EVOLUTION OF THE CONCEPTS OF IMPLANT ANCHORAGEAHMADSHAMS,NEGARRAMEZANI FATATOUEI,MINASAFARI SAMAN,NEDASHERAFAT,SONIA

INTRODUCTION

IMPLANTS- are relatively inert materials (biomaterials) inserted into the soft and hard tissues of jaws, thereby providing support and retention for dental prostheses

OSSEOINTEGRATIONIt is a process whereby clinically asymptomatic rigid fixation of alloplastic materials is achieved and maintained in bone during functional loading It is a contact established between normal and remodeled bone and an implant surface without the interposition of non-bone or connective tissue.

HISTORY

Weinmann(1956)concept of seal around dental implantsBranemark et el.(1970s)---- research on osseointegrationJames and Kelln(1974)---- investigation of seal phenomenon Reported----

regeneration of gingival epithelium presence of hemidesmosomes oricin-positive deposition presence of connective tissues fibres Lavelle et al.(1981)----- necessity of attached gingiva to adapt to the implant Mckinney et al.(1981-85)---- regeneration of attached gingiva

SEAL FORMATIONThe following series of events occur:-Formation of epithelial cuff/ free gingival margin.Formation of free gingival groove and gingival sulcus.Formation of non-keratinized crevicular epithelium.Zone of epithelial cells at the base of the sulcus.

ROLE OF EPITHELIAL CELLS IN SEAL FORMATIONFormation of basal lamina collagenous structureSecretion of enzyme- Laminin

BIOLOGIC STRUCTURES FORMING BIOLOGIC SEAL Epithelial cell with cell membraneBasal lamina outside cell membrane

Lamina LucidaLamina densaSublamina LucidaHemidesmosomes on cell membrane

Peripheral densitiesPyramidal particlesFine filamentsLinear body

THE IMPLANT-BONE INTERFACEThe relationship between endosseous implants and bone consists of the following mechanisms:-Osseointegration- when the bone is in intimate but not ultra-structural contactFibrosseous integration - in which soft tissues such as fibers and/or cells, are interposed between the two surfacesBiointegration- the benign acceptance of a foreign object by living tissue

CELLULAR BACKGROUND

Conditions for a proper bone response:- Presence of adequate cells Presence of adequate nutrition Presence of adequate stimulus for bone repair

Adequate cells :--Differentiated bone cells---

OsteoblastsOsteoclastsOsteocytesUndifferentiated--- capable of future osteogenic activity

BONE HEALING

Cell to cell contactMatrix contributionPeizoelectric signals

BIOLOGIC MECHANISMS FOR BONE GROWTHOSTEOCONDUCTION- formation of bone by osteoblasts from the margins of the defect on the bone graft material.

OSTEOINDUCTION- involves new bone formation via stimulation of undifferentiated cells to differentiate into osteoblasts.

OSTEOGENESIS- given an adequate blood supply and cellular viability transplanted osteoblasts form new centers of ossification

BIOMATERIALS The various biomaterials are:-1. Metals and Metal Alloys2. Ceramics and Carbons3. Polymers and Composites

1. METAL ALLOYS Metallic biomaterials being used extensively are:- 1. Titanium and alloys of titanium 2. Aluminium 3. Vanadium 4. Precious metals such as gold and platinum and their alloys are less frequently used

1. CERAMICS AND CARBONSThis group includes:-Aluminium oxide( alumina and sapphire)CeramicsCarbon and Carbon-silicon compounds Hydroxyapatite has been proposed as a solid material and as a surface coating.

2. POLYMERS AND COMPOSITESThese include:-Cross-linked polymers such as:- Polymethyl-methacrylate, Silicone rubber Polyethylene

SURFACE MODIFICATIONSPASSIVATION- enhancement of the oxide layer to prevent the release of metallic ions ANODIZATION- passage of electric current through the metal.SURFACE TEXTURING- increases the area to which the bone can bond.ION IMPLANTATION- bombarding the surface of the implant with high-energy ions

FACTORS AFFECTING SUCCESS AND FAILURE OF IMPLANTSImplant BiocompatabilityImplant DesignImplant surfaceImplant BedSurgical TechniqueLoading Conditions

FACTORS

1. IMPLANT BIOCOMPATABILITY---Most accepted- commercially pure titanium, Niobium, Tantalum.Adherent, self repairing, corrosion resistant layer

2. IMPLANT DESIGN Threaded implants- long functioning without clinical problems Unthreaded

3.IMPLANT SURFACE

Smooth surfaceunacceptable bone cell adhesion Micro-irregularities Energy states/ Surface energy

4. STATE OF HOST BED

Previous irradiation Osteoporosis and Alveolar ridge height resorption Heavy smoking

5. SURGICAL TECHNIQUE Technique -Violent- frictional heat Speed of drilling Power used for implant insertion

6. LOADING CONDITIONS

Premature-

-soft tissue anchorage -poor long term function Length of time loading Gradual increase of load

SIGNIFICANCE OF THE DEFINITIONS All the above definitions are HISTOLOGICAL and not CLINICAL. These definitions come into play:- 1. In laboratories with experimental subjects. 2. After implant failure 3. At the time of autopsy

CLINICAL SUCCESS OF IMPLANTS This is when the implant is in clinical service. The success criteria of implants has been determined on the basis of:- LONGEVITY OF IMPLANTS Earlier-- ranged to about 5 years Now-- ranges to around 20 years

CONCLUSION If the dentist keeps these biologic activities in mind during surgical and prosthetic procedures, the bone can be expected to be maintained in a healthy state, thus assuring long term functioning for such dental implants.

THANK YOU ! ! !