REDM 105

Tooth-Whitening Materials

In tooth-whitening, a material is applied to teeth for a prescribed period as a means of whitening them.

 
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.

Indications for using Tooth-Whitening Products

• Discoloration of teeth
• Aging 
• Consumption of staining substances 
• Trauma 
• Tetracycline staining 
• Excessive fluoride 
• Nerve degeneration
• Old 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 wait longer to see results from whitening.

Tooth-Whitening Products

• Peroxide-based gel 
  • The peroxide breaks down and oxygen enters the enamel and dentin, bleaching the colored substances.
  • The gel comes in various concentrations.

In general, concentrations dispensed for at-home use are lower than those used for in-office tooth whitening.

Treatment Options

• In-office
  • Professionally applied
  • Fastest results
  • Most expensive
• At-home
  • Custom-fitted tray
  • Prescribed regimen
• Over-the-counter 
  • Strips
  • Paint-on solutions

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 postprocedure sensitivity.

Final whitening results appear a few weeks after the completion of treatment completion. At this time, nonmatching composite resins, veneers, and porcelain crowns are replaced with ones that match.

Indirect Restorations

Indirect restorations are created by a technician in the dental laboratory. These restorations are referred to as castings, which cannot be reshaped or carved once they are in this stage.

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.

Gold Alloys

• The combination of gold with other metals to form an alloy yields the characteristics and hardness required for an indirect restoration.
  • Gold
  • Palladium
  • Platinum 

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.

Gold Crown

This photo displays 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.

Types of Casting 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 possibly 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 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

Ceramics

Ceramics are compounds that contain a combination of metallic and nonmetallic elements, producing strength and an aesthetic appearance.

Ceramics were incorporated into indirect restorative options for a more aesthetic 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.

Types of Ceramic Restorations

• Porcelain fused to metal (PFM) 
• Porcelain bonded to metal (PBM)
• Ceramometal restorations 
• Porcelain-metal restorations (P-M) 

The above are examples of restorations that are aesthetically 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 aesthetic purposes.
Remember to document the materials that were placed in the patient’s mouth in the patient’s chart.

Porcelain

This is the type of ceramic most commonly used in dentistry. It is strong and translucent, and it can be matched to the natural tooth color.

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 laboratory scripts for the dental lab when sending an impression off for the fabrication of a porcelain crown. Some offices now send or e-mail intraoral photos to their dental labs to aid in crown fabrication.

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 labs 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.

Indications for using Porcelain

• The shading of colors matches tooth color well. 
• Porcelain aesthetically improves the appearance of anterior teeth. 
• It has the strength of metal. 
• The material 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 aesthetic 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?