1. Chapter 5
Principles of Bonding

2. Lesson 5.1 Principles of Bonding
Discuss the effects of acid etching on enamel and dentin.
Describe the basic steps of bonding.
Explain the differences between bonding to enamel and bonding to dentin.
Discuss the significance of the smear layer.
Describe “wet” dentin bonding.
Compare total-etch and self-etch bonding techniques.
Explain how the hybrid layer is formed and its importance in bonding to dentin.
Discuss the factors that interfere with good bonding.

3. Lesson 5.1 Principles of Bonding
Discuss the adverse effects of microleakage at restoration margins.
Describe how to bond ceramic veneers.
Describe the bonding of orthodontic brackets.
Describe the bonding of endodontic posts.
Explain the differences in bonding to enamel, dentin, metal, and ceramic.
List the factors that contribute to tooth sensitivity after bonding.
Etch enamel and dentin with phosphoric acid as permitted by state law.
Apply a bonding system to etched enamel and dentin as permitted by state law.

4. Basic Principles of Bonding
Bond or bonding
Adhesion
In dentistry, the term bond, or bonding, is used to describe the process of attaching restorative materials to the tooth by adhesion.
When describing cosmetic restorations, such as porcelain or composite veneers, patients often use the term bonding.
The basic principles of the bonding process involve preparing the surface of the tooth or restoration.
Preparing the tooth surface includes removing decay, plaque, and debris.
The tooth then is etched or conditioned with a 10% to 42% solution of phosphoric acid.
This conditioning removes microns of tooth to provide a rough surface to which bonding can occur.

5. Preparation for Bonding
Bonding to the etched surface
Surface wetting
Bond strength
Durability of the bond
Bonding to an etched surface: When a resin bonding agent or primer is flowed over the etched surface, it penetrates into the microscopic pores. When a resin bonding agent cures, it forms resin tags that adhere to the etched surface of the tooth. The resin bonding agent then will chemically bond to other resins placed over it, such as composite resin.
Primary and secondary bonds: The primary or chemical bond occurs through adhesion when the bonding agent and the composite resin material adhere to each other. The chemical bond is stronger than a secondary or physical bond. An example is adhesion of paint to a metal surface.
Surface wetting: Etching increases the ability of the bonding material to wet the tooth surface by creating a high surface energy. Good wetting increases the contact of the material and the tooth; poor wetting prevents complete contact. For this reason, bonding agents are typically made of a low-viscosity material.
Bond strength: The strength of the bond is determined by the amount of force needed to break the two materials apart. This is accomplished by pulling the two materials apart or by applying force until the bond fails. An enamel bond is typically stronger than a dentinal bond.

6. Enamel Etching Removes a small portion of the surface
Removes the smear layer
Etching times
Suggested times
Permanent teeth
Highly mineralized teeth
Primary
The small surface of the enamel that is removed with etching reduces the enamel rods and opens porosities among the rods. The removal of the smear layer also occurs during etching, and the smear layer is made up of debris on the enamel or dentinal surface that results from the cutting of tooth structure during the cavity preparation. The smear layer comprises bacteria, salivary components, and tooth dust.
Clinical trials show good results in some teeth in as short as 10 seconds of etching. For permanent teeth, the etch time is usually 20 to 30 seconds. Highly mineralized teeth may be more resistant to etching and may require up to 60 seconds of etching. Primary teeth should be etched for longer periods (60 seconds or more), because the enamel has a prism pattern that is not well structured. Etching should take approximately 20 to 60 seconds, depending on the manufacturer’s instructions and the type of procedure to be completed.
From Phillips RW, Moore BK: Synthetic resins. In: Elements of Dental Materials for Dental Hygienists and Dental Assistants, Philadelphia, 1994, Saunders.

7. Enamel Etching Frosty appearance Supplied as a liquid and a gel
Rinsing times
The etched surface should have a frosty appearance when dried. When a cavity preparation involves the etching of both enamel and dentin and the preparation is left slightly moist for wet denting bonding, the frosty appearance of the enamel cannot be determined.
The acid etchant comes as a liquid and a gel. The application of the etchant depends on the form that is being used.
The recommended rinsing times for acid gels is approximately 10 seconds or longer. Rinsing times shorter than 5 seconds may not remove residual silica. Rinsing times for liquid etchants can be shorter – 5 to 10 seconds.

8. Dentin Etching Smear layer Acidic primers Phosphoric acid etching
Moist dentin for bonding
The dentin has a higher water content because of its organic makeup. It also contains collagen and other fluids from the pulp chamber. The smear layer, which is made up of debris on the enamel or dentinal surface resulting from the cutting of tooth structure during cavity preparation, must be removed before the bonding procedure is performed. The smear layer contains plaque, bacteria, pellicle, salivary components, blood, and tooth dust. The smear layer sticks tenaciously to the surface, plugs the openings of the dentinal tubules, and cannot be washed off with use of air-water spray.
Bonding agents that use acidic primers to etch the enamel and dentin penetrate the smear layer and incorporate it into the bonding agent, since there is no rinsing used with these systems.
Etching dentin with phosphoric acid dissolves the smear layer first, and then portions of the hydroxyapatite crystals from the surface of the dentin, creating a porous surface and exposing the meshwork of collagen fibrils that are part of the dentin matrix. This opens the dentinal tubules, which leaves a rough, porous surface.
Dentin has a lower mineral content and needs to be etched for only about 10 seconds. Over-etching leaves a weaker bond.
Wet dentin for bonding is where the acid is removed by rinsing for at least 10 seconds. The excess water is removed by a gentle stream of air, but the dentin surface must be moist to keep the collagen fibrils fluffed up.
Courtesy of Grayson Marshall, University of California School of Dentistry (San Francisco, CA).

21. Adhese Universal with VivaPen: Light-curing dental adhesive
Adhese Universal is a single-component, light-curing universal adhesive for direct and indirect bonding procedures that features compatibility with all etching techniques: self-etch, selective-enamel-etch and total-etch.
                                                            
Adhese Universal is the only universal bonding agent available in the conventional bottle as well as the unique VivaPen® delivery for fast and convenient direct intra-oral application with minimal waste to optimize cost-effectiveness. The VivaPen ensures consistently high bond strength because its internal locking mechanism keeps the material fresh all the way to the last drop.
Key Benefits:
UNIVERSAL APPLICATION – for all bonding and etching techniques
Compatible with direct and indirect bonding procedures Adhese Universal balances hydrophilic and hydrophobic properties into one formulation making it universally compatible for direct and indirect bonding procedures. Its low film thickness (~10 microns) will help ensure accurate seating of indirect restorations.
Compatible with all etching techniques Adhese Universal is well-suited for any etching protocol to ensure optimum results in all situations.
EFFICIENT DELIVERY – up to 190 single-tooth applications per VivaPen
The ergonomic, pen-like design of the VivaPen combined with its angled brush cannula enhances comfort, control and speed during direct intra-oral application while reducing material waste.
The 2 milliliters of adhesive contained in the VivaPen are sufficient for approximately 190 single-tooth applications. Compared to conventional bottle delivery forms, this amounts to almost 3 times more applications per milliliter.
The VivaPen features a built-in locking mechanism that minimizes evaporation of material during storage. This helps to ensure consistently high bond strength from the first to the last drop.
PREDICTABLE RESULTS – high bond strength and virtually no post-operative sensitivity
The water solvent and integrated micro-fillers used in Adhese Universal are designed to enhance penetration into the dentin tubules to stabilize and support the collagen network as well as create the formation of a homogeneous layer with only one layer of adhesive. This results in optimum sealing of the dentinal tubules to prevent movement of dentinal fluid, microleakage and post-operative sensitivity.
Adhese Universal with VivaPen: Light-curing dental adhesive
Adhese Universal is a single-component, light-curing universal adhesive for direct and indirect bonding procedures that features compatibility with all etching techniques: self-etch, selective-enamel-etch and total-etch.
                                                            
Adhese Universal is the only universal bonding agent available in the conventional bottle as well as the unique VivaPen® delivery for fast and convenient direct intra-oral application with minimal waste to optimize cost-effectiveness. The VivaPen ensures consistently high bond strength because its internal locking mechanism keeps the material fresh all the way to the last drop.
Key Benefits:
UNIVERSAL APPLICATION – for all bonding and etching techniques
Compatible with direct and indirect bonding procedures Adhese Universal balances hydrophilic and hydrophobic properties into one formulation making it universally compatible for direct and indirect bonding procedures. Its low film thickness (~10 microns) will help ensure accurate seating of indirect restorations.
Compatible with all etching techniques Adhese Universal is well-suited for any etching protocol to ensure optimum results in all situations.
EFFICIENT DELIVERY – up to 190 single-tooth applications per VivaPen
The ergonomic, pen-like design of the VivaPen combined with its angled brush cannula enhances comfort, control and speed during direct intra-oral application while reducing material waste.
The 2 milliliters of adhesive contained in the VivaPen are sufficient for approximately 190 single-tooth applications. Compared to conventional bottle delivery forms, this amounts to almost 3 times more applications per milliliter.
The VivaPen features a built-in locking mechanism that minimizes evaporation of material during storage. This helps to ensure consistently high bond strength from the first to the last drop.
PREDICTABLE RESULTS – high bond strength and virtually no post-operative sensitivity
The water solvent and integrated micro-fillers used in Adhese Universal are designed to enhance penetration into the dentin tubules to stabilize and support the collagen network as well as create the formation of a homogeneous layer with only one layer of adhesive. This results in optimum sealing of the dentinal tubules to prevent movement of dentinal fluid, microleakage and post-operative sensitivity.

22. Adhese Universal with VivaPen: Light-curing dental adhesive
Adhese Universal is a single-component, light-curing universal adhesive for direct and indirect bonding procedures that features compatibility with all etching techniques: self-etch, selective-enamel-etch and total-etch.
                                                            
Adhese Universal is the only universal bonding agent available in the conventional bottle as well as the unique VivaPen® delivery for fast and convenient direct intra-oral application with minimal waste to optimize cost-effectiveness. The VivaPen ensures consistently high bond strength because its internal locking mechanism keeps the material fresh all the way to the last drop.
Key Benefits:
UNIVERSAL APPLICATION – for all bonding and etching techniques
Compatible with direct and indirect bonding procedures Adhese Universal balances hydrophilic and hydrophobic properties into one formulation making it universally compatible for direct and indirect bonding procedures. Its low film thickness (~10 microns) will help ensure accurate seating of indirect restorations.
Compatible with all etching techniques Adhese Universal is well-suited for any etching protocol to ensure optimum results in all situations.
EFFICIENT DELIVERY – up to 190 single-tooth applications per VivaPen
The ergonomic, pen-like design of the VivaPen combined with its angled brush cannula enhances comfort, control and speed during direct intra-oral application while reducing material waste.
The 2 milliliters of adhesive contained in the VivaPen are sufficient for approximately 190 single-tooth applications. Compared to conventional bottle delivery forms, this amounts to almost 3 times more applications per milliliter.
The VivaPen features a built-in locking mechanism that minimizes evaporation of material during storage. This helps to ensure consistently high bond strength from the first to the last drop.
PREDICTABLE RESULTS – high bond strength and virtually no post-operative sensitivity
The water solvent and integrated micro-fillers used in Adhese Universal are designed to enhance penetration into the dentin tubules to stabilize and support the collagen network as well as create the formation of a homogeneous layer with only one layer of adhesive. This results in optimum sealing of the dentinal tubules to prevent movement of dentinal fluid, microleakage and post-operative sensitivity.

24. Adhese Universal with VivaPen: Light-curing dental adhesive
Adhese Universal is a single-component, light-curing universal adhesive for direct and indirect bonding procedures that features compatibility
with all etching techniques: self-etch, selective-enamel-etch and total-etch.
                                                            
UNIVERSAL APPLICATION – for all bonding and etching techniques
Compatible with direct and indirect bonding procedures Adhese Universal balances hydrophilic and hydrophobic properties into one formulation making it universally compatible for direct and indirect bonding procedures. Its low film thickness (~10 microns) will help ensure accurate seating of indirect restorations.

25. high bond strength and virtually no post-operative sensitivity
The water solvent and integrated micro-fillers used in Adhese Universal are designed to enhance penetration into the dentin tubules to stabilize and support the collagen network as well as create the formation of a homogeneous layer with only one layer of adhesive. This results in optimum sealing of the dentinal tubules to prevent movement of dentinal fluid, microleakage and post-operative sensitivity.

86. Enamel Bonding Enamel bonding resins Single component Resin tags
Bonding agents are low-viscosity resins dissolved in solvents, typically acetone or ethyl alcohol, that penetrate porosities in the tooth surface created by etching.
Bonding of agents for enamel requires only a single component – low-viscosity liquid.
When the resin is cured by a chemical process or by light-activation, it locks into the microscopic spaces and irregularities, producing resin tags. The resin tags secure the resin to the enamel and create a very strong bond. Contaminates on the surface, such as saliva or blood, can dramatically lower the strength of the bond to the enamel. This is the major reason why good isolation is so important.
From Phillips RW, Moore BK: Synthetic resins. In: Elements of Dental Materials for Dental Hygienists and Dental Assistants, Philadelphia, 1994, Saunders.

87. Dentin Bonding Dentin bonding resins Resin primer Adhesive resin
Solvents
Adhesive resin
Bonding agents for dentin are viewed as two types: (1) the resin primer that penetrates etched dentin and enamel and lays down a resin layer and (2) adhesive resin that is applied over the primer. The two resins chemically bond to each other. The initial resin prepares or "primes" the tooth surface, and the second resin chemically bonds to the primer. The primer is placed first and is dried before curing, to remove the solvent and the remaining water.
The first step of bonding to dentin requires the primary to penetrate water on the surface of the tooth. In order for the resin to penetrate through the water, it must be dissolved in a solvent that can penetrate water and carry the resin with it.
Courtesy of Jorge Perdigão, University of Minnesota School of Dentistry (Twin Cities, MN).

88. Bonding Systems History of the development of bonding systems
First generation: 1970s
Second generation: Early 1980s
Third generation: Late 1980s
Fourth and fifth generation: Early 1990s
Total etch
Sixth generation: Late 1990s
Self-etching systems
Seventh generation: Early 2000s
Eighth generation: Not on market
Each generation has consisted of better materials or simpler procedures
The first generation bonding agents are those dentists used in the 1970s. The dentist would etch the enamel with acid and place a self-cured, unfilled bonding resin on the enamel only.
By the late 1970s and early 1980s, both enamel and dentin bonding agents (second generation) were being used, and they were light-cured. The dentin still was not etched. This only allowed bonding to the smear layer of the dentin and resulted in a weak bond.
In third generation bonding systems, the dentin was etched but not for a long enough period and then it was dried. So, bonding resin did not penetrate the dentin surface correctly.
In the early 1990s, etching both enamel and dentin with phosphoric acid (called total etch) was an accepted technique. The fourth and fifth generation systems used primer and bonding resins. The fourth generation is a two bottle system, and the fifth generation is a one bottle system where the primer and bonding resins are combined.
In the later part of the 1990s, the sixth generation systems were called self-etching systems. The primer would etch and prime the tooth at the same time, and the etching with phosphoric acid was not required. These systems had primer and bonding resin in separate bottles.
In the early 2000s, the seventh generation systems were self-etching materials, which were improved so that components are contained in one bottle.
The eighth generation is not on the market. It is anticipated to be a more universal bonding system that is compatible with all light, self, and dual-cured resins.

89. Modes of Cure Three modes of curing are used for resin bonding agents:
Light-cure process
Self-cure process
Dual-cure process
The selection of a resin bonding agent and its mode of cure is dependent on the type of restorative materials being used.

90. Three Main Steps of Bonding Systems
Etching with either phosphoric acid or an acid primer
Priming with hydrophilic monomers in a solvent that penetrates etched surfaces
Bonding with hydrophobic bonding resins to seal etched surfaces and to chemically bond to composite resin or resin luting cements
All bonding systems have three main steps in common.

91. Microleakage Margins of restorations Recurrent decay
Failure of existing restorations
Percolation
Restorations can leak when they are not completely sealed at their margins. Leakage usually occurs at the microscopic level (called microleakage) and permits fluids, bacteria, and debris to enter the cavity preparation. Microleakage can result in recurrent decay and failure of the existing restoration.
Microleakage can be also be caused by shrinkage of composite resins when they cure or from restorations placed without bonding, such as conventional amalgam restorations. When restorative materials expand and contract with temperature variations at a different rate from the tooth structure, percolation can occur, in which fluids and bacteria percolate or flow into and out of the gap at the interface of the restoration and the tooth.

92. Contamination of Bonding Site
Common contaminates
Prevention of contamination
Materials that prevent good bonding
The most common contaminates encountered in the oral cavity are saliva and blood. Isolation of the area being treated is essential, and astringents and hemostatic agents can be used to control bleeding.
If contamination of a newly etched surface occurs, rinse it thoroughly and re-etch for 10 to 15 seconds.
Some dental materials will prevent a bonding agent from adhering to the tooth surface appropriately. Eugenol interferes with the set of resins and will cause a drop in bond strength. Flavoring oils in prophy paste can interfere with bonding. Carbamide and hydrogen peroxide whitening agents can leave residual oxygen in the tooth structure that interferes with the bond.

93. Postoperative Sensitivity
Short duration
Causes
Prevention
Some patients may experience transient tooth sensitivity after a bonded restoration. This usually lasts only a short time from a few hours to a few days.
Common causes of tooth hypersensitivity include the following: (1) Tooth has been overdried (desiccated) during the bonding process, trapping air in the dentinal tubules. (2) The dentin has been overetched and is not adequately sealed with priming and bonding resins. (3) The composite resin restoration is cured in increments that are too large, causing contraction stress on the tooth or microleakage as it pulls away from the cavity preparation.
Less postoperative sensitivity is found with self-etching bonding systems compared to total-etch bonding systems. It is important to carefully follow each manufacturer’s instructions for use to ensure that the dentinal tubules are sealed and postoperative sensitivity is avoided.

94. Clinical Application of Bonding
Bonding of restoration
Ceramic bonding and repair
Metal bonding
Amalgam bonding
Composite resin repair
Orthodontic bracket bonding
Bonding of ceramic veneers
Bonding of endodontic posts
After the initial bonding resin is cured on the tooth, other adhesive bonding resins or resin cements can be used to attach restorations to the tooth by way or resin-to-resin chemical bonds.
Ceramic restorations are retained better if they are bonded to the tooth than if they are merely cemented. Bonding also helps to prevent microleakage. Ceramic restorations chip on occasion and need repair instead of replacement. Techniques have been developed to permit repair of the porcelain in the mouth if the repair will not be placed under heavy chewing forces.
Metal bonding is used to create better retention of the metal to the tooth during the cementation of a restoration. Metal bonding is also used for placement of a composite veneer over metal for cosmetic reasons.
Amalgam bonding is not used frequently because the clinical studies have indicated little difference between a bonded and non-bonded amalgam. The change for microleakage, recurrent decay, and fracture was shown to be the same.
Composite resins may be repaired in certain circumstances. However, the older the composite is, the weaker will be its bond to the new composite.
Orthodontic brackets have replaced bands for orthodontic treatment. Bonding of orthodontic brackets is done with plastic or metal brackets, using adhesive bonding resins that are self-cured, light-cured, or dual-cured. Because the metal or ceramic material will not allow light to reach and cure the resin cement under the bracket directly, the light is cast from all directions of the tooth to cure the resin by light that has passed through the enamel.
Ceramic veneers are a relatively conservative means of achieving anterior esthetics. The total-etch bonding systems are preferred, and the veneer will be bonded to mostly enamel.
Posts are placed within the roots of endodontically treated teeth to retain dental materials used to build up missing tooth structure. Posts may be metal or nonmetal. Posts are bonded with the use of bonding agents and resin cements.
Refer students to Procedures 5-1, 5-2, and 5-3 (pp , in the textbook).

95. Summary
Bonding has a wide variety of uses in the modern dental practice
Bonding systems are placed in two general categories
Careful attention to the manufacturer’s recommendations is required to get good results with any bonding system
The two general categories for bonding agents are total-etch (etch and rinse) and self-etch (no rinse).

96. Questions?