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| Does bleaching the teeth really work? In a
word, YES! It has been done in one form or another for the last 100 years,
and it has proven itself to be safe and effective. The current popularity
of the bleaching process goes back only about 10 years, catching on with the
public fairly quickly, and with dentists much more slowly over that time.
The reasons that dentists have been less quick to endorse the process are very
interesting, and not what you would expect. I will cover this aspect later
in this piece, but first, you need to know a bit more about the process itself. |
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Exactly what gets bleached during the bleaching
process?
 The diagram to the right shows the internal
structure of a natural tooth. The layer you can see directly in
the mouth is the enamel layer which is the only portion of the tooth
that should lie above the gums. The natural color of enamel is
white, but it is translucent and the color of the other structures that
underlie it tend to show through. The material immediately under
the enamel is called dentin. It's normal color is yellow, but its
structure is porous, and materials from the nerve can permeate it
causing it to darken to a brownish yellow as we get older. The
color we see when we look at a tooth in the mouth is a composite of the
colors of the enamel which may permanently stain as we get older, and
the underlying dentin which darkens over the years due to its close
association with the underlying nerve.
This is the reason that simply brushing the teeth
will not prevent the teeth from becoming darker yellow as we get
older. You can brush all day, but you will not be able to brush away the
natural internal color scheme.
Enter bleach!
Root
canal treated teeth tend to be dark because the dead nerve which prompted
the root canal treatment turns a chocolate brown and permeates the surrounding
dentin before the dead material is removed during the root canal procedure. It was
discovered about 100 years ago that these teeth could be lightened up
substantially by temporarily sealing up a cotton pellet soaked with oxalic acid inside the access hole in the crown of the root canal treated
tooth. The cotton pellet was removed after several days and the access was
sealed with a filling. Hydrogen peroxide may have been used to lighten
teeth as early as 1884. In 1917, the process was speeded up using hydrogen
peroxide and a heat lamp. This is still the basic procedure used in some
offices today.
Later, it was discovered that even dark vital
teeth (teeth with live nerves) could be bleached by soaking the tooth in 30%
hydrogen peroxide. This stuff is 10 times more concentrated than the type
you can buy in the drugstore, and in order to use it safely, the dentist had to
isolate the dark tooth with a
rubber dam.
The peroxide could penetrate through the enamel into the dentin and bleach out
the dark color.
Finally, about 20 years ago, it was discovered
that a 10-percent carbamide peroxide solution (also called urea
peroxide) could be applied to the teeth safely
without fear of burning or otherwise damaging the mouth, or poisoning the
patient. This dilute solution of peroxide, if kept in contact with the
teeth long enough bleached the teeth to a brighter color. The longer the
contact, the brighter the teeth got (up to a point.....sooner or later, there's
no color left to bleach out.).
Is bleaching safe?
Most dentists now offer bleaching as an esthetic treatment for their
patients. The American Dental Association has published the following
statement:
"Dentist-prescribed, home-applied bleaching made by a reputable manufacturer and used under the supervision of a
dentist in a relatively short-term treatment duration is safe and recognized as most effective in lightening the color of teeth.
Bleaching materials that have received the ADA Seal of Acceptance are recommended.
Mild thermal sensitivity [sensitivity to cold] is a common side effect associated with most in-office and dentist-prescribed home bleaching
methods. However, no long term irreversible tissue effects have been demonstrated in relevant clinical studies."
Peer reviewed studies have found no irreversible
side effects from bleaching with 10 % carbamide peroxide.
The dental profession has recently begun to recommend carbamide
peroxide as a means of preventing periodontal disease and tooth decay in patients who
are unable to carry out normal oral hygiene measures such as regular brushing
and flossing. For patients like these, rubber trays are fabricated to fit
over both the teeth and the gingiva. The tooth indents in the trays are
filled with 10% carbamide peroxide and the patient wears the trays for two hours
once a day, or overnight. The carbamide peroxide breaks down into 3.5% hydrogen
peroxide and 6.5% urea when it contacts plaque. The urea further breaks
down into ammonia and carbon dioxide under the action of bacteria. The hydrogen peroxide
kills the oral bacteria, and the ammonia raises the PH of the plaque neutralizing
the acid that causes tooth decay.
Tooth Sensitivity
Bleaching solutions do cause your teeth to become
temporarily sensitive. In order to permanently bleach the teeth, the
solution must penetrate through the enamel to reach the underlying dentin.
(Click
here to see
a schematic diagram of the anatomy inside a tooth.) The dentin contains
microscopic tubules which allow the flow of cellular fluids between the living
nerve in the center of the tooth and the outer layer of enamel. This is
the reason that the teeth become sensitive. It would be logical to assume
that this process can't be too good for the health of the nerve, however, over
the course of the years that these bleaching products have been used, no ill
effects have been reported. The sensitivity goes away within a few days of
terminating the bleaching treatments, and the nerves in the teeth suffer no
permanent damage. The sensitivity, while temporary, in rare cases may be
severe and has been known to force some patients to terminate the bleaching
treatment early.
What bleaching can't do
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Bleaching will not bleach out the black, brown or
white color imparted to teeth due to
decay.
Teeth should be repaired before bleaching is performed.
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Bleaching will not bleach out
darkness
imparted to teeth by old amalgam fillings. Removing the old
metal filling and replacing it with a new composite will usually accomplish
this, but if the tarnish has penetrated deeply into the tooth structure, the
tooth may remain permanently discolored.
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Bleaching will not generally improve the appearance
of fluorosis if the patient grew
up in a part of the country (before the 1960's) that had a high
concentration of fluoride in the drinking water. This problem is also
prevalent in patients who "ate" a lot of fluoride toothpaste when
they were toddlers.
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Bleaching is ineffective in reducing the irregular
gray horizontal lines seen on patients with tetracycline stain in
their tooth structure. Tetracycline stain is seen primarily in older
patients who received tetracycline to treat ear infections when they were
infants and toddlers. Physicians in those days did not know that this
drug would incorporate itself into the developing teeth of children causing
this deformity.
The
different forms of dental bleaching
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Whitening toothpastes: These are
over-the-counter preparations that have a low concentration of carbamide
peroxide. These toothpastes will work to brighten your teeth if you
are a very
good brusher, brush
many times a day, and have a lot of patience. In the years since these
toothpastes have been on the market, I have seen only one person who
achieved real results using whitening toothpaste only. They are very
useful, however in maintaining the whitening achieved by using trays and
strips.
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Bleach releasing disposable
strips (Crest
Whitestrips): These are strips of plastic
designed so that they will adhere to the teeth.
They are applied and worn for several hours like the trays described
above. The carbamide concentration in home bleaching strips is only 7%
to 14% while professionally prescribed take-home bleaches come in either 22%
or 32%. Thus it takes a lot longer to get the same results using over
the counter bleaching strips than it does using professionally prescribed
bleaching solutions in trays. The main advantages to the strips is that no impressions need
to be taken to make trays, and the strips do not
apply pressure to the teeth which may increase the sensitivity of the
bleaching process. A number of my patients have tried
them. Some have had good results. The major problems I have heard about with the
strips is that they do not adhere very well to lower teeth, and they are too
short to bleach all the upper teeth that show when the patient smiles.
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Professionally supervised take-home bleaching with
custom made
trays: This type of system is available only through your
dentist. The bleaching material can only be bought with a prescription
and must be applied using the custom trays that the dentist or his hygienist
makes for
you. The agent is carbamide peroxide and it comes in concentrations
between 10% to 35% with 15% being the most popular for professional
take-home bleaching. Because of the high concentration of the agent, and the close
approximation with the teeth made possible by the trays, this system
produces very good results in anywhere from several hours to several weeks
of regular use. A drop of agent is placed in each tooth indent and the
trays are placed in the mouth for 30 minutes to an hour maximum. The carbamide
peroxide penetrates the enamel into the dentin and effectively bleaches the
teeth. Post-bleaching tooth sensitivity is a frequent
complaint, but it is transient and generally lasts no more than 24 hours.
The use of high fluoride concentration toothpaste (5000 ppm) such as that
found in the prescription toothpaste PreviDent used prior to, and throughout
bleaching effectively reduces the sensitivity. Alternatively, the use
of a 5000 ppm fluoride gel for 5 minutes in the bleaching trays after each
bleaching session can also reduced sensitivity. The patient can also
use amorphous calcium phosphate products (MI paste by GC America)
either in the trays for 3 minutes, or as a dentifrice twice daily.
Professionally supervised at-home treatment has the highest dentist
satisfaction rate of all bleaching methods offered with 94% being either
very satisfied or satisfied with the results.
In-office bleaching (Power bleaching): Some
offices offer a quick start bleaching procedure in which a concentrated
peroxide gel is placed on the teeth and allowed to remain in place while
"activated" with a light source. Treatments like this tend to be faster,
but they require a lot of chair time which means that they are likely to be
expensive. Prior to the introduction of at-home tray-bleaching
techniques, this was the only form of bleaching offered to the public.
The tray method can achieve the same or better results, (albeit over a
greater length of time) with the added benefit of total patient control of
the degree of bleaching desired. They can use the trays as long
as they want, and keep them around for touch-ups later.
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A note on Light or
laser bleaching: In-office bleaching systems use a gel made
with a 35% solution of hydrogen peroxide rather than the carbamide peroxide
used with trays or strips in the take-home systems. The hydrogen
peroxide gel is much stronger than the carbamide peroxide solutions used in
take-home systems, and it must be applied by dental staff because of the
potential to harm it could do to other oral tissues surrounding the teeth.
These strong hydrogen peroxide solutions offer very effective tooth
bleaching in about two hours on their own, however most dentists speed up
the process by using a heat or light source to liberate more oxygen from the
gel faster than would happen without the light or heat source.
Manufacturers of these solutions have managed to cut the time down to about
one hour, or in some cases even to a half hour if the light or heat source
is used to accelerate the process. On the other hand, retail
light bleaching kits that come with a flashlight-like device that
illuminates the tray (sold on TV, and recently in big-box merchandise
stores) are no more effective at whitening the teeth than using the low
concentration bleach that is sold with them without the light. They
are simply gimmicks. Stick with the Crest White Strips or go to a
dentist for the real thing.
How we make bleaching trays in the office
The first step in bleaching involves a thorough
examination, X-rays and cleaning. Bleaching diseased teeth is like painting
a rusted out old car. The owner walks away thinking he has a new car, but
finds out soon that he is no better off than before. It is not ethical for
a dentist to perform an esthetic procedure like bleaching in the presence of
curable disease!
It is important to be aware that fillings,
including white fillings in the front teeth do not whiten with bleach.
Therefore, if you have any
composite fillings in your front teeth, they
may have to be replaced after the bleaching process since the shade
of these fillings was chosen to match the teeth as they were before
bleaching. In practice, this is not always necessary.
The
second step is taking impressions of the upper and lower teeth so models can be made to
fabricate the bleaching trays. The major problem with impressions is that
people who gag may have a difficult time. The key to having impressions
taken is to be sure to breath only through your nose. If you breath
through your mouth during this procedure, you will have gagging problems.
I usually tell my patients to practice by opening their mouths wide, and humming, being sure that all the sound is coming out of their nose. When
performing this feat, the back of the tongue blocks off the throat, and since
the impression material cannot go any further down the throat than that, the
gagging reflex is suppressed. (This is really the same thing that happens
when you are chewing food which is why gaggers generally have no problems
eating. You will notice that when chewing food, you can hum at the
same time.)
Finally, you get your trays and the bleaching
kit, and go home and begin the process. The instructions vary slightly
according to the type and manufacturer of the bleaching kit, but you generally
wear the trays anywhere from several hours several times a day, to overnight for
as long as you want to keep the process up.
Are "over-the-counter" bleaching
methods as good as the kind you get from the dentist?
The results
you can expect from all of the over-the-counter methods are never as good as you
can get with prescription dental bleaching methods. The reason for this is
that the dentist can provide prescription strength bleach and custom bleaching trays that fit your teeth
tightly and keep the bleach in undiluted contact with the teeth for long periods
of time. Neither bleaching strips nor the stock trays provided
in the over-the-counter bleaching systems have either of these advantages.
The advantage to the availability of the dental
bleaching agents through sources such as the home shopping network is that once
you finish a prescription bleaching regime, your custom trays remain in your
possession indefinitely, and touchups, or continued bleaching can be done using
the prescription custom trays and the relatively less expensive bleaching agents
available from commercial sources.
The retail light bleaching kits that come with a
flashlight-like device that illuminates the tray (sold on TV, and recently in
big-box merchandise stores) are no more effective at whitening the teeth than
using the low concentration bleach that is sold with them without the light.
Click here
to see why.
So why did it take dentists so long to come
around?
In order to answer this question, it is helpful
to begin by reading my page on the
Nature of
dental practices. In fact, most dentists are not just out to make a
fast buck. If that were the case, there would have been no hesitation in
the acceptance of bleaching by individual dentists.
A substantial majority of general dentists are what I call
the "dentists in the trenches". Although we all do esthetic
work, the majority of our time is spent alleviating pain, curing infections,
saving bombed out teeth, teaching oral hygiene and generally making our patients
feel better about their mouths, and themselves. You could say that we are
really physicians who specialize in the mouth.
For me, and I suspect for a lot of the other
older guys who have been practicing dentistry in the trenches for so many
years, it was hard to work bleaching into our concept of what dentistry
means. We see dentistry as a branch of health care, but bleaching teeth
seems to fall more under the rubric of cosmetology. It seems more akin to
dying your hair, or applying fingernail polish. Thus, when it first became
apparent that there was a market for whitening teeth, many of us were reluctant
to integrate it into our concept of the meaning of what we do for a
living. "Teeth are supposed to be off-white, and they
are supposed to get darker with age. It's normal!" And
normality is what health is all about.
 What changed my mind was my hygienist, Jen.
She is, in fact, an esthetician who specializes in skin care. That's
what she did before she became a hygienist. (Note that teeth are
"dermal" structures, so she's really still in her
field.) She really really wanted to bleach teeth. So I bought the kits
and let her have at it. The first thing that struck me was how well it
worked. I had no problems telling who had bleached their teeth and who
hadn't. The second thing that absolutely amazed me was the sheer number of
patients who wanted to have it done. People who I had been treating for
years and who it never occurred to me would want to bleach their teeth were
showing up with teeth that fluoresced in the dark. And they were very very
happy.
So I realized that bleaching does fit into the
general concept of health.....mental health! When a person looks in a
mirror and likes what he sees, he feels better all over.
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