Biological considerations of

Dental ImplantDr. Nitika Jain

Implant introduction Implant classification Implant geometry ( Macro design)

◦ Endosseous implants◦ Subperiosteal implants◦ Transmandibular implants

Implant surface characteristics ( micro design)◦ Additive processes◦ Subtractive processes

Hard tissue interface ◦ Stages of bone healing and ossointegration

Soft tissue interface

Contents

Per – Iangvar Branemark 3rd May 1929

Implant :- Any object or material , such as an alloplastic substance or other tissue, which is partially or completely inserted or grafted into the body for therapeutic , diagnostic, prosthetic or experimental purposes.

Dental implant :- A prosthetic device of alloplastic material Implanted into the oral the oral tissues beneath the mucosa, periosteal layer and or within the bone to provide retention and support for a removal or fixed prosthesis.

Introduction

Implantology :- The study or science of placing and restoring dental implants.

Implant surgery :- The phase of implant dentistry concerning the selection, planning, and placement of the implant body and abutment.

Implant prosthodontics :- The phase of prosthodontics concerning the replacement of missing teeth and/or associated structures by restorations that are attached to dental implants

Implant dentistry:- The selection, planning, development, placement, and maintenance of restoration(s) using dental implants.

Implant abutment :- The portion of the dental implant that serves to support and or retain any prosthesis.

Implant prosthesis:- Dental prosthesis such as crown and other fixed dental prostheses, removable dental prostheses as well as maxillofacial prostheses supported and retained in part or whole by dental implants.

CLASSIFICATION OF DENTAL IMPLANTS

1.Based on implant design2.Based on attachment mechanism3.Based on macroscopic body design4.Based on the surface of the implant5.Based on the type of the material

CLASSIFICATION BASED ON IMPLANT DESIGN

Endosseous implants◦ blade like◦ Pins◦ Cylindrical (hollow and solid)◦ Disklike◦ Screw shaped◦ Tapered and screw shaped

Subperiosteal framelike implants Transmandibular implants

Implants geometry ( macrodesign)

Inserted into the jaw bone after mucoperiosteal flap elevation.

Tapped in place in a narrow trench made with a rotary bur.

One or more posts pierced through the mucoperiosteum after suturing of the flaps.

After a few week healing, a FPD is fabricated by a classic method and cemented on top of it.

Endosseous implants – Blade implants

BLADE I.: A flat, blade-shaped end osseous implantwhich derives its support from a horizontal length ofbone. Most commonly made of metal, it can beperforated, smooth, fluted, textured, coated, wedgeshaped, and/or multi-headed.

Three diverging pins were inserted either transgingivally or after reflection of mucoperiosteal flaps in holes drilled by spiral drills.

At the point of convergence, the pins were interconnected with cement to ensure the proper stability because of their divergence.

Pins

Hollow and Full cylindrical

◦ Straumann and co workers introduced hollow cylinders in mid1970s.

◦ Implant stability would benefit from the large bone to implant surfaces provided by means of the hollow geometry.

◦ Holes ( vents ) favour the ingrowth of bone to offer additional fixation.

Cylindrical implants

Full cylindrical implants were used by Kirsch and became available under the name of IMZ .

The long term survival rates were unacceptable, leading to the limited use of this implant type currently.

They are rarely used at present. The concept was developed by Scortecci. It

is based on the lateral introduction into the jaw bone of a pin with a disk on top.

Once introduced into the bone volume, the implant has strong retention against extraction forces.

Disk implants

The most common type of implant is the screw shaped, threaded implant.

A decrease in the interthread distance at the coronal end of the implant has been proposed to enhance the marginal bone level adaptation.

Screw shaped ( tapered ) implants

1. Minimize apical bone fenestration2. Allow for implant placement in narrow

apical sites 3. Amenable to immediate placement

intoanterior extraction socket

Tapered implant design

They are customized according to plaster model derived from an impression of the exposed jawbone, prior to the surgery planned for implant insertion.

They are designed to retain the overdenture.

They are rarely used.

Subperiosteal implants

ENDOSTEAL

BLADE

RAMUS FRAME

ROOT FORM

They were developed to retain the dentures in the edentulous lower jaw.

The implant was applied through submandibular skin incision.

“staple bone” implant developed by Small, consisted of a splint adapted to the lower border of the mandible.

Transmandibular implants

CLASSIFICATION BASED ON ATTACHMENT MECHANISM OF THE IMPLANT

CLASSIFICATION BASED ON MACROSCOPIC BODY DESIGN OF THE IMPLANT

Cylindrical Implant

Threaded implants

Plateau implants

Perforated implants

Solid implantVented implant

Hollow implant

CLASSIFICATION BASED ON THE IMPLANT MATERIAL

CLASSIFICATION BASED ON THE SURFACE OF THE IMPLANT

Biomechanics involved in Implantology includes

Implant surface characteristics micro design

The nature of the biting forces on the

implants

Transferring of the biting forces to the interfacial surfaces

The interfacial tissue reaction

A successfully osseointegrated implant provides a direct and relatively rigid connection of the implant to the bone.

A critical aspect affecting the success or failure of an implant is the manner in which mechanical stresses are transferred from the implant to bone smoothly.

Surface plays an important role in biological interactions.

Surface modifications have been applied to metallic biomaterials in order to improve the◦ Mechanical◦ Chemical◦ Physical

such as ◦ Wear resistance◦ Corrosion resistance◦ Biocompatibility and surface energy, etc.

Micro rough surfaces ◦ Better bone apposition◦ Higher percentage of bone in contact with the

implant◦ Influence the mechanical properties of the

interface◦ Stress distribution ◦ Bone remodelling

Smooth surfaces ◦ Bone resorption ◦ Fibrous connective tissue layer

Additive

•Surface coatings•Carbon, glass, ceramic coating•Hydroxyapatite coating•Ca –P coating•Composite coating•Titanium Nitride coating•Titanium plasma spray coating•Titania film coating

Implant surface characteristics micro design

Increase the functional surface of implant-bone

interface

Effective stress

transfer

Promote bone

apposition

Improved osseointegrat

ion

Surface coatings

The surface of titanium has been modified by ion beam mixing a thin carbon film.

The corrosion resistance and other surface and biological properties were enhanced using carbon plasma immersion ion implantation and deposition.

Reactive plasma spray produces a feasible BAG-coating for Ti-6Al-4V dental implants.

The coating withstands, without any damage , an externally generated tensile stress of 47MPa,and was adequate for load bearing applications.

Carbon, Glass and ceramic coatings

Enhancement of the osteoconductivity of Ti implants is potentially beneficial to patients since it ◦ shortens the treatment time and◦ Increases the initial stability of the implant

HydroxyapatiteTri calcium phosphate

Hydroxy apatite coating

Ca-P coatings are applied to ◦ To combine the strength of the metals with the

bioactivity of Ca-P.◦ Accelerates the bone formation around the implant and

effectively the osseointegration rate

Various technique ◦ Ion beam dynamic mixing technique(IBDM)◦ Radio frequency magnetron sputter◦ Biometric◦ Deposition◦ Electrochemical deposition◦ Plasma spraying

Ca-P coating

BioActive Ca-P◦ Phosphate based glass◦ Hydroxy apatite

TCP – tri calcium phosphate CPP – calcium pyrophosphate

The cells on the coatings expressed higher alkaline phosphatase activity than pure Ti.◦ Suggesting the stimulation of the osteoblastic

activity on the coatings.

Composite coating

Titanium nitride is known for its high surface hardness and mechanical strength.◦ Increasing the corrosion resistance &surface

hardness of the implant surfaces exposed

Titanium nitriding - various methods◦ Gas nitriding◦ Plasma nitriding by plasma diffusion treatment◦ Plasma assisted chemical vapour deposition◦ Pulsed DC reactive magnetron sputtering◦ Closed field unbalanced magnetron sputtering ion

plating

Titanium nitride coatings

Favour the osseointegration of the bone because of the inherent roughness of such coating

Titanium plasma spraying coating

An ion beam assisted sputtering deposition technique has been used to deposit thick and dense TiO2 films on titanium surfaces which are not easily breached and hence improved corrosion protection.

Titania (titanium dioxide) film coating

Subtractive

•Sand blasting•Shot peening and LASER peening•Dual acid etched technique

Cleaning surface contaminants to prior to further operation

Roughening surfaces to increase

effective/functional surface area

Producing beneficial surface compressive

residual stress

Sand blasting

Alumina (Al2O3) Silica ( SiO2)

Similar to sand blasting but has more controlled peening power, intensity, and direction.

It is a cold process in which the surface of a part is bombarded with small spherical media called shot.

Shot- peening and LASER peening

The LASER peening technology is recently developed ◦ Non contact◦ No media◦ Contamination free peening method

High intensity (5 -15GW/cm2)nano second (10-30ns) of LASER light beam (3-5mm width)striking the ablative layer generate a short lived plasma which causes a shock wave to travel into the implant.

The shock waves induces the compressive residual stress that penetrates beneath the surface and strengthens the implant, resulting in improvement in fatigue life and retarding the stress corrosion cracking occurrence.

Dual acid etched technique◦ To produce microtexture rather than macrotexture◦ Enhance the osteoconductive process through the

attachment of fibrin and osteogenic cells, resulting in bone formation directly on the surface of the implant.

◦ Higher adhesion and expression of platelet and extracellular genes, which help in colonization of osteoblasts at the site and promote osseointegration.

Chemical and electrochemical modifications

Sandblasted and acid etched (SLA) method◦ SLA given by BUSER et al, ◦ Sand blasted, large grit, acid etched.

◦ The surface is produced by large grit blasting process followed by acid etching using hydrochloric acid.

Tooth interface VS implant interface

Vs

Hard tissue interfaceStages of bone healing and osseointegration

A, Three-dimensional diagram of the tissue and titanium interrelationship showing an overall view of the intact interfacial zone around the osseointegrated implant. B, Physiologic evolution of the biology of the interface over time.

The term Osseointegration was first used by Prof I-P Branemark. since then it has been used to describe the procedure of bone attachment with titanium. Though lately, the Glossary of Prosthetic Terms (Sixth Edition) lists the terms Osseointegration and osteointegration but recommends the use of the term osseous integration.

Osseointegration

Osseointegration was originally defined as, a direct structural and functional connection between ordered living bone and the surface of a load-carrying implant.◦ Branemark in 1985

A direct on light microscopical level, contact between living bone and implant. ◦ Albrektsson in 1981

A bony attachment with resistance to shear and tensile forces.◦ Steinemann in 1986

Osseointegration

Branemark in 1990, then gave a modified definition of his own – ◦ “A continuing structural and functional

coexistence, possibly in a symbolic manner, between differentiated, adequately remodeling, biologic tissues and strictly defined and controlled synthetic components providing lasting specific clinical functions without initiating rejection mechanism.”

Osseointegration

Defined as direct bone deposition on the implant surface.

Characterized by structural and functional connection between ordered, living bone and the surface of a load-bearing implant.

Compared to as direct fracture healing, in which the fragment ends become united by bone, without intermediate fibrous tissue or fibrocartilage formation.

Osseointegration

Material and surface properties

Primary stability and adequate load

Prerequisites for osseointegration

Material and surface properties◦ Bio inert materials

Titanium◦ Rough surfaces

Improve adhesive strength Favors bone deposition Degree of mechanical interlock

Primary stability and adequate load◦ Requires perfect stability◦ Exact adaptation and compression of the

fragments

incorporation by woven bone formation;• 4

to 6 weeks

adaptation of bone mass to load (lamellar and parallel-fibered bone deposition); and Second month

adaptation of bone structure to load (bone remodeling).Third month

Stages

The first bone tissue formed is woven bone. characterized by a random, felt-like

orientation of its collagen fibrils, numerous, irregularly shaped osteocytes and, at the beginning, a relatively low mineral density.

it grows by forming a scaffold of rods and plates and thus is able to spread out into the surrounding tissue at a relatively rapid rate

Formation of woven bone

(deposition of parallel-fibered and lamellar bone)

lamellar bone, or towards an equally important but less known modification called parallel- fibered bone

◦ Three surfaces qualified for deposition of fibered and lamellar bone Woven bone formed in the first period of OG Pre-existing or pristine bone surface The implant surface

Adaptation of bone mass to load

Woven bone ◦ Deposition of more mature bone on the initially

formed scaffold results in reinforcement and often concentrates on the areas where major forces are transferred from the implant to the surrounding original bone.

Pre – existing or pristine bone◦ The trabeculae become necrotic due to the

temporary interruption of the blood supply at surgery. Reinforcement by a coating with new, viable bone compensates for the loss in bone quality (fatigue), and again may reflect the preferential strain pattern resulting from functional load.

The implant surface◦ Bone deposition in this site increases the bone-

impIant interface and thus enlarges the load-transmitting surface. Extension of the bone-implant interface and reinforcement of pre-existing and initially formed bone compartments are considered to represent an adaptation of the bone mass to load.

(bone remodeling and modeling) Last stage of OG It starts around the third month and, after

several weeks of increasingly high activity, slows down again, but continues for the rest of life.

Remodeling starts with osteoclastic resorption, followed by lamellar bone deposition. Resorption and formation are coupled in space and time.

Adaptation of bone structure to load

The cutting cone advances with a speed of about 50 pm per day, and is followed by a vascular loop, accompanied by perivascular osteoprogenitor cells.

Remodeling in the third stage of osseointegration contributes; to an adaptation of bone structure to load in two ways:◦ It improves bone quality by replacing pre-existing,

necrotic bone and/or initially formed, more primitive woven bone with mature, viable lamellar bone.

◦ It leads to a functional adaptation of the bone structure to load by changing the dimension and orientation of the supporting elements.

six key factors for successful osseointegration:

◦ implant material;◦ implant design;◦ surface quality;◦ prosthetic load;◦ surgical technique;◦ bone health.

Soft tissue interfaces

The healthy soft, keratinized tissues facing teeth and implants frequently have a pink color and a firm consistency. The two tissues have several microscopic features in common. The gingiva as well as the keratinized, peri-implant mucosa is lined by a well-keratinized oral epithelium that is continuous with a junctional epithelium that is about 2 mm long.

The interface between epithelial cells and the titanium surface is characterized by the presence of hemi desmosomes and a basal lamina.

Capillary loops in the C/T under the junctional and sulcular epithelium around implant appear normal

The thickness of the epithelium is 0.5mm

The average direction of the collagen fiber bundles of the gingiva is parallel with the implant.

Even if perpendicular then they are never embedded as in the case of dentogingival and dentoperiosteal fibers around the teeth.

The fiber bundles also have cuff like orientation – soft tissue seal around the implant.

The vascular supply of the peri implant gingival or oral alveolar mucosa is more limited than that around natural teeth.

a

Schematic illustration of the blood supply in the connective tissue cuff surrounding the implant/abutment is scarcer than in the gingival complex around teeth because none originates from a periodontal ligament.

Newman, Takei, Klokkevold, Carranza. Carranza’s Clinical Periodontology, 10th Edition and 11th Edition

Lindhe, Lang, Karring. Clinical Periodontology & Implant Dentistry, 5th Edition.

Carle E. Misch. Contemporary Implant Dentistry. 3rd edition.

PHILLIP’S – SCIENCE OF DENTAL MATERIALS – Kenneth J. Anusavice , Phd ,DMD

Robert K, Schenk & Daniel Buser. Osseointegration: A reality. Perio 2000. Vol 17, 1998, 22-35.

References

Robert