Patent Granted
GB 2 416 311 – Method and apparatus for whitening teeth
GB 2 416 310 – Bleaching tray for use in teeth whitening
GB 2 445 298 – Bleaching tray for use in teeth whitening
GB 2 416 309 – Method of whitening, shade and dehydration
GB 2 438 308 – Teeth whitening composition

Patent Pending
P5068PCT(US)  US 12/161 840
P5068PCT(CN)  200680051683.7
P5245PCT(EP)  07732838.3
P5245PCT(US)  12/301,110
P5245PCT(CN)  200780017736.8
P5424GB  GB 0817658.0
P5424W001  PCT/GB2009/002296

Research Paper IADR 2006
Paper presented at the International Association of Dental Research 2006 meeting in Brisbane, Australia.

0948 Bleaching of Tooth Discolouration Compounds by a Novel Chairside Gel
J. BLACKBURN, M. GROOTVELD, C. SILWOOD, and E. LYNCH, Queen's University of Belfast, United Kingdom

‘Browning products' (melanoidins) arising from Maillard reactions are at least partially responsible for extrinsic tooth discolouration (ETD). These reactions are triggered by the primary condensation of the free amino groups of amino acids and proteins with carbonyl compounds or reducing sugars. Objectives: In this study we have investigated the ability of a novel ‘in-office' tooth-whitening formulation [1] [containing 50% (w/w) hydrogen peroxide (H2O2) and a co-applied amino-alcohol bleaching activator and accelerant] to decolourise model brown-pigmented melanoidins. Methods: Melanoidins were produced from the reaction of 50.0 mM D-glucose with an equivalent concentration of L-lysine in 40.0 mM phosphate buffer (PB) solution (final pH 7.00). After allowing to cool at room temperature, each sample was diluted to a final volume of 1.00 ml with further 40.0 mM PB, treated with increasing concentrations of the H2O2-containing product component (equivalent to 10-80 mM H2O2), and the decrease in melanoidin absorption bands in the 250-600 nm wavelength range (ëmax. 300 nm) with time monitored spectrophotometrically. The influence of increasing added concentrations of the amino-alcohol accelerant (10-50 mM) was also evaluated. Results: obtained provided evidence for a time-dependent bleaching of browning products by product [1], and also that the rate and extent of this process increased with increasing H2O2 level. Moreover, both the rate and extent of melanoidin bleaching were substantially enhanced by the amino-alcohol activator [e.g., at an added H2O2 concentration of 20.0 mM, a 10.0 mM level of this agent gave rise to a decrease in absorbance at 350 nm (A350) of 45% at the 20.0 hr. time-point, whereas that for H2O2 alone was only 13%]. Conclusions: These data demonstrate that H2O2 in product [1] successfully bleaches melanoidins which serve as chemical models for ETD, and also that the accelerant tested markedly elevates its bleaching actions. [1] Wyten Professional Chairside gel, Smilestudio, London, UK.

Research Paper IADR 2008
Paper presented at the International Association of Dental Research 2008 meeting in Toronto, Canada.

A Comparative Spectrophotometric Investigation Of Selected Professional Tooth-Whitening Products
W. CHAN1, M.C. GROOTVELD1, E. TARASOVA2 and E. LYNCH3
1CMRI, University of Bolton, Bolton, UK, 2Department of Applied Science, London South Bank University, London, UK,  3School of Clinical Dentistry, Queen’s University Belfast, Belfast, N. Ireland

Introduction
Extrinsic tooth discolouration (ETD) can arise from brown-coloured melanoidins, products derived from the condensation reaction of reducing sugars or carbonyl compounds with amino functional groups contained in, for example, amino acids, peptides, polypeptides and proteins. These are termed Maillard reactions. The glycoproteins of the acquired pellicle serve as possible substrates for these processes.

The Maillard reaction is a general term used to describe a whole network of processes involving amino acids, reducing sugars, nucleic acid bases and sugar moieties, unsaturated fatty acids, nitrogen-containing vitamins, together with their derivatives including fragmentation products, either as single molecules or as polymers.  It provides the underlying mechanisms for some causes of, e.g., mutagenesis, carcinogenesis, protein molecule unfolding, cross-linking and denaturation, modified and impaired antibody-antigen reactions, specific enzyme inhibition, the promotion of growth of microbial pathogens such as bacteria, viruses, yeasts, fungi and protozoa, the suppression of growth of microbial non-pathogens, etc. The Maillard reaction is of much relevance to dental aesthetics, since many independent investigations have suggested that non-enzymatic browning has an aetiological importance in the development of extrinsic tooth discolouration.

Such processes involve condensation reactions of carbonyl compounds or reducing sugars with free amino groups. The latter can be typical a-terminal amino acid groups or the e-NH2 side-chain group of a protein’s lysine residue.  These reactions, in the first instance, yield  relatively simple premelanoidins.  Subsequent reactions are more complex and can yield a diverse range of soluble and volatile products ranging from straight-chain enol derivatives, carbocycles and heterocycles resulting from further reactions at the carbonyl and amino acid units, the separate fusion of carbonyl units, and subsequently simple addition polymers of  such cyclic units.  These products can then undergo further reactions and more complex polymerizations, yielding numerous brown-coloured, high-molecular-mass species (melanoidins or “browning products”).

Melanoidins can also arise from the interactions of carbonyl compounds regularly consumed in the diet. For example, reactive aldehydes generated from culinary oils that have been subjected to episodes of thermal stressing have been detected by high resolution proton (1H) NMR spectroscopy.  These may also play an important role in the discolouration of human teeth. Many commonly-administered antibiotics, anti-fungal and other anti-microbial agents have amino groups and/or carbonyl groups and consequently Maillard reactions may be partially responsible for their therapeutic activities, especially since many of them are specific enzyme inhibitors. Other sources of melanoidins include chlorhexidine, quinone species (derived via autoxidation of plant polyphenols occurring in beverages such as tea and red wine), together with acetaldehyde present in cigarette smoke.   

In this study we have evaluated and compared the bleaching efficacies of a series of professional H2O2–containing tooth-whitening products [Zoom!, and Zoom 2 (Discus Dental Inc., USA) and Wy10 Chairside Gel (Smile Studio UK, UK), products [1], [2] and [3] respectively] using model melanoidin browning products as spectrophotometric probes.

Materials and Methods
Model brown-coloured melanoidins were generated from the reaction of L-lysine (50.0 mM) with an equivalent concentration of a-D-glucose in 40.0 mM phosphate buffer (pH 7.00) at 60ºC for a period of 20 hr. After cooling to ambient temperature, 1.00 g quantities of each bleaching product evaluated, together with an H2O2-free control CarbopolR gel [2.00% (w/w)] was added to 3.50 ml aliquots of the above browning product solution re-heated to 35oC. Subsequent to centrifugation (5,000 r.p.m. for 5 min.), the clear supernatants were removed and equilibrated at 35oC for a period of 60 min. Following dilution (1/10), the absorbance   of the pre-treated and control supernatants was determined at 325 nm.  

The decrease in absorbance at 325 nm (ΔA325) achieved following 1.00 hr. treatment at 35oC was determined for each product tested and the control sample. The bleaching efficacies (ΔA325 . hr.-1 per 1.00% (w/w) of active H2O2 ingredient) was then calculated for each product. Each determination was conducted in triplicate. Statistical analysis of data acquired was performed by analysis-of-variance (ANOVA) on log10-transformed bleaching efficacy data.

Results
Mean (± SD) values for the tooth-whitening (bleaching) efficacies of products [1], [2] and [3] were 0.075 (± 0.0035), 0.068 (± 0.0041) and 0.114 (± 0.0051) respectively. Statistical analysis of log10-transformed bleaching efficacy data acquired revealed that product [3] was significantly more effective in its bleaching capacity than products [1] and [2] (p < 0.01, ANOVA).  No significant difference in this value was found between the latter two product.   

 

 

Conclusions
Hydrogen peroxide-containing tooth-whitening products effectively bleach brown-coloured melanoidins, agents which are known to contribute to extrinsic tooth discolouration. The mechanism of this process involves the H2O2–mediated oxidative consumption of these chromphoric chemical models. The greater effectiveness of product [3] is attributable to the incorporation of a novel amino-substituted alcohol accelerant/activator in this chairside gel. This accelerant may act by either (1) promoting the generation of bleaching-active •OH radical from its H2O2 precursor (Fenton reaction system) via its prior complexation of trace levels of ‘catalytic’ Fe(II) and/or Cu(I) ions present in the medium (a process involving favourable reductions in the redox potentials of the Fe(III)/Fe(II) and/or Cu(II)/Cu(I) couples, respectively), or (2) reacting with melanoidin browning products in a manner which facilitates the attack of •OH radical, HO2- and/or H2O2 on these chemical model staining agents.

Independent Studies
Our researchers are for obvious reason interested in studies done by other research institutions that have profound effects on our understanding of teeth whitening.  Here is a recent example.

In vitro efficacy and risk for adverse effects of light-assisted tooth bleaching
Ellen M. Bruzell, Bjørn Johnsen, Tommy Nakken Aalerud, Jon E. Dahl and Terje Christensen
Photochemical and Photobiological Science journal

The use of optical radiation in the so-called light-assisted tooth bleaching procedures has been suggested to enhance the oxidizing effect of the bleaching agent, hydrogen peroxide. Documentation is scarce on the potential adverse effects of bleaching products and on optical exposure risks to eyes and skin. The efficacy of seven bleaching products with or without simultaneous use of seven different bleaching lamps was investigated using extracted human teeth. The bleaching effect was determined immediately after treatment and one week later. Tooth surfaces were examined for adverse alterations after bleaching using a scanning electron microscope. Source characteristics of eight lamps intended for tooth bleaching were determined. International guidelines on optical radiation were used to assess eye and skin exposure hazards due to UV and visible light emission from the lamps. Inspection of teeth one week after bleaching showed no difference in efficacy between teeth bleached with or without irradiation for any of the products. Scratches, probably from the cleaning procedure were frequently seen on bleached enamel irrespective of irradiation. Maximum permissible exposure time (tmax) and threshold limit values were exceeded for about half the bleaching lamps investigated. One lamp exceeded tmax even for reflected blue light within the treatment time. This lamp also exceeded tmax values for UV exposure. The lamps were classified as low risk and as borderline to moderate risk according to a relevant lamp standard.