Mandible Cortical Bone Research Articles

Does the Miniscrew Length, Insertion Level, and Insertion Force Make a Difference on the Stress and Strain Distribution Across the Alveolar Bone? A Finite Element Study

Objective The aim of this study was to evaluate, using the finite element method (FEM), the stresses generated on various parts of the mini-screw and on the bone resulting from the insertion of mini-screws of varying lengths and under different forces. Materials and Methods Three-dimensional models of mini-screws (1.6 × 6, 8, and 10 mm) and bone (mandible cortical bone thickness of 2 mm) were constructed and simulated using FEM. The mini-screws were inserted using force loads of 10 and 20 Ncm, and stress evaluation was carried out on screws and bone. The stress evaluation was also performed across different levels of insertion (at the point of insertion, half-insertion, and full insertion). Results A direct correlation between the force applied and the stresses on the body of the screws was observed. There was an inverse relationship between the length of the mini-screw and the resulting stress on the bone with the highest stress of 14.58 Mpa with 6 mm long and the minimum stress of 3.81 Mpa with longer mini-screws. On application of different force magnitudes, the stress levels increased linearly with a change in the length. The highest stresses on the bone were observed only when the screw was fully inserted in the bone. Conclusion When mini-screws of different lengths were inserted using different magnitudes of forces, the stress levels increased linearly on the bone. A combination of longer mini-screw and lesser force magnitude used during insertion produced less stress on the bone.

Fractal analysis of the mandible cortical bone: correlation among fractal dimension values obtained by two processing methods from periapical radiograph and micro-computed tomography with cone-beam computed tomography.

The objectives of the present study were to assess Fractal Dimension (FD) values in the mandible cortical bone obtained from digital periapical radiographs (DPR), high-resolution microtomography (µCT), and cone-beam computed tomography (CBCT), by two processing methods: binarization (FD.b) and grayscale-based method (FD.f) and, finally, to identify the correlation among these values with other micro-architectural parameters. For this, a prospective study was conducted on 18 healthy individuals (mean age 23 ± 2.4years old) who underwent third molar extraction. Pre-operative CBCT scans were conducted, bone fragments were removed from the retro-molar region, and DPR and µCT were performed on those bone samples. FD.b and FD.f values were calculated using three parasagittal sections for CBCT, one image for DPR, and three sections for µCT. The 3D bone microarchitecture was analyzed in µCT (voxel size: 19µm). As a result, FD.b mean values of 1.55 ± 0.02 and 1.80 ± 0.01 were obtained for CBCT and µCT, respectively. Furthermore, FD.f mean values of 1.22 ± 0.12 for DPR, 0.99 ± 0.04 for CBCT, and 1.30 ± 0.07 for µCT were obtained. Both FD.b and FD.f values showed a good agreement. FD.f was negatively correlated with the standard deviation of the mean gray value (p = 0.003) for DPR and intra-cortical bone surface (p = 0.02) for µCT. In conclusion, image processing with or without binarization revealed different values for FD, although showing agreement. The grayscale-based method retrieved FD values correlated with the gray levels and the cortical porous network, which means that FD can be a valuable index for mandibular cortical bone evaluation. FD is associated with mineralization and microarchitecture. Nevertheless, there was no correlation between FD values obtained from low- (DPR) and high-resolution (µCT) X-ray modalities with FD obtained from the in vivo CBCT.

Investigation of a Modified Novel Technique in Bilateral Sagittal Splitting Osteotomy Fixation: Finite Element Analysis and In Vitro Biomechanical Test.

Purpose To evaluate the biomechanical properties of the modified novel 2-hole monocortical plate fixation (2HMCPf) and traditional 4-hole monocortical plate fixation (4HMCPf) techniques in bilateral sagittal splitting osteotomy (BSSO) synthesis using a finite element analysis (FEA) and an in vitro biomechanical test with the application of a shearing loading force on a sawbone mandible model. Materials and Methods A three-dimensional mandible models were generated using the geometry obtained from the computerized tomography image of a sawbone mandible. Plates and screws were generated and combined with the mandible in a CAD environment. The 2HMCPf and traditional 4HMCPf techniques for BSSO osteosynthesis were then analyzed under the occlusal load using the FEA. An in vitro biomechanical test was executed to verify the result of FEA. The force on fixation failure and pattern of failure were recorded. Results The results revealed that the von Mises Stress on the mandible cortical bone (75.98 MPa) and the screw/plate (457.19 MPa) of the 2HMCPf group was lower than that of the 4HMCPf group (987.68 MPa, 1781.59 MPa). The stress concentrated on the central region of the 4HMCPf group and the distal set of the 2HMCPf group. In vitro study using the sawbone mandible model showed mechanical failure at the region of the proximal segment near the osteotomy site with the 4HMCPf group (average 32.198 N) but no failure on the fixation sites with the 2HMCPf group. Instead, the mandible sawbone fractured on the condyle neck region (average 44.953 N). Conclusion From the biomechanical perspective, we proved that the 2HMCPf method was able to withstand a higher shearing loading force than the 4HMCPf fixation method in BSSO osteosynthesis.

Correlation between pixel value of CBCT and Hounsfield Unit of MDCT on teeth and mandible cortical bone

Cone-beam computed tomography (CBCT) is an imaging modality widely used in dentistry over multi detector computed tomography (MDCT). It is in view of its high resolution with relatively lower dose. MDCT is able to show Hounsfield Unit (HU) which is proportional to x-ray attenuation degree by the tissue. The x-ray attenuation degree in CBCT is shown in grayscale value with pixel values unit. The aim of this study was to determine the correlation of pixel values in CBCT with HU in MDCT. We used secondary data from RSGM Universitas Padjajaran patient who had CBCT and MDCT. Measurement was done on the cortical areas (lingual, buccal, and posterior side) of the mandible and teeth 47 (email, dentin, and pulp) with 5 regions of interest (ROIs) on each area. DICOM software was used for the measurement on CBCT and MDCT data. The result indicated a strong correlation between pixel value in CBCT and HU in MDCT on the cortical bone and teeth area (R=0.846). Linear regression resulted in an equation to derive HU value from pixel value of cortical bone and teeth area, which is y = 1,9011x + 177,15. The conclusion is HU can be derived from CBCT by converting with regression equation.

Evaluation of cortical mandibular bone in patients with oral squamous cell carcinoma.

The aim of the study was to evaluate the mandible cortical bone changes in patients with oral squamous cell carcinoma (OSCC). Twenty patients who underwent some mandibular bone removal as part of the treatment of OSCC had bone samples collected in two parts: in the proximity of the tumor (BPT) and in the surgical margin (BEP). Cortical microarchitecture was analyzed trough micro-computed tomography, together with texture analysis, followed by microcrack evaluation in histological sections and gene expression of RANK, RANKL, OPG, and sclerostin by quantitative polymerase chain reaction. Bone surface was higher in BPT (0.005±0.002 vs 0.004±0.002, p=0.01) compared with BEP. In BPT, the subset of patients without bone invasion presented higher anisotropy (0.83±0.07) compared with the ones with bone invasion (0.70±0.14) (p=0.04). RANK, RANKL, OPG, and sclerostin were found to be downregulated in the majority of cases in both parts. There were significant correlations between the parameters of microarchitecture and gene expression analysis (p<0.001 to p<0.05), most of them related with OPG levels. The cortex in the mandible in the proximity of the tumor reveals more bone surface than the bone in the surgical margin, and the tumor invasion causes a decrease in anisotropy. RANK, RANKL, OPG, and sclerostin are downregulated in mandible, in both parts analyzed. Correlation tests revealed the association between cortical thickness, bone surface, anisotropy, porosity, bone mineral density, and OPG levels. The mandible cortical bone microarchitecture changes in the proximity of the squamous cell carcinoma lesion.

Influence of Age and Gender on Mandible Among South Indian Population

The decrease of bone strength on ageing is a globally observed phenomenon among all human beings. The association between oral health and bone health has not been much researched among the Indian population. So, the proposed study was aimed to extract information about mandibular indices from dental panoramic radiographs and to identify its age and gender related changes among the south Indian population. The study involved 279 subjects, which included 103 men (46±11.55 years) and 176 women (47.2±12.49 years). The panoramic radiographs were obtained from a digital orthopantomogram scanner. The subjects were categorised into various decade age sub-groups for both the genders: 31-40, 41-50, 51-60, 61-70 and 71-80 years. The subjects were also further classified into three groups as: Normal, mild and severe based on the erosion of the endosteal margin of mandible cortical bone. The measurement of the Mandibular Cortical Thickness (MCT), Panoramic Mandibular Index (PMI) and assessment of the endosteal margin of the mandibular cortical bone was performed on the radiograph. The ANOVA test revealed a statistically significant difference for the MCT and PMI as (F = 6.98; p<0.001) and (F = 4.49; p<0.01) respectively between subjects of the various decade age sub-groups. The Chi-square tests revealed higher levels of significances (p<0.001) for the variations in the endosteal margin with age. The results of the study conclude that the MCT, PMI and the endosteal margin of mandible are age depended. The decrement of radiomorphometric indices was more prominent in females than males and they exponentially decreased after the sixth decade of age for both the genders. The MCT and PMI decreased by 6.41 and 4.8% respectively for males and by 23.2 and 30.8% respectively for females in the older groups.

Relationship between Preferential Alignment of Biological Apatite and Young^|^rsquo;s Modulus at First Molar in Human Mandible Cortical Bone

Biological apatite (BAp) crystallite c-axis alignment is known to be a factor in the mechanical function of bone. However, reports are lacking on mechanical properties in the alveolar area and base of the mandible area of the human mandible, which has complex occlusal force. In addition, there are many unclear mechanical properties concerning the relationship with BAp crystallite alignment. We therefore aimed to elucidate the relationship between BAp crystallite alignment and Young’s modulus in the alveolar area and base of the mandible area in human mandible cortical bone. The effect of occlusal force on bone quality at first molar in the mandible was also discussed.Mandibular specimens including teeth were obtained from 6 Japanese adult cadavers (mean age: 63.0 ± 12.1 years) housed at the Department of Anatomy, Tokyo Dental College. A microbeam X-ray diffraction system was used to determine BAp crystallite alignment along the mesiodistal direction (longitudinal axis) in each specimen. Young’s modulus was also measured at the same sites along the mesiodistal direction by nanoindentation and its relationship with BAp crystallite alignment examined.BAp crystallite alignment at first molar in human mandible cortical bone was low in the alveolar part but high in the base of mandible. The same tendency was observed for Young’s modulus at the same sites. Furthermore, a positive correlation was recognized between BAp crystallite alignment and Young’s modulus (p < 0.01).The present results showed a close relationship between BAp crystallite alignment and Young’s modulus, suggesting the importance of determining BAp crystallite alignment when evaluating bone strength. Determination of BAp crystallite alignment at first molar in human mandible may be useful in determining the effects of occlusal force.

Alignment of Biological Apatite Crystallites at First Molar in Human Mandible Cortical Bone

The aim of this study was to quantitatively clarify the c-axis alignment of biological apatite (BAp) crystallites (hereafter referred to as BAp alignment) in the cortical bone of the human mandible first molar. Six mandible specimens were collected from the cadavers of six dentulous Japanese adults (mean age, 63.0±12.1 years) held at the Department of Anatomy, Tokyo Dental College. A microbeam x-ray diffraction system was used to determine BAp alignment in the mesiodistal direction. Bone mineral density (BMD) was also measured using 3-dimensional trabecular structure measurement software. The results showed that the degree of BAp alignment in the mesiodistal direction was low in the alveolar area and high at the base of the mandible, suggesting that BAp alignment in the alveolar area is affected by occlusal force. Moreover, it was observed that the correlation between BAp alignment and BMD was small, indicating that BAp alignment and BMD could be independent factors. Therefore, determining BAp alignment was important in the evaluation of bone quality, including bone strength.

Anisotropic Wear Resistance of Human Mandible Cortical Bone

In order to evaluate the wear resistance, nanoscratch tests were conducted along different directions in the axial and the cross sections of mandible cortical bone, with the progressive loads from 0.1 to 80 mN. The morphology of scratch scars was showed via a field emission scanning electron microscope and an AMBIOS XP-2 stylus profilometer. The results indicated that the wear resistance of axial section was better than that of cross section. Furthermore, the wear resistance of axial section was affected by the different arrangement of lamellae. The wear degree was slighter when the scratches were conducted along the direction paralleling the osteon. The wear mechanism of cortical bone became more complicated with the increasing loads. It changed from the simple elastic–plastic deformation to the combination of deformation, delamination, and microcrack’s propagation.

Ameloblastoma Suggesting Large Apical Periodontitis

This case report describes the endodontic treatment of a large apical periodontitis with well-defined margins adjacent to teeth #22–24. After the initial endodontic treatment, continued expansion of the mandible cortical bone was observed, indicating a need to surgically enucleate the lesion and submit it for histopathologic examination. The microscopic examination indicated a diagnosis of ameloblastoma. Ameloblastoma is a benign epithelial neoplasm of odontogenic origin, and depending on the stage of development, it can mimic a periapical lesion and therefore should be considered in establishing an endodontic differential diagnosis. The definitive diagnosis for some periapical lesions can only be made by a histopathologic examination.