Dental Implant Osseointegration

Classify types of Dental implants and discuss the role of surface topography of implants in osseointegration.

Dental Implant Definitions

The dental implant is defined as a prosthetic device made of alloplastic material(s) implanted into the oral tissues beneath the mucosal or periosteal layer on or within the bone to provide retention and support for a fixed or removable dental prosthesis; a substance that is placed upon the jaw bone to support a fixed or removable dental prosthesis.

Osseointegration – The process and resultant apparent direct connection of an exogenous material’s surface and the host bone tissues, without intervening fibrous connective tissue present.

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Classification Of Dental Implants

The implants are classified on the basis of tissue placement, materials, based upon bone attachment, shape, surgical stage, upon angle of insertion and tissue – systemic responses.

Classified according to the tissue engagement as:

Subperiosteal implants: An implant that is placed beneath the periosteum of the bone, it receives its primary bone support by resting on it (unilateral, interdental, total and circumferential)

Transosteal implant/mandibular staple/transmandibur: A dental implant that penetrates both cortical plates and passes through the entire thickness of the alveolar bone

• Endosteal implants: An implant that is present within the bone extending into basal bone for support (screw form, cylinder form and blade form).

Classification based on the degree of roughness, surface treatment and manufacturing process.

Classification Of Dental Implants

Significance of implant surface and osseointegration

• Enhances cellular activity and bone apposition
• The bone-to-implant contact (BIC) is enhanced with improved effects on cell migration, proliferation, biomaterial–tissue interaction
• In the early healing stages the implant surface properties provides ideal biological and chemical properties
• The implant surface chemistry can modify the interactions, protein adsorption and cellular activity
• Surface morphology with defined microstructures enhance stable anchorage, increases the wettability and osteoblast activity

• The expressions of bone-specific differentiation factors for osteoblasts are higher and blood coagulation is better on hydrophilic surfaces.

Endosteal Implants

Implant surfaces

Implant surface roughness is divided, depending on the dimension of the measured surface features into macro, micro- and nano-roughness.

Macro roughness

• Range of millimeters to tens of microns
• Directly relates to implant geometry, with threaded screw and macro porous surface treatments
• The primary implant fixation and long-term mechanical stability can be improved by an appropriate macro-roughness
• The macro-roughness enhances the mechanical interlocking between the implant surface and the surrounding bone.

Micro-roughness
Defined as being in the range of 1–10 μm. This range of roughness maximizes the interlocking between mineralized bone and implant surface.

Nano-roughness
Composed of nano-sized materials with a size range between 1 and 100 nm. They increase the process of bone growth, turnover and remodeling.

Various surface treatments

Additive surface

The implant surfaces are modified with an addition of material that increases the implant surface area and enhances osseointegration. E.g. titanium plasma spraying (TPS) technique and hydroxyapatite coating (HA) technique.

Subtractive surface

Indents the implant surfaces with a suitable medium and thus, increases the implant surface area. E.g. blasting with titanium oxide/aluminum oxide and acid etching.

Based on manufacturing process

Turned surface/machined surface
When the titanium rod is loaded to the machine which turns titanium into screw or cylinder.

Titanium plasma spraying (TPS)
Titanium powder particles are plasma sprayed through a nozzle at a temperatures of around 1500 degrees centigrade under argon gas atmosphere at a velocity 600 m/s that results in 0.04–0.06 mm diameter projections.

Classification Of Dental Implants

Osseointegration Advantage
Primary stability is enhanced and surface area is increased to 5–6 times.

Hydroxyapatite coating (HA)
HA-coated implant has a bioactive surface with increased primary stability due to the greater bone to implant contact area.

Osseointegration Indication
Type 4 bone, fresh extraction sites and newly grafted sites.

Blasting with titanium oxide/aluminum oxide
The implant surface is bombarded with particles of aluminum oxide (Al2O3) or titanium oxide (TiO2) to produce a rough surface with irregular pits and depressions. Blasting with Al2O3 particles of 25–75 µm produces surfaces with roughness values of 1.16–1.20 µm, respectively.

Osseointegration Limitations

Embedded remaining particles interferes with osseointegration hence, resorbable blast medium (RBM), such as hydroxyapatite and calcium phosphate are substituted.

Osseointegration Acid etching

• A mixture of acids like HCL and H2SO4 is used. Other acids used for etching are HF, HNO3and H2O2
• The acid concentration, type of acids, temperature and duration of contact are determining factors in creating ideal surface microstructure.

Osseointegration Combination (SLA)

• The combination of two subtractive techniques, such as sand-blasted large-grit acid etched technique (SLA) is the commonest example of this category
• This surface is produced by a large grit (250–500 µm) blasting process followed by etching with hydrochloric–sulfuric acid.

Osseointegration Objectives

Sand blasting creates surface roughness and acid etching cleans the surfaces producing a micro surface.

Electrochemical oxidized surface

A 3–10 nm coating is made on the implant by electrochemical process which improves the corrosion, wear resistance and increases osseointegration.

Osseointegration Ion implantation

High-energy nitrogen ion or calcium ion are added on to the implant surface using higher surface energy. These treatments are usually done in medical grade instruments to increase hardness, corrosion resistance and wear resistance.

Endosteal Implants

Doped surface
Coating surfaces through sol–gel technique with various types of bone growth factors or other bone-stimulating agents enhance growth of bone and osseointegration.

Osseointegration Disadvantages

Include disintegration of coating during implant placement, plaque retention, greater chances of failure and increased cost.

Other surface coatings

Nanosized hydroxyapatite coated on nanotubular Ti surface promotes osteoblast cell adhesion and deposition of osteoblast.
Oxidation of implant surfaces with chemicals and laser roughening are the other methods.