Tooth whitening formulation and method

A tooth whitening formulation comprising urea peroxide (1:1) in a concentration of 22-32% based on the total weight of the formulation, in combination with a gelling agent, is provided in accordance with the present invention. The invention also provides a method for whitening the teeth using said formulation wherein the formulation is applied to the teeth using a splint which keeps the formulation in contact with the teeth for a period of time sufficient to cause whitening thereof.

FIELD OF THE INVENTION 
The invention relates to a tooth whitening formulation employing urea 
peroxide as active ingredient in a gel formulation. The invention also 
relates to a method of using said tooth whitening formulation. 
BACKGROUND 
There are several approaches available for bleaching and whitening teeth 
externally. Heat/catalyzed chemical procedures are well known. For example 
one technique involves vital bleaching of discolored or intrinsically 
stained teeth utilizing 37% phosphoric acid which etches the enamel, and 
then bleaching the teeth by applying 30% hydrogen peroxide to the tooth 
surface followed by heat application by a heating element. The time 
required will vary with tooth sensitivity. However, according to Bowles, 
et al., "Vital Bleaching: The Effects Of Heat And Hydrogen Peroxide On 
Pulpal Enzymes", Journal of Endodontics 12, 1084-112 (1986) both heat and 
hydrogen peroxide have been demonstrated to have deleterious effects on 
pulpal tissues. 
Other techniques involve the superficial removal of enamel with abrasive 
instruments or pumice followed by treatment with additional caustic 
agents. 
More recently, bleaching techniques suitable for home use have been 
developed. For example, Hayward, "Night Guard Vital Bleaching . . . ", 
Quintessence International 20, 173-177 (1989), describes a 10% carbamide 
(urea)/peroxide solution which is placed in a "Night Guard" and worn at 
night for several weeks to brighten teeth. According to Haywood, et al, no 
significant caustic chemical agents are used and only two short office 
visits are required to initiate treatment. This obviously provides a 
significant savings of cost and time for the patient. 
SUMMARY OF THE INVENTION 
It has now been found that a tooth whitening formulation employing between 
about 22-32% (w/w) urea/peroxide (1:1) as active ingredient in a gel 
formulation offers significant improvements over the tooth whitening 
procedures heretofore known. The tooth whitening formulation and method 
according to the present invention provides a more uniform lightening of 
the teeth from bicuspids to the incisors. Additionally, it has now been 
found that with the tooth whitening formulation and method according to 
the present invention it is possible to lighten teeth from the linguals 
when a plastic bonding has been put on the labial surfaces during previous 
treatments. It has been found that the gel formulation sits on the teeth 
and does not slip away. This permits the active ingredient to more 
uniformly penetrate the tooth to effect a more uniform lightening. 
According to the present invention about 5 cc of the gel formulation is 
applied into a splint and inserted over the patients' teeth. Any material 
that extrudes out of the splint is wiped away with a tissue. The patients 
wear the splint for a minimum of six hours daily, generally during evening 
and sleep hours. The procedure is repeated on a daily basis until maximum 
whitening or lightening of the dentition occurs.

DETAILED DESCRIPTION OF THE INVENTION 
The preparation of the tooth whitening formulation according to the 
invention will be set forth below. Unless otherwise indicated, all 
percentages are on a weight basis. 
A 22% urea peroxide solution is prepared as follows. Urea peroxide (1:1), 
Spectrum Chemical Co., 14422 South San Pedro Street, Gardenia, Calif., 110 
grams, is dissolved in 20 cc boiling water. Methylcellulose (400 CPS), 86 
grams, is dissolved in 60 cc boiling water and triturated until a smooth 
texture is obtained. The dissolved urea peroxide solution is added to the 
methylcellulose and triturated until uniform. Next, sufficient water is 
added to bring the total mixture to 500 cc. 
In similar manner, a 32% urea peroxide (1:1) solution is prepared following 
the foregoing procedure but, however, substituting 160 grams urea peroxide 
for the 110 grams used in the previous example. 
The method of the invention will now be described as follows. 
Impressions are taken on the maxillary and mandibular arch of a patient in 
need of tooth whitening to attain accurate models of the mouth. Initial 
photographs are taken with a static color from an existing shade guide 
used as a reference point. 
A custom clear acrylic splint is fabricated over the models of the teeth 
that are the target to lighten. This clear splint is 0.02 inches thick and 
covers the lingual and labial tooth surfaces. The splint is fabricated in 
known manner using a Stavac.TM. device, Buffalo Dental Co., 575 Underhill 
Boulevard, Syosset, N.Y. 11791. 
This splint is placed onto the teeth to verify a good fit and no creation 
of occlusal disharmony. 
Approximately 5 cc of the tooth whitener gel is applied into the splint and 
inserted over the teeth. Any material that extrudes out of the splint is 
wiped away with a tissue. Patients wear the splint at a minimum of six 
hours daily, generally in the evening and sleep hours. The tooth whitener 
is thus administered on a daily basis until maximum whitening or 
lightening of the dentition occurs. 
Surprisingly, it has been found that the tooth whitening gel in accordance 
with the present invention is capable of bringing about more uniform 
lightening of the teeth from bicuspids to the incisors than has heretofore 
been possible and penetrates through the tooth so that it is possible to 
lighten teeth from the linguals when a plastic bonding has been put on the 
labial surfaces during previous treatments. 
It is envisioned that urea/peroxide concentrations within the range of 
22-32% may be used to make the tooth whitening gel according to the 
formulation. In addition, other gelling agents as are known in the art may 
be used in place of the methylcellulose. 
It should be understood that the preferred embodiments and examples 
described are for illustrative purposes only and are not to be construed 
as limiting the scope of the present invention which is properly 
delineated only in the appended claims.