• Morra et al  found that machined implants display a lower concentration of titanium on the surface and a higher concentration of carbon than sandblasted, acid- etched, or plasma-sprayed surfaces.

• Wear is related to the strength of the material, but also to surface roughness.

• Implants of a roughness of about 1.5 µm (Sa) show stronger bone response than turned (smoother) and plasma-sprayed (rougher).

• Potential drawbacks of roughening the implant surface include greater problems with Peri-implantitis and a greater risk of ionic leakage.

• 1.0–2.0 µm (“moderately rough”) Tioblast, SLA, TiUnite, Frialit, most implants of today.

  • Stronger bone response, tendency to better clinical results than turned implants Many, but not all, designs have only short clinical follow-up _ 2.0 µm (“rough”) Plasma-sprayed titanium, hydroxyapatite-coated implants Positive 5-year documentation reported

  • Increased incidence of Peri-implantitis reported in two studies.

• The relevant way to describe an oral implant surface is by referring to its micrometer-sized irregularities.

• Physical characteristics refer to factors such as surface energy and charge.

• In other words, an oral implant with high surface energy may, at least theoretically, show stronger ossseointegration than implants with a low surface energy.

• It is possible that an initially high surface energy will be immediately changed when the implant is moved from the glow discharge container through the air toward the patient.

• A turned titanium implant, such as the original Brånemark screw, is anchored to bone through in- growth into small irregularities of the implant surface— biomechanical bonding.

• Scientific papers published into the 1980s generally indicated that bone needs a minimum of 50- to 100-µm cavities or pores for proper ingrowth.

• Today, we have sufficient knowledge that irregularities at least down to 1 µm may be invaded by bone, although complete Haversian systems need a larger space.

• The strongest biomechanical bonds are seen to surfaces of a roughness of about 1.5 µm, whereas rougher, plasma-sprayed implants show weaker bone ingrowth.

Biochemical Bonding

• The best definition of the biochemical bonding mode of implant anchorage is: “Bioactivity is the characteristic of an implant material which allows it to form a bond with living tissues.”

• Potential chemical bonding between implant and host tissues was first suggested by Hench et al and referred then to a certain glass-ceramic composition and its reaction to the host tissues.

• Instead, calcium phosphate ceramics (eg, hydroxyapatite [HA]) were launched as potentially bioactive surface coatings for titanium implants.

Calcium phosphate–coated implants.

• As summarized by Legeros, calcium phosphate biomaterials have similarities to bone mineral: They may form bone apatite like mineral or carbonate HA on their surfaces (bioactivity); they are able to promote cellular function, leading to formation of a strong bone–calcium phosphate interface; and they are osteoconductive and may bind bone morphogenetic proteins (BMP) to become osteoinductive.

• Osseotite acid- etched implants (3i) have been claimed to give rise to a particular fibrin retention that allows osteogenic cells to migrate to the implant surface, enabling what Davies 53calls “de novo bone formation.”

Doped Surfaces

• Under this heading are implant surfaces that have been doped with a potentially bone-stimulating agent, such as BMP or other bone growth factors.