Walsh, Laurence J.

University of Queensland eSpace

48 Australasian Dental Practice March/April 2008
the cutting | EDGE
W ith the current strong levels of interest bypatients in reducing the aging-relatedyellow shades within their teeth by
bleaching, it is surprising that greater attention has
not been directed to other means of reducing yel-
lowness. This paper looks at the concept of “tooth
lightening” using simple in-office and supporting
at-home measures, as opposed to “tooth whitening”
using peroxides.
The concept is based on exploiting a number of
well-established optical properties of teeth, enamel
and water under visible light conditions. These are
presented step-wise in Tables 1-3 and the accompa-
nying Figures 1 and 2. The scientific foundations of
the tooth lightening concept rest largely on altering
the short wavelength (blue) scatter of enamel and
reducing its transmission of yellow light, although
there are minor accompanying changes such as
reduced red absorption which also occur.
The clinical stages in tooth lightening are as fol-
lows. Firstly, the reflection of light and the
backscatter of the shorter wavelengths of light are
enhanced by a gentle microabrasion procedure (ADA
Item 116) using 37% phosphoric acid etching for 20
seconds followed by gentle application of flour of
pumice or graded abrasive pastes at low rotational
speeds. The etching step enhances subsequent sub-
surface mineral changes. Patients then apply GC
Tooth Mousse Plus™ each night immediately before
bed for at least 2 weeks. The reduced yellow trans-
mission and increased backscatter of blue light from
the enamel will cause a subtle reduction in yellow.
The procedure can precede in-office or at-home
whitening treatments, to establish optimal enamel
properties and aesthetics, or can follow other cos-
metic treatments. Two typical cases are shown in
Figures 3 and 4. A variety of surface polishing
agents can be used to maximize reflectivity without
losing the natural surface contours.
Tooth lightening: a new concept 
for maximizing surface aesthetics
By Professor Laurence J. Walsh
“With the 
current strong
levels of interest
by patients in
reducing the
aging-related
yellow shades
within their teeth
by bleaching, it is
surprising that
greater attention
has not been
directed to other
means of
reducing 
yellowness...”
Figure 1. Simplified representation of the interac-
tions of light with enamel and dentine. At the tooth
surface, there is reflection and scatter, but limited
absorption. With transmission into the tooth, fur-
ther reflection, scattering and absorption events
occur. Selective enhancement of the shorter wave-
lengths of light provides the lightening effect.
Figure 2. Ground section of a human maxillary
central incisor tooth showing some of the major
interactions at the enamel and dentine boundaries.
March/April 2008 Australasian Dental Practice 49
Table 1. Optics of human teeth
• The light that penetrates the surface of a tooth and enters it is refracted due to the
fact that light travels faster in air, than in water or in solid apatite materials.
• Tooth colour is determined by the paths of light inside the tooth, and attenuation of
light along those paths.1
• Colours of natural teeth have a wide range (greater colour space) than represented
on existing shade guides,2,3 however yellow is the base colour which causes the
greatest distress when patients are asked to rate their own tooth colour. The human
eye is more sensitive to green and yellow light than to blue or red - because of the
numerical difference in cones (colour photoreceptors).4
• Both reddish and yellowish colours of natural teeth tend to increase from the incisal
to cervical, whereas translucency decreases. The middle and incisal thirds are the
most visible during speech and in normal function, and thus yellowness here attracts
the greatest attention.5
• While a significant yellow fluorescence emission is excited from enamel under vis-
ible blue or ultraviolet lighting conditions, this makes little contribution to the
perceived colour of natural teeth under normal “white light” lighting conditions.1
• Attenuation of light within the tooth is caused by several different factors, but pri-
marily by scattering and absorption. Scattering of light disperses it, without
changing the wavelength. Scattering can be forward or backwards in direction.
• Light is transmitted through enamel and dentine to the pulpal surface, with the light
following the path of the enamel prisms and dentinal tubules. Enamel and dentine
together collect and distribute light within the tooth.6
• Light bends when it moves through dentine, in other words, dentine is optically
anisotropic. Moreover, light propagation in human dentine exhibits a strong direc-
tional dependence.
• It was originally thought that both enamel prisms and dentinal tubules acted as
optical fibers,6 however it is now well established that the tubular structure is the
predominant cause of scattering in dentine.7,8
• Multiple scattering events occur within the dentine tubules due to its cylindrical
structure (and to a lesser extent by peri-tubular collagen fibers), and not by
fiberoptic effects, as had been previously assumed.9-12
Figure 3. Clinical case of a 26 year old female, showing immediately before and 
4 weeks after tooth lightening treatment, with blue pixel intensity data for tooth 11
showing an increase between the two. Note the bimodal nature of the pixel 
distribution in the “after result”, which occurs because of increased reflection of
light. Case taken from Ref. 15.
Figure 4. Clinical case of a 57 year old
male. A, Baseline image. B, After 
polishing disks were used on the 
maxillary central incisors. C, After fine
graded pastes were used. D, Second
appointment after using Tooth Mousse
for 4 weeks. E, Final appearance after
application of a surface coat of a 
protective nano-filled resin layer 
(G-Coat Plus). Note the even distribu-
tion of light from the tooth surfaces.
50 Australasian Dental Practice March/April 2008
the cutting | EDGE
References 
1. Bosch JJ, Coops JC. Tooth color and reflectance as
related to light scattering and enamel hardness. J Dent
Res. 1995; 74(1):374-80.
2. Schwabacher WB, Goodkind RJ. Three-dimen-
sional color coordinates of natural teeth compared
with three shade guides. J Prosthet Dent. 1990;
64(4):425-31.
3. Guan YH, Lath DL, Lilley TH, Willmot DR,
Marlow I, Brook AH. The measurement of tooth
whiteness by image analysis and spectrophotometry: a
comparison. J Oral Rehabil. 2005; 32(1):7-15.
4. Kennedy D, Milkman RD. Selective light absorp-
tion by the lenses of lower vertebrates, and its
influence on spectral sensitivity. Biol Bull 1956;
111(3):375-86.
5. Hasegawa A, Ikeda I, Kawaguchi S. Color and
translucency of in vivo natural central incisors. J Pros-
thet Dent. 2000; 83(4):418-23. 
6. Odor TM, Watson TF, Pitt Ford TR, McDonald F.
Pattern of transmission of laser light in teeth. Int
Endod J. 1996; 29(4):228-34.
7. Vaarkamp J, ten Bosch JJ, Verdonschot EH. Propa-
gation of light through human dental enamel and
dentine. Caries Res. 1995; 29(1):8-13.
8. Vaarkamp J, ten Bosch JJ, Verdonschot EH. Light
propagation through teeth containing simulated caries
lesions. Phys Med Biol. 1995; 40(8):1375-87.
9. Kienle A, Forster FK, Diebolder R, Hibst R. Light
propagation in dentin: influence of microstructure on
anisotropy. Phys Med Biol. 2003; 48(2):N7-14.
10. Kienle A, Forster FK, Hibst R. Anisotropy of light
propagation in biological tissue. Opt Lett. 2004;
29(22):2617-9.
11. Kienle A, Michels R, Hibst R. Magnification - a
new look at a long-known optical property of dentin. J
Dent Res. 2006; 85(10):955-9.
12. Kienle A, Hibst R. Light guiding in biological tissue
due to scattering. Phys Rev Lett. 2006; 97(1):181-4.
13. Spitzer D, Bosch JT. The absorption and scattering
of light in bovine and human dental enamel. Calcif
Tissue Res. 1975;17(2):129-37.
14. Odor TM, Chandler NP, Watson TF, Ford TR,
McDonald F. Laser light transmission in teeth: a study
of the patterns in different species. Int Endod J. 1999;
32(4):296-302.
15. Walsh LJ. Tooth Mousse: Anthology of applica-
tions. Singapore, GC Asia Dental, 2007.
16. Walsh LJ. White spots. Singapore, GC Asia
Dental, 2007.
17. Kleber CJ, Putt MS, Nelson BJ. In vitro tooth
whitening by a sodium bicarbonate/peroxide denti-
frice. J Clin Dent. 1998; 9(1):16-21. 
About the author
Professor Laurence J. Walsh is the tech-
nology editor of Australasian Dental
Practice magazine. He is also a noted
commentator on and user of new technolo-
gies and is the Head of The University of
Queensland School of Dentistry.
Table 2. Optics of human enamel
• Absorption of light by human enamel is low. In enamel, the organic (protein) 
component, mostly aromatic amino acids, is responsible for most or all of the 
limited absorption which occurs.13
• Yellow and red light are highly transmitted by normal enamel, and thus can 
both reflect from the dentino-enamel junction and transmit back through enamel to
the surface.14
• Scattering of light by enamel is high. This is critical, since while tooth colour is
determined mainly by dentine, enamel plays a significant role in modifying tooth
colour by scattering the shorter wavelengths in the visible blue range.1
• Reflectance of light from the enamel surface increases linearly from 400 nm (blue)
through to 600 nm (red).1
• Shorter wavelengths of visible light (blue and violet) have a much higher scatter
coefficient than longer wavelengths (yellows and reds). This is why visible blue and
violet wavelengths in the non-dental environment cause dazzle effects in rain, fog
and snow, and cause problems with glare.
• In enamel, it is the hydroxyapatite crystals themselves which contribute 
significantly to scattering, rather than the prism structure.7,8 For this reason, 
dissolution of crystallites or their incomplete formation will affect the scatter 
of light.
• The more porous the enamel, the less it scatters short (blue) wavelengths of light.
The more the enamel scatters blue light, the lighter it appears.1
Table 3. The influence of water present in the enamel
• Enamel contains 7-10% water by volume as one of its normal constituents, and this
water affects its ability to both absorb and scatter light.
• For early carious lesions and other enamel conditions with increased subsurface
water, longer wavelengths of yellow and red are preferentially reflected back to the
surface. This radiance change is mainly determined by the lack of mineral and the
increased water content in these lesions.7,8
• Even without the development of white spot lesions or altered enamel formation,
microscopic subsurface water voids are common as enamel is never perfectly min-
eralized. These water rich areas can undergo subsurface remineralization by
repeated topical application of CPP-ACP (Recaldent) products.15,16
• Restoring mineral to these water rich areas should, therefore, change the scatter 
of short wavelengths of light and thereby alter the appearance and colour of the
enamel surface. 
• Micropolishing the enamel surface makes tooth shade lighter and less yellow, and
this effect is enhanced upon air-drying, which removes subsurface moisture.17
• This provides a rationale for micropolishing in combination with subsurface 
remineralization.
CPD POINTS AVAILABLE
Continuing Education credits are 
available on this article for subscribers
by answering the questionnaire at
www.dentalpractice.com.au


Tooth lightening: a new concept for maximizing surface aesthetics

http://espace.library.uq.edu.au/view/UQ:139080/Mousse_Lightening.pdf

Tooth lightening: a new concept for maximizing surface aesthetics

Abstract

Similar works

Full text

Available Versions

University of Queensland eSpace