ADHESION IN DENTISTRY Dr Aravind R Kudva ADHESION

ADHESION IN DENTISTRY Dr. Aravind R Kudva

ADHESION Is defined as the state in which two surfaces are held together by interfacial forces which consist of valence forces or interlocking forces or both Is defined as attachment of one substance to another

�Adherend : The surface or substrate to which adhesive is applied �Adhesive: A material that can join substances together, resist separation and transmit loads across the bond

Adhesive Adherend

DENTIN BONDING AGENTS: �Are di-functional or multifunctional organic molecules that contain a reactive group which interacts with dentin and monomer of restorative material

MECHANISM OF ADHESION � 1. Mechanical theory: State that the solidified adhesive interlocks micromechanically with the roughness and irregularities of the surface of the adherend. 2. Adsorption theory: This includes all kinds of chemical bonds between the adhesive and adherend including primary & secondary bonds

�Diffusion theory: � Proposed that adhesion is a result of bonding between mobile molecules. � Polymers from each side of the interface can cross over and react with molecules on other side. � Eventually interface disappears and two parts merge into one.

�Electrostatic theory: �States that an electrical double layer forms at the interface between a metal & a polymer. �The interfacial phenomena to occur, the two materials being joined must be sufficiently close & have intimate contact. �Sufficient wetting of adhesive will occur only if it’s ST is less than Surface free energy of adherend

ADVANTAGES OF ADHESIVE TECHNIQUE � 1) Minimal tooth preparation………… � 2) Reduces microleakage at restoration tooth interface…. . � 3) Better transmission & distribution of functional stresses across restoration tooth interface � 4) Reinforcement of weakened tooth structure � 5) Repair of restoration is possible � 6) Replacement of debonded restoration with little loss of tooth structure……

Requirements of good bonding: (Dental materials and their selection: William J O’ Brien Third edition. Sturdevant. ) 1. Good Wetting; degree of spreading of a liquid drop on a solid surface Low contact angle : Good wetting High contact angle : Poor wetting

� 2. SURFACE ENERGY FOR SUBSTRATE � 3. SURFACE TENSION OF LIQUID � 4. SURFACES JOINED SHOULD BE CLEAN �Liquid with low viscosity, low surface tension, low contact angle & substrate should have high surface energy.

Indications of adhesive dentistry: �Restoring carious and fractured tooth structure, abrasion, erosion, cervical restorations �Indirect resin based restoration. �All ceramic restoration. �Prefabricated/ cast posts. �Ortho brackets. �Perio splints �Pit and fissure sealants. �Re attachment of fractured tooth.

History of dentinal bonding: Oscar Hagger( 1951): GPA DMA. Buonocore: (1955): Acid etching technique ……. Bowen ( 1957) : Development of BISGMA.

Nakabayashi et al( 1975) Hybrid layer Fusayama ( 1979) Concept of total etching and bonding. . Ferrari et al( 1997 - 2003) Development of one bottle bonding systems. Sixth and Seventh generation bonding systems.

Ideal requirements of dentin bonding agents: High bond strength to dentin Provide bond strength to dentin similar to that of enamel Biocompatibility to dental tissue including the pulp Minimize microleakage at the margins of the restorations.

Prevent recurrent caries and marginal staining. Easy to use and minimally technique sensitive. Good shelf life. Be compatible with a wide range of resins. Non toxic and non sensitizing to the operators or patients. Bonding agents should seal the tooth surfaces from oral fluids.

Enamel adhesion: �Bonding to enamel is achieved mainly by micro mechanical retention after acid etching which removes the smear layer and dissolves hydroxy apatite crystals in the outer surface. �The formation of resin tags with enamel surface is the basis.

�Resin tags : 2 types �Macrotag: formed between enamel rod peripheries. (2 -5µ) �Microtag: fine network of tags across the end of each rod where HA are dissolved. �More important & contribute to bond strength….

Macrotags �Microtags

Etching: �Process of increasing surface reactivity by de- mineralising the superficial calcium layer and thus creating the enamel tags. �Enamel etching transforms smooth enamel into irregular enamel with a high surface free energy.

Pattern of enamel etching: �Type I: removal of enamel prism core, prism periphery intact �Type II: Prism periphery removed �Type III: Mixed pattern

Enamel etching patterns

Effect of acid etch on enamel: �Kind of acid used �Acid concentration �Etching time �Form of etchant �Rinse time �Way in which etching is activated– Rubbing, agitation, repeated application �Primary or permanent dentition �Flouridated, demineralised or stained enamel.

Etchants: �INORGANIC ACIDS �Phosphoric Acid 30%-40% �Nitric Acid �ORGANIC ACIDS �Maliec acid �Citric acid �Oxalic acid

Phosphoric acid: �Buonocore suggested 85% PA RECOMMENDED 30 -40% �This is because calcium dissolution & etching depth increases as the conc of PA increases until it reaches 40%. At higher conc, a reverse effect is seen.

�Etching time: �Not less than 15 secs Washing time: 5 -10 secs ETCHING RESULTS IN: 1. Cleanses debris from enamel 2. Produces a complex 3 D microtopography at enamel surface. 3. Increases enamel surface area for bonding 4. Produces micro-pores for resin. 5. Exposes more reactive surface layer thus increasing its wettability

Steps of enamel etching: � 1) oral prophylaxis � 2) Clean & wash the teeth with water � 3) Isolation � 4) Apply acid etch in the form of liquid or gel for 1015 secs � 5)Wash etchant for 5 -10 secs � 6) frosty white appearance on drying � 7) Repeat procedure if contaminated � 8) Apply Bonding agent � 9) Formation of micro & macro tags constitute the fundamental of enamel resin adhesion

Hybrid layer �Defined as structure formed in dental hard tissue due to de-mineralisation of dentinal surface followed by infiltration of monomer & its polymerisation. �It is the zone in which resin of adhesive system micro mechanically interlocks with dentinal collagen.

Tubule wall hybridization Refers to extension of hybrid layer into tubule wall. Hermetically seals pulp dentin complex. Lateral tubule hybridization Refers to formation of tiny hybrid layer into the walls of lateral tubule. This hybrid layer typically surrounds central core of resin called micro resin tag .

Reverse Hybrid layer: Seen when acid etch dentin is treated with Na. OCL. Hybrid layer is surrounded by more inorganic material unlike the normal hybrid layer where collagen is encapsulated by resin. Ghost hybrid layer: Formed due to incorporation of air bubbles at the substrate adhesive interface These micro space are then open to micro leakage.

Resin tag Dentinal tubule Hybrid layer

Composition of dentin bonding agents Etchants Primers Adhesives Initiators and accelerators Fillers

The various acid etchants used are: Organic Maliec acid Tartaric acid Citric acid EDTA Acidic monomers Polymeric Polyacrylic acid Mineral acids Hydrochloric acid Nitric acid Hydrofluoric acid

Primers Also called adhesion promoters. Monomers used is HEMA-HYDROXY ETHYLE METH ACRYLATE

The solvents used in primers Acetone Ethanol water. Acetone – H 2 O Eg: Tenure- quick Acetone- ethanol Eg: All bond 2 ( Bisco) Ethanol- water Eg: Gluma comfort bond Scotchbond

Adhesives Bis GMA, UDMA, TEGDMA, Methacrylated phosphates Initiators and Accelerators Light cured: camphoroquinone and an organic amine. Dual cured bonding agents : catalyst to promote self curing.

Fillers: • Most unfilled • inorganic fillers 0. 5% to 40% by wt. • microfillers, or nanofillers, and submicron glass. Advantages ….

Classification of dentin bonding agents:

I Generation Bonding agents Buonocore : GPA-DMA could bond to HCl etched dentin Bowen 1965 : N- Phenylglycine glycidyl methacrylate( NPG- GMA).

Dentin Bonding Systems Agents used in this generation: NPG-GMA. Glycerophosphoric acid dimethacrylate. ( GPA-DMA). Cyanoacrylates Polyurethanes Commercial product Cervident( S. S White, Lake wood, NJ) First commercially available bonding agent. Cosmic bond( Amalgamated Dental Company) Palakav( Kulzer, USA).

Dentin Bonding Systems II generation bonding agents: 1978, the Clearfil Bond System F( Kuraray, Osaka, Japan) Systems Scotch bond dual cure( 3 M ESPE). Bondlite ( Kerr). Prisma Universal Bond. Mechanism of action: Major Disadvantage : Interaction occurred at the smear layer

Dentin Bonding Systems Third Generation Dentin Adhesives mid to late 1980 s Two approaches : Modification of smear layer to improve its properties Removal of smear layer partially without disturbing the plugs that occluded the dentinal tubules

Dentin Bonding Systems 3 step process Advantages: Better clinical performance. Disadvantages.

Dentin Bonding Systems The agents used were: Scotch bond 2 ( 3 M Dental) Gluma( Bayer/ Miles) Tenure( Den- Mat) Prisma Universal Bond 3( Caulk/ Dentsply), Syntac( Ivoclar Vivadent) XR Bond( Kerr) Clearfil New Bond( Kuraray)

Dentin Bonding Systems Fourth Generation Bonding agents: Total etch concept : Fusayama in 1979

Dentin Bonding Systems Bonding via resin tag formation in the tubules of conditioned dentin. Formation of precipitate on pre treated dentin surfaces followed by chemical or mechanical bonding of resin. Chemical union to either organic or inorganic components of dentin. Hybrid layer : Nakabayashi

3 step total etch 4 Th Generation Etchant + Primer + Adhesive

Dentin Bonding Systems Advantages: Bond strength: 18 Mpa Can bond to mineralized tissue as well as metal, amalgam, composite and porcelain. Disadvantages: Multiple steps: Technique sensitive. Unless the primer and adhesive are applied consecutively, the overlying composite resin will not bond to the surface. light cure to dual cure.

Dentin Bonding Systems Agents used in this generation All bond 2( Bisco Dental) Amalgam- bond( Parkell) Clearfil Liner Bond( Kuraray) Imperva Bond( Shofu Dental) Optibond( Kerr) Scotch bond multipurpose( 3 M Dental)

Dentin Bonding Systems FIFTH GENERATION BONDING AGENTS

3 step total etch 4 Th Generation Etchant + + Primer and adhesive Adhesive 2 step 5 Th Generation

Dentin Bonding Systems Mechanism of action : micromechanical retention by Penetration into partially opened tubules Hybrid layer Chemical interactions using first and second order bonding Moist bonding technique

Dentin Bonding Systems Moist bonding technique use acetone based primer In case surface is dried – rewetting agents

Dentin Bonding Systems Advantages: Good bond strength. Time saving and relatively simpler to use. Some agents have incorporated fluoride and elastomeric components to improve marginal integrity. Disadvantages: Post operative sensitivity (most common in situations that magnify effects of composite polymerization shrinkage. )

Dentin Bonding Systems Fifth Generation adhesives Prime and Bond 2. 1 Prime and Bond NT( Dentsply Caulk, Milford, Delaware. Prime and Bond 2. 0( Dentsply De Trey, Konstanz, Germany) Single Bond( 3 M ESPE) Optibond Solo plus( Kerr Corporation, Orange California) Pq 1(Ultradent products, South Jordan) Excite( Ivoclar Vivadent. Bond 1(Jeneric/Pen

Dentin Bonding Systems

Dentin Bonding Sy tems

Prime and Bond NT Is the successor of Prime bond 2. 1. Contains nanofillers of diameter of 7 micrometers. Stabilize the hybrid layer Additional crosslinkage by penetrating the channels between collagen fibrils to provide nanoretention

Dentin Bonding Systems SIXTH GENERATION BONDING AGENTS.

Sixth Generation Type 1 Etchant + Self etching primer + Primer Adhesive Sixth Generation Type ii Etchant + Primer All in one adhesive + Adhesive

Dentin Bonding Systems Mechanism 2 gen- smear layer modifying 6 th gen- smear layer dissolving

Dentin Bonding Systems Advantages of Sixth Generation Bonding agent: Single dose packaging possible. So less chance of cross infection. Possibility for particle filled adhesive. Low technique sensitivity

Dentin Bonding Systems Disadvantages of sixth Generation Bonding Agents: Less effective bonding of enamel. Initial bond might deteriorate with aging, which could lead to premature failures. Bonding to Sclerotic and caries affected dentin might be problematic May inhibit set of self cure or dual cure resin materials. Insufficient long term research.

Dentin Bonding Systems Type I Two step/ Non rinsing conditioner/ Self etch primer systems: NRC Non Rinse Conditioner( Dentsply De Trey, Konstanz, Germany) followed by Prime and Bond NT( Dentsply) Clearfil SE Bond Clearfil Liner Bond IIV. Tryian( BISCO, Inc, Schaumburg, ) Simplicity( Apex Dental Materials, Inc, Sandwich, IL) Uni. Fil Bond(GC America, Alsip, IL) One. Coat Self-Etching Bond(Coltene Whaledent, Cuyahoga Falls ) Adhe. SE( Ivoclar Vivadent).

Dentin Bonding Systems Type II 6 th Generation Bonding agent : One step/ Self etching adhesives/ All in one systems In reality, many of these are not all in- one systems at all but require premixing of chemical components (Prompt-L-Pop) or the use of chemically activating pellets or brushes that come with the kit (Touch & Bond, Brush & Bond).

Dentin Bonding Systems 6 th Generation Type II. • Prompt L Pop( 3 M) • Touch and Bond ( Parkell) • Brush and Bond( Parkell) • Xeno III( Dentsply Caulk) • One up Bond F( J Morita, Kuraray)

Universal adhesive for composites and compomers Disposable application system – excellent hygiene Prompt L pop: 10 second curing step It has 3 compartments Compartment 1: Containing methacrylated phosphoric acid, esters photoinitiators, stabilizers. Compartment 2: Contains water, complex fluoride and stabilizers. Compartment 3: Has a microbrush.

Features: Single step application Visual confirmation of polymerization. Fluoride releasing A A and B Mixed Polymerization completed

Dentin Bonding Systems Seventh Generation Bonding systems: They are truly all in one self etch adhesives that require no mixing. Eg: I bond( Heraeus Kulzer). G Bond( GC America).

GC s G bond: 4 MET monomer : strong consistent bond to dentin Phosphoric acid ester monomer : Consistent bond to enamel. Nanointeraction technology Non-conventional interface with the dentin – a “Nano Interaction Zone” (NIZ) Forms insoluble calcium compound.

Dentin Bonding Systems Advantages of seventh generation: Fast and easy to use. Disadvantages: Marginal staining and debonding may occur in some of the systems. May not bond durably to enamel. May not be compatible with self cure and dual cure composites. Lack of polymerization. Water trees phenomenon. phase seperation between hydrophilic and hydrophobic components

Dentin Bonding Systems MOIST BONDING VS DRY BONDING Moist dentin Dry dentin

Dentin Bonding Systems Dry Bonding: use the adhesive systems with water based primers Moist Bonding: use the adhesive systems with acetone based primers Azeotrophism How wet or how dry? .

Dentin Bonding Systems

Clinical problems that can decrease bond strength Problem Solution Dentin surface too dry Use moist cotton pellet to rehydrate surface Dentin surface too wet Gently air dry to achieve glistening surface Contamination with saliva and blood Rinse, re etch if contamination is moderate or greater Contamination with caries detector, handpiece lubricant or hemostatic agent Rinse and reetch Contamination by eugenol Avoid eugenol containing provisional materials and temporary cements. Remaining caries affected dentin Remove caries

Surface does not glisten after application of primer Apply additional coats of primer Self cured composite debonds from adhesive Use dual cure bonding agent with self cured composite or resin cement Bonding agent under cured Cure recommended time with properly maintained light curing unit, be sure the bonding agent is compabtible with light curing unit. Recent bleaching procedure Wait one week after bleaching. Flourosed teeth Double the etching time Smooth single surface lesions lack of bonding Create surface roughness and mechanical undercuts