial Board Members and Guest Editors of this journal. We declare that Luca Testarelli had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to Marco Tatullo.
(© 2023 The Author(s). Published by IMR Press.)

Humans, Software, Algorithms, Anatomic Landmarks anatomy histology, Imaging, Three-Dimensional methods, and Mandible diagnostic imaging

Objective: To explore an efficient and automatic method for determining the anatomical landmarks of three-dimensional(3D) mandibular data, and to preliminarily evaluate the performance of the method.
Methods: The CT data of 40 patients with normal craniofacial morphology were collected (among them, 30 cases were used to establish the 3D mandibular average model, and 10 cases were used as test datasets to validate the performance of this method in determining the mandibular landmarks), and the 3D mandibular data were reconstructed in Mimics software. Among the 40 cases of mandibular data after the 3D reconstruction, 30 cases that were more similar to the mean value of Chinese mandibular features were selected, and the size of the mandibular data of 30 cases was normalized based on the Procrustes analysis algorithm in MATLAB software. Then, in the Geomagic Wrap software, the 3D mandibular average shape model of the above 30 mandibular data was constructed. Through symmetry processing, curvature sampling, index marking and other processing procedures, a 3D mandible structured template with 18 996 semi-landmarks and 19 indexed mandibular anatomical landmarks were constructed. The open source non-rigid registration algorithm program Meshmonk was used to match the 3D mandible template constructed above with the tested patient's 3D mandible data through non-rigid deformation, and 19 anatomical landmark positions of the patient's 3D mandible data were obtained. The accuracy of the research method was evaluated by comparing the distance error of the landmarks manually marked by stomatological experts with the landmarks marked by the method of this research.
Results: The method of this study was applied to the data of 10 patients with normal mandibular morphology. The average distance error of 19 landmarks was 1.42 mm, of which the minimum errors were the apex of the coracoid process [right: (1.01±0.44) mm; left: (0.56±0.14) mm] and maximum errors were the anterior edge of the lowest point of anterior ramus [right: (2.52±0.95) mm; left: (2.57±1.10) mm], the average distance error of the midline landmarks was (1.15±0.60) mm, and the average distance error of the bilateral landmarks was (1.51±0.67) mm.
Conclusion: The automatic determination method of 3D mandibular anatomical landmarks based on 3D mandibular average shape model and non-rigid registration algorithm established in this study can effectively improve the efficiency of automatic labeling of 3D mandibular data features. The automatic determination of anatomical landmarks can basically meet the needs of oral clinical applications, and the labeling effect of deformed mandible data needs to be further tested.

Male, Female, Humans, Adolescent, Young Adult, Adult, Middle Aged, Mandibular Condyle diagnostic imaging, Mandibular Condyle surgery, Mandibular Condyle anatomy histology, Prospective Studies, Mandible diagnostic imaging, Mandible surgery, Temporomandibular Joint diagnostic imaging, Temporomandibular Joint surgery, Cone-Beam Computed Tomography methods, Mandibular Reconstruction, and Spiral Cone-Beam Computed Tomography

Objective: This study aimed to evaluate the condylar positional changes following mandibular reconstruction with preservation of the condylar head using Cone-Beam Computed Tomography (CBCT). Also, to assess joint space changes and the overall volumetric space compared to the preoperative status.
Methodology: This prospective study included 30 patients (60 joints) subjected to unilateral mandibular resection and reconstruction with preservation of the condylar head. The Helkimo index and preoperative (T1), two weeks postoperative (T2), and follow-up CBCTs (T3) after at least six months were gathered and processed to evaluate the condylar position and TMJ joint space using Anatomage Invivo 6. A student's t-test and repeated-measures ANOVA statistics were used. A P value of less than 0.05 was considered statistically significant.
Results: Thirty patients (14 males, 16 females) with a mean age of 40.01 ± 12.7 years (a range of 18.1-62.9 years) were included. On the tumor side, there were significant variances in the vertical and mediolateral condylar positions between the three-time points (T1, T2, T3). Immediately after the operation, the condyles were significantly displaced in a downward direction at T2, which became larger after the last follow-up period (T3) (p = 0.007). The condylar positions at the anteroposterior direction were relatively stable without significant differences between the three times points (p = 0.915). On the non-tumor side, the condylar positions were relatively stable in the mediolateral and anteroposterior positions. In the tumor side, all of the TMJ spaces were significantly increased in size following the mandibular reconstructions (T2 and T3). However, on the non-tumor side, the anterior, posterior, and medial joint spaces were significantly changed postoperatively.
Conclusion: After mandibular reconstruction with condylar preservation, the condylar position and volumetric measurement immediately changed noticeably and continued to be a permanent change over time compared to relatively stable condyles on the non-tumor side. According to Helkimo index, patients become adapted to the postoperative changes without significant differences between the two sides.
(© 2023. The Author(s).)

Humans, Cross-Sectional Studies, Mandible diagnostic imaging, Mandible surgery, Mandible anatomy histology, Dental Implantation, Endosseous adverse effects, Dental Implantation, Endosseous methods, Cone-Beam Computed Tomography methods, Dental Implants adverse effects, and Spiral Cone-Beam Computed Tomography

Background: To explore the influence of cross-sectional type and morphological parameters at the mandibular molar sites on lingual plate perforation (LPP) during the immediate implant placement (IIP).
Methods: 181 implants were virtually placed in the mandibular molar sites on the cone beam computed tomography (CBCT). Each cross-section of the implantation site was divided into the Undercut (U)/Parallel (P)/Convex (C) types. Morphologically relevant parameters were measured on the cross-sections, including width of the upper end (Wb), width of the lower end (Wc), vertical height (V), angle between the natural crown axis and the alveolar bone axis (∠β), LC depth (LCD), LC height, and angle between the horizontal line and the line connecting the most prominent point and the most concave point of lingual plate (∠α). Besides, the distance from the end of the virtual implant and the lingual bone plate of the cross-section (D IL ) was calculated. Relationships between all the morphologically relevant parameters and the D IL were further analyzed.
Results: A total of 77 (42.5%) cross-sections were classified as U-type, which was the most common one, accounting for 63% of the second molar regions. All LPP cases and most of the nearly LPP (87.9%) cases occurred at the U-type cross-sections, and the relationship between the D IL and the morphological parameters can be expressed by a multivariate linear equation.
Conclusions: The occurrence rate of U-type cross-sections in the second molar region was very high, and the risk of LPP should be considered during IIP. Except for the U-type, significant large LCD, small Wc, and large ∠β were the important relevant factors. CBCT and multivariate linear equations could help to assess the LPP risk and provide a reference for implant placement design pre-surgery.
(© 2023. The Author(s).)