Characterizing the hierarchical structures of bioactive sol-gel silicate glass and hybrid scaffolds for bone regeneration

Bone is the second most widely transplanted tissue after blood. Synthetic alternatives are needed that can reduce the need for transplants and regenerate bone by acting as active temporary templates for bone growth. Bioactive glasses are one of the most promising bone replacement/regeneration materials because they bond to existing bone, are degradable and stimulate new bone growth by the action of their dissolution products on cells. Sol-gel-derived bioactive glasses can be foamed to produce interconnected macropores suitable for tissue ingrowth, particularly cell migration and vascularization and cell penetration. The scaffolds fulfil many of the criteria of an ideal synthetic bone graft, but are not suitable for all bone defect sites because they are brittle. One strategy for improving toughness of the scaffolds without losing their other beneficial properties is to synthesize inorganic/organic hybrids. These hybrids have polymers introduced into the sol-gel process so that the organic and inorganic components interact at the molecular level, providing control over mechanical properties and degradation rates. However, a full understanding of how each feature or property of the glass and hybrid scaffolds affects cellular response is needed to optimize the materials and ensure long-term success and clinical products. This review focuses on the techniques that have been developed for characterizing the hierarchical structures of sol-gel glasses and hybrids, from atomicscale amorphous networks, through the covalent bonding between components in hybrids and nanoporosity, to quantifying open macroporous networks of the scaffolds. Methods for non-destructive in situ monitoring of degradation and bioactivity mechanisms of the materials are also included. © 2012 The Royal Society.

Polycaprolactone fibres as a potential delivery system for collagen to support bone regeneration

Poly(e-caprolactone) (PCL) is biocompatible, non-immunogenic and non-toxic, and slowly degrades, allowing sufficient time for tissue regeneration. PCL has the potential for application in bone and cartilage repair as it may provide the essential structure required for bone regeneration, however, an ideal scaffold system is still undeveloped. PCL fibres were prepared using the gravity spinning technique, in which collagen was either incorporated into or coated onto the 'as-spun' fibres, in order to develop novel biodegradable polymer fibres which will effectively deliver collagen and support the attachment and proliferation of human osteoblast (HOB) cells for bone regeneration. The physical and mechanical characteristics and cell fibre interactions were analysed. The PCL fibres were found to be highly flexible and inclusion of collagen did not alter the mechanical properties of PCL fibres. Overall, HOB cells were shown to effectively adhere and proliferate on all fibre platforms tested, although proliferation rates were enhanced by surface coating PCL fibres with collagen compared to PCL fibres incorporating collagen and PCL-only fibres. These findings highlight the potential of using gravity spun PCL fibres as a delivery platform for extracellular matrix proteins, such as collagen, in order to enhance cell adherence and proliferation for tissue repair.

Development of novel multi-substituted apatite nanophases with advanced functionalities for bone regeneration

In the field of bone substitutes is highly researched an innovative material able to fill gaps with high mechanical performances and able to stimulate cell response, permitting the complete restoration of the bone portion. In this respect, the synthesis of new bioactive materials able to mimic the compositional, morphological and mechanical features of bone is considered as the elective approach for effective tissue regeneration. Hydroxyapatite (HA) is the main component of the inorganic part of bone. Additionally ionic substitution can be performed in the apatite lattice producing different effects, depending from the selected ions. Magnesium, in substitution of calcium, and carbonate, in substitution of phosphate, extensively present in the biological bones, are able to improve properties naturally present in the apatitic phase, (i.e. biomimicry, solubility e osteoinductive properties). Other ions can be used to give new useful properties, like antiresorptive or antimicrobial properties, to the apatitic phase. This thesis focused on the development of hydroxyapatite nanophases with multiple ionic substitutions including gallium, or zinc ions, in association with magnesium and carbonate, with the purpose to provide double synergistic functionality as osteogenic and antibacterial biomaterial. Were developed bioactive materials based on Sr-substituted hydroxyapatite in the form of sintered targets. The obtained targets were treated with Pulsed Plasma Deposition (PED) resulting in the deposition of thin film coatings able to improve the roughness and wettability of PEEK, enhancing its osteointegrability. Were investigated heterogeneous gas-solid reactions, addressed to the biomorphic transformations of natural 3D porous structures into bone scaffolds with biomimetic composition and hierarchical organization, for application in load-bearing sites. The kinetics of the different reactions of the process were optimized to achieve complete and controlled phase transformation, maintaining the original 3-D morphology. Massive porous scaffolds made of ion-substituted hydroxyapatite and bone-mimicking structure were developed and tested in 3-D cell culture models.

Diagnosis and treatment of extraction sockets in preparation for implant placement: report of three cases

This article addresses diagnostic parameters that should be assessed in the treatment of extraction sockets with dental implant placement by presenting three case reports that emphasize the relevance of the amount of remaining bone walls. Diagnosis was based on the analysis of clinical and radiographic parameters (e.g.: bone defect morphology, remaining bone volume, presence of infections on the receptor site). Case 1 presents a 5-wall defect in the maxillary right central incisor region with severe root resorption, which was treated with immediate implant placement. Cases 2 and 3 present, respectively, two- and three-wall bone defects that did not have indication for immediate implants. These cases were first submitted to a guided bone regeneration (GBR) procedure with bone graft biomaterial and membrane barriers, and the implants were installed in a second surgical procedure. The analysis of the preoperative periodontal condition of the adjacent teeth and bone defect morphology is extremely important because these factors determine the choice between immediate implant or GBR treatment followed by implant installation in a subsequent intervention.

Immediate implants placed into infected sockets: a case report with 3-year follow-up

The esthetics and functional integrity of the periodontal tissue may be compromised by dental loss. Immediate implants became a viable option to maintain the periodontal architecture because of their anatomic compatibility with the dental socket and the possibility of eliminating local contamination. This article describes the procedure of immediate implant placement in the anterior maxilla replacing teeth with chronic periapical lesions, which were condemned due to endodontic lesions persisting after failed endodontic treatment and endodontic surgery, and discusses the relationship between the procedure and periapical lesions. Surgical removal of hopeless teeth 11, 12 and 21 was performed conservatively in such a way to preserve the anatomy and gingival esthetics. A second surgical access was gained at the apical level, allowing the debridement of the surgical chamber for elimination of the periapical lesion, visual orientation for setting of the implants and filling of the surgical chamber with xenogenous bovine bone graft. After this procedure, the bone chamber was covered with an absorbent membrane and the healing screws were positioned on the implants. Later, a provisional partial removable denture was installed and the implants were inserted after 6 months. After 3 years of rehabilitation, the implants present satisfactory functional and esthetic conditions, suggesting that immediate implant placement combined with guided bone regeneration may be indicated for replacing teeth lost due to chronic periapical lesions with endodontic failure history in the anterior maxilla.

Nonsurgical Periodontal Therapy Combined with Laser and Photodynamic Therapies for Periodontal Disease in Immunosuppressed Rats

Background. Periodontal disease is often associated with systemic diseases and is characterized by destruction of the tissues supporting the teeth. Patients using immunosuppressive drugs such as tacrolimus are among those who suffer from tissue destruction. Objective. We sought to evaluate the effects of laser and photodynamic therapies (PDT; nonsurgical) as an adjunct to scaling and rootplaning (SRP) in the treatment of corona-induced periodontitis in rats immunosuppressed with tacrolimus (Prograf). Materials and Methods. The animals were divided into 5 groups. Each groups had 6 rats. Group I, the control group, received only saline solution throughout the study period of 42 days and did not receive periodontal treatment; group II received saline solution and SRP; group III received tacrolimus (1 mg/kg per day) and was treated with SRP; group IV animals were treated identically to group III and then administered laser treatment; and in group V, the animals were treated identically to group III and then administered PDT. Results. Statistical analysis indicated decreased bone loss with the progression of time (P = .035). There was no difference between the bone loss associated with the types of treatment administered to groups I, II, and III (P > .9) or groups IV and V (P > .6). The analysis also indicated that immunosuppression was not a bone loss-determining factor. Conclusion. Laser and PDT therapies were effective as an adjunctive treatment to SRP in reducing bone loss caused by experimental periodontitis induced in animals being treated systemically with tacrolimus.

Efficacy of a bioactive glass-ceramic (Biosilicate (R)) 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 (R)) and a bioactive glass (Biogran (R)) 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 (R), Biogran (R) 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 (R) or Biogran (R) particles preserved alveolar ridge height without affecting its width. No significant differences in terms of BIC, BAMA, and BABT values were detected among Biosilicate (R), Biogran (R), and the non-implanted group. Conclusions The results of the present study indicate that filling of sockets with either Biosilicate (R) or Biogran (R) particles preserves alveolar bone ridge height and allows osseointegration of Ti implants. To cite this article:Roriz VM, Rosa AL, Peitl O, Zanotto ED, Panzeri H, de Oliveira PT. Efficacy of a bioactive glass-ceramic (Biosilicate (R)) in the maintenance of alveolar ridges and in osseointegration of titanium implants.Clin. Oral Impl. Res. 21, 2010; 148-155.doi: 10.1111/j.1600-0501.2009.01812.x.

Collagen membranes at immediate implants: a histomorphometric study in dogs

Aim To evaluate the influence of resorbable membranes on hard tissue alterations and osseointegration at implants placed into extraction sockets in a dog model. Material and methods In the mandibular premolar region, implants were installed immediately into the extraction sockets of six Labrador dogs. Collagen-resorbable membranes were placed at the test sites, while the control sites were left uncovered. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed, and ground sections were obtained for histomorphometric evaluation. Results After 4 months of healing, a control implant was not integrated (n=5). Both at the test and at the control sites, bone resorption occurred. While the most coronal bone-to-implant contact was similar between the test and the control sites, the alveolar bone crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 1.7 mm) compared with the control sites (loss: 2.2 mm). Conclusions The use of collagen-resorbable membranes at implants immediately placed into extraction sockets contributed to a partial (23%) preservation of the buccal outline of the alveolar process. To cite this article:Caneva M, Botticelli D, Salata LA, Souza SLS, Carvalho Cardoso L, Lang NP. Collagen membranes at immediate implants: a histomorphometric study in dogs.Clin. Oral Impl. Res. 21, 2010; 891-897.doi: 10.1111/j.1600-0501.2010.01946.x.

Histological evaluation of chitosan-based biomaterials used for the correction of critical size defects in rat`s calvaria

Chitosan, a biopolymer obtained from chitin, and its derivates, such as chitosan hydrochloride, has been reported as wound healing accelerators and as possible bone substitutes for tissue engineering, and therefore these Substances could be relevant in dentistry and periodontology. The purpose of this investigation was to make a histological evaluation of chitosan and chitosan hydrochloride biomaterials (gels) used in the correction of critical size bone defects made in rat`s calvaria. Bone defects of 8 mm in diameter were surgically created in the calviria of 50 Holtzman (Rattus norvegicus) rats and filled with blood clot (control), low molecular weight chitosan, high molecular weight chitosan, low molecular weight chitosan hydrochloride, and high molecular weight chitosan hydrochloride, numbering 10 animals, divided into two experimental periods (15 and 60 days), for each biomaterial. The histological evaluation was made based on the morphology of the new-formed tissues in defect`s region, and the results indicated that there was no statistical difference between the groups when the new bone formation in the entire defect`s area were compared (p > 0.05) and, except in the control groups, assorted degrees of inflammation Could be Seen. In Conclusion, chitosan and chitosan hydrochloride biomaterials used in this study were not able to promote new bone formation in critical size defects made in rat`s calvaria. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res 93A: 107-114, 2016

Análise citogenética de células-tronco derivadas do subendotélio da veia umbilical humana

Mesenchymal stem cells (MSCs) are known as a population of multi-potential cells able to proliferate and differentiate into multiple mesodermal tissues including bone, cartilage, muscle, ligament, tendon, fat and stroma. Several applications of the study of EC can be emphasized the therapeutic techniques such as guided bone regeneration by implantation of EC in the affected site, without the need for bone grafts, using titanium as a vehicle. The process of cryopreservation is essential for the maintenance of cell cultures, since the cell line is frozen, it can be maintained in liquid nitrogen for an indefinite period and then thawed for therapeutic or experimental purposes. The aim of this study was to isolate a population of MSCs derived from the subendothelium of the umbilical vein human (MSCs-SUVH) to assess cytogenetic analysis by the possibility of appearance of chromosomal changes in two different situations: MSCs-SUVH regarding the process of cryopreservation and MSCs-SUVH grown on the surface of titanium. Flow cytometry analysis revealed that, this cell population was positive for the markers CD29, CD73 and CD90, but there was no expression of hematopoietic lineage markers, such as CD14, CD34 and CD45 and demonstrated capacity for osteogenic differentiation. The chromosomes obtained from the primary culture of MSCs-SUVH were analyzed by GTW banding technique, and results are described as guidelines to ISCN 2005. There was not the emergence of clonal chromosomal changes in the MSCs-SUVH in different situations analyzed. However one of the strings presented a balanced paracentric inversion, probably a cytogenetic constitutional alterations, which was present before and after the experimental situations that the MSCs-SUVH was submitted

Autogenous demineralized dentin matrix for tissue engineering applications: Radiographic and histomorphometric studies

Purpose: This work evaluated the osteoconductive properties of autogenous demineralized dentin matrix (ADDM) on surgical bone defects in the parietal bone of rabbits, using the guided bone regeneration technique and polytetrafluoroethylene (PTFE) membrane. Materials and Methods: Surgical bone defects were created in 24 adult rabbits and repaired with either ADDM and PTFE (experimental group) or PTFE alone (control group). The ADDM had been obtained from the central incisors of the experimental rabbits. The rabbits were sacrificed after 15, 30, 60, and 90 days and the defects examined radiographically and histologically. Results: Radiographically, the defects in the experimental animals achieved radiopacity more quickly than the defects in the control group. Discussion: After 15, 30, 60, and 90 days of observation following surgery, the ADDM slices appeared to stimulate new bone formation. The dentin slices were completely incorporated into the new bone tissue and were resorbed during the bone repair. Conclusions: Bone repair was accelerated on the bone defects treated with ADDM when compared to the control group.

Densitometric analysis of the autogenous demineralized dentin matrix on the dental socket wound healing process in humans

The aim of this study was to evaluate the effects of the autogenous demineralized dentin matrix (ADDM) on the third molar socket wound healing process in humans, using the guided bone regeneration technique and a polytetrafluoroethylene barrier (PTFE). Twenty-seven dental sockets were divided into three groups: dental socket (Control), dental socket with PTFE barrier (PTFE), and dental socket with ADDM slices associated to PTFE banier (ADDM + PTFE). The dental sockets were submitted to radiographic bone densitometry analysis and statistical analysis on the 15th, 30th, 60th and 90th days using analysis of variance (ANOVA) and Tukey's test (p ≤ 0.05). The radiographic analysis of the ADDM + PTFE group showed greater homogeneity of bone radiopacity than the Control group and the PTFE group, during all the observation times. The dentin matrix gradually disappeared from the dental socket during the course of the repair process, suggesting its resorption during the bone remodeling process. It was concluded that the radiographic bone density of the dental sockets treated with ADDM was similar to that of the surrounding normal bone on the 90th day. The ADDM was biocompatible with the bone tissue of the surgical wounds of human dental sockets. The radiographic analysis revealed that the repair process was discreetly faster in the ADDM + PTFE group than in the Control and PTFE groups, although the difference was not statistically significant. In addition, the radiographic image of the ADDM + PTFE group suggested that its bone architecture was better than that of the Control and PFTE groups.