D R R I T E S H S H I W A K O T I

IMPLANT MATERIALS

IMPLANT – is defined as insertion of any object

or a material , which is alloplastic in nature either partially or completely into the body for therapeutic , experimental , diagnostic or prosthetic purpose .

FATHER OF IMPLANT DENTISTRY:

Per Ingvar Branemark

Advantage of Implant

To overcome the drawbacks of removable prostheses

Bone maintenance of height and width

Ideally esthetic tooth positioning

Improved psychological health

Increased stability in chewing

Increased retention

Eliminates need to involve adjacent teeth

Materials used in the fabrication of the implant can be generally classified into two different ways :

1. Chemical point – metals and ceramics

2. Biological point – biodynamic materials : biotolerant , bioinhert , bioactive.

Materials regardless of use fall into four different categories :

1. Metal and metal alloys : metals that are used in implants are titanium , tantalum , and alloys Ti-Al-Va , Co-Cr-Mb , Fe-Co-Ni

2. Ceramics

3. Synthetic polymers

4. Natural materials

Bioinhert materials allow close approximation of bones in their surface leading to contact osteogenesis.

These materials allow formation of new bone in their surface and ion exchange with the tissue leads to the formation of chemical bonding along the interface bonding osteogenesis.

Biotolerant are those that are not necessarily rejected when implanted into the living tissiue.

They are human bone morphogenetic protein-2( rhBMP-2 ) which includes bone formation de nevo.

Biomemtic are tissue interegated engineered materials design to mimic specific biologic processes and help optimize the healing/regenerative response of the host microenviroment.

Bioinhert and bioactive materials are also called osteoconductive meaning that they can act as scaffolds allowing bone growth on their surfaces.

Factors affecting implant biomaterials

1. Mechanical

2. Chemical

3. Electrical and

4. Surface specific properties

Chemical factors:

Corrosion : loss of metallic ions from the surface of the metal to the surrounding enviroment.

General : occurs when the metal is immersed into an electrolyte solution.

Pitting : occurs in an implant with a small surface pit placed in a solution.

Crevice : occurs in the bone-implant interface or an implant device where an overlay or composite type surface exist on metallic substrate in a tissue/fluid environment with minimal surface , little or no oxygen may be present in the crevice.

Surface – specific factors

Event at the bone-implant interface:

The performance of the implant can be classified in

terms of :

1. The response of the host to the implant

2. The behaviour of the material in the host

Material response: The event that occurs immediately upon implantation of metals i.e. Results in release of proteins to the blood from the wound surface and cellular activity in the interfacial region.

Host response: Involves series of cellular and matrix events ideally culminating in tissue healing leading to intimate apposition of the bone to the biomaterials i.e. Osseo integration.

Electrical factors

Physiochemical method:

1. Surface energy

2. Surface charge

3. Surface composition are the three factors that aim to improve the bone implant interface.

Morphologic method :

Alteration in biomaterials surface morphology and roughness have been used to influence the cells and tissue response to the implant.

Biochemical method:

The goal is to immobilize protein, enzyme or peptide on biomaterials for the purpose of inducing specific cell and tissue response.

Mechanical properties

Properties considered are:

1. Modulus of elasticity

2. Tensile strength

3. Compressive strength

4. Elongation and

5. Metallurgy

Classification of implant

1. Based on implant design

2. Based on attachment mechanism

3. Based on macroscopic body design

4. Based on the surface of the implant

5. Based on the type of the material

Classification based on implant design:

1. Endosteal1. Ramus frame

2. Root form

3. Blade form

2. Sub-periosteal

3. Transosteal

4. Intramucosal

Endosteal implant:

A device which is placed into the alveolar bone and/or basal bone of the mandible or maxilla

Transect only one cortical plate

Blade form implant:

It consist of thin plates in the form of blade embedded into the bone

Ramus frame implant:

Horse shoe shaped stainless steel device

Inserted into the mandible from one retromolar pad to the other

It passes through the anterior symphysis area

Root form implant:

Designed to mimic the shape of the tooth

For directional load distribution

Subperiosteal implant

Placed directly beneath the periosteum overlying the bony cortex

Transosteal implant

Other names- Staple bone implant

Mandibular staple implant

Transmandibular implant

Combines the subperiosteal and endostealcomponents

Penetrates both cortical plates

Intramucosal implant

Inserted into the oral mucosa

Mucosa is used as attachment site for the metal inserts

Classification based on attachment mechanism

1. Osseointegration

2. Fibro-integration

Osseo integration:

Direct contact between the bone and the surface of the loaded implant

Described by BRANEMARK

Bio active material that stimulate the formation of bone can also be used

Biological considerations for

osseointegration

Bone implant interface

Bone remodeling

Foreign body reaction

Bone to implant interface

Mechanism of osseointegration

Ultrastructure in osseointegration

Destruction of osseointegration

Soft tissue implant interface

Peri-implant membrane

Disease activity in peri-implant tissue

Neuromuscular system as it relates to the

implant

Osseointegration is defined as a direct bone

anchorage to an implant body which can

provide a foundation to support a prosthesis.

“Direct structural and functional connection between ordered, living bone and

surface of a load carrying implant”.

American Academy of Implant Dentistry defined it as “contact

established without interposition of non bone tissue between

normal remodeled bone and on implant entailing a sustained

transfer and distribution of load from the implant to and within

bone tissue”.

Biological Considerations for Osseointegration

Bone implant interface

When compared to compact bone spongy bone has

less density and hardness is not a stable base for

primary fixture fixation.

In the mandible the spongy bone is more dense than

maxilla.

With primary fixation in compact bone,

osseointegration in the maxilla require a longer

healing period.

Bone remodelling

Osseointegration requires new bone

formation around the fixture. A process

resulting from remodeling within bone

tissue.

Osteoblastic and osteoclastic activity helps

maintain blood calcium without change in

quantity of bone

To maintain a constant level of bone

remodeling there should be proper local

stimulation, crucial levels of thyroid

hormone, calcitonin and vitamin D.

Occlusion or occlusal force stimulus are both

important to optimal bone remodeling

Foreign body reaction

Organization or an antigen antibody reaction

occurs when a foreign body is present in the

body.

This reaction occurs in the presence of a protein

but with implant materials devoid of proteins no

antigen antibody reaction

When titanium is used no foreign body

reaction are seen.

The implant material is an important factor

for Osseo integration to occur.

Biological process of implant osseointegration

The healing process of implant system is

similar to primary bone healing.

Titanium dental implants show three stages

of healing

OSTEOPHYLLIC STAGE

When a implant is placed into the cancellous

marrow space blood is initially present between

implant and bone.

Only a small amount of bone is in contact with

the implant surface; the rest is exposed to

extracellular fluids.

Generalized inflammatory response to the

surgical insult.

By the end of first week, inflammatory cells are

responding to foreign antigens.

Vascular ingrowth from the surrounding vital tissues

begins by third day.

A mature vascular network forms by 3 weeks.

Ossification also begins during the first week and the

initial response observed in the migration of

osteoblasts from the trabacular bone which can be

due to the release of BMP’s.

The osteophyllic phase lasts about 1 month.

OSTEOCONDUCTIVE PHASE

Once they reach the implant, the bone

cells spread along the metal surface laying

down osteoid.

Initially this is an immature connective

tissue matrix and bone deposited is a thin

layer of woven bone called foot plate

Fibro-cartilaginous callus is eventually

remodeled into bone callus.

This process occurs during the next 3

months

Four months after implant placement the

maximum surface area is covered by

bone.

OSTEOADAPTIVE PHASE

The final phase begins approximately 4 months

after implant placement.

Once loaded implants do not gain or loose bone

contact but the foot plates thicken in response

and some reorientation of the vascular pattern

may be seen

Grafted bone integrates to a higher degree than

the natural host bone to the implant.

To achieve optimal results an osseointegration

period of 4 months is recommended for implants

in graft bone and 4 to 8 months for implant

placed in normal bone.

Bioactivity

characteristic of an implant material that allows attachment to

living tissues, whereas a non bioactive material would form a

loosely adherent layer of fibrous tissue at the implant

interface

Bioactive retention is achieved with bioactive

materials such as hydroxyapatite (HA), which

bond directly to bone

Factors influencing Osseointegration

Biomaterial for dental implant

Surface composition and structure

Implant design

Heat

Contamination

Primary stability or initial stability

Bone quality

Epithelial down growth

Loading

Mechanism of Osseointegration

Blood clot (between fixture & bone)

Clot transformed by phagocytic cell (1st to 3rd day)

Procallus formation (containing fibroblasts & phagocytes)

Procallus becomes dense connective tissue (Differentiation of osteoblasts & fibroblasts)

Callus (Osteoblasts on the fixture)

Fibro cartilagenous callus (between fixture & bone)

Bone callus (Penetrates & matures)

Prosthesis attached to the fixtures stimulating bone remodeling

Fibro-integration:

Proposed by Dr.Charles Wiess

Complete encapsulation of the implant with soft tissues

Soft tissue interface could resemble the highly vascular periodontal fibers of natural dentition

Classification based on implant materials

1. Metallic implant

2. Ceramic and ceramic coated

3. Polymer and

4. Carbon compound

Metallic implant:

Most popular material in use today is TITANIUM

Other metallic implants are

stainless steel

cobalt chromium molybdenum alloy

vitallium

Metals and alloys in implants

Dental implants are constructed using metals and alloys. These include titanium , tantalum , and alloys of aluminium , vanadium , cobalt , chromium , molybdenum and nickel.

These materials are generally selected on the basis of their strength.

The precious metals generally used in restoration such as gold, platinum and their alloys are less frequently used as dental implant.

Titanium

Discovered in 1789 by Wilhelm Gregor.

Represents only 6% of the earth crust.

Industrial use started 60 years ago with use in aerospace and defence because of it's light weight, high strength and high melting point.

Used as biomaterials in dental implants ,orthopaedic and cardiovascular applications.

Excellent biocompatibility, corrosion resistance, and desirable physical and mechanical properties.

Dr. Wilhelm Kroll is known as the father of titanium dentistry.

He successfully developed the deoxidation process of titanium tetrachloride through a reduction process with magnesium and sodium.

The result was a titanium sponge that could be melted in an induction casting furnace into a solid alloy and produced in long cast solid bars

General properties of titanium

Melting point is 1680 degree

High tensile strength

Highly ductile

Highly rigidity due to high modulus of elasticity

Low weight

High corrosion resistance

American society for testing materials (ASTM) classified titanium into grades; which vary according to oxygen(0.18-0.40 wt%) iron (0.20-0.50 wt%) and other impurities which includes nitrogen , carbon , and hydrogen.

Grade I is the purest and softest form , and have moderately high tensile strength.

As the grade goes up, the stronger the titanium becomes

Grade V contains aluminum and vanadium along with titanium, making it stronger than grades I-IV

Advantage

Strong Lightweight Corrosion Resistant Cost-efficient Non-toxic Biocompatible (non-toxic AND not rejected by the body) Long-lasting Non-ferromagnetic Osseointegrated (the joining of bone with artificial

implant) Long range availability Flexibility and elasticity rivals that of human bone

Medical grade titanium is used in producing: Pins Bone plates Screws Bars Rods Wires Posts Expandable rib cages Spinal fusion cages Finger and toe replacements Maxio-facial prosthetics

It is used to create a number titanium surgical devices: Surgical forceps Retractors Surgical tweezers Suture instruments Scissors Needle and micro needle holders Dental scalers Dental elevators Dental drills Lasik eye surgery equipment Laser electrodes Vena cava clips

Dental Titanium

Titanium has the ability to fuse together with living bone. This property makes it a huge benefit in the world of dentistry.

Titanium dental implants have become the most widely accepted and successfully used type of implant due to its propensity to osseointegrate.

When bone forming cells attach themselves to the titanium implant, a structural and functional bridge forms between the body’s bone and the newly implanted, foreign object.

Titanium orthodontic braces are also growing in popularity. They are stronger, more secure and lighter than their steel counterparts.

Future of Bio-medical Titanium

It is expected that use within the biomedical industry will only continue to grow for titanium in the coming years. With the baby-boomer demographic continuing to age and our health industry pushing for people to live more active lives, it’s only logical that the medical industry will continue researching new and innovative uses for this popular metal alloy. And with health care reform a current major issue, titanium’s cost-efficiency adds even more appeal to those looking to cut health care costs.

Alfa-bio, Bredent, Nobel Biocare are the most widely used dental implants.

Ceramic

Bioceramics and bioglasses are ceramic materials that are biocompatible Bioceramics are an important subset of biomaterials.

Bioceramics range in biocompatibility from the ceramicoxides, which are inert in the body, to the other extreme of resorbable materials, which are eventually replaced by the materials which they were used to repair.

Bioceramics are used in many types of medical procedures. A primary medical procedures where they are used is as surgical implants.

Though some bioceramics are flexible. The ceramic materials used are not the same as porcelain type ceramic materials.

Rather bioceramics are closely related to either the body's own materials, or are extremely durable metal oxide

Available

1)Specialty steels2) Cobalt base alloys3) Titanium and titanium alloys4) NiTiNOL5) Zirconium alloys

Uses

Ceramics are now commonly used in the medical fields as dental, and bone implants.

Artificial teeth, and bones are relatively commonplace.

Surgical cermets are used regularly. Joint replacements are commonly coated with bioceramicmaterials to reduce wear and inflammatory response.

Other examples of medical uses for bioceramics are in pacemakers, kidney dialysis machines, and respirators.

Advantages

Porous, strong and non-brittle composition

Rapid fibrovascularization

No risk of disease-transmission

Lightweight and easy to insert during surgery

Easy to suture to extra ocular muscles

Effortlessly hand-drilled without crumbling

Non-dissolving

Does not release soluble components

Does not cause excessive tissue inflammation

Types of ceramic coatings

Plasma spraying

Vacuum deposition technique

Sol-gel and dip coating methods

Hot isostatic pressing

Expensive

The potential for contamination

The necessity for removing the inert foil or other encapsulating materials

Polymer and composites: