Maxillary sinus lift response to platelet-rich plasma associated with autogenous bone, ceramic biphasic HA/ß-TCP (70:30), or deproteinized bovine bone.

BACKGROUND: This study evaluated the long-term effects of platelet-rich plasma (PRP) on bone formation and regeneration when associated with autogenous bone graft (AB), porous biphasic calcium phosphate (pBCP), or deproteinized bovine bone (DBB) in maxillary sinus augmentation (MSA) of rabbit. METHODS: In 54 rabbits, bilateral MSA procedure was performed and randomly one sinus was filled with 200 mm3 material plus blood clot (AB/clot, DBB/clot, and pBCP/clot) and other with the same graft plus PRP (AB/PRP, DBB/PRP, and pBCP/PRP). After 30, 60, and 180 days, microtomographic were performed to analyze the three-dimensional MSA volume and histomorphometric analyses for the percentage of bone and soft tissues ingrowth. Data were compared by two-way ANOVA and the means were compared by the Tukey test, at p < 0.05. RESULTS: The percentage of pBCP and DBB were nearly unchanged throughout the whole period and bone formation occurred in the spaces between particles. The MSA volume filled with DBB and pBCP agglutinated with clot and PRP maintained constant during all experimental periods (147.2 mm3 and 154.9 mm3, respectively, p = 0.7377), and no significant changes in the new formatted bone and soft tissue were observed between treatments. In AB/clot and AB/PRP, the MSA volume was similar at 30 days (140.3 mm3 and 137.9 mm3, respectively), but a higher and gradual reduction was observed until 180 days. In the AB/PRP, this reduction was significantly higher (44.2%) than AB/clot (22.5%) (p = 0.01792). Histologically, the addition of PRP to AB accelerated the new bone formation/remodeling maintaining the percentage of new bone similar to AB/clot during all experimental volume (p = 0.6406), while the AB particles showed a higher resorption in AB/PRP than AB/clot until 60 days (mean of 7.8% and 15.1%, respectively, p = 0.0396). CONCLUSION: The association of PRP with the autogenous graft accelerates the process of bone formation/remodeling in MSA, but not had influence on the pBCP and DBB groups.

Concentration-dependent effects of latex F1-protein fraction incorporated into deproteinized bovine bone and biphasic calcium phosphate on the repair of critical-size bone defects.

F1-protein fraction (F1) is a natural bioactive compound extracted from the rubber tree, Hevea brasiliensis, and has been recently studied for its therapeutic potential in wound healing. In this study, we investigated the concentration-dependent effects of F1 (0.01%, 0.025%, 0.05%, and 0.1%) incorporated into deproteinized bovine bone (DBB) and porous biphasic calcium phosphate (pBCP), on the repair of rat calvarial critical-size bone defects (CSBD). The defects were analyzed by 3D-microtomography and 2D-histomorphometry at 12 weeks postsurgery. The binding efficiency of F1 to pBCP (96.3 ± 1.4%) was higher than that to DBB (67.7 ± 3.3%). In vivo analysis showed a higher bone volume (BV) gain in all defects treated with DBB (except in 0.1% of F1) and pBCP (except in 0.05% and 0.1% of F1) compared to the CSBD without treatment/control group (9.96 ± 2.8 mm3 ). DBB plus 0.025% F1 promoted the highest BV gain (29.7 ± 2.2 mm3 , p < .0001) compared to DBB without F1 and DBB plus 0.01% and 0.1% of F1. In the pBCP group, incorporation of F1 did not promote bone gain when compared to pBCP without F1 (15.9 ± 4.2 mm3 , p > .05). Additionally, a small BV occurred in defects treated with pBCP plus 0.1% F1 (10.4 ± 1.4 mm3, p < .05). In conclusion, F1 showed a higher bone formation potential in combination with DBB than with pBCP, in a concentration-dependent manner. Incorporation of 0.25% F1 into DBB showed the best results with respect to bone formation/repair in CSBD. These results suggest that DBB plus 0.25% F1 can be used as a promising bioactive material for application in bone tissue engineering.

In vitro and in vivo assessment of CaP materials for bone regenerative therapy. The role of multinucleated giant cells/osteoclasts in bone regeneration.

In this work, bone formation/remodeling/maturation was correlated with the presence of multinucleated giant cells (MGCs)/osteoclasts (tartrate-resistant acid phosphatase [TRAP]-positive cells) on the surface of beta-tricalcium phosphate (ß-TCP), sintered deproteinized bovine bone (sDBB), and carbonated deproteinized bovine bone (cDBB) using a maxillary sinus augmentation (MSA) in a New Zealand rabbit model. Microtomographic, histomorphometric, and immunolabeling for TRAP-cells analyses were made at 15, 30, and 60 days after surgery. In all treatments, a faster bone formation/remodeling/maturation and TRAP-positive cells activity occurred in the osteotomy region of the MSA than in the middle and submucosa regions. In the ß-TCP, the granules were rapidly reabsorbed by TRAP-positive cells and replaced by bone tissue. ß-TCP enabled quick bone regeneration/remodeling and full bone and marrow restoration until 60 days, but with a significant reduction in MSA volume. In cDBB and sDBB, the quantity of TRAP-positive cells was smaller than in ß-TCP, and these cells were associated with granule surface preparation for osteoblast-mediated bone formation. After 30 days, more than 80% of granule surfaces were surrounded and integrated by bone tissue without signs of degradation, preserving the MSA volume. Overall, the materials tested in a standardized preclinical model led to different bone formation/remodeling/maturation within the same repair process influenced by different microenvironments and MGCs/osteoclasts. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:282-297, 2020.

HGMB1 and RAGE as Essential Components of Ti Osseointegration Process in Mice.

The release of the prototypic DAMP High Mobility Group Box 1 (HMGB1) into extracellular environment and its binding to the Receptor for Advanced Glycation End Products (RAGE) has been described to trigger sterile inflammation and regulate healing outcome. However, their role on host response to Ti-based biomaterials and in the subsequent osseointegration remains unexplored. In this study, HMGB1 and RAGE inhibition in the Ti-mediated osseointegration were investigated in C57Bl/6 mice. C57Bl/6 mice received a Ti-device implantation (Ti-screw in the edentulous alveolar crest and a Ti-disc in the subcutaneous tissue) and were evaluated by microscopic (microCT [bone] and histology [bone and subcutaneous]) and molecular methods (ELISA, PCR array) during 3, 7, 14, and 21 days. Mice were divided into 4 groups: Control (no treatment); GZA (IP injection of Glycyrrhizic Acid for HMGB1 inhibition, 4 mg/Kg/day); RAP (IP injection of RAGE Antagonistic Peptide, 4 mg/Kg/day), and vehicle controls (1.5% DMSO solution for GZA and 0.9% saline solution for RAP); treatments were given at all experimental time points, starting 1 day before surgeries. HMGB1 was detected in the Ti-implantation sites, adsorbed to the screws/discs. In Control and vehicle groups, osseointegration was characterized by a slight inflammatory response at early time points, followed by a gradual bone apposition and matrix maturation at late time points. The inhibition of HMGB1 or RAGE impaired the osseointegration, affecting the dynamics of mineralized and organic bone matrix, and resulting in a foreign body reaction, with persistence of macrophages, necrotic bone, and foreign body giant cells until later time points. While Control samples were characterized by a balance between M1 and M2-type response in bone and subcutaneous sites of implantation, and also MSC markers, the inhibition of HMGB1 or RAGE caused a higher expression M1 markers and pro-inflammatory cytokines, as well chemokines and receptors for macrophage migration until later time points. In conclusion, HMGB1 and RAGE have a marked role in the osseointegration, evidenced by their influence on host inflammatory immune response, which includes macrophages migration and M1/M2 response, MSC markers expression, which collectively modulate bone matrix deposition and osseointegration outcome.

Metformin as an add-on to insulin improves periodontal response during orthodontic tooth movement in type 1 diabetic rats.

BACKGROUND: Type 1 diabetes (T1D) is associated with delayed tissue healing and bone loss. Periodontal tissues during tooth movement (OTM) in T1D and under diabetic treatment are poorly understood. We aimed to study the effect of metformin as an add-on to insulin therapy on periodontal structures during OTM in T1D rats. METHODS: Rats were divided into normoglycemic (NG, n = 20) and streptozotocin-induced diabetic groups that were untreated (T1D, n = 20), treated with insulin (I-T1D, n = 20), or treated with insulin plus metformin (IM-T1D, n = 20). After 7 days of treatment, the first right upper molar (M1) was moved mesially. At days 0, 3, 7 and 14, the pattern of OTM and the periodontal tissues were analyzed by micro-CT, histomorphometry, and immunohistochemistry for TRAP. RESULTS: In T1D, major osteoclastogenic activity and bone loss versus other groups were confirmed by a greater TRAP-positive cell number and reabsorption surface on both the pressure and tension sides for 14 days (p < 0.01). Additionally, we observed low bone volume density. Metformin plus insulin resulted in a daily insulin dose reduction and major glycemic control versus I-T1D. Although no significant differences were observed between I-T1D and IM-T1D, the tooth displacement and inclination, periodontal ligament thickness, and alveolar bone density on the pressure side in IM-T1D were similar to that of NG (p > 0.05). CONCLUSION: Antidiabetic treatment reduces severe periodontal damage during applied orthodontic force in T1D untreated rats. Metformin as an add-on to insulin therapy resulted in glycemic control and a periodontal tissue response to orthodontic forces that was similar to that of normoglycemic rats.

Green tea prevents vascular disturbs and attenuates periodontal breakdown in long-term hyperglycaemia in T1D rats.

AIM: The effects of green tea on the modulation of vascularization during the progression of spontaneous periodontitis in long-term hyperglycaemia in streptozotocin-induced type 1 diabetic (T1D) rats were evaluated. MATERIALS AND METHODS: Wistar rats normoglycaemic (NG) and T1D were divided into two control groups, which received water (NG-W and T1D-W) and two experimental groups that received green tea (NG-GT and T1D-GT). Periodontal structures were evaluated by microtomographic and histological analyses. Number of immunostained cells for VEGF (NcVEGF+/mm2 ) and CD31 (NcCD31+/mm2 ), as well microvessel density (MVD) in the periodontal ligament (PDL) were evaluated. RESULTS: Long-term hyperglycaemia in T1D-W rats induced vascular alterations in PDL with a reduction of 36% in MVD, a decrease of 33% in NcCD31+/mm2 and an increase of 53% in NcVEGF+/mm2 . Concomitantly, a severe degree of periodontitis with higher reduction in bone volume and periodontal bone level was observed. In T1D-GT, green tea maintained the MVD, NcCD31+/mm2 and NcVEGF+/mm2 in the PDL similar to normoglycaemic groups. Clinically, in T1D-GT rats, green tea reduced dental plaque accumulation and the degree of periodontitis when compared to T1D-W. CONCLUSION: Daily green tea consumption has a therapeutic effect on the diabetic vascular disorder in PDL and the progression of periodontitis in long-term hyperglycaemia in T1D rats.

Osteoinductive porous biphasic calcium phosphate ceramic as an alternative to autogenous bone grafting in the treatment of mandibular bone critical-size defects.

The bone-induction capacity of a porous biphasic calcium phosphate (pBCP) using heterotopic implantation in mouse (mHI-model) and its efficacy as substitute for autograft in mandibular critical-size defect in rabbit (rabMCSD-model) was investigated. In mHI-model, pBCP was implanted into the thigh muscles and bone formation was histomorphometrically and immunohistochemically evaluated. In rabMCSD-model, 13 mm bone defects were treated with pBCP or autograft and bone repair comparatively evaluated by radiographic and histomorphometric methods. In mHI-model, formed bone and immunolabeling for bone morphogenetic protein-2 and osteopontin were observed in 90% of pBCP implanted samples after 12 weeks. In rabMCSD-model neither statistically significant difference was found in newly formed bone between pBCP and autograft groups at 4 weeks (18.8 ± 5.5% vs 27.1 ± 5.6%), 8 weeks (22.3 ± 2.7% vs 26.2 ± 5.1), and 12 weeks (19.6 ± 4.7% vs 19.6 ± 2.3%). At 12 weeks, the stability and contour of the mandible were restored in both treatments. Near tooth remaining, pBCP particles were covered by small amount of mineralized tissue exhibiting perpendicular attachments of collagen fiber bundles with histological characteristic of acellular cementum. Within the limitations of this study, it was concluded that pBCP is osteoinductive and able to stimulate the new formation of bone and cementum-like tissues in rabMCSD-model, suggesting that it may be an alternative to treatment of large bone defect and in periodontal regenerative therapy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1546-1557, 2018.

Bacteria arise at the border of mycoplasma-infected HeLa cells, containing cytoplasm with either malformed cytosol, mitochondria and endoplasmic reticulum or tightly adjoined smooth vacuoles.

A study with transmission electron microscopy of mycoplasma-contaminated HeLa cells using five cell donors referred to as donors A, B, C, D and E, observations are herein presented. Experiments performed with cells from donors B, C and D, revealed the presence of Mycoplasma hyorhinis after PCR and sequencing experiments. Bacteria probably originated from a cytoplasm with compacted tiny granular particles replacing the normal cytosol territories, or from the contact with the cytoplasm through a clear semi-solid material. The compact granularity (CG) of the cytoplasm was crossed by stripes of smooth and rough endoplasmic reticulum cisternae. Among apparently normal mitochondria, it was noted, in variable proportions, mitochondria with crista-delimited lucent central regions that expand to and occupied the interior of a crista-less organelle, which can undergo fission. Other components of the scenarios of mycoplasma-induced cell demolition are villus-like structures with associated 80-200 nm vesicles and a clear, flexible semi-solid, process-sensitive substance that we named jam-like material. This material coated the cytoplasmic surface, its recesses, irregular protrusions and detached cytoplasmic fragments. It also cushioned forming bacteria. Cyst-like structures were often present in the cytoplasm. Cells, mainly apoptotic, exhibiting ample cytoplasmic sectors with characteristic net-like profile due to adjoined vacuoles, as well as ovoid or elongated profiles, consistently appeared in all cells from the last four cell donors. These cells were named "modified host cells" because bacteria arose in the vacuoles. The possibility that, in some samples, there was infection and/or coinfection of the host cell by another organism(s) cannot be ruled out.

Impact of Inorganic Xenograft on Bone Healing and Osseointegration: An Experimental Study in Rabbits.

PURPOSE: To evaluate if an inorganic graft applied before implant insertion interferes with osseointegration. MATERIALS AND METHODS: The bilateral mandibular incisors of 12 rabbits were extracted. One of the sockets was randomly filled with an inorganic xenogenic bone graft, whereas the remaining socket was allowed to heal naturally and served as a control. After 60 days, titanium implants were inserted into healing areas. The animals were killed 60 days after. Bone depositions were marked with fluorochrome oxytetracycline, alizarin, and calcein and evaluated using confocal laser scanning microscopy. Bone-to-implant contact (BIC) and bone area (BA) within the limits of the implant threads were analyzed. Data were compared statically by paired t tests, one-way ANOVA, and Bonferroni post hoc tests (α = 0.05). RESULTS: No differences between the control and experimental groups in bone deposition for each marker, in either the BIC or BA analysis were observed. The bone deposition marked by alizarin (14-21 days) was the highest, followed by oxytetracycline (0 and 7 days) and calcein (45 and 52 days) in both groups (P < 0.05). CONCLUSION: The bone healing or the course of osseointegration was not impaired by the use of an inorganic xenogenic graft before insertion of a titanium implant.

Intramembranous bone healing process subsequent to tooth extraction in mice: micro-computed tomography, histomorphometric and molecular characterization.

Bone tissue has a significant potential for healing, which involves a significant the interplay between bone and immune cells. While fracture healing represents a useful model to investigate endochondral bone healing, intramembranous bone healing models are yet to be developed and characterized. In this study, a micro-computed tomography, histomorphometric and molecular (RealTimePCRarray) characterization of post tooth-extraction alveolar bone healing was performed on C57Bl/6 WT mice. After the initial clot dominance (0 h), the development of a provisional immature granulation tissue is evident (7 d), characterized by marked cell proliferation, angiogenesis and inflammatory cells infiltration; associated with peaks of growth factors (BMP-2-4-7,TGFß1,VEGFa), cytokines (TNFα, IL-10), chemokines & receptors (CXCL12, CCL25, CCR5, CXCR4), matrix (Col1a1-2, ITGA4, VTN, MMP1a) and MSCs (CD105, CD106, OCT4, NANOG, CD34, CD146) markers expression. Granulation tissue is sequentially replaced by more mature connective tissue (14 d), characterized by inflammatory infiltrate reduction along the increased bone formation, marked expression of matrix remodeling enzymes (MMP-2-9), bone formation/maturation (RUNX2, ALP, DMP1, PHEX, SOST) markers, and chemokines & receptors associated with healing (CCL2, CCL17, CCR2). No evidences of cartilage cells or tissue were observed, strengthening the intramembranous nature of bone healing. Bone microarchitecture analysis supports the evolving healing, with total tissue and bone volumes as trabecular number and thickness showing a progressive increase over time. The extraction socket healing process is considered complete (21 d) when the dental socket is filled by trabeculae bone with well-defined medullary canals; it being the expression of mature bone markers prevalent at this period. Our data confirms the intramembranous bone healing nature of the model used, revealing parallels between the gene expression profile and the histomorphometric events and the potential participation of MCSs and immune cells in the healing process, supporting the forthcoming application of the model for the better understanding of the bone healing process.

Meloxicam temporally inhibits the expression of vascular endothelial growth factor receptor (VEGFR)-1 and VEGFR-2 during alveolar bone repair in rats.

BACKGROUND: Vascular endothelial growth factor (VEGF) plays an important role during angiogenesis and bone repair. This study investigated whether the use of meloxicam alters bone repair via downregulation of VEGF and receptor expression. METHODS: One hundred twenty male Wistar rats had their maxillary right incisor extracted. Animals were divided into a control group (CG; n = 60) and a meloxicam-treated group (TG; n = 60) that received either a single daily intraperitoneal injection of 0.9% NaCl or meloxicam 3 mg/kg, respectively, for 7 consecutive days. Alveolar bone repair was evaluated histomorphometrically, whereas VEGF and its receptors were analyzed by immunohistochemistry and quantitative polymerase chain reaction (qPCR). Data were submitted to two-way analysis of variance and Tukey post hoc test with P < 0.05. RESULTS: Bone volume density increased significantly (P = 0.001) in both groups with a strong correlation between treatment and periods (P = 0.003). In the TG, a small amount of bone formation occurred compared with the CG between 3 and 21 days. No significant differences in the number of VEGF-positive cells per square millimeter (P = 0.07) and VEGF messenger RNA (mRNA) expression (P = 0.49) were found between groups. Immunostained cells per square millimeter and mRNA expression for VEGF receptor (VEGFR)-1 (P = 0.04 and P < 0.001) and VEGFR-2 (P < 0.001 for both analysis) showed a strong interaction between treatment groups and periods. In the TG, immunostained cells per square millimeter and mRNA expression for VEGFR-1 were, respectively, 89% and 37% lower from 3 to 10 days compared with the CG, whereas for VEGFR-2, these values were 252% and 60%, respectively, from 3 to 7 days. CONCLUSION: In rat alveolar bone repair, meloxicam did not affect VEGF expression but downregulated VEGFR expression, which may cause a delay in the bone repair/remodeling process.

Long-term dexamethasone treatment alters the histomorphology of acinar cells in rat parotid and submandibular glands.

Glucocorticoids (GCs) induce insulin resistance (IR), a condition known to alter oral homeostasis. This study investigated the effects of long-term dexamethasone administration on morphofunctional aspects of salivary glands. Male Wistar rats received daily injections of dexamethasone [0.1 mg/kg body weight (b.w.), intraperitoneally] for 10 days (DEX), whereas control rats received saline. Subsequently, glycaemia, insulinaemia, insulin secretion and salivary flow were analysed. The parotid and submandibular glands were collected for histomorphometric evaluation and Western blot experiments. The DEX rats were found to be normoglycaemic, hyperinsulinaemic, insulin resistant and glucose intolerant (P < 0.05). DEX rat islets secreted more insulin in response to glucose (P < 0.05). DEX rats had significant reductions in the masses of the parotid (29%) and submandibular (16%) glands (P < 0.05) that was associated with reduced salivary flux rate. The hypotrophy in both glands observed in the DEX group was associated with marked reduction in the volume of the acinar cells in these glands of 50% and 26% respectively (P < 0.05). The total number of acinar cells was increased in the submandibular glands of the DEX rats (P < 0.05) but not in the parotid glands. The levels of proteins related to insulin and survival signalling in both glands did not differ between the groups. In conclusion, the long-term administration of dexamethasone caused IR, which was associated with significant reductions in both mass and flux rate of the salivary glands. The parotid and submandibular glands exhibited reduced acinar cell volume; however, the submandibular glands displayed acinar hyperplasia, indicating a gland-specific response to GCs. Our data emphasize that GC-based therapies and insulin-resistant states have a negative impact on salivary gland homeostasis.

Sintered anorganic bone graft increases autocrine expression of VEGF, MMP-2 and MMP-9 during repair of critical-size bone defects.

This study aimed to evaluate morphometrically the bone formation and immunohistochemically the expression of vascular endothelial growth factor (VEGF) and metalloproteinase (MMP)-2 and -9 during the healing of critical-size defects treated with sintered anorganic bone (sAB). The 8-mm diameter full-thickness trephine defects created in the parietal bones of rats were filled with sAB (test group) or blood clot (CSD-control group). At 7, 14, 21, 30, 90 and 180 days postoperatively (n = 6/period) the volume of newly formed bone and total number of immunolabeled cells (Ntm) for each protein were determined. Bone formation was smaller and faster in the CSD-control group, stabilizing at 21 days (6.74 mm(3)). The peaks of VEGF, MMP-2 and MMP-9 occurred at 7 and 14 days in fibroblasts and osteoblasts, with mean reduction of 0.80 time at 21 days, keeping constant until 180 days. In the test group, sAB provided continuous bone formation between particles throughout all periods. The peak of MMP-2 was observed at 7-14 days in connective tissue cells and for VEGF and MMP-9 at 30 days in osteoblasts and osteocytes. Ntm for VEGF, MMP-2 and MMP-9 were in average, respectively, 3.70, 2.03 and 5.98 times higher than in the control group. At 180 days, newly formed bone (22.9 mm(3)) was 3.74 times greater in relation to control. The physical and chemical properties of sAB allow increased autocrine expression of VEGF, MMP-2 and MMP-9, favoring bone formation/remodeling with very good healing of cranial defects when compared to natural repair in the CSD-control.

Effects of fluoride in bone repair: an evaluation of RANKL, OPG and TRAP expression.

The objective of this study was to evaluate comparatively the effect of fluoride in the expression of the receptor activator of nuclear factor kappa B ligand (RANKL), osteoprotegerin (OPG) and tartrate-resistant acid phosphatase (TRAP) in alveolar bone repair in rats. We used 3 groups of male Wistar rats (n = 5/group), which received drinking water containing different doses of F (NaF): 0, 5 and 50 ppm, for 60 days before the incisors extraction. The upper incisors were extracted and the animals were killed 7, 14, 21 and 30 days after extraction. The hemi-maxillae were collected for microscopic examination (histomorphometric and immunostaining for RANKL, OPG and TRAP). Histomorphometric analysis confirmed an increase in the volume density of neoformed bone between 7 and 30 days for groups control, 5 and 50 ppm of F, with a concomitant decrease in the volume density of connective tissue and blood clot. Higher blood clot for groups 5 and 50 ppm of F at 30 days was observed. The RANKL and OPG expressions were not changed by chronic exposure to fluoride in the drinking water during the studied periods; on the other hand, TRAP expression was changed (at 7 days) by chronic exposure to fluoride (p < 0.05). It was concluded that F in high concentrations can slow the blood clot remission and bone repair, and alter the TRAP expression in the beginning of the bone tissue repair. However, a better understanding about this blood clot remission phenomenon is required.

The impact of healing time before loading on orthodontic mini-implant stability: a histomorphometric study in minipigs.

OBJECTIVE: To evaluate healing time before loading, areas compression and tension and location of insertion on mini-implant stability. DESIGN: Six minipigs were used. Each animal received 3 mini-implants in each quadrant: 1 mini-implant was used as an unloaded control (G1, n=24); the other 2 were loaded with 150g-force at three time intervals (G2: immediate loading, G3: after 15 days and G4: after 30 days), with 16 mini-implant in each experimental group. After 120 days, tissue blocks of the areas of interest were harvested. Clinical analysis (exact Fisher test) determined the survival rate. Histological analysis (Kontron KS 300™, Zeiss) quantified the fractional bone-to-implant contact (%BIC) and bone area (%BA) at each healing time point, areas of interest, and insertion site (ANOVA and t tests for dependent and independent samples). RESULTS: The mini-implant survival rates were G1: 71%, G2: 50%, G3: 75% and G4: 63%, with no statistical differences between them. The groups presented similar %BIC and %BA. There were no differences between the compression and tension sides or maxillary and mandibular insertion sites. CONCLUSIONS: These results suggest that low-intensity immediate or early orthodontic loading does not affect mini-implant stability, because similar histomorphometric results were observed for all the groups, with partial osseointegration of the mini-implants present.

Biological monitoring of a promissory xenogenic pin for biomedical applications: a preliminary intraosseous study in rats.

OBJECTIVES: Over the last years, it is known that in some cases metal devices for biomedical applications present some disadvantages suggesting absorbable materials (natural or synthetic) as an alternative of choice. Here, our goal was to evaluate the biological response of a xenogenic pin, derived from bovine cortical bone, intraosseously implanted in the femur of rats. MATERIAL AND METHODS: After 10, 14, 30 and 60 days from implantation, the animals (n=5/period) were killed and the femurs carefully collected and dissected out under histological demands. For identifying the osteoclastogenesis level at 60 days, we performed the immunohistochemisty approach using antibody against RANKL. RESULTS: Interestingly, our results showed that the incidence of neutrophils and leukocytes was observed only at the beginning (10 days). Clear evidences of pin degradation by host cells started at 14 days and it was more intensive at 60 days, when we detected the majority of the presence of giant multinucleated cells, which were very similar to osteoclast cells contacting the implanted pin. To check osteoclastogenesis at 60 days, we evaluated RANKL expression and it was positive for those resident multinucleated cells while a new bone deposition was verified surrounding the pins in all evaluated periods. CONCLUSIONS: Altogether, our results showed that pins from fully processed bovine bone are biocompatible and absorbable, allowing bone neoformation and it is a promissory device for biomedical applications.

Long-term rabbits bone response to titanium implants in the presence of inorganic bovine-derived graft.

This study evaluated bone responses to titanium implants in the presence of an inorganic graft material. The bilateral mandible incisors of 24 rabbits were surgically extracted and one of the exposed sockets, chosen at random, was filled with an inorganic xenogenic bone graft (Gen-ox®), whereas the remaining socket was left to heal naturally and served as a control. After 60 days, titanium implants were inserted in the specific areas, and on days 0, 30, 60, and 180 after the implant insertions, six animals of each group were killed. Digital periapical radiography of implant region was obtained and vertical bone height (VBH) and bone density (BD) were evaluated by digital analysis system. In the undecalcified tissue cuts, bone-to-implant contact (BIC) and bone area (BA) within the limits of the implant threads were evaluated and compared statistically by means of two-way ANOVA and Tukey's test (ρ < 0.05). No significant differences were detected in VBH and BA, either between groups or between different experimental intervals. The BD was significantly higher in the experimental group than in the control group in all the intervals tested, but there were no significant differences by interval. The BIC was statistically lower in the control group on day 0; however, a significant increase was observed on days 60 and 180 (ρ < 0.05). The use of an inorganic xenograft prior to insertion of a titanium implant did not interfere with the course of osseointegration.

Repair of rabbit femur defects with organic bovine bone cancellous block or cortical granules.

PURPOSE: To investigate the osseous repair in epiphyseal rabbit femur defects treated with organic bovine bone (OBB) cancellous block or OBB cortical granules. MATERIALS AND METHODS: Forty-eight trephined defects were made bilaterally in 30 rabbits. In 18 animals, the defects were filled with OBB cancellous block (experimental group 1) or OBB cortical granules (experimental group 2), and in 12 animals (control group), the defects on both sides were filled only with blood clot. After 30, 90, and 180 days, the femur epiphyses were collected, fixed, radiographed both digitally and conventionally, and then processed for histologic analyses. The newly formed cortical bone was measured in the histologic sections using a digital image analysis system. RESULTS: Histologically, both experimental groups showed total or partial closure of the defects with woven bone at 30 days, whereas in the control sites, a marked migration of connective tissue into the defect was apparent. At 90 and 180 days, a similar pattern of repair was observed in the experimental groups and the control group. Quantitatively, however, no significant differences between groups (P > .05) were observed throughout the experimental period. A significant reduction in newly formed cortical bone occurred at 90 and 180 days (P < .05) in all groups. Radiographically, no statistically significant differences were seen among the groups (P > .05). CONCLUSIONS: The study showed minor descriptive differences at the first healing period that were not evident at later periods and that were not shown through histomorphometry and radiographic analysis. The only significant results were related to time.

Biological monitoring of a xenomaterial for grafting: an evaluation in critical-size calvarial defects.

Our purpose was to evaluate the osteoconduction potential of mixed bovine bone (MBB) xenografts as an alternative for bone grafting of critical-size defects in the calvaria of rats. After surgery, in the time intervals of 1, 3, 6, and 9 months, rats were killed and their skulls collected, radiographed and histologically prepared for analysis. The data obtained from histological analysis reported that the particles of MBB did not promote an intense immunological response, evidencing its biocompatibility in rats. Our results clearly showed the interesting evidence that MBB was not completely reabsorbed at 9 months while a small amount of newly formed bone was deposited by osteoprogenitor cells bordering the defect. However, this discrete bone-forming stimulation was unable to regenerate the bone defect. Overall, our results suggest that the properties of MBB are not suitable for stimulating intense bone regeneration in critical bone defects in rats.

Biomechanical and microscopic response of bone to titanium implants in the presence of inorganic grafts.

This study evaluated the biomechanical and microscopic response of previously grafted bone to titanium implants. The lower incisors of 16 rabbits were surgically extracted, and bilateral perforations communicating with the remaining sockets were created distally. A socket/perforation defect on each mandible was chosen at random to be immediately filled with a xenogenic graft, whereas the contralateral perforation was left to heal naturally and served as a paired control. After 60 days, titanium implants were installed in the previously operated areas. After periods of 2 and 6 months, the animals were killed, and the force necessary to retrieve implants as well as the bone-implant contact (BIC) and bone mass (BM) were quantified and statistically compared by 2-way analysis of variance and Tukey's test (α  =  .05). No significant differences in removal torque were observed, either by time or by treatment condition. Differences in BIC and BM between experimental and control groups were not statistically significant through the intervals studied (P < .05). The presence of a xenogenic graft did not influence the microscopic tissue response to titanium implants or fixation into newly formed or mature bone.