Ilze Šalma

Volumetric analysis of implanted biphasic calcium phosphate/collagen composite by three-dimensional cone beam computed tomography head model superimposition.

Facial onlay augmentation is often performed as an ancillary procedure simultaneously with orthognathic surgery to improve facial appearance, with hydroxyapatite (HAp) and HAp-based composites often used as the materials of choice. The ability to apply HAp in a granular rather than solid shape form may be responsible for its comparatively reduced rate of complications. However, a known complication of HAp and HAp composites is reduction of implant volume over time associated with resorption of the material. Evaluation of the volumetric changes of implanted biphasic calcium phosphate (HAp/β-TCP)/collagen composite in the malar areas from baseline to 4 months, 9-12 months, and 18-24 months after surgery using cone beam computed tomography (CBCT) surface superimposition and volumetric subtraction was done. The average decrease of volume of implanted HAp/β-TCP 4 months after surgery was 18.6%. Further volumetric decreases were negligible and a mean total volume loss of 21.65% was found at 18-24 months postoperatively.

Porous Hydroxyapatite Bioceramic Scaffolds for Drug Delivery and Bone Regeneration

The conventional methods of supplying a patient with pharmacologic active substances suffer from being very poorly selective, so that damage can occurs to the healthy tissues and organs, different from the intended target. In addition, high drug doses can be required to achieve the desired effect. An alternative approach is based on the use of implantable delivery tools, able to release the active substance in a controlled way. In the current research local drug delivery devices containing 8mg of gentamicin sulphate were prepared using custom developed vacuum impregnation technique. In vitro dissolution tests showed that gentamicin release was sustained for 12h. In order to decrease gentamicin release rate, biopolymer coatings were applied and coating structure investigated. The results showed that gentamicin release can be sustained for more than 70h for poly(-caprolactone) coated calcium phosphate scaffolds. From poly lactic acid and polyvinyl alcohol coated scaffolds gentamicin was released within 20h and 50h, respectively.

Does Local Application of Strontium Increase Osteogenesis and Biomaterial Osteointegration in Osteoporotic and Other Bone Tissue Conditions: Review of Literature

Summary Osteoporosis and other pathological bone conditions can impair bone regeneration properties, consuming in increased morbidity and decreased quality of life. Changes of bone healing can result in poor osteointegration and surgical failures if implants are used. To overcome and facilitate bone regeneration, more attempts are made to develop an ideal synthetic scaffold with better biocompatibility, osteoconductivity, bioactivity, osteoinductivity and interconnected porosity. It is considered that strontium, being similar to calcium, can be incorporated into the mineral phase of the bone remodeling. This quality had led strontium to be used as an osteoporotic medication to improve quality of bone and to reduce the risk of bone fractures. Also local application of strontium has been widely used within different biomaterials in tissue engineering researches. In this review authors wanted to provide an overview about strontium, its mechanisms of action in bone tissue and initiated changes of bone remodeling within biomaterials.

3D Cone Beam Radiodensitometry in Evaluation of Hydroxyapatite (HAP)/Tissue Hybrid after Maxillary Sinus Floor Elevation

Clinical and radiological outcomes of one and two stage maxillary sinus floor augmentation with HAP granules and dental implant insertion, degree of mineralization of residual bone and augmented sinus part were evaluated. 180 dental implant insertions in 84 patients in the age from 32-68 years were included in this study. Patient clinical and CBCT (Cone Beam Computer Tomography) were analyzed by quantitative radiodensitometry using HU (Hounsfield units) after 1 to 5 years after functional loading. Four implants were lost during osseointegration phase the 176 implants survived. We found 2.5 times denser synthetic HAP/bone area comparing with residual bone. With time there was a decrease in radiodensity in HAP augmented maxillary sinus area and an increase of radiodensity in the area of residual alveolar bone.

Immunohistochemical evaluation after Sr-enriched biphasic ceramic implantation in rabbits femoral neck: comparison of seven different bone conditions

AbstractStrontium (Sr) has shown effectiveness for stimulating bone remodeling. Nevertheless, the exact therapeutic values are not established yet. Authors hypothesized that local application of Sr-enriched ceramics would enhance bone remodeling in constant osteoporosis of rabbits’ femoral neck bone. Seven different bone conditions were analyzed: ten healthy rabbits composed a control group, while other twenty underwent ovariectomy and were divided into three groups. Bone defect was filled with hydroxyapatite 30% (HAP) and tricalcium phosphate 70% (TCP) granules in 7 rabbits, 5% of Sr-enriched HAP/TCP granules in 7, but sham defect was left unfilled in 6 rabbits. Bone samples were obtained from operated and non-operated legs 12 weeks after surgery and analyzed by histomorphometry and immunohistochemistry (IMH). Mean trabecular bone area in control group was 0.393 mm2, in HAP/TCP – 0.226 mm2, in HAP/TCP/Sr – 0.234 mm2 and after sham surgery – 0.242 mm2. IMH revealed that HAP/TCP/Sr induced most noticeable increase of nuclear factor kappa beta 105 (NFkB 105), osteoprotegerin (OPG), osteocalcin (OC), bone morphogenetic protein 2/4 (BMP 2/4), collagen type 1α (COL-1α), interleukin 1 (IL-1) with comparison to intact leg; NFkB 105 and OPG rather than pure HAP/TCP or sham bone. We concluded that Sr-enriched biomaterials induce higher potential to improve bone regeneration than pure bioceramics in constant osteoporosis of femoral neck bone. Further studies on bigger osteoporotic animals using Sr-substituted orthopedic implants for femoral neck fixation should be performed to confirm valuable role in local treatment of osteoporotic femoral neck fractures in humans.

Antibacterial Efficiency of Hydroxyapatite Biomaterials with Biodegradable Polylactic Acid and Polycaprolactone Polymers Saturated with Antibiotics / Bionoārdāmu Polimēru Saturošu Un Ar Antibiotiskajām Vielām Piesūcinātu Biomateriālu Antibakteriālās Efektivitātes Noteikšana

Abstract Infections continue to spread in all fields of medicine, and especially in the field of implant biomaterial surgery, and not only during the surgery, but also after surgery. Reducing the adhesion of bacteria could decrease the possibility of biomaterial-associated infections. Bacterial adhesion could be reduced by local antibiotic release from the biomaterial. In this in vitro study, hydroxyapatite biomaterials with antibiotics and biodegradable polymers were tested for their ability to reduce bacteria adhesion and biofilm development. This study examined the antibacterial efficiency of hydroxyapatite biomaterials with antibiotics and biodegradable polymers against Staphylococcus epidermidis and Pseudomonas aeruginosa. The study found that hydroxyapatite biomaterials with antibiotics and biodegradable polymers show longer antibacterial properties than hydroxyapatite biomaterials with antibiotics against both bacterial cultures. Therefore, the results of this study demonstrated that biomaterials that are coated with biodegradable polymers release antibiotics from biomaterial samples for a longer period of time and may be useful for reducing bacterial adhesion on orthopedic implants.

Change of Biomechanical Parameters in the Lower Jaws of Rabbits with Experimental Osteoporosis after Implantation of Calcium-Phosphate Bioceramic Material in the Greater Trochanter Region

Investigation of biomechanical properties of the rabbit bone tissue from a corner of the lower jaw was done. Experimental osteoporosis was induced by ovariectomy and following injections of methylprednisolone. The defects in the greater trochanter region was created and filled with granules of a hydroxyapatite and tricalcium phosphate (HAP/TCP 30/70) or HAP/TCP 30/70 together with 5% strontium ranelate. After 3 month animals were euthanased, squared samples have been cut out from a corner of the lower jaw and tested on a bend. Results of research show, that the corner of a lower jaw in rabbit becomes more rigid after filling of defects in the greater trochanter region with granules of a hydroxyapatite and tricalcium phosphate (HAP/TCP 30/70) or granules together with strontium ranelate. The ultimate strain for the bone tissue in the 2nd and 3rd group is less, than for control group. Thus, local uses calcium – phosphatic bioceramic material around the greater trochanter region improves biomechanical parameters of a bone tissue in the lower jaw of animals.

The Level of Inflammatory Cytokines and Antimicrobial Peptides after Composite Material Implantation and Contamination with Bacterial Culture

As biomaterial implantation is a traumatic process, especially if the implanted object becomes contaminated by bacteria, it can cause a significant increase in the production of inflammatory cytokines. An increase in the level of inflammatory cytokines can be used as a marker of biomaterial associated infection (BAI) in surrounding tissues. To prevent BAI and production of inflammatory cytokines, biomaterials with antibiotics should be used, in particular biomaterials with prolonged release of antibiotics. In this in vivo study, the level of inflammatory cytokines (interleukine – 10 (IL-10), beta-defensin-2 and tumor necrosis factors (TNF-alpha)) was determined in surrounding tissues after composite material implantation in vivo and wound contamination with Staphylococcus epidermidis (S. epidermidis) or Pseudomonas aeruginosa (P. aeruginosa). The results show that the level of inflammatory cytokines is normal in surrounding tissues after implantation of biomaterials with prolonged release of antibiotics. Biomaterials with rapid release of antibiotics also show normal levels of inflammatory cytokines. The level of inflammatory cytokines increases in cases if biomaterials without antibiotics are implanted in vivo, thus being an indication of inflammation process and BAI.

Quantitative Changes of Bone Volume and Immunohistochemical Analysis of Biomarkers in Healthy, Osteoporotic and Osteoporotic Sham Surgery Affected Rabbit Bone Controls

Aim of our preliminary in vivo study was to evaluate bone regeneration properties in three different bone conditions and to compare expression of OPG, NFkB105, BMP2/4, MMP2, IL 1 and IL 10 between healthy, osteoporotic and osteoporotic sham surgery affected rabbit bone controls. Osteoporosis index was found to be higher in healthy bone, while rabbits with osteoporotic sham surgery affected bone showed slight elevation of mean trabecular field rather than rabbits with osteoporotic bone. Expression of OPG and NFkB105 was higher in healthy bone, with less equal appearance in osteoporotic and osteoporotic sham surgery affected bone. Presence of BMP2/4 and MMP2 was much higher in healthy bone, whereas twice less in osteoporotic group. Osteoporotic sham surgery affected group showed recurrence of immunoreactive structures similar to healthy group of IL 1 and IL 10. OPG and was found as the most stable indicators for bone regeneration. Decrease of BMP2/4, MMP2, IL-1 and 1L-10 in osteoporotic bone with following increase in osteoporotic sham surgery affected bone, proves the role of traumatic injury as the inducer of bone regeneration.

Autologous Fibrin Mixed with Biphasic Calcium Phosphate Bioceramic Granules Activates Encapsulation in Soft Tissue Environment

The physical, chemical and biological properties of both biphasic calcium phosphate (BCP) bioceramics and fibrin scaffolds may be cumulated for preparing advanced bone substitutes. Aim of experimental study was to evaluate histological response on implantation of synthetic biphasic HAp/TCP bioceramic granules mixed with autologous plasma derived fibrin scaffold in subcutaneous tissue of rabbits.