In Vitro Evaluation of Nanoscale Hydroxyapatite-Based Bone Reconstructive Materials with Antimicrobial Properties.

In the field of oral implantology the loss of bone tissue prevents adequate patient care, and calls for the use of synthetic biomaterials with properties that resemble natural bone. Special attention is paid to the risk of infection after the implantation of these materials. Studies have suggested that some nanocontructs containing metal ions have antimicrobial properties. The aim of this study was to examine the antimicrobial and hemolytic activity of cobalt-substituted hydroxyapatite nanoparticles, compared to hydroxyapatite and hydroxyapatite/poly-lactide-co-glycolide. The antibacterial effects of these powders were tested against two pathogenic bacterial strains: Escherichia coi (ATCC 25922) and Staphylococcus aureus (ATCC 25923), using the disc diffusion method and the quantitative antimicrobial test in a liquid medium. The quantitative antimicrobial test showed that all of the tested biomaterials have some antibacterial properties. The effects of both tests were more prominent in case of S. aureus than in E coli. A higher percentage of cobalt in the crystal structure of cobalt-substituted hydroxyapatite nanoparticles led to an increased antimicrobial activity. All of the presented biomaterial samples were found to be non-hemolytic. Having in mind that the tested of cobalt-substituted hydroxyapatite (Ca/Co-HAp) material in given concentrations shows good hemocompatibility and antimicrobial effects, along with its previously studied biological properties, the conclusion can be reached that it is a potential candidate that could substitute calcium hydroxyapatite as the material of choice for use in bone tissue engineering and clinical practices in orthopedic, oral and maxillofacial surgery.

Sexual Dimorphism in the Dimensions of Teeth in Serbian Population.

The study of teeth is of great interest to anthropologists, biologists, orthodontists and forensic scientists. The existence of sexual dimorphism in permanent teeth is a known phenomenon. Aim of this study was to analyze the presence of sexual dimorphism in the mesiodistal and vestibulolingual diameter of permanent teeth in the sample of Serbian population. Measurements were taken on plaster casts of 201 individuals of both sexes, ages between 18-25 years, using a digital caliper with 0.01 mm precision. The mesiodistal and vestibulolingual diameter of each permanent tooth was determined. A Student's t-test and a Mann-Whitney U test were used to statistically analyze the obtained results. There were no statistically significant differences in the teeth crown diameter between the right and left side of the same dental arch. Majority of the teeth examined were larger in male than in female patients. Statistically significant difference in the mesiodistal diameter of male and female maxillary and mandibular canines was found. The results of this study indicate that there are significant differences in teeth size between sexes in Serbian population. Males have larger diameters in teeth crowns than females. Canines show the greatest dimorphism.

Aspects of orthodontic-prosthetic rehabilitation of dentofacial anomalies.

Skeletal class III malocclusion is one of the most difficult dentofacial anomalies, characterized by deviation in the development of the mandible and maxilla in the sagittal plane, where the mandible is dominant in relation to the maxilla. In patients with class III malocclusion, anomalies in the dentoalveolar level and esthetic discrepancies are also frequent. The etiology of class III malocclusion is multifactorial due to the interaction of hereditary and environmental factors. Rehabilitation and treatment of malocclusion is one of the major goals of modern dentistry. This article presents the orthodontic-prosthetic therapy and rehabilitation of a 45-year-old patient with an abnormal occlusal vertical dimension and a skeletal class III malocclusion. The patient came to the clinic complaining about degraded esthetics and disordered functions of the orofacial region (functions of eating, swallowing, speech) and also pain in the temporomandibular joint. After the diagnosis was made, the patient was first referred to orthodontic treatment with fixed orthodontic appliances (self-ligating brackets system Rot 0.22). Upon completion of the orthodontic treatment, the patient was sent for further prosthetic treatment. Fixed prosthetic restorations were made in the upper and lower jaw, thus achieving a satisfactory result in terms of esthetics and function of the stomatognathic system.

Nanoparticles of cobalt-substituted hydroxyapatite in regeneration of mandibular osteoporotic bones.

Indications exist that paramagnetic calcium phosphates may be able to promote regeneration of bone faster than their regular, diamagnetic counterparts. In this study, analyzed was the influence of paramagnetic cobalt-substituted hydroxyapatite nanoparticles on osteoporotic alveolar bone regeneration in rats. Simultaneously, biocompatibility of the material was tested in vitro, on osteoblastic MC3T3-E1 and epithelial Caco-2 cells in culture. The material was shown to be biocompatible and nontoxic when added to epithelial monolayers in vitro, while it caused a substantial decrease in the cell viability as well as deformation of the cytoskeleton and cell morphology when incubated with the osteoblastic cells. In the course of 6 months after the implantation of the material containing different amounts of cobalt, ranging from 5 to 12 wt%, in the osteoporotic alveolar bone of the lower jaw, the following parameters were investigated: histopathological parameters, alkaline phosphatase and alveolar bone density. The best result in terms of osteoporotic bone tissue regeneration was observed for hydroxyapatite nanoparticles with the largest content of cobalt ions. The histological analysis showed a high level of reparatory ability of the nanoparticulate material implanted in the bone defect, paralleled by a corresponding increase in the alveolar bone density. The combined effect of growth factors from autologous plasma admixed to cobalt-substituted hydroxyapatite was furthermore shown to have a crucial effect on the augmented osteoporotic bone regeneration upon the implantation of the biomaterial investigated in this study.

Influence of saliva medium on freeing heavy metal ion from fixed dentures.

In dental-prosthetic practice, various kinds of fixed dentures, crowns and bridges, have very often been used in order to replace natural teeth and to respond to all health and esthetic needs. This study investigated the effect of saliva medium on migration of ions of heavy metals from fixed dentures that were fixed with various cements. Also, the influence of saliva medium on natural human teeth was observed. Potentiometric stripping analysis was used in order to determine the content of toxic heavy metals in the examined samples. The study confirmed that synthetic saliva had no significant influence on heavy metal ion migration from the natural teeth, whereas slight migration of some observed toxic heavy metal ions from the fixed dentures was present. This, however, indicates that these contents, although very low, must be taken seriously, because the above mentioned metals have cumulative effect which after some period of time may lead to functional disorders of some organs, and even to some very serious diseases.

Substitution of osteoporotic alveolar bone by biphasic calcium phosphate/poly-DL-lactide-co-glycolide biomaterials.

Lost bone tissue due to osteoporosis makes dentistry very difficult. The aim of thisstudy is to reconstruct the bone tissue with composite biomaterials and to estimate the optical density and alveolar ridge height of the mandible. Research is conducted on 30 postmenopausal women aged from 46 to 62 years, with diagnosed osteoporosis and defects in alveolar bones caused by extraction of paradontopathic teeth, enucleation of cysts and periapical changes, extraction of impacted teeth,or by trauma.Biphasic calcium phosphate/poly-DL-lactide-co-glycolide (BCP/PLGA) composite is implanted into the defects of alveolar bones. Six weeks after implantation of BCP/PLGA, the alveolar bone density in the region of premolars on the experimental side of the jaw is found to be lower than that on the untreated, control, side of the jaw. On thecontrary, 24 weeks after implantation, it is significantly higher compared with the density of the control side. A significant increase in optical density of alveolar bones in the region of premolars on the experimental side compared with the control one is noticed. These results indicate a high level of osteoregeneration and osteoblast activity. Synthetic BCP/PLGA composite belongs to the group of biomaterials, which facilitate formation of new bones and rehabilitation of alveolar bones weakened by osteoporosis. Because of its osteoconductive characteristics, BCP/PLGA composite is supposed to be the material of choice for replacement of bone tissue in the future.

Chitosan-PLGA polymer blends as coatings for hydroxyapatite nanoparticles and their effect on antimicrobial properties, osteoconductivity and regeneration of osseous tissues.

Composite biomaterials comprising nanostructured hydroxyapatite (HAp) have an enormous potential for natural bone tissue reparation, filling and augmentation. Chitosan (Ch) as a naturally derived polymer has many physicochemical and biological properties that make it an attractive material for use in bone tissue engineering. On the other hand, poly-D,L-lactide-co-glycolide (PLGA) is a synthetic polymer with a long history of use in sustained drug delivery and tissue engineering. However, while chitosan can disrupt the cell membrane integrity and may induce blood thrombosis, PLGA releases acidic byproducts that may cause tissue inflammation and interfere with the healing process. One of the strategies to improve the biocompatibility of Ch and PLGA is to combine them with compounds that exhibit complementary properties. In this study we present the synthesis and characterization, as well as in vitro and in vivo analyses of a nanoparticulate form of HAp coated with two different polymeric systems: (a) Ch and (b) a Ch-PLGA polymer blend. Solvent/non-solvent precipitation and freeze-drying were used for synthesis and processing, respectively, whereas thermogravimetry coupled with mass spectrometry was used for phase identification purposes in the coating process. HAp/Ch composite particles exhibited the highest antimicrobial activity against all four microbial strains tested in this work, but after the reconstruction of the bone defect they also caused inflammatory reactions in the newly formed tissue where the defect had lain. Coating HAp with a polymeric blend composed of Ch and PLGA led to a decrease in the reactivity and antimicrobial activity of the composite particles, but also to an increase in the quality of the newly formed bone tissue in the reconstructed defect area.

Multifunctional hydroxyapatite and poly(D,L-lactide-co-glycolide) nanoparticles for the local delivery of cholecalciferol.

Cholecalciferol, vitamin D3, plays an important role in bonemetabolism by regulating extracellular levels of calcium. Presented here is a study on the effects of the local delivery of cholecalciferol (D3) using nanoparticulate carriers composed of hydroxyapatite (HAp) and poly(D,L-lactide-co-glycolide) (PLGA). Multifunctional nanoparticulate HAp-based powders were prepared for the purpose of: (a) either fast or sustained, local delivery of cholecalciferol, and (b) the secondary, osteoconductive and defect-filling effect of the carrier itself. Two types of HAp-based powders with particles of narrowly dispersed sizes in the nano range were prepared and tested in this study: HAp nanoparticles as direct cholecalciferol delivery agents and HAp nanoparticles coated with cholecalciferol-loaded poly(D,L)-lactide-co-glycolide (HAp/D3/PLGA). Satisfying biocompatibility of particulate systems, when incubated in contact with MC3T3-E1 osteoblastic cells in vitro, was observed for HAp/D3/PLGA and pure HAp. In contrast, an extensively fast release of cholecalciferol from the system comprising HAp nanoparticles coated with cholecalciferol (HAp/D3) triggered necrosis of the osteoblastic cells in vitro. Artificial defects induced in the osteoporotic bone of the rat mandible were successfully reconstructed following implantation of cholecalciferol-coated HAp nanoparticles as well as those comprising HAp nanoparticles coated with cholecalciferol-loaded PLGA (HAp/D3/PLGA). The greatest levels of enhanced angiogenesis, vascularization, osteogenesis and bone structure differentiation were achieved upon the implementation of HAp/D3/PLGA systems.

Size effect of calcium phosphate coated with poly-DL-lactide- co-glycolide on healing processes in bone reconstruction.

In this article, synthesis and application of calcium phosphate/poly-DL-lactide-co-glycolide (CP/PLGA) composite biomaterial in particulate form, in which each CP granule/particle is coated with PLGA, are described. Two types of the particulate material having different particle sizes were synthesized: one with an average particle diameter between 150 and 250 mum (micron-sized particles, MPs) and the other with an average particle diameter smaller than 50 nm (nanoparticles, NPs). A comparative in vivo analysis was done by reconstructing defects in osteoporotic alveolar bones using both composites. The material, CP granules/particles covered with polymer, was characterized using X-ray structural analysis, scanning electron microscopy, and atomic force microscopy. Changes in reparatory functions of tissues affected by osteoporosis were examined in mice in vivo, using these two kinds of composite materials, with and without autologous plasma. Having defined the target segment, histomorphometric parameters-bone area fraction, area, and mean density-were determined. The best results in the regeneration and recuperation of alveolar bone damaged by osteoporosis were achieved with the implantation of a mixture of nanoparticulate CP/PLGA composite and autologous plasma. After the implantation of microparticulate CP/PLGA, in the form of granules, mixed with autologous plasma, into an artificial defect in alveolar bone, new bone formation was also observed, although its formation rate was slower.

[Comparative analysis of linear morphometric parameters of the humane mandibula obtained by direct and indirect measurement].

BACKGROUND/AIM: Reconstruction of lost, damaged or distorted mandibular bone presents a challenge from the functional side, as well as from the esthetic point of view. The aim of this study was to determinate potential differences between values of the basic linear moprhometric parameters (LMPs) obtained by direct and indirect manual measurement of the same humane mandibles, with accuracy testing of indirect measurement, which are routinely used in every-day clinical practice. The results are essential for defining of parametric model of the "standard mandible" and virtual modeling of the humane mandible in future researches as well as in clinical medicine. METHODS: A total number of 12 dry bony mandibles of human adults were studied. According to the standard anatomical landmarks, 10 standard LPMs were measured on each mandible by different manual methods: directly by a sliding caliper with nonius, and indirectly using standard software on two-dimensional (2D) reconstructions of mandibular multislice computed tomography (MSCT) scans. The values obtained by the different measuring methods were matched for the same LMPs. RESULTS: Statistically significant differences between compared LMPs values obtained by different measuring methods, appeared in the gnathio-interdental distance (Gn-IdD), as well as in the gnathio-condylar distance (Gn-CoD), bilaterally. In both parameters, significantly higher mean values (with percent of difference) were obtained by direct versus indirect measurement: Gn-IdD (21.57%; 29.2 mm vs 22.9 mm; p = 0.004); Gn-CoD left side (14.1%; 122.7 mm vs 105.4 cm; p = 0.001); Gn-CoD right side (11.87%; 124.7 mm vs 109.9 mm; p = 0.009). CONCLUSION: According to the observed inaccuracy of indirect measurement, we recommended the use of a correction factor for calculation of both Gn-IdD and Gn-CoD real vales, in defining of parametric model of the "standard mandible" based on indirect morphometry on 2D reconstructions of mandibular MSCT scans. Additional studies with larger number of specimens and quantification of anatomical variations regarding to sex, age, dentition status and ethnic origin, additionally should increase measurement accuracy and consequently reliability of future parametric model of the human mandible.

[The neutral zone and vertical dimension of occlusion].

INTRODUCTION: More recent research points out to the existence of a new concept of the technique for locating the neutral zone. The objective of the study was to determine the effect of changing vertical dimension of occlusion, as well as that of the alveolar ridge type, on the neutral zone dimensions. MATERIAL AND METHODS: The neutral zone was investigated in two groups of patients, with prominent (the control group) and flat alveolar ridges and it was determined for each patient at 3 heights (the correct, the increased and the decreased vertical dimension of occlusion). It was studied both vertically and horizontally. The width of the neutral zone was measured in different regions. RESULTS: The width of the neutral zone was minimal at the level of the occlusal plane, and it increased gradually as the occlusal plane went down and up, towards the anterior region. CONCLUSION: No statistically significant difference was found in the width of the neutral zone, between the group of patients with prominent alveolar ridges (the control group), and that with the flat ones. There was, also, no difference at all, at any level of the vertical dimension of occlusion, that could possibly bear statistical significance.

[Mineral substances in the bone tissue and blood of patients with osteoporosis].

INTRODUCTION: Osteoporosis is a very common disorder of skeleton, which can be caused by various metabolic disturbances, malnutrition, immobilization, endocrine disorders, bone marrow diseases, connective tissue disorders, and, in some cases, by inappropriate therapy. The aim of this investigation was to evaluate the relationships between the mineral content in the alveolar bone and serum osteoporosis in chosen patients. MATERIAL AND METHODS: The study included an experimental and a control group of patients who were submitted to internal and prosthodontic therapy. The plan of therapy was to extract anticipated parodonthopathic teeth, taking samples of the alveolar bone and its analysis by spectrometry. At the same time the biochemical analyses of the blood were performed. RESULTS: Before the therapy, due to negative remodeling, values of mineral content in decalcified bone tissue and serum were significantly lower than in the control group. After the therapy, the quality of the bone tissue was improved, with increased contents of mineral substances. DISCUSSION AND CONCLUSION: Disorders of mineral metabolism are very important for osteoporosis. This disorder may involve entire skeleton, especially stomatoghnatic complex. Therefore osteoporosis is one of very important illnesses in dentistry, especially in prosthodontics, because of the supporting nature of bone tissue for all types of dental prostheses.

[Preparation of irreversible hydrocolloides to improve retention of complete dentures].

INTRODUCTION: Precise reproduction of anatomical-morphological details of dentures support on working models presupposes adequate application of modern impression materials and casting procedure, as well as minimal dimensional change of these materials. THE AIM OF THE STUDY: experimental and clinical research is connected to irreversible hydrocolloides and the objective was to examine the most suitable consistency of the alginate as the impression mass for the purpose of improving retention of complete dentures. MATERIAL AND METHODS: This research included 35 completely toothless patients, most of who had already had complete dentures, 40-80 years of age and of both sexes. Static adhesion was measured with acrylate plates made of adequate corresponding and various models depending on consistency of the irreversible hydrocolloides. Each model was cut into three parts, the cuts obtained were mutually compared, and computerized graphic charts of each section were made. RESULTS: The results of the research show that there is a greater retention force in the acrylate plates obtained on models casted on an anatomical impression base taken with irreversible hydrocolloides of solid consistency. Analysis of the results shows such quality of impressed tissues that they are practically slightly displaced by the impressions regardless of the consistency of the material impressed. CONCLUSION: In conclusion it is pointed out that the preparation of irreversible hydrocolloides must be carried out by strictly obeying the powder-water weight ratios. The sections of the models obtained by irreversible hydrocolloides of various consistencies, that is by applying different pressures, point to minimal displacement of tissues and great differences in the retention force in favour of the compressive impression.

[Neurophysiological conception of pain in craniomandibular disfunction].

INTRODUCTION: Ethiopathogenesis of dysfunction and pain in temporomandibular joints has been the subject of passionate discussions between supporters of purely mechanical conception and the ones who are supporters of psyhosomatic conception. THE AIM OF THE STUDY: Relying on neurophysiological data, the authors are trying to reveal the main role of reticular mesencephalical formation in mechanisms which provoke craniomandibular dysfunctions and confront the influence of emotional factors from neocortex and painful stimuli from oral structures. DISCUSSION: From dynamical point of view, not only the morphological aspects of teeth and arcades, but also sensitive-sensorial mechanisms connected to masticatory muscles, periodontal structures and oral structures, should be considered. The ideal bite and perfect morphology of tooth arcades are not enough for reconstitution of correct occlusion, if there are no neuromuscular system, temporomandibular joint, and especially central nervous system. CONCLUSION: The presence of pain is just one of the craniomandibular dysfunction symptoms, but if it is added to the other clinical signs and emotional or affect--provoking factor, it will provoke dysfunctional syndrome.