Experiments on physical ablation of long bone using microwave ablation; defining optimal settings using ex- and in-vivo experiments.

BACKGROUND: Improved survival of cancer patients leads to more skeletal metastatic lesions that need local therapies for tumor control and pain relief. Not all tumors are radiosensitive and alternative therapies are direly needed. Microwave ablation (MWA) is a technique for minimally invasive local tumor control by physical ablation. In soft tissue local temperature ablation is more common, but studies on bone tissue are limited. To ensure safe and effective treatment, studies on local tumor ablation in bone are needed. METHOD: Microwave ablation was performed on sheep bone, for both in- and ex-vivo settings. Both a slow-cooking MWA protocol (gradually increasing wattage in the first two minutes of ablation) and a fast-cooking protocol (no warm-up period) were used. Heat distribution through the bone during ablation was determined by measuring temperature at 10- and 15mm from the ablation probe (= needle). Ablation size after procedure was measured using nitro-BT staining. RESULTS: In-vivo ablations led to up to six times larger halos than ex-vivo with the same settings. Within both ex- and in-vivo experiments, no differences in halo size or temperature were found for different wattage levels (65W vs 80W). Compared to a fast cooking protocol, a two-minute slow cooking protocol led to increased temperatures and larger halos. Temperatures at 10- and 15mm distance from the needle no longer increased after six minutes. Halo sizes kept increasing over time without an evident plateau. CONCLUSION: Microwave ablation is technically effective for creating cell death in (sheep) long bone. It is recommended to start ablations with a slow-cooking period, gradually increasing the surrounding tissue temperature in two minutes from 40 to 90°C. Ex-vivo results cannot simply be translated to in-vivo.

Histomorphometric evaluation of the effects of mandibular advancement appliance and low level laser therapy (LLLT) with different doses on condylar cartilage and subchondral bone in rats / Evaluación histomorfométrica de los efectos del aparato de avance mandibular y la terapia con láser de bajo nivel (TLBN) con diferentes dosis en cartílago condilar y hueso subcondral en ratas

The aim of this study was to evaluate the effects of mandibular advancement appliance and low level laser therapy (LLLT) with different doses on cellular hypertrophic changes in the mandibular condyle of rats. Forty-eight 8-week-old male Wistar albino rats weighing between 260 and 280 g were randomly divided into four experimental and control groups. Group I was the control group; group II was the mandibular advancement appliance group; group III was the 8 J/cm2 (0.25 W, 20 s) laser irradiation with mandibular advancement appliance group; and group IV was the 10 J/cm2 (0.25 W, 25 s) laser irradiation with mandibular advancement appliance group. Mandibular condyle cartilage and subchondral bone changes with different LLLT dose and mandibular advancement appliance were evaluated by histomorphometrical analysis. Subchondral bone fraction results showed that there were no significant differences between groups (p<0.05). The statistically significant differences found between control group and experimental groups in anterior and posterior cartilage layers thickness (p<0.05) and (p<0.01). Posterior and anterior condylar cartilage layers of rats react differentially to LLLT and mandibular advancement application. Maximum changes in condylar cartilage layers were found in 8 J/cm2 laser irradiation with mandibular appliance group.

El objetivo de este estudio fue evaluar los efectos del aparato de avance mandibular y la terapia con láser de bajo nivel (TLBN) con diferentes dosis sobre los cambios hipertróficos celulares, en el cóndilo mandibular de ratas. Cuarenta y ocho ratas albinas macho Wistar de 8 semanas de edad con un peso de 260 y 280 g se dividieron aleatoriamente en cuatro grupos experimentales y control. El grupo I control; grupo II, dispositivos de avance mandibular; grupo III de irradiación con láser de 8 J / cm2 (0.25 W, 20 s) con el grupo dispositivos de avance mandibular; y grupo IV con irradiación láser de 10 J / cm2 (0,25 W, 25 s) con el grupo de dispositivos de avance mandibular. El cartílago del cóndilo mandibular y los cambios en el hueso subcondral con diferentes dosis de TLBN y dispositivo de avance mandibular, se evaluaron mediante análisis histomorfométrico. Los resultados de la fracción ósea subcondral indicaron que no hubo diferencias significativas entre los grupos (p <0,05). Las diferencias estadísticamente significativas encontradas entre el grupo control y los grupos experimentales, en el grosor del cartílago anterior y posterior (p<0,05) y (p<0,01). Las capas de cartílago condilar posterior y anterior de las ratas reaccionan de manera diferencial a la aplicación de TLBN y avance mandibular. Se encontraron cambios significativos en las capas de cartílago condilar con irradiación láser de 8 J /cm2 con el grupo de dispositivos mandibulares.

Basic research and clinical application of beta-tricalcium phosphate (ß-TCP).

The mechanism of bone substitute resorption involves two processes: solution-mediated and cell-mediated disintegration. In our previous animal studies, the main resorption process of beta-tricalcium phosphate (ß-TCP) was considered to be cell-mediated disintegration by TRAP-positive cells. Thus, osteoclast-mediated resorption of ß-TCP is important for enabling bone formation. We also report the results of treatment with ß-TCP graft in patients since 1989. Two to three weeks after implantation, resorption of ß-TCP occurred from the periphery, and then continued toward the center over time. Complete or nearly complete bone healing was achieved in most cases within a few years and was dependent upon the amount of implanted material, the patient's age, and the type of bone (cortical or cancellous). We have previously reported that an injectable complex of ß-TCP granules and collagen supplemented with rhFGF-2 enabled cortical bone regeneration of rabbit tibiae. Based on the experimental results, we applied this technique to the patients with femoral and humeral fractures in elderly patients, and obtained bone union.

Biochemical changes on the repair of surgical bone defects grafted with biphasic synthetic micro-granular HA + ß-tricalcium phosphate induced by laser and LED phototherapies and assessed by Raman spectroscopy.

This work aimed the assessment of biochemical changes induced by laser or LED irradiation during mineralization of a bone defect in an animal model using a spectral model based on Raman spectroscopy. Six groups were studied: clot, laser (λ = 780 nm; 70 mW), LED (λ = 850 ± 10 nm; 150 mW), biomaterial (biphasic synthetic micro-granular hydroxyapatite (HA) + ß-tricalcium phosphate), biomaterial + laser, and biomaterial + LED. When indicated, defects were further irradiated at a 48-h interval during 2 weeks (20 J/cm2 per session). At the 15th and 30th days, femurs were dissected and spectra of the defects were collected. Raman spectra were submitted to a model to estimate the relative amount of collagen, phosphate HA, and carbonate HA by using the spectra of pure collagen and biomaterials composed of phosphate and carbonate HA, respectively. The use of the biomaterial associated to phototherapy did not change the collagen formation at both 15 and 30 days. The amount of carbonate HA was not different in all groups at the 15th day. However, at the 30th day, there was a significant difference (ANOVA, p = 0.01), with lower carbonate HA for the group biomaterial + LED compared to biomaterial (p < 0.05). The phosphate HA was higher in the groups that received biomaterial grafts at the 15th day compared to clot (significant for the biomaterial; p < 0.01). At the 30th day, the phosphate HA was higher for the group biomaterial + laser, while this was lower for all the other groups. These results indicated that the use of laser phototherapy improved the repair of bone defects grafted with the biomaterial by increasing the deposition of phosphate HA.

In vitro investigation on Ho:YAG laser-assisted bone ablation underwater.

Liquid-assisted hard tissue ablation by infrared lasers has extensive clinical application. However, detailed studies are still needed to explore the underlying mechanism. In the present study, the dynamic process of bubble evolution induced by Ho:YAG laser under water without and with bone tissue at different thickness layer were studied, as well as its effects on hard tissue ablation. The results showed that the Ho:YAG laser was capable of ablating hard bone tissue effectively in underwater conditions. The penetration of Ho:YAG laser can be significantly increased up to about 4 mm with the assistance of bubble. The hydrokinetic forces associated with the bubble not only contributed to reducing the thermal injury to peripheral tissue, but also enhanced the ablation efficiency and improve the ablation crater morphology. The data also presented some clues to optimal selection of irradiation parameters and provided additional knowledge of the bubble-assisted hard tissue ablation mechanism.

In vivo effect of immobilisation of bone morphogenic protein 2 on titanium implants through nano-anchored oligonucleotides.

The aim of the present study was to test the hypothesis that immobilisation of bone morphogenic proteins on the surface of titanium implants through nano-anchored oligonucleotides can enhance peri-implant bone formation. Non-coding 60-mer DNA oligonucleotides (ODN) were anchored to the surface of custom made sandblasted acid etched (SAE) titanium screw implants through anodic polarisation, gamma-sterilised with a standard dose of 25 kGy, and were hybridised with complementary 30-mer strands of DNA oligonucleotides conjugated to rhBMP2. Blank SAE implants, SAE implants with nano-anchored ODN and SAE implants with nano-anchored ODN and non-conjugated rhBMP2 served as controls. The implants were inserted into the tibiae of 36 Sprague Dawley rats. Perforations at the head and the tip of the implants allowed for bone ingrowth. Bone ingrowth into perforations and bone implant contact (BIC) as well as bone density (BD) at a distance of 200 µm from the implant surface were assessed after 1 , 4 and 13 weeks. Implants with nano-anchored ODN strands hybridised with conjugated rhBMP2 exhibited enhanced bone ingrowth into the perforations and increased BIC after 1 week as well as increased BIC after 4 weeks compared to controls. No difference was seen after 13 weeks. Bone density around the outer implant surface did not differ significantly at any of the intervals. It is concluded that rhBMP2 immobilised on the surface of titanium implants through nano-anchored oligonucleotide strands can enhance bone implant contact. The conditions of sterilisation tested allowed for handling under clinically relevant conditions.

Raman spectroscopic study of the repair of surgical bone defects grafted or not with biphasic synthetic micro-granular HA + ß-calcium triphosphate irradiated or not with λ850 nm LED light.

The handling of bone losses due to different etiologic factors is difficult and many techniques are aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through Raman spectroscopy, the level of bone mineralization using the intensities of the Raman peaks of both inorganic (~960, ~1,070, and 1,077 cm(-1)) and organic (~1,454 and ~1,666 cm(-1)) contents of bone tissue. Forty rats were divided into four groups each subdivided into two subgroups according to the time of sacrifice (15 and 30 days). Surgical bone defects were made on the femur of each animal with a trephine drill. On animals of group clot, the defect was filled only by blood clot, on group LED, the defect filled with the clot was further irradiated. On animals of groups biomaterial and LED + biomaterial, the defect was filled by biomaterial and the last one was further irradiated (λ850 ± 10 nm, 150 mW, Φ ~ 0.5 cm(2), 20 J/cm(2)-session, 140 J/cm(2)-treatment) at 48-h intervals and repeated for 2 weeks. At both 15th and 30th days following sacrifice, samples were taken and analyzed by Raman spectroscopy. At the end of the experimental time, the intensity of hydroxyapatite (HA) (~960 cm(-1)) were higher on group LED + biomaterial and the peaks of both organic content (~1,454 and ~1,666 cm(-1)) and transitional HA (~1,070 and ~1,077 cm(-1)) were lower on the same group. It is concluded that the use of LED phototherapy associated to biomaterial was effective in improving bone healing on bone defects as a result of the increasing deposition of HA measured by Raman spectroscopy.

Influence of the λ780nm laser light on the repair of surgical bone defects grafted or not with biphasic synthetic micro-granular hydroxylapatite+Beta-Calcium triphosphate.

The treatment of bone loss due to different etiologic factors is difficult and many techniques aim to improve repair, including a wide range of biomaterials and, recently, photobioengineering. This work aimed to assess, through histological analysis The aim of this study was to assess, by light microscopy, the repair of bone defects grafted or not with biphasic synthetic micro-granular Calcium hydroxyapatite (HA)+Beta-TCP associated or not with Laser phototherapy - LPT (λ780nm). Forty rats were divided into 4 groups each subdivided into 2 subgroups according to the time of sacrifice (15 and 30days). Surgical bone defects were made on femur of each animal with a trephine drill. On animals of Clot group the defect was filled only by blood clot, on Laser group the defect filled with the clot was further irradiated. On animals of Biomaterial and Laser+Biomaterial groups the defect was filled by biomaterial and the last one was further irradiated (λ780nm, 70mW, spot size∼0.4cm(2), 20J/cm(2)-session, 140J/cm(2)-treatment) in four points around the defect at 48-h intervals and repeated for 2weeks. At both 15th and 30th days following sacrifice, samples were taken and analyzed by light microscopy. Many similarities were observed histologically between groups on regards bone reabsorption and neoformation, inflammatory infiltrate and collagen deposition. The criterion degree of maturation, marked by the presence of basophilic lines, indicated that the use of LPT associated with HA+Beta TCP graft, resulted in more advanced stage of bone repair at the end of the experiment.

Evaluation of four biodegradable, injectable bone cements in an experimental drill hole model in sheep.

Four cement applications were tested in this investigation. Two dicalcium phosphate dihydrate (DCPD-brushite) hydraulic cements, an apatite hydraulic fiber loaded cement, and a calcium sulfate cement (Plaster of Paris) were implanted in epiphyseal and metaphyseal cylindrical bone defects in sheep. The in vivo study was performed to assess the biocompatibility and bone remodeling of four cement formulations. After time periods of 2, 4, and 6 months, the cement samples were clinically and histologically evaluated. Histomorphometrically, the amount of new bone formation, fibrous tissue, and bone marrow and the area of remaining cement were measured. In all specimens, no signs of inflammation were detectable either macroscopically or microscopically. Cements differed mainly in their resorption time. Calcium sulfate was already completely resorbed at 2 months and showed a variable amount of new bone formation and/or fibrous tissue in the original drill hole over all time periods. The two DCPD cements in contrast were degraded to a large amount at 6 months, whereas the apatite was almost unchanged over all time periods.

Comparison of Er:YAG laser and surgical drill for osteotomy in oral surgery: an experimental study.

PURPOSE: High-energy lasers have been proposed as an alternative to the conventional surgical drill in oral and maxillofacial surgery. The aims of this study were to compare thermal changes of the bone surface, procedure time, and volume of the removed bone after drilling with an erbium (Er):yttrium-aluminum-garnet (YAG) laser versus a low-speed surgical drill. The bone sections were observed under light microscopy and examined histologically. MATERIAL AND METHODS: Thirty bone blocks were prepared from porcine ribs. On each block 2 holes (tunnel preparations) were performed using a low-speed, 1.0-mm-wide, surgical pilot drill and an Er:YAG laser (pulse energy, 1,000 mJ; pulse duration, 300 µs; frequency, 20 Hz). The temperature induced by the preparation techniques was measured using an infrared camera. The removed bone volume was calculated by a modified mathematical algorithm. The time required for the preparation was measured with a digital stopwatch and a time-measurement instrument integrated within the computer program. The cortical and spongiose surfaces of the specimens were examined microscopically and histologically under a light microscope with a high-resolution camera. RESULTS: The Er:YAG laser removed significantly more bone tissue than the drill (P < .01) in a significantly shorter time (P < .01). The temperature was statistically lower during the laser preparation (P < .01). Cavities prepared with the laser were regular with clear sharp edges and knifelike cuts. In the drill group, the preparations exhibited irregular edges full of bone fragments and fiberlike debris. Histologic examination of the laser sides showed a 30-µm-thick altered sublayer. The tissue in the drill group was covered with a smear layer without any alterations. CONCLUSIONS: The Er:YAG laser produced preparations with regular and sharp edges, without bone fragments and debris, in a shorter time, and with less generated heat. Thermal alterations in the treated surface were minimal.

Impact of 4-methylbenzylidene camphor, daidzein, and estrogen on intact and osteotomized bone in osteopenic rats.

The study investigated the influence of 4-methylbenzylidene camphor (4-MBC), daidzein, and estradiol-17ß-benzoate (E(2)) on either intact or osteotomized cancellous bone in ovariectomized (Ovx) rats. Three-month old Ovx rats were fed with soy-free (SF) diet over 8 weeks; thereafter, bilateral transverse metaphyseal osteotomy of tibia was performed and rats were divided into groups: rats fed with SF diet and SF diet supplemented with 4-MBC (200 mg), daidzein (50 mg), or E(2) (0.4 mg) per kilogram body weight. After 5 or 10 weeks, computed tomographical, biomechanical, histological, and ashing analyses were performed in lumbar spine and tibia of 12 rats from each group. 4-MBC and E(2) improved bone parameters in lumbar spine and tibia, were not favorable for osteotomy healing, and decreased serum osteocalcin level. However, daidzein improved bone parameters to a lesser extent and facilitated osteotomy healing. For lumbar spine, the bone mineral density was 338±9, 346±5, 361±6, and 360±5 mg/cm(3) in SF, daidzein, 4-MBC, and E(2), respectively, after 10 weeks. For tibia, the yield load was 98±5, 114±3, 90±2, and 52±4 N in SF, daidzein, 4-MBC, and E(2), respectively, after 10 weeks. Serum daidzein was 54±6 ng/ml in daidzein group and equol was not detected. Alp and Igf1 genes were down-regulated in callus after daidzein and E(2) compared with 4-MBC (week 5). The response of bone tissue and serum markers of bone metabolism could be ordered: daidzein<4-MBC

Mechanical evaluation of the influence of low-level laser therapy in secondary stability of implants in mice shinbones.

The present work evaluates mechanically the bone-implant attachment submitted or not to low-level laser therapy, with wavelength of 795 nm, in a continuous way, with power of 120 mW. The implant was placed in one of the shinbones of 24 mice, randomly distributed into two groups. The experimental group was submitted to six laser applications, divided into four points previously established, two lateral and two longitudinal, six times 8 J/cm2 with an interval of 2 days, totaling the dose of 48 J/cm2. The control group did not receive laser therapy. The interval between applications was 48 h and the irradiations began immediately after the end of the implant surgeries. The two groups were killed on the 14th day and a bone block of the area was removed where the implant was inserted. A torque machine was used to measure the torque needed for loosening the implants. A statistically significant difference was observed between the two groups. The experimental group presented larger difficulty for breaking up the implant interface with the bone block than the control group. It can be concluded that with the animal model and the protocol of irradiation present in this study, the laser therapy demonstrated capacity to increase the attachment bone implant.

[Perspectives of clinical stem cell therapy in the treatment of musculoskeletal diseases in Germany]. / Perspektiven klinischer mesenchymaler Stammzelltherapie bei muskuloskeletalen Erkrankungen in Deutschland.

AIM: The treatment of large bone defects remains a challenge for the orthopaedic surgeon. Regenerative therapies with the use of mesenchymal stem cells (MSC) may provide an alternative to autogenous bone transplantation, callus distraction or the use of allografts. MATERIAL AND METHODS: On the occasion of an expert workshop of the German Society for Orthopaedic and Trauma Surgery, a literature search regarding studies with the use of MSC was performed to evaluate its potential for future clinical studies. Furthermore, the legislative requirements were examined. RESULTS: Various in vitro and animal studies showed the benefit of MSC in bone regeneration. However, there are sparse data from clinical studies. Due to recent legislative changes there are several regulatory demands to meet if clinical studies are performed with MSC. CONCLUSIONS: For further evaluation of the role of MSC in the treatment of bone defects there is a need for clinical trials. The current paper provides some assistance for the successful application for clinical trials with MSC. Planning and performance of these studies may require early consultation with the regulatory authorities and cooperation of research centres in order to obtain authorisation for the evaluation of MSC. Preclinical data have to be obtained according to good laboratory practice with equivalent protocols that will be used in the clinical trials. In the latter the implementation of the guidelines for good clinical practice are mandatory.

Glucocorticoid induced osteopenia in cancellous bone of sheep: validation of large animal model for spine fusion and biomaterial research.

STUDY DESIGN: Glucocorticoid with low calcium and phosphorus intake induces osteopenia in cancellous bone of sheep. OBJECTIVE: To validate a large animal model for spine fusion and biomaterial research. SUMMARY OF BACKGROUND DATA: A variety of ovariectomized animals has been used to study osteoporosis. Most experimental spine fusions were based on normal animals, and there is a great need for suitable large animal models with adequate bone size that closely resemble osteoporosis in humans. METHODS: Eighteen female skeletal mature sheep were randomly allocated into 3 groups, 6 each. Group 1 (GC-1) received prednisolone (GC) treatment (0.60 mg/kg/day, 5 times weekly) for 7 months. Group 2 (GC-2) received the same treatment as GC-1 for 7 months followed by 3 months without treatment. Group 3 was left untreated and served as the controls. All sheep received restricted diet with low calcium and phosphorus during experiment. After killing the animals, cancellous bone specimens from the vertebra, femurs, and tibias were micro-CT scanned and tested mechanically. Serum biomarkers were determined. RESULTS: In lumbar vertebra, the GC treatment resulted in significant decrease of cancellous bone volume fraction and trabecular thickness, and bone strength. However, the microarchitecture and bone strength of GC-2 recovered to a similar level of the controls. A similar trend of microarchitectural changes was also observed in the distal femur and proximal tibia of both GC treated sheep. The bone formation marker serum-osteocalcin was largely reduced in GC-1 compared to the controls, but recovered with a rebound increase at month 10 in GC-2. CONCLUSION: The current investigation demonstrates that the changes in microarchitecture and mechanical properties were comparable with those observed in humans after long-term GC treatment. A prolonged GC treatment is needed for a long-term observation to keep osteopenic bone. This model resembles long-term glucocorticoid treated osteoporotic model, and is useful in preclinical studies.

Pulsed electromagnetic fields as adjuvant therapy in bone healing and peri-implant bone formation: an experimental study in rats.

The objective of this study was to determine whether short exposure to pulsed electromagnetic fields (PEMF) accelerates bone repair and peri-implant bone formation in a rat tibial model at different times. Sixty Wistar rats were employed. Sterile custom fabricated commercially pure cylinder threaded titanium implants were placed in the right tibial crest, and an osteotomy was performed in the left tibial crest of each animal. Thirty rats were treated with PEMF (72 mT 50Hz), twice a day in sessions of 30 minutes each, and 30 rats of the control group were sham-treated. Rats were sacrificed at 5, 10 and 20 days postsurgery (n = 10 per group). Tibias were fixed in formaldehyde and decalcified, embedded in paraffin, and stained with hematoxylin-eosin (half samples of left tibias), or they were included in methylmethacrylate, grinded and polished (right tibias and half samples of left tibias). Bone healing was evaluated by image analysis in terms of ossification area, and perimeter and diameter of the lesion. Peri-implant ossification was assessed in terms of ossification percentage. At day 10 the area of ossification index was higher in the PEMF group than in the control group (p = 0.012). At day 20 the osteotomies of the PEMF group were almost completely remodeled. The ossification percentage was higher in the PEMF group (p = 0.018). In conclusion, short daily electromagnetic stimulation appears to be a promising treatment for acceleration of both bone-healing and peri-implant bone formation.

Pulsed electromagnetic fields as adjuvant therapy in bone healing and peri-implant bone formation: an experimental study in rats

El objetivo del presente trabajo fue evaluar a diferentes tiemposen un modelo experimental en tibias de rata, el efecto de la exposición breve a campos electromagnéticos pulsantes(PEMF, del inglés Pulsed lectroMagnetic Fields) sobre la reparación y formación ósea peri-implantaria. Se utilizaron 60 ratas Wistar. En la cresta tibial derecha de cada animal se colocó un implante roscado de titanio comercialmentepuro y en la cresta tibial izquierda se efectuó una osteotomía. La mitad de los animales fueron tratados con PEMF (72 mT, 50Hz) dos veces por día (30 minutos por sesión), y la otra mitadconstituyó el grupo control. Las ratas se sacrificaron a los 5, 10 y 20 días postcirugía (n=10 por grupo). La mitad de las tibias derechas se descalcificaron,incluyeron en parafina y tiñeron con hemato xilina-eosina, mientras que al resto se las incluyó en metil-metacrilato y se realizaron cortes por desgaste. Se evaluó el área de osificación, el perímetro y el diámetro de las osteotomías mediante un analizadorde imágenes. Para evaluar la osificación peri-implante se obtuvo el porcentaje de osificación. Al día 10 el índice del área de osificación fue significativamentemayor en el grupo PEMF que en el control (190,6±13,6 vs. 147,9±6,3; p=0,012). Al día 20, las osteotomías del grupo PEMF estaban, en su mayor parte remodeladas. El porcentaje de osificación fue mayor en el grupo PEMF respecto al control (51,9±10,4 por ciento vs. 36±12.1 por ciento; p=0,018). La breve estimulación electromagnética pulsante diaria sería un tratamiento promisorio para facilitar la reparación ósea y peri-implantaria.

Biomaterial osseointegration enhancement with biophysical stimulation.

Despite the ongoing improvement in implant characteristics, bone intrinsic potential for regeneration may be stimulated with adjuvant therapies to standard surgical procedures, as it is important to achieve the best possible implant osseointegration into the adjacent bone and to ensure therefore long-term implant stability. For this purpose various pharmacological, biological or biophysical modalities have been developed, such as bone grafting materials, pharmacological agents, growth factors and bone morphogenetic proteins. Biophysical stimulation of osseointegration includes two non-invasive and safe methods that have been initially developed to enhance fracture healing: pulsed electromagnetic fields (PEMFs) and lowintensity ultrasounds (LIPUS), for which most studies confirm their beneficial effects. The present paper is an overview of bone-implant osseointegration and the current trends on its enhancement, focusing mainly on the two methods of biophysical stimulation.

Effects of fibrin sealer and resorbable gelatin on the repair of osseous defects in rat tibia.

Gelfoam - a biologically resorbable gelatin sponge - has the function of restricting hemorrhage, providing platelet rupture, and supporting fibrin threads. Beriplast - a fibrinogen-thrombin compound - is used to adhere tissues, to consolidate sutures and in hemostasis. The objective of this study was to perform a histological analysis of the effects of haemostatic agents on osseous repair. These materials were inserted into surgical sites in young rat right and left tibiae. After the observation periods of 7, 14, 30 and 45 days, according to the bioethic protocol, the animals were killed, the tibiae were removed and fixed in 10% formalin and decalcified in equal parts of formic acid and sodium citrate solutions. After routine processing, the specimens were embedded in paraffin for microtomy. Analysis of the results demonstrated that the haemostatic agents are effective in controlling hemorrhage; they stimulate osteogenesis, featuring a pattern of osseous tissue formation similar to the control pattern, although the amount of osseous trabeculae was superior, especially in the Gelfoam group in the periods of 7 and 14 days; 30 days after surgery, the delay in tissue healing in the control group in relation to the experimental groups started to decrease, and the control and experimental groups exhibited similar tissue repair after 45 days, when all the groups exhibited secondary osseous tissue.