Hydrophilic titanium surface modulates early stages of osseointegration in osteoporosis.

OBJECTIVE: Using a mouse osteoporotic model, this study aimed to determine the influence of hydrophilic titanium surfaces on gene expression and bone formation during the osseointegration process. BACKGROUND: Based on the previous evidence, it is plausible to assume that osteoporotic bone has a different potential of bone healing. Therefore, implant surface modification study that aims at enhancing bone formation to further improve short- and long-term clinical outcomes in osteoporosis is necessary. MATERIAL AND METHODS: Fifty female, 3-month-old mice were included in this study. Osteoporosis was induced by ovariectomy (OVX, test group) in 25 mice. The further 25 mice had ovaries exposed but not removed (SHAM, control group). Seven weeks following the ovariectomy procedures, one customized implant (0.7 × 8 mm) of each surface was placed in each femur for both groups. Implants had either a hydrophobic surface (SAE) or a hydrophilic treatment surface (SAE-HD). Calcium (Ca) and phosphorus (P) content was measured by energy-dispersive X-ray spectroscopy (EDS) after 7 days. The femurs were analyzed for bone-to-implant contact (BIC) and bone volume fraction (BV) by nano-computed tomography (nano-CT) after 14 and 28 days. Same specimens were further submitted to histological analysis. Additionally, after 3 and 7 days, implants were removed and cells were collected around the implant to access gene expression profile of key osteogenic (Runx2, Alp, Sp7, Bsp, Sost, Ocn) and inflammatory genes (IL-1ß, IL-10, Tnf-α, and Nos2) by qRT-PCR assay. Statistical analysis was performed by ANOVA and paired t test with significance at P < .05. RESULTS: The amount of Ca and P deposited on the surface due to the mineralization process was higher for SAE-HD compared to SAE on the intra-group analysis. Nano-CT and histology revealed more BV and BIC for SAE-HD in SHAM and OVX groups compared to SAE. Analysis in OVX group showed that most genes (ie, ALP, Runx2) involved in the bone morphogenetic protein (BMP) signaling were significantly activated in the hydrophilic treatment. CONCLUSION: Both surfaces were able to modulate bone responses toward osteoblast differentiation. SAE-HD presented a faster response in terms of bone formation and osteogenic gene expression compared to SAE. Hydrophilic surface in situations of osteoporosis seems to provide additional benefits in the early stages of osseointegration.

Influence of Titanium Alloy Scaffolds on Enzymatic Defense against Oxidative Stress and Bone Marrow Cell Differentiation.

Studies have been directed towards the production of new titanium alloys, aiming for the replacement of Ti-6 Aluminium-4 Vanadium (TiAlV) alloy in the future. Many mechanisms related to biocompatibility and chemical characteristics have been studied in the field of implantology, but enzymatic defenses against oxidative stress remain underexplored. Bone marrow stromal cells have been explored as source of cells, which have the potential to differentiate into osteoblasts and therefore could be used as cells-based therapy. The objective of this study was to evaluate the activity of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in porous scaffolds of Ti-6 Aluminium-4 Vanadium (TiAlV), Ti-35 Niobium (TiNb), and Ti-35 Niobium-7 Zirconium-5 Tantalum (TiNbZrTa) on mouse bone marrow stromal cells. Porous titanium alloy scaffolds were prepared by powder metallurgy. After 24 hours, cells plated on the scaffolds were analyzed by scanning electron microscopy (SEM). The antioxidant enzyme activity was measured 72 hours after cell plating. Quantitative real time PCR (qRT-PCR) was performed after 3, 7, and 14 days, and Runx2 (Runt-related transcription factor2) expression was evaluated. The SEM images showed the presence of interconnected pores and growth, adhesion, and cell spreading in the 3 scaffolds. Although differences were noted for SOD and CAT activity for all scaffolds analyzed, no statistical differences were observed (p > 0.05). The osteogenic gene Runx2 presented high expression levels for TiNbZrTa at day 7, compared to the control group (TiAlV day 3). At day 14, all scaffolds had more than 2-fold induction for Runx2 mRNA levels, with statistically significant differences compared to the control group. Even though we were not able to confirm statistically significant differences to justify the replacement of TiAlV regarding antioxidant enzymes, TiNbZrTa was able to induce faster bone formation at early time points, making it a good choice for biomedical and tissue bioengineering applications.

In vitro osteogenesis process induced by hybrid nanohydroxyapatite/graphene nanoribbons composites.

Carbon nanotubes combine high bend and mechanical strength, which is advantageous for many structural and biomedical purposes. Recently, some biomaterials, based on carbon nanostructures and nanohydroxyapatite (nHAp), have been investigated as bone substitutes in order to improve regeneration. The aim of this study was to access the expression of some RNA transcripts (involved in the process of osteoblast differentiation) by mesenchymal stem cells cultured over different nanocomposite surfaces. A multi-walled carbon nanotube (MWCNT) was firstly grown using chemical vapor deposition and then exfoliated using chemical and oxygen plasma treatments to obtain graphene nanoribbons (GNR). The hybrid composites nHAp/GNR were prepared using the wet method assisted by ultrasound irradiation with different amounts of GNR (1.0, 2.0 and 3.0 wt %). Five groups were tested in cell cultures. Group 1: synthesized nHAp; Group 2: synthesized GNR; Group 3: nHAp and 1.0% of GNR; Group 4: nHAp and 2.0% of GNR and group 5: nHAp and 3.0% of GNR. Real time reverse transcription polymerase chain reactions were performed, and all data was submitted to Kruskal Wallis and Dunn tests, at a significance level of 5%. As a result, three nanocomposites with different proportions of GNR were successfully produced. After cell culture, the expression of osteogenic genes demonstrated no significant differences among the groups and periods. However, bone morphogenetic protein II (BMP II), integrin binding sialoprotein (IBSP), and Osterix highest expressions were observed in the group containing 3.0% of GNR. In conclusion, our hybrid composites may be useful in bone interventions requiring mesenchymal stem cell differentiation into osteoblasts for healing.

The Role of MicroRNAs in the Osseointegration Process.

Regulation of cellular function is key to bone formation at endosseous implant surfaces. Osseointegration was "discovered" prior to the discovery of genetic regulation of osteoinduction or characterization of mesenchymal stem cells. Understanding osseointegration in cellular and molecular terms has benefited from genome-wide characterization of this healing process at endosseous implants in vivo. These in vivo studies also demonstrate a role for osteoprogenitor cells and cells involved in immune regulation and osteoclastogenesis. The identification of noncoding RNAs, including microRNAs, as key factors controlling cell function has highlighted the role of microRNAs in cell differentiation control. This review summarizes emerging in vitro and in vivo investigations emphasizing the role of microRNAs in the osseointegration process. Many microRNAs influence key osteoinductive pathways controlling Osterix, runt-related transcription factor 2 (RUNX2), and bone morphogenetic protein (BMP)/SMAD function. Others influence the monocyte/macrophage lineage. While significant progress has been made in elucidating the mechanisms associated with the regulation of surface modulation of osteoblast differentiation by microRNAs, knowledge gaps are evident in the identification and characterization of microRNAs linked to osseointegration. Given existing knowledge regarding the varied expression of microRNAs and their role in inflammation, it is important to understand how microRNA expression may influence the process of bone accrual at implant surfaces during osseointegration.

Masticatory performance with different types of rehabilitation of the edentulous mandible

Abstract Aim: To compare the masticatory performance associated with different rehabilitation strategies for patients with edentulous mandibles. Methods: one portion of the test food "Optocal" was provided to groups: Natural Dentition (n = 15), Mandibular Fixed Implant-Supported Prosthesis with Maxillary Fixed Prosthesis (n = 8), Mandibular Fixed Implant-Supported Prosthesis with Maxillary Removable Prosthesis (n = 14), Mandibular Implant-Retained Overdenture with Maxillary Removable Prosthesis (n = 16), and Complete Dentures (n = 16). The portion was collected after 40 chewing strokes, and then passed through a stack of eight sieves with decreasing apertures. Masticatory performance was determined by weighing the portion of food on each sieve. Results: the masticatory performance was: 71.00% for Natural Dentition, 41.57% for Mandibular Fixed Implant-Supported Prosthesis with Maxillary Fixed Prosthesis, 31.44% for Mandibular Fixed Implant-Supported Prosthesis with Maxillary Removable Prosthesis, 27.70% for Mandibular Implant-retained Overdenture, and 14.33% for Complete Dentures. The data were statistically compared using Student's t-test (p < 0.05). Natural Dentition and Complete Denture groups were statistically different from all other groups, with the Natural Dentition and Complete Denture groups exhibiting the highest and lowest masticatory performance values, respectively. Conclusions: Osseointegrated implants improved the masticatory performance of all implant-supported groups compared to the Complete Dentures group.

Effects of titanium surface anodization with CaP incorporation on human osteoblastic response.

In this study we investigated whether anodization with calcium phosphate (CaP) incorporation (Vulcano®) enhances growth factors' secretion, osteoblast-specific gene expression, and cell viability, when compared to acid etched surfaces (Porous®) and machined surfaces (Screw®) after 3 and 7days. Results showed significant cell viability for Porous and Vulcano at day 7, when compared with Screw (p=0.005). At the same time point, significant differences regarding runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and bone sialoprotein (BSP) expression were found for all surfaces (p<0.05), but with greater fold induction for Porous and Vulcano. The secretion of transforming growth factor ß1 (TGF-ß1) and bone morphogenetic protein 2 (BMP-2) was not significantly affected by surface treatment in any experimental time (p>0.05). Although no significant correlation was found for growth factors' secretion and Runx2 expression, a significant positive correlation between this gene and ALP/BSP expression showed that their strong association is independent on the type of surface. The incorporation of CaP affected the biological parameters evaluated similar to surfaces just acid etched. The results presented here support the observations that roughness also may play an important role in determining cell response.

Efeitos da diferenciação de células-tronco mesenquimais humanas sobre superfícies de implantes hidrofílicas / Effect of hydrophilic implant surfaces on differentiation of human mesenchymal stem cells

Novas superfícies de implantes foram desenvolvidas para melhorar o processo de osseointegração guiando principalmente a diferenciação de células-tronco mesenquimais humanas (CTMh) em osteoblastos. Este estudo avaliou o efeito de diferentes superfícies de implantes na diferenciação de CTMh em osteoblastos. Uma nova superfície de implante (Acqua) foi comparada com a superfície NeoPoros. As CTMh foram cultivadas em discos de titânio preparados com duas superfícies, e experimentos diferentes foram realizados para avaliar a viabilidade celular, a proliferação, a atividade de fosfatase alcalina, a mineralização e a expressão dos genes relacionados aos osteoblastos. Além disso, microscopia eletrônica de varredura e espectroscopia de fotoelétrons de raio X foram feitas para avaliar a composição química e a topografia das superfícies. Após três e sete dias, a superfície Acqua mostrou níveis mais altos de proliferação celular, quando comparada com a superfície NeoPoros (p < 0,05). A atividade da fosfatase alcalina foi seis vezes maior na superfície Acqua após 14 dias de cultura celular (p < 0,05). Além disso, a quantidade de cálcio depositado nas superfícies, devido ao processo de mineralização, foi o dobro na superfície Acqua após 14 e 28 dias (p < 0,05). Para a análise da expressão gênica, os níveis de mRNA do genes da fosfatase alcalina (ALP) e sialoproteína óssea (BSP) foram maiores para Acqua aos três, sete e 14 dias, em comparação com a superfície NeoPoros. Dentro das limitações deste estudo, a superfície Acqua foi capaz de induzir melhor diferenciação das CTMh em osteoblastos, comparadas com a superfície NeoPoros. Uma maior expressão de genes marcadores de osteoblastos, bem como maior atividade de fosfatase alcalina e teor de cálcio, foram observados para a superfície Acqua...

New implant surfaces have been developed to improve the osseointegration process mainly guiding the differentiation of human mesenchymal stem cells (hMSC) into osteoblasts. This study evaluated the effect of different implant surfaces in hMSC differentiation into osteoblasts. A novel implant surface (Acqua) was compared to Neoporos surface. hMSCs were cultured on titanium disks prepared with the two different surfaces and experiments to evaluate cell viability and proliferation, alkaline phosphatase activity, mineralization and gene expression of osteoblast marker genes were conducted. Also, scanning electron microscopy and X-ray Photoelectron Spectroscopy were conducted to evaluate the topography and chemical composition of both surfaces. After three and seven days, Acqua surface showed higher levels of cell proliferation compared to Neoporos surface (p < 0.05). Alkaline phosphatase activity was 6-fold higher on Acqua surface after 14 days of cell culture (p < 0.05). Also, the amount of calcium deposited on the surfaces due to the mineralization process was 2-fold higher for Acqua surface after 14 and 28 days (p < 0.05). For gene expression analysis, alkaline phosphatase (ALP) and bone sialoprotein (BSP) mRNA levels were higher for Acqua at three, seven and 14 days compared to Neoporos surface. Within the limitations of this study, the Acqua surface was able to better induce the differentation of hMSCs into osteoblasts compared to the Neoporos surface. Higher expression of osteoblast marker genes as well as higher alkaline phosphatase activity and calcium content were observed for Acqua...

Comparison of masticatory function between subjects with three types of dentition.

PURPOSE: The aim of this study was to evaluate the effect of an oral rehabilitation program on masticatory performance and ability as a function of the number of masticatory cycles. Subjects with a mandibular fixed implant-supported prosthesis (ISP), complete dentures (CDs), or a natural dentition (ND) were evaluated. MATERIALS AND METHODS: Masticatory performance was tested with an artificial test food (Optocal). Optocal was provided to subjects in two portions of 17 cubes and collected after both 20 and 40 masticatory cycles. The particles were collected on stacks of eight sieves. The geometric mean diameter of the chewed particles was calculated using the sieves. Questionnaires were used to assess masticatory ability before and after the fixed mandibular rehabilitation program. The geometric mean diameter of the chewed particles was compared by two-way analysis of variance followed by the Tukey test (P < .05). RESULTS: The geometric mean diameter for all groups was lower after 40 cycles versus 20 cycles. When compared to the ND group, masticatory performance for the CD and ISP groups was 12% and 28% after 20 cycles and 31% and 61% after 40 cycles, respectively. The data for the masticatory ability of the ISP group before and after fixed mandibular rehabilitation were compared by the McNemar test (P < .05), and showed that 100% of these subjects were satisfied with their chewing capacity after fixed mandibular rehabilitation. CONCLUSIONS: These results quantify the differences in masticatory function among different types of dentition. Greater masticatory function for fixed mandibular rehabilitation versus CDs was demonstrated.

Nanostructured alumina-coated implant surface: effect on osteoblast-related gene expression and bone-to-implant contact in vivo.

PURPOSE: The use of nanotechnology to enhance endosseous implant surfaces may improve the clinical control of interfacial osteoblast biology. This study investigated the influence of a nanostructure-coated implant surface on osteoblast differentiation and its effects on bone-to-implant contact (BIC) and removal torque values. MATERIALS AND METHODS: Titanium disks were machined (M) or machined and subsequently treated by acid etching (Ac) or by dipping in an aluminum oxide solution (Al2O3). Surfaces were characterized by scanning electron microscopy, atomic force microscopy, and x-ray microanalysis. For the in vitro experiment, rat mesenchymal stem cells (rMSCs) were grown in osteogenic supplements on the disk surfaces for 3 days. Real-time polymerase chain reaction (PCR) was used to measure mRNA levels of several gene products (bone sialoprotein, osteocalcin, osteopontin, and RUNX-2). For the in vivo experiment, titanium implants were placed in rat tibiae and harvested after 3 to 21 days for measurement of bone-specific mRNA levels by real-time PCR. Removal torque and BIC were measured 3 to 56 days after placement. RESULTS: Average height deviation (Sa, in nm) values for M, Ac, and Al2O3 implants were 86.5, 388.4, and 61.2, respectively. Nanostructured Al2O3 topographic features applied to machined implants promoted MSC commitment to the osteoblast phenotype. Greater bone-specific gene expression was observed in tissues adjacent to Al2O3 implants, and associated increases in BIC and torque removal were noted. CONCLUSION: Nanostructured alumina may directly influence cell behavior to enhance osseointegration.

Avaliação do comportamento de células mesenquimais humanas sobre superfícies de implantes dentários / Evaluation of differentiation and mineralization of human mesenchymal cells plated on dental implant surfaces

O objetivo deste estudo foi avaliar uma superfície de implante dentário compatível biologicamente e que aumente a resposta celular de osteoblastos de maneira a estimular o processo de diferenciação do tecido ósseo. Neste estudo foram utilizados discos de titânio comercialmente puro (cpTi) grau IV (6,0 mm x 1,0 mm) divididos em três grupos. Estes discos foram somente usinados (grupo U) ou usinados e subsequentemente tratados com ataque ácido (grupo Ac) ou usinado, jateamento e ataque ácido (grupo J/Ac). Células mesenquimais humanas indiferenciadas foram cultivadas sobre os discos e diferenciadas em osteoblastos. Os níveis de expressão de genes relacionados à diferenciação do tecido ósseo (Fostatase Alcalina-ALP; Sialoproteína Óssea-BSP; e Runx2) foram avaliados após sete e 21 dias através de PCR-tempo real (o gene GAPDH foi utilizado como controle endógeno). Após 35 dias avaliou-se a formação de nódulos de mineralização corados com Alizarin Red S. Observou-se um aumento relativo nos níveis de expressão dos genes ALP, BSP e Runx2 para a superfície com J/Ac quando comparada com as superfícies U e Ac. Após 21 dias a expressão de ALP estava 80 vezes maior na superfície J/Ac e o aumento no nível de BSP foi de 25 vezes. Após 35 dias a área mineralizada foi de 18%, 71% e 80%, para as superfícies U, Ac e J/Ac, respectivamente. Estes resultados sugerem que o jateamento da superfície previamente ao ataque ácido permitiu um maior nível de expressão de genes relacionados à cascata de diferenciação do tecido ósseo e formação de nódulos de mineralização in vitro, podendo levar a uma maior e melhor resposta de osseointegração destas superfícies.

Novel implant surfaces have been developed to improve/accelerate the osseointegration process. The mechanism by which implant surface improves osteoblast response at endosseous titanium implants is not fully understood. One of the mechanisms is related to induction of expression of bone-tissue specific genes inducing cells to differentiate into osteoblasts. The aim of this study was to evaluate a biologically compatible implant surface that can improve osteoblast responses and leads to a faster osseointegration. Commercially pure grade IV titanium disks (6.0x1.0mm) were machined (U) or machined acid etching (Ac) or sandblasted/acid etching (J/Ac), and divided into three groups. Human Mesenchymal Stem Cells were plated onto the disks and differentiated into osteoblasts. The expression levels of osteoblast-specific genes were evaluated by Real Time PCR to measure the mRNA levels of alkaline phosphatase (ALP), bone sialoprotein (BSP), and Runx2 after 7 and 21 days. The housekeeping gene GAPDH was used as a control. At 35 days, mineralization nodules were evaluated by Alizarin Red S staining. After 21 days, the expression levels of ALP for J/Ac and BSP were upregulated 80-fold and 25-fold, respectively. After 35 days, the mineralized area U, Ac and J/Ac was 18%, 71%, and 80%, for, respectively. The results demonstrated that a sandblasted/acid etched surface can affect adherent cell-bone specific gene expression, leading to a higher expression of osteoblast-specific genes and an increased in vitro mineralization response.

Management of fractured dental implants: a case report.

An implant fracture may be one of the major causes of late implant failures. Complications, such as loosening or fracture of the prosthesis restorative components, or even fracture of the implant, may occur and dental professionals should be aware of the causes of these complications. This study reports a clinical situation involving a patient restored with a mandibular overdenture that presented a fractured implant 2 years after placement. The probable cause of the implant fracture was due to biomechanical overload caused by parafunctional habits. The implant head was flattened to make it smooth, retapping the internal screw, installing a new abutment (longer), and fabricating part of the overdenture bar. This treatment was timesaving for the patient in that the prosthesis was repaired in the shortest time possible.

Use of distraction osteogenesis for repositioning of an osseointegrated implant: a case report.

This report presents a clinical case in which distraction osteogenesis was used for the vertical repositioning of an implant already osseointegrated in the maxillary right central incisor area. An adhesive prosthesis was cemented over the neighboring teeth to accomplish this procedure. The prosthesis was made with a temporary cylinder directly over the implant to guide its repositioning. After incision and osteotomy, the area that contained the implant was fixed with an implant mount screw. After initial gingival healing (7 days), activation of the distraction was begun. The screw was activated with a full turn thrice a day, for a total of 1.0 mm per day for 7 consecutive days. Thereafter, the bone was allowed to heal for 3 months. Distraction osteogenesis led to a better implant-crown relationship, even after the osseointegration of the implant, thus improving the esthetic results.