Adhesive technique

ADHESIVE DENTISTRY I. Def.: state, where two surfaces are held together by interfacial forces Basically 2 types: 1. micromechanical irregularities in the surface – anorganic tooth material changes place with bond (resin) 2. chemical Range of indication: esthetic front tooth restorations, direct and indirect fillings: ceramic veneers, all- porcelain adhesive bridges and crowns, preprothetical restorations, orthodontic adhesives

ADHESIVE DENTISTRY II. In operative dentistry this technique is commonly used in resin- based material restorations. Filling materials used in adhesive dentistry: composites, glass- ionomers, hybrid- ionomers, compomers,

PRINCIPLE OF ADHESIVE DENTISTRY I. Tooth structures demineralisation with orthophosphoric acid The walls of a cavity show specific surface pattern after etching with an adequate concentration of acid. (Both dentin and enamel)

Micromorphologic enamel patterns after etching 1. Dissolution of prism cores >microtag 2. Dissolution of peripheral enamel > macrotag 3. mixed form

PRINCIPLE OF ADHESIVE DENTISTRY II. Adhesives can penetrate to the roughness of the etched surface. Both adhesive and the filling material has similar chemical character, so they can chemically bond to each another. Bonding can resist masticatory forces.

PHYSICAL BACKGROUND OF ADHESIVE TECHNIQUES The surface phenomena influence the employement and the adhesion of the adhesive filling materials. Surface phenomena include: Surface energy Wetting Capillary action Adhesion

SURFACE ENERGY- SURFACE TENSION I. Atoms and molecules at the surfaces of liquids and solids posses more energy than those in the interior. Reason: assymmetrical forces. Molecules on the border surface of e.g. air-liquid are in contact with each other and the air molecules. However, in liquid, molecules in the inner parts are only in contact with each other which means a different energetic state. In case of liquids this causes the formation of drops, because liquids tend to form in smallest surfaces ->surface tension.

SURFACE ENERGY- SURFACE TENSION II. In general the higher the surface energy, the higher the bonding strength and smaller the extension and penetration. Importance: adhesive penetration to the etched tooth surface.

WETTING 0° degree contact angle indicates complete wetting. Wetting is defined in terms of the degree of a spreading liquid drop on a solid surface. 0° degree contact angle indicates complete wetting. above 90 degrees indicate poor wetting. Good wetting promotes capillary penetration and adhesion. This is important in the employment of adhesives.

CAPILLARY PENETRATION The surface energy of a liquid creates pressure that drives the liquid into tubules. A liquid with low viscosity, low surface energy and low contact angle ( good wetting ) will penetrate faster than one with opposite combination of properties.

ADHESION Adhesion is the attachement of materials in contact that resist the forces of separation. Types of adhesion: MECHANICAL: depends on mechanical interlocking of the two phases and may include microscopic attachements as in case of resin bonding to etched enamel (bonding agent-enamel) CHEMICAL: relies on chemical bonding between two phases.

ADHESIVES Bonding normally has been conducted in three steps Bonding systems involve an unfilled or lightly filled, liquid acrylic monomer mixture placed onto an acid etched tooth surface. Types: enamel, dentin ( or both ) bonding systems. Employment depends on the type of the system. Bonding normally has been conducted in three steps (etching, priming, bonding ). During the late 1990s, the number of stages reduced by combining the actions in various steps

Development of Bond Systems I. 1st Generation 1956 BUONOCORE development of a surface active comonomer GPDM (glycerophosphoric acid- dimethacrylate) theoratically able to form chemical bonds with Ca ions of dentin 2-3 Mpa bond strength  poor clinical results 2nd Generation 1978 (Clearfil Bond System, Scotchbond) mechanism based on polar interaction between phosphate groups in resin(Bis-GMA or HEMA) (negative) and Ca++ in smear layer 5-6 Mpa  smear layer loosely attached

Development of Bond Systems I. 3rd Generation late 80’s: HEMA (hidroxil-etil-metakrilát) hydroxyethyl methacrylate Not to remove, but modify smear layer Adhesive: un/partially filled resin that can contain primer (HEMA) 3-8MPa 4th Generation : total etch technique, early 90’s: acid application on DENTIN surface 13-30MPa 5th gen. one-step=one-bottle system 1 or 2 layers of bond then light 6th, 7th, 8th gen.

Performing the adhesive technique Light-curing composite material: -take out a small amount of filling material, not more than 2mm thickness (colour, light penetration) from the tube. Close tube immediately to prevent contamination with moisture or ligth. -various colour shades: opaque-dentin; incisal-incisal edge of anterior teeth -the composite layers bond to each other, no need to etch or to use bonding agents in between the composite layers. -always try to light from the direction of tooth material – bonding agent and composite filling material both shrink towards the direction of light.

Finishing and polishing Use fine/ultrafine diamond bur to remove excess filling material and form anatomical fissure system and cusps.

Errors during adhesive technique Isolation, cleaning (blood, liquid from gingival sulcus, moisture from exhaled air – rubber dam!) Poorly contoured or fixed matrice Wedge Errors in etching – too long, too short Overdrying tooth surface Bond should dissolve in equal amounts Wrong colour Air bubbles in filling material Poor lighting, wrong direction, time Check articulation