Layer Of Bone Research Articles

Mimicking osteochondral interface using pre-differentiated BMSCs/fibrous mesh complexes to promote tissue regeneration

The heterogeneous nature of osteochondral tissue requires the construction of implant with biomimetic gradients. Electrospun fibrous meshes with different designs provide the feasibility in arranging such a kind of gradient structure via layer-by-layer stacking. In this study, a kind of triphasic implant was constructed by layering pre-differentiated cell sheets, which were hold by electrospun poly(L-lactide)/gelatin (PLLA/Gel) fibrous meshes containing hyaluronic acid and chondroitin sulfate for the cartilage layer or hydroxyapatite for the bone layer. As for the calcified interlayer, the bone marrow mesenchymal stromal cells (BMSCs) seeded on PLLA/Gel fibrous mesh was pre-differentiated with a mixed osteoinductive/chondroinductive (1:1) medium. With this gradient construct being implanted in rabbit knee osteochondral defect, it was found that both the cartilage and subchondral bone were regenerated effectively with reproduced tidal line structure. The importance of implants with biomimetic gradients for osteochondral defect repair was confirmed, and cell sheets on electrospun fibrous meshes were flexible for gradient structure construction via the layer-by-layer stacking technology. Highlights Composite fibrous meshes with tissue-specific components are electrospun. Confluent BMSCs on fibrous meshes are chondrogenically or osteogenically induced. BMSCs hypertrophy is induced with the mixture of chondroinductive and osteoinductive medium. The pre-differentiated cell/mesh complexes are stacked layer-by-layer to form gradient construct. The gradient construct efficiently promotes osteochondral regeneration in rabbit joint.

Analysis of tissue electrical properties on bio-impedance variation of upper limps

Upper limb loss has a significant impact on individual socioeconomic life. Human-machine interface (HMI) using surface electromyography (sEMG) establishes a link between the user and a hand prosthesis to recognize hand gestures and motions which allows the control of robotic machines and prostheses to perform dexterous tasks. Numerous methods aimed to enhance hand gesture and motion recognition toward an HMI. Bio-impedance analysis (BIA) is a noninvasive way of assessing body compositions and has been recently used for hand motion interpretation using `brute force? pattern recognition. The impedance variation in the body mostly depends on the precise stimulation using appropriate electrical features of the associated tissue layers. It has been reported that the electrical properties of these layers varied significantly. Thus, it is essential to investigate the influence of these variations on the stimulator design for the hand motion interpretation. This may not be possible using experimental approaches. Alternatively, using highly advanced computational models, this can be readily investigated by attaining the available range of the electrical properties of each tissue layer and applying appropriate boundary conditions and simulation settings. The computational models are composed of a volume conductor of the human arm model and electrode settings. Also, two different computational study methods were used to determine the influence of the tissues? dielectric properties on the results. The quasistatic approximation was used by only considering the resistivity of the anatomical layers and the transient simulation was used to analyze the capacitive impact on the results. Finite element (FE) models were developed to simulate the potential distribution inside the skin, muscle, and bone layers of the upper arm for given electrode settings. Then, simulation results were recorded for various electrical properties and different study types. It was shown that the capacitive influence of the tissue may not be ignored for certain conditions due to significant variation in the induced electrical potential variation along with the target muscle. Also, the influence of the individual tissue?s electrical properties was investigated using a set of dielectric parameters. The results showed that the skin and muscle layers have a significant impact on the electrical potential variation across the muscle length.

A 3-Dimensional Printed Patient-Specific Surgical Guide to Facilitate Transsphenoidal Hypophysectomy in Dogs.

ObjectiveHypophysectomy in dogs is a difficult surgery that requires specific learning and training. We aimed to evaluate the accuracy of a 3-dimensional printed patient-specific surgical guide to facilitate choosing the entry point in the basisphenoid bone before approaching the sella turcica during transsphenoidal hypophysectomy in dogs.MethodsTwo canine cadavers and 8 dogs undergoing transsphenoidal hypophysectomy for Cushing's disease treatment, involving design and fabrication of a 3-dimensional printed guide. The ideal entry point in the basisphenoid bone outer cortical layer was determined in each dog pre-operatively; its anatomical location was described with a set of measurements then compared to post-operative computed tomography measures describing the location of the outer cortical window created in the basisphenoid bone.ResultsSeveral guide designs were proposed, and a consensus reached based on surgeons' experience performing hypophysectomy. The device chosen could be applied to the size and shape of skulls encountered in this case series. The pre-planned measurements were comparable to post-operative measurement (there was also no statistical difference), with median of differences <0.1 mm, which we judged as clinically acceptable.Clinical SignificanceHypophysectomy in dogs is a challenging procedure that has a learning curve and needs to be performed by specialist neurosurgeons. We propose that a low-profile 3-dimensional printed surgical guide can aid the specialist neurosurgeon to locate the burring site of the outer cortical layer of the basisphenoid bone at a pre-defined location and with good accuracy. It does not alleviate the need to understand the anatomy of the region and to know how to create a slot within the basisphenoid bone, which remains essential to enter the sella turcica. This device could help specialist veterinary neurosurgeons wishing to be trained to perform hypophysectomy.

Age- and sex-specific normative values of bone mineral density in the adult glenoid.

The objective of this study was to determine the normative bone mineral density (BMD) of cortical and trabecular bone regions in the adult glenoid and its dependence on the subject's age and sex. We analyzed computed tomography (CT) scans of 441 shoulders (310 males, 18-69 years) without any signs of glenohumeral joint pathology. Glenoid BMD was automatically quantified in six volumes of interest (VOIs): cortical bone (CO), subchondral cortical plate (SC), subchondral trabecular bone (ST), and three adjacent layers of trabecular bone (T1, T2, and T3). BMDwas measured in Hounsfield unit (HU). We evaluated the association between glenoid BMD and sex and age with the Student's t test and Pearson's correlation coefficient (r), respectively. The lambda-mu-sigma method was used to determine age- and sex-specific normative values of glenoid BMD in cortical (CO and SC) and trabecular (ST, T1, T2, and T3) bone. Glenoid BMDwas higher in males than females, in most age groups and most VOIs. Before 40 years old, the effect of age on BMD was very weak in both males and females. After 40 years old, BMD declined over time in all VOIs. This BMDdecline with age was greater in females (cortical: r = -0.45, trabecular: r = -0.41) than in males (cortical: r = -0.30; trabecular: r = -0.32). These normative glenoid BMD values could prove clinically relevant in the diagnosis and management of patients with various shoulder disorders, in particular glenohumeral osteoarthritis and shoulder arthroplasty or shoulder instability, as well as in related research.

Peri-Implantitis: A New Definition Proposal Based on Unnatural Spatial Arrangement and Late Mechanical Coupling between Two Cortical Bone Layers during Osseointegration Phase Part II

To date, the term peri-implantitis has been mostly associated with bacterial or foreign body reaction as primary factors of its development. Because of this, researchers’ and clinicians’ attention regarding treatment possibilities were directed into the solutions on the basis of surface modifications, debridement, and antibiotics. After years of clinical observations and poor results in treatment of peri-implantitis, a new proposal of this condition is presented, shifting our way of thinking regarding bone and implant interactions. In the second part of the paper presenting a new definition of peri-implantitis, we focused on a biological explanation of the bone behavior at the bone–implant interface. The main conclusion is that PI is not an “infectious disease”, but rather the result of natural changes of the bone’s morphology in response to implant such as a decrease in convexity of the outer surface of the bone and subsequently a decrease in concavity of the inner bone.

Thermal Modeling of Ultrasound Diathermy in Tissues with a Circular Inclusion near a Curved Interface

The influences of implants on the temperature field in tissues during ultrasound diathermy is controversial. In addition, most previous studies have focused on plate implants, and the effects of irregular implants and bones are seldom discussed. In this study, a hybrid computational framework per se is proposed to investigate the effects of double circular inclusions on the temperature distribution during ultrasound diathermy. The tissue–inclusion–bone structure is simplified as a two-dimensional bilayer composite model consisting of soft tissue and bone with a circular inclusion imbedded in the soft tissue. The interface between the bone layer and the soft-tissue layer is assumed as a convex surface for the incident ultrasonic waves. Multiply scattered waves originate between the two acoustic scatterers, i.e., the circular inclusion and the convex bone. The proposed computational framework consists of two kernels tackling ultrasound propagation and heat conduction problems, respectively. Making use of theoretical solutions of pressure fields, the transformed heat sources are efficiently obtained in the first kernel without sacrificing much computational burden. Temperature distributions in the composite media under ultrasound diathermy are evaluated via finite element numerical simulations in the second kernel. Numerical results indicate that the temperature distributions in the composite system obviously change when the bone layer changes from flat to convex. In addition, the inclusion size, location, material, and ultrasound operation frequency will also affect the temperature distribution and peak temperature during ultrasound diathermy. Pertinent findings could serve as a guide for clinical innovations in therapeutic ultrasounds.

Study of the Efficacy of Artificial Intelligence Algorithm-Based Analysis of the Functional and Anatomical Improvement in Polynucleotide Treatment in Knee Osteoarthritis Patients: A Prospective Case Series.

Knee osteoarthritis (OA) is one of the most common degenerative diseases in old age. Recent studies have suggested new treatment approaches dealing with subchondral remodeling, which is a typical feature of OA progression. However, diagnostic tools or therapeutic approaches related to such a process are still being researched. The automated artificial intelligence (AI) algorithm-based texture analysis is a new method used for OA-progression detection. We designed a prospective case series study to examine the efficacy of the AI algorithm-based texture analysis in detecting the restoration of the subchondral remodeling process, which is expected to follow therapeutic intervention. In this study, we used polynucleotide (PN) filler injections as the therapeutic modality and the treatment outcome was verified by symptom improvement, as well as by the induction of subchondral microstructural changes. We used AI algorithm-based texture analysis to observe these changes in the subchondral bone with the bone structure value (BSV). A total of 51 participants diagnosed with knee OA were enrolled in this study. Intra-articular PN filler (HP cell Vitaran J) injections were administered once a week and five times in total. Knee X-rays and texture analyses with BSVs were performed during the screening visit and the last visit three months after screening. The Visual Analogue Scale (VAS) and Korean-Western Ontario MacMaster (K-WOMAC) measurements were used at the screening visit, the fifth intra-articular injection visit, and the last visit. The VAS and K-WOMAC scores decreased after PN treatment and lasted for three months after the final injection. The BSV changed in the middle and deep layers of tibial bone after PN injection. This result could imply that there were microstructural changes in the subchondral bone after PN treatment, and that this change could be detected using the AI algorithm-based texture analysis. In conclusion, the AI- algorithm-based texture analysis could be a promising tool for detecting and assessing the therapeutic outcome in knee OA.

Peri-Implantitis: A New Definition Proposal Based on Unnatural Spatial Arrangement and Late Mechanical Coupling between Two Cortical Bone Layers during Osseointegration Phase: Part I

Scientists have been speculating for three decades about the reasons for the occurrence of peri-implantitis around dental implants. Many theories have been proposed since the beginning of 1990. Since then, the dental profession has been exposed to a vast number of peri-implantitis cases, whereas the “disease” had been unknown before this time. However, the situation has not improved because we focus more on how to treat the problem instead of trying to understand it completely. The aim of this paper is to present a purely bone-based explanation for the beginning of the “bone loss” process around already “osseointegrated” implants. Conclusion: There are a number of possible chain reactions of physiological bone response to dental implants which may explain the occurrence of peri-implantitis. Bacteria and “immunological reactions” may not be the main causes of this disease. In the first part, the authors present the principles of bone biology and physiology based on the theories of Donath, Jansen and Frost and transfer them to the field of implantology. They describe the stages of “osseointegration”, explaining the subsequent changes in the bone at the implant–bone interface.

3D bioassembly of cell-instructive chondrogenic and osteogenic hydrogel microspheres containing allogeneic stem cells for hybrid biofabrication of osteochondral constructs

Recently developed modular bioassembly techniques hold tremendous potential in tissue engineering and regenerative medicine, due to their ability to recreate the complex microarchitecture of native tissue. Here, we developed a novel approach to fabricate hybrid tissue-engineered constructs adopting high-throughput microfluidic and 3D bioassembly strategies. Osteochondral tissue fabrication was adopted as an example in this study, because of the challenges in fabricating load bearing osteochondral tissue constructs with phenotypically distinct zonal architecture. By developing cell-instructive chondrogenic and osteogenic bioink microsphere modules in high-throughput, together with precise manipulation of the 3D bioassembly process, we successfully fabricated hybrid engineered osteochondral tissue in vitro with integrated but distinct cartilage and bone layers. Furthermore, by encapsulating allogeneic umbilical cord blood-derived mesenchymal stromal cells, and demonstrating chondrogenic and osteogenic differentiation, the hybrid biofabrication of hydrogel microspheres in this 3D bioassembly model offers potential for an off-the-shelf, single-surgery strategy for osteochondral tissue repair.

Effect of disease duration on the distribution of otosclerotic foci within the stapes based on scanning electron microscopy analysis

Introduction: Otosclerosis is characterized by the presence of abnormal resorption and recalcification of the endochondral layer of the temporal bone, which is not observed in healthy subjects. The result of the alternating occurrence of both processes is the appearance of disorganized and, over time, dense, sclerotic bone tissue underlying the clinical manifestation of the otosclerotic process. Aim: The aim of the work is the chemical analysis of otosclerotic foci of the stapes superstructure with the use of a scanning electron microscope. Material and methods: Patients operated for the first time due to otosclerosis were analyzed. The removed stirrup suprastructures were examined in a Scanning Electron Microscope (SEM) using microanalytical techniques (WDXS – Wavelength-dispersive X-ray spectroscopy TEXS – Transition Element X-ray Spectrometer) and diffraction techniques (2D EBSD – Electron Backscatter Diffraction). Results: In patients with a short medical history, a statistically significant difference in calcium (Ca) concentration was found between the anterior and posterior cruses of stapes. Along with the duration of the disease, a statistically significant difference in calcium (Ca) concentration was observed between the stapes head and its cruses. In the course of the disease, degradation of the microstructure of the stapes bone tissue was observed in a scanning electron microscope. Conclusions: (A) As the otosclerotic process progresses, significant changes in the chemical composition between the individual parts of the stapes superstructure are observed; (B) The observed biochemical changes are accompanied by changes in the microstructure of bone tissue observed in SEM.

Life history and ossification patterns in Miguashaia bureaui reveal the early evolution of osteogenesis in coelacanths.

The study of development is critical for revealing the evolution of major vertebrate lineages. Coelacanths have one of the longest evolutionary histories among osteichthyans, but despite access to extant representatives, the onset of their weakly ossified endoskeleton is still poorly understood. Here we present the first palaeohistological and skeletochronological study of Miguashaia bureaui from the Upper Devonian of Canada, pivotal for exploring the palaeobiology and early evolution of osteogenesis in coelacanths. Cross sections of the caudal fin bones show that the cortex is made of layers of primary bone separated by lines of arrested growth, indicative of a cyclical growth. The medullary cavity displays remnants of calcified cartilage associated with bony trabeculae, characteristic of endochondral ossification. A skeletochronological analysis indicates that rapid growth during a short juvenile period was followed by slower growth in adulthood. Our new analysis highlights the life history and palaeoecology of Miguashaia bureaui and reveals that, despite differences in size and habitat, the poor endoskeletal ossification known in the extant Latimeria chalumnae can be traced back at least 375 million years ago.

Palaeobiological inferences of the aetosaur Aetosauroides scagliai (Archosauria: Pseudosuchia) based on microstructural analyses of its appendicular bones

ABSTRACT Aetosaurs were a group of armoured pseudosuchians, recorded in most of the Upper Triassic continental deposits worldwide. Several osteohistological contributions of aetosaurs focused on their osteoderms, but rarely on appendicular bones. Here, we analyse the microstructure of the humerus, femur and tibia of Aetosauroides scagliai (specimens PVL 2073 [holotype] and PVL 2052). These exhibit cortical bone formed by highly vascularised fibrolamellar bone present in the inner portion of the cortex, mixed with scarce parallel-fibred bone. Also, they show parallel-fibred bone in the outermost portion of the cortex. A general growth pattern that includes a first rapid stage followed by a slow stage is reported. Nevertheless, the growth rate and the presence of parallel-fibred bone embedded in fibrolamellar bone layers recognise more variation within Aetosauria. The value of appendicular bones and osteoderms as age estimators is variable, the first being useful in early stages, and in late stages the osteoderms are better (based on the particular growth of osteoderms). Through morphological (neurocentral sutures) and histological (EFS absent) information, the holotype (PVL 2073) was recovered between juvenile and subadult stages. Using a statistical model that combines microanatomical and morphological data, a terrestrial lifestyle is inferred for Aetosauroides, which concur with previous analyses.

Bilayered laponite/alginate-poly(acrylamide) composite hydrogel for osteochondral injuries enhances macrophage polarization: An in vivo study

Addressing osteochondral defects, the objective of current study was to synthesize bilayered hydrogel, where the cartilage layer was formed by alginate (Alg)-polyacrylamide (PAAm) with and without the addition of TGF-β3 and bone layer by laponite XLS/Alg-PAAm and characterize by in vitro and in vivo experiments. Exceeding the mechanical strength of Alg-PAAm (32.95 ± 1.23 kPa) and XLS based (317.5 ± 21.72 kPa) hydrogels, XLS/Alg-PAAm hydrogel (469.7 ± 6.1 kPa) activated macrophages towards M2 phenotype and stimulated the expression of anti-inflammatory factors. The addition of TGF-β3 accelerated transition of macrophage polarization, especially between day 4 and 7. The expression levels of M1-related genes such as CD80, iNOS and TNF-α decreased gradually after day 4, reaching lowest values at day 13, whereas the expression levels of M2-related genes, CD206, Arg1 and STAT6 significantly increased promoting M2 macrophage polarization, which might be associated with accelerated bone repair. Moreover, bilayer structure exhibited a better cell viability as well as repairment thorough the XLS contents. In vivo histological examinations verified the significant surface regularity and hyaline like tissue formation employment, along with synchronized degradation profile of the hydrogel with tissue healing at the end of 12 weeks. A mechanically durable, biocompatible and immunocompatible hydrogel was formulated to be utilized in bone-cartilage engineering applications.

Dynamic process enhancement on chitosan/gelatin/nano-hydroxyapatite-bone derived multilayer scaffold for osteochondral tissue repair

Accurate repair of osteochondral defects is a great challenge due to the complex structure of osteochondral defects. The current study aims to prepare a biomimetic osteochondral gradient scaffold based on chitosan, gelatin and nano-hydroxyapatite and bone-derived materials for repair cartilage defects. Hereon, the chitosan/gelatin/nano-hydroxyapatite multilayer scaffold with complex hierarchical structure using iterative hierarchical method is prepared to simulate the structure of natural cartilage. And porcine femur in distal metaphysis was treated by chemical decellularization, deproteinization, decalcification, and degreasing to obtain the bone-derived scaffold simulating subchondral bone layer. We also used a spinner bioreactor for the in vitro modeling of the microenvironment which can promote adipose mesenchymal stem cell (ADSCs) recruitment into the chitosan/gelatin/nano-hydroxyapatite-bone derived multilayer scaffold under physiological flow conditions. Biological experiments have shown that osteochondral layered materials can induce ADSCs to differentiate into chondrocytes and osteoblasts and exhibit chondrogenic and osteogenic phenotypes similar to natural tissues, respectively. Furthermore, the expression both of the chondrogenic gene (Col II, ACAN, and Sox9) and osteogenic gene (Runx2, OCN and Col I) of ADSCs differentiated by mechanical stimulation were increased. These results indicate that osteochondral materials and dynamic environment are the key factors to improve cell regulation or signal molecule transfer function, and provide a feasible plan for osteochondral regeneration for future medical services.

Analysis of facial pressure generated by everyday masks using the finite element method

In the present work, a model based on the finite element method is formulated, with the purpose of measuring the facial pressure generated by everyday masks. The analysis includes the computational determination of the contact pressure generated by the mask on two head shapes that contemplate the anthropometric dimensions of the Colombian population between 20 and 59 years old, one represents the male sex and the other the female sex. The head model is divided into five parts (two cheeks, the forehead, the chin, and the back of the head), some of them contemplate layers of skin, muscle, fat tissue and bone, according to the anatomy of the human head. The mask is made up of three layers of different materials, a metal clip and two elastic bands that allow the mask to be adjusted to the face. The simulation process consists of placing the mask fully centered on the face and stretching the elastic bands until they are located at the back of the ears, thus generating facial contact between the mask and the head. The results obtained in the simulation indicate that the maximum pressure values are found in five specific points of the head.

Mimicking the Composition and Structure of the Osteochondral Tissue to Fabricate a Heterogeneous Three-Layer Scaffold for the Repair of Osteochondral Defects.

Heterogeneous three-layer scaffolds were fabricated by mimicking the biochemical composition and structure of the hyaline cartilage, calcified cartilage, and subchondral bone of the osteochondral tissue for the repair of osteochondral defects. The hyaline cartilage layer was composed of collagen I (50.0 wt %) and sodium hyaluronate (50.0 wt %). The calcified cartilage layer and subchondral bone layer were composed of collagen I, sodium hyaluronate, and nanohydroxyapatite with different proportions. N-Hydroxysuccinimide/N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride was used to mediate the crosslinking reaction of the amine groups of collagen with carboxyl groups of sodium hyaluronate. The hyaline cartilage layer and calcified cartilage layer were designed as dense structures, while the subchondral bone layer was designed as a relatively loose structure by adjusting the crosslinking degree. The scaffolds displayed a uniform and interconnected porous structure and possessed a high porosity over 85%, which were conducive to cellular adhesion and proliferation. The scaffolds could remain at 50-75% after 30 days of degradation owing to crosslinking, providing enough time for the regeneration of the osteochondral tissue. Especially, the hyaline cartilage layer and calcified cartilage layer preferred to induce the proliferation of chondrocytes, while the subchondral bone layer was more conducive to the proliferation of osteoblasts. In conclusion, the heterogeneous multilayer scaffolds could serve as implant materials for osteochondral reconstruction.

Bone‐on‐a‐Chip: A Microscale 3D Biomimetic Model to Study Bone Regeneration

Organ‐on‐chip models, developed using microengineering and microfluidic technologies, aim to recreate physiological‐like microenvironments of organs or tissues as a tool to study (patho)physiological processes in vitro. On‐chip models of bone are relevant for the study of bone physiology, diseases and regenerative processes. While a few bone‐on‐a‐chip models exist, recapitulating the cellular components of bone, these models do not incorporate the chemical and structural characteristics of bone tissue. Herein, the development of a bone‐on‐a‐chip platform is reported that comprises a 3D structural model of bone. To build the platform, first, a 3D model of bone is produced in a polymer using two‐photon polymerization (2PP) from a 3D nano‐computed tomography scan of trabecular bone. This 3D model is then coated with a layer of bone mineral‐like calcium phosphate. Finally, the 3D bone model is integrated inside a microfluidic device suitable for cell culture. Human mesenchymal stromal cells, cultured inside the platform for up to 21 days, show high viability and extensive production of extracellular matrix, rich in collagen. This biomimetic bone‐on‐a‐chip platform can contribute to a better understanding of the processes related to bone formation and remodeling, which in turn can be used for the development of bone regeneration strategies.

Development and in vitro assessment of a bi-layered chitosan-nano-hydroxyapatite osteochondral scaffold

An innovative approach was developed to engineer a multi-layered chitosan scaffold for osteochondral defect repair. A combination of freeze drying and porogen-leaching out methods produced a porous, bioresorbable scaffold with a distinct gradient of pore size (mean = 160–275 μm). Incorporation of 70 wt% nano-hydroxyapatite (nHA) provided additional strength to the bone-like layer. The scaffold showed instantaneous mechanical recovery under compressive loading and did not delaminate under tensile loading. The scaffold supported the attachment and proliferation of human mesenchymal stem cells (MSCs), with typical adherent cell morphology found on the bone layer compared to a rounded cell morphology on the chondrogenic layer. Osteogenic and chondrogenic differentiation of MSCs preferentially occurred in selected layers of the scaffold in vitro, driven by the distinct pore gradient and material composition. This scaffold is a suitable candidate for minimally invasive arthroscopic delivery in the clinic with potential to regenerate damaged cartilage and bone.

Ossifying fibroma a case report with review of literature

Ossifying fibroma also known as cemento ossifying fibroma is a slow-growing benign fibroosseous lesions of the oral and maxillofacial regions. They present clinically as asymptomatic swelling of the cortical layer of jaw bones, producing a marked extraoral facial asymmetry. Fibrous dysplasia a developmental anomaly, wherein bone gets replaced by fibrous tissue, whereas ossifying fibroma, cemento-osseous dysplasia or familial gigantiform cementoma are either reactive or dysplastic change, derived from periodontal ligament, extraligamentary bone or remnants of cementum may create confusion to a clinician. Because of the presence of both bone and cementum-like products in ossifying fibromas, these lesions are designated as ossifying fibroma, cemento-ossifying fibroma, and cementifying fibroma. Fortunately ossifying fibromas are treated with surgical curettage with acceptable results. This paper is a humble attempt to present a case of Ossifying fibroma of maxilla which is otherwise common in mandible, and its esthetic outcome after the surgical treatment through Weber Fergusson's approach and a review of literature.

EXPERIMENTAL STUDY OF BONE DENSITY IN PATIENTS WITH CONGENITAL PSEUDOARTHROSIS OF THE TIBIA BEFORE AND AFTER SURGERY.

The aim: Determine the changes in bone density that occur in the cortical layer of the tibia in patients with CPT after surgical treatment due to radiography data. Materials and methods: The study was performed on X-rays of the tibia of three patients with CPT, aged 5 to 7 years. X-rays were taken before surgery and 1 year after surgery. The optical density of the cortical layer of both tibia bones was determined, for which they were conditionally divided into 7 zones. Results: In all patients with CPT before treatment, there is significant decrease in the optical density of cortical bone tissue of the damaged tibia compared with contralateral. One year after surgery, there was an increase in the optical density of the cortical layer of both tibia of the studied patients. The increase in the density of the nonoperated tibia can be attributed to the active growth of patients. On the operated limb, the increase in the density of the cortical layer became statistically significant in all studied areas, which can be attributed not only to the growth of patients, but also to the possibility of active loading of the operated limb. Conclusions: In all patients with CPT before treatment, a statistically significant decrease in the density of cortical bone tissue of the damaged tibia was observed. As a result of the treatment there is an approximation of the bone density of the operated limb to the indicators of intact contralateral bone.