|
Dry-contact Analysis
|
Wear
(friction/lubrication) |
Sliding Test |
Micro-arc anodised cp-Ti, vs
-
•
hydrothermal; 130 °C 80 kPa,
-
•
heat; 5 °C/min 400 and 600 °C, 1 h
|
Reciprocate tribometer: WC (Co) ball, ⌀6 mm, 3 N, 1 cm/s, half-amp of 1 mm, 9 m distance. |
-
•
One order lower of wear rate difference between hydrothermal and heat threatened anodised layer,
-
•
hydrothermal have similar rate with standard anodised Ti.
|
[282] |
| Friction Test |
Microstructured composite anodised Ti-10V-2Fe-3Al;
|
Ball-on-disc rotating: Si3N4 ball, ⌀2 mm, roughness ~0.01 mm, 100 g load rotation in ⌀4 mm, 100rpm. |
-
•
Worn surface decreases with the increase anodising time, enhanced wear resistance of composite anodised sample with thicker films.
-
•
Denser latex particles incorporated in the layer produced less wear loss, thus lubricating on the worn surface, reduced friction coefficient.
|
[183] |
| Tensile Test |
Microstructured cp-Ti M4 screws. |
Fixture anodised screw to nut (tightened-untightened); torque wrench 2 Nm from initial zero load, I∠300°, Motosh ISO 16047. |
-
•
Increased layer thickness decreased the coefficient of friction, COF between 10-40%, depends proof load (max 70%).
-
•
COF min. attained at anodising 40V–50V corresponds to 0.14–0.24 μm thickness, above these: COF increased eventually (ca. 0.6 to 0.8 static COF).
|
[318] |
| Wear-life Test |
Anodised cp-Ti before and after coated by diamond-like carbon (DLC) |
Reciprocated ball-on-plate friction (GCr15 stainless ⌀6 mm), distances 1 N for 100 m &10 N for 1500 m; 0.075 m/s.
|
-
•
Friction coefficient of the composite coating and the DLC mono-film was similar under both light & heavy load (composite wear-life: ca. 43% longer than DLC mono-film)
-
•
Altered bottom TiO2 film provided necessary hardness and load support. The wear rate of titanium with protective composite was much lower than Ti with DLC mono-film.
|
[307] |
Adhesion
(detachment/peel/flake-off/delamination) |
Scratch Test |
|
PEO Ti6Al14 V at 20–90 min. |
Progressive load: 0.3–10 N along 5 mm, scratched using 200μm radius Rockwell C diamond tip. |
-
•
No failure produced at 90 min, although coating is more porous and looser than the one produced at 60 min.
-
•
An adhesive at the edge and cohesive failure in the inner layer of scratch track occur, produced higher critical load (60 min; failed at ca. 5.3N, cracked at ca. 6.2N & delaminated at ca 6.7N), implied greater adhesion and bonding strength.
|
[283] |
|
Micro-arc Anodised cp-Ti, vs
-
•
hydrothermal; 130 °C 80 kPa,
-
•
heat; 5 °C/min 400 and 600 °C, 1 h
|
Linear ramp 0–400 mN constant load, 600 mm scratch length, 10 mm/s |
|
[282] |
Deformation
(stress shielding/stiffness) |
Indentation Test |
|
Microstructured cp-Ti M4 screws |
Vickers hardness 100 gf (1 N) load. |
Anodic layer thickness increased exponentially from 0.23μm (60V) to a max. of 3.4 μm (100V), implied an increase in mean surface hardness (ca. 380 to 420). |
[318] |
| TNTs at single and two-stage AO, with and without heat treatments |
Vickers; 10 indentations performed randomly per 3 different samples with load of 0.98 N (0.1 kgf). |
-
•
No significant differences in roughness between samples (Ra ca. 130nm) but the hardness for untreated (ca. 240 HV) notably lower than TNTs (ca. 290 HV).
-
•
The second anodic treatment and heat treatment led to an increase of hardness, highest value was: group 2 stages AO + heat treatments (ca. 340 HV).
|
[298] |
|
Micro-arc Anodised cp-Ti, vs
-
•
hydrothermal; 130 °C 80 kPa,
-
•
heat; 5 °C/min 400 and 600 °C, 1 h
|
Oliver and Pharr: loads 0.14400 mN, 10 cycles, Berkovich tips |
-
•
H/E ratio (elastic strain to failure) of hydrothermal anodic layer was lowest, reiterates the instability due to cracking left by nanoindenter, means highest wear rate.
-
•
Heat treated anodic slightly increases the H/E but still lower compared to standard anodised Ti.
|
[282] |
| TNTs via optimised-AO on commercial dental implants (abutments and screws) |
Oliver and Pharr: loading force 10,000 μN, Berkovich tip, depth max.10% of the thickness |
-
•
Standard TNTs have compromised the edges of implant threads leading to delamination and fracture.
-
•
The optimised TNTs, greatly enhanced elastic modulus (ca. 40–60 GPa), significantly outperformed standard TNTs (ca. 4–8 GPa), while retaining desirable hardness (ca. 2.5 GPa).
|
[290] |
|
Wet-contact Analysis
|
Wear
(detachment/debris/ion release) |
Tribocorrosion Test |
Usually using flat tribometer coupled to a potentiostat; tested either in;
-
•
Sodium chloride (NaCl) [281]/
-
•
Phosphate buffer saline (PBS) [298]/
-
•
Hank's solutions [189]/
-
•
Fusayama's artificial saliva [287]
|
CaP MAO microporous-Ti vs acid-etched microporous-Ti
-
•
porous Ti having closed and interconnected pores (22 and 37% porosities).
-
•
Anodised: MAO 300V, 1 min DC, 200rpm. While control: etched 24 h in Kroll's reagent
|
NaCl tribo-cell: used pin-on-disc tribometer, working substrate facing upwards, 7 mm zirconia pin spherical end 100 mm radius as counter material, mounted vertically above the exposed area (1.13 cm2), rotated clockwise. Open circuit potential (OCP, 25 °C) before, during and after sliding stable at ΔE <60 mV h−1, pin loaded then slide unidirectional, track ⌀4 mm, 1 Hz (60 rpm), 30 min (1800 cycles), 3 N load, Hertzian 80.8 MPa. After sliding, pin unloaded and OCP kept on monitoring for 30 min. |
-
•
All bio-functionalised samples had higher OCP values before, during, and after sliding (but anodised Ti performed better than acid etched samples), indicating a lower corrosion tendency, not only due to the improved corrosion resistance of the oxide layers formed on the outer and pore surfaces, but also due to their high hardness and thus high wear resistance.
-
•
During tribocorrosion, the counter material primarily slides over the protruding anodized surfaces, causing the functionalised surfaces to suffer less mechanical damage. Debris removal from pores also reduced third-body abrasion, resulting in improved tribocorrosion performance.
-
•
Anodised Ti outperformed acid etched Ti in general.
|
[280] |
| CaP PEO cp-Ti with and without annealing treatment |
PBS tribo-cell: sample counterfaced alumina ball ⌀6-mm, 5 N, 1 mm linear peak-to-peak displacement, 1 Hz; 350 cycles. OCP measured for 1 h, for each normal load tested, the region of sliding was changed. |
-
•
Tribocurrent (Itcorr) rose after ca.240 s of sliding began and lowered significantly compared to cp-Ti & cp-Ti before annealing.
-
•
For 400V samples, no significant variation, differences in tracks of smashed oxide wear (from the porous outer layer); but compact inner layer sustains the contact load during sliding and minimises exposition of the substrate.
|
[319] |
| TNTs at single and two-stage AO, with and without heat treatments |
PBS tribo-cell: OCP with a tribometer of pin-on-plate, WE against alumina ball (⌀10 mm, 1 Hz, 0.5 N, amp 2 mm), 30 min sliding after OCP stabilised 2 h ΔE <60 mV/h. After sliding, the counter material was removed and OCP continued to be recorded for 30 min. |
-
•
Coefficient of friction; untreated is the highest (0.7 ± 0.1) followed single AO and two-stage AO (0.6 ± 0.1), and then heat treated AO (0.5 ± 0.1).
-
•
Wear tracks: untreated presented parallel ploughing grooves, adhered/oxidised patches, and plastic deformations.
-
•
Irregular wear track shapes observed for single AO and two-stage AO (detachment of the TNTs), both presented similar wear features to the substrate. But heat treated groups (heat on single AO va two-stage AO) presented dissimilar behaviour; two-stage AO better where no evidence of detachment at the border of wear tracks nor sliding grooves were observed.
|
[298] |
| Two-stage reverse-polarised-AO TNTs with and without doped elements Ca/P/Zn |
Fusayama's tribo-cell: pin- on-disk reciprocated sliding (Al2O3 ball ⌀10 mm). OCP conducted during two independent cycles; reciprocating sliding & after each period solicitations, 1800 s followed 2000 s to stabilised. Sliding tests; 1 N, 400 MPa, 1 Hz, linear displacement amplitude is 650 μm. |
-
•
TNTs achieved stable OCP around −0.14 V, differs strikingly from TNTs-Ca/P/Zn which stabilised around 0.11–0.12 V.
-
•
COF measured during the first & second sliding cycle lasted for 1800 s with no significant differences between samples
-
•
Wear volume loss was found significantly higher for TNTs than TNTs-Ca/P/Zn. No detachment observed outside the contact region for these samples and the survival of TNTs was detected even in the border and central regions of their wear tracks.
-
•
Formation of the tribofilm during mechanical solicitations might be promoted by their improved wear resistance.
|
[287] |
Corrosion
(pitting/ion release/fretting/crevice)
|
Electrochemical Test |
|
PEO Ti-13Nb-13Zr in ultrasonically dispersed Zr-nanoparticles + acidic electrolyte |
Integral investigations: OCP (20h) & potentiodynamic () perform via Voltalab potentiostat, while EIS using Zennium potentiostart (±10mV, 10m–100M Hz).
|
-
•
OCP for PEO samples higher than Ti substrate indicating that PEO coating shows higher resistivity against corrosive attack than the non-coated substrate.
-
•
Tafel curves: reduced for more than two orders of magnitude for PEO coating than the uncoated samples; the corrosion currents decrease with increasing current density applied in the PEO treatment.
-
•
PEO inner barrier Ri = 1.54 MΩ/cm2 (untreated 160 kΩ/cm2) and the outer porous Rp = 162 kΩ cm2 show that resistance of the inner layer plays a crucial role for the enhanced corrosion resistance.
-
•
Theoretical capacitances, CPE roughly deviate by a factor of 10 from the fitted values, indicating the incompleteness of the fitting model.
|
[209] |
|
TNTs vs structured-optimised, SO-TNTs via multistage AO
|
Integral Investigation: OCP ±250mV, 0.3 mV/s at 22 °C CH1660D workstation, 60 min to stabilise, scans 1500s. Tafel curves measured at 0.01 V/s, E(V) = −1 to final E(V) = 0.
|
-
•
OCP: SO-TNT (ca. −0.06 V) presented lower corrosion tendency than NT (ca. −0.28 V).
-
•
Corrosion current density of bare Ti and NT were measured as 0.77 μAcm−2 and 14.41 μAcm−2, whereas SO-TNT was 0.07 μAcm−2. Obviously, SO-TNT has significantly reduced the corrosion potential and corrosion current density.
-
•
Formation of interfacial layer in SO-TNTs act like a “barrier”, which prevents the underlying Ti substrate from erosion.
|
[320]
|
In/ex vivo
|
Example in/ex vivo studies on Anodised Ti
|
Histomorphometry [321]
-
•
histologically and quantitatively assesses bone cells, growth, tissue remodeling, bone architecture, and repair
-
•
both the activity of bone cells and the amount and distribution of bone tissue can be analysed
|
Bone Implant Contact (BIC) Visualisations (qualitative measure)
|
Routine Histological [315]
-
•
stained site shows more cellular detail, but underemphasises the mineralised bone
-
•
does not permit direct evaluation of BIC or bone neoformation near implant surface upon removal/damage of mineral content
|
Micro-arc anodised RBM Ti dental implants, placed in sheep mandible
|
Fixed in formalin, dehydrated with ethanol, cleared with xylol and set in C5H8O2., then sectioned and glued to plastic slides, polished by silicon carbide, then stained with one part of MacNeal's tetrachrome followed by two parts of toluidine blue. |
-
•
No evidence of inflammation or titanium particles found within the tissue.
-
•
Untreated surface had large masses of disorganised calcified material filling the thread, appeared to be resorbed bone tissue or residual debris.
-
•
Anodised surfaces showed less debris than the control, largely incorporated into new bone, filling the threads.
-
•
BIC for anodised surfaces were more than 70% relative to control.
|
[53] |
| Micro-arc anodised Ti inserted into the bone marrow in the femurs' Wistar rats
|
Fixed in formaldehyde, decalcified with C10H16N2O8 acid, set in paraffin & sectioned before stained with haematoxylin and eosin. |
-
•
Many osteoblasts with a cuboidal shape were observed aligned on the bone newly-formed on anodised Ti,
-
•
Deposited CNH induced newly-generated bones with proteoglycans, drives higher BIC% rate, indicates better “contact osteogenesis”.
|
[59] |
| Sand-blasted vs PEO microstructured surface of screw-shaped Ti-6Al-4V implants, drilled in rabbit tibias
|
Tissue was fixed with plastic, and subjected to Haemotoxylin and Eosin staining. |
-
•
No signs of inflammation, both structures were in direct contact with the surrounding cortical bone and bone marrow.
-
•
Upon implant removal, amount of newly formed bone around anodised surface was higher than sand-blasted surface.
-
•
Overall BIC% no difference but the ratio of new bone created nearby the implant fixture was more than doubled in the anodised sample compared to sand-blasted sample.
|
[317] |
| LENS™ printed CaP coated porous Ti implants (25% porosity); surface modified by depositing TNTs, followed by doping Sr2+ and Si4+ via SBF
|
Fixed in formalin, dehydrated via ethanol series finishing with acetone, embedded into Spurs resin, mounted on glass slides, then stained with modified-Masson Goldner's trichrome [322] |
-
•
Osteoid-like new bone formation has been observed even at the 4 weeks' time, with more been noticed after 10 weeks of implantation on specimen's dopants with Sr and Si compared to just TNTs film.
-
•
Almost 100 % BIC noticed after 10 weeks in Sr & Si dopants TNTs compared to ca. 60% BIC in control samples.
-
•
Strong bone interlocking, confirms by presence of no gaps at the implant interface in the CaP/TNTs-coated implants.
|
[323] |
| Commercial Ti dental implants with surface treated by crystallisedHAp vs sand-blasted/acid-etched vs TNTs; installed in sheep’ iliac crest
|
Trephined samples fixed in formalin, dehydrated with ethanol, embedded in
light-curing resin, stained with Toluidine blue + acid fuchsin |
-
•
After 2 weeks: nanostructured surface showed large trabeculae of neoformed bone between threads and islands of bone debris in contact with the trabecular bone.
-
•
Sand-blasted/acid-etched microstructured surface present similar degree of bone volume but less extensive trabeculae, bone debris between the threads.
-
•
Microstructured anodised surface showed bone trabeculae permeating the implant surface at a lower volume than either other 2 samples but with a similar BIC area.
-
•
After 4 weeks, newly formed bone around the implants were clearly apparent with minimum amount of connective tissue was observed in all groups.
-
•
Overall BIC higher than 80% with no statistical difference in between groups.
-
•
All groups experienced a constant increase in trabecular bone fixation to the implant surface from 2 to 4 weeks.
|
[324] |
Nano vs macro-threaded anodised Ti implant;
-
•
TNTs ⌀30, 50, 70, 100nm inserted into the right & left rat’ femur at osteotome sites
-
•
implantation period: 2 & 6 weeks
|
Fixed in formalin, decalcified with EDTA, embedded in paraffin, sections stained with hematoxylin-eosin (H&E) |
-
•
New bone formed near cortical bone difficult to differentiate, then the one unsuccessful histomorphometric: within the sponge bone is easy to differentiate therefore is measured.
-
•
During implant removal, new interface or severely damaged then difficult to analyse. The results showed higher BIC% in 30nm and 70 nm groups at 2 and 6 weeks
|
[310] |
| Machined cp-Ti implants vs Anodised cp-Ti (TNTs) implants placed in rats' right tibia
|
Fixed in formaldehyde nondecalcified; dehydrated in ethanol, soaked and inlaid in methyl methacrylate; glued to a plexiglass with acrylate-based adhesive; crushed and polished using silicon carbide, then stained in Stevenel's blue/Alizarin red |
-
•
Histologic qualitative analyses showed bone formation in close contact with the implant for both groups.
-
•
The histomorphometric analyses showed that cp-Ti machined (BIC 37.89%) had a lower percentage of bone area compared with cp-Ti anodised (58.97%)
|
[325] |
|
Biomechanical Analysis [326]
|
BIC Strengths (qualitative measure) |
Pull-out Test |
Sand-blasted VS PEO microstructured surface of Screw-shaped Ti-6Al-4V implants, drilled in rabbit tibias
|
Fixture mounted the implant and the torque meter, fastened to 35 Ncm and connected to a torque meter. Torsional removal value recorded over the reverse-rotation of its placement. |
-
•
Average removal torque was 49.7 Ncm for sand-blasted sample and 51.5 Ncm for the anodised sample.
-
•
Greater torque rotation forces required to remove the implants anodised surface, suggest higher strengths of osseointegration of the structure.
|
[317] |
| TNTs doped with Si implanted in rat femur
|
Direct pull-out from implanted site at speed of 1 mm/s. The maximal force was the pull-out force. |
The peak pull-out force for S-doped sample was increased by 18% and 54% compared to TNT and Ti screws, respectively |
[71] |
| Nano vs macro-threaded anodised Ti implant; TNTs ⌀30, 50, 70, 100nm inserted into the right & left rat’ femur at osteotome sites
|
Fixed implant placed at removal torque test apparatus, connected with conventional digital torque gauge. Installed screw driver connected to implant’ upper notch and rotated in an anticlockwise direction. Peak value when broken was recorded |
Macro threaded showed higher removal torque than nano threaded. 30nm and 70nm TNTs at 2 weeks and 6 weeks showed the highest value; but no significant difference. |
[310] |
| Machined cp-Ti vs anodised cp-Ti (TNTs) placed in rats' right tibia
|
Specimens placed on a workbench, aligned with torque meter. An adapted wrench applied counter clockwise for implant removal |
The removal torque analyses showed that the Group cp-Ti machined (1.15 ± 0.01, N/cm) had significantly lower values than the Group cp-Ti anodised (1.44 ± 0.01, N/cm) |
[325] |
| Implant Stability Quotient (ISQ) [324]
|
Resonance frequency analysis (RFA) |
Micro-arc anodised RBM Ti dental implants placed in sheep mandible, implanted site was dissected en bloc prior to testing.
|
ISQ obtained in pairs at right angles projected RFA to each mandible's buccolingually and mesiodistally |
There was no statistically significant difference in RFA mean values or trends measured at surgery to a month healing, showing ISQ values do not correlate with histomorphometric figures. |
[53] |
| Commercial Ti dental implants with surface treated by crystallisedHAp VS sand-blasted/acid-etched VS AO; installed in sheep’ iliac crest
|
magnetic transducers were mounted on each implant and tightened with hand pressure using the metallic (MulTipegs®) VS plastic (SmartPeg®) screwdriver. Penguin® RFA Probe held 1 mm from the transducers to register ISQ |
-
•
Higher values of statistical differences recorded using MulTipeg®/Penguin®. MultiPeg® showed higher resonance frequency than SmartPeg®, yet no significant ISQ difference occurred between the implants under the same device.
-
•
All samples recorded high levels of insertion torque and primary stability, but no correlation existed between the two, suggesting that a high insertion torque does not necessarily correspond with a high ISQ value
|
[324] |
