1. Dental Liners, Bases, and Bonding Systems
Chapter 44
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2. Chapter 44 Lesson 44.1
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3. Learning Objectives Pronounce, define, and spell the Key Terms.
Discuss how the sensitivity of a tooth determines the type of dental material that is selected for a procedure.
Discuss how and why cavity liners are used in restoring tooth structure.
(Cont’d)
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4. Learning Objectives
(Cont’d)
Apply calcium hydroxide to a prepared tooth surface.
Discuss how and why varnishes are used in restoring tooth structure.
Apply dental varnish to a prepared tooth surface.
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5. Introduction
Dental liners, bases, and bonding systems are a supplemental classification of dental materials that provide additional protection for the health and well-being of the tooth being restored.
Liners and bases can make a big difference in postoperative sensitivity and long-term pulpal prognosis when used appropriately.
Liners and bases are even used in cavity preparations that are small in circumference but deep.
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6. Prepared Tooth Structures
Design of the cavity preparation
Provides strength within the tooth
Helps determine how the tooth will hold the restoration in place
This is different with amalgam, which relies primarily on retentive features such as removing enough tooth structure to cause the opposing walls to slant slightly inward.
In general, the more natural tooth structure that remains, the stronger the tooth will be.
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7. Pulpal Responses Type of Stimulus Example Physical Thermal, electrical
Mechanical occlusion Handpiece, traumatic
Chemical Acid from dental materials
Biologic Bacteria from saliva
The pulp, found inside the tooth, contains the nerve and blood supply that keep the tooth alive and supplied with nutrients.
These are only a few of the stimuli that may trigger an unfavorable response, either reversible or irreversible, in the pulp. Irreversible trauma to the pulp requires endodontic treatment (a root canal) to save the tooth.
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8. Dental Liners
Dental liners provide a thin barrier to protect the pulpal tissue from irritation caused by physical, mechanical, chemical, and biologic elements.
Liners help protect the pulp from irreversible irritation that may lead to endodontic therapy or an extraction.
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9. Calcium Hydroxide Indications for use Application process
Protects the pulp from chemical irritation by way of its sealing ability
Stimulates the production of reparative or secondary dentin
Compatible with all types of restorative materials
Application process
May be an advanced function in your state
Placed directly over the deepest portion of the preparation
Placed only on dentin
Calcium hydroxide’s capacity for stimulating the production of reparative or secondary dentin is unusual among dental materials.
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10. Fig. 44-1 Placement of a liner.
This drawing represents a cross-section of a tooth with its various layers and the preparation in the middle.
As shown, calcium hydroxide is placed over the deepest portion of the pulpal floor, and only on dentin.
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11. Varnish
Varnish is a liquid consisting of one or more resins in an organic solvent applied to the internal preparation structure.
If varnish is indicated, would it be placed before or after placement of calcium hydroxide? (After.)
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12. Varnishes Indications for use*
Sealing dentinal tubules
Reducing leakage around a restoration
Acting as a barrier to protect the tooth from highly acidic cements such as zinc phosphate
* This material is contraindicated in its use under composite resins and glass ionomer restorations.
(Cont’d)
One popular use is placement of a dental varnish such as Copalite throughout the preparation just before amalgam placement.
Note: Dental varnish has a distinct noxious smell that evaporates quickly. Care should be taken to replace the lid as soon as possible after varnish is dispensed.
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13. Varnishes Application process
(Cont’d)
Application process
Applied with the use of a small disposable applicator or a cotton pellet
Thin coating placed on the internal walls, floor, and margin of a cavity preparation
Allowed to air dry
Second application recommended
For the sake of efficiency, the dentist usually applies the varnish while the assistant carefully prepares the amalgam.
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14. Fig. 44-3 Location for placement of cavity varnish.
This drawing reiterates that varnish or sealer is placed over the liner, which is applied first and allowed to set.
As you will see later in the lesson, a base is also sometimes placed after the liner but before the sealer.
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15. Chapter 44 Lesson 44.2
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16. Learning Objectives
Discuss how and why dentin sealers are used in restoring tooth structure.
Apply a dentin sealer to a prepared tooth surface.
Discuss how and why dental bases are used in restoring tooth structure.
Mix and place three types of bases on a prepared tooth surface.
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17. Dentin Sealer Indications for use Application process
Treatment or prevention of hypersensitivity
Instead of a varnish
Sealing of the dentinal tubules
Ideal for use under all indirect restorations
Application process
Use the material sparingly.
Do not allow the material to make contact with soft tissues (HEMA and glutaraldehyde).
Apply the dentin sealer with the use of a cotton-tipped applicator.
Apply the sealer over all areas of exposed dentin.
Dentin sealer is used under restorations as per the listed indications.
Dentin sealer may also be used as a temporary and conservative desensitizer in areas that may not be readily or immediately restored—for example, cervical abfraction or in areas of toothbrush abrasion—instead of a cervical/gingival composite.
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18. Dental Bases
Dental bases provide different types of pulpal protection:
Protective: protects the pulp from a large restoration
Insulating: protects the tooth from thermal shock
Sedative: soothes pulp that has been damaged by decay or irritated by mechanical means.
Recall that for the reasons listed in this slide a base would be applied over a liner (if a liner was indicated) or directly on a moderately deep dentinal floor. The varnish, sealer, or both would then be placed before the final restoration.
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19. Types of Base Materials
Zinc oxide–eugenol (ZOE)
Zinc phosphate
Polycarboxylate
Glass ionomer
Common commercial examples of dental bases include:
Intermediate restorative material (ZOE)
Tenacin (zinc phosphate)
Durelon (polycarboxylate)
Vitrebond (glass ionomer). Glass ionomer is a popular option because it is compatible under composite resins and easy to manipulate and place.
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20. Fig. 44-5 Location for placement of a base.
This diagram shows the proper order of placement of the base over the liner.
The varnish or sealer is placed over the base.
A bonding agent is placed over the base (after etching) if composite resin is to be placed.
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21. Chapter 44 Lesson 44.3
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22. Learning Objectives
Describe the tooth-etching process and its importance in the bonding of tooth and material.
Describe bonding systems and how they provide a better adherence of dental materials to the tooth structure.
Apply etchant material.
Apply a bonding system to the prepared tooth structure.
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23. Dental Bonding
Dental bonding improves retention by creating a micromechanical retention between the tooth structure and the restoration.
Bonding agents allow for the removal of less tooth structure before definitive restoration placement because minimal retentive features are needed.
Direct bonding to the tooth is achieved by way of removal of the smear layer with etchant.
The use of a light helps the operator control the set time of the material.
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24. Enamel Bonding
Enamel bonding is placed directly on the intact enamel surface.
Examples of enamel bonding
Sealants
Bonded orthodontic brackets
Resin‑bonded bridges
Bonded veneers
Sealant material is also held in place by occlusal developmental grooves.
Bonded veneers are an example of an aesthetic option available to an individual who wishes to change the shape, size, and color of the teeth. A very small layer of the facial enamel is removed, followed by an impression that allows the dental laboratory to fabricate a new facial surface in porcelain, which is bonded permanently to the prepared teeth.
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25. Dentin Bonding
Dentin bonding is placed on the prepared dentin for the bonding of a restorative material to tooth structure.
Smear layer
Thin layer of debris
“Nature’s bandage”
Preparing the tooth surface properly with the use of acid etchant for removal of the smear layer before bonding exposes more microscopic surface area, and thus micromechanical retention is also achieved.
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26. Etching Systems
Etching systems are used to remove the smear layer in preparation for bonding.
Supplied as:
Liquid/gel
Maleic acid
Phosphoric acid
Proper isolation of the teeth to be treated is necessary because contact with skin or soft tissues in the mouth will cause a burn, irritation, or both.
The acid etchant is usually 35% phosphoric acid gel, colored (e.g., blue) to make it easier to see where it has been placed and whether it has been completely washed off.
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27. Clinical Application of the Etchant and Bonding Systems
Plaque or debris is removed before the bonding process.
Etchant is applied to remove the smear layer.
The tooth structure is rinsed and dried (avoid overdrying etched teeth).
All surfaces are covered with onding solution.
Too much bonding is better than too little.
Contamination with saliva requires the entire procedure to be redone.  
Allow time for the bonding material to mature before completing the restoration.      
How is plaque removed before bonding?
Note: The fluoride usually found in prophylaxis paste may interfere with proper bonding.
The bonding agent is usually light-cured.
Some practitioners, as well as manufacturers, advocate the application of multiple layers of bonding agent.
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28. Table 44-1 Supplementary Dental Materials and Application in Order of Use.
This table is a simplified guide to how some of the discussed materials may be used in clinical practice.
Often the treatment plan changes once a tooth has actually been opened up and evaluated.
As research in the field of restorative dentistry continues, the methods and materials used will change.
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