Oscar Peitl

Compositional and microstructural design of highly bioactive P2O5-Na2O-CaO-SiO2 glass-ceramics.

Bioactive glasses having chemical compositions between 1Na(2)O-2CaO-3SiO(2) (1N2C3S) and 1.5Na(2)O-1.5CaO-3SiO(2) (1N1C2S) containing 0, 4 and 6 wt.% P(2)O(5) were crystallized through two stage thermal treatments. By carefully controlling these treatments we separately studied the effects on the mechanical properties of two important microstructural features not studied before, crystallized volume fraction and crystal size. Fracture strength, elastic modulus and indentation fracture toughness were measured as a function of crystallized volume fraction for a constant crystal size. Glass-ceramics with a crystalline volume fraction between 34% and 60% exhibited a three-fold improvement in fracture strength and an increase of 40% in indentation fracture toughness compared with the parent glass. For the optimal crystalline concentration (34% and 60%) these mechanical properties were then measured for different grain sizes, from 5 to 21 μm. The glass-ceramic with the highest fracture strength and indentation fracture toughness was that with 34% crystallized volume fracture and 13 μm crystals. Compared with the parent glass, the average fracture strength of this glass-ceramic was increased from 80 to 210 MPa, and the fracture toughness from 0.60 to 0.95 MPa.m(1/2). The increase in indentation fracture toughness was analyzed using different theoretical models, which demonstrated that it is due to crack deflection. Fortunately, the elastic modulus E increased only slightly; from 60 to 70 GPa (the elastic modulus of biomaterials should be as close as possible to that of cortical bone). In summary, the flexural strength of our best material (215 MPa) is significantly greater than that of cortical bone and comparable with that of apatite-wollastonite (A/W) bioglass ceramics, with the advantage that it shows a much lower elastic modulus. These results thus provide a relevant guide for the design of bioactive glass-ceramics with improved microstructure.

Efficacy of a bioactive glass–ceramic (Biosilicate®) in the maintenance of alveolar ridges and in osseointegration of titanium implants

OBJECTIVES The aims of this research were to evaluate the efficacy of a bioactive glass-ceramic (Biosilicate) and a bioactive glass (Biogran) placed in dental sockets in the maintenance of alveolar ridge and in the osseointegration of Ti implants. MATERIAL AND METHODS Six dogs had their low premolars extracted and the sockets were implanted with Biosilicate, Biogran particles, or left untreated. After the extractions, measurements of width and height on the alveolar ridge were taken. After 12 weeks a new surgery was performed to take the final ridge measurements and to insert bilaterally three Ti implants in biomaterial-implanted and control sites. Eight weeks post-Ti implant placement block biopsies were processed for histological and histomorphometric analysis. The percentages of bone-implant contact (BIC), of mineralized bone area between threads (BABT), and of mineralized bone area within the mirror area (BAMA) were determined. RESULTS The presence of Biosilicate or Biogran particles preserved alveolar ridge height without affecting its width. No significant differences in terms of BIC, BAMA, and BABT values were detected among Biosilicate, Biogran, and the non-implanted group. CONCLUSIONS The results of the present study indicate that filling of sockets with either Biosilicate or Biogran particles preserves alveolar bone ridge height and allows osseointegration of Ti implants.

A novel bioactive glass-ceramic for treating dentin hypersensitivity

Dentin hypersensitivity (DH) is a painful response to stimulus applied to the open dentinal tubules of a vital tooth. Its a common oral condition, however, without an ideal treatment available yet. This work evaluated in vitro the effect of micron-sized particles from a novel bioactive glass-ceramic (Biosilicate) in occluding open dentinal tubules. A dentin disc model was employed to observe comparatively, using scanning electron microscopy (SEM), dentinal tubule occlusion by different products and deposition of hydroxyl carbonate apatite (HCA) on dentin surface by Biosilicate, after a single application: G1 - Dentifrice with potassium nitrate and fluoride; G2 - Two-step calcium phosphate precipitation treatment; G3 - Water-free gel containing Biosilicate particles (1%); G4 - Biosilicate particles mixed with distilled water in a 1:10 ratio; all of them after 1, 12 and 24 hours of immersion in artificial saliva. Fourier transform infrared spectroscopy (FTIR) was performed to detect HCA formation on dentin discs filled with Biosilicate after 2 minutes, 30 minutes and 12 hours of immersion in artificial saliva. SEM showed a layer of HCA formed on dentin surface after 24 hours by G4. G1, G2 and G3 promoted not total occlusion of open dentinal tubules after 24 hours. FTIR showed HCA precipitation on the dentin surface induced by Biosilicate after 30 minutes. The micron-sized particles from the bioactive glass-ceramic thus were able to induce HCA deposition in open dentinal tubules in vitro. This finding suggests that Biosilicate may provide a new option for treating DH.

In vivo biological performance of a novel highly bioactive glass-ceramic (Biosilicate®): A biomechanical and histomorphometric study in rat tibial defects

This study aimed to investigate bone responses to a novel bioactive fully crystallized glass-ceramic of the quaternary system P(2)O(5)-Na(2)O-CaO-SiO(2) (Biosilicate®). Although a previous study demonstrated positive effects of Biosilicate® on in vitro bone-like matrix formation, its in vivo effect was not studied yet. Male Wistar rats (n = 40) with tibial defects were used. Four experimental groups were designed to compare this novel biomaterial with a gold standard bioactive material (Bioglass® 45S5), unfilled defects and intact controls. A three-point bending test was performed 20 days after the surgical procedure, as well as the histomorphometric analysis in two regions of interest: cortical bone and medullary canal where the particulate biomaterial was implanted. The biomechanical test revealed a significant increase in the maximum load at failure and stiffness in the Biosilicate® group (vs. control defects), whose values were similar to uninjured bones. There were no differences in the cortical bone parameters in groups with bone defects, but a great deal of woven bone was present surrounding Biosilicate® and Bioglass® 45S5 particulate. Although both bioactive materials supported significant higher bone formation; Biosilicate® was superior to Bioglass® 45S5 in some histomorphometric parameters (bone volume and number of osteoblasts). Regarding bone resorption, Biosilicate® group showed significant higher number of osteoclasts per unit of tissue area than defect and intact controls, despite of the non-significant difference in the osteoclastic surface as percentage of bone surface. This study reveals that the fully crystallized Biosilicate® has good bone-forming and bone-bonding properties.

Biosilicate® and low-level laser therapy improve bone repair in osteoporotic rats

The aim of this study was to investigate the effects of a novel bioactive material (Biosilicate®) and low‐level laser therapy (LLLT) on bone fracture consolidation in osteoporotic rats. Forty female Wistar rats were submitted to ovariectomy (OVX) to induce osteopenia. Eight weeks after surgery, the animals were randomly divided into four groups of 10 animals each: a bone defect control group (CG); a bone defect filled with Biosilicate group (BG); a bone defect filled with Biosilicate and irradiated with LLLT at 60 J/cm2 group (BG60); and a bone defect filled with Biosilicate and irradiated with LLLT at 120 J/cm2 group (BG120). Bone defects were surgically performed on both tibias. The size of particle used for Biosilicate was 180–212 µm. Histopathological analysis showed that bone defects were predominantly filled with the biomaterial in specimens treated with Biosilicate. LLLT with either 60 or 120 J/cm2 was able to increase collagen, Cbfa‐1, VGEF and COX‐2 expression in the circumjacent cells of the biomaterial. A morphometric analysis revealed that the Biosilicate + laser groups showed a higher amount of newly formed bone. Our results indicate that laser therapy improves bone repair process in contact with Biosilicate as a result of increasing bone formation, as well as COX‐2 and Cbfa‐1 immunoexpression, angiogenesis and collagen deposition in osteoporotic rats. Copyright

The effect of a novel crystallised bioactive glass-ceramic powder on dentine hypersensitivity: a long-term clinical study

The aim of this comparative clinical study was to evaluate a novel bioactive glass-ceramic (Biosilicate® 1-20 μm particles) to treat dentine hypersensitivity (DH). Volunteers (n = 120 patients/ 230 teeth) received the following treatments: G1-Sensodyne® , G2-SensiKill®, G3-Biosilicate® incorporated in a 1% water-free-gel and G4-Biosilicate® mixed with distilled water at 1:10 ratio. G1 and G3 were applied at home, daily for 30 days; G2 and G4 were applied once a week by a dentist (four applications). A visual analogue scale (VAS) was employed to evaluate pain for each quadrant in one sensitive tooth at baseline, weekly during treatment and during a 6-month follow-up period. Dentine hypersensitivity values (G1/n= 52), (G2/n =62), (G3/n = 59) and (G4/n = 59) were analysed with Kruskal-Wallis/Dunn tests. All the products were efficient in reducing DH after 4 weeks. Among the four materials tested, G4 demonstrated the best clinical performance and provided the fastest treatment to reduce DH pain. Distilled water proved to be an adequate vehicle to disperse Biosilicate®. Low DH scores were maintained during the 6-month follow-up period. The hypothesis that the novel bioactive glass-ceramic may be an efficient treatment for DH was confirmed.

Effects of biosilicate(®) scaffolds and low-level laser therapy on the process of bone healing.

OBJECTIVE This study aimed to investigate the in vivo tissue performance of the association of Biosilicate(®) scaffolds and low-level laser therapy (LLLT) in a tibial bone defects model in rats. BACKGROUND DATA Many studies have been demonstrating the osteogenic potential of Biosilicate and LLLT. However, there is a need to investigate the effects of both treatments for bone consolidation. METHODS The animals were divided into control group (CG), Biosilicate scaffold group (BG), and Biosilicate scaffolds plus LLLT group (BLG). Animals were euthanized after 15, 30, and 45 days post-injury. RESULTS The histological analysis revealed that all the experimental groups showed inflammatory infiltrate and granulation tissue, at the area of the defect at day 15. After 30 days, CG still showed granulation tissue and bone ingrowth. Both Biosilicate groups presented newly formed bone and interconected trabeculae. At 45 days, CG showed immature newly formed bone. A more mature newly formed bone was observed in BG and BLG. On day 15, BG demonstrated a statistically higher expression of cyclooxygenase (COX)-2 compared with CG and BLG. No statistically significant difference was observed in COX-2 immunoexpression among the groups at 30 and 45 days. Similar expression of bone morphogenetic protein (BMP)-9 was demonstrated for all experimental groups at 15 and 30 days. At 45 days, the BMP-9 immunoexpression was statistically upregulated in the BLG compared with the CG and BG. No statistically significant difference was observed in the receptor activator of nuclear factor kappa-B ligand (RANKL) immunoexpression among the groups in all periods evaluated. Biosilicate groups presented a decrease in biomechanical properties compared with CG at 30 and 45 days post-surgery. CONCLUSIONS Our findings suggest that Biosilicate presented osteogenic activity, accelerating bone repair. However, laser therapy was not able to enhance the bioactive properties of the Biosilicate.

Thermal shock properties of chemically toughened borosilicate glass

Abstract This paper describes an experimental test of the unified theory of thermal shock. A borosilicate glass (78.1%SiO 2 –13.3%B 2 O 3 –4.7%Na 2 O–3.4%Al 2 O 3 ) subjected to ion-exchange in molten KNO 3 , was used. The theory predicts the critical temperature difference for fracture initiation by thermal shock; however, it overestimates the number of cracks which propagate simultaneously. Despite that fact, taken into account the numerous assumptions of the theoretical model and the possible experimental errors, our results indicate a fair agreement between theory and experiment.

Biocompatibility Analysis of Bioglass® 45S5 and Biosilicate® Implants in the Rabbit Eviscerated Socket

Purpose: Bioactive glass and bioactive glass-ceramic cone implants were placed in the rabbit eviscerated socket to assess their biocompatibility. Methods: Fifty-one Norfolk albino rabbits underwent evisceration of the right eye followed by implantation of cones made from Bioglass® 45S5 (control group) and two types of bioactive glass-ceramic (Biosilicate®), a single- and a two-phase bioactive glass-ceramic implants into the scleral cavity. Postoperative reactions, animal behavior and socket conditions were monitored daily. Clinical exam, biochemical evaluations, and orbit computed tomographic scan were done at 7, 90, and 180 days post-procedure. After that, the animals were euthanized, and the orbital content was removed and prepared to light microscopy with morphometric evaluation and scanning electron microscopy examination. Statistical analysis was done by parametric and non-parametric analysis of variance, complemented by Dunn’s and Tukey’s tests (p < 0.05). Results: All animals did not develop systemic toxicity throughout the experimental period and also did not have orbit infection, implant migration or extrusion. Morphological analysis demonstrated pseudocapsule around all implants. Bioglass® and single-phase Biosilicate® implants induced less inflammation and pseudocapsule formation than two-phase Biosilicate® cones. Seven days post-procedure, the inflammatory reaction was intense and gradually decreased throughout the experiment. Tissue reaction was least intense in animals receiving Bioglass® implants. Conclusions: We observe discrete differences among the studied materials, with best responses obtained with use of Bioglass® 45S5 and single-phase Biosilicate®. The authors agree these implants might be useful in the management of the anophthalmic socket.

Bone response to biosilicates® with different crystal phases

The aim of this study was to investigate the histological and histomorphometrical bone response to three Biosilicates with different crystal phases comparing them to Bioglass 45S5 implants used as control. Ceramic glass Biosilicate and Bioglass 45S5 implants were bilaterally inserted in rabbit femurs and harvested after 8 and 12 weeks. Histological examination did not revealed persistent inflammation or foreign body reaction at implantation sites. Bone and a layer of soft tissue were observed in close contact with the implant surfaces in the medullary canal. The connective tissue presented few elongated cells and collagen fibers located parallel to implant surface. Cortical portion after 8 weeks was the only area that demonstrated significant difference between all tested materials, with Biosilicate 1F and Biosilicate 2F presenting higher bone formation than Bioglass 45S5 and Biosilicate vitreo (p=0.02). All other areas and periods were statistically non-significant (p>0.05). In conclusion, all tested materials were considered biocompatible, demonstrating surface bone formation and a satisfactory behavior at biological environment.