bio-materials: paper review on bone response to titanium implants

Michelle Calender

Ngozi Aberdeen

Jurinus Lesporis

Larsson et al.

International Journal of Biomaterials

1994

Background• Surface composition includes attributes

such as roughness and surface oxide

thickness.

• Titanium’s surface properties can be varied

systematically by electropolishing and

anodizing.

• Are implant-tissue interactions influenced

by implant surface composition?

Preparation Methods

Electropolishing

Polishing using

electrical current.

• Titanium oxides

dissolve

• methanol, butanol,

and perchloric acid

• 22.5 V

• -30 °C

Anodizing

Adding a layer of

surface oxide using

electrical current.

• Titanium oxides form

protective layer

• acetic acid

• 10 or 80 V

• Room temperature

Groups

Each rabbit received 4 threaded titanium

implants, two in each tibia:

1. Electropolishing

2. Electropolishing and 10 V anodizing

3. Electropolishing and 80 V anodizing

4. None

4 rabbits were examined after 7 weeks

6 rabbits, after 12 weeks

Analysis Method

Morphometry:

• Implants and surrounding tissue examined

under a microscope connected to a computer

• Measured surface oxide thickness and

smoothness

• Calculated contact between implant and

tissues

• Calculated percentage of different tissues

between threads

Modified Implant Surface Topography

Clinical Control Anodized Sample - 10V

Anodized Sample - 80V


Clinical

Control

• Rough surface, having grooves, pits and protrusions

• Deformations are plastically deformed

• Topographical features are less than 10µm in height

• Oxide layer 4nm


Electropolished

• Smooth surface, having small pits

• Topographical features are less than 1µm in height

• Oxide layer 4-5nm


Anodized 10V

• Smooth surface, having pits and porous regions

• Topographical features are approximately 10µm in height

• Oxide layer 21nm


Anodized 80 V:

Smooth (left)

Rough (right)

• Heterogeneous surface, having grooves, pits and protrusions

• Topographical features are approximately10µm in height

• Oxide layer 180nm

Surface CharacteristicsPreparation Composition Oxide

Thickness

Surface Topography Substrate

Microstructure

Oxide Crystallinity

Clinical

Reference

TiO2 + 45-80%

C;

Traces of Ca, S,

Si, P, Cl, Na

4nm Rough, with grooves, pits

and protrusions, ≤10µm

R =29 ±4nm

Plastically deformed,

amorous metal surface

Non-crystalline oxide

Electropolished TiO2 + 55-90%

C;

Traces of Ca, S,

Si, P, Cl, Na

4-5nm Smooth, occasional pits,

≤1µm

R = 2.7 ± 0.9nm

Polycrystalline metal

surface


Electropolished

and Anodized,

10V

TiO2 + 55-70%

C;

Traces of Ca, S,

Si, P, Cl, Na

21nm Smooth, with pits and

porous regions, ~10µm

R = 1.5 ± 1nm


surface


Electropolished

and Anodized,

80V

TiO2 + 34-40%

C;

Traces of Ca, S,

Si, P, Cl, Na

180nm Heterogeneous, with

smooth or porous regions,

~10µm

R = 16 ± 2nm


surface

Crystalline oxide

(anatase)

Bone Response to Modified Implants After Surgery

(Clinical Control and Electropolished)

7 weeks 12 weeks

Bone Response to Modified Implants After Surgery

(Anodized 10V and 80V)

7 weeks 12 weeks

Bone Contact and Area in Threads

• Bone deposition occurred on the cut bone after modification by bone resorption, not directly on implant surface.

• Threads 1 and 2 in cortical portion of implant.

• Threads 3-5 in intramedullary portion of implant.

Bone Contact (7 weeks)

Bone Contact (12 weeks)

Bone Area (7 weeks)

Bone Area (12 weeks)

Bone Contact Results

The data suggests the 80V-anodized sample has the most bone contact and bone area within the threads.

Total Bone Contact Total Bone Area

Discussion: Findings

1. All had a high degree of bone contact, and there was no evidence of soft tissue encapsulation.

Why: for bone apposition the Oxide Layer surface chemical properties is a lot more important than its Thickness & Microstructure.

2. Electropolished implants had the lowest degree of bone contact and intra-thread bone amount.

Why: very smooth surface topography

Discussion: Findings (cntd.)

3. 80V Anodized Implant had faster bone formation

Why: I. Maybe Thicker oxide

II. Surface TopographyBut: Topographical features occurred on 1µm level and cells are only influenced by structures 10 times that.

Discussion: Limitations

• Longer implantation periods are especially

necessary for evaluating the clinical

implications of the results of this study.

• Oxide Microstructure was not looked at in

this study.

bio-materials: paper review on bone response to titanium implants

Health & Medicine