1. Restorative and Esthetic
Dental Materials
Chapter 43

2. Introduction
Restorative dental materials fulfill an important role in the way dentistry is delivered today
Amalgam
Composite resin
Glass ionomer
Temporary restorative materials
Tooth-whitening products
Gold alloy
Ceramic castings
As a clinical dental assistant, you will be spending much of your time working with various restorative and esthetic dental materials.
It will be important to know which materials to have available, not only in the treatment rooms but also in the office supply room.
It will be important to know how to dispense and mix these materials properly and perhaps apply some of them yourself.
It will also be important to know how to properly clean the instruments used to prepare and place the materials and how to properly dispose of any leftover or expired materials.

3. Standardization of Dental Materials
Criteria for a new dental material
It must not be poisonous or harmful to the body
It must not be harmful or irritating to the tissues of the oral cavity
It must help protect the tooth and oral tissues of the oral cavity
It must resemble the natural dentition as closely as possible so as to be esthetically pleasing
It must be easily formed and placed in the mouth
It must conform and function
The Council on Dental Materials, Instruments and Equipment, a subcommittee of the American Dental Association, works with federal agencies to ensure that strict specifications are followed by manufacturers in the development of new dental materials.
Many materials may be harmful to the oral cavity when in their unset or unmixed component form, yet, if handled properly, provide a safe and desirable restoration once completed.

4. Properties of Dental Materials
The types of dental materials used to restore teeth must respond to and withstand specific factors associated with oral conditions
The following characteristics enhance the ability of dental materials to withstand the oral environment and allow for easy application:
Mechanical properties
Thermal changes
Electrical properties
Corrosive properties
Solubility
Application properties
Some of the properties apply to all dental materials and some are more important with certain types of materials.
Sometimes thermal insulation is desirable, for example, under an extensive restoration. Other times, for example, under a denture base we would like thermal transfer.
Electrical and corrosive properties are important with metallic restorations.

5. Mechanical Properties
Materials must be able to withstand the biting and chewing force in the posterior area of the mouth
Force is any push or pull on matter
Stress is the reaction within the material that can cause distortion
Strain is the change produced within the material that occurs as the result of stress
Mechanical properties of a material placed in the anterior area should also withstand various forces caused by factors including occlusion and a patient’s habits.
A restoration will eventually reach a breaking point, causing permanent deformation (change) after a certain amount of both stress and strain is applied over a certain amount of time.
Stress is the amount of load per unit of a cross-sectional area. What is an example of stress? (Chewing)
Remember that different materials have different properties under different types of force.

6. Types of Stress and Strain
Tensile stress
Pulls and stretches the material
Compressive stress
Pushes the material together
Shear stress
Breakdown of the material as the result of something sliding over two areas
What type of stress may a material undergo if subjected to the following scenarios?
A patient enjoys eating sticky candy. (Tensile stress)
A patient reports clenching his teeth when he is concentrating hard at work. (Compressive stress)
A patient has a habit of grinding her teeth at night, or nocturnal bruxism. (Shear stress)

7. Types of Stress and Strain (Cont.)
Figure 43.2: Types of stress and strain: compressed, tensile, and shear.
These types of stresses may also be demonstrated to students using the palms of your hands.
© Elsevier Collection.

8. Ductility and Malleability
Ductility: Measure of the capacity of a metal to be stretched or drawn out by a pulling or tensile force without fracturing
Malleability: Measure of the capacity of a metal to be extended in all directions by a compressive force
Ductility and malleability are measures of a metal’s ability to withstand permanent deformation by either tensile or compressive forces.

9. Thermal Change
A change in temperature in the oral cavity resulting from a hot or cold product
These thermal changes are of major concern because of:
Contraction and expansion
The need to protect the pulp from thermal shock from extreme differences in temperature
Has anyone experienced sensitivity caused by a hot or cold food or drink in his or her mouth? (Answers will vary.)
When the restorative material and surrounding tooth structure have different rates of contraction and expansion, microleakage may occur. Space between the tooth and the restoration allows saliva or bacteria to enter, causing sensitivity and/or breakdown of that interface and ultimately destroying the restoration and permitting decay in the tooth.

10. Contraction and Expansion
Each type of dental material will contract or expand at its own rate
It is essential that the tooth structure and restorative material have, as nearly as possible, the same rate of contraction and expansion
Significantly different rates of contraction and expansion can cause the dental material to pull away from the tooth, which can result in microleakage, or a faulty restoration
The minute separation could allow fluids, debris, and microorganisms to enter between the restoration and the wall of a cavity preparation
The ideal restorative material is one that contracts and expands at a rate similar to that of the tooth within which it was placed.
If the linear thermal coefficient of expansion differs between the two materials, percolation occurs as the materials thermocycle. This occurs in roadways where water freezes during the wintertime. Small amounts of water seep into tiny cracks. When the water freezes it creates bigger cracks and the pavement breaks apart.
What is the term for the process of minute separation that could allow fluids and such to enter between a restoration and the wall of a cavity preparation? (Percolation)

11. Electrical Properties
An electrical current, or galvanic action, in the oral cavity can take place when there are two different or dissimilar metals present
Conditions that allow these electrical currents include:
Saliva contains salt, a good conductor
Two metallic components of different composition can act as a battery
Galvanic action, or shock, is the coming together of all these conditions
What does galvanic shock feel like? (An undesirable tingling sensation)
One patient who may report such a feeling is someone who has teeth on opposing arches that contact each other in function. The teeth contain restorations composed of different metals (e.g., a full gold crown opposing a large amalgam).
In the above scenario, the oral cavity acts like a battery, with saliva helping relay the electrical current.

12. Corrosive Properties and Hardness
Corrosion is the reaction that occurs within a metal when it is exposed to corrosive products such as temperature, humidity, and saline
Certain foods contain metallic forms that cause corrosion of a dental material
Most corrosion involves surface discoloration and can be removed easily with the use of polishing agents
Hardness is a measure of the resistance of a metal to indentation, scratching, or abrasion
What common drinks or foods have corrosive properties? (Soft drinks, concentrated lemonade, and other products that create a highly acidic oral environment)
Plaque that remains for an extended period on the margin between an amalgam and the tooth may also produce a more acidic environment locally.
An acidic environment (lactic acid under dental plaque) drastically changes the solubility of tooth structure, such as enamel. Because enamel is the hardest substance in the body, the plaque must have been present for a considerable amount of time for a cavity to occur.

13. Solubility
The degree to which a substance will dissolve in a given amount of another substance
Sand has low solubility because it does not dissolve easily
Sugar has high solubility because it does dissolve easily
A material that dissolves easily in the oral environment is of limited use because it will wash away and leave the tooth structure exposed
The mouth is exposed to many kinds of acids, which can dissolve materials. Many sodas and sports drinks have a very acidic pH. Citric acid is added to many foods to give them a tart taste.

14. Application Properties
For a dental material to have specific mechanical properties, steps must occur in the application of the dental material
Techniques used in the application help determine the properties of that application
What are the different properties of dental materials that may affect the application properties? (Flow; adhesion, which includes wetting and viscosity; retention; and curing)

15. Flow
When decay is removed and healthy tooth structure is prepared to receive a permanent filling material, the dental material must be pliable enough to be placed in the preparation
Dental materials are designed to have a certain amount of flow for placement
This allows the material to fill in the preparation of the tooth
When sealants that help prevent decay are placed on newly erupted permanent molars that are deeply fissured, the sealant material must flow well to plug up and protect areas that are not easily cleaned.

16. Adhesion
The strength that causes unlike materials to adhere to each other
Without proper adhesion, microleakage can occur, and the restoration could come out
Characteristics of dental materials that can affect the adhesion process are:
Wetting: Ability to flow over a surface
Viscosity: Property of a liquid that causes it not to flow easily
Surface characteristics: Influence the wetting ability
Film thickness: Thinner means a stronger adhesive junction
Adhesion may be thought of as placing a piece of tape on a piece of paper.
A consideration in wetting is whether two materials are hydrophilic (water-loving) or hydrophobic (water-hating). A hydrophilic surface would not be wet well by a hydrophobic liquid.
For an example of ideal film thickness, think of piecing together a broken china ornament using Krazy Glue rather than the thicker glue used in grade school craft projects.

17. Retention
Ability of holding two things firmly together when they will not adhere to each other naturally
Dental restorations, castings, and appliances must be held in place with the use of materials and retention methods
Even though retention holds the material in place, it does not completely seal the two structures together
Microleakage can occur if an additional material such as a bonding material is not placed to create a seal
Retention is very important in the preparation of teeth that are to receive amalgam fillings. One of the ways in which retention is achieved is preparing the opposing inside walls of the tooth to slant slightly inward so that when amalgam is placed and set it will not slide out.
There are two types of retention: mechanical and chemical. The application of sealant is an example of mechanical retention. The etchant increases the surface area for retention and the sealant material flows into all the nooks and crannies on the surface of the tooth.

18. Curing
A setting process of a dental material that is initiated by a chemical reaction or by light in a blue wave spectrum
Auto-cured material hardens as a result of a chemical reaction of the materials once mixed together
Light-cured material does not harden until it has been exposed to a curing light
With dual-cured material, some curing takes place as the material is mixed
The final cure does not occur until the material has been exposed to a curing light
Bonded materials are set (hardened) by various means, including the exposure to light of a particular wavelength, chemical reaction (auto), or a combination of the two.

19. Direct Restorative Materials
Applied to a tooth or teeth while the material is pliable and can still be adapted, carved, and finished
Materials used in these types of restorative and esthetic procedures are:
Amalgam
Composite resins
Glass ionomers
Temporary restorative materials
Tooth-whitening products
Numerous materials fulfill most of the aforementioned criteria, yet there is an ongoing search for new materials and improvements to existing materials so that they may fulfill all criteria.
Today much emphasis is placed on the esthetic aspect of restorative dentistry as patients seek to obtain, and dental professionals seek to create, a beautiful, natural-looking smile.
These materials are placed in the mouth and adjusted to a desirable finish. They replace tooth structures that are missing as a result of cavity removal, fracture, or a deficiency at the time of the appointment.
There are very distinct methods of dispensing, preparing, placing, and finishing these materials. All are very technique-sensitive and offer a wide range of treatment options.
Tooth-whitening systems are examples of esthetic restorative dentistry.

20. Amalgam
Amalgam consists of several different metals, with silver being the predominant metal
Metals are in a powder form and then mixed with mercury to form a soft, pliable mixture
When placed into a prepared tooth, condensed, carved, and allowed to harden, the mixture becomes a permanent amalgam restoration
Amalgam is a safe, affordable, and durable material used predominantly to restore premolars and molars
Although amalgam has been used in restorative dentistry for many years, you may see fewer amalgam restorations placed as a result of esthetic concerns of patients and the ongoing controversy about the safety of amalgam use for both the patient and staff.
Even if you see a minimal number of amalgam restorations being newly placed, you will surely see numerous existing amalgam restorations that remain in good condition for many years after placement.

21. Class II Amalgam Restoration
Figure 43.7 shows an example of a class II amalgam restoration.
A class II restoration is one that includes both the necessary portion of the occlusal surface and the proximal surface abutting the adjacent tooth, in this case the mesial.
Ideally all teeth to be restored should be isolated with the use of a rubber dam in this manner. In reality, clinical circumstances do not always allow this.
From Heymann HO, Swift EJ, Ritter AV: Sturdevant’s art and science of operative dentistry, ed 6, St Louis, 2013, Mosby.

22. Indications for Using Dental Amalgam
Primary and permanent teeth
Stress-bearing areas of the mouth
Small to moderate-sized cavities in the posterior teeth
Severe destruction of tooth structure
As a foundation for cast-metal, metal-ceramic, and ceramic restorations
When a patient’s commitment to personal oral hygiene is poor
When moisture control is problematic
When cost is an overriding patient concern
The most convincing indication for amalgam placement continues to be when restoring an area where blood and saliva contamination is extremely difficult, beneath the gingiva, or both, or in a poorly accessible, nonesthetic region of the mouth where composites are contraindicated.

23. Contraindications for Using Dental Amalgam
When esthetics is particularly important
With patients who have a history of allergy to mercury or other amalgam components
When a large restoration is needed, and the cost of other restorative materials or treatment options is not a significant factor in the treatment decision
A patient who presents with an amalgam allergy should be questioned about the specific reaction and how the allergy was diagnosed.
It is important to ask patients which type of restoration they prefer if choice is an option.
If the patient opts for an unfavorable choice, the discussion should be documented.
Once a restoration has been placed in the mouth, the materials used and methods followed must be documented in the patient’s chart.

24. Composition of Dental Amalgam
The end result of mixing approximately equal parts
Mercury (43% to 54%)
An amalgam alloy powder (57% to 46%)
The alloy powder is a combination of metals
Silver, which gives it its strength
Tin, for its workability and strength
Copper, for its strength and corrosion resistance
Zinc, to suppress oxidation
The widely used Eames technique specifies a 1:1 ratio of mercury to alloy.
The main differences in composition and classification of dental amalgam alloy powders are based on what? (Alloy particle shape and size, copper content, and zinc content)
If you have the opportunity to work with amalgam, you may eventually be able to distinguish between brands because of how they feel when properly triturated and how workable they are during condensation and carving.

25. Composition of Dental Amalgam (Cont.)
Fig displays the mercury liquid and alloy powder, separated on the left, and at various stages of mixing to produce a final amalgam for placement.
It is important to ensure that trituration is complete before amalgam is placed in a carrier for placement in the preparation. Different manufacturers call for different trituration times, depending on the components of their products.
Other variables to keep in mind: Triturating machines sometimes malfunction, and stocked amalgam capsules may reach their expiration dates before being used.
From Hatrick CD, Eakle WS: Dental materials: clinical applications for dental assistants and dental hygienists, ed 3, St Louis, 2016, Elsevier

26. High-Copper Alloys
Contain a higher percentage of copper than previous alloys
Classified according to their particle shape:
Spherical (round particles) or irregular (rough, lathe-cut particles)
Particle shapes influence the trituration and working characteristics of the resulting amalgam mixture
With a high-copper amalgam alloy, the copper reacts with the mercury before the tin can react with mercury. This reaction eliminates a weak tin-mercury phase and the material is less subject to marginal breakdown.
Refer students to Table 43.1 for more information.

27. Mercury-to-Alloy Ratios
The ratio must contain just enough mercury to make the mix workable without containing an excessive amount of mercury
A 1:1 mercury-to-alloy ratio is widely used
What is the 1:1 mercury-to-alloy ration known as? (Eames technique)
In the past, the dentist used a mercury dispenser to dispense a drop of mercury into a reusable capsule. The size of the drop of mercury was inconsistent, so a squeeze cloth was used to remove excess mercury.
Condensation techniques also bring the excess mercury to the surface of the newly placed restoration, where it is carved away.

28. Nonmercury Alloys
A nonmercury alloy called Galloy, which is composed of gallium, indium, and tin, has been approved by the American Dental Association (ADA)
Gallium, the alloy base ingredient, is a soft, silver-hued metal that liquefies at 86º F
Galloy is sensitive to moisture, which can cause corrosion and expansion
How should Galloy be placed? (It is recommended that this material be placed after the tooth has been lined with a resin and that an application of sealant be placed over the restoration.)

29. Controversial Issues Regarding Mercury
The controversy has evolved in two directions:
Potential harm to patients from mercury within the amalgams placed in their teeth
Toxicity level of mercury vapors affecting dental personnel exposed over a long period
It is important to stress to patients that once amalgam is set, the mercury content is inactive.
The amount released in the mouth under the pressure of chewing and grinding is extremely small and presents no cause for alarm.
This amount is less than what patients are routinely exposed to in food, air, and water.

30. Controversial Issues Regarding Mercury (Cont.)
The ADA and the National Institute of Health-Nations Administration have agreed that there is no basis for claims that amalgam is a significant health hazard
The health risk for dental personnel is greater than that for a patient
The dentist and assistant who are exposed to mercury vapors daily should be aware of their toxic effects
An increase in exposure can result in tremors, kidney dysfunction, depression, and central nervous system disorders
It may be more detrimental to remove more than one tooth by replacing a sound amalgam restoration than to leave it alone. The oral environment may be re-exposed to mercury with removal.
Do not touch mercury with your bare hands.
Do not vacuum spilled mercury.
Get a mercury spill kit with a magnet.

31. Management Practices for Mercury Amalgam
Figure shows management practices for mercury amalgam.
Refer students to Box 43.1 for a list of best management practices for mercury amalgam.
© Elsevier Collection.

32. Application of Dental Amalgam: Preparation
Amalgam is supplied by the manufacturer in sealed single-use capsules with the proper ratio of alloy powder in one side of the capsule and mercury on the other side, separated by a thin membrane
Capsules are available with:
600 mg of alloy for small or single-surface restorations
800 mg of alloy for larger restorations
If more amalgam is required, additional capsules are triturated as needed
Amalgam capsules come in different doses, so you should try to estimate what you need.
Avoid triturating another dose of amalgam until the dentist is ready for it.

33. Trituration
The process by which mercury and alloy are mixed together to form the mass of amalgam needed to restore the tooth
Many types of capsules require the use of an activator, which breaks the activating membrane
The amalgamator is set to operate for the length of time specified in the manufacturer’s directions
The mix is placed from the capsule into an amalgam well and the mix is loaded into the amalgam carrier
What is trituration also known as? (Trituration is also known as amalgamation.)
It is possible for a mass of amalgam to be under-triturated or over-triturated. Either of these negatively affects the properties of the set material.
Refer students to Procedure 43.1 for more details.
Why is the cover of the amalgamator closed? (To prevent mercury vapors from escaping during trituration. It also prevents the capsule from flying out into the room, if it has been properly placed into the prongs of the arm used to mix the capsule.)

34. Condensation
The amalgam is carried to the tooth by the amalgam carrier and placed in increments into the prepared tooth
Each increment is condensed immediately with the use of an amalgam condenser
The purpose of condensation is to pack the amalgam tightly into all areas of the prepared cavity and to aid in removing any excess mercury from the amalgam mix
It is important to work efficiently here, as the silver amalgam is setting from the time amalgamation is complete.
Single- and double-ended amalgam carriers are available that can carry different sizes of increments depending on the dentist’s preference.
Pass the loaded amalgam carrier so that the end with amalgam to be placed and condensed is closest to the tooth.

35. Carving and Finishing
With the use of hand carving instruments, the dentist is able to carve back the amalgam material to the tooth’s normal anatomy, which was removed during cavity preparation
A burnisher is used to smooth the amalgam
Once most of the carving has been completed, the patient is instructed to bite down lightly on articulating paper
This allows the dentist to check how the new restoration occludes with the opposing tooth, and then final carvings can be made
If the restoration involves a proximal surface, a matrix band and wedge must be placed to reform the contour as necessary. The burnisher is used at this step to burnish the metal where contact will be reestablished with the adjacent tooth.
Polishing of amalgams, if desired, is done during a subsequent appointment with the use of a polishing cup and a slow-speed handpiece.

36. Composite Resins
Composite resins are becoming the widely accepted material of choice by dentists and patients
They have been placed mainly in anterior teeth because of their esthetic qualities, but with new advances, they are increasingly being placed in posterior teeth as well
Composite resins are not as strong as amalgams or gold restorations
Ask how many students have had composites placed in their mouths and if they are able to tell which teeth are composites by visual examination or touch. (Answers will vary.)

37. Class IV Composite Restoration
Figure shows class IV composite restoration before (A) and after (B).
A skilled operator is able to disguise a composite restoration using color or color combination and by incorporating contours similar to the tooth’s contralateral.
From Heymann HO, Swift EJ, Ritter AV: Sturdevant’s art and science of operative dentistry, ed 6, St Louis, 2013, Mosby.

38. Indications for Composite Resin Use
Restore class I, II, III, IV, and V restorations
Restoration of surface defects such as hypocalcification, attrition, abrasion, and congenital abnormalities
Closure of diastema
Esthetic recontouring of teeth such as peg laterals
What oral environments may be unfavorable for placement of a composite resin? (Poor isolation, poor oral hygiene, tremendous bruxism, and lack of use of a night guard)
Overall treatment-planning note: If the patient desires full-mouth whitening, it should be done before placement of any composites in an esthetic region, or the composites may no longer match after whitening.

39. Contraindications for Composite Resin Use
When esthetics is not an important factor
With patients who do not have daily proper oral hygiene habits, especially in the posterior area
When the cost of restorative materials is a significant factor in the treatment decision
Direct composite resin restorations are typically more costly than their amalgam equivalent. Placement is very technique sensitive and requires more time, due to incremental addition and curing of the material.
These materials are usually light-cured and are as hard as they will ever be when the patient leaves the office. This is different than the silver amalgam restorations, which can be carved for a while following placement and continue to harden after the patient leaves the office.

40. Composition of Composite Resins
The composition of composite resins is a chemical mix, which includes:
An organic resin matrix
Inorganic fillers
A coupling agent
Pigments
Is the resin matrix inorganic or organic? (The resin matrix is organic. Organic means it contains carbon.)
The coupling agent bonds the inorganic and organic portions together.

41. Resin Matrix
A fluid-like material called dimethacrylate, also referred to as BIS-GMA
The fluid, which is the monomer, is used to make synthetic resin
By itself, it is not strong enough to be used as a restorative material
Addition of fillers and coupling agents allows polymerization to take place
Additional additives are the initiator, accelerator, retarder, and ultraviolet (UV) light stabilizers
Dimethacrylate is a tissue irritant in its monomer state.
Polymerization is the process of bringing together multiple monomer units, using light as a catalyst.

42. Filler
Inorganic fillers include quartz, glass, silica particles, and colorants
These fillers add the strength and characteristics that are needed in a restorative material
The amount of filler, the particle size, and the types of fillers used are important factors in determining the strength and wear-resistant characteristics of the material
Composites that have a combination or mixed range of particle sizes are referred to as hybrids
Fillers come in many shapes and sizes and are used in different amounts to produce the desired physical and chemical properties.

43. Types of Composites Macrofilled composites Microfilled composites
Contain the largest of filler particles, providing the greatest strength, but a duller, rougher surface
Self-cured, used in areas where great strength is required
Microfilled composites
Contain inorganic fillers much smaller than those in macrofilled composites
Capable of producing a highly polished finished restoration; used primarily in anterior restorations
Which type of composite is strongest? (Macrofilled composite)
What property of macrofilled composites has limited their use today? (These composites contain the largest filler particles, which result in a duller, rougher surface.)

44. Hybrid Composites Used most often today
Contain a mixed range of particle sizes
Can be polished smoother than macrofilled composites, yet they have greater strength than what is seen with microfilled composites
High wear resistance and excellent shading characteristics
Hybrid composites are widely used today for universal applications. They provide a happy medium of strength and polishing ability.
The current trend is to use composites with smaller and smaller filler particles. These are called nanofilled composites.

45. Flowable and Sealant Composites
Flowable composites
Supplied as either a hybrid or nanofilled composite with enough filler included to make the material wear-resistant
Flow is the key term when describing this type of composite
The material is designed to flow easier into the more conservative preparation
Sealant composites
Resemble flowable composites with less viscosity to allow the material to flow into the pits and fissures of the tooth surface
These materials are recommended for what type of lesion? (They are recommended for cervical class V lesions, such as areas of toothbrush abrasion or abfraction. They are not recommended for areas subject to heavy wear such as occlusal surfaces.)
Most sealants used today are filled resin sealants. These qualify as composite restoratives because they have filler particles.

46. Coupling Agent
Strengthens the resin by chemically bonding the filler to the resin matrix
To achieve this, the filler particles are coated with an organosilane compound
The silane portion bonds to the quartz, glass, and silica filler particles
The organic portion bonds with the resin matrix, thus bonding the filler to the matrix
Silanation is also used to prepare porcelain veneers for bonding to tooth structure.

47. Pigments
For a composite material to match a tooth color, coloring must be added
Most often, the color comes from an inorganic substance
Teeth have many different shades, including reds and blues.

48. Application of Composites
Differences for composites versus amalgam include the following:
The cavity preparation for a composite resin is designed to hold the resin material by means of a bonding system rather than by retention added into the preparation
Specific dental materials cannot be used with composite resins
The matrix system will vary with composite resins
Placement of composite resin is accomplished by increments; light-curing is performed before additional increments are added
Some operators like to place the material directly into the tooth themselves with the use of the handheld applicator.
Only 1- to 2-mm increments should be placed and light-cured at one time.

49. Shade Selection
One of the most critical aspects when working with composite resins
A shade guide is always used when determining the correct shade for application
The composite kit may include its own shade guide; most manufacturers cross-reference their shades with those of the VITA shade guide
The shade should be chosen before the tooth is prepared because desiccation throughout the procedure changes the color.
The shade of composite is selected using a shade guide. There are many different shades available. Some manufacturers even have more than one type of shade for different parts of the tooth.

50. Tips When Choosing a Shade
Determine tooth shades if possible in daylight or with standardized daylight lamps and not under normal ambient lighting
The entire surroundings should be kept free from bright colors
Make the choice quickly; always accept the first decision since the eyes begin to tire after approximately 5 to 7 seconds
A blue background such as blue sky is good for refreshing tired color receptors.
Refer students to Figure to view a shade guide for color matching.

51. Application
Composite resins are supplied in a single-paste, lightproof syringe or individual units
The paste contains both the photo initiator and the amine activator and will not polymerize until it is exposed to the curing light
The material is supplied in a kit that includes varying shades of the composite resin, along with an etching and bonding system that works specifically for the application process of that material
The individual units are more costly than the syringes.

52. Polymerization of Composite Resins
Polymerization is the process by which the resin material is changed from a pliable state into a hardened restoration
Occurs through auto-curing or light-curing
Light-curing uses a high-intensity light source
The exact curing time depends on the:
Composite manufacturer’s instructions
Thickness and size of the restoration
Shade of the restorative material used
In light-curing, what determines the duration of curing? (Manufacturer of material instructions, type of light being used, thickness and size of material being placed, shade of material being used)

53. Finishing and Polishing
The finishing and polishing of composite resins are much different from the completion steps in an amalgam procedure
Because composite materials go from the soft, pliable state to being completely hardened by polymerization, the dentist is not able to carve or make adjustments with hand instruments
Finishing burs and abrasive materials are used to contour and polish a finished composite resin
Rotary instrumentation includes green and white stones and carbide and diamond finishing burs.

54. Steps in Finishing a Composite Restoration
Reduction of the material is by the use of a white stone or a finishing diamond
Fine finishing is performed with the carbide finishing burs, then with diamond burs
Polishing the resin begins with medium disks and finishes with superfine discs
Finishing strips assist in the polishing of the interproximal surfaces
Polishing paste applied to a rubber cup completes the step
Proper occlusion should be reestablished first.
In addition to polishing discs, points and cups help shape the newly placed restoration.
Refer students to Procedure 43.2: Preparing Composite Resin Materials.

55. Glass Ionomers
Glass ionomer represents one of the most versatile dental materials available
Because glass ionomers have the ability to adhere chemically to teeth, the need to prepare the tooth structure is not as extensive as the preparation for an amalgam or composite resin
The most unique feature of glass ionomers is the release of fluoride after the final setting
Note that etching and other pretreatments are not necessary, so the smear layer remains.
The components may be light-sensitive.
The material is biocompatible.
Commercial examples of these are Vitrebond and Fuji LC.

56. Indications for Glass Ionomer Use
Primary teeth because of the fluoride release and minimal cavity preparation requirement
Final restorations in nonstress areas such as class V and root surfaces
Sealants
Core material for a buildup
Provisional (longer-term temporary) restorations
In the restoration of a deep cavity preparation, CaOH (Dycal) may be placed in the deepest portion over the pulp as a liner, followed by glass ionomer (Vitrebond), which must be light-cured.
The remaining preparation is then etched, bonded, and restored with the use of composite resin.
Glass ionomer alone may also be placed on dentin in a slightly deep area of a preparation.

57. Composition of Glass Ionomers
In the term glass ionomer, the word glass actually refers to a combination of glass, ceramic particles, and a glassy matrix
From this special glass combination, the material derives its translucency and prolonged fluoride release
Ionomer refers to ion-cross-linked polymers, such as acrylic acid, tartaric acid, and maleic acid
The type of polymer and its molecular weight ensure excellent adhesion and resistance to acid erosion
Ionomers in the name glass ionomers refer to which ion cross-linked polymers? (Acrylic, tartaric, and maleic acids)

58. Glass Ionomers Materials
Resin modified
Gives the material better strength, greater wear resistance, and an improved esthetic quality
Metal reinforcement
Blend of silver-tin alloy with glass ionomer provides a strong, abrasion-resistant material
Preparation tip: With powder and liquid components, such as Vitrebond, the powder is fluffed to loosen the components before being dispensed.
Place with the use of a ball applicator (only on dentin).
Half a millimeter or less should be placed first and cured, after which a second layer of as much as 2 mm may be placed.
Components should be mixed in 10 to 15 seconds to allow ample working time (about 2 minutes). The mixture should then be light-cured for a minimum of 30 seconds.
Remember, a higher room temperature will increase the setting time.

59. Fabrication and Application
When supplied as a powder and a liquid for a cement, glass ionomers are manually mixed together on a treated paper pad
For restorative purposes, glass ionomers are supplied in either light-protected tubes, cartridges, tubes, or premeasured capsules
The material can be either manipulated with a spatula and placed in the applicator, or triturated and then placed in the applicator, and applied to the tooth and light-cured
Should the powder be added to the liquid, or the liquid added to the powder when glass ionomers are manually mixed? (The powder should be incorporated into the liquid.)
How long should glass ionomer cement be mixed? (The material must be completely mixed in less than 45 seconds.)
What are some cautions for using glass ionmers? (Avoid water contamination/contact with the material. Be aware that when the material’s glossy appearance has disappeared, the setting stages have begun. Protect the matrix band from the material; the material will adhere to the metal band.)

60. Temporary Restorative Materials
Material selected for a temporary restoration is designed to maintain and restore function and keep the patient comfortable for a limited time
Indications:
Reduce the sensitivity and discomfort of a tooth to determine a diagnosis
Maintain the function and esthetics of a tooth until a permanent restoration can be placed
Protect the margins of a prepared tooth that will receive a permanent casting at a later time
Prevent shifting of adjacent or opposing teeth because of open space
These materials are used for emergencies when there is insufficient time for a final restoration and when the tooth is too sensitive for a final restoration to be placed.

61. Intermediate Restorative Material (IRM)
Figure shows placement of intermediate restorative material (IRM) into a molar.
This slide displays a molar isolated with the use of a rubber dam and surrounded by a matrix and matrix holder (bottom of photo), with a wedge (blue) at the distal edge.
The bright-white material, IRM, is being placed with the use of the instrument shown in the image.
Newly mixed IRM has a puttylike consistency and must remain dry until it is completely set.

62. Temporary Restorative Materials
If a tooth has lost a filling or has a small pit, an intermediate restorative material would be selected
If a cusp is gone, or if the dentist has prepared the tooth for a cast restoration, a provisional material would be selected
It is called an intracoronal restoration when the restorative material is surrounded by the tooth.
It is called an extracoronal restoration when the restorative material extends over a cusp.

63. Intermediate Restorative Materials
IRM is a reinforced zinc-oxide eugenol composition
Eugenol has a sedative effect on the pulp, and fillers are added to improve the strength and durability of the material
Describe clinical situations in which IRM may be placed, such as in the following:
(A patient presents with a very sensitive posterior tooth. Caries removal extends deep toward the pulp and extensively throughout the tooth to the point that a crown is indicated. IRM may be placed for 4 to 8 weeks to see whether symptoms decrease before final restoration [direct, indirect, or both]. The necessity for a root canal can be evaluated before the final restoration. IRM placement is also useful in situations in which the diagnosis, the prognosis of the tooth, or both are unclear and under circumstances in which time is limited, such as in emergency treatment.)

64. Intermediate Restorative Materials (Cont.)
Common uses of IRM include:
Restoration of primary teeth
Restorative emergencies
Caries management programs
IRM is supplied as a powder and a liquid, which are mixed manually on a treated paper pad, or as premeasured capsules that are activated and then triturated
Is IRM compatible with composite resin? (No)
If IRM is dispensed as a powder and a liquid, what is the ratio? (One drop to one scoop, mixed with the use of a metal spatula)
If IRM is dispensed in premeasured capsules, they are mixed by means of trituration, like amalgam capsules, in an amalgamator.
Both of these methods may require the addition of more powder to improve manipulation.
Refer to Procedure 43.3: Mixing Intermediate Restorative Materials.

65. Provisional Restorative Materials
Designed to cover the major portion of a tooth or several teeth for a longer period
Acrylic resins are supplied in several ways: as a liquid/powder, in premeasured tubes, and auto-mix cartridges
The material is placed in an alginate impression or a vacuum-formed tray and is seated over the prepared tooth and allowed to cure
The occlusion is adjusted, and the temporary is polished and cemented in place with temporary cement
You will need to be comfortable with dispensing and mixing this material if you assist in indirect restorative procedures.
Knowledge of this material will also be important if you are asked to fabricate provisional restorations as an expanded-duty assistant. Vacuum-formed tray: Plastic stent formed over model of the tooth or teeth before preparation for an indirect restoration.
Caution: Some materials are set in an exothermic reaction (giving off heat). Therefore the necessary precautions, such as rinsing the tooth with cool water during setting, should be taken.
Some provisional materials must be polished to a final luster.
Refer to Procedure 43.4: Preparing Acrylic Resin for the Fabrication of Provisional Coverage.

66. Provisional Coverage Material
Figure shows an example of provisional coverage material.

67. Acrylic Resin
Figure 43.24: Acrylic resin is supplied as liquid/powder, tubes, and automix cartridges.
At the bottom left are a liquid (dark bottle) and a powder (white bottle). The dropper is used to measure liquid into a dappen dish, to which the powder is gradually added to achieve the desired consistency.
This photo displays a few of the dispensing methods for these materials, including an auto-mixing tip attached to a cartridge with two separate barrels, which is attached to a dispensing gun.
From Hatrick CD, Eakle WS: Dental materials: clinical applications for dental assistants and dental hygienists, ed 3, St Louis, 2016, Elsevier.

68. Tooth-Whitening Materials
One of the most popular and cost-effective ways of restoring the esthetic appearance of teeth
Whitening products can be found in many everyday items such as toothpaste, fluoride, mouth rinses, and even chewing gum
Ask the students how many of them have had their teeth whitened. If some have, ask them to share their experiences with the class.
Tooth-whitening is an important adjunct to overall treatment plans in cosmetic restorative dentistry.
Besides the anterior teeth, all the facial/buccal surfaces of teeth that are visible when the patient is smiling can be whitened.
Reminder: Only natural tooth structures will whiten. Indirect porcelain restorations and direct composite resins will not.

69. Tooth-Whitening Materials (Cont.)
Figure shows before and after the use of a whitening product.
The shade guide is used to record the patient’s baseline tooth shade before whitening.
The baseline shade must be recorded in the patient’s chart.
Notes should also be made of other baseline characteristics, such as the shade of the canines, which are usually darker than the rest of the dentition.
Some practitioners also take clinical before-and-after photos.

70. Composition of Whitening Materials
Most tooth-whitening products are made from a peroxide-based ingredient
Peroxide-based solutions are supplied in different concentrations
Peroxide-based whitening products work deep within the enamel to remove staining and discoloration that have come from years of accumulated stain and aging
Most people are familiar with 3% hydrogen peroxide from the pharmacy.

71. Reasons Teeth Become Discolored
Aging
Consumption of staining substances such as coffee, tea, colas, and tobacco
Trauma
Use of tetracycline
Excessive fluoride
Nerve degeneration
Aging of restorations
Tooth whitening is contraindicated during pregnancy and lactation.
For optimal results, teeth should be clean and free of plaque.
Individuals with tetracycline staining (intrinsic) will have to wait longer than individuals whose teeth are discolored as a result of time, age, and extrinsic staining to see results from whitening.

72. Methods of Tooth Whitening
Patients can choose “in office” or “at home”
Most in-office procedures use the bleaching agent carbamide peroxide, which breaks down in the mouth to form hydrogen peroxide
The bleaching gel typically contains between 10% and 30% carbamide peroxide
In general, concentrations dispensed for at-home use are lower than those used for in-office tooth whitening.

73. Methods of Tooth Whitening
A newer choice for in-office whitening is the power or light-accelerated bleaching, also referred to as laser bleaching
A power bleaching treatment typically involves isolation of soft tissue with a resin-based, light-curable barrier, application of a professional hydrogen peroxide whitening gel (25% to 38% hydrogen peroxide), and exposure to the light source for 6 to 15 minutes
Individuals who undergo in-office whitening, which involves the use of a higher concentration of solution over a short period, may experience a higher level of post-procedure sensitivity.
Final whitening results appear a few weeks after treatment completion. At this time, non-matching composite resins, veneers, and porcelain crowns are replaced with ones that match.

74. Methods of Tooth Whitening
Teeth whitening at home can be accomplished using high-concentration carbamide peroxide, which is readily available and can be much more cost-effective than the in-office procedure
Whitening is performed by applying a concentration of oxidizing agent to the teeth with thin plastic trays or strips for a short period
The application ideally should be well-fitted to retain the bleaching gel, ensuring even and full tooth exposure to the gel
Many products are available over-the-counter at the pharmacy.

75. Methods of Tooth Whitening
The material will typically stay on the teeth for about 15 to 20 minutes
Trays or strips are then removed and the procedure is repeated over several days
Have any of you tried these products? (Answers will vary.)
How do you feel about the results? (Answers will vary.)
Did you have any sensitivity? (Answers will vary.)

76. Indirect Restorative Materials
An indirect restoration is one that is fabricated outside the mouth by a dental laboratory technician
These restorations involve a chain of procedures, including:
Preparing the tooth
Taking a final impression
Waxing a pattern
Investing the pattern
Casting the restoration
Finishing and polishing the casting
Cementing the restoration in place
What are some of the indications for the placement of an indirect restoration? (A considerable amount of the natural tooth structure is missing as a result of trauma, decay, or fracture; a tooth has been endodontically treated; cosmetics or function needs to be restored; a surgically placed implant[s] must be restored)

77. Gold-Noble Metal Alloys
Gold in its purest form is much too soft for use in cast dental restorations
The combination of gold with other metals to form an alloy provides the characteristics and hardness required of an indirect restoration
One way of describing the alloys is to discuss their noble and base metal content
Noble metals consist of gold, palladium, and platinum
All other metals in the alloys that are not classified as noble metals are considered to be base metals
Impressions of the prepared tooth structure are taken in the dental office and sent to a dental laboratory to be fabricated.
Gold remains one of the best restorative materials and most biocompatible, despite esthetic concerns.

78. Courtesy Dr. David Graham, San Francisco, CA.
Gold Crown
Figure shows a gold crown.
Displayed in the photo is a stone model of a patient’s maxilla with a full gold crown on tooth 3 before adjustment and final cementation in the patient’s mouth.
Courtesy Dr. David Graham, San Francisco, CA.

79. Gold-Noble Metal Alloys
Soft: Type I alloy
Used for casting inlays subject to slight stress during mastication
Medium: Type II alloy
Used for practically all types of cast inlays and posterior bridge abutments
Hard: Type III alloy
Acceptable for inlays, full crowns, three-quarter crowns, and anterior or posterior bridge abutments
Extra-hard: Type IV alloy
Designed for crowns, bridges, and cast-removable partial dentures
Ask students whether they have any gold jewelry with the carat marking visible on the inside. Note that a 10K or 14K ring is more durable than a 24K ring, which has a higher gold content.
One advantage of a type I alloy, used for inlays in areas bearing less stress, is that its margins can be burnished.
A type IV alloy is much more durable when used as a framework to support the acrylic base and teeth.

80. Ceramic Castings
Ceramics are compounds, which is a combination of metallic and nonmetallic elements
Ceramic castings are made of a claylike material with a glaze that has metallic components to make it durable and able to withstand temperature change
A ceramic material can be adhered to a metal casting, creating the “best of both worlds” in strength and esthetics
Ceramics were incorporated into indirect restorative options for a more esthetic result compared with the full metal crown previously shown.
The preparation design differs slightly, according to where metal, porcelain, or both may be sought in the final preparation.
Clinical cementing procedures and materials may differ, depending on whether the crown being cemented is made entirely of metal, of porcelain and metal, or of porcelain alone.

81. Ceramic Castings
Combinations of ceramic-metal restorations include the following:
Porcelain fused to metal (PFM)
Porcelain bonded to metal (PBM)
Ceramco-restorations (C/M)
Porcelain-metal (P/M)
The above are examples of restorations that are esthetically conscious, for the most part. They use a tooth-colored material on the outside and are reinforced with metal on the inside.
Porcelain-on-metal castings remain a popular choice for a full-coverage crown or a multiple-unit bridge, whereas all-porcelain crowns are being used more frequently now in the anterior region for esthetic purposes.
Remember to document the materials that were placed in the patient’s mouth in the patient’s chart.

82. Porcelain This is the type of ceramic most commonly used in dentistry
It combines strength, translucency, and the ability to match natural tooth color
These restorations are stronger than direct restorations, such as composite resins, which are created in the mouth
The ceramic porcelain is fused to a metal backing shell, then is fired and glazed to produce a highly smooth surface that is extremely hard and similar to enamel
More than one shade of porcelain may be used to create a more natural look, such as a darker shade near the gingival margin that gradually blends into a lighter and more translucent shade toward the incisal edge.
As an assistant, you will most likely be asked to help write the scripts for the dental laboratory when sending an impression off for the fabrication of a porcelain crown. Some offices now send or intraoral photos to their dental laboratory to aid in crown fabrication.

83. Porcelain Crown Figure 43.27 shows a porcelain crown.
The porcelain crown shown here is on a die of stone. The crown is fabricated as multiple layers of baked porcelain. The die is a replica of the prepared tooth that is being covered with a provisional restoration while the crown is being fabricated at the dental laboratory.
Although most indirect restorations are fabricated by outside dental laboratories using intraoral impressions of the prepared teeth, you may work in an environment that has a machine used to mill ceramic restorations in the office from a computer-generated reproduction of a prepared tooth.

84. Why Porcelain? The shading of colors matches tooth color well
Porcelain improves the esthetic appearance of anterior teeth
The material has the strength of metal
Porcelain is a good insulator
The material has a low coefficient of thermal expansion
Remember that shade selection for a porcelain crown should ideally take place in natural light, especially if the crown will be located in a region of esthetic concern. If a nearby source of natural light is not accessible, the ideal is outside the office.
Review: Porcelain has a low coefficient of thermal expansion. What would be a possible consequence if a material had a high coefficient of thermal expansion? (Answers will vary.)