What is tooth whitening?
Whitening is any process that will lighten the existing natural
colour of your teeth without removing any of the tooth surface. This can be
achieved in two ways;
A product can bleach a tooth, which means that it actually changes
the natural tooth colour. Bleaching products contain peroxides that help remove
deep (intrinsic) and surface (extrinsic) stains.
Non – bleaching whitening products can be used which contain
agents that work by chemical or physical action to help remove surface stains
only.
How long has tooth whitening been used?
Tooth whitening has been practised by dentists for over 100 years.
The history of “modern day” tooth bleaching, however, began in 1989 and is
credited to Haywood and Heymann who introduced the nightguard method of vital
tooth bleaching. At the same time, Omnii International (USA), working with a
dentist named John Munro, developed and marketed the first commercially
available home-bleaching product to be used under dentist supervision.
Interestingly enough, this
system was initially discovered quite by accident by an orthodontist named
William Klusmier. He instructed a patient to use an oral antiseptic containing
10% carbamide peroxide in an orthodontic positioner, which the patient wore at
night, in an effort to facilitate tissue healing. The patient returned with
improved tissue health and, after using the product for an extended period of
time, his teeth were significantly lighter in colour. He began using this
technique to lighten teeth. From 1970 to 1975, Klusmier presented his findings
at several dental meetings. Haywood and Haymann attended one of these meetings
and initiated their clinical and laboratory investigations on the technique as
a result.
As with hair and skin colour, the colour of our teeth is
genetically determined and therefore varies between individuals. Our teeth tend
to naturally darken as we get older.
Teeth can be stained on the surface by food and drinks such as
tea, coffee and red wine. Tobacco smoking can also stain teeth. Acidic drinks
and foods such as fizzy drinks, fruit juice and yoghurt can cause the teeth to
appear more yellow as they cause erosion of the outer enamel layer allowing the
underlying yellow dentine to shine through.
Discolouration can also be caused by illness or the use of
tetracycline antibiotics while the teeth are forming. Minocycline, a
tetracycline antibiotic, can cause staining in adult teeth.
Deposits of calculus (tartar) that form around the necks of teeth
can pick up unsightly stains.
Who should decide if my teeth are suitable for whitening?
A thorough oral
examination, performed by a dentist, is essential to determine whether you are
a candidate for tooth whitening and what type of whitening system would provide
the best results. If tooth bleaching is the treatment of choice the dentist
will then administer or supervise the use of bleaching agents within the
context of a comprehensive, appropriate treatment plan.
Only a trained clinician can diagnose the type of stain present.
In some cases, it may be sufficient to whiten teeth by removing surface stains
with a thorough prophylaxis which involves polishing teeth with pumice.
What are the different options for tooth whitening?
Whitening products may be
administered or dispensed by dentists or purchased over the counter.
Professional bleaching is the most common and effective form of tooth
whitening. There are two techniques available for professional bleaching;
Dentist monitored home bleaching techniques.
In surgery bleaching techniques.
What do the different options for tooth whitening involve?
Home Technique
With this technique you bleach your teeth at home, under the
supervision of your dentist, using a tooth bleaching gel, usually 10% -20%
carbamide peroxide, which is held next to the teeth in a mouthguard.
Impressions of your teeth are taken by the dentist and a custom
made bleaching tray is constructed. The tray is lightweight, clear and fits
closely around the teeth to ensure that the bleaching gel can be applied to the
teeth without touching the gums. The dentist will show you how to put a small
amount of the bleaching gel into the tray and will demonstrate how to slide it
over your teeth.
You will then continue the treatment at home. The tray is worn for
several hours, usually at night time or when it is most convenient. A course of
treatment usually takes two weeks but may vary dependant on the concentration
of bleaching agent used. In cases of heavily stained teeth the duration of
treatment may be as much as six months.
Disposable trays pre-filled with 9% hydrogen peroxide gel which
can be adapted to fit around the teeth without the need for impressions have
also become recently available.
In Surgery Technique
This technique involves using either light-activated units for
‘power bleaching’ or lasers while you sit in the dental chair.
The dentist will apply a rubber dam or a gel to protect the soft
tissues, and a bleaching agent, usually containing 15-35% hydrogen peroxide, is
then applied onto your teeth. A light or
laser is then shone on the teeth to activate the chemical so that it acts more
quickly on the discolouring molecules within the tooth. The actual tooth whitening
procedure will take about one hour.
Before these tooth
bleaching techniques are carried out the dentist will make
a note of your baseline tooth shade using a guide so that it can
be compared with the shade after bleaching on your follow up appointment.
The success of these techniques is determined by the initial
colour of the teeth. Generally, bleaching easily removes yellow with dark brown
and grey stains being more resistant to the process. As younger teeth are more
porous it has been suggested that they would be easier to bleach than older
ones. With the home bleaching technique it is important to remember that
patient compliance with the dentists instructions plays a crucial role in the
success of the treatment.
What are the active ingredients in professional bleaching gels and
how do they work?
Bleaching gels contain either hydrogen peroxide or one of its
precursors, notably carbamide peroxide.
Carbamide peroxide breaks down into hydrogen peroxide and urea, with
hydrogen peroxide being the active ingredient.
The success of any bleaching treatment is based on the ability of
the bleaching agent to permeate tooth structure to the source of the
discolouration. Hydrogen peroxide has a low molecular weight and therefore
passes easily through enamel and dentine. Bleaching is an oxidation of the
discolouring molecules within the tooth. Peroxides release free radicals which
interact chemically with large organic pigment molecules contained in enamel
and dentine. These molecules are reduced into smaller, less pigmented
molecules.
How long does tooth whitening last?
Some individuals experience better effects from tooth whitening
than others. Tooth whitening should last for approximately 18 months to 3
years. At this point you may chose to have a touch up treatment and the colour
will usually change to the optimal shade readily. The effect is less likely to
last as long if you smoke, or eat or drink products that can stain teeth.
Is tooth whitening safe?
The evidence on safety published to date tends to suggest that
bleaching is a relatively safe procedure.
Hydrogen peroxide breaks down into water and oxygen. Urea breaks
down into carbon dioxide and ammonia. Normal body processes easily handle all
four products.
It has been suggested that
peroxides are mutagenic and can boost the effects of known carcinogens. The
American Dental Association (ADA), however, has found no evidence that when
used as directed, tooth whiteners increase cancer risk or cause other problems.
The ADA have acknowledged that bleaching products are abused by some members of
the public.
What are the side effects?
The most commonly observed side effects to hydrogen or carbamide
peroxide are tooth sensitivity to cold and occasional irritation of the soft
tissues in the mouth, particularly the gums.
Tooth sensitivity often occurs in the early stages of bleaching
treatment. In most cases, gum irritation is caused by an ill fitting bleaching
tray rather than the actual bleaching agent. Both of these conditions are
usually temporary and disappear within a few days of the treatment finishing.
The use of desensitising agents containing fluoride or different bleaching gel
formulations can address the sensitivity problem.
If you encounter any of these side effects you should consult your
dentist.
Will tooth whitening damage my teeth?
Over bleaching can cause teeth to become chalky and translucent.
Several studies have been carried out to investigate the reaction of
the pulp, which contains the nerve and blood supply to the tooth, to the
bleaching process. Evidence shows that bleaching may either have no effect or
may cause an initial, mild, localised pulp reaction which is reversible several
weeks post treatment.
There are no reports in the literature indicating that bleaching
may exert a negative impact on existing restorations. Defective restorations
should, however, be replaced before bleaching to minimise potential
sensitivity.
How much does tooth whitening cost?
Whitening treatments are not available from your dentist on the
NHS. Private charges will vary between practices and between regions. In
surgery bleaching techniques tend to be more expensive than dentist supervised
home techniques.
Patients are advised to contact their dentist to determine costs.
Existing crowns and fillings on the front teeth may also need to
be changed following the bleaching procedure which increase the overall cost.
How can I look after my teeth during and after whitening?
Personal habits may need to be modified to achieve and maintain
the desired goal of whiter teeth.
Teeth should be dry and cleaned of debris before any bleaching
agent is applied. During bleaching teeth may be slightly dehydrated and
consumption of food and drinks which can cause staining should be kept to a
minimum. These foodstuffs should also be kept to a minimum after tooth
whitening. Stopping smoking will also prevent staining of teeth.
What about whitening products bought ‘over the counter’?
Although cheaper, over the counter bleaching kits often contain an
insufficient concentration of hydrogen peroxide to be effective. Some may
contain acetic or citric acid as active ingredients. These acids have too low a
pH (too acidic) and can cause significant structural damage to enamel when used
for extended periods of time and worsen the discolouration through erosion.
Bleaching trays provided are not made to fit your mouth and can therefore cause
increased leakage and soft tissue irritation.
Whitening toothpastes do not affect the natural colour of teeth
but may be effective at removing surface (extrinsic) staining because they
contain abrasives.
Before you use a tooth whitening product you should consult your
dentist.
Are there any people for whom tooth whitening is not a good idea?
Individuals with a history of extreme sensitivity to hot and cold
food or drink, fracture lines in their teeth, large dental pulps, and severe
loss of enamel may not be suitable candidates for tooth whitening as the
procedure may precipitate sensitivity.
Decay, periapical lesions, and gum disease should be treated
before any tooth whitening procedure is carried out. Tooth whitening should not
be carried out on individuals with a peroxide allergy.
When might tooth whitening not work?
Tooth whitening only works on natural teeth and will therefore
have no effect on fillings, crowns, and veneers. If you have white fillings in
your front teeth, these should be replaced approximately 2 weeks post -
bleaching to ensure a good colour match and bond strength.
Very severe tetracycline stained teeth may not respond or have a
limited response to tooth whitening. In these cases, porcelain veneers may be
the treatment of choice. Mild to moderate tetracycline staining does, however,
tend to respond to extended bleaching regimes of 3-6 months. White fluorosis
spots do not tend to bleach but will become less obvious as a result of
lightening of the surrounding tooth area.
Can a single tooth which has been root filled be whitened?
Sometimes teeth become discoloured by the breakdown of tissue
inside the root canal when the nerve dies.
It is hypothesised that the blood in the pulp chamber undergoes
haemolysis, which releases haemoglobin. The iron in the haemoglobin then
combines with hydrogen sulphide, produced by bacteria to form iron sulphide,
which is a very dark pigment.
Provided a satisfactory root filling, hydrogen peroxide or sodium
perborate can be placed inside the tooth (internal bleaching) under a temporary
dressing. After a week, the bleach is removed and a permanent filling placed to
reseal the tooth. Internal bleaching can also be combined with external
bleaching.
Can I whiten my teeth while I am pregnant?
The effect of the bleaching gel on the foetus is unknown. You will
swallow some of the gel while you are bleaching with home kits. It is now
generally accepted to avoid unnecessary medical interventions during pregnancy
in order to minimise any possible risks to the health of the foetus.
History, safety, and effectiveness of current bleaching techniques
and applications of the nightguard vital bleaching technique
Introduction
The purpose of this article is to evaluate the safety of the
various techniques for bleaching teeth in general, and the newer nightguard
vital bleaching technique specifically, as well as provide examples of some of
the applications of the nightguard vital bleaching technique. Bleaching
techniques may be classified by whether they involve vital or nonvital teeth
and by whether the procedure is performed in the office or has an at‑home
component.
Hydrogen peroxide, in various concentrations, is the primary
material currently used by the profession in the bleaching process. Current in‑office
techniques for vital teeth and the "walking bleach" technique for
nonvital teeth typically use a 30% to 35% concentration of hydrogen peroxide.
The majority of the products currently on the market for the nightguard vital bleaching
technique use a 10% carbamide peroxide solution. A 10% carbamide peroxide
degrades into 3% hydrogen peroxide and 7% urea, and hydrogen peroxide can be
considered its active ingredient.The urea may provide some beneficial side
effects, because it tends to raise the hydrogen ion concentration (pH) of the
solution.Some products marketed directly to consumers, over the counter (OTC),
use 6% hydrogen peroxide solutions in a gel form.
Hydrogen peroxide naturally occurs in the body, even in the eyes,
in low concentrations. It is manufactured and regulated by the body, and often
involved in wound healing. In higher concentrations, it is bacteriostatic, and
in very high concentrations is mutagenic, possibly by disrupting the DNA
strand. However, the body has mechanisms for immediate repair of natural
damage, low concentrations of hydrogen peroxide do not cause serious problems,the
carcinogenic capabilities of hydrogen peroxide are more often caused by other
peroxide derivatives, and the body uses the peroxidisesand other mechanisms
for regulating hydrogen peroxide. Also, other conditions are often required to
allow action by hydrogen peroxide on cells. Because hydrogen peroxide occurs
extensively within the body, and because it has been used topically for many
years, it has been studied extensively. The understanding of the role of
hydrogen peroxide offers clues to understanding many of the body's actions at
the cellular level and to understanding the naturally occurring inflammation
and healing processes.
The mechanism of action of hydrogen peroxide in tooth bleaching is
considered to be oxidation, although the process is not well understood. It is
felt that the oxidizers remove some unattached organic matter from the tooth
without disolving the enamel matrix, but also may change the discolored portion
to a colorless state. There is some concern that continued long‑term treatment
will result in dissolution of the enamel matrix, but reports to date on
nightguard vital bleaching techniques have not supported this theory.
Tetracycline stains are more resistant to oxidation because the molecule is
tightly bound to the mineral in the enamel prism matrix during formation and
hence is less accessible to immediate action (Crenshaw M: Personal
communication). Teeth stained with tetracycline therefore require prolonged
treatment times before any results are demonstrated and often are unresponsive
to the procedure.
Generally, bleaching is considered an elective process, although
there are other indications that may make bleaching a necessity.
Safety over time
The first area to consider when evaluating safety is how long the
technique has been used, and the observations that have been made over that
time. Esthetic dentistry was a popular topic in the late 1800s, including such
present‑day concepts as recontouring of teeth; the portion proposed to be
removed was shaded with indict ink for patient approval. Recontouring and
bleaching were recommended procedures, along with gold inlays and porcelain
inlays, to avoid the waste of sound tooth structure by the casual crowning of
the tooth. Dentistry was in an era of affluence, and esthetics was a prime
consideration. Dentists were concerned that too many teeth were being crowned,
about the inappropriate use of base metal in restorations, about proper uses
of better pins in teeth, and about the need for better use of the rubber dam.
From the middle 1800s until early 1900, the reputable dental
journals contained 40 to 60 articles a year on tooth bleaching. The chemistry
seemingly was well understood, the eminent leaders of the profession conducted
experiments showing the safety of bleaching to the tooth, and the plea for
conservative dentistry and preservation of tooth structure was ever the
standard. Prominent dental leaders and editors of major textbooks gave lectures
supporting bleaching, and chapters or sections in operative dentistry textbooks
were devoted to this treatment. The discussions concerned whether or not
bleaching worked, the appropriate indications, how long it lasted, and the
relative safety of the various procedures.
Practitioners speaking against bleaching argued that it took too
long to occur and was too technique sensitive to perform. They argued that
because the teeth often reverted back to their original color, bleaching was
not worth the effort, and they would rather crown the tooth. Those
practitioners in favor of bleaching demonstrated the scientific approach to the
application of the different bleaching techniques to avoid failure and minimize
relapses, reported longevity averaging 6 to 25 years, and stated that
professional dentists gave the needed time to get the best, most conservative
treatment for their patients.
As early as 1848, nonvital tooth bleaching with chloride of lime
was practiced. Truman is often credited with introducing, well before 1864,
the most effective technique for bleaching nonvital teeth, which used chlorine
from a solution of calcium hydrochlorite and acetic acid. The commercial
derivative of this, later known as Labarraque's solution, was a liquid chloride
of soda. Numerous other bleaching agents were also successfully employed on
nonvital teeth in the late 1800s, including aluminum chloride,oxalic acid,
pyrozone (ether‑peroxide), hydrogen dioxide (hydrogen peroxide or perhydrol),
sodium peroxide, sulphorus acid, sodium hypophosphate, chloride of lime, and
cyanide of potassium. All these substances were considered either direct or
indirect oxidizers, which acted on the organic portion of the tooth, except for
sulphorus acid, which was a reducing agent. It later came to be recognized that
the most effective direct oxidizers were Pyrozone (Mc Kesson & Robbins),
Superoxol (Merk), and sodium dioxide, while the indirect oxidizer of choice was
a chlorine derivative.
The bleaching agents were categorized according to which stains
they were most effective in removing. Iron stains were removed with oxalic
acid, silver and copper stains with chlorine, and iodine stains with ammonia.
The stains of metallic salts from metallic restorations such as amalgam were
considered the most resistant to bleaching. Although cyanide of potassium would
easily remove such metallic stains, its use was not recommended because of its
being a very active poison. It was recognized that restorations were not
affected by bleaching, but the bleaching would remove the stains around margins
and under esthetic restorations that were leaking, giving them a longer
esthetic life. Earlier concerns of the profession about the potential
dissolution of teeth from the caustic nature of some of the materials had been
disproved by laboratory experiments and clinical observation.
Techniques that allowed the practitioner to perform the procedures
in-office or place the medicament and change it at subsequent appointments were
described. Sodium peroxide and hydrogen dioxide were used independently or
together to bleach teeth; sodium peroxide actually had the advantage of giving
the most natural translucency to the nonvital teeth. It had long been
recognized that some stains were more resistant to treatment than others, and
great care was taken during endodontic therapy to avoid allowing the pulpal
tissues to bleed into the chamber, since this caused the tooth to discolor.
Although most of the early dental literature focused on bleaching
nonvital teeth, vital teeth were also treated, as early as 1868, with oxalic
acid, and later hydrogen peroxide or Pyrozone. By 1910, these vital bleaching
techniques generally included the use of hydrogen peroxide with a heating
instrument or a light source. The steps to ensure patient comfort, including
the covering of the eyes, the number of appointments, four or five, and the
minimum of 3‑day intervals between appointments, as well as the favorable
prognosis, were well documented and recognized by the profession.
As early as 1893, it was common knowledge that a 3% solution of
Pyrozone (ether‑peroxide), the aqueous solution of hydrogen dioxide, could be
used freely as a mouthwash by both children and adults and that, in children
with pitted teeth, it had the beneficial side effect of reducing caries and
bleaching the teeth. It was reported that the 5% solution could be used in a
like manner to bleach teeth, but that the 25% solution, the most effective
bleaching agent, should be used carefully, to prevent contact with the soft
tissue, because of its caustic nature.
Since there were few manufacturing companies in the 1800s, most
dentists were excellent chemists, and mixed a variety of solutions in their
offices. When the manufacturing industry began to develop in the 1900s, this
versatility was lost to the profession, and the choices of materials to the
profession were limited to those offered by the manufacturing companies. Superoxol
was introduced by a manufacturing company early in the 1900s, and later became
the chemical used by the majority of dentists because of its safety, although
it was recognized that hydrogen peroxide bleaching sometimes left a yellow or
brown tinge in some teeth, which the other, previously used materials had not,
and that Pyrozone (ether‑peroxide) was the more efficient bleaching material.
From about 1913 until 1940, which included the time of World War
I, the Depression, and World War II, very little was written about bleaching.
However, articles began to appear in the 1940s and 1950s as the United States
began to recover economically, as communications improved nationally, and as
the profession began treating fluorosis, tetracycline‑stained teeth, and
discolored teeth saved by endodontic therapy rather than lost to extraction. In
the 1940s, hydrogen peroxide and ether were again used on vital teeth.
Pyrozone continued to be used effectively for nonvital teeth in
the late 1950s and early 1960s,52 as was sodium perborate. In the late 1960s,
Nutting and Poeelected to use Superoxol instead of Pyrozone, for safety, and
combined it with sodium perborate to achieve a synergistic effect. They
recommended use of Amosan (Knox Mfg Co), a sodium peroxyborate monohydrate,
because it released more oxygen than did sodium perborate. They also advised
that the guttapercha be sealed before the procedure was initiated.
Also in the late 1960s, a successful technique for home bleaching
using a 10% carbamide peroxide, delivered in a custom‑fitting mouth tray, was
discovered by Klusmier. Although he presented several table clinics at the
Arkansas State Dental Society and the Southwestern Orthodontic Society
(Klusmier B: Personal communication), this technique went relatively unnoticed
until Haywood and Heymann described the technique in March 1989 and a similar
product was introduced by a manufacturing company that same month. For the
first time, this technique offered the possibility of whiter vital teeth to a
wider section of the general patient population at a lower cost, with much less
danger and fewer side effects, than any of the previous options. Since that
time, numerous other products and techniques making claims for bleaching teeth
have been introduced. These options include variations on the dentist‑prescribed/home‑applied
techniques, as well as "bleaching kits" sold directly to consumers in
stores for unsupervised home use. The nightguard vital bleaching techniques
and the OTC bleaching kits have kindled a resurgence of interest in tooth
bleaching and have reopened the questions asked 100 years ago: Does it work, is
it safe, what are the indications, and how long does it last?
Current safety
Nonvital bleaching
The walking bleaching technique is probably the most popular
option for bleaching nonvital teeth, and no major problems of safety were
initially observed other than those associated with the handling of the
material and the potential for burns from the high concentration of hydrogen
peroxide. This technique involves sealing a mixture of 30% hydrogen peroxide
and sodium perborate in the pulp chamber and changing the solution every 2 to
7 days.
The in‑office alternative treatment for bleaching nonvital teeth
usually involves a single appointment in which 30% hydrogen peroxide is
activated by a heating instrument, which is more efficient. However, later in
the 1970s, external resorption was noted in the cervical areas of nonvital
bleached teeth. Early reports linked this to overzealous use of heating
instruments or to previous trauma to the tooth. Onset was 1 to 7 years
posttreatment, and the tooth was often lost.
Although the etiology of the resorption is still unknown, later
reports have questioned the heat and trauma theories and proposed that the
resorption may result from exiting of the peroxide through the tooth where the
enamel and cementum do not join. Approximately 10% of teeth do not have an
intact cementoenamel junction (CEJ). This theory, along with the observation
that pressure in the chamber often causes transient pain, reaffirm that a base
material should be placed, before the peroxide is inserted, over the exposed
root canal filler and over areas that might communicate with the CEJ. However,
placement of this base often means that a portion of the tooth that is discolored
will have to be masked with the base material and possibly will not lighten.
A significant drop in pH has been observed in the cervical area of
the tooth from passage of the peroxide through the tooth and its exit at the
CEJ. Later observations have indicated that the resorption is not actually at
the CEJ, but is more apical. This observation, along with experience gained
using calcium hydroxide in the treatment of resorption and incomplete root formation,
have led to the practice of filling the pulp chamber with calcium hydroxide
powder after the completion of the bleaching to alter the pH and halt the
potential osteoclastic activity. More recent reports have recognized the
greater potential for cervical resorption from the combination of heat and 30%
hydrogen peroxide over either treatment alone. For these reasons, the safer
nonvital bleaching technique appears to be the walking bleaching technique,
rather than the in‑office technique using a heating instrument.
Another approach to treatment involves using sodium perborate
alone, rather than in conjunction with hydrogen peroxide, as the primary
bleaching agent. Although this may be a slower process, it is potentially less
destructive to the tooth and hence safer.
It is unclear why these resorption problems should appear so late
in the history of nonvital bleaching, but their recent appearance raises the
possibility that changes in materials for root canal fillers, sealers, or
bleaching, or a wide variation by practitioners in administration of the
technique, may be the cause. At this time, the walking bleaching technique
seems reasonably safe, with only a slight chance of cervical resorption. The
benefit of treatment is relatively great (considering the cost of a crown or
veneer, the preservation of remaining tooth structure, the potential for an
esthetic outcome, the avoidance of a subsequent weakening of the tooth, and the
finite life of the other restorative possibilities), and the risk is small.
Precautions include sealing the root‑filled portion preoperatively with a
material such as polycarboxylate cement, placing calcium hydroxide powder in
the chamber postoperatively for 14 days, and following the patient for a number
of years with frequent recall radiographs. If there is any evidence of
resorption, it may be arrested with calcium hydroxide treatment, and the tooth
can be crowned (with or without extrusion of the tooth to manage the defect).
Vital bleaching
For any vital bleaching procedure, patients are classified by whether
they have tetracycline‑stained teeth, or teeth stained from other reasons.
Tetracyclinestained teeth are the least responsive to bleaching, depending on
the severity of the stain. With external bleaching, tetracycline‑stained teeth
generally get lighter, but not whiter. Some clinicians have recently advocated
intentional endodontic therapy on those teeth, with the use of the walking
bleach, to overcome this problem. While the esthetic result appears to be much
better than that of external bleaching, this approach raises questions about
the success of the endodontic therapy over time, the longevity of the walking
bleaching technique, and the potential of the treatment or retreatment to
cause cervical resorption.
The most popular technique for the in‑office bleaching of vital
teeth involves 35% hydrogen peroxide, etching the teeth with phosphoric acid to
facilitate bleaching, and either a heating element or a light source to enhance
the action of the peroxide. Because this technique must be accomplished
without anesthesia to allow the patient's pain threshold to determine the
appropriate heat level, there have been numerous studies on the effects of both
the heat and the concentrated hydrogen peroxide on the pulp. Although there is
insult to the tissue, most of the research has shown that the pulp remains
healthy, and the insult is reversible in approximately 2 months. The
observations of many clinicians who have performed this procedure over many
years attest to the fact that pulpal necrosis is not associated with vital
bleaching. Research in this area has shown how easily the hydrogen peroxide,
because of its low molecular weight, passes through the enamel and dentin to
the pulp.
More current clinical studies have eliminated the etching with
phosphoric acid, and the most recent products on the market advocate no use of
heat or light for the reaction.
A number of studies have evaluated the effect of bleaching with
this high concentration on dentin and enamel and have found some hints of
structural changes in tetracycline‑stained teeth. However, the most important
observation has been the decrease in bond strengths of composite resin to
bleached, etched enamel immediately after the bleaching process. Later studies
in this area have attributed the decrease to residual peroxide left immediately
in the tooth or on the surface.
The main safety advantages of the in‑office vital bleaching
technique are that, although it uses caustic chemicals, it is totally under the
dentist's control, the soft tissue is generally protected from the process, and
it has the potential for bleaching quickly in situations in which it is
effective. Disadvantages are primarily the cost, the unpredictable nature of
the result, and the unknown duration of the treatment. The unsafe features
include the potential for soft tissue damage to patient and provider, the
discomfort of rubber dam, the temperature on the pulp, and the resultant posttreatment
sensitivity. Although early concerns about pulpal response were identified,
subsequent research seems to have shown that although this high concentration
of hydrogen peroxide causes changes, they are reversible. If etching is
performed, polishing is required after each visit, with some enamel loss.
It is well accepted that this technique works, but the patient
must be counseled that, although the result may be permanent, the process more
likely will have a 1‑ to 3‑year duration, at which time the treatment will need
to be redone. Also, it cannot be determined prior to treatment whether the
teeth will respond, and treatment may take as many as four to six treatments.
The labor‑intensive nature of the treatment, which in turn requires a higher
fee, coupled with the discomfort to the patient and uncertainty of the outcome,
keep this method of bleaching from being a treatment that is widely accepted,
although it can be successful.
Recent innovations for in‑office bleaching include chairside‑mixed
gels, some of which are activated by composite resin curing lights (Hi Lite
Dual Activated Bleaching System, Shofu). According to the manufacturer, this
light‑activated material changes color when the bleaching process is completed,
which should take only 3½ minutes.
Chemical composition and effects on tooth structure of this technique are
unknown at this date. Other gel forms do not use heat or light. Although they
require approximately the same treatment time as the conventional Superoxol
bleaching technique, the gels are much easier to manage clinically.
Nightguard vital bleaching or dentist‑prescribed/homeapplied
bleaching
The most recently introduced vital bleaching technique, originally
called nightguard vital bleaching (NGVB), but also referred to as home
bleaching or dentist‑monitored bleaching, has created a resurgence in the area
of bleaching, primarily because of its relative ease of application, the safety
of the materials used, the lower cost, its general availability to all socioeconomic
classes of patients, and the high percentage of successful treatments. It may
be more appropriately termed a "dentist‑prescribed/home‑applied" technique.
Because the 10% carbamide solution is equivalent to a 3% hydrogen peroxide
solution, this solution is approximately one tenth the concentration of the
solutions used for "power," or in‑office, bleaching. Results are
generally seen in 2 to 3 weeks, and the final outcome is complete in 5 to 6
weeks. However, treatment times vary extensively, and much depends on the
amount of time per day that the patient chooses or is able to apply the
technique. Later products have offered solutions of hydrogen peroxide that
range from 1% to 10% and carbamide peroxide solutions that are either 10% or
15% concentration. The details of this technique have been reported in many
articles.
Numerous articles have attested to the efficacy of the technique,
which has been successful in clinical trials for approximately 91% of persons
with materially or genetically discolored teeth, and somewhat less successful
in 91% of persons with tetracyclinediscolored teeth. Tetracycline‑stained
teeth generally get lighter, but not whiter. Nightguard vital bleaching
generally has the same indications and prognosis as conventional, in‑office
bleaching, but can be accomplished at a much lower cost and with fewer side
effects, such as tissue burns and sensitive teeth, in the general patient
population. A recent survey of 7,617 dentists indicated a success rate of
greater than 90% for the technique; ninety percent of the responding dentists
use a 10% carbamide peroxide.
Specific questions as to the safety of NGVB were recently
addressed in an article by Haywood and Heymann. The controversial element that
the nightguard vital bleaching technique adds to conventional bleaching options
is the potential for contact of the soft tissue during treatment and from
ingestion of the material. This contact sometimes results in one of the two
common side effects, an irritation of the gingival tissue. More than half the
time, this irritation is related to an ill‑fitting prosthesis. Other times, it
is the tissue's response to the peroxide.
There are numerous reports of the effects of hydrogen peroxide on
tissue. However, those effects are generated by conditions that exceed greatly
the time and dosage of peroxide used in this bleaching technique. The
previously mentioned survey confirmed that one third of patients bleaching
their teeth in the home manner did not have side effects, while those that did
experienced either transient tooth sensitivity or gingival irritation. The fit
of the guard was a major cause of gingival irritation. Reports from industries
that make hydrogen peroxide state, "It is improbable that humans will be
exposed to high oral doses of H2O2 due to the acute toxicity of concentrated
solutions and the corrosivity of H2O2 to mucous membranes. An individual would
theoretically have to drink daily 23 mL of 35% hydrogen peroxide for a lifetime
to develop the lesions seen in mice." Hydrogen peroxide is approved as
safe for use as human food additive with no residues.
More recent studies directly evaluating the effects of 10%
carbamide peroxide on tissues and in animals systemically have indicated that
the effects of 10% carbamide peroxide on tissue are less than or equal to those
of many other accepted dental medicaments, such as eugenol, or other dental
procedures. The most conclusive evidence to date has been the work of
Woolverton et al establishing the nonmutagenic nature of 10% carbamide
peroxide, the safe level of ingestion, and the minimal effects on cell lines.
Even in tray designs that seek to avoid covering the attached gingiva, the
interdental papillae are still exposed to the solution. Hence, the total
avoidance of soft tissue contact is impossible as the technique currently
stands. Conclusions from evaluations of the other studies indicate that
toxicity and mutagenicity of hydrogen peroxide are dose related, and the
concentrations used in the at‑home bleaching technique are not of sufficient
strength to warrant concern about the soft tissue. In fact, although a high,
sudden dose of hydrogen peroxide is toxic to cells, a lower dose over a longer
time allows cells to adjust and actually ultimately tolerate a higher dose than
that which originally would have been toxic. Also the long history of clinical
usage of the solutions with soft tissue contact ranging from 7 days to 3 years,
in patients ranging from newborn infants to geriatric patients, has
demonstrated no problems.
Various effects of carbamide peroxide on teeth have been studied.
Generally, these reports find the effects to be nonexistent or to be no worse
than those already found with in‑office bleaching. Although there have been
varying reports concerning the effect on enamel, there does not seem to be a
significant effect on the morphology of the enamel surface outside the normal
variation of enamel. No published reports have demonstrated any change in
hardness of enamel, nor have studies at the University of North Carolina shown
any significant concerns. Studies that evaluate change in the surface must take
into account the remineralization potential in the mouth, which may negate any
potential changes. There has been one observation that toothbrush abrasion was
more significant in the presence of bleaching agents, while yet another
slightly different study showed brushing with the solutions had no effect.
Another report has shown the at‑home bleaching procedure to be a controlled
oxidation process in which the organic phase of the enamel is mobilized without
producing grossly unacceptable enamel surface topography. Clinically, there is
no apparent loss, and the tooth retains its glossy appearance. There have been
reports of internal matrix changes from bleaching with 35% hydrogen peroxide
after laboratory‑induced tetracycline staining, but there is no direct
correlation between this study and the milder hydrogen peroxide, nor have these
changes been demonstrated to have any clinical significance. Studies directly
on dentin and enamel with 10% carbamide peroxide materials have demonstrated
no structural loss.
The effects on the pulp were extensively evaluated in the previous
generation of bleaching with 35% hydrogen peroxide, and the lower concentration
of peroxide would not be expected to be as detrimental to the pulp. The effects
on pulp have not been directly evaluated with the weaker peroxide solutions,
but the research on 35% hydrogen peroxide has shown effects that are reversible
over time, with no clinical consequence other than immediate, but transient,
sensitivity. Clinical trials on nightguard vital bleaching techniques in
progress at the University of North Carolina have found no predictors of
sensitivity relative to patient age, pulpal size, presence of exposed dentin or
cementum, caries, or leaking restorations. The limitation for how young the
child is able to be treated is related more to the available number of
permanent teeth to retain the guard and the desire not to impede the eruption
of permanent teeth as they attempt to rapidly enter the oral cavity than to
pulpal sensitivity. The occasional mild tooth sensitivity associated with nightguard
vital bleaching is attributed to the easy passage of the hydrogen peroxide and
urea through the enamel and dentin to the pulp and the resulting mild
irritation. This ceases on termination of treatment. Because the concentration
of hydrogen peroxide is lower, certain patients that could not tolerate the in‑office
bleaching because of discomfort have found the nightguard vital bleaching
technique to be acceptable.
Effects on restorative materials have been limited primarily to
composite resins, both with color change and surface integrity. Basically,
there is no appreciable change in the color of any restorative material
clinically. Although there have been conflicting reports recently in this area
as to composite resins, the ability of the colorimeters to measure differences
is limited, and this color difference has not yet been calibrated to clinically
detectable changes. Clinicians must assume there will be no color change in any
material (although the stains may be removed from the surface and margins of
porous composite resins, etc), and patients should be advised of the potential
need for replacement of any esthetic restorations if the shade of the composite
resin is not clinically acceptable postbleaching. Reports of the dissolution of
a portion of the matrix have also concluded that it may be clinically
inconsequential. Since the composite resin may have to be replaced afterward,
any loss may be of no significant concern. Whether this bleaching technique
will have a significant effect on the long‑term wear of posterior composite
resins is still unknown, because other reports have shown that composite resin
hardens after exposure to bleaching solutions. Porcelain, amalgam, and gold
have not responded with either color change or alteration of structure, so
they are considered unchanged by the bleaching process.
Of current interest to the clinician is the effect of bleaching on
bond strength of etched enamel to composite resin. Earlier reports had
associated a decrease in bond strength of treated enamel to composite resin
with bleaching using 35% hydrogen peroxide. This occurrence has also been
confirmed with the 3% peroxide, but has been related to the residual oxygen in
the tooth, and the bond has been shown to increase, approaching the original
strength over time. More recent studies of the 35% in‑office bleaching
techniques have also attributed this loss to residual peroxide temporarily
remaining in the tooth or to surface changes. Another study of home bleaching
techniques demonstrated that roughening the surface slightly also eliminates
this phenomenon. Generally, etching and bonding should be delayed at least 14
days after termination of bleaching until further studies can determine a more
precise waiting time.
Safety to the occlusion and the temporomandibular joint during the
bleaching process must also be considered. Typically, occlusal problems during
NGVB may be mechanical or physiologic. Mechanically, the patient may occlude on
only posterior teeth, rather than on all teeth simultaneously. Sequentially
removing posterior teeth from the guard until all the teeth contact will
rectify the problem, and avoid the potential for joint disturbances. If the
patient exhibits bruxism, he or she usually will wear a hole in the appliance
over time, and another will have to be made. There has been no success to date
in fabricating an occlusal device for bruxism that can also serve as a well‑fitting
guard for bleaching. Physiologically, if the patient has pain in the joint, the
posterior teeth can be removed from the guard until only anterior guidance is
remaining, and the patient's wear time should be reduced or limited to the day
only.
Another area of concern with safety is how often the procedure
will have to be administered. Current research at the University of North
Carolina on longevity of the result indicates that, although the change may be
permanent, the patient will probably need re‑treatment in 1 to 3 years. It has
been noted that re‑treatment involves significantly less time than the original
treatment.
Over‑the‑counter bleaching kits
The newest systems that claim to bleach teeth are bleaching kits
sold directly to consumers. These kits are described as a three‑step process: a
15‑second pretreatment acetic rinse, a 1‑ to 2‑minute application of a 6%
hydrogen peroxide gel with a cotton swab on the facial surfaces of the teeth,
and an application of a tooth‑whitening pigment.
Early concerns have been expressed as to whether the process
actually works, especially as it is shown in television advertisements.
Although results shown in advertisements seem dramatic, the manufacturers'
literature reports that bleaching may take from 2 days to 2 weeks, and
sometimes up to 60 applications, for successful lightening. No reports from
dental studies have demonstrated any effectiveness. In a screening project for
the US Federal Trade Commission at the University of North Carolina,
administration of the OTC technique, on patients who had already successfully
bleached one arch with the dentist‑prescribed/ home‑applied technique in a
clinical bleaching study, did not effect any change after one, two, 14, or 60
applications. One report has shown that there is no harm to composite resins
from any of the bleaching agents, including this type of system.
A more disturbing concern relates to the safety of the material
and technique. A recent report cites the dissolution of enamel in a young
person using the technique. Although the person was also a heavy cola drinker,
this result raises the question of the safety of unsupervised use of a
treatment as well as the lack of baseline data. If the material is not
effective as a bleaching treatment, this lack of success could further foster
abusive use in an attempt to achieve results. In those patients who have other
problems resulting in dissolution of enamel, this could be an additional insult.
It may be this lack of proof of efficacy and safety with some
techniques that has prompted both the American Dental Association to advise
caution and the US Food and Drug Administration to issue warning letters to
manufacturers requesting data supporting their claims. Further determination of
both efficacy and safety of these OTC bleaching kits and other variations of
the conventional NGVB technique are certainly indicated. However, the ruling by
the US
Food and Drug Administration is directed toward manufacturers, and
does not restrict, limit, or affect bleaching treatments performed in a
legitimate dentistpatient relationship (US Food and Drug Administration:
Personal communication).
Relative safety of the nightguard vital bleaching technique
Safety of nightguard vital bleaching must be assessed relative to
that of the other bleaching techniques, but it also must be compared to the
safety of other accepted dental practices. With teeth, as with any living
tissue, there will always be a response to treatment. The questions are the
risk‑banefit of the treatment and what is known from observations and studies
on other dental treatments. The question of safety is always a doseover‑time
relation, as has been noted in the questions of fluoride toxicity and the
recent amalgam and mercury concerns. Other areas in dentistry are also
currently being examined for their safety. These indude concerns about the
nickel‑beryllium content of nonprecious metals, the carcinogenicity of nickel,
and the reported toxicity of Sargenti techniques.
As to the concern of the effect of materials on the pulp and other
tissues, it has been shown that one in five teeth that receive a crown will
need root canal therapy, 73% of the single pins placed in teeth cause a
fracture in the dentin that communicates directly with the pulp, and heat on
the pulp from restorations and direct provisional restorations has adverse
effects. Dentists observe postoperative pain from the cementation of crowns or
ceramic inlays with glassionomer or zinc phosphate cements, hypersensitivity
reactions to polyether impressions, and allergic reactions to the poly(methyl
methacrylate) acrylic resins. It has been shown that poly(methyl methacrylate)
is cytotoxic and produces non‑neoplastic lesions and that some glass‑ionomer
cements exude cytotoxic substances even after a hardening period of 48 hours.
In the more esthetic materials, it has been shown that all composite resin is
cytotoxic in its unset form and when incompletely cured, and some composite
resin is even cytotoxic if cured for less than 60 seconds. The cytotoxicity of
orthodontic adhesives has been demonstrated even after 2 years, and the
cytotoxicity of orthodontic solder joints to tissue has been shown. Recently,
Gluma 3 (Miles Inc) has been identified as a mutagenic agent, the cytotoxicity
of dentinal bonding agents has been demonstrated, and detrimental effects of
dentinal bonding agents on the pulp have been cited. Although the relative
thickness of remaining dentin determines the cytotoxic effects of composite
resin and glass‑ionomer cement on the pulpal tissues, it is impossible to know
how much dentin is present in the mouth. There is also the danger of damage to
the gingival tissues from indiscriminate use of the microabrasion technique,
as well as with the conventional in‑office bleaching techniques.
As to effects of other dental treatments on the surface of teeth
or restorations, 5 to 50 µm of enamel is removed during a prophylaxis and 5 to
50 µm of enamel is removed at banding and debanding of orthodontic appliances.
Hence, even a possible effect on the surface of enamel from bleaching may be
considered negligible compared to the 5‑ to 10‑µm loss of enamel from every
rubber cup prophylaxis over the life of a patient, including the loss of the
fluoride‑rich layer. Merely etching the enamel dissolves at least 10 µm in
addition to the 25 to 50 µm that is etched. Treatment with microabrasion to
remove stained enamel results in 12 µm of enamel loss with the first 5‑second
application, and an average of 26 µm of loss for every successive 5‑second
application. Acidulated phosphate fluoride, which contains hydrofloric acid, is
capable of etching porcelain in the mouth (Bayne S: Personal communication).
It has also been shown that judicious use of the Cavitron can remove resin‑bonded
fixed partial dentures or other cemented prostheses.
As to overall safety, it is reported that 8% of patients are
allergic to latex gloves. Studies on the previous effects of eugenol in
periodontal dressings on bone have resulted in a change in the formulation to
noneugenol‑containing periodontal dressings. However, no significant clinical
problems from the use of the eugenol‑containing periodontal dressings on soft
tissue has been identified in the literature. Detrimental effects of hydrogen
peroxide on the bone have been reported, but it is unlikely that the nightguard
vital bleaching techniques would ever be used in patients with exposed bone.
Recent reports have described the toxic effects of zinc oxide‑eugenol cement to
the pulp, the dangers and toxicity of sodium hypochlorite, the toxicity of
endodontic obturation materials, and allergic reactions to implants. This, in
conjunction with the radiation from normal exposure of radiographs, the
potential for an allergic reaction to local anesthetic, the hazards of eye
damage from composite resin curing lights, and the hearing loss caused by the
high‑speed handpiece, make dental treatment full of risk‑banefit judgments in
the light of current knowledge. Even the choice between a direct pulp cap or
endodontic therapy, between placement of another foundation or a casting, or to
remove a questionable restoration, which takes more tooth structure and weakens
the tooth, is subjective but significant in the long‑term safety and health of
the tooth.
One concern often expressed about the nightguard vital bleaching
technique is the potential danger of making bleaching materials available to
patients at home, where abuse may occur. It is important to distinguish
between nightguard vital bleaching (dentistprescribed/home‑applied), and OTC
kits available directly to consumers. In the "prescribed" method, the
materials are held in a custom‑fabricated guard, and approximately 1 to 2 oz is
used in a 4‑ to 6‑week period. If the patient uses more than 2 oz during that
time, the dentist should reevaluate the patient's application technique. The
availability of the dentist for monitoring, the slowness of the treatment, and
the contained environment reduce the potential for abuse. Clinical trials have
also indicated there is a level of lightness beyond which the teeth do not
pass. Hence the treatment is somewhat self‑limiting over time. Patients could
continue for extended periods of time, but at this time there is no clinical
evidence that this is occurring. There is always the potential for abuse by
some persons, but there is the same potential danger of abuse from ingestion of
fluoride‑containing toothpaste or rinses, alcohol‑containing mouthwashes, and
aspirin, even when these materials are correctly prescribed.
On the other hand, OTC kits place the consumer in a position of
diagnosing the reason for discoloration of their teeth, as well as prescribing
a treatment that has no professional evaluation of the baseline standard, the
side effects, or the results. Unsupervised or excessive use of any material has
potential for harm, especially in certain persons in whom the physiologic
status of the teeth and saliva or psychological status exaggerates otherwise
reasonable treatment responses. These effects are seen in the case of
toothbrush abrasion or the detrimental erosive effects of excess consumption of
carbonated drinks and fresh citrus fruits on enamel and dentin. Most unknown
about the OTC kits is the effect of the prerinse on enamel over time. Further
research and unbiased reports are needed to establish the appropriateness of
claims for both safety and efficacy. The safer option currently available is a
system where there is some establishment of indications for treatment by a
trained professional, baseline recording of data, fabrication and insertion of
a custom‑fitted mouthguard, monitoring of treatment, availability for
questions, evaluation of success or concerns, and instruction in application.
Some concern also has been expressed about the safety of wearing
the guard. However, the history of dentures, mouthguards for sports, Hawley or
Frankle appliances, orthodontic positioners, bite splints, and other occlusal
devices that have served dentistry so well over the years make this an
unreasonable concern.
Indications and applications for nightguard vital bleaching
The primary indication for the nightguard vital bleaching
technique has been for persons dissatisfied with the original color of their
otherwise sound teeth (Figs 1 and 2). Special concerns are for staining related
to ingestion of tetracycline as an antibiotic during tooth formation or as an
acne treatment during the teenage years (Figs 3 and 4). Other persons
interested in bleaching originally had lighter teeth, but now the teeth have
been darkened by age, coffee, tea, smoking, or other staining habits (Figs 5
and 6). Brown fluorosis stains are generally responsive, but white spots are
unaffected (Figs 7 and 8). Other motivations for treatment may warrant
consideration. These may include bleaching to avoid any of the developmental
personality changes in young persons who are ostracized by their peers for
having discolored teeth; persons in public contact areas whose appearance
greatly influences their success; or persons who are so dissatisfied with their
present appearance that they are considering more invasive procedures, such as
bonding, veneers, or crowns. In these instances, bleaching should be considered
as an alternative procedure, not as an elective procedure. Bleaching can also
prolong the life of unesthetic but otherwise acceptable dentistry.
Other indications include single teeth that have darkened from
trauma, but are still vital or have a poor endodontic prognosis because of the
absence of a radiographically visible canal. If all the other teeth are the
appropriate color, the section of the guard covering the adjacent teeth can be
removed so that material is placed only on the darkened tooth (Figs 9 to 11).
If all the teeth are slightly darkened, but one is still darker than the
remaining teeth, then a conventionalstyle guard is constructed and all the
teeth are bleached (Figs 12 and 13). Because it has been observed that teeth
lighten to a certain point, then maintain that color, the treatment is merely
continued on the darker tooth until it approaches or matches the other
lightened teeth.
Other options presented in the literature for treating the single
darkened tooth have included intentional endodontics or creating an artificial
pulp chamber and bleaching the tooth with the walking bleaching technique.
Because of the slight potential for cervical resorption, the loss of tooth
structure, and the less than 100% chance of success with endodontics, home
bleaching should be considered the first choice for altering the color of these
teeth.
Often the walking bleaching technique is desirable to ensure the
removal of debris and discolored restorative materials from the pulp chamber.
However, occasionally a tooth that has previously been bleached by the walking
bleaching technique and sealed with a finished etched composite resin will
discolor. In this instance, the first treatment considered should be bleaching
the tooth externally with the nightguard vital bleaching technique, especially
if the lingual access has since been covered by another restoration, such as an
etched‑metal, resin‑bonded fixed partial denture retainer (Fig 14). External
bleaching avoids unnecessary removal of an acceptable dental restoration, and
the loss of tooth structure during the process, which weakens the tooth, and
prevents additional insult to the cervical area from another 35% hydrogen
peroxide treatment. Even after successful treatment with a walking bleach,
often the bleached tooth is more yellow than the other teeth. Nightguard vital
bleaching then can be used to harmonize the colors of the vital and nonvital
teeth. Teeth that are endodontically treated, but have such a thin portion of
remaining dentin at the cervical area that there is concern about potential
cervical resorption from use of the 35% hydrogen peroxide, are also amenable
to the nightguard vital bleaching technique as the first choice of treatment.
The nightguard vital bleaching technique should be considered as
the first choice of treatment for any discolored teeth, even those considered
for the placement of porcelain or other esthetic veneers. Attempting
nightguard vital bleaching first may avoid the need for veneers. However, even
if the technique is unsuccessful in achieving the desired shade, or if there
are other indications for veneers other than the tooth color, bleaching may
lighten the underlying tooth base and make the subsequent veneer more esthetic,
as well as allow the patient to evaluate the results of the more conservative
option first. Home bleaching can be used prior to placement of single porcelain‑fused
to‑metal or ceramic crowns, fixed partial dentures, or removable partial
dentures to offer a lighter, youngerlooking shade, as well as to eliminate
some of the difficult crack lines or characterizations that are not easily
duplicated in ceramic restorations. Nightguard vital bleaching can minimize the
discoloration of the stained incisal edges of mandibular teeth and minimize the
effects of white‑spot lesions by lightening the tooth structure adjacent to the
white‑spot lesion.
Not only is nightguard vital bleaching effective as a preoperative
treatment, but it is also effective posttreatment to lighten natural teeth to
match existing ceramic crowns, fixed partial dentures, or Dicor restorations
(Dentsply International) (Figs 15 and 16). This lightening can be achieved to
match crowns to adjacent teeth in one arch or to teeth in the opposing arch.
Bleaching can also increase the longevity of threequarters crown abutments,
onlays, or resin‑bonded fixed partial denture abutments that have darkened more
than their originally matched porcelain poetic (Figs 17 and 18). Bleaching has
even been used successfully to increase the life of previous composite resin
bonding by lightening the underlying tooth structure to compensate for the
wear of the composite resin or to lighten the apparent color of veneers already
cemented by lightening the underlying tooth structure. This lightening effect
is due to the ability of the carbamide peroxide to pass freely through enamel
and dentin and to permeate to all parts of the tooth, even those protected by
restorations.
Although the success and acceptance of the nightguard vital
bleaching technique has been phenomenal, it has not eliminated the in‑office
bleaching. Some patients' lifestyles do not lend themselves to extended
treatment times, or outside‑the‑office appliances. Also, they may not be
willing to wait the time for home bleaching to be effective. They may not be
concerned about the greater financial investment of inoffice bleaching or may
not be able to wear the guard and tolerate the taste of the solutions used in
nightguard vital bleaching. In these situations, in‑office bleaching is
indicated. It is also indicated if the patient does not respond well to the
nightguard vital bleaching regimen. In clinical trials at the University of
North Carolina, a single in‑office bleaching treatment, delivered after a lack
of response to nightguard vital bleaching, followed by continuation of the
nightguard vital bleaching treatment, has achieved results that neither
technique showed independently. In those cases, the teeth were not etched, and
neither heat nor light was employed. Other recommendations include beginning
bleaching with the in‑office treatment, followed by the home treatment.
Other clinical pilot studies at the University of North Carolina
have shown reduction in the buildup of chlorhexidine stains when a 10%
carbamide peroxide is used in an alternating fashion with the mouthwash. Other
preventive opportunities being explored have included using the nightguard
vital bleaching system to attempt to reduce the incidence of root caries that
is unresponsive to traditional fluoride and tray systems. This caries is often
related to xerostomia and is a sequelae to radiation therapy, chemotherapy, medical
problems, or aging. There is hope to evaluate the nightguard vital bleaching
application in nursing homes or hospitals, where attendants may be able to add
this application technique to the oral hygiene regimen of patients with
inability to perform adequate oral hygiene measures.
Conclusions
The profession should neither propose a sweeping condemnation nor
offer a sweeping endorsement of bleaching any more than it should any other
treatment option or medicament used in dentistry. Bleaching techniques that
have been shown to be reasonably and relatively safe and effective, both in
current usage and over time, should be accepted as a reasonable treatment
option, knowing the risks and benefits. Continued research should be undertaken
on these and all other dental treatments. These accepted techniques include the
nonvital bleaching with 35% hydrogen peroxide and/or sodium perborate (but
without heat), in‑office vital bleaching with 35% hydrogen peroxide (but
without etching), and nightguard vital bleaching (dentist‑prescribed/home‑applied
bleaching) with 10% carbamide peroxide materials or similar products.
Conversely, claims that any use of hydrogen peroxide will bleach teeth and that
all techniques are safe cannot be accepted blindly. Especially in question are
the OTC bleaching kits and toothpastes containing carbamide peroxide.
Effectiveness and safety of the bleaching technique must evaluate not only the
product but also the delivery method and treatment time.
Unbiased research is still the best avenue for sifting through the
claims and reports to achieve a better understanding of what is correct and
what it incorrect. Over time, the understanding of temporomandibular joint
function has changed radically, the correlation between occlusion and pain has
altered, the change from pins to slots in amalgam restorations has occur red,
the noncrowning of anterior, endodontically treated teeth has been advocated,
and the nonposting of endodontically treated anterior teeth, unless the post is
needed to retain the preparation form of the crown, has been reported. So must
the dental profession be ever vigilant for changes that provide the most
conservative esthetic treatment options for patients. More importantly, the
profession should continually examine these treatment options in the light of
new evidence or techniques, always applying the same standards of safety to
all treatment options.
