Cancellous Bone Density Research Articles

Reliability of Grayscale Value for Bone Density Determination in Oral Rehabilitation using Dental Implants.

Quality and quantity of jaw bones have been previously classified in literature using different methods. Imaging modalities such as computed tomography (CT), successfully determine bone density of jaws. This study aims to establish the role of cone-beam CT (CBCT) in determining the density of cortical and cancellous bones at different jaw sites. Eighty-three possible implant sites in healthy patients were evaluated using NewTomGiano CBCT machine. Cross-sections were obtained and cortical and cancellous bone densities on different aspects of the virtual implant in terms of Hounsfield unit (HU) were determined using New Net Technologies software version 6.1 and were classified according to software from D1 to D4. Data were entered into SPSS software (version 19.0) and were statistically analyzed. The mean HU showed the highest value for cortical and cancellous in the anterior mandible (mean HU 1874.01 and 1131.73, respectively) followed by the posterior mandible (mean HU 1789.20 and 872.95, respectively) and least in posterior maxilla (mean HU 1068.26 and 830.04, respectively). Maximum D1 bone type was found in cortical bone and D2 bone type was noted in cancellous bone area. Males showed very highly significant cortical bone thickness (P < 0.001) whereas females showed more cancellous bone thickness but the results were nonsignificant. A high degree of concordance between different regions of jaw bones with a strong correlation between the four bone types was obtained. Bone density plays a pivotal role in determining the prognosis of the implant. CBCT has proven to be beneficial in bone density analysis.

Integrated Dose-Effect Relationship of Near-Infrared Light-Emitting Diode Light on Bone Regeneration in Disuse Osteoporosis Rats.

Objective: To examine the integrated dose-effect relationship of near-infrared (NIR) light-emitting diode (LED) light therapy in promoting bone defect repair in the rat model for osteoporosis (OP). Background: Low-intensity laser therapy has been shown to promote bone regeneration in OP rats. However, its integrated dose-effect relationship is not clear. Methods: Twenty-week-old male Sprague-Dawley rats were randomly assigned to 11 groups: (1) no-treatment control group (C group), (2) tail suspension (TS)-induced disuse OP experimental group (TS-OP group), and (3) OP rats with LED light treatment at nine dosages (L1-L9 groups). The tail of the rat was tied and suspended on the beam of the cage to suspend their hind limbs to induce bone loss for 4 or 7 weeks. The rats were then released and returned to their regular positions. An NIR LED at 810 nm was used on the bilateral hind limbs daily for 4 weeks. The C group rats were not given any treatment. The TS-OP group rats were subjected to identical procedures with L groups, with the exception that the light power was not turned on. After the experiment, the dual-energy X-rays or the microcomputed tomography scan analysis was performed to evaluate bone tissue status. Data analysis was done using SPSS and the health scale. Results: The trabecular thickness, trabecular number, bone volume/total volume, and connectivity density of cancellous bone and the biomechanical properties of femur in light groups were significantly increased compared with the TS-OP group, while the trabecular separation and structure model index were significantly decreased. Conclusions: NIR LED light therapy may promote trabecular bone repair of TS-OP rats. Light intensity influences photobiomodulation. In our dose levels, the greater the light intensity, usually the more effective.

New classification for bone type at dental implant sites: a dental computed tomography study

ObjectiveThis study proposed a new classification method of bone quantity and quality at the dental implant site using cone-beam computed tomography (CBCT) image analysis, classifying cortical and cancellous bones separately and using CBCT for quantitative analysis.MethodsPreoperative CBCT images were obtained from 128 implant patients (315 sites). First, measure the crestal cortical bone thickness (in mm) and the cancellous bone density [in grayscale values (GV) and bone mineral density (g/cm3)] at the implant sites. The new classification for bone quality at the implant site proposed in this study is a “nine-square division” bone classification system, where the cortical bone thickness is classified into A: > 1.1 mm, B:0.7–1.1 mm, and C: < 0.7 mm, and the cancellous bone density is classified into 1: > 600 GV (= 420 g/cm3), 2:300–600 GV (= 160 g/cm3–420 g/cm3), and 3: < 300 GV (= 160 g/cm3).ResultsThe results of the nine bone type proportions based on the new jawbone classification were as follows: A1 (8.57%,27/315), A2 (13.02%), A3 (4.13%), B1 (17.78%), B2 (20.63%), B3 (8.57%) C1 (4.44%), C2 (14.29%), and C3 (8.57%).ConclusionsThe proposed classification can complement the parts overlooked in previous bone classification methods (bone types A3 and C1).Trial registrationThe retrospective registration of this study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH 108-REC2-181.

Reconstructive Allograft Preparation for Long Bone Intercalary Segments After Tumor Resections: Toronto Sarcoma Protocol.

Reconstructive Allograft Preparation for Long Bone Intercalary Segments After Tumor Resections: Toronto Sarcoma Protocol.

Preoperative metaphyseal cancellous bone density is associated with intraoperative conversion to stemmed total shoulder arthroplasty

Methods to determine whether a stemless humeral component is appropriate for anatomic total shoulder arthroplasty are varied and often subjective. Objective preoperative data regarding metaphyseal bone quality may help guide surgical decision-making. This study sought to evaluate preoperative proximal humeral bone quality and determine whether it is predictive of intraoperative conversion to a stemmed humeral component. Consecutive patients who underwent primary anatomic total shoulder arthroplasty from a single-surgeon practice were enrolled. All patients received a preoperative computed tomography (CT) scan for surgical templating purposes. The exclusion criteria were lack of a preoperative CT scan, preoperative plan for a stemmed component, and intraoperative conversion to a stem for a reason other than bone quality (ie, fracture). Preoperative CT scans were analyzed with an automated templating software. Cortical index and thickness were calculated, and bone density of the proximal diaphysis, cancellous metaphysis, and cortical metaphysis was obtained by averaging Hounsfield units (HU) across anatomically defined regions using a previously validated technique. The decision to convert to a stemmed humeral component was made intraoperatively based on a lack of stability of the trial stemless component. Bone quality measurements were compared between stemless and stemmed groups. An exact logistic regression was used incorporating gender and age. A total of 79 patients who underwent primary anatomic total shoulder arthroplasty were included in this study. Of these patients, 6 underwent intraoperative conversion to a stemmed humeral component (7.6%). There was no significant difference between cohorts in terms of cortical index and bone density within the proximal diaphysis and cortical metaphysis. On univariate analysis, cortical thickness, metaphyseal cancellous bone density, and gender were significantly different between groups. Patients receiving a stem had significantly lower metaphyseal cancellous bone density than those receiving stemless components (5.5 ± 11.2 HU vs. 47.6 ± 29.4 HU, P<.001). All patients converted to stems were female individuals (P= .01) and had metaphyseal cancellous bone density less than 20 HU (P<.001). Metaphyseal cancellous bone density can be calculated on preoperative CT scans and is associated with intraoperative conversion to a stemmed humeral component in anatomic shoulder arthroplasty. A threshold of 20 HU can be used to predict which patients are more likely to require stemmed components.

Effect of inhaled corticosteroids on bone mineral density in patients with asthma.

Inhaled corticosteroids (ICS) are a safe treatment for asthma. However, at higher doses, ICS use has been reported to inhibit adrenocortical function. This study aimed to evaluate the effect of ICS on bone mineral density (BMD) in adult patients with asthma. Ultrasonic bone densitometry was performed in 40 patients (14 men, 26 women, mean age 61.2 years, mean duration of asthma 6.19 years) who were receiving ICS for asthma, and the whole bone density, thickness of cortical bone, and density of cancellous bone of the radius was measured. The age-matched mean was set as 100%. Lifetime cumulative dose of ICS was calculated using all past prescriptions. No significant correlations were observed between lifetime cumulative ICS dose and whole bone density (r² = 0.011), cortical bone thickness (r² = 0.022), and cancellous bone density (r² = 0.004). No significant differences were observed between lower and higher lifetime cumulative ICS dose among these BMD parameters (104% vs 97%, 103% vs 99%, and 106% vs 91%, respectively). No significant correlations or differences in lifetime cumulative ICS dose were observed by asthma severity, asthma duration, and pulmonary function. Also, serum markers of bone metabolism showed no significant correlations or differences with lifetime cumulative ICS dose. In the entire study population, long-term ICS use was safe and was not associated with an increased risk of osteoporosis.

Low-density lipoprotein receptor deficiency reduced bone mass in mice via the c-fos/NFATc1 pathway

AimThe low-density lipoprotein receptor (LDLR) plays a crucial role in regulating lipid metabolism. However, whether LDLR deficiency affects bone mass and morphology remains controversial. This study aimed to analyze the bone phenotypes of LDLR knockout (LDLR−/−) mice. Main methodsEight-week-old LDLR−/− and wild-type (WT) mice were subjected to microcomputed tomography to detect bone phenotypes. Enzyme-linked immunosorbent assay kits were used to detect the serum estrogen levels and matrix metalloproteinase 9 (MMP-9) levels in tissue homogenates. Von Kossa, toluidine blue, tartrate-resistant acid phosphatase (TRAP) staining, and calcein labeling were performed to explore bone turnover parameters. In vitro, osteoclastogenesis was induced in bone marrow cells from LDLR−/− mice and WT mice in the presence or absence of 17β-estradiol. The microphotographs and number of osteoclasts were validated using TRAP staining. Relative gene expression during osteoclast differentiation and maturation was determined by quantitative real-time polymerase chain reaction. Key findingsLDLR deficiency results in reduced bone mineral density of the tibial cancellous bone, indicating bone loss to some extent in LDLR−/− mice. LDLR deficiency significantly increased the number of osteoclasts, but not osteoblasts. In vitro, bone marrow cells from LDLR−/− mice displayed enhanced osteoclastic potential along with increased expression of TRAP, cathepsin K, nuclear factor of activated T-cells 1 (NFATc1), c-fos, and MMP-9 and inhibited dendritic cell-specific transmembrane protein expression. Moreover, 17β-estradiol treatment can inhibit osteoclastogenesis in vitro. SignificanceOur data demonstrated that LDLR deficiency promoted osteoclastogenesis by upregulating c-fos and NFATc1 expression, reducing cancellous bone mass in LDLR−/− mice.

Biomechanical analysis of printable functionally graded material (FGM) dental implants for different bone densities

The long-term success of a dental implant is related to the material and design of the implant, and bone density. Conventional implants cause stress-shielding due to a mismatch between the implant and bone stiffness. Functionally graded porous materials and designs are a great choice for the design of implants to control the local stiffness at a certain location to meet the biomechanical requirements. The purpose of this study is to analyze five designs of axial and radial functionally graded materials (FGM) implants besides the conventional implant and conical and cylindrical shapes that were simulated with five different bone densities. The results showed that strain in bone increased with a decrease in cancellous bone density. The shape of the implant did not play an important role in strain/stress distribution. Conventional implants showed optimal strain (1000–2240 με) in low-density (0.7–0.8 g/cm3) bone, however, FGM implants produced optimal strain (990–1280 με) in the high-density bone (0.9–1 g/cm3) as compared to conventional implants. The proposed designs of FGM implants have the potential to address the complications of conventional implants in high-density bone.

Bone resorption after maxillary reconstruction with the vascularized free iliac flap

The aim of this study was to evaluate the resorption of the iliac bone after maxillary reconstruction with a vascularized free iliac flap. Twenty-seven patients with maxillary defects who underwent maxillary reconstruction with the vascularized free iliac flap between January 2017 and January 2021 were included. Computed tomography (CT) images taken at 1 week, approximately 6 months, and 1 year after the surgery were used for evaluation. The total iliac bone thickness and height, cortical bone thickness, and cancellous bone density were measured in the CT images. Compared with 1 week after the surgery, the total thickness and height of the iliac bone were reduced significantly 1 year after the surgery, and the cortical bone thickness and cancellous bone density were reduced significantly at 6 months and 1 year after the surgery. Compared with 6 months after the surgery, cancellous bone density was reduced significantly 1 year after the surgery. In conclusion, during the first year after maxillary reconstruction with a vascularized free iliac flap, there was significant resorption of iliac bone, including the total iliac bone thickness and height, the cortical bone thickness, and the cancellous bone density.

Accuracy of an Apparatus for Measuring Glenoid Baseplate Micromotion in Reverse Shoulder Arthroplasty

Abstract Reverse shoulder arthroplasty (RSA) is used to treat patients with cuff tear arthropathy. Loosening remains to be one of the principal modes of implant failure and the main complication leading to revision. Excess micromotion contributes to glenoid loosening. This study sought to determine the predictive accuracy of an experimental system designed to assess factors contributing to RSA glenoid baseplate micromotion. A half-fractional factorial experiment was designed to assess 4 factors: central element type (screw versus peg), central element length (13.5 versus 23.5 mm), anterior-posterior peripheral screw type (locking versus nonlocking) and cancellous bone density (10 versus 25 pounds per cubic foot (pcf)). Four linear variable differential transducers (LVDTs) recorded micromotion from a stainless-steel disk surrounding a modified glenosphere. The displacements were used to interpolate micromotion at each peripheral screw position. The mean absolute percentage error (MAPE) was used to determine the predictive accuracy and error range of the system. The MAPE for each condition ranged from 6.8% to 12.9% for an overall MAPE of (9.5 ± 0.9)%. The system had an error range of 2.7 μm to 20.1 μm, which was lower than those reported by prior studies using optical systems. One of the eight conditions had micromotion that exceeded 150 μm. These findings support the use of displacement transducers, specifically LVDTs, as an accurate system for determining RSA baseplate micromotion in rigid polyurethane foam bone surrogates.

Maxillary and Mandibular Healing After Facial Allotransplantation.

Facial transplantation has emerged as a viable option in treating devastating facial injuries.Despite the high healing rate of Le Fort III and bilateral sagittal split osteotomies (BSSO) in nontransplant patients, few studies have reported assessment of maxillary and mandibular healing in face transplant patients compared with nontransplant patients. The aim of this study was to examine differences in bone healing in our patients. A retrospective chart review was conducted of facial allotransplantation patients at the Cleveland Clinic from December 2008 to inception. Demographics such as age, date of birth, and sex were recorded. Additional variables included procedures, revisions, reoperations, medications, and bone stability and healing. Computed tomography (CT) images assessed the alignment of skeletal components, bony union quality, and stability of fixation. Three patients were included: 2 had Le Fort III segment transplantation, and 1 had transplantation of both a Le Fort III segment and mandibular BSSO. The Le Fort III segment in all patients exhibited mobility and fibrous union at the Le Fort III osteotomy on CT. In contrast, the BSSO healed uneventfully after transplantation and revision surgery, with bony union confirmed by both CT and histology of the fixation area between the donor and recipient mandible bilaterally. No patients with midfacial fibrous union required revision of the nonunion as they were clinically asymptomatic. Le Fort osteotomy demonstrates inferior healing in facial transplantation compared with the nontransplant population. In contrast, the successful healing in the mandible is likely owing to the high density of rich cancellous bone.

Insufficiency fractures of the spine in relation to cancellous bone density : An in vitro study

HintergrundDas Risiko für osteoporotische Insuffizienzfrakturen (Fx) am Achsenskelett steigt mit zunehmender Abnahme der Knochendichte, wobei sich thorakal und thorakolumbal eine Häufung findet. Um die unterschiedliche Verteilung von Fx entlang der Wirbelsäule (WS) besser zu verstehen, wurden morphologische und osteodensitometrische Untersuchungen mittels Computertomographie (CT) in den verschiedenen WS-Abschnitten durchgeführt. Zudem war zu klären, ob die bei CT-Untersuchungen aus anderen Indikationen gefunden Hounsfield-Einheiten (HE) mit der Knochendichte korrelieren und Anlass für eine osteologische Diagnostik sein könnten.Material und MethodenVon 26 Körperspenden wurden die gesamten WS in einem Plexiglas-Wasser-Phantom fixiert und mittels hochauflösende Spiral-CT analysiert. Zusätzlich erfolgte die Messung der CT-morphologischen Spongiosadichte in HE von C3 bis S2 (624 Wirbelkörper). Der Knochenmineralgehalt (KMG, mg/ml) wurde ermittelt und zur Abschätzung einer Osteoporose (OPO) herangezogen.ErgebnisseBei allen WS lag eine OPO vor. Bei einem KMG unterhalb von 60 mg/ml fanden sich signifikant vermehrte Sinterungsfrakturen im thorakalen und thorakolumbalen Bereich. Osteoporotische Insuffizienzfrakturen im HWS-Bereich fanden sich insgesamt nicht. Die Spongiosadichte war signifikant höher in den zervikalen (Median 188,6 HE) als in den lumbalen (Median 63,6 HE) und sakralen (Median 25,5 HE) Wirbelkörpern aller untersuchten WS.SchlussfolgerungEin KMG-Verlust der Wirbelkörperspongiosa führt zu einem erhöhten Fx-Risiko, welches sich auch bei den verwendeten WS findet. Jedoch wird im zervikalen Bereich ein scheinbarer Schwellenwert für das Auftreten von Sinterungsfrakturen nicht unterschritten. Einen Schwellenwert für HE zu finden, wäre für die klinische Praxis relevant.

Preoperative Computed Tomography in Guiding the Length of Cannulated Screws in Medial Malleolar Fractures

Excessive lengths of partially threaded cannulated screws in medial malleolus fractures are often related to failure of fixation. This study aimed to analyze the distribution and density of cancellous bone in the medial malleolus among healthy individuals and provide a theoretical basis for determining the lengths of cannulated screws based on preoperative computed tomography (CT) to achieve stable fixation of medial malleolus fractures. Between January 2012 and December 2016, 100 patients (without ankle fractures) who underwent computed tomography of the distal tibia were included. Specific levels on the computed tomography images were selected to assess the density and length of valid cancellous bone in the medial malleolus. Meanwhile, we followed up 44 patients who underwent open reduction and internal fixation of medial malleolus fractures based on preoperative computed tomography-based measurements. The valid lengths of cancellous bone in the medial malleolus were significantly different between men and women (p < .05). In addition, there was a significant difference among different age groups (p < .05). All patients were followed up to union without displacement. Age and gender have a considerable impact on the distribution and density of cancellous bone in the medial malleolus. The density and length of valid cancellous bone decrease with age. The shoulder of the tibial plafond in medial malleolus, which is a weak part of cancellous bone, is a common site of fracture. Short screws are recommended for fixation in elderly patients. In conclusion, preoperative computed tomography can help determine the length and location of cannulated screws.

Evaluation of mandibular bone density in bruxers: the value of panoramic radiographs.

This study aimed to establish a difference in mandibular bone density between bruxer and non-bruxer patients, based on panoramic radiographs. Panoramic radiographs of bruxer and non-bruxer patients were analyzed with ImageJ®. Several radiological determinants were studied on the patients' panoramic radiographs: gray values of cancellous bone and cortical bone, and bony exostoses at the mandibular angle. Thirty-seven bruxers and forty-seven non-bruxers were included in the study. A statistically significant difference (p < 0.05) was noted in the cancellous to cortical bone ratios of bruxers and non-bruxers: the density of cancellous bone was greater in bruxers than in non-bruxers. The number of bony exostoses at the mandibular angle was significantly higher in bruxers (p < 0.05). This study obtained radiological determinants of bruxism from panoramic radiographs. Further studies are needed to supplement this preliminary approach, especially via the analysis of three-dimensional imaging to overcome the limitations of panoramic radiography.

Initial Assessments of a Handheld Indentation Probe's Correlation With Cancellous Bone Density, Stiffness, and Strength: An Objective Alternative to “Thumb Testing”

Abstract Objective: During shoulder arthroplasty, surgeons must select the optimal implant for each patient. The metaphyseal bone properties affect this decision; however, the typical resection “thumb test” lacks objectivity. This investigation's purposes were to determine the correlation strength between the indentation depth of a handheld mechanism and the density, compressive strength, and modulus of a bone surrogate; as well as to assess how changing the indenter tip shape and impact energy may affect the correlation strengths. Methods: A spring-loaded indenter was developed. Four tip shapes (needle, tapered, flat, and radiused cylinders) and four spring energies (0.13 J–0.76J) were assessed by indenting five cellular foam bone surrogates of varying density, every five times. After each indentation, the indentation depth was measured with a separate probe and correlated with manufacturer specifications of the apparent density, compressive strength, and modulus. Results: indentation depth plateaued as the bone surrogate's material properties increased, particularly for indentation tips with larger footprints and the 0.13 J spring. All tip shapes produced strong (R2≥0.7) power-law relationships between the indentation depth metric and the bone surrogate's material properties (density: 0.70 ≤ R2 ≤ 0.95, strength: 0.75 ≤ R2 ≤ 0.97, modulus: 0.70 ≤ R2 ≤ 0.93); though the use of the needle tip yielded the widest indentation depth scale. Interpretation: these strong correlations suggest that a handheld indenter may provide objective intra-operative evidence of cancellous material properties. Further investigations are warranted to study indenter tip shape and spring energy in human tissue; though the needle tip with spring energy between 0.30 J and 0.76 J seems the most promising.

368Evaluation of myostatin as a possible regulator of the skeletal muscle-cortical bone interaction in adults

Abstract Background Bone mass was recently reported to be related to skeletal muscle mass in humans, and a decrease in cortical bone is a risk factor for osteoporosis. Since circulating myostatin is a factor that primarily controls muscle metabolism, this study examined the role of myostatin in blood in bone mass-skeletal muscle mass interactions. Methods The subjects were 375 middle-aged community residents with no history of osteoporosis or sarcopenia who participated in a health check-up. The subjects were divided into those with low cortical bone thickness (LCT) or low cancellous bone density (LBD) and those with normal values (NCT/NBD). Bone metabolism markers (BAP, TRACP-5b, etc.), skeletal muscle mass, serum myostatin levels, and lifestyle, were then compared between the groups. Results The percentage of diabetic participants and blood HbA1c, TRACP-5b, and myostatin levels were significantly higher, and the frequency of physical activity, skeletal muscle mass, grip strength, and leg strength were significantly lower in the LCT group than in the NCT group. The odds ratio of high myostatin in the LCT group compared with the NCT group was significant (2.26) even after adjusting for related factors. Significant differences were observed in the same items between the LBD and NBD groups as between the LCT and NCT groups, with no significant differences in skeletal muscle mass and serum myostatin levels. The serum myostatin level was significantly negatively correlated with cortical bone thickness and skeletal muscle mass. Conclusions Myostatin may regulate bone-skeletal muscle interactions and serve as a surrogate marker of cortical bone metabolism. Key messages The interaction between bone and skeletal muscle is reported to be important for preserving the activity of bone and muscle metabolism. Herein, we report for the first time that myostatin may regulate bone-skeletal muscle interactions and serve as a surrogate marker of cortical bone metabolism in adults.

Eucommia ulmoides Polysaccharides Attenuate Rabbit Osteoarthritis by Regulating the Function of Macrophages.

Background and purpose:Eucommia ulmoides polysaccharides (EUP) can regulate the immunity of macrophages, but the functional status of macrophages is related to osteoarthritis and synovial inflammation. The purpose of this study is to explore whether EUP has the effect of inhibiting osteoarthritis and its possible mechanism.Methods: MTT test was used to evaluate the appropriate concentration of EUP and real-time quantitative polymerase chain reaction (RT-qPCR) was conducted to detect the effect of EUP on gene expression in RAW 264.7 cells. The osteoarthritis model was constructed by the anterior cruciate ligament transection (ACLT) in the rabbits. These rabbits were divided into three groups, sham operation group, OA group, and EUP group. The changes in articular cartilage were detected by gross observation and histological staining, and Micro-CT tested subchondral bone. Finally, the changes of macrophages in synovial tissue were studied by immunohistochemistry.Results: The results showed that EUP at the concentration of 50ug/mL and 100ug/mL were beneficial to the proliferation of macrophages. The qPCR results indicated that EUP inhibited the expression of inflammation-related genes IL-6, IL-18 and IL-1β, and promoted the expression of osteogenic and cartilage-related genes BMP-6, Arg-1 and transforming growth factor beta (TGF-β). The results of in vivo experiments suggested that the degree of destruction of articular cartilage in the EUP group was significantly reduced, and the Osteoarthritis Research Society International (OARSI) score was significantly reduced. Compared with the OA group, the subchondral cancellous bone density of the EUP group increased, the number and thickness of trabecular bone increased, and the separation of trabecular bone decreased. Synovial macrophage immunohistochemistry results manifested that EUP, on the one hand, reduced M1 polarized macrophages, on the other hand, accumulated M2 polarized macrophages.Conclusion: EUP can promote articular cartilage repair and subchondral bone reconstruction. The regulation of the polarization state of macrophages may be one of its mechanisms to delay the progression of osteoarthritis.

Computed tomography assessment of maxillary bone density for orthodontic mini-implant placement with respect to vertical growth patterns.

To quantitatively measure and report bone density of maxilla in the interradicular (alveolar and basal bone) and infrazygomatic crest (IZC) region in various growth patterns among Dravidian individuals. This was a retrospective spiral computed tomography (CT) study. The study was conducted at the Department of Orthodontics, Saveetha Dental College and Hospital, Tamil Nadu, India. Sixty CT scans (24 men, 36 women; mean age = 25.3 years and 23.8 years, respectively) divided equally into three groups based on vertical facial proportions were included. Bone density measurements in Hounsfield units (HU) were performed using Philips and RadiAnt DICOM viewers. Buccal cortical, palatal cortical and cancellous bone regions were analysed in a Philips DICOM viewer and IZC region was analysed in a RadiAnt DICOM viewer. Statistical analysis with one-way ANOVA and post-hoc Tukey HSD test was done. The hypodivergent group had a significantly higher bone density at the buccal cortex in posterior region (P < 0.05) when compared to the normodivergent and hyperdivergent groups. Buccal basal bone was denser than buccal alveolar bone (P < 0.05) in all three groups. In the IZC region, hypodivergent groups had significantly higher density values when compared to the normodivergent and hyperdivergent groups (P < 0.05). The present study concluded that cancellous bone density in the interradicular regions was greatest in the anterior sites and was not influenced by growth pattern. Hypodivergent groups tend to have higher density in the posterior regions (buccal and palatal cortical bone) and at the IZC region compared to normodivergent and hyperdivergent groups.

Characterization of Ultralow Density Cellular Solids: Lessons from 30 years of Bone Biomechanics Research.

Advances in additive manufacturing techniques have enabled the development of micro-architectured materials displaying a combination of low-density and lightweight structures with high specific strength and toughness. The mechanical performance of micro-architectured materials can be assessed using standard techniques; however, when studying low- and ultralow density micro-architectured materials, standard characterization techniques can be subject to experimental artifacts. Additionally, quantitative assessment and comparisons of microarchitectures with distinct lattice patterns is not always straightforward. Cancellous bone is a natural, ultralow density (porosity often exceeding 90%), irregular, cellular solid that has been thoroughly characterized in terms of micro-architecture and mechanical performance over the past 30 years. However, most the literature on cancellous bone mechanical properties and micro-structure-function relationships is in the medical literature and is not immediately accessible to materials designers. Here we provide a brief review of state-of-the-art approaches for characterizing the micro-architecture and mechanical performance of ultralow density cancellous bone, including methods of addressing experimental artifacts during mechanical characterization of ultralow density cellular solids, methods of quantifying microarchitecture, and currently understood structure-function relationships.

Studying the biomechanical effects of zirconia implant geometry and bone quality on the bone-implant interface using finite element analysis

The success of dental implants is influenced by several biomechanical factors such as implant design, bone quality, length of the implant, and the load transferred to the implant. The present studyaimsto determine the effects of bone quality, implant length, and bone type on stress/strain distribution in bone and implant for a zirconia implant. The study was performed using the three dimensional finite element analysis and four different lengths, two types of implants, and four different bone qualities. The Elastic modulus of a cancellous bone was varied to represent the four different bone qualities. A load of 100 N was applied at the center of the abutment. The result of this current work shows that a bone is subjected to the maximum equivalent stress and strain when the cancellous bone density decreased. The screw type implant induced lesser strain than the cylinder type load. The study also confirms that longer implants produced lesser stain than shorter implants, and type I, and II bones induced lesser stresses than type III, and IV bones. The importance of bone quality has been confirmed from this study, and zirconia dental implants have induced lesser stresses.