Composite shade guide and shade matching

Question 1

What are the three principles in the Munsell colour system?

Answer 1

• Hue: the types of colours in the wheel
• Value: is the degree of lightness or darkness of a colour (Black has value zero, and pure white has value 10)
• Chroma: Strength or intensity of a colour (For example, lemon yellow has a high chroma, while a banana yellow has lower chroma)

Question 2

List the factors that determine shade of CR.

Answer 2

Hue

Value

Chroma

Translucency

Opacity

Type and intensity of illumination

Metamerism

Contrast

Question 3

Describe translucency

Answer 3

Permitting light to pass through but diffusing it so that persons, objects, etc., on the opposite side are not clearly visible

Question 4

Describe opacity

Answer 4

Not able to be seen through

Question 5

Describe type and intensity of illumination

Answer 5

• Low light intensity – decrease value, increase chroma

* High light intensity – increase value, decrease chroma

Question 6

Describe metamerism

Answer 6

• When two colored samples will appear to be of the same shade under one light source but will appear to be different shades under a second source
• Composite matches under operating lighting but a significant difference is noted in photographs or normal work environment

Question 7

Describe contrast

Answer 7

• Contrasting colours found in the visual environment in can hinder the ability to accurately assess the shade of composite, such as wall colour, bib colour, lipsticks and inflamed gingival tissues
• Areal contrast (object of different sizes), spatial contrast (objects in foreground and/or background) and successive contrast (viewing an object immediately after another) can confuse the human eye when attempting to select the appropriate shade of composite resin

Question 8

Describe the shade matching procedure for CR

Answer 8

• Clean tooth with pumice and water to remove plaque and debris
• Avoid prophylaxis pastes that contains fluoride which may interfere with bonding to enamel
• Shade matching should use light source that best reflects natural daylight
• Direct test strips can be used to narrow down the composites of choice
• Prior to etching, place composites directly on the tooth in a thickness equivalent to the final restoration layer
• Light cure the composite, choose the appropriate shade, then remove composite
• Record shade on patient’s dental treatment record

Question 9

When it comes to a base, what type of GIC should you choose?

Answer 9

You would choose GIC with the highest degree of strength. Resin modified isn’t always the strongest.

Question 10

When you place calcium hydroxide?

Answer 10

If the placement of a sub-base is indicated, such as calcium hydroxide, only apply on the deepest spot, because it will reduce the area for adhesion of the glass ionomer

Question 11

How should CR be polished?

Answer 11

• The polishing abrasive particles must be relatively harder than the filler materials. Otherwise, the polishing agent will only remove the soft resin matrix and leave the filler particles protruding from the surface
• Aluminium oxide is significantly higher than most filler materials
• Remove excess by using finishing diamonds or tungsten carbide burs
• Expose the restoration to the curing light after polishing, it has been shown to improve mechanical properties including tensile strength and microhardness

Question 12

Do we use a slow speed bur to polish>

Answer 12

Due to the hardness of filler particles, polishing of CR with slow speed round bur is not recommended. The stainless steel particles from the bur will be scraped off by the filler particles, leaving the CR with grey scratches and discoloration

Question 13

How long do CR last?

Answer 13

Median age is around 5- 7 years

Question 14

What are common reasons for CR failing?

Answer 14

• Class I – secondary caries
• Class II – secondary caries, improper proximal contacts and gingival irritation
• Class III – discoloration
• Class IV – filling fracture or dislodged

Question 15

What are reasons for secondary caries and discoloration

Answer 15

Reasons for secondary caries
• Not all infected dentine was removed
• Micro-organism gained entry via leaky gap at the tooth restoration interface
• Resin shrinkage due to polymerization = bond failure
• Poor oral hygiene

Reasons for discoloration
• Microleakage at the tooth-restoration interface
• Inadequate acid etching of enamel

Question 16

How do you repair a CR restoration?

Answer 16

• Use a fissure bur to remove defective margin of composite resin restoration and recurrent caries from cavity margin
• Roughen the surface of the remainder of the restoration including the removal of the surface layer of material using a coarse diamond bur prior to application of fresh composite • Etch the repair surface and the remainder of the restoration
• Apply bond to the repairing surface and the remainder surface of the composite
• Restore with composite resin and check occlusion
• Review