Reflection on the measurement and use of the topography of the indentation imprint.

The goal of this paper is to study the main uses of the residual imprint of the indentation test. It also discusses the different technologies and methods employed in this context. The difficulties encountered when trying to exploit the full potentials of the imprint are thoroughly examined. A survey of the literature on the quantification of the pile-up clearly shows that there is a lack of consensus on the measurement of the residual imprint as well as on treatment methods. Therefore, in order to widen the application fields of the indentation residual imprint, relevant and standardized indicators should be established.

[Mechanisms of damage to metal-on-polyethylene articulating surfaces of total hip prostheses: influence of intra-articulate migration of metallic debris]. / Mécanismes d'endommagement des pièces de frottement des arthroplasties de hanche à couple métal-polyéthylène. Influence de la migration intra-articulaire de débris métalliques.

PURPOSE OF THE STUDY: The objective of this work was to identify the mechanisms leading to deterioration of the polyethylene acetabular surface in total hip prostheses. MATERIAL AND METHODS: We conducted an in vivo analysis of damage caused to articulating surfaces of metal-on-polyethylene total hip prostheses. This analysis was performed on three of the 45 explants of Harris-Galante prostheses available to use from our series of 1480 implantations performed between 1985 and 1996. These three pieces were selected because large-sized fibers of metallic debris were identified on the polyethylene surface and because the explants had been performed for reasons other than loosening in aseptic patients. Macroscopic examination was combined with scan electron microscopy to analyze morphological changes. RESULTS: We found that identical damage could be observed on the polyethylene explants despite the different sizes of the metallic heads and different metal-on-polyethylene combinations. Our analysis confirmed the deleterious effect of metallic foreign bodies trapped in contact with the articulate surfaces. These foreign bodies resulted in one case from rupture of a multifilament wire used for the trochanteric fixation and in two cases from the surfacing of the non-cemented Harris-Galante cups. The microscopic analysis demonstrated several successive localizations of the foreign bodies on the polyethylene surface before becoming deeply encrusted in the polyethylene where they deteriorated the femoral head surface (rough) and wore the polyethylene surface (abrasion). When the fibers came from the surfacing of the Harris-Galante cups, the metallic debris remained unrecognized during the revision procedure and were only identified later during the systematic examination of prosthetic explants. DISCUSSION AND CONCLUSION: These findings emphasize the importance of quality surface treatments for non-cemented prostheses and argue in favor of particular precautions during operative manipulation of these components. A systematic analysis of the prosthetic explants is advisable, particularly for components explanted because of wear or unexplained osteolysis. Use of multifilament trochanteric wires should be avoided because rupture raises the risk of intra-articulate migration of metallic debris. If the prosthesis involves a polyethylene acetabular surface, ceramic heads should be preferred to improve resistance to abrasion, particularly to limit the deleterious effect of a third body.

An unscaled parameter to measure the order of surfaces: a new surface elaboration to increase cells adhesion.

We present a new parameter to quantify the order of a surface. This parameter is scale-independent and can be used to compare the organization of a surface at different scales of range and amplitude. To test the accuracy of this roughness parameter versus a hundred existing ones, we created an original statistical bootstrap method. In order to assess the physical relevance of this new parameter, we elaborated a great number of surfaces with various roughness amplitudes on titanium and titanium-based alloys using different physical processes. Then we studied the influence of the roughness amplitude on in vitro adhesion and proliferation of human osteoblasts. It was then shown that our new parameter best discriminates among the cell adhesion phenomena than others' parameters (Average roughness (Ra em leader )): cells adhere better on isotropic surfaces with a low order, provided this order is quantified on a scale that is more important than that of the cells. Additionally, on these low ordered metallic surfaces, the shape of the cells presents the same morphological aspect as that we can see on the human bone trabeculae. The method used to prepare these isotropic surfaces (electroerosion) could be undoubtedly and easily applied to prepare most biomaterials with complex geometries and to improve bone implant integration. Moreover, the new order parameter we developed may be particularly useful for the fundamental understanding of the mechanism of bone cell installation on a relief and of the formation of bone cell-material interface.

Effect of grooved titanium substratum on human osteoblastic cell growth.

Various surface treatments have been developed to increase the clinical performance of titanium-based implants. Many in vitro tests have been carried out on substrates with varied surface topography for a complete understanding of osteoblasts. In previous research, we made the observation that surface roughness must be taken into account, not only in terms of amplitude but also in terms of organization. In this study, we tested the adhesion and proliferation of human primary osteoblasts on grooved titanium surfaces with various amplitudes and organizations of topography. The roughness was described at a scale above (macro-roughness) or below (micro-roughness) the cell size. We observed better orientation and proliferation of human osteoblasts on surfaces with a micro-roughness characterized by a lower Order (parameter describing the organization of topography) and by a higher Ra and Rz (parameters describing the amplitude of topography). It appears that cultured human osteoblasts prefer surfaces with relatively high micro-roughness amplitude and with a low level of repeatability.

Improvement in the morphology of Ti-based surfaces: a new process to increase in vitro human osteoblast response.

Surface roughness has been shown to be an influencing parameter for cell response. In this experience we attempted to compare the effect of roughness organization of Ti6A14V or pure titanium substrates on human osteoblast (hOB) response (proliferation, adhesion). Surface roughness was extensively analyzed at scales above the cell size (macro-roughness) or below the cell size (micro-roughness) by calculation of relevant classic amplitude parameters (Ra, Rt) and original frequency parameters (Order, Delta). We developed a new process to prepare isotropic surfaces (electro-erosion), which were compared to isotropic surfaces obtained by polishing and anisotropic surfaces obtained by machine-tooling. The hOB response on electro-eroded (EE) Ti6A14V surfaces or pure titanium (Ti) surfaces was largely increased when compared to polished or machine-tooled surfaces after 21 days of culture. Moreover, the polygonal morphology of hOB on these EE surfaces was very close to the aspects of hOB in vivo on human bone trabeculae. By a complete description of the surface topography of EE surfaces, we concluded that when the topography was considered below the cell scale, hOB appreciated their isotropic smooth aspect, although when the topography was considered above the cell scale they appreciated their rough isotropic 'landscape' formed by many 'bowl-like nests' favouring cell adhesion and growth. Electro-erosion is a promising method for preparation of bone implant surfaces, as it could easily be applied to preparation of most biomaterials with complex geometries.

[Cleaning implantation burs. Observations using scanning electron microscopy]. / A propos du nettoyage des forets implantaires. Observation en microscopie electronique a balayage.

Drastic aseptic conditions are necessary in implantological treatments. A good sterilizing procedure of the specific instrumentation, like drills, is based on an efficient cleaning. Because of their design, the cleaning of drills is a real challenge. The aim of this investigation is to evaluate two different cleaning procedures usually used by implantologists. One is based on a manual cleaning, the other on an ultra-sonic cleaning. The instrument observed by scan-electron-microscope, is a I.T.I. system drill. The results show the superiority of the ultra-sonic cleaning. The manual cleaning is especially ineffective on the inside and the cutting part of the drill. Even if ultra-sonic cleaning is definitely a better procedure, it has to be improved. A extensive study should be conducted to optimize the cleaning parameters, if not, single-use drill should be definitely preferred by implantologists.

The relative influence of the topography and chemistry of TiAl6V4 surfaces on osteoblastic cell behaviour.

Proliferation and adhesion of mouse (MC3T3-E1) osteoblastic cells and primary human osteoblastic cells were carried out on Ti6Al4V titanium alloy samples with varied surface roughnesses. Mechanically or manually polished surfaces were prepared to produce respectively non-oriented or oriented residual polishing grooves. Sand-blasted surfaces were prepared using 500 microm or 3 mm alumina particles. Surface roughness parameters showed a negative correlation in comparison to proliferation and adhesion parameters. X-ray microprobe chemical surface microanalysis showed complete disturbance of the surface element composition of the Ti6Al4V alloy following sand-blasting treatment. An AlOx-enriched layer was observed on sample surfaces. This may lead to the suspicion that the concomittant effect of surface roughness amplitude and AlOx surface concentration has an effect on osteoblastic cell proliferation and adhesion. These findings show the significance of chemical surface analysis after any surface treatment of titanium-based implants before any biological use.

Qualitative and quantitative study of human osteoblast adhesion on materials with various surface roughnesses.

We quantitatively evaluated the adhesion of human osteoblasts on orthopedic metallic substrates (Ti6Al4V alloy) with various surface roughnesses at several times after inoculation and studied its correlation with qualitative changes in the expression of adhesion proteins and with parameters extensively describing the surface topographies. Cells were orientated in a parallel order on polished surfaces. This orientation was not affected by residual grooves after polishing. On sandblasted surfaces the cells never attained confluence and had a stellate shape, and the cell layer had no particular organization. Extracellular matrix (fibronectin, type I collagen, osteopontin) and cytoskeletal protein (actin, vinculin) orientation reflected the cell layer organization. In our experiment human osteoblasts expressed alpha3beta1 integrin but not alpha2beta1 integrin. In addition to currently analyzed roughness magnitude parameters, we calculated roughness organization parameters (fractal dimension parameters) of the substrates. We observed lower adhesion and proliferation on less organized surfaces (i.e., sandblasted ones). The significant statistical correlation observed between fractal dimension parameters (describing surface roughness organization) and cell parameters adds a new concept to the studies of substratum roughness influence on cell behavior. An attempt at modelization of the cell-surface interaction was made that includes the influence of fractal dimensions parameters.

[The in vitro biological behavior of TiNb30 alloy treated with hydroxyapatite and tricalcium phosphates]. / Le comportement biologique in vitro d'un alliage TiNb30 traité avec hydroxyapatite et phosphates tricalciques.

An in vitro study has been carried out in different cell systems to determine the biological response of TiNb30 alloy before and after a surface treatment with hydroxyapatite (HA) and tricalcium phosphate (TCP) by the sol-gel method. TiNb30 pure Ti induce favorable cell viability with respect to pure Ni showing a high cytotoxic effect. After surface treatment with HA or HA-TCP mixtures, no difference in cell proliferation can be observed between amorphous and cristalline forms. However, HA decreases (75 +/- 15%) and HA-TCP mixtures increase (133 +/- 11%) significantly cell proliferation compared with controls.

[In vitro and in vivo biocompatibility of stainless steel as a function of surface treatments: roughness and surfacing with hydroxyapatite]. / Biocompatibilité in vitro et in vivo de l'acier inoxydable en fonction du traitement de surface: rugosité et revêtement avec hydroxyapatite.

The in vitro tests on cell viability reveal a favorable position for steel and hydroxyapatite (HA)? However, the roughness induces a negative effect on cell proliferation. Sandblasting of the stainless steel considerably decreased cell number compared with the polished substrate. HA showed a better percentage of proliferation in spite of the surface effect compared with controls. For in vivo biocompatibility, intramuscular implants revealed localized inflammatory reactions for the HA treated stainless steel but nor for the untreated alloy.

Dimensional stability of seven elastomeric impression materials immersed in disinfectants.

Dental impressions can increase the transmission of microorganisms and infections. The purpose of this study was to assess the influence of three disinfectant solutions on the dimensional accuracy of seven elastomeric impression materials. Impressions of a test block were either left untreated (controls) or treated by immersion in a disinfectant solution. Measurements were taken on die stone replicas of the impressions. Comparisons were made between (1) the measurements for the variations in the nontreated impressions and those for the treated impressions and (2) measurements for the treated impressions and the test block. Results indicated that the aminoamphoteric agent or glutaraldehyde derivative-based solutions created little change in relation to the initial dimensional accuracy of the impression products. However, the sodium hypochlorite solution often leads to expansion by comparison with controls. By comparison to the test block, this expansion then makes it possible in most cases to obtain better dimensional accuracy than initially. Within the limits of this study this expansion could lead to an improvement in clinical fixed prosthodontic procedures.

Corrosion of surgical implants.

Corrosion on orthopaedic implants has been studied. Twelve intramedullary nails and twelve osteosynthesis plates were implanted up to eight and thirteen years, respectively. Analysis of biological fluids from all patients was carried out and revealed high concentrations of nickel and chromium that correlated to the implantation time. All implants were corroded by both crevice and intergranular corrosion. Intergranular corrosion is related to mechanical and heating treatments. Crevice-like corrosion is probably enhanced by sulphur present in amino-acids. Electronic probe analysis shows the reaction study between both sulphur and nickel and sulphur and chromium. These results are compared to the metal distribution in body fluids. After a certain incubation time the corrosion accelerates as is characteristic for crevice-like corrosion processes. Studies of the distribution rate of two Ni-Fe-Cr dental alloys in a cell culture system give similar results: metal-ion release increases with the exposure time.

Investigations of the presence of serum antibodies to Epstein-Barr virus in patients with various tumors.

Serum samples from 150 patients with various malignant or benign tumors and from 20 clinically healthy subjects were tested by indirect immunofluorescence (IF) reaction for the presence of specific antibodies to Epstein-Barr-virus-determined viral capsid antigen (EB VCA). The IF test-carried out in multitest-slide EB3 and Raji cell preparations-revealed antibodies to EB VCA in 102 of the patients with tumors and in 4 of the healthy persons.