Adhesive Restorative Materials

• The presentation discusses adhesive restorative materials, focusing on the bonding of resin-based materials

Introduction

• The development and use of adhesive materials have revolutionized restorative and preventive dentistry
• Adhesive materials have altered attitudes towards cavity preparation
• Michael Buonocore defined adhesion as a method to increase the adhesion of acrylic filling materials to enamel surfaces

Microleakage

• Microleakage, a major dental problem responsible for secondary caries, can be reduced or eliminated with adhesive materials
• New treatments, like pit and fissure sealing, coverage of stained teeth, and direct bonding of brackets, have grown from adhesive systems

Definition of Cohesion

• Cohesion refers to the bonding between similar materials

Definition of Adhesion

• Adhesion (or bonding) is the force or energy between atoms/molecules at an interface, holding dissimilar phases together

Adherend

• Adherend is the surface or substrate to which the adhesive bonds, which is the tooth structure
• Adhesives act as bonding agents that join substances, resist separation, and transmit loads

Achieving Adhesion

• Intimate contact between the adhesive and adherend must be achieved to produce adhesion

Types of Adhesion: True Adhesion

• True adhesion is caused by primary bonds
• Examples of true adhesion include bonding with glass ionomer cement, zinc polycarboxylate cement, and adhesive resin cement
• Glass ionomer and zinc polycarboxylate cements have COOH groups that chemically bond to tooth structure
• Adhesive resin cements use active groups such as MDP and 4-META for chemical bonding to teeth

Types of Adhesion: Mechanical Interlocking

• Macro-mechanical interlocking occurs by creating undercuts inside the tooth structure, such as with amalgam restorations

Types of Adhesion: Micro-Mechanical Interlocking

• Micro-mechanical interlocking occurs when a liquid flows into pores of a solid surface and hardens, creating a strong bond

Factors Affecting Adhesion

• Wetting is an expression of the attraction between molecules of adhesive and adherend and the ability of a liquid to spread over a solid surface

Contact Angle and Wetting

• Wetting is measured by contact angle; a smaller contact angle indicates higher wetting
• Contact angle (0) is the angle between the liquid surface and the solid surface
• Acute angle (good wetting and adhesion), Vertical angle (very poor wetting, no adhesion), Obtuse angle (no wetting, no adhesion)
• Good wetting is required for good adhesion

Factors Affecting Wetting

• Surface energy of solid surface (adherend)
• Surface tension of the adhesive
• Surface irregularities of the adherend
• Viscosity of the adhesive

Surface Energy

• Surface energy relates to the attraction force between surface atoms of a solid
• Higher surface energy improves wetting
• Cleanliness of the adherend increased surface area for adhesion

Surface Irregularities

• Surface irregularities of the adherend such provide mechanical interlocking with the adhesive

Surface Tension

• Surface tension is the attraction force between the surface atoms of a liquid
• High surface tension reduces wetting

Viscosity of the Adhesive

• The viscosity of the adhesive influences the penetration into surface irregularities
• Higher viscosity lowers wetting

Obstacles for Adhesion to Tooth Structure

• The main problem are the heterogeneous composition of enamel and dentine
• Enamel and dentine are formed from organic and inorganic components
• Enamel differs significantly from dentine in its composition.

Obstacles for Adhesion to Tooth Structure: Debris from Cavity Preparation

• The smear layer consists of tooth and bacterial debris and covers the dentine surface
• Low Surface energy is caused because of no intimate contact

Obstacles for Adhesion to Tooth Structure: Presence of Water

• Water is present in the prepared cavity due to leaching from the dentinal tubules

Obstacles for Adhesion to Tooth Structure: Hydrophobic Bonds

• Ideal adhesive monomers must be both hydrophilic for water compatibility and hydrolytically stable to ensure stable bonds in a moist oral environment

Significance of Enamel

• Enamel consists of 95% mineralized inorganic and 4% organic substance
• 1955 studies show adhesion of acrylic resin to acid etched enamel
• Optimum concentration of phosphoric acid range between 30 to 40% and will obtain better adhesion

Acid-Etch Systems for Bonding to Enamel

• The enamel surface is smooth with little potential for bonding by micromechanical attachment
• Treatment with certain acids modifies the enamel surface
• Standard treatment protocol is use of 37% phosphoric acid for 60 seconds, but studies now indicate 15-20 seconds is adequate and preferred

Over-Etching Effects

• If enamel is etched for more than required time, it results in deeper etch
• Bonding agents does not allow its full penetration into etched enamel, results in 'dead space beyond the bonded area
• When enamel bends, dead space gets exposed to oral fluids, these penetrate and may result in secondary caries or discoloration

Optimal Etch Time and Concentrations

• Usually 37% phosphoric acid is used for 15 to 30 seconds
• If concentration is greater than 50%, then monocalcium phosphate monohydrate get precipitated, and inhibits with adhesion
• If concentration is lower than 30%, dicalcium phosphate mono-hydrate is precipitated, which interfere adhesion
• Deciduous teeth require longer time for etching due to the apron of aprismatic enamel

Mechanism of Adhesion

• Adhesion to tooth structure involves an exchange where inorganic tooth material (hydroxyapatite) is replaced by synthetic resins
• Resin tags are formed that micro-mechanically interlock or interpenetrate with the hard tissue.

Types of Acid Applicators

• Solutions of phosphoric acid > difficult to control when applied
• Gels of phosphoric acid viscous enough to allow controlled placement in the required area
• Acis is usually applied by means of brush and syringe.

Surface After Etching

• Surface of human enamel etched with 37% phosphoric acid the acid of choice for most applications of the acid-etch technique.

Patterns of Etching

• Type 1: involves preferential removal of the enamel prism cores, the prism peripheries remaining intact (most common)
• Type 2: involving preferential removal of the peripheries with the cores being left intact.
• Type 3: contains areas which resemble both type 1 and type 2

Micro-Mechanical Attachment After Acid Etch

• The etched surface is now suitable for micromechanical attachment since it contains small undercuts for resins to gain ingress, set, and mechanically lock

Bonding Agents and Resin Tags

• The bonding agent and low viscosity monomers are spread over the etched enamel surface
• Enamel bonding agents generally contain Bis-GMA or UDMA with TEGDMA, to lower the viscosity
• Due to their low viscosity, the bonding agents are able to rapidly wet and penetrate the clean, dried and conditioned enamel
• Resin tags which form between enamel prisms are the Macrotags.

Micro tags

• Finer Microtags are formed across the end of each rod where individual hydroxyapatite crystals were dissolved
• The formation of resin micro and macrotags within the enamel constitutes the fundamental mechanism of enamel resin adhesion

Factors Affecting Acid-Etch Banding Success

• Time of Etching of 10-60 seconds depending on the tooth structure, (NOW 15-30 sec) Chalky appearance on the treated enamel
• Next is the Washing Stage with copious amounts of water to remove debris for 60 seconds is needed
• There needs to have a Drying Stage, this is critical stage if the enamel is being coated with any material that is hydrophobic.

Resin Flow and Bonding

• Resin from the composite flows into the etched enamel and sets, forming rigid tags typically 25 µm long, which retain the filling

Bonding Resin Types

• Consists of a resin similar to that used in the composite material
• Either Single components which can be activated by light, or a Two fluid resin, one containing initiator, one activator which require mixing before applications

Bonding Interface

• Bonding occurs at the unfilled resin to composite interface
• Surface layers of bond resins which are polymerized by a free radical mechanism will remain soft and unpolymerized, from the effect of inhibiting oxygen.

Shear Bond Strength and Clinical Examples

• The resulting shear bond strength achieved between etched enamel and restorative resins is 16-20 MPa
• Fissure sealants are now widely used to prevent pit and fissure caries, use a Class IV restoration
• Fissure sealants are either chemically activated (require the layer tacky due to air, inhibition of the polymerization wiped away) or Light activated

Fissure Sealant Products

• Some products contain additives such as titanium dioxide in order to improve durability (lightly filled composites)

Fluoride and Effectiveness

• Survival of the sealant and cares of sealant relies on Fluoride properties
• Fluoride containing sealants caries resistance
• Some Resin can also be used to make Veneers which chemically link the material silca, or Cementation to attach any prosthesis

Affecting Effects of Etching

• Various Factors on enamel including the, Type of acid, Concentrations, Chemical, Fluoride and types of dentin being permanently applied

Summary of Acid Etching and Enamel

• Summary: Using 37% phosphoric acid around 15-20 seconds, Liquid or gel, The etching process which creates Micropores, using BISGMA or UDMA to bond to it and it also help the mechanical interlocking of the resin

Bonding to Dentine

• Bonding to dentin has proven to be more difficult and less reliable than enamel, and this because of morphologic and histologic differences of the two
• Enamel is 95% the other 50% which is also the reason why Dentin contains more water content

Dentine

• Since Dentine contains 50% hydroxyapatite + 30% polypeptides the system attachs to both more effective
• Adhesives that make chemical links with reactive groups, such as – NH which are present in dentine proteins > make strong bond with dentine but no appreciable adhesion is observed with enamel

Dentin Structure

• Composed of Dentin, DEJ and Pulp, all parts are important

Three Bottle System

• System includes an, Acid, Primer and Resin which allows great bonding

Dentine

• The surface of exposed dentine need to be etched with the surface to allow a resin to form tags.

Concerns About Etching The System

• This part can possible be very damaging to the part, since it helps pull the dentin fluid up, as the tooth and tubules can resist this.

Smear Layer Removal

• Smear layer is removed when Minerals are removed with water, exposing collagen

Factors Limiting bonding to dentine

• Factors Limiting are always bonding a fluid is always hard since Dentin has a smear layer. The smear layer consists of dentine chips, microorganisms, and the salivary protein and dentin from.

Smear Layer

• A tooth that is not cleansed properly has the chance to be affected by a, A. residual of Debrix collected during the process, and B. This layer is loosely attached to Dentin. As it can consisting of inorganic matter crystals that allow infection

Smear Layer Structure

• When it is put into a Microscopy is Amorphous shape that is granular to the eye, some points which have already been treated

Role of Smear Layer

• The smear Layer can be Advantageous to one point since the body is designed to help reduces the body from any sensitivities and it can keep pathogens away
• Disadvantageous because it incorporates microorganisms and creates a week bond with underlying dentin

Smear Layer with Different Systems

• The Adhesive systems should totally remove the smear layer with help of one other layer to reach bonding
• Modern adeshio Stratagies help on the way with how they Interact of them.
• First Method Etch and rinse for the complete removal
• Second Self Etch-adheshives in how the surface is desvoled, and the 3rd method using "Glass loner" to leave most of it in tact

Dentine Conditioning

• Dentine Conditioning is mainly the process of removing the "smear" layer to the surface.

Conditioners

• Conditioners are the liquids that help with removing the pre treatments of the bonding, like the Smear Layer

Dentine Acid

• 35-37% of Phospric Acid
• 10% Phospric
• 10% Malic
• 10% Citric 3% Ferric Cholire

Pros

• Because most of the acid use is the same, it can be advantageous since we do not need to have other product since are all 35%

Process of Priming

• This process helps and change the whole chemical process that the dentite is, helps remove unwanted oils and help prepare a waterproof space.

Differntal Parts

• They have different Materials to use between each process
• The "Hema" which is what used to bond

Bond Strength

• This process used in the dentite is very good and it allows us to have a 2 point connection system.

Systems

• It enables the aid etching by different components and systems that are used but are highly different and difficult

Hybrid layer/Bonding

• To achieve strength this requires, removing the smear layers and using the "Hybrid Technique" which allows a great bonding power to resin

Systems to Hybrid Formation

• Using Primers and resins or two mixures can allow the surface of dentitite to form the layers from below

A - Total Etch Method

• The method which will involve a strong acidic (Phospic) followed with some rinsing to make a removal.

CAVEX "QUEEN"

• CAVEX Total Etch a "Quadrat" used for Gels as a Conditoner, and Eching
• It cause Irritation

B - Single Use and Advantage

• This process is very fast which can perform 1 step at a time conditioning

"Self Etching" Primer Mehtod

• Method can only really be achevible with a special kind of solution can do both at the same point in

In and in

• "In Some cases you can use more acid to help with the process but you must be very careful since that too can harm the process, best practices just continue with main process"

Extra Acid Problems

• You may not be as effective as some of the acids that have already been used with this process

Classification for Dentin Bonding Systemcs

• Most manufacters put them in different system to discrive bond strength are used to have the dentist understand, like generaters.

Modern Mechimism and Structre

• It always has a really big valus, it also has to be tested and its more liky that if there is a dentine fail that it will show.

Primers

• Also we had to use a dentine primer which allowes enamel dreiness to become lest of an issue of modern systems. and if there is and analogus to the dentine, it can affect the bond.

Enamels

• One of the most well known modern systems with good strength bonds.

Alloys and Ceramics

• Alloys/ceramics are very recent to where the bonding can withstand tooth substance and be able to do direct restorations.

Retainability

• The process of a chemical union can have some affect in the alloys, that can reduce the performance and work load that these things needed.

Modern Powder

• The powder was consists of Quartz and Methacrylite monomers wich with the other mixures made the cement work.

Modern Products

• Some of the most modern powder today are in 2 forms both paste and powder to have easy access and use.

Types and examples

• One of the type of powder that can be used is Polymethacrylate is a liquid mixture that as the surface bond.

Application Examples

• You can bond and amalgam to make one great restoration. repair a break, add support.

Chemically Active Resins

• Most chemicaly Resin will have a Intristic that works like metal and needs the aid to with stand the porcelian and metals.
• These material will be 2 types

phocosphyrlated materials

• These material will be have help with both tooth since it will ahve phoslate with both the metal and the tissue.

4-META

• Helps the teeth chemically reactive but their where comcerns over its safety.