Igor Iuco Castro-Silva

Repair of critical-size defects with autogenous periosteum-derived cells combined with bovine anorganic apatite/collagen: an experimental study in rat calvaria

The aim of this study was to evaluate the bone repair using autogenous periosteum-derived cells (PDC) and bovine anorganic apatite and collagen (HA-COL). PDC from Wistar rats (n=10) were seeded on HA-COL discs and subjected to osteoinduction during 6 days. Critical-size defects in rat calvarias were treated with blood clot (G1), autogenous bone (G2), HA-COL (G3) and HA-COL combined with PDC (G4) (n=40), and then analyzed 1 and 3 months after surgeries. Radiographic analysis exhibited no significant temporal change. G1 and G2 had discrete new marginal bone, but the radiopacity of graft materials in G2, G3 and G4 impaired the detection of osteogenesis. At 3 months, histopathological analysis showed the presence of ossification islets in G1, which was more evident in G2, homogeneous new bone around HA-COL in G3 and heterogeneous new bone around HA-COL in G4 in addition to moderate presence of foreign body cells in G3 and G4. Histomorphometric analysis showed no change in the volume density of xenograft (p>0.05) and bone volume density in G2 was twice greater than in G1 and G4 after 3 months (p<0.05), but similar to G3. The PDC did not increase bone formation in vivo, although the biomaterial alone showed biocompatibility and osteoconduction capacity.

Immunohistochemical evaluation of MMP-2, MMP-9 and CD31/microvascular density in squamous cell carcinomas of the floor of the mouth

The aim of this study was to evaluate the immunoexpression of MMP-2, MMP-9 and CD31/microvascular density in squamous cell carcinomas of the floor of the mouth and to correlate the results with demographic, survival, clinical (TNM staging) and histopathological variables (tumor grade, perineural invasion, embolization and bone invasion). Data from medical records and diagnoses of 41 patients were reviewed. Histological sections were subjected to immunostaining using primary antibodies for human MMP-2, MMP-9 and CD31 and streptavidin-biotin-immunoperoxidase system. Histomorphometric analyses quantified positivity for MMPs (20 fields per slide, 100 points grade, ×200) and for CD31 (microvessels <50 µm in the area of the highest vascularization, 5 fields per slide, 100 points grade, ×400). Statistical design was composed by non-parametric Mann-Whitney U test (investigating the association between numerical variables and immunostainings), chi-square frequency test (in contingency tables), Fishers exact test (when at least one expected frequency was less than 5 in 2×2 tables), Kaplan-Meier method (estimated probabilities of overall survival) and Iogrank test (comparison of survival curves), all with a significance level of 5%. There was a statistically significant correlation between immunostaining for MMP-2 and lymph node metastasis. Factors associated negatively with survival were N stage, histopathological grade, perineural invasion and immunostaining for MMP-9. There was no significant association between immunoexpression of CD31 and the other variables. The intensity of immunostaining for MMP-2 can be indicative of metastasis in lymph nodes and for MMP-9 of a lower probability of survival.

Porcine peritoneum as source of biocompatible collagen in mice

PURPOSE: To investigate the biocompatibility and biodegradability of a membrane made from porcine peritoneum. METHODS: The membrane (5x5 mm) was inserted in the subcutaneous tissue on the back of 15 mice, which were killed after 1, 3 and 9 weeks (ISO 10993-6). The cellular components of the inflammatory response and degradation of the membrane were analyzed in hematoxylin-eosin-stained histological sections. RESULTS: After one week, mononuclear cells were observed inside the membrane. After three weeks, the material was almost completely absorbed. After nine weeks, there was no presence of material and there were signs of tissue remodeling. There was neither a foreign body reaction nor signs of tissue necrosis. CONCLUSION: The collagen membrane derived from porcine peritoneum is biocompatible and bioabsorbable when implanted in the subcutaneous tissue of mice.

Effectiveness and acceleration of bone repair in critical‐sized rat calvarial defects using low‐level laser therapy

Tissue regeneration remains a challenge for orthopedic and craniomaxillofacial surgery to treat bone loss. The use of low‐level laser therapy suggests a promise on this road with positive results for narrow defects. However, temporal and quantitative evaluations are required to understand the healing process of large injuries. The aim of this study was to investigate the repair of critical‐size bone defects in rat calvaria using a GaAlAs laser.

Biocompatibility of wollastonite‐poly(N‐butyl‐2‐cyanoacrylate) composites

Wollastonite-poly(n-butyl-2-cyanoacrylate) composite (W-BCA) has been proposed to immobilize anatomically bone fragments in order to achieve an optimal healing process. The present study evaluated the in vitro and in vivo behavior of three types of fillers: powdered natural wollastonite (Wn), synthetic pseudowollastonite powder (Ws), and synthetic pseudowollastonite powder coated with 5% acetyl tributyl citrate (Wst). The Wst-BCA composite underwent a higher degradability in the real-time degradation test and a superior cytotoxic effect; whereas the Wn-BCA composite showed a higher degradability in the accelerated test with no cytotoxicity. The formation of an extracellular collagenous matrix deposit on its surface and the most favorable new bone formation on Wn-BCA indicate its potential for bone adhesive use in unstable orthopedic traumas.

Comparative In Vivo Study of Biocompatibility of Apatites Incorporated with 1% Zinc or Lead Ions versus Stoichiometric Hydroxyapatite

Hydroxyapatite is the main ceramic material that has being used in bone repair, although its physico-chemical and in vivo behavior should be better understood. A method to improve the biocompatibility of HA is the substitution of calcium with divalent cations which enhance mechanic resistance and can modulate inflammatory response against implanted material. In this study we analyzed the biocompatibility of HA doped with one per cent of Zn2+ or Pb2+. The first one has being described as an inflammation modulator and the second would be a model for chronic toxicity assay. Biocompatibility of the both materials was studied in vivo following the ISO 10993-6 standard. HA cylinders (ZnHA, PbHA and stoichiometric HA as positive control) were implanted into subcutaneous tissue of 45 Balb-c mice and after 1, 3 and 9 weeks the animals were euthanized (5 for each experimental condition). Necropsies of the skin containing reactional tissue were removed, fixed in 10% formaldehyde and followed the histological processing for paraffin embedding and staining with Hematoxylin-Eosine and Picrosirius red. Microscopic analysis showed for all groups moderate inflammatory response, decreasing throughout the experimental periods, with ZnHA group showing more intense response. Similar presence of macrophages, fibrosis and angiogenesis were observed among the groups. Thereby, we can conclude that ZnHA and PbHA are biocompatible and not bioresorbable, being the ZnHA potentially indicated as bone graft. Detailed studies are required to better understand the role of PbHA as chronic model for lead toxicity.

Pérola de esmalte: epidemiologia, morfopatogênese e relevância na clínica odontológica

INTRODUCTION: Disturbances in odontogenesis generate dental anomalies with diagnostic and therapeutic relevance. OBJECTIVE: The aim of this article was to do the systemic review about pearl enamel, and discuss their formation process and its significance in clinical dentistry. MATERIAL AND METHOD: Three electronic databases (Pubmed, Cochrane and Biblioteca Virtual em Saude) were used to retrieve scientific articles in the last 30 years, using the descriptor enamel pearls. RESULT: Brazil occupies a prominent position in existing thematic publications (18%). Etiopathogenesis of this dental anomaly remains obscure, and more researches are needed regarding factors involved in ectopic amelogenesis and deficient cementogenesis in situ. Epidemiological data show variable frequency in the Brazilian population (0.8-8%) and in the global population (0,2-6,2%), with a higher incidence in the molars. Morphological analysis of enamel pearls shows that this shape and volume anomaly can be of two types: simple (external or internal true pearl) or compound (enamel-dentine or enamel-dentine-pulp). It is important the clinical and imaginological differential diagnosis of enamel pearls to allow adequate dental treatment that include enameloplasty as an effective conduct to minimize oral biofilm accumulation and worsening of periodontal disease. CONCLUSION: It is necessary to publish detailed researches about enamel pearls in order to generate scientific evidence in dental practice.

Osteoconduction and Bioresorption of Bone Allograft versus Anorganic Bovine Bone Xenograft: A Histomorphometric Study in Humans

This clinical study evaluated the tissue repair process using different bone grafts. Nine dental patients with indication for posterior implantodontic treatment were submitted to maxillary sinus lifting procedures associated to grafting. After 6 months, bone biopsies (6 sites with allogenous bone grafting and 13 sites with bovine xenogenous bone grafting/OsseusTM) were removed and processed for histopathological and histomorphometric analyses (ANOVA and Tukeys test). Both groups had tissue biocompatibility without significant inflammatory response, only punctual presence of multinucleated giant cells in xenograft group. Osteoconductive potential was evidenced by new bone tissue surrounding and in direct contact with the granules of both grafts. Volume density of connective tissue was similar between groups, although there were significant differences in allograft group in comparison to xenograft as the presence of new bone formation (48.50%±13.93 versus 29.83±9.56, respectively, p<0.05) and remnant biomaterial (1.57±2.39 versus 22.23±12.41, respectively, p<0.001), suggesting a greater osteoconductivity and faster bioresorption in the allograft group. These results demonstrate that allogenous bone and OsseusTM can be satisfactorily used as grafts in minor oral surgeries for bone augmentation in humans.

Hypernociception and wound healing after application of cyanoacrylate ester as a tissue adhesive in rats.

OBJECTIVE The present study assessed and compared postoperative hypernociception and skin healing after cyanoacrylate and classic suture as well as analyzed morphologic features of the tissue repair. STUDY DESIGN The intensity of hypernociception was measured with an electronic pressure-meter test. Rats were given an incised wound in the middle of the palms of the right and left paws. The left side was treated with a silk suture, and the right with cyanoacrylate. Control groups were treated locally with dipyrone or received a systemic pretreatment with valdecoxib. RESULTS Cyanoacrylate was associated with less inflammation (first week), and the healing wound site was rich in collagenous extracellular matrix and neovascularization. Dipyrone in combination with cyanoacrylate greatly increased the antinociceptive effect. These results were not repeated after systemic treatment with valdecoxib, suggesting that the antinociceptive effect seen in the tissue adhesive was due to formation of a physical barrier.

Preclinical evaluation of a xenogenic hydroxyapatite/ collagen-based bone substitute material

Objective: The aim of this study was to evaluate the physical, chemical and biological properties of a bovine xenograft for bone repair. Methods: Physicochemical analysis was performed using X-ray diffraction, Fourier transform infrared spectroscopy and scanning eletron microscopy. In vitro biocompatibility was evaluated through cytotoxicity and cell adhesion assays using a fibroblast cell line culture and murine pre-osteoblasts, respectively. Furthermore, an in vivo assay using a subcutaneous grafting on a rat model (5 and 10 weeks, synthetic hydroxyapatite as a control material) and yet a long term experiment in criticalsize calvarial defects (6 and 9 months, blood clot and autogenous bone as negative and positive controls, respectively). Results: The test material presented a three-dimensional architecture consisting of dense granules and micropores (various sizes), composed of crystalline hydroxyapatite/collagen fibers. The xenograft was cytocompatible and after 7 days pre-osteoblast spreading on material granules was observed. Histopathological analysis of the implanted material into rat subcutaneous showed the intact xenograft after 10 weeks surrounded by loose connective tissue with a mild inflammatory infiltrate and giant multinuclear cells around the particles (5 and 10 weeks) similar to the synthetic hydroxyapatite. Concerning the critical-size calvarial defects it was observed 1.7 times more new bone formation in the xenograft than the blood clot group (P<0.001), a similar result was verified on autograft. There was no significant variation in the volume density of the xenograft (37.9%±4.3). Conclusion: It was concluded that the xenogenic material is biomimetic, biocompatible, osteoconductive and non-resorbable, therefore being a promising material for bone repair.