BIO-MATERIALS IN IMPLANTSBY, DR.SIDDARTH SAS

Introduction

The restoration of missing teeth is an important aspect of modern dentistry There is a demand for replacing missing teeth for esthetics and functional aspect Conventional methods of restoration includes R.P.D, F.P.D, C.D Each method have their own advantages and disadvantages Removal of Partial Denture one or more times per day inconvenience to young patients (its a major drawback)Bulky, un esthetic, complicate chewing Removable Partial Denture.

F.P.D seems to be more natural and convenient but they need adjacent teeth preparation secondary decay, irreversible pulpitis. Complete Denture

Bulky in nature- major drawback Structural variation of tissue- resorption Instability of denture. Loss of masticatory efficiency.

Implants overcome all this drawbacks.

DENTAL IMPLANTAccording to GPT, 1999 A prosthetic device of alloplastic material(s) implanted into the oral tissues beneath the mucosal and/or periosteal layer and on/or within the bone to provide retention and support for a fixed or a removable prosthesis; a substance that is placed into and/or upon the jaw bone to support a fixed or removable prosthesis. According to GPT, 2005 It is defined as a graft (a) insert which is set firmly / deeply into the alveolar bone (which is prepared to the insertion of crowns) to support a fixed / removable prosthesis.

IMPLANT MATERIALDefinition of implant material It has been accepted that no foreign material placed with in a living body is completely compatible. The only substances that conform completely are those manufactured by the body itself (autogenous) Other substance that is recognized as foreign Initiates some type of reaction host tissue response.

BIO MATERIALDefinition of bio material Any substance other than the drug that can be used for any period of time as part of a system that treats, augments or replaces any tissues, organ, or functions of the body.

Classification of bio materialClassification of biomaterials according to their bioactivity (Reaction) 1. Bio active eg., hydroxyapatite coating an a metallic dental implants 2. Bio inert eg., alumina dental implants 3. Surface active bioglass 4. Bioresorbable

VARIOUS TYPES OF IMPLANTSThe implants may be classified based on their position & design and materials used for it. Classification based on implant position & design and their properties 1. Sub periosteial 1. Unilateral 2. Bilateral 2. Transosteal (or) Staple bone implant (or) Mandibular staple implant (or) Trans mandibular implant 3. Endosteal implant 1. Cylindrical cones (or) thin plates 2. Blade implant 3. Ramus frame implant 4. Root form implant 4. Epithelial implant (or) Sub dermal implant (or) intra mucosal implant.

Classification based on materials used 1. Metallic 1. Titanium 2. Titanium alloy 3. Cobalt chromium 4. Molybdenum 5. Stainless Steel 2. Non metallic 1. Ceramics 2. Carbon Classification based on bio activity Bio active implant Bio inert implant Bio glass implant Bio resorbable implant

How implant getting attached to boneRetention of implant in the bone by two methods. 1. Mechanical Osseointegration 1. Fibroosseous integration 2. Osseous integration 2. Chemical Mechanical Mechanical inter locking between bone and implant Retention may be achieved by etching of the implant surface (or) undercuts in the form of vents, slots, screws etc., No chemical bond between bone and implant This kind of retention seen in inert metals like titanium used. Chemical bonding Achieved by coating the implant surface with bio active material e.g, Tricalcium phosphate, Hydroxy apatite. Chemical bond between ions on the implant surface and the collagen of the bone.

OSSEIOINTEGRATIONOsseiointegration Lattin word Osseious Bone Integration State of being complete whole Definition of osseointegration (According to GPT) 1. The apparent direct attachment connection of ossesous tissue to an inert alloplastic material with out intervening connective tissue. 2. The process and resultant apparent direct connection of an exogenous materials surface and the host bone tissues, with out intervening fibrous connective tissue present 3. The interface between alloplastic material and bone Brane mark 1983 stated A direct bone anchorage to an implant body which can provide foundation support to prosthesis, it has an ability to transmit occlusal forces directly to bone. In 1986 Carisson stated the Direct adaptation of bone implant without any other inter mediate tissue, similar to tooth ankylosis

Ossciointegration - How it takes1. Osteo conduction 2. Surface bone apposition OSTEO CONDUCTION Bone producing cells migrate along side the implant surface through a connective tissue scaffolding (implants surface design) form adjacent to implant. Surface bone apposition active material encouraged microscopic surface ridges the osseointegration can also occur by use of bio stimulate formation of bong along surface of implant. SURFACE BONE A POSITION De no vo bone formation where in a mineralized interfacial matrix is deposited along the implant surface. The surface topography will determine the bond strength of bone to the implant surface.

Mechanisum of osseiointegrationIt is same a normal bone healing primary / secondary bone healing. Primary healing To duplicate primary bone healing surgery should be performed in on healthy bone Free from infection Free from necrotic tissue Area should be perfectly sterilized blood clot

Process of healing Initially blood present between fixture and bone forms

Blood clot is transformed by the phagocytic cells such as P.M.N.L, lymphoid cells and macrophages. Phagocytic activity increases during the times between 1st & 3rd day after surgery

Procallons formation (fibroblasts, fibrous tissue & phagocytes) Procallus becomes dense Connective Tissue and mesenchymal cell differentiate into osteoblasts and fibroblsts callus. Connective Tissue + osteoblasts seen on tissue surface potential to calcify Osteogenic fiber formed by osteoblasts

Dense Connective Tissue forms fibro cartilagenous callus (between fixture and the bone) New bone penetrates and new bone matrix called bone callus. Bone callus 1. Increase density 2. Hardness At this time prosthesis is attached to fixture with the stimulation and bone remodeling. Haversian bone calcifies, becomes dense and homogeneous. Occlusal stress stimulate surrounding bone to model and osseointegrated fixtures can with stand masticating function.

FACTORS AFFECTING OSSEIOINTEGRATION 1. Occlusal load 2. Bio compatibility of material 3. Implant design 4. Implant surface 5. Implant bed (surgical site) 6. Surgical technique 7. Infection control. Bone to implant interface 2 theories 1. Fibrosseous weiss theory 2. Osseo integration (Branemarks theory) Fibrosseous theory States that there is a fibroosseons ligament formed between the implant and the bone and this ligament can be considered as the equivalent of periodontal ligament. Presence of collagen fibers at bone & implant interface Peri implantal ligament with an osteogenic effect Early loading of implant.

Characteristics of osseiointegrated implant1. Direct bone anchorage support fixed prosthesis 2. Surgically designed for full arch prosthesis using 6 fixtures Fornoto denture (or) Fully bone Anchored prosthesis 3. Cantilevered form 2nd pre molar 4. Bilateral cantilevered section are limited to 10 mm on each side (maxilla) 20 mm on each side (mandible)

5mm (min) adjacent to natural teeth Length longer anterior posterior depends on inferior alveolar canal position. Elimination of fulcrum rotations in FPD (using several fixtures shorter fixed segments) Free standing FPD

Soft tissue interface Similar to gingiva around natural teeth Peri implant tissues firmly surround and mechanically attach along the abutment surface J.E. surrounds abutment at crevice C.T. adapts to abutment surface beneath. Hanssion (1963) normal shaped epithelial cells attach to the oxide layer with the glycoprotein layer and no inflammatory cells are found around abutment.

Classification of materialMetals Gold, stainless steel, cr-co alloy, titanium, tantalum etc, Titanium & tantalum most commonly used. Metals with surface coatings Titanium substructure sprayed with - plasma spraying hydroxy apatite, Titanium substructure sprayed with calcium phosphate (CaPo4) ceramic coating Ceramics Bioactive Non reactive Other materials Carbon (vitreous) Porous aluminium silicate Polymers and composites (under evaluation)

STAINLESS STEEL

Iron based alloy (steel) 1.2% carbon Stainless steel 12-30% chromium 3 types (based on composition) Ferritic Martenstic Austenitic steel Austenitic steel (surgical grade) is used here Iron 9120C to 394oC quenched Austenitic steel obtained heated Composition 18 % chromium Corrosion resistance 8% nickel Stabilize austenitic form (may cause allergic reaction) 0.03 to 0.05% carbon hardness (it should not exceed) Properties High strength and ductility (resistant to brittle #) Modulus of elasticity 28* 106 psi

Disadvantages Cant be used in nickel sensitive patients Susceptible to pit and crevice corrosions Direct contact with dissimilar metal crown should be avoided prevent galvanism. Through the mechanical properties are suitable, it is not corrosive resistant to the extent to be used in implant.COBALT CHROMIUM MOLYBDENUM.

Cast and annealed for custom made implant designs. Composition Cobalt 63% continuous phase for bi - phasic properties. corrosion resistance (oxide formation) serve to stabilize the structure 5% Chromium 30%

Molybdenum Carbon traces

hardener

Manganese and nickel traces.

properties Out standing resistance to corrosion Tensile strength 95 .psi Modulus of elasticity 34*106psi It has very low ductility Properly fabricated good bio compatibility Used in sub periosteal frame work. Advantages Resistance to corrosion High modulus of elasticity Long term clinical success Disadvantage Poor ductility of all implant alloys Excessive bending should be avoided # The grater corrosive resistance and tissue compatibility over come by titanium.

TITANIUM ITS ALLOYS(Ti-6Al-4Va)

Most popular implant material using today Pure element with an atomic no 22 Highly reactive Composition pure titanium 99.9% Titanium alloys Titanium 90%, aluminium6%, vanadium 4% Traces of nitrogen, carbon and hydrogen. The titanium is highly reactive metal it oxidizes (passivates) on contact with air/normal tissue fluids. This reactivity is favourable for implant devices. Because it minimizes bio corrosion.

Titanium alloys can be classified as alpha, beta, and alpha beta alloys. Alpha alloy Highest strength best corrosion resistance pure titanium small amounts of nitrogen and oxygen (CpT1) Beta alloy Difficult to manufacture (vanadium + aluminium) not used for implant. Alpha beta alloys Most common alloys consisting of 6% of aluminium 4% of vanadium (T1 & Al64Va) Tensile strength of about 120,000 psi Corrosion resistance

properties Material of choice because of inert, bio compatible nature with excellent resistant corrosion. Density 4.5 gm/cm2 40 % lighter than steel Low specific gravity High heat resistance High strength compatible with S.S Very resistance to corrosion Ability to from stable oxides like Tio2 Titanium more ductility than titanium alloy endosteal blade from implants. High dielectric property osseointegration.

Advantages Osseontegration Biodegradative products from favourable tissue response. High corrosive resistance.Metals with surface coatings

alloy

vanadium

produce

The term bio active bonded interface hydroxyapatitie.

inorganic material that develop an adhered with bone eg., tricalcium phosphate,

The titanium substructures sprayed with plasma spraying, hydroxyapatite Calcium phosphate ceramic coatingPlasma spraying hydroxyapatite

Improves quality of osseointegration

Procedure More ten droplets of titanium in plasma state are bombarded against the implant surface with high velocity at tem. 15000oC Plasma stray will from a layer of 0.04 to 0.05 mm after Under microscopic examination, small inter connected pores are found or plasma spray Advantages Promotes bone growth Improves osseiointegration Disadvantages May disrupt interfacial attachment Ion exchange reaction between the bioactive implant and the surrounding body fluids results in the formation of biologically active carbonate appetite (CHAP) layer on the implant that is chemically and crystallographically equivalent to mineral plasma bone.

Collagen formed is thus directly Anchored onto the apatite - depecting Complete osseo intergration

CERAMICS

1. Bio active eg., hydroxy apatitite 2. Non reactive eg., bioglass, alumina sapphire. They are highly inert Bio compatible Moderately high modulus of elasticity Disadvantage Low ductility Low tensile strength Bio active by hydroxy apatite Calcium phosphate ceramic Natural mineral component of vertebrate of hard tissue It show direct bonding with bone similar to ankylosed tooth As alloplastic material to augment the high of resorbed alveolar ridges.

The major advantage of there ceramic coatings is that they can stimulate the adaptation of bone and they exhibit more bone intimate bone to implant contact compared with metallic surface. Greater bone to implant integration hydroxyapatite coated implants with values.

hydroxyapatite 17.1 % 75.9 % 7 days 3 months

Titanium 1.2% 7 days 45.7% 3 months

BIO GLASS

Surface active highly bio combatable Sio2-CaO-Na2O-P2O5-MgO Developed by L.Hench 1967. Known to form a carbonated hydroxyapatite layer in vivo as a result of their calcium and phosphorous content. Formation of this layer initiated by migration of calcium, phosphate, silica & sodium ions towards tissue as a result of external ph changes. Silica rich gel layer forms on the surface as elements are released and lost.

This results in formation of calcium phosphorus layer that simulates osteoblasts to proliferate. These osteoblasts produce collagen fibrils that become incorporated into the calcium phosphorus layer under later anchored by the calcium phosphorus crystals. Which forms strong bone bioglass interface Bioglass bio active material stimulate the formation or bone This materials often used as grafting materials ridge augmentation or bony defects than as coating materials for metallic implants. Even though they have osteoinductive ability bioglasses are also very brittle, which makes them unsuitable for use as stress bearing implant materials

Fig - 2

Fig - 1

The rationale for coating the hydroxyapatite on metal surface 1. Fast bony adaptation 2. Reduced healing time Advanced bio ceramics Composition similar to biological tissue Chemical bonding implant of bone Modulus of elasticity equal to that of bone Disadvantage Bone tensile & shear strength Non reactive ceramic Well tolerated by bone But not promote bone formation High strength Stiffness Hardness Abutment F.P.D. mouth

Carbon compounds vitreous carbon were developed in 1975 to enhance bio compatibility. Connective tissue interface between implant and bone is comparable to that of periodontal ligament. These implants were not very successful because they did not exhibit long term clinical stability other carbon implants are Pyrolytic carbons Glassy carbons Vapour deposited carbons. Polymers and composites polymeric bio material have been used as implant material as well as surface coating the various polymer which used include. Ultra high molecular weight polymers Poly tetra fluro ethylene Fibre reinforced polymers the major dis advantages with these materials is their low strength, high ductility.