Osseointegration and materials
Minimum Success Criteria for Implant
Factors Influencing Osseointegration, 468
Concept of Osseointegration, 468
Materials Used in Dental Implants, 470
Healing Process in Dental Implants, 473
Mechanism of Bone Augmentation in Dental
Bone Grafts Used in Implant Dentistry, 474
Dental implants provide an excellent option to patients who desire
fixed restorations or in those patients who cannot tolerate removable
prosthesis. The long-term favourable outcome with implant
restorations is well documented.
Minimum success criteria for implant systems
The minimum success criteria proposed by T. Albrektsson, G.A.
Zarb and P. Worthington (1986) are:
• An individual, unattached implant is immobile when tested
• Radiographic examination does not reveal any peri-implant
• After the first year in function, radiographic vertical bone loss is less
• The individual implant performance is characterized by an absence
of signs and symptoms such as pain, infections, neuropathies,
paraesthesia or violation of the inferior dental canal.
• As a minimum, the implant should fulfil the above criteria with a
success rate of 85% at the end of a 5-year observation period and
80% at the end of a 10-year period.
Osseointegration is defined as ‘the apparent direct attachment or
connection of osseous tissue to an inert, alloplastic material without
intervening connective tissues’.
‘The process and resultant apparent direct connection of an exogenous
materials surface and the host bone tissues, without intervening fibrous
connective tissues’. (GPT 8th Ed)
Factors influencing osseointegration
1. Biocompatibility and implant design: Commercially pure titanium
implants are the most commonly used material to establish
• Related material, such as niobium, is used to
produce high degree of osseointegration.
• The implant design influences greatly the initial
• Implant length: Commonly used implant lengths
are between 8 and 15 mm which correspond closely
• Implant diameter: For adequate implant strength at
least 3.25 mm diameter implants are used. Most
commonly used diameter is 4 mm. Implant
diameter rather than length influences the amount
of force distributed to the surrounding bone.
• Implant shape: Implant shapes such as hollow
cylinders, hollow screws, solid cylinders or solid
screws influence the amount of osseointegration
and provide initial stability. Alteration in the size or
pitch of the threads can influence the initial stability
2. Surface characteristics: Degree of roughness influences the
osseointegration. Surface treatment, like grit-blasting, etching, plasma
sprayed hydroxyapatite coating, improves osseointegration by
increasing the bone to implant contact.
3. Bone factors: Quality and quantity of bone greatly influences the
stability of implant during placement.
• Qualities of bone most desirable during placement
of implants are well-formed cortical and densely
trabecular bone with good blood supply. Quality of
bone is influenced by factors such as infection,
smoking or irradiation which decreases the blood
4. Loading factors: Adequate healing period should be given to the
implant before loading. Ideally 6 months for maxilla and 4 months for
5. Prosthetic considerations: Properly planned occlusal loading will
help in increased bone to implant contact and long-term
6. The functional loading condition depends on the:
• Type of occlusal factors: Shallow cuspal inclines and
reduced loading during lateral excursion results in
lesser load transferred to the surrounding bone.
• Loading also depends on the nature of the opposing
• Type of prosthetic reconstruction: It may vary from a
single tooth replacement to full arch reconstruction
or implant supported overdentures.
• Number, location and design of implants: The greater
number of implants will distribute the functional
forces over the larger surface area, thereby reducing
• Patient habits: Any parafunctional habits will
drastically influence the prognosis of the treatment.
• Design and properties of implant connectors: Rigid
connectors which are having passive fit help in
distributing load between the multiple implants
and also provide good splinting.
P.I. Branemark coined the term ‘osseointegration’ in 1977. It means a
direct structural and functional connection between ordered living bone and
the surface of a load carrying implant.
The rationale behind osseointegration was to achieve direct contact
between the bone and the implant without any fibrous tissues
between the two interfaces (Fig. 34-1).
• At the light microscopic level, there is a very close adaptation of the
• At higher magnification detected with the electron microscope,
there is a gap of about 100 nm width between the bone and the
• This gap is occupied by the collagen-rich zone adjacent to the bone
and the amorphous zone adjacent to the implant surface.
• Bone proteoglycans help in initial attachment of the tissues to the
surface of implant (titanium dioxide in case of titanium implants).
• Degree of osseointegration depends on the total implant surface
• Greater osseointegration is observed in cortical bone with good
blood supply than in the cancellous bone.
• The degree of osseointegration increases with time and function.
• During placement of the implant, there should be a good contact
between the bone and the implant surface to ensure adequate
• Blood clot forms at the osteotomy site, which is replaced by bone
• Initial bone trauma will lead to bone resorption which will reduce
the primary stability which was initially achieved.
• After the critical period of 2 weeks, the bone formation takes place
and the level of bone contact and implant stability is enhanced.
• Osseointegration can be considered as a dynamic process where bone
• The degree of osseointegration is influenced by the factors described
• Osseointegrated implant is similar to the ankylosed tooth where
there is absence of mobility and there is no intervening fibrous
connective tissue between the tooth and the bone.
• Greater forces applied to the implant may lead to apical movement
of the bone margins resulting in some loss of osseointegration.
• An undisturbed and unloaded healing phase is recommended for
adequate osseointegration (two-stage implant procedure).
FIGURE 34-1 Osseointegration—bone fills the implant thread
Materials used in dental implants
Classification of materials used in dental implants
On the basis of type of material used
• Cobalt–chromium–molybdenum based
• Carbon and carbon silicone compounds
• Austenitic steel with 18% chromium, 8% nickel and iron–carbon
• Chromium imparts corrosion resistance and nickel helps in stabilizing
• It should not be used in a patient sensitive to nickel.
• Alloy is mostly used in wrought and heat treated form.
• It is not in common use currently; it was used to fabricate ramus
blade, ramus frame, stabilizer pins, etc.
• It has high strength and ductility and thus is resistant to brittle
• It is cheap and easily available.
• Alloy is subjected to crevice and pitting corrosion and care is taken
to preserve the passivating layer.
• Iron-based alloys have galvanic potential and have corrosion
characteristics when interconnected with titanium, cobalt,
zirconium or carbon implant biomaterials.
Cobalt–chromium–molybdenum alloy
• It is used in cast or cast and annealed condition.
• It is used in fabrication of subperiosteal frames.
• It is composed of cobalt 63%, chromium 30% and molybdenum 5%
and in traces carbon, manganese and nickel.
• Cobalt provides continuous phase for basic properties.
• Chromium provides corrosion resistance.
• Molybdenum provides strength and stabilizes the structure.
• Good strength and high modulus of elasticity
• Ductility is least and, therefore, bending should be avoided.
• It is technique sensitive during fabrication.
• It is critical to use all the elements in proper concentration.
• Early implants were made of metal such as tantalum, platinum,
gold, palladium and its alloys.
• Recently tungsten, hafnium and zirconium have been used.
• Gold, platinum and palladium have low strength.
• Gold and platinum are costly and have limited use in dental
• Commercially pure titanium (cp-Ti) is considered the material of
choice for fabricating dental implant because of its predictable
reaction with the biologic environment.
• It consists of 99% titanium and 0.5% oxygen and minor amounts of
impurities such as nitrogen, hydrogen and carbon.
• Titanium is a highly reactive material which oxidises (passivates) on
contact with air or normal tissue fluids to form a passivating layer of
titanium oxide. Since the passivating layer minimizes biocorrosion,
this property is desirable for implant devices.
• With the formation of titanium oxide, titanium or its alloy is highly
corrosion resistant. The titanium oxide layer, nevertheless, releases
titanium ions slowly when it comes in contact with electrolyte such
• When a cut surface of titanium is exposed to atmosphere, a
passivating layer 10 Å forms on the surface within a millisecond.
• Any abrasion or scratch on the surface during placement of implant
repassivates in vivo. The passivating property of titanium and its
alloy is further enhanced by treating it with nitric acid to form a
thick and durable layer on the surface.
• Density of titanium is 4.5 g/cm³ and is, therefore, 40% lighter than
• Modulus of elasticity (97 GN/m²) is one-half of that of steel but is 5–
10 times more than that of compact bone.
• It has a high strength to weight ratio.
• The most common alloy of titanium used in implant dentistry is
titanium–aluminium–vanadium (Ti–Al–V) alloy.
• This alloy contains 90% titanium, 6% aluminium and 4% vanadium
• The mechanical properties of the titanium alloy are better than the
• The passivating layer of titanium oxide has a high dielectric
property which is responsible to make the surface of the implant
more reactive to the biomolecules through the increased
electrostatic forces. It, therefore, helps in osseointegration.
Bioactive materials used in implant dentistry
The most commonly used bioactive materials in implant dentistry are
Ceramic materials can be divided into two types:
1. Bioactive, e.g. hydroxyapatite, bioglass and beta-tricalcium
phosphate; these materials exhibit chemical contact with the host
2. Bioinert ceramics, e.g. aluminium oxide and titanium oxide; these
materials do not bond directly to the bone but are mechanically held
in contact with the host bone.
• The ceramic biomaterials are osteoconductive materials.
• These are alloplastic graft materials.
• These materials are used in augmentation of the resorbed ridges and
reconstruction of the osseous defects.
• These provide a scaffold or matrix to enhance new bone formation.
These materials do not have capacity of its own to develop bone.
• These have excellent biocompatibility.
• These exhibit good compressive strength and poor tensile strength
similar to the property of the bone.
• On account of poor tensile strength, their use is limited to lowstress-bearing regions.
• These are available in different shapes, sizes and textures.
Bioactive materials can be classified as:
• Dense crystalline—least resorption of bone occurs
• Amorphous—faster resorption occurs
• Dense—least resorption occurs
• Macroporous—larger spaces and slower resorption
• Microporous—smaller spaces and faster resorption
• On the basis of pH: Low pH—all CaPO4 compounds resorp rapidly,
whereas at high pH—resorp slowly.
Various biomaterials commonly used are:
• Bovine-derived anorganic bone matrix material (Bio-Oss)
Hydroxyapatite: It is a mineral which is primarily inorganic having
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