Biomechanical and histomorphometric investigations on two morphologically differing titanium surfaces with and without fluorohydroxyapatite coating: an experimental study in sheep tibiae

Role of BMP-7 on biological parameters osseointegration of dental implants: Preliminary results of a preclinical study

The aim of this work was to analyze and compare the effect of bone morphogenetic protein-7 on biological parameters related to implant osseointegration in an experimental animal model. Sixteen dental implants were placed in the tibias of four randomly selected minipigs for the following dental implant surface treatments: Group A: conventional treatment of the dental implant surface by SLA (n = 8) and Group B: treatment of the dental implant surface with carboxyethylphosphonic acid and bone morphogenetic protein-7 (n = 8). The animals were sacrificed one month after dental implants placement and a histomorphometric study was performed for the evaluation of bone-to-implant contact, corrected bone-to-implant contact, new bone formation, interthread bone density and peri-implant density using Student's t-test and the non-parametric Mann-Whitney test. The histomorphometric parameters bone-to-implant contact and corrected bone-to-implant contact showed statistically significant differences between the study groups; 34.00% ± 9.92% and 50.02% ± 10.94%, respectively (p = 0.004) for SLA and 43.08% ± 10.76% and 63.30% ± 11.30%, respectively (p = 0.003) for BMP-7. The parameters new bone formation, interthread bone density and peri-implant density did not show statistically significant differences between the study groups (p = 0.951, p = 0.967 and p = 0.894, respectively). Dental implant surfaces treated with carboxyethylphosphonic acid and BMP-7 improve the biological response of dental implants to osseointegration.

Assessment of the Tissue Response to Modification of the Surface of Dental Implants with Carboxyethylphosphonic Acid and Basic Fibroblastic Growth Factor Immobilization (Fgf-2): An Experimental Study on Minipigs

Simple Summary

This study aimed to evaluate the efficacy of treating the surface of dental implants with carboxyethylphosphonic acid for the immobilization of FGF-2, the influence of FGF-2 on cortical bone in close contact with dental implants, new bone formation around dental implants in the presence of FGF-2 and the influence of FGF-2 on the interthread bone area of dental implants during the healing period after insertion.

Abstract

The aim of this study was to evaluate the effect of implant surface treatment with carboxyethylphosphonic acid and fibroblast growth factor 2 on the bone–implant interface during the osseointegration period in vivo using an animal model. The present research was carried out in six minipigs, in whose left tibia implants were inserted as follows: eight implants with a standard surface treatment, for the control group, and eight implants with a surface treatment of carboxyethylphosphonic acid and immobilization of FGF-2, for the test group. At 4 weeks after the insertion of the implants, the animals were sacrificed for the histomorphometric analysis of the samples. The means of the results for the implant–bone contact variable (BIC) were 46.39 ± 17.49% for the test group and 34.00 ± 9.92% for the control group; the difference was not statistically significant. For the corrected implant–bone contact variable (BICc), the mean value of the test group was 60.48 ± 18.11%, and that for the control group, 43.08 ± 10.77%; the difference was statistically significant (p-value = 0.035). The new bone formation (BV/TV) showed average results of 27.28 ± 3.88% for the test group and 26.63 ± 7.90% for the control group, meaning that the differences were not statistically significant (p-value = 0.839). Regarding the bone density at the interthread level (BAI/TA), the mean value of the test group was 32.27 ± 6.70%, and that of the control group was 32.91 ± 7.76%, with a p-value of 0.863, while for the peri-implant density (BAP/TA), the mean value of the test group was 44.96 ± 7.55%, and that for the control group was 44.80 ± 8.68%, without a significant difference between the groups. The current research only found a significant difference for the bone–implant contact at the cortical level; therefore, it could be considered that FGF-2 acts on the mineralization of bone tissue. The application of carboxyethylphosphonic acid on the surface of implants can be considered a promising alternative as a biomimetic coating for the immobilization of FGF-2. Despite no differences in the new bone formation around the implants or in the interthread or peri-implant bone density being detected, the biofunctionalization of the implant surface with FGF-2 accelerates the mineralization of the bone–implant interface at the cortical level, thereby reducing the osseointegration period.

Biomedical Coatings to Improve the Tissue-Biomaterial Interface

One of the most important factors determining the degree of tissue interaction of an implanted device is the property of its surface. Thus, great importance is given to chemical and morphological characteristics of biomaterial surfaces to improve biocompatibility, cell migration, proliferation and differentiation, mechanical stability and endogenous tissue ingrowth.

In order to obtain new and healing stimulating properties, it is possible to apply a coating or more generally a surface treatment to the surface of a prosthetic device. One of the most versatile methods for coating is thermal spray technology. This paper considers the principle of thermal spray processes and their application in the biomedical field, namely the coatings used for orthopedic prostheses and dental implants. Among thermal spray processes, plasma spray as well as High Velocity Oxygen Fuel (HVOF) processes will be particularly considered and their most important aspects will be illustrated.

Effect of microgrooves and fibronectin conjugation on the osteoblast marker gene expression and differentiation

PURPOSE

To determine the effect of fibronectin (FN)-conjugated, microgrooved titanium (Ti) on osteoblast differentiation and gene expression in human bone marrow-derived mesenchymal stem cells (MSCs).

MATERIALS AND METHODS

Photolithography was used to fabricate the microgrooved Ti, and amine functionalization (silanization) was used to immobilize fibronectin on the titanium surfaces. Osteoblast differentiation and osteoblast marker gene expression were analyzed by means of alkaline phosphatase activity assay, extracellular calcium deposition assay, and quantitative real-time PCR.

RESULTS

The conjugation of fibronectin on Ti significantly increased osteoblast differentiation in MSCs compared with non-conjugated Ti substrates. On the extracellular calcium deposition assays of MSCs at 21 days, an approximately two-fold increase in calcium concentration was observed on the etched 60-µm-wide/10-µm-deep microgrooved surface with fibronectin (E60/10FN) compared with the same surface without fibronectin (E60/10), and a more than four-fold increase in calcium concentration was observed on E60/10FN compared with the non-etched control (NE0) and etched control (E0) surfaces. Through a series of analyses to determine the expression of osteoblast marker genes, a significant increase in all the marker genes except type I collagen α1 mRNA was seen with E60/10FN more than with any of the other groups, as compared with NE0.

CONCLUSION

The FN-conjugated, microgrooved Ti substrate can provide an effective surface to promote osteoblast differentiation and osteoblast marker gene expression in MSCs.

Structural influence from calcium phosphate coatings and its possible effect on enhanced bone integration

OBJECTIVE

The aim of this review was to summarize our present knowledge about calcium phosphate (CaP) coatings on implants with respect to their topographical appearance at micrometer as well as nanometer level and also the reported influence on bone healing.

MATERIAL AND METHODS

The PubMed database was used with the key words - surface roughness, CaP coating, implant, bone integration, clinical studies, experimental studies - used in different combinations. Only in vivo studies were taken into consideration.

CONCLUSIONS

A significantly improved healing capacity associated with CaP-coated implants is often reported, but individual importance of the several modes of surface changes introduced, deliberately or not, is usually very difficult to interpret. Several studies claim this difference to be due to altered chemistry, but in many the result may equally well be dependent on the surface topography. The few studies that have been published indicate that nanometer structures have an impact on early bone healing. However, the optimal size and distribution of nanometer-sized particles or pores applied on implant surfaces is still unknown, as are the evaluation effects of micrometer roughness. Improved surface characterization is needed if we are to reveal effects dependent on isolated nanometer alterations.

In vivo preclinical evaluation of the influence of osteoporosis on the anchorage of different pedicle screw designs

We investigate the anchorage of pedicle screws with different surface treatments in osteoporotic bone. Eight ewes were divided into two groups of four animals each: four sheep underwent bilateral ovariectomy (OVX Group), whereas the operation was simulated in the remaining group (SHAM Group). Eighteen months after the first operation, the Dynesys(®) System was fitted to the sheep using pedicle screws with three different surface treatments: untreated, rough blasted (uncoated) and bioactive coated (bioactive). Uncoated screws showed a significantly higher bone ingrowth value compared with the untreated screws in the OVX group (9.3%, p < 0.005) and a significantly lower bone ingrowth value in the SHAM group (-11.0%, p < 0.05). Furthermore, the bioactive pedicle screws had a significant lower bone ingrowth value than the untreated screws in the SHAM group (-12.1%, p < 0.05). These results suggest that both tested surface treatments of pedicular screws may provide an advantage in terms of bone quality and osseointegration, when implanted in osteoporotic vertebrae.

Histomorphometric analysis of pure titanium implants with porous surface versus rough surface

The purpose of this study was to analyze the bone repair around commercially pure titanium implants with rough and porous surface, fabricated using powder metallurgy technique, after their insertion in tibiae of rabbits. Seven male rabbits were used. Each animal received 3 porous-surface implants in the left tibia and 3 rough-surface implants in the right tibia. The rabbits were sacrificed 4 weeks after surgery and fragments of the tibiae containing the implants were submitted to histological and histomorphometric analyses to evaluate new bone formation at the implant-bone interface. Means (%) of bone neoformation obtained in the histomorphometric analysis were compared by Student's t-test for paired samples at 5% significance level.. The results of the histological analysis showed that osseointegration occurred for both types of implants with similar quality of bone tissue. The histomorphometric analysis revealed means of new bone formation at implant-bone interface of 79.69 ± 1.00% and 65.05 ± 1.23% for the porous- and rough-surface implants, respectively. Statistically significant difference was observed between the two types of implants with respect to the amount new bone formation (p<0.05). In conclusion, the porous-surface implants contributed to the osseointegration because they provide a larger contact area at implant-bone interface.

Design of dental implants, influence on the osteogenesis and fixation

The fixation and the bone ingrowth at the interface of porous cylindrical implants (total porosity of 37% and average pores diameter of 480 microm) were compared in vivo to rough cylindrical implants (R (a) = 5.3 microm), both of commercially pure titanium, made by powder metallurgy. The implants were inserted into the tibias of 20 rabbits and the animals were sacrificed 4 and 8 weeks after surgery. The percentage of bone-implant contact observed in porous implant was significantly larger than in the rough ones for all of sacrifice periods, respectively, 57% vs. 46% after 4 weeks, and 59% vs. 50% after 8 weeks. The mechanical tests showed a significant increase in the shear strength of the porous implants for the two analyzed periods, 4 and 8 weeks (14 and 20 MPa), when compared with rough ones (4 and 13 MPa). These results suggest that porous implants improve the contact at the implant-bone interface and increase the fixation to the bone, improving the osseointegration. Thus, the porous implant might be an alternative to dental implant in less favorable conditions, and appear to be better fixed to bone, offering promising alternatives.

Calcification at the Interface Between Titanium Implants and Bone: Observation With Confocal Laser Scanning Microscopy

It has not been previously possible to observe bone formation in undecalcified sections with titanium implants at high magnification because of the difficulty in sectioning bone together with implants. A method for examining the bone-implant interface in undecalcified sections is described in which implants are left in situ and confocal laser scanning microscopy (CLSM) is used to examine both the implant surface and adjacent bone. Pulsing of animals at different times with the fluorescent dyes calcein and alizarin red permitted assessment of temporal patterns of bone formation by CLSM. Reflectivity of the polished implant surface permitted accurate assessment of the position of the implant relative to labeled bone. The analysis showed that bone first formed as thin processes towards and across the implant surface, followed by further bone formation behind these processes. The interface between calcified bone tissue and the implant surface was characterized by a 10-μm space. The CLSM technique enabled detailed observations of new bone formation at the titanium implant interface.

In vitro behaviour of osteoblasts cultured on orthopaedic biomaterials with different surface roughness, uncoated and fluorohydroxyapatite-coated, relative to the in vivo osteointegration rate

The effects of two surfaces with different roughness (Low Roughness, LR: Ra: 5.6-5.9 microm; High Roughness, HR: Ra: 21.5-22.5 microm), uncoated and fluorohydroxyapatite(FHA)-coated, were investigated in MG-63 osteoblasts. At 72 hours, cells proliferated on biomaterials more slowly than in the control group (p < 0.0001), the proliferation rate was higher on FHA-coated LR than uncoated HR (p = 0.037). Collagen-I production was positively affected by the LR surface (p = 0.001) as compared to controls, while it was significantly lower (p = 0.0001) in the HR surfaces. Compared to controls, LR and HR surfaces led to enhanced production of TGF-beta1, further improved by FHA (FHA-coated LR: p = 0.007; FHA-coated HR p < 0.0001 respectively). ALP, OC, IL-6 and TNF-alpha levels were not significantly different from the controls. Results suggest that collagen-I production could be useful in predicting the in vivo osteointegration rate of biocompatible biomaterials observed in previous studies.