Osseointegration has been discussed in detail in Unit 3 and we will recapitulate its finer aspects.
Definition of Osseointegration
a) From the view of the patient.
An implant fixture is osseointegrated if it provides a stable and apparently immobile support of a prosthesis under functional loads, without pain, inflammation or loosening over the lifetime of the patient.
b) From a view point of macro and microscopic biology and medicine.
Definition of Osseointegration
a) From the view of the patient.
An implant fixture is osseointegrated if it provides a stable and apparently immobile support of a prosthesis under functional loads, without pain, inflammation or loosening over the lifetime of the patient.
b) From a view point of macro and microscopic biology and medicine.
Osseointegration of a fixture in bone is defined as the loose apposition of new and reformed bone in congruence with the fixture, including surface irregularities,so that at light microscopic level, there is no interpositioned connective or fibrous tissue and that a direct structural and functional connection is established, capable of carrying normal physiological loads without excessive deformation and without initiating rejecting mechanism.
c) From a macroscopic biomechanical point of view.
A fixture is osseointegrated if there is no progressive relative motion between the fixture and surrounding living bone marrow under functional levels and types of loading for the entire life of the patient and exhibits deformation of the same order of magnitudes as when the same loads are applied directly to the bone.
d) From a microscopic biophysical point of view
Osseointegration implies that at light microscopic and electron microscopic levels, the identifiable components of tissue within a zone of a fixture surface are identified as normal bone marrow constituents which continuously grade into a normal bone structure surrounding the fixture: that mineralized tissue is found to be in contact with fixture surface over most of the surface within nanometers.
Bone Implant Interface
It consists of remodelled bony tissue. For making it strong implant should not be overloaded during its organization period i.e. soon after placement of implant. If overloading occurs at this phase the remodeling process is disrupted and a poorly differentiated implant bone interface will develop leading to a implant failure.All these definitions indicate there is contact between the implant and bone. It must be realized that there is never 100% bone contact at the implant interface.The range of percentages of the implant surface contacting bone matrix i.e. bone to implant contact (BIC) varies between 10% and 90%. Also, all these definitions indicate there is no connective tissue located between the implant and bone. It is important to note that with titanium, root form implants, the marrow vascular spaces contain connective tissue that should be considered part of bone since it is an integral component of cancellous and woven osseous tissue.
Bone Implant Interface -Interface Phase Development
Three phases have been described in the development of bone implant interface.
1. Stabilization phase
c) From a macroscopic biomechanical point of view.
A fixture is osseointegrated if there is no progressive relative motion between the fixture and surrounding living bone marrow under functional levels and types of loading for the entire life of the patient and exhibits deformation of the same order of magnitudes as when the same loads are applied directly to the bone.
d) From a microscopic biophysical point of view
Osseointegration implies that at light microscopic and electron microscopic levels, the identifiable components of tissue within a zone of a fixture surface are identified as normal bone marrow constituents which continuously grade into a normal bone structure surrounding the fixture: that mineralized tissue is found to be in contact with fixture surface over most of the surface within nanometers.
Bone Implant Interface
It consists of remodelled bony tissue. For making it strong implant should not be overloaded during its organization period i.e. soon after placement of implant. If overloading occurs at this phase the remodeling process is disrupted and a poorly differentiated implant bone interface will develop leading to a implant failure.All these definitions indicate there is contact between the implant and bone. It must be realized that there is never 100% bone contact at the implant interface.The range of percentages of the implant surface contacting bone matrix i.e. bone to implant contact (BIC) varies between 10% and 90%. Also, all these definitions indicate there is no connective tissue located between the implant and bone. It is important to note that with titanium, root form implants, the marrow vascular spaces contain connective tissue that should be considered part of bone since it is an integral component of cancellous and woven osseous tissue.
Bone Implant Interface -Interface Phase Development
Three phases have been described in the development of bone implant interface.
1. Stabilization phase
Subendosteal and subperiosteal calluses form and adhere to implant surface. This bone is low in density (woven bone) and forms rapidly.
2. Strength phase
Once the implant is stabilized process of resorption by osteoclasts begins. Bone formed is stronger (lamellar bone) and is weight bearing.
3. Durability phase
Bone undergoes extensive remodeling and additional strength is developed. With remodeling and proper prosthodontic function the interface bone tends to show very mature osteonal and lamellated bone. Bone remodeling and changes occur continuously to long terms success and can conversely contribute to failure.
Remodeling rate -
Human cortical bone: 2-10% per year depending on site and age of patient.Trabecular bone: Higher turnover rate 20-30% per year.In a study of remodeling, the bone turnover rate was found to be substantially higher within 1mm. of bone-implant interface.
Osseointegration In Immediate Placement Of Implants
In routine procedures, delayed placement of implants is done. However, immediate placement of implants into fresh extraction sites is also possible in select cases.In these cases, except for the apical or the apical- lateral portion of implant, much of metal surface may not be in contact with bony walls of the socket, but injuxtaposition to the surrounding organized clot in the socket which must undergo organization process prior to pre-osseous matrix and bone formation. In humans 4-6 weeks is required for the socket to fill with cancellous bone which undergoes further modeling and stiffening prior to the formation of more lamellated structure.
About 1 mm of cortical bone adjacent to osseous wound undergoes post-surgical necrosis inspite of careful surgical technique which must be replaced with a vital bone.Hardness of bone adjacent to implant is significantly low than bone farther away.There is less microdamage in more compliant bone adjacent to implant than in farther older bone.
Physiologic mechanism of osseointegration
It has been suggested that the physiologic mechanism for maintaining osseous integration is a sustained evolution in remodeling adjacent to bone implant interface.
Factors affecting osseointegration
The success or failure of osseointegration is dependent on the following factors.
a) Occlusal load
b) Biocompatibility of the material
c) Implant surface
d) Implant design
e) Surgical technique
f) Infection
g) Bone density
Occlusal load
Overloading the recognizing bone tissue prematurely will cause failure of osseointegration. A two stage surgery is advised routinely and a second stage surgery is carried out 3-6 months later when osseointegration is complete.
Biocompatibility of materials
Materials available of present are cpTi (commercially pure Titanium) Ti - 6AI - 4V (Titanium - 6 Aluminum - 4 Vanadium), Cp Niobium, Hydroxyapatite (HA).cpTi and its alloy (Ti-6Al-4V) are biocompatible materials and are most commonly used implant materials currently.
Implant design
Most conductive design for osseointegration is root form. They can be threaded, hydroxyapatite coated or not.
Implant surface
A smooth surfaced implant is less prone for osseointegration.
Infection control
Infection especially from periodontium should be avoided. All surgical protocol to avoid infection should be followed.
Bone density
The most important bone property is density which is influenced by factors such as patient age and genetics. Higher density bones have a better success.
2. Strength phase
Once the implant is stabilized process of resorption by osteoclasts begins. Bone formed is stronger (lamellar bone) and is weight bearing.
3. Durability phase
Bone undergoes extensive remodeling and additional strength is developed. With remodeling and proper prosthodontic function the interface bone tends to show very mature osteonal and lamellated bone. Bone remodeling and changes occur continuously to long terms success and can conversely contribute to failure.
Remodeling rate -
Human cortical bone: 2-10% per year depending on site and age of patient.Trabecular bone: Higher turnover rate 20-30% per year.In a study of remodeling, the bone turnover rate was found to be substantially higher within 1mm. of bone-implant interface.
Osseointegration In Immediate Placement Of Implants
In routine procedures, delayed placement of implants is done. However, immediate placement of implants into fresh extraction sites is also possible in select cases.In these cases, except for the apical or the apical- lateral portion of implant, much of metal surface may not be in contact with bony walls of the socket, but injuxtaposition to the surrounding organized clot in the socket which must undergo organization process prior to pre-osseous matrix and bone formation. In humans 4-6 weeks is required for the socket to fill with cancellous bone which undergoes further modeling and stiffening prior to the formation of more lamellated structure.
About 1 mm of cortical bone adjacent to osseous wound undergoes post-surgical necrosis inspite of careful surgical technique which must be replaced with a vital bone.Hardness of bone adjacent to implant is significantly low than bone farther away.There is less microdamage in more compliant bone adjacent to implant than in farther older bone.
Physiologic mechanism of osseointegration
It has been suggested that the physiologic mechanism for maintaining osseous integration is a sustained evolution in remodeling adjacent to bone implant interface.
Factors affecting osseointegration
The success or failure of osseointegration is dependent on the following factors.
a) Occlusal load
b) Biocompatibility of the material
c) Implant surface
d) Implant design
e) Surgical technique
f) Infection
g) Bone density
Occlusal load
Overloading the recognizing bone tissue prematurely will cause failure of osseointegration. A two stage surgery is advised routinely and a second stage surgery is carried out 3-6 months later when osseointegration is complete.
Biocompatibility of materials
Materials available of present are cpTi (commercially pure Titanium) Ti - 6AI - 4V (Titanium - 6 Aluminum - 4 Vanadium), Cp Niobium, Hydroxyapatite (HA).cpTi and its alloy (Ti-6Al-4V) are biocompatible materials and are most commonly used implant materials currently.
Implant design
Most conductive design for osseointegration is root form. They can be threaded, hydroxyapatite coated or not.
Implant surface
A smooth surfaced implant is less prone for osseointegration.
Infection control
Infection especially from periodontium should be avoided. All surgical protocol to avoid infection should be followed.
Bone density
The most important bone property is density which is influenced by factors such as patient age and genetics. Higher density bones have a better success.
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