CONTEMPORARY TRENDS AND TECHNIQUES IN TOOTH WHITENING: A REVIEW

The popularity of tooth whitening has increased with the advent of patient-applied, peroxide-based whitening agents, as well as increased media influence. Peroxides are considered effective and safe when used under professional supervision.

Whitening methods include those prescribed by a dental professional for the patient’s at-home use, those applied by the dental professional in the office, a combination of both, or methods available over the counter (OTC). This article reviews the effect of contemporary whitening agents and illustrates the clinical application of three methods prescribed by dental professionals.

Learning Objectives:
This article presents the use of three different types of whitening agents for improved aesthetics. Upon reading this article, the reader should be able to:

• Distinguish the difference between professionally administered in-office
and at-home tooth-whitening results.
• Identify the effects of whitening agents on dental tissues.

Practical Procedures & AESTHETIC DENTISTRY

New products and techniques that are less invasive to dental tissues are now being used to fulfill rising patient demands for aesthetics. The use of peroxide is now generally accepted as a safe and effective treatment for discolored teeth.1 When these discolorations compromise aesthetics, whitening may also be recommended before a clinician can perform an anterior bonded restoration
(eg, porcelain veneers and direct bonding).

Carbamide peroxide has been used as a bleaching agent since 1989.3 Using a concentration of 10%
carbamide peroxide, vital bleaching became a standard technique also known as “nightguard vital bleaching” (Figures 1 and 2). This technique (ie, at-home bleaching) allows the patient to use a tray whitening device at home, while the results and concentrations are monitored by a dental professional.

Figure 1. Preoperative appearance demonstrates severe

tooth discoloration in the maxillary anterior region.

Figure 2. Postoperative facial appearance following athome

whitening with 10% carbamide peroxide.

Other materials based on higher concentrations of hydrogen peroxide are also available for in-office power bleaching. More recently, polyethylene strips impregnated with 5.3% or 6.5% hydrogen peroxide (OTC concentration and dentist-prescribed concentration, respectively)
were introduced (Crest Whitestrips, Procter & Gamble, Cincinnati, OH).

Effects of Whitening Agents on Hard Dental Tissues

Carbamide peroxide has been used for many years as an oral antiseptic before it was applied as a gel for home bleaching.3,4 Numerous carbamide peroxide-based home bleaching products have been introduced in the last 13 years for use with the nightguard bleaching technique.
Carbamide peroxide is basically urea combined with hydrogen peroxide.5 Both products are released when carbamide peroxide breaks down in contact with saliva.


Initially, tooth bleaching with peroxides (both hydrogen peroxide and carbamide peroxide) was performed without a comprehensive understanding of the effects of the bleaching procedure on the structure and chemical composition of the enamel surface. More recently, studies
on enamel bond strengths and structural effects of peroxide-based materials on enamel have been undertaken.

5-7 Several studies have shown that hydrogen peroxide  and carbamide peroxide-based bleaching agents adversely affect the immediate bond strength of resins to enamel.5,8-11 Bond strengths to dentin treated with hydrogen peroxide for 60 minutes followed by 37% phosphoric acid for 60 seconds (and vice versa) were reported to be 0.0 MPa.12 Clinically, this decrease in bond strengths is relevant because whitening is often considered a preliminary treatment to improve the appearance of teeth prior to the application of a bonded restoration.

 Some authors have implied that the adverse effects of peroxides on bonding are caused by residual oxygen that inhibits resin polymerization, but roughening the surface eliminates this adverse effect. Surface analysis techniques have demonstrated that oxygen does not
accumulate within the near surface of enamel that has been bleached with peroxides. Consequently, the bond-strength reduction caused by bleaching with peroxide based whitening agents is not associated with the inhibition of resin polymerization by oxygen accumulated
within the enamel structure. The reduction in enamel microhardness after two weeks of whitening with 10% carbamide peroxide may be responsible for the decrease in enamel bond strengths, especially for gels with low pH.7 At four weeks, the decrease in microhardness was reversed.
The action of bleaching agents on enamel may be related to the fact that hydrogen peroxide is a strong oxidizing agent that can remove stains from enamel and dentin by oxygen-release mechanical cleansing. Bleaching agents may also cause alterations in the chemistry of hard dental tissues, inverting the ratio between organic and inorganic components and increasing
solubility. In a recent energy dispersive spectrometry study, the effects of 30% hydrogen peroxide on enamel were found to differ from the effects induced by two 10% carbamide peroxide-based materials. While 30% hydrogen peroxide resulted in a significant reduction in
the Ca:P ratio, neither a commercial 10% carbamide peroxide gel nor an aqueous solution of 10% carbamide peroxide resulted in significant changes in that ratio. Another study has shown that a 6-hour treatment of human enamel with 10% carbamide peroxide results in a significant loss of calcium compared with a water control, as measured with the atomic absorption spectrophotometer.

These alterations in the chemical composition of enamel may be transitory; their clinical relevance has not been determined. Effects of Whitening Agents on Soft Tissues The carcinogenic potential of whitening agents has raised some controversy. A court ruling resulted in a
ban of peroxide-containing tooth whiteners in the United Kingdom. Oxidative stress can induce damage in oral epithelial cells, resulting in premalignant changes. The application of hydrogen peroxide and DMBA (9,10-dimethyl -1,2-benzanthracene), a known carcinogenic analogous to those found in tobacco smoke, resulted in hyperkeratosis or carcinomas in the mucosa of hamsters after 22 weeks, depending on the concentration of hydrogen peroxide. A recent study, however, found that the chronic use of 35% carbamide peroxide did not result in alterations of the cell cycle in the oral mucosa of rats.

Practical Procedures & AESTHETIC DENTISTRY



Concerning the pulpal tissue, teeth that were scheduled to be extracted for orthodontic reasons were bleached with 10% carbamide peroxide for 4 hours or left untreated.29 No significant differences were found in the concentration of the enzyme heme oxygenase-1
(HO1) in the pulp. This enzyme HO1 is increased in cells subjected to oxidative stress.

Based on current information, it has been concluded that the use of dentist-monitored, at-home tooth whitening gels containing 10% carbamide peroxide carries no carcinogenic risk and does not cause irreversible damage to enamel.25,30 The safety of peroxides is corroborated by the inclusion of at-home vital whitening in the curriculum of the majority of dental schools in the
United States.

At-Home Whitening
Nightguard vital bleaching using 10% carbamide peroxide gel is the most common whitening method applied by the patient while supervised by a dental professional (Figures 3 through 7).

Figure 3. Preoperative evaluation demonstrates discoloration of tooth #8(11) following traumatic injury. Although the canal space within the compromised tooth was calcified, the tooth responded well to cold tests.

Figure 4. A resin spacer was added to the study model

over tooth #8 to facilitate development of a reservoir

within the whitening tray.

Figure 5. Two windows were cut in the areas corresponding

to teeth #7(12) and #9(21) so the teeth would not be

affected by the bleaching agent.

Figure 6. The whitening tray was tried in. Note the space
allocated for the whitening reservoir on tooth #8.

Figure 7. Postoperative appearance following 2 weeks of
whitening with 10% carbamide peroxide. Note the
increased aesthetics and harmony between tooth #8 and
the adjacent dentition

Studies have shown that whitening of vital teeth is very effective, durable, and safe. The literature has further indicated that peroxides diffuse quickly into dentin reaching the pulp chamber.
While tooth sensitivity seems to be the most common adverse event with carbamide peroxide whitening, sensitivity subsides with the termination of treatment.Sensitivity is generally associated with previous history of sensitive teeth, increased frequency of application, or the utilization of higher concentrations of carbamide peroxide (eg, 20%).45,46 Although sensitivity may be a
result of the potential of carbamide peroxide to penetrate the pulp chamber, the rate of penetration depends on the concentration and the commercial brand.

Another factor that may affect sensitivity is the pH of the bleaching gel. For whiteners used with the at-home technique, the pH is within a range of 5.66 to 7.35.
 Sensitivity is also directly related to the frequency of application of the gel — patients who change the whitening solution more than once a day report significantly more side effects than those who do not change the whitening solution.

Potassium nitrate and fluoride have recently been added to the composition of certain whitening gels to prevent sensitivity during treatment. One clinical study demonstrated that potassium nitrate and fluoride added to 10% carbamide peroxide gel reduced sensitivity over a 2- week treatment period when compared to a 10% carbamide peroxide gel without those two components. The use of reservoirs in the tray to allow for space to retain the bleaching gel is a controversial issue.

Despite the recommendation of some manufacturers as a light-cured block-out resin or a self-adhesive strip, the use of spacers to create reservoirs for the bleaching gel does not seem to increase the success of home bleaching. The bleaching gel, however, remains active for longer periods when reservoirs are used.

Power Bleaching
In 1918, a high-intensity light was first used to induce a rapid increase in the temperature of hydrogen peroxide and thereby accelerate the whitening process. Lasers and high-intensity lights have been recommended by some authorities for in-office bleaching despite the disappointing results obtained in some studies. Power whitening procedures are currently performed in-office
with concentrations of hydrogen peroxide in the range of 15% to 40%. (Figures 8 through 15).

Figure 8. Preoperative appearance demonstrates the presence

of tetracycline staining.

Figure 9. Right lateral view demonstrates severe staining

at the gingival regions in both the maxillary and mandibular

dentition.

Figure 10. Left lateral appearance demonstrates discoloration

throughout the entire buccal aspect.

Figure 11. The teeth were isolated with a rubber dam to

protect the gingival tissues during in-office whitening.

Figure 12. Four applications of the whitening agent were

administered. The whitening material was placed for 15

minutes per application.

Figure 13. Postoperative facial view following the initial inoffice

whitening session.

Figure 14. Note the harmonious whitening achieved

throughout the entire maxillary arch.

Figure 15. Lateral evaluation further verified lightening of

the previously discolored dentition.

 The most effective in-office whitening materials are those that include a chemical catalyst: LumaArch (LumaLite Inc, Spring Valley, CA; 35% HP, pH=5.5), Opalescence Xtra Boost (Ultradent Products, South Jordan, UT; 38% HP, pH=7.0); Zoom (Discus Dental, Culver City, CA; 25% HP, pH=7.9).56 When a chemical catalyst is added to the hydrogen peroxide immediately prior to bleaching, the oxygen is released rapidly, inducing the whitening effect. Both LumaArch and Zoom use light sources exclusively for the bleaching treatment.

For Opalescence Xtra Boost, the use of light is optional. Despite the recommendation, however, the application of light does not significantly affect the rate of decomposition of hydrogen peroxide for any of the three inoffice materials, as the whitening results are very similar

with and without irradiation with a light source. Heat accelerates the release of oxygen, but these power bleaching gels do not reach temperatures in the mouth high enough to significantly increase the decomposition rate of hydrogen peroxide.

The primary advantage of the in-office power whitening technique compared to the at-home technique with a nightguard is that the former is not dependent upon the patient’s compliance and the results can be appreciated by the patient in the same session during which the procedure is completed. On the other hand, in-office procedures require extensive tissue isolation and/or a resin barrier to prevent the gel from irritating the soft tissues.

Hydrogen Peroxide Strips
An OTC, 5.3% hydrogen peroxide-coated polyethylene strip (Crest Whitestrips, Procter & Gamble, Cincinnati, OH) was recently introduced to the market.
According to the manufacturer’s recommendations, the patient applies two strips per day for 30 minutes each. A similar 6.5% hydrogen peroxide-coated strip is available by prescription. Clinical studies comparing the whitening efficacy of 10% carbamide peroxide (which breaks down in 3.5% hydrogen peroxide) with the efficacy of the hydrogen peroxide-coated strips have demonstrated that the polyethylene strips may be an acceptable alternative to the nightguard method of athome
whitening (Figures 16 through 18).

Figure 16. Preoperative appearance demonstrates the

patient’s existing A2-shade. A slightly lighter shade was

desired at minimal cost.

Figure 17. The patient was instructed to use one whitening

strip for 30 minutes, twice a day for 2 weeks.

Figure 18. Postoperative appearance demonstrates slightly

whiter dentition with satisfactory results.

Other Methods
An 18% carbamide peroxide (equivalent to 6.5% hydrogen peroxide) paint-on liquid is also available as an OTC agent (Colgate Simply White Clear Whitening Gel, Colgate-Palmolive, New York, NY). While clinical studies have shown that this method can be effective, additional independent clinical studies are needed to confirm its long-term impact on this therapeutic category.

Another OTC paint-on liquid is now available (Crest Night Effects, Procter & Gamble, Cincinnati, OH) as a 19% sodium percarbonate bleaching film.

Conclusion
A variety of whitening options are currently available for patients seeking to enhance the appearance of their smiles. When suggesting a professionally administered whitening option, clinicians must be aware of the variety of options currently available. Based on the patient’s existing condition and desired whitening effects, in-office, athome, or OTC modalities can be used to safely and effectively address a variety of aesthetic concerns.

Acknowledgment
The authors do not have any financial interest or association with the manufacturers of the products mentioned in this article

TEETH BLEACHING- ILLNESS AND TRAUMA DURING TOOTH FORMATION

ILLNESS AND TRAUMA DURING TOOTH FORMATION 

TIle effects of illness, trauma and medica tion (e.g. porphyria, infant jaundice, vitamin deficiency, pheny j ketonuria, haematological anaemia) cumulative effect creating stains and defects, which cannot be altered by bleaching. Staining may result from haematological disorders such as erythroblastosis foetalis (Atasu et al 1998), porphyria, phenylketonuria, haemolytic anaemic, sickle cell anaemia and thalassaernia. As the coagulation system is affected, discoloration occurs due to the presence of blood within the dentinal tubules (Nathoo 1997). Bilirubinaemia in patients with liver dysfunction can cause bilirubin pigmentation in deciduous teeth (Watanabe et al1999).

STAINS AFTER ODONTOGENESIS 

(POSTERUPTIVE)

MINOCYCLINE 

Minocycline is a semisynthetic second-generation tetracydine derivative (Goldstein 1998). It is. a broad-spectrum antibiotic that is highly plasma bound and lipophilic (McKenna et at 1999). It is bact

antimicrobial activity than tetracycline or its analogues (Salman et al1985). The drug is used to treat acne and various infections. Its lipophilicity facilitates penetration into body fluids, and after oral administration the minocycline concentration in saliva is 30 to 6001;) of the serum concentration (McKenna et al 1999). Minocycline is absorbed from the gastrointestinal tract and combines poorly with calcium.

Those adolescents and adults who take the drug are at risk from developing intrinsic staining on their teeth, gingivae, oral mucosa and bones (Bowles and Bokmeyer 1997). It causes tooth discoloration by cheJating with iron to form insoluble complexes. It is also thought that the discoloration may be due to its forming a complex with secondary dentine (Salman et al 1985). The discoloration does not resolve after discontinuation of therapy.

The resultant staining is normally milder than that from tetracycline and may be amenable to bleaching and lightening, although it is case specific.

PULPAL CHANGES 

Pulp necrosis 

This can be the result of bacterial, mechanical or chemical irritation to the pulp. Substances can enter the dentinal tubules and cause the teeth to discolour. These teeth will require endodontic treatment prior to bleaching, the latter using the intracoronal method (see Chapter 8) or the outside/Inside technique (see Chapter 9).

Intrapulpal haemorrhage due to trauma Accidental injury to the tooth can cause pulpal and dentinal degenerative changes that alter the colour of the teeth (see Figure 1.14). Pulpal haemorrhage may occur giving the tooth a grey, non-vital appearance (Nathanson and Parra 1987). The discoloration is due to the haemorrhage, which causes lysis of red blood cells. Blood disintegration products such as iron sulphides enter the dentine tubules and discolour the surrounding dentine, which causes discoloration of the tooth (Baratieri et al 1995). Sometimes the tooth can recover from such an episode (Marin et al 1997) and the discoloration can reverse naturally without bleaching. These discoloured teeth should be vitality tested, because those that are still vital (see Chapter 4) can be successfully bleached using the home bleaching technique (see Chapter 5).

Dentine hypercalcification 

This results when there is excessive irregular dentine in the pulp chamber and. canal walls. There may be a temporary disruption in blood supply followed by the disruption of odontoblasts (Rotste.in 1998). Irregular dentine is laid down in the walls of the pulp chamber. There is a gradual decrease in the translucency of these teeth which results in a yellowish or yellow-brown discoloration. These teeth can be bleached with good results (see Chapter 9).

TEETH BLEACHING - TETRACYCLINE

TETRACYCLINE

Tetracycline is a broad-spectrum bacteriostatic antibiotic (van der Bijl and Ptitgoi-Aron 1995) which is used to treat a variety of infections. The tetracycline antibiotics are a group of related compounds that are effective against Gram negative and Gram positive

bacteria. It is well known that the administration of tetracycline during odontogenesis causes unsightly discoloration of both primary and secondary dentitions. The discoloration varies according to the type of tetracycline used (see Table 1.2). The staining effects are a result of chelation of the tetracycline molecule with calcium ions in hvdroxvapatite crystals, primarily in the "dentiJ1e (S'wift 1988). The tetracycline is incorporated into the enamel and dentine. The chela ted molecule arrives a t the mineralizing predentine-dentine junction via the terminal capillaries of the dental pulp (Patel et aI1998). The brown discoloration is due to photooxidation, which occurs on exposure of the tooth to light.

The staining can be classified according to the developmental stage, banding and colour (Jordan and Boksman 1984):

- First degree (mild tetracycline staining) is yellow to grey, which is uniformly spread through the tooth. There is no banding .

- Second degree (moderate staining) is vellow-brown to dark grey .

- Third degree (severe staining) is blue-grey or black and is accompanied by significant banding across the tooth .

-Fourth degree (intractable staining) has been suggested by Feinman et al (1987), designated for those stains that are so dark that bleaching is ineffective .

All degrees of stain become more intense on chronic exposure to artificial light and sunlight, The severity of pigmentation depends on three factors: time and duration of administration, the type of tetracycline administered, and the dosage (Shearer 1991, Dayan et al 1983).

First and second degree staining are normally amenable to bleaching treatments (Haywood 1997). Prolonged home bleaching has been reported in the literature to be successful for tetracycline cases. This may take between three and six months or longer . The bleaching material penetrates into the dentine structure of the tooth and causes a penl1anent colour change in the dentine colour (McCaslin et al 1.999).

TEETH BLEACHING - FLUOROSIS

FLUOROSIS 

This staining is due to excessive fluoride uptake with the developing enamel layers. The fluoride source can be from the ingestion of excessive fluoride in the drinking water or from overuse of fluoride tablets or fluoride toothpastes (Shannon 1978). It occurs within the superficial enamel, and appears as white or brown patches of irregular shape and form (Figure 1.7). The acquisition of stain, however, is post-eruptive. The teeth are not discoloured on eruption, but as the surface is porous they gradually absorb the coloured chemicals present in the oral cavity (Rotstein 1998). Staining due to fluorosis manifests in three different ways: as simple fluorosis, opaque fluorosis, or fluorosis with pitting (Nathoo and Gaffar 1995). Simple fluorosis appears as brown pigmentation on a smooth enamel surface, while opaque fluorosis appears as grey or white flecks on the tooth surface. Fluorosis with pitting occurs a.s defects in the enamel surface and the colour appears to be darker (Figure 1.7B).

Stannous fluoride treatment causes discoloration by reactions of the tooth with the tin ion (Shannon 1978). No intraoral discolorations occur from topical use of fluoride at low concentrations. The severity and degree of staining are directly related to the amount of fluoride ingested during odontogenesis.

DEVELOPMENTALLY DEFECTIVE ENAMEL AND DENTINE

STAINS DURING ODONTOGENESIS

(PRE-ERUPTIVE)

These alter the development and appearance of the enamel and dentine on permanen t teeth.

DEVELOPMENTALLY DEFECTIVE ENAMEL AND DENTINE 

Defects of enamel development can be caused by, for example, amelogenesis imperfecta (Figure 1.3), den tinogenesis i 111 perfecta (Figure 1.4) and enamel hypoplasia. The defects in enamel are either hypocalcific or hypoplastic (Rotstein 1998). Enamel hypocalcification is a distinct brownish or whitish area found on the buccal aspects of teeth (see Figure 1.5). The enamel is well formed and the surface is intact. Many of these white and brown discolorations can be removed with bleaching in combination with microabrasion (see Chapter 10). Enamel hypoplasia is developmentally defective
enamel. The surface of the tooth is defective and porous and may be readily discoloured by materials in the oral cavi ty. Depending on the severity and extent of the dysplasia, the enamel surface may be bleached with varying degrees of success.

TEETH BLEACHING - COLOUR OF NATURAL HEALTHY TEETH

INTRODUCTION 

Tooth discoloration is a common problem. People of various ages may be affected, and it can occur in both primary and secondary teeth. The aetiology of dental discoloration is multifactorial, while different parts of the tooth can take up different stains. Extrinsic discoloration increases with increasing age and is more common in men (Eriksen and Nordbo 1978); it may affect 3JO!c, of men and 21 % of women (Ness et a11977). The result is a complex of physical and chemical interactions with the tooth surface. The aim of this chapter is to assess the aetiology of tooth discoloration and the mechanisms by which teeth stain.

COLOUR OF NATURAL HEALTHY TEETH 
Teeth are polychromatic (Louka 1989). The colour varies among the gjngival, incisal and cervical areas according to the thickness, reflectance of different colours and translucency in enamel and dentine (see Figure 1.2). The colour of healthy teeth is primarily determined by the dentine and is modified by:

• the colour of the enamel covering the crown

• the translucencv of the enamel which varies with different degrees of calcification

• the thickness of the enamel which is greater at the occlusal/incisal edge of the tooth and thinner at the cervical third (Dayan et a11983).

concerning the exact definitions of these terms. Feinman et al (1987) describes extrinsic discoloration as that occurring 'when an agent stains or damages the enamel surface of the teeth, and intrinsic staining as occurring when internal tooth structure is penetrated by a discolouring agent. According to his definitions, the terms staining and discoloration are used synonymously. However, extrinsic staining will be defined here as staining that can be easily removed by a normal prophylactic cleaning (Dayan et al 1983). Intrinsic staining is defined here as endogenous staining that has been incorporated into the tooth matrix and thus cannot be removed by prophylaxis.

Some discoloration is a combination of both types of staining and may be multifactorial. For example, nicotine staining on teeth is extrinsic staining which becomes intrinsic staining. The modified classification of Dzierkak (1991) and Hayes et al (1986) and Nathoo (1997) will be used as a guide.

TEETH BLEACHING - ACKNOWLEDGEMENTS

ACKNOWLEDGEMENTS

It would not have been possible to write this are taken in their laboratory. Most of the book without the assistance of a considerable laboratory work shown is theirs. I should also number of people. 1 would firstly like to like to thank Keith Moore of Photo craft for acknowledge my patients who went through taking the interior photographs in the dental the bleaching procedures and treatments, surgery and treatment rooms.

Their comments and incidental findings have I feel most indebted to the contributing been helpful and honest and helped me authors, Dr George Freedman, Dr Valeria collate the information in the book. Gordan, Dr Martin Kelleher, Dr Gerald Unless otherwise stated, most of the lllus- McLaughlin and Professor Ilan Rotstein-all trations, tables, photos and slides are my experts in their fields-who have shared their own. However, as we in the UK have been unique expertise in the book. 1 should also legally only allowed to bleach teeth compar- like to acknowledge Professor Bernard G N atively recently, there may be a shortage of Smith, who encouraged me to undertake clinical cases presented. I am immensely original research into bleaching during my

grateful to Dr Ted Croll, Dr Dan Fischer, Dr master's degree (1990-2), and Robert Peden Valeria Gordan, Dr Van B Haywood and Dr of Martin Dunitz Publishers, who encouraged Martin Kelleher for the slides they have lent me to write this book and saw it through me to be included in the book. from an idea to final publication.

I should like to thank Dr Colin Hall Dexter Finally, I wish to thank my dental staff in who allowed me to adapt his patient question- the practice for their continual support, naire and charting form for my practice and Dr encouragement and dedication to improving, Eddie Levin for giving me further insights into building and striving for excellence in the the golden proportion and his special golden dental practice. I would also like to thank my proportion gauge. mother for encouraging me to open my own Thanks go to my dental technicians, Mick practice so that I could fulfil an ideal dream Kedge and Cliff Quince from Kedge and and for taking care of the babies while I vilas Quince Laboratory, for the help and assis- balancing building a busy practice with a
tance they have given me over the years. The young family.

photos of the making of the bleaching trays are taken in their laboratory. Most of the laboratory work shown is theirs. I should also like to thank Kei th Moore of Photo craft for taking the interior photographs in the dental surgery and treatment rooms.


I feel most indebted to the contributing authors, Dr George Freedman, Dr Valeria Gordan, Dr Martin Kelleher, Dr Gerald McLaughlin and Professor Han Rotstein-all experts in their fields-who have shared their unique expertise in the book. 1 should also Like to acknowledge Professor Bernard G N Smith, who encouraged me to undertake original research into bleaching during my master's degree (1990-2), and Robert Peden of Martin Dunitz Publishers, who encouraged me to write this book and saw it through from an idea to final publication.

Finally, I wish to thank my dental staff in the practice for their continual support, encouragement and dedication to improving, building and striving for excellence in the dental practice. I would also like to thank my mother for encouraging me to open my own practice so that I could fulfil an ideal dream and for taking care of the babies while I vilas balancing building a busy practice with a young family.