BONDING TO TOOTH STRUCTURE

Macro-mechanical attachment Chemical bonding Micro-mechanical attachment Interpenetration (Hybrid layer)

Bonding Approaches to Tooth Structure

ADHESIVE BONDING

Clinical Applications

Bonded resin composite restorations.

Bonded amalgam restoration.

Cementing indirect ceramic restorations.

Root canal posts and direct resin core build-ups.

Glass ionomer restoration and cementation.

Bonding of orthodontic brackets.

Application of pits and fissures sealant.

Difficulties

Heterogeneous composition of tooth structure Wet tissues Presence of saliva Tubular nature of the dentin Irregularities of cut enamel and dentin surfaces Presence of debris layer (smear layer)

1. Northwest Dentistry - Journal of the Minnesota Dental Association2. www.answers.com/topic/smear-layer3. www.forp.usp.br/bdj/bdj12(3)/trab13123/t13123.html

ADHESIVE BONDING TO TOOTH ENAMEL

Chemical BondingBoth PAA or phosphates-containing bonding agents can achieve chemical bond to HA

Micro-mechanical retention (Acid etching)

Adhesive Bonding to Tooth Enamel

Benefits of acid etching1. Creating surface micro-irregularities2. Increases the bonding surface area3. Removes surface debris and stains 4. Increase the surface free energy

Types of acids to be used 30-50% phosphoric acid (liquid or gel) 10% Maleic acid 2.5% Nitric acid 18% Hydrochloric acid

www.nordiskadental.se/ana_etchi...composite

Steps of acid etching Application of the nominated acid for 15-60s Rinsing with water-air spray for 15s Air Drying for 15s

Enamel surface should have a white frosted appearance This procedure is then followed with application of liquid adhesive The restorative material (composite) should only applied after hardening

(curing) of the adhesive takes place

priory.com/den/resin.htm

Enamel Bonding Agents Diluted Bis-GMA or TEG-DMA resins. Hydrophobic….. Bond only to dry enamel surfaces New formulations have hydrophilic resins (HEMA) to be used for

both enamel and dentin bonding

ADHESIVE BONDING TO TOOTH DENTIN

Yoshiyama et al., J. Appl. Oral Sci. 2004

Chemical Bonding

Bonding to the HA (Ca++) o NPG-GMA (N-phenyl glycine glycidyl methacrylate)o Polymerizing phosphates (glycerophosphoric acid dimethacrylate)o Poly alkenoic acid (polycarboxylic acid)

Bonding to collageno Glutaraldehyde reacts with collagen forming a charged compounds that

reacts with HEMA molecule.o 4-META (4- methyloxy ethyl trimellitic anhydride) can be used as a

potential coupling agent to collage

Micro-mechanical attachmentRetention of resin adhesive could be achieved to irregular dentin surfaces (inter-tubular dentin) and to the walls of opened dentinal tubules (intra-tubular dentin).

Interpenetration attachmentHydrophilic resin adhesive is required to penetrate the wet collagen. e.g. HEMA , PAA and NPG-GMA (N-phenyl glycerol glucidyl methacrylate)

Dentin Bonding Agents (DBA) should Have both hydrophilic and hydrophobic resin components. oThe hydrophilic part is to displace the dentinal fluids and wet the surface. oThe hydrophobic part is responsible for bonding to composite filling materials.

GCharacteristicsBond strength

Commercial examples

1st- 1 component - Very weak adhesion to dentin

2 MPa- Cervident- Cosmic Bond

2nd - 2 components - Weak adhesion to dentin- Prone to water-degradation

2-8 MPa- Bond Lite- Scotchbond- Dentin Adhesit

3rd - 2 component (primer +adhesive) - Bonding to metal- Reduced sensitivity

8-15 MPa

- Prisma UB- Scotchbond II- Tenure- Gluma- X-R Bond

Development of Dentin Bonding Systems

4th Generation(3 Steps)1. Etchant2. Primer (could be B&C)

3. Adhesive (could be B&C)

1. www.solutions.3m.com.2. www.promedica.de/products/compblcm.htm

Total etch (E&D) Formation of hybrid layer Acceptable bond strength (17-25 MPa)

• Compobond LCM• Scotchbond MP• Syntac

5th Generation (2 Steps)

1. Etchant2. single component

(Primer + Adhesive)

Total etch (E&D) Wet bonding Formation of hybrid layer Acceptable bond strength (20-24 MPa)

• Exite• Single-Bond• one-step

6th Generation (2-3 steps)

1. Self-etch primer(etchant + primer)

2. Adhesive

• Prompt L-Pop• SE Bond• Liner bond

Total etch (E&D) Formation of hybrid layer Acceptable bond strength (18-23 MPa)

7th Generation (1 step) 1. Self-etch Adhesive

• I- Bond• G-Bond• VivaPen

Total etch (E&D) Formation of Nano-hybrid layer Acceptable bond strength (18-25 MPa)