1. Dental Cements

2. Dental Cements have many different uses

3. Classification of Dental Cements
Dental materials that are routinely used when working with indirect restorations
May be classified into three types according to properties and intended use:
Type I: Luting agents, which include permanent and temporary cements
Type II: Restorative materials, such as glass ionomers
Type III: Liners or bases placed within the cavity preparation
What is a luting agent? (This type of dental material is designed to act as an adhesive to hold an indirect restoration to the tooth structure, or to adhere brackets to the tooth surface during orthodontic treatment.)
What type of restorations can be cemented permanently? (Indirect)
Why would a dentist cement a restoration temporarily? (Answers will vary.)
What are some uses of cements? (Certain cements are routinely used as a permanent adhesive material when working with indirect restorations; another type would be used to restore a tooth; and still others act as a temporary cement.)

4. Permanent Cements
Permanent cement is used for the long‑term cementation of cast restorations such as inlays, crowns, bridges, laminate veneers, and orthodontic fixed appliances
Once prepared in the laboratory, cast restorations are delivered to the dentist for the cementation appointment
A luting agent must have qualities that do not interfere with a proper fit
Most restorations are cemented permanently once they have been fabricated in the laboratory and delivered to the dentist.

5. Casting Ready to Be Cemented
What type of restoration is being cemented? (Answers will vary.)
What tooth is involved? (Supply the number.)

6. Temporary Cements
The temporary cementation of an indirect restoration may be determined if:
The dentist needs to remove the restoration at a later date
The tooth is sensitive or is exhibiting other symptoms that might require removal of the cast restoration
When temporary cementation of provisional coverage is required while the patient waits until the laboratory technician completes the cast restoration
What is provisional coverage? (Provisional coverage is a temporary coverage that is placed on a tooth to protect the tooth until the permanent restoration is ready to be cemented.)

7. Variables Affecting Final Cementation
A number of factors can influence the actual cementation of a luting cement
Cementing errors can be the result of:
Improper mixing technique and time
Humidity
Incorrect temperature of the glass slab
What would be some examples of improper mixing technique? (Not properly incorporating the powder into the liquid, and mixing for too short or too long a period of time)
High humidity can interfere with the setting of zinc oxide-eugenol cements in particular.

8. Mixing Time
Follow the manufacturer’s directions regarding a material’s exact mixing time, working time, and delivery time
Any delay between completion of the mix and seating of the cast restoration will result in the initial setting process, which could cause the casting not to seat properly
Each type of cement has its own mixing time.
The cement becomes thicker as time passes.
If the casting does not seat properly it can lead to an open margin and recurrent caries.

9. Guidelines for Mixing Dental Cements
Before mixing, follow the manufacturer's directions
Determine the use of the cement; then measure out the powder and liquid according to the manufacturer’s instructions
Place the powder and liquid on the glass slab
Divide the powder into increments
Incorporate each powder increment into the liquid; then mix thoroughly
The mixing time per increment will vary according to the type of material and its use
Power scoops vary in size according to the cement product. Be careful to match the correct scoop with the appropriate product.
What are the advantages of using an automix system? (Many types of cements today are supplied in a cartridge where they are automatically mixed as they are expressed onto the pad or directly onto the tooth surface you are working on. The advantages of using an automix system are that it provides an exact measurement of material, easy mix and application, and easy clean-up.)

10. Humidity
Premature exposure to warm temperatures or humidity can result in a loss of water from the liquid or addition of moisture to the powder
Always dispense the powder first, then the liquid, to minimize the loss of water from evaporation
Wait until it is time to mix the material before placing it on the pad
Do not set it out at the beginning of the procedure
Always dispense the powder first, then the liquid, to minimize the loss of water resulting from evaporation.
Always wait to dispense powder and liquid until you are ready to mix them.

11. Powder-to-Liquid Ratio
Incorporating too much or too little powder will alter the consistency of the cement
Fluff the powder in the bottle before dispensing the powder in the measuring scoop
Always hold the bottle or vial upright to ensure drops of consistent size when dispensing the liquid
The bottle with liquid should be inverted straight up-and-down prior to dispensing a drop.

12. Temperature
Specific types of material will have a chemical reaction during the setting stage
Zinc phosphate cement generates heat (an exothermic reaction)
It may be beneficial to cool a glass slab in the refrigerator before mixing the cement
Make sure to thoroughly wipe the slab dry before dispensing the material so not to incorporate any moisture condensation into the material
The glass slab needs to be cool to reduce the exothermic heat of reaction and decrease (slow down) the setting time of some cements, especially zinc phosphate cement.

13. Types of Cement
Selection of cement for a specific procedure requires knowledge of the chemical and physical properties of each particular type of cement
Glass ionomer cement
Composite resin cement
Zinc oxide-eugenol cement
Polycarboxylate cement
Zinc phosphate cement
Glass ionomer cement releases fluoride.
Composite resin cement is very strong and is used to cement porcelain veneers.
Zinc oxide-eugenol is often referred to as ZOE. It soothes pain.
Polycarboxylate cement is kind to the pulp.
Zinc phosphate cement is the oldest cement. It is very strong but the mixing procedure is complicated.

14. Glass Ionomer Cement
One of the most versatile types of cement used in dentistry
A hybrid of silicate and polycarboxylate cements
Adheres to enamel, dentin, and metallic materials
Adheres to enamel, dentin, and metallic materials.

15. Glass Ionomer Cement
Supplied in special formulations according to their use:
Type I
For the cementation of metal restorations and direct‑bonded orthodontic brackets
Type II
Designed for restoring areas of erosion near the gingiva
Type III
Used as a liner and dentin bonding agent
Available in self-curing and light-curing formulas.

16. Advantages of Glass Ionomer
The slow release of fluoride from this powder aids in inhibiting recurrent decay
Causes less trauma or shock to the pulp than is caused by many other types of cements
Has a low solubility in the mouth
Adheres to a slightly moist tooth surface
Has a very thin film thickness, which is excellent for ease of seating a casting
Can be formulated for use as a dentin substitute or base material
If glass ionomer is light-cured, what additional equipment will need to be used? (Answers will vary.)

17. Chemical Makeup of Glass Ionomer Cement
Liquid: polyacrylic acid copolymer and water
Powder: calcium fluoroaluminosilicate glass with barium glass
What is the benefit of adding fluoride to the powder of glass ionomer cement? (It helps prevent recurrent caries around the margins of the restoration.)

18. Application of Glass Ionomer
Available as a self-curing or light-cured formula
Supplied in bottles of powder and liquid, which can be mixed manually on a paper pad or cool, dry glass slab
Also supplied in premeasured capsules which are triturated and expressed through a dispenser.
Refer students to Procedure 45-1 (p. 773) for more information on the application of glass ionomer.
Will a cool glass slab decrease or increase the working time? (Answers will vary.)

19. Premeasured Capsules of Glass Ionomer Permanent Cement
Advantages of capsules:
Convenience
Decreased mixing time
Consistent mixes because of controlled ratios
What additional equipment will need to be used for capsules? (A dispenser will be used.)
From Hatrick CD, Eakle WS, Bird WF: Dental materials: clinical applications for dental assistants and dental hygienists, ed 2, St Louis, 2011, Saunders.

20. Composite Resin Cement
A newer classification of cement material designed for:
Cementation of ceramic or porcelain inlays, onlays, crowns, and bridges
Cementation of ceramic veneers
Direct bonding of orthodontic brackets
Cementation of metal-based crowns and bridges
Is etching necessary? (Answers will vary.)

21. Chemical Makeup of Composite Resin Cement
These cements have physical properties comparable with those of composite resins, including:
Thin film thickness
Virtual insolubility in the mouth
The tooth must be free of all plaque and debris and must be prepared by etching or by treatment with a bonding system before cementation
What does insoluble mean? (Insoluble means that something won't dissolve in water.)
The tooth must be free of plaque and debris before being etched.

22. Application of Composite Resin Cement
Supplied
As a powder and liquid mix
In a syringe-type applicator as a base and catalyst
In a versatile light-cured/dual-cured system
Recommended portions of either application are dispensed onto a paper pad and mixed rapidly with a spatula
Composite resin is used for veneers.
Refer students to Procedure 45-2 (p. 774) for more information on mixing composite resin.

23. Examples of Composite Resin Cements Supplied in Variable Systems
The orange object in the lower right of the picture is a mixing well.
Composite material has been placed out on the paper pad.
A disposable brush tip has been placed in the composite brush handle.

24. Zinc Oxide-Eugenol Cement
Eugenol has a soothing effect on the pulp and is often used on patients when postoperative sensitivity may be a concern
Type I
Lacks strength and long‑term durability and is used for temporary cementation or provisional coverage
Type II
Has reinforcing agents added for the permanent cementation of cast restorations or appliances
What is provisional coverage? (Provisional coverage is a temporary coverage that is placed on a tooth to protect the tooth until the permanent restoration is ready to be cemented.)

25. Zinc Oxide-Eugenol Cement
Type I (paste)
Supplied as a two‑paste system as temporary cement
Pastes dispensed in equal lengths on a paper pad and mixed
Type II (liquid/powder)
Mixed on an oil‑resistant paper pad
Mixing time of 30 to 60 seconds
Setting time in the mouth of 3 to 5 minutes
Both systems are mixed on an oil-resistant paper pad; the pad will not absorb the liquid.
When a slower set is required, a glass slab is used.

26. Temp-Bond NE TempBond NE, a type I temporary cement.
This photo is an example of a two-paste system.
Dispense equal amounts from each tube but leave room on the paper pad to mix them together.
What does NE stand for? (The NE on the tube stands for no eugenol. Patients may have eugenol sensitivity.)

27. ZOE Type II Cement for Permanent Cementation
This is an example of a powder/liquid system.
Dispense powder on one side and liquid on the other side of the paper pad or glass slab.
Be sure to follow the manufacturer’s instructions for measurement and mixing.

28. Chemical Makeup of Zinc Oxide-Eugenol Cement
Liquid: eugenol, water, acetic acid, zinc acetate, and calcium chloride
Powder: zinc oxide, magnesium oxide, and silica
ZOE is one of the least irritating of all dental cements
The eugenol can have a strong odor, and may be offensive to some patients
What effect does eugenol have on the pulp? (Eugenol actually has a soothing effect on pulp and is often used in procedures when postoperative sensitivity may be a concern.)
ZOE has a pH close to 7.0, making it less acidic than other cements.
Smells like cloves.

29. Application of Zinc Oxide-Eugenol Cement
ZOE is mixed on an oil-resistant paper pad that will not absorb any of the liquid
Take care when using a eugenol product because of its irritating qualities to the oral mucosa
Try not to allow the liquid to come into direct contact with tissue
When a slower set is required, a glass slab can be used
The thickness of the mix is determined by the powder-to-liquid ratio, as recommended by the manufacturer
Refer students to Procedures 45-3 and 45-4 (p. 775) for more information on mixing zinc oxide-eugenol.
How can you modify the thickness of the zinc oxide-eugenol mix? (By altering the powder-to-liquid ratio)

30. Polycarboxylate Cement
This cement generally has been used as a permanent cement for cast restorations, stainless steel crowns, and orthodontic bands
It also maintains its versatility as a nonirritating base under composite and amalgam restorations and as an intermediate restoration

31. Chemical Makeup of Polycarboxylate Cement
Liquid: polyacrylic acid, itaconic acid, maleic acid, tartaric acid, and water
Powder: zinc oxide, magnesium oxide, aluminum oxide, and other reinforcing fillers
Polycarboxylate cement is less irritating to the pulp than zinc phosphate cement is, and the pulpal reaction is similar to that of ZOE cement
Polycarboxylate cement is also known as polyacrylic cement.

32. Application of Polycarboxylate Cement
Available in a powder and liquid form
Liquid may be measured using the plastic squeeze bottle or the calibrated syringe‑type liquid dispenser supplied by the manufacturer
The liquid has a limited shelf life because it will thicken as the water evaporates.
Mixing is carried out on a nonabsorbent paper pad
If it is necessary to increase the working time, a cool, dry glass slab can be used
What would be used if a longer working time was needed? (A cool, dry glass slab.)
Refer students to Procedure 45-5 (p. 776) for more information on polycarboxylate cement application.

33. Powder and Calibrated Syringe of Polycarboxylate Cement
This product is usually mixed on a paper pad.
The liquid part of the product comes in a syringe.
Do not dispense liquid until you are ready to mix the cement.
Could you mix the cement on a glass slab? Why would you do this? (Answers will vary.)

34. Zinc Phosphate Cement Classified as two types Type I (fine grain)
Used for the permanent cementation of cast restorations such as crowns, inlays, onlays, and bridges
Creates a very thin film layer, which is necessary for an accurate cementing of castings
Type II (medium grain)
Recommended for use as an insulating base for deep cavity preparations
Phosphoric acid can be irritating to the tooth pulp.

35. Zinc Phosphate Type I Cement for Permanent Cementation
Dispense the powder at one end of the slab and liquid on the other; mix them in the middle.
Is the mixing process (1) add powder to liquid or (2) add liquid to powder? (You add the liquid to the powder.)

36. Chemical Makeup of Zinc Phosphate Cement
Liquid: 50% phosphoric acid in water, buffered with aluminum phosphate and zinc salts to control the pH
Powder: 90% zinc oxide and 10% magnesium oxide
The phosphoric acid can be irritating to the pulp
A liner, sealer, or desensitizer should be placed first to reduce sensitivity to the phosphoric acid
Zinc phosphate is the oldest cement used in dentistry.
Is zinc phosphate a permanent or temporary cement? (Permanent)

37. Application of Zinc Phosphate
The powder is divided into increments of varying size, with each increment spatulated before the next increment is added
It is critical that the powder be added to the liquid in very small increments
This method dissipates the heat of the chemical action and retards the setting of the cement
What does dissipate mean? (Dissipate means to scatter in various directions or dispense.)
Powder and liquid should be dispensed just before being mixed.
Refer students to Procedure 45-6 (p. 777) for more information on the application on zinc phosphate.

38. Cement Removal
Once the dentist has completed the cementation procedure of an indirect restoration, the patient is asked to bite down for a few minutes on a cotton roll for the initial setting process
Excess cement is removed from around the margins, interproximal spaces, and adjacent areas covered with excess cement
If excess cement is not removed from in and around the gingival margin and sulcus of the tooth, the cement could irritate the area and cause inflammation and discomfort
If excess cement is not removed, what could happen to the gum tissue? (The cement can irritate the area and cause additional problems, such as inflammation and discomfort.)
The floss is usually knotted.
Refer students to Procedure 45-7 (p. 778) for more information on cement removal.

39. Excess Cement Removed After the Setting Process
Wait to remove cement until the initial setting is complete.
Who can remove cement from a permanent restoration? (Dentists or dental assistant, if it is not an expanded function)