Dry Mandibles Research Articles

Incidence of retromolar canal in Egyptian population using CBCT: a retrospective study

BackgroundMany studies have been done to investigate the incidence and the course of the retromolar canal (RMC) in different populations either osseous studies using cadavers or dry mandibles, panoramic studies, or cone beam computed tomography (CBCT) studies. The location of the RMC is in the retromolar area distal to the third mandibular molar. The retromolar area is considered an imperative site where many dental surgeries are being held.The aim of this study is to determine the incidence of RMC in the Egyptian population using CBCT and measure the distance between the RMF and neighboring anatomical landmarks to better allocate the RMC and RMF and avoid the complications.Two hundred and fourteen CBCT scans were examined to detect the presence of RMC. Their course was classified to 3 main types A, B, and C, and linear measurements were done from the retromolar foramen (RMF) to the 2nd and 3rd molars in anteroposterior direction and from the RMF to the mandibular foramen (MF) in anteroposterior and mediolateral directions.ResultsThe RMC was present in 24 scans from the 214 with 11.2% incidence rate. The most common type was found to be type A, and type C was the rarest. The RMC has no significant difference between males and females, unilateral and bilateral distribution, and right and left sides. The linear measurements from the RMF to the 2nd and 3rd molars are 14.70 ± 5.07 mm and 4.26 ± 4.21 mm, respectively, and from the RMF to the MF in anteroposterior and mediolateral directions are 15.69 ± 3.43 mm and 2.62 ± 1.60 mm, respectively.ConclusionsThe incidence rate of RMC in Egyptian population represents 11.2%. The use of CBCT is quite important in the evaluation of the retromolar area to visualize the presence of the RMC or RMF and avoid the complications occurring due to different dental surgical procedures performed in the aforementioned site.

Incidence of the retromolar foramen in dry mandibles and its significance for dental surgical procedures

O forame retromolar, assim como o canal retromolar, são variações anatômicas da mandíbula que se apresentam na região do trígono retromolar. Esse forame e canal contêm estruturas neurovasculares que fornecem inervação adicional aos molares inferiores e à área bucal. Objetivou-se verificar a incidência e ocorrência entre os sexos do forame retromolar em mandíbulas da Coleção de Ossos Contemporâneos da Universidade Federal de Pernambuco. Foram analisadas 61 mandíbulas secas, sendo 37 masculinas e 24 femininas. Das 61 mandíbulas, 18 apresentaram o forame retromolar (29,5%), sendo 12 mandíbulas apresentando o forame unilateralmente (19,67%). As mandíbulas masculinas apresentaram uma maior incidência comparada às femininas, tendo totalizado 12 (32,43%) mandíbulas com forame retromandibular. A população analisada mostra uma alta incidência do forame retromolar, especialmente para o lado direito. A identificação dessa variação anatômica auxilia no planejamento de cirurgias e durante os procedimentos anestésicos.

Analysis of angle of mandible in dry human mandibles

Analysis of angle of mandible in dry human mandibles

Use of the metal artefact reduction tool in the identification of fractured endodontic instruments in cone-beam computed tomography.

To evaluate the influence of the metal artefact reduction (MAR) tool in the diagnosis of fractured instruments in root canals of extracted mandibular molars, with or without root canal fillings. The root canals of 31 mandibular molars were divided into four groups: (i) the control group, without root fillings; (ii) the fracture group, without fillings and with fractured files; (iii) the fill group, with root filling; and (iv) the fill/fracture group, root filled and with fractured files. The following instruments were used as fractured endodontic instruments: stainless steel hand files, NiTi reciprocating files and NiTi rotary files. Each tooth was inserted in a dry mandible to obtain cone-beam computed tomography (CBCT) images using a CBCT OP300 3D Maxio (Instrumentarium Dental, Tuusula, Finland) and Picasso Trio (Vatech, Hwaseong, Republic of Korea), with and without application of the MAR tool. All images were evaluated by three radiologists for the presence or absence of fractured files on a 5-point scale. The diagnostic accuracy (area under ROC curve) was calculated. Image noise was measured in regions of trabecular and cortical bone and soft tissue. The comparison between the ROC curve values with the MAR tool enabled or disabled was performed using a t-test. A t-test was also employed for comparing image noise when the MAR tool was enabled and disabled. The significance level was set at 5%. The use of the MAR tool did not influence the diagnostic accuracy for identifying fractured endodontic instruments in root canals with and without fillings in both CBCT systems (P>0.05), nor did it influence the image noise (P>0.05). The MAR tool on these two devices did not increase the detection of fractured endodontic instruments and did not reduce image noise using extracted mandibular molars. Therefore, the MAR tool is not recommended for evaluation of fractured endodontic instruments in teeth with and without root fillings in mandibular molars.

Is the inferior occlusal plane a reliable anatomic landmark for inferior alveolar nerve block? A study on dry mandibles of Brazilian adults

To investigate the relationship between the mandibular foramen (MF) and the inferior occlusal plane (IOP) of anatomic specimens, in order to guide clinicians in the inferior alveolar nerve block (IANB). Eighty-two dry mandibles (totally or partially toothed) of Brazilian adults were selected, totalizing 66left and 66right antimeres. A flat plate of rigid PVC plastic was placed on the occlusal surfaces of posterior teeth and pressure was then manually applied to simulate the IOP. Following, the perpendicular distance from the IOP to the lowest point of the MF was measured by the use of a digital caliper, adopting negative values inferiorly and positive values superiorly. Regarding the antimeres, the majority of the lowest limits of the MF was below the IOP (right: 86.4%, left: 81.8%) with a mean of -4.2mm (±4.8) in the right and -4.1mm (±4.8) in the left ones, without any statistical significance. Considering both sexes, no statistically significant difference was obtained between them. The IOP seems not to be a good anatomical landmark to localize the MF and, its turn, to guide clinicians during the IANB for Brazilian adults, given the marked topographic variations.

RELIABILITY OF 3-D-PRINTED MANDIBLES CONSTRUCTED FROM CONE BEAM CT VOLUMES OF DIFFERENT VOXEL SIZES

<h3>Background</h3> 3-D printing, also known as <i>additive manufacturing or rapid prototyping</i>, is a manufacturing process in which layers are sequentially added to create an object. 3-D printing is used in a wide variety of fields, ranging from dentistry and medicine to food manufacturing, toy manufacturing, house manufacturing, and automobile manufacturing and in the fashion industry. 3-D printed models can have a wide variety of uses in dentistry, ranging from anatomic models to surgical implants. <h3>Objective(s)</h3> The aim of the present study was to establish the reliability of linear cephalometric measurements made on mandibles and their respective 3-D printed models created from different voxel sizes in cone beam computed tomography (CBCT) scans. <h3>Study Design</h3> Ten dry mandibles were used for this study. All mandibles were scanned using the i-CAT FLX cone beam CT unit (Imaging Sciences International, LLC, Hatfield, PA) using voxel sizes of 0.30 mm, 0.25 mm, and 0.20 mm at 16 × 8 cm field of view and 360° rotation arc. The 3-D models were reconstructed and saved as STL files using 3-D Slicer software and sent to a 3-D printer for printing. Two observers measured the 10 mandibles and 30 3-D printed models. The measurements were repeated on 50% of the samples after at least 1 week. Cronbach's alpha and intraclass correlation coefficient were calculated to measure reliability. <h3>Results</h3> Good to excellent interobserver and intraobserver reliability were achieved across most of the measurements. There was no difference in reliability across models made from different voxel sizes. <h3>Discussion/Conclusions</h3> The present study successfully showed that the reliability of measurements made on 3-D printed models of dry skull mandibles created using the fused deposition modeling technique with images of different voxel sizes from an iCAT FLX CBCT machine are valid, reproducible, and reliable and can be used for diagnostic and clinical purposes.

Microsurgical Anatomy of the Superior Wall of the Mandibular Canal and Surrounding Structures: Suggestion for New Classifications for Dental Implantology.

Our goal was to clarify the relationship between the superior wall of the mandibular canal and the presence of teeth. We also sought to study the structural changes of the mandibular canal after tooth loss. Twenty sides from 10 dry mandibles derived from six males and four females were used for this study. The age of the specimens at the time of death ranged from 57 to 91 years. The mandibles were cut in the midline resulting in 20 hemi-mandibles. The presence of teeth (from the second premolar to the third molar) was recorded for each hemi-mandible. The mandibular canal in the body of the mandible was divided into four areas, that is, Areas 1-4. The superior wall of the mandibular canal and a cancellous bone pattern above the mandibular canal were observed. Next, the mandibular canal was horizontally cut at its center and the superior wall of the mandibular canal observed inferiorly. A total of 75 areas (20 dentulous areas and 55 edentulous areas) were produced. The distal view was classified into three groups, Type I (trabecular pattern), Type II (osteoporotic pattern), and Type III (dense/irregular pattern). The Type I pattern was found in 60.0% (12/20) of the dentulous areas and 32.7% of the edentulous areas. While the Type II pattern was found in 15.0% (23/55) of the dentulous areas and 41.8% of the edentulous areas. The inferior view was classified into four groups depending on the surface of the superior wall of the mandibular canal, that is, Class I (trabecular pattern), Class II (osteoporotic pattern), Class III (dense/irregular pattern), and Class IV (smooth).The Class I pattern was seen most frequently (55.0%) in dentulous areas and the Class IV pattern (45.5%) most frequently in edentulous areas. Based on these results, we conclude that the superior wall of the mandibular canal could change following tooth loss. Clin. Anat. 33:223-231, 2020. © 2019 Wiley Periodicals, Inc.

Influence of Cone Beam Computed Tomography Settings on Implant Artifact Production: Zirconia and Titanium.

This in vitro study assessed the artifact production related to titanium and zirconia implants in cone beam computed tomography (CBCT) and compared the effect of different protocol settings on image quality for both materials. A titanium implant and a zirconia implant were placed in a dry mandible. CBCT scans were obtained separately for each implant using the ProMax 3D (Planmeca) unit; 20 protocols were tested with varying kilovoltage (70 to 90 kVp) and resolution (high and low), and with and without a metal artifact reduction tool. Standard deviation and contrast-noise ratio were calculated in regions of interest adjacent and distant to the implant. The zirconia produced more artifacts and its images were more affected by the different protocols than titanium. High kVps and an activated metal artifact reduction tool decreased the standard deviation values related to both implants. Activation of the metal artifact reduction tool also increased contrast-noise ratio values for both implants, whereas increasing kVp improved them only on titanium images. The standard deviation and contrast-noise ratio were not affected by resolution. The zirconia implant generated more image artifacts than the titanium implant. Increasing kVp and the metal artifact reduction tool are efficient in decreasing the CBCT artifacts for both implants, whereas resolution does not affect their production.

Accuracy of two different voxel sizes for presurgical evaluation of mandibular osteotomy

The aim of this study was to compare the accuracy of two different voxel resolutions for the preoperative assessment of mandibular osteotomies. The study was conducted on 37 dry adult human mandibles. To obtain measurement standardization, heated gutta-percha cones were placed on the dry mandibles to mark 20 anatomical points. These cones were used for all measurement groups. Cone beam computerized tomography (CBCT) scans of the mandibles were made using 0.200mm3 and 0.400mm3 voxel sizes (Planmeca Promex-3D Helsinki, Finland). The results obtained from these two groups were compared with physical measurements obtained using a digital calliper, in order to analyze their predictive value. In the study, one voxel size did not have supremacy over the other in terms of accuracy. For mandibular osteotomies, 0.400mm3 voxel size can be preferred because of lower radiation dose.

Endosteal blood supply of the mandible: anatomical study of nutrient vessels in the condylar neck accessory foramina.

In the mandible, the condylar neck vascularization is commonly described as mainly periosteal; while the endosteal contribution is still debated, with very limited anatomical studies. Previous works have shown the contribution of nutrient vessels through accessory foramina and their contribution in the blood supply of other parts of the mandible. Our aim was to study the condylar neck's blood supply from nutrient foramina. Six latex-injected heads were dissected and two hundred mandibular condyles were observed on dry mandiblessearching for accessory bone foramina. Latex-injected dissections showed a direct condylar medular arterial supply through foramina. On dry mandibles, these foramina were most frequently observed in the pterygoid fovea in 91% of cases. However, two other accessory foraminaareas were identified on the lateral and medial sides of the mandibularcondylar process, confirming the vascular contribution of transverse facial and maxillary arteries. The maxillary artery indeed provided both endosteal and periosteal blood supply to the condylar neck, with three different branches: an intramedullary ascending artery (arising from the inferior alveolar artery), a direct nutrient branch and some pterygoid osteomuscularbranches.

Anatomical relation of third molars and the retromolar canal

The study was designed to assess, by direct anatomical observations and cone-beam computed tomography (CT), the prevalence of a retromolar canal and foramen in relation to the mandibular third molar in dry human mandibles. Dry mandibles from European skeletons (n=89) were observed directly and after cone-beam CT scanning (Newtom VGI evo). The following variables were assessed: the presence of a retromolar foramen and canal; the presence of a third molar, and orientation of the third molar. From the total of 89 mandibles selected, 73 showed a retromolar foramen (49 of which were bilateral). A retromolar canal was identified in 64 mandibles based on cone-beam CT assessment, with a total of 101 canals, including 74 that were bilateral. A total of 112 hemimandibles contained a third molar. Orientation of the third molar did not seem to indicate the presence of retromolar foramina or canals. A similar prevalence of retromolar canals was found for both vertically (41/79) and mesially (17/33) orientated third molars. A retromolar foramen and canal were present in most mandibles, with more than half being bilateral. We were unable to confirm a potential relation between the retromolar foramen and canal on the one hand, and the orientation of the third molar on the other.

Difference in the artefacts production and the performance of the metal artefact reduction (MAR) tool between the buccal and lingual cortical plates adjacent to zirconium dental implant.

To quantify the artefacts production and the performance of the metal artefact reduction (MAR) tool, enabled before or after the acquisition, in cortical plates (buccal and lingual) and other regions adjacent to zirconium implants. Cone beam CT scans were acquired using the OP300 Maxio unit before (control group) and after (implant group) the insertion of a zirconium implant into the posterior region of a dry mandible. Three conditions of MAR tool were tested: "without MAR", with "MAR activated after acquisition", and with "MAR activated before acquisition". The standard deviation (SD), contrast-to-noise ratio (CNR) and voxel values were calculated in the buccal and lingual cortical plates, medullary bone and water region, close to the implant. The structural bone analysis was performed in the medullary bone close to the implant. Overall, in control and implant groups, the lingual cortical had higher SD, lower CNR and lower voxel values than the buccal cortical, regardless of the MAR condition (p < 0.05). Implant caused higher SD values and lower voxel values in adjacent regions "without MAR" (p < 0.05). MAR activation decreased SD and changed voxel values when the implant was present, regardless of MAR activation mode (p < 0.05). The activation of MAR increased the trabecular thickness values for the implant group (p < 0.05). The expression of artefacts adjacent to zirconium implants is greater in the lingual than in the buccal cortical. The greater the expression of artefacts in this region, the greater the effectiveness of the MAR tool in homogenizing the grey values, regardless of the time of its activation.

CT imaging parameters for precision models using additive manufacturing

Additive manufacturing (AM), generally known as 3D Printing, is one of the manufacturing methods to develop medical models. The AM physical medical models are manufactured by virtual Computer-Aided Design (CAD) models. These CAD models are generated using medical scan data such as, Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), etc. In the process of CT data acquisition and transformation from CT to CAD data, dimensional and volumetric errors occur. In this work, the influence of several CT image reconstruction parameters on the 3D CAD model was evaluated experimentally. The dry mandible has been considered as a phantom from construction of a 3D CAD model. The linear dimensional and volumetric errors in the CT image reconstruction were compared from the dry mandible to the 3D CAD model of the CT images. Further, the CT image reconstruction parameters are optimized by Taguchi and Gray relational analysis methods. The optimized parameter of a 3D CAD model was used to develop STereo Lithography (STL) file and Fused Deposition Modeling (FDM) model by AM process. The scaling factor of each axis is determined by considering the ratio of STL to FDM model linear dimensions. Finally, the scaled STL model was manufactured by FDM technique and investigated that the dimensional error of the FDM model was minimized.

Cross sectional analysis of positional and numerical variations of mental foramina in dry human mandibles

Introduction: During lower jaw surgeries, mental nerve block is given at mental foramen level. However, mental foramen is prone for variations in its location and number, which could lead to iatrogenic injuries to neurovascular structures in this region. Aim and Objective: The aim of this study is to provide precise information of variations of site and number of mental foramen for helping dental surgeons to avoid injuries to mental nerve and vessels. Hence, the objective of the study is to analyze changes in site and number of mental foramen in the form of accessory foramina osteologically in Gujarat’s population. Materials and Methods: Three hundred dry mandibles of unknown sexes, and bearing all teeth or intact alveolar margin were included in the study. In 37.33% of mandibular sides, mental foramens were found between 2nd premolar and the 1st molar teeth. Numerical variations in the form of accessory foramina were found in 16.66% mandibles, more on the left side, showing statistically significant difference in laterality distribution. Conclusion: Iatrogenic injuries of mental neurovascular structures could better be avoided with precise idea of variations in site and numbers of mental foramen, which may ease the work of dental surgeon. Keywords: Dry mandibles, Mental foramen, Anaesthesia, Anatomical variation.

Diagnostic accuracy of cone beam computed tomography with different resolution settings for external root resorption

To evaluate the diagnostic accuracy of cone beam computed tomography (CBCT) with different resolution settings in detecting the simulated external root resorption defects. External root resorption defects were simulated in 51 human single rooted premolar teeth. Cavities simulating root resorption defects of 1 mm in diameter and 0.1 mm, 0.2 mm, and 0.3 mm in depth were drilled in the cervical, middle and apical thirds of lingual surfaces of the teeth. In addition to the 51 locations as controls, a total of 102 cavities were obtained in the present study. Specimens were placed in a human dry mandible and scanned by ProMax 3D and DCT PRO CBCT with different resolution settings, respectively. The three-dimensional CBCT images were evaluated by two experienced observers. The data were analyzed with receiver operating characteristics (ROC) analysis. ROC curves were generated and the area under ROC curve (Az) was employed to express the diagnostic accuracy. The diagnostic accuracy (Az value) of ProMax 3D CBCT with high, normal and low resolution settings were 0.867, 0.703 and 0.665 (P < 0.05), respectively. Defects with depths of 0.2 mm and 0.3 mm were easier to be detected than those with depths of 0.1 mm (P < 0.05). The images obtained by high resolution mode scanning had obvious advantages in detecting smaller defects (depth 0.1 mm and 0.2 mm). The DCT PRO CBCT provided 4 resolution settings including normal quality + normal resolution, normal quality + high resolution, high quality + normal resolution and high quality + high resolution. The Az values for those 4 resolution settings were 0.527, 0.725, 0.743, and 0.794 (P < 0.05), respectively. Similar to ProMax 3D CBCT, the scanning mode with high resolution played a better role in detecting the defects with depth of 0.1 mm. Except for the scanning setting mode with normal quality + normal resolution, the other three modes could well be evaluated for the defects with depth of 0.2 mm and 0.3 mm. It is concluded that the diagnostic ability for external root resorption of CBCT could be affected by resolution settings. Computer-aid imaging method can improve the CBCT diagnostic accuracy for external root resorption without increasing the radiation dose level during CBCT scanning.

Mandible: An Indicator for Sex Determination - A Three-dimensional Cone-Beam Computed Tomography Study.

Background:Mandible is considered as one of the stronger bones of skull available for gender identification. Mandibular measurements can be used for the identification of gender either on dry mandible or through panoramic radiography or cone-beam computed tomography (CBCT).Aim:To determine the gender from mandibular measurement using CBCT.Materials and Methods:The Morphometric analysis was performed on 200 CBCT scans of the subjects using OnDemand 3D software (Seoul, Korea). Morphometry of mandibular is measured by estimation of the angles formed at different locations on mandible to predict the gender. Statistical analysis was performed; independent samples “t-” test was used to compare the mean values between males and females. Discriminant function analysis was used for gender prediction.Results:The subject's age ranged from 18 to 60 years with an equal number of males and females. The mean angle formed by the intersection of lines from the left and right gonion to menton in males was 129.9 ± 11.9 and it was 126.7 ± 12.6 in females. The mean linear distances from the right gonion to menton in both males and females were 86.8 ± 5.3 and 82.6 ± 6.2, respectively. The mean linear distances from the left gonion to menton were 49.5 ± 5.1 in males and 47.7 ± 3.9 in females. The mean linear distance from the right gonion to left gonion was 47.7 ± 4.4 in males and 46.6 ± 4.2 in females. The Box's M statistics was applied to verify the applicability of mandibular measurements in gender prediction. The values indicate that gender can be predicted using these four variables, which is statistically significant (P = 0.000). The overall prediction accuracy of this model was 67%, with 66.7% in males and 67.3% in females being correctly classified.Conclusion:The angle formed by the intersection of lines from the left and right gonion to menton (Gn-M0) helps provide anthropological data, which can be used in dental and medicolegal practices.

Morphometric analysis of dry human mandibles - Application in inferior alveolar nerve block

Morphometric analysis of dry human mandibles - Application in inferior alveolar nerve block

Morphological study of various shapes of coronoid process of known sex in dry human mandible in Saurashtra region

Morphological study of various shapes of coronoid process of known sex in dry human mandible in Saurashtra region

Anatomical characteristics of the lingual foramen in ancient skulls: a cone beam computed tomography study in an Anatolian population.

The purpose of this study is to evaluate the anatomical features of lingual foramina and their bony canals in Anatolian ancient mandibles (9-10th century) by using cone beam computed tomography (CBCT). Fifty-eight ancient dry mandibles were scanned with CBCT. Lingual foramina were grouped into midline, paramedian, posterior foramina and combination of these groups. Midline group was also classified according to internal surface of the mandible (gonial tubercles [GTs]). The incidence, vertical distance and diameter of lingual foramina were measured according to age groups and gender. The incidence of the lingual foramen was 96.6%. Midline of the symphysis had the highest incidence (34.4%) of foramina (p < 0.05), followed by both midline and paramedian type (32.8%; p < 0.05). Classification in terms of GT represented class 3 as the most encountered group (28.6%). Number of foramina observed in the mandibles ranged from 0 to 6 with the incidence of 3.4% and 32.8%, respectively. The male and < 35 years groups presented larger measurement values in midline region (p < 0.05). Mandibular lingual foramina and bony canals are frequently present in ancient mandibles. When compared with modern subjects, similar findings are observed according to published literatures. CBCT is also proved to be an effective imaging modality in the detection of lingual foramina and canals in anthropological studies.

Determination of presence and morphometry of lingual foramina and canals in Chilean mandibles using cone-beam CT images.

To describe the presence and anatomical characteristics of lingual foramina and canals using cone-beam computed tomography (CBCT) in a sample of Chilean dry mandibles. Cone-beam computed tomography images of 68 adult mandibles of indeterminate sex and age were analyzed. The description of number and position of lingual foramina were tabulated using a position regarding the mental spines (superior, between, and inferior to the mental spines). Area and diameter of the foramina and length of the canals found were measured. All the mandibles had one or more lingual foramen. The median was 3 foramina with a minimum of 1 and a maximum of 4. The most frequent positions were superior and inferior with 88% and 85% of presence, respectively. The lingual canal diameter obtained for the superior position was 1.04 ± 0.38mm, for the between position was 1.02 ± 0.5mm, and finally 1 ± 0.3mm for the inferior position. The lingual canal length for the superior position was 6.38 ± 2.4mm, for the between position 6.77 ± 1.33, and 5.38 ± 0.25mm for the inferior position. All the mandibles have one or more lingual foramina. The most frequent positions were superior and inferior. Many of the lingual foramina found were over 1mm in diameter. The lingual canal length was over 5mm for all the positions.