Should etching be performed as part of a vital
bleaching technique?
by David A. Hall
originally published in Quintessence International,
Volume 22,
Number 9 (September 1991), pp. 679-686
Click here to find
books about cosmetic dentistry.
Abstract: Many clinicians advocate etching the teeth
before vital bleaching as a way to enhance the permeability of the tooth
surface to hydrogen peroxide and thus to enhance the bleaching effect.
However, no studies have been published to date to document the effect of
etching on vital bleaching. In this study, ten patients received a
bleaching treatment regimen of several appointments. Half of the teeth in
one arch of each patient were etched with phosphoric acid for 20 seconds
before they were bleached with 35% hydrogen peroxide. The teeth in the
other half of the same arch were treated with tap water prior to
bleaching. Evaluations of the patients after 3 and 6 weeks failed to
confirm any enhanced lightening effect from etching.
ARTICLE
(We have not reproduced the entire article
here but have
published an abridgement. Additionally, the original article was published
with photographs of all the bleaching cases, which are not included here.)
Introduction:
The bleaching of vital teeth is a procedure that has been
gaining in patient popularity as well as professional acceptance over the
past several years. The results have been pleasing to the patients, and
the techniques employed have proven to be conservative means of treating
tooth discolorations.
The oldest technique, introduced 20 years ago, involves
the application of concentrated hydrogen peroxide (eg, Superoxol, Union
Broach Co) to the teeth with cotton pledgets and then heat treatment with
a warming device. The heat accelerates the release of oxygen by the
peroxide, and it undoubtedly accelerates the bleaching action of the
oxygen on the tooth structure.
The newest technique involves the use of a solution of
carbamide peroxide in a gel. A splint is made to fit tightly over the
teeth of one arch. The gel is placed in the splint, and the splint is worn
for a number of hours each day for several weeks, depending on how much
lightening is desired. This system apparently relies on an extended period
of contact between the bleaching agent and the teeth to accomplish the
bleaching.
A third technique involves the use of a "bleaching light."
Concentrated hydrogen peroxide is applied to teeth that have been
carefully isolated with a tight rubber dam and etched with 37% phosphoric
acid. While the teeth are kept wet under a thin layer of gauze, the
bleaching light is placed 13 to 15 inches from the teeth. The light is set
initially at a medium intensity and later adjusted according to the
patient's reported sensitivity level.
Some clinicians have questioned the accepted vital
bleaching techniques and have pointed out the lack of controlled
scientific studies to establish the prudence of certain steps, the
effectiveness of the bleaching. or its long-term effects. This study
attempts to fill that void by examining the most controversial step in the
bleaching light procedure, etching the teeth prior to the application of
the bleaching solution. ....
Method and materials:
Ten patients were selected for this study.... An arch of
each patient's mouth was then selected for bleaching. This arch was
divided at the midline; one quadrant would be etched prior to bleaching
and the other would not be etched. ... The patients were randomly assigned
into one of two groups—in one group teeth on the left side were etched,
and in the other group teeth on the right side were etched. A small piece
of rubber dam material was placed between the central incisors to help
contain the etchant. To conceal from the patient which side of the mouth
was the experimental side and which was the control, the control teeth
were treated with plain tap water and this was rinsed off the teeth in a
similar manner to the etchant.
The bleaching procedure was followed for four to five
appointments, spaced approximately 3 weeks apart, for each patient.
Approximately 3 weeks after the final bleaching
appointment, each subject's teeth were evaluated by the operator. For this
evaluation, no review was made beforehand to learn which side had been
etched; thus the evaluation was done blindly. In addition, an independent
dentist, who had no other role in the study, was employed to give a
second, completely blind evaluation approximately 3 weeks after the first.
Each quadrant of the patient's dentition was graded for lightness against
the contralateral quadrant and the opposing quadrant.
Differences were graded qualitatively according to a rough
numerical scale: 0 = no difference; 0.5 = barely perceptible difference; 1
= perceptible difference; 2 = small difference; 3 = distinct difference.
The quantification of the differences was not regarded as critical to the
study—the objective of the study was to determine if there was any
difference at all, and if so, which side was lighter—the experimental side
or the control.
Results
Results were averaged by assigning a positive value to the
difference in lightness if the etched quadrant was lighter and a negative
value to the difference if the control quadrant was lighter. The sum of
these values was then divided by the number of patients.
In comparing the etched quadrant to the control quadrant,
the operator found the control quadrant to be lighter, on the average, by
a score of 0.2. Comparison of the bleached arch (using the lighter
quadrant, if there were a difference between the etched and control
quadrants) to the unbleached arch revealed that the bleached arch was
lighter by an average score of 2.6.
The independent evaluator found no net difference between
the etched quadrant and the control quadrant. According to the independent
evaluator, the bleached arch was lighter than the unbleached arch by an
average score of 2.8.
Discussion
The hypothesis of the author, in beginning this study, was
that etching the teeth as part of the bleaching treatment would enhance
the lightening effect of the bleaching. This study, however, failed to
corroborate that hypothesis. Those teeth that were etched sometimes
lightened slightly more and sometimes lightened slightly less than the
teeth that were not etched.
Even when the patients were separated into a group that
avoided staining substances during the bleaching and a group that ignored
this caution, there was no clear pattern. Not one patient was found to
have a distinct or even a small difference between their etched and
control teeth. One patient, patient 6, was evaluated by the independent
evaluator as having the teeth in the etched quadrant lighter by a
perceptible difference than the teeth in the control quadrant. According
to the evaluation by the operator, the difference in this patient and in
all the other patients were smaller or the control teeth were lighter.
Admittedly, the judgments of color value used in this
study are poorly quantified on a rather crude scale. This scale was
adopted on the premise that clinically significant differences of value
are clear, easily perceived differences. To the bleaching patient, the
bleaching effect must be at least perceptible, which is a number 1 on this
scale, preferably distinct, a number 3 on the scale, or even dramatic,
which is beyond the range of this small scale. Therefore, a barely
perceptible difference, with a value of 0.5, would not be esthetically
significant.
If there is indeed a benefit for some patients in an
increased lightening effect that comes from etching the teeth prior to the
application of Superoxol, conceivably the same benefit could be attained
by not etching and by increasing the number of bleaching sessions.
The potentially adverse effects of etching the teeth must
also be considered. If the teeth are etched, they have to be polished, and
polishing removes some enamel. The amount removed is not known. Clearly,
it would be desirable to retain as much of this glossy, fluoride-rich
surface layer of enamel as possible. Additionally, etching has the
potential to increase the sensitivity of the patient to the procedure.
Finally, in many states, etching is not a delegatable function. The time
required for the dentist to interrupt a procedure being performed on
another patient to apply the etchant is cost that needs to be considered
in the total fee for the procedure, in addition to the cost of the time
for the polishing.
In this study, where differences between the etched
quadrant and the control quadrant were perceived, the patient was offered
the chance to have additional bleaching visits and the treatments
reversed: to etch the control quadrant to not etch the quadrant that had
been etched during the study. However, none of the patients elected to
have this reversed procedure performed. None felt there was enough
difference between the quadrants to warrant any treatment.
Conclusion
Although the sample size of the study was too small to
draw any quantifiable conclusions, it is the opinion of the author that,
if potentially detrimental effects of etching and polishing the teeth are
weighed against the absence of a clear pattern of greatly enhanced
lightening, the weight of the argument is against the use of etchant.
More articles
America's Dental Bookstore maintains this collection of articles on dentistry submitted by visitors to our site. These
could be clinical tips, research articles, opinion articles, dental jokes, or
whatever. Do you have something you'd like to submit? If so,
click here to submit an article. |