Enhanced Minimal Invasive Tooth Whitening

Keywords
Minimal Invasive Dentistry, Tooth whitening, White spot lesion, CPP-ACP, MI Paste

Abstract
This article discusses the philosophy behind the clinical protocols to achieve enhanced results in tooth whitening, and the successful reversal of enamel white spot lesions. External tooth whitening has long been recognized as having successful but variable results. An often-unintended consequence of external tooth whitening using oxidizing agents, is the enhancement of white hypocalcific areas (white patching), which if extensive appear unesthetic.

Understanding how different wavelengths of light are reflected from the teeth can allow enhancement of tooth whitening results. Achieving an increase in the enamel mineralization is a minimally invasive way of improving esthetic results and reducing white hypocalcified areas. This procedure is termed tooth ‘lightening’ and is achieved through the topical use of GC MI Paste Plus containing casein phosphopeptide-amorphous calcium phosphate, CPP-ACP, 900ppm fluoride. Treatment protocols, and clinical cases are presented to demonstrate these enhancements.

Introduction
The chemical action of peroxide products in external tooth whitening is well elucidated and understood, and modern tooth whitening has been successfully carried out by dentists for over fifty years. Often after seemingly successful tooth whitening procedures, the patient can be unhappy with the result due to an emphasis of existing white hypocalcific areas present on the anterior teeth. In some cases, a successful bleaching treatment conducted on teeth that are darker than the normal mid-range yellow shades can uncover underlying opacities that previously were masked. 1,2 These could be subtle areas of mild fluorosis or enamel hypocalcification that have been present in the tooth since it formed, or they may occur as the result of loss of enamel matrix proteins from oxidation. The latter has been termed “overbleaching”. 3 Residues of water from that process alter the refractive index and light scatter of the enamel, causing opacity to develop. 4 The coloured pigments used in some bleaching gels are unlikely to contribute to colour changes in the enamel. 5

This article describes a minimal invasive clinical technique for improving the appearance of these white hypocalcific areas, and the reversal of white spot enamel lesions in general. These are preferred over restorative approaches such as etching followed by placement of a resin veneer to mask the areas,6 or infiltration with resin to camouflage them. 7 In both cases, the resin makes further bleaching treatments later in the patient’s life problematic.

Use of peptide-stabilized remineralization technologies such as casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has been a useful approach for reversing development enamel opacities as well as those which are only noticed after bleaching. Even advocates of resin infiltration admit that the first choice of treatment is remineralization with various remineralizing agents such as ACP-CPP and fluoride. 8 Products which contain both (e.g. *GC MI Paste Plus, Tooth Mousse Plus (in Australia and New Zealand) and MI Paste One (toothpaste with ACP-CPP and 1100ppm fluoride) can reverse enamel white spot lesions as well as hypocalcific areas. 9-11 Of particular importance, the reversal of the appearance of the white spot lesion is permanent, resulting in enamel with normal lustre but superior resistance to further acid dissolution. This latter aspect is critical for situations where there are concerns regarding the integrity of the enamel, such as in cases of incisor hypomineralization. 12 Even such lesions can be treated with CPP-ACP with fluoride (CPP-ACFP), and show improvement in their mineral content, as well as their appearance. 13

When used separately, the remineralization patterns produced by CPP-ACP and fluoride are quite different. CPP-ACP achieves remineralization of enamel subsurface lesions, while the effects of topical fluorides are mostly on the surface, and not within the body of the lesion. 13,14 This is why using CPP-ACP is important for achieving fully remineralized areas that not only have better aesthetics and strength but are more resistant to a subsequent acid challenge.

Both authors have been using CPP-ACP with fluoride (MI Paste Plus, Tooth Mousse Plus) for the past decade to augment bleaching treatments and have found that application of this topical crème can greatly improve aesthetic results after tooth whitening. 15 To understand how CPP-ACP can enhance tooth esthetics, some key aspects of the optics of teeth and the process of bleaching teeth are important to stress. Yellow is the color of teeth which patients most dislike, however with aging the teeth appear more yellow. 16 The color of the inner dentin is more obvious because of less scattering of light in the enamel, because of subtle progressive changes, particularly from the accumulation of calcification in the enamel inter-rod spaces. 17 In older patients, the enamel thickness may also be less due to non-carious loss of tooth structure. Together, these alterations in the enamel alter the way that light is scattered by the enamel prisms, and then reflected from the dentin. 18 Yellow light is well transmitted by normal enamel, and thus can reflect from the dentino-enamel junction and transmit back through enamel to the surface. 19-21 Scattering of light by enamel modifies tooth colour by scattering the shorter wavelengths in the visible blue range. 18 Altering the crystal structure of the enamel surface changes the light scattering, particularly for the shorter visible blue and violet wavelengths of light. 15,20 By having optimal formation of enamel mineral on the surface by using CPP-ACP, blue light reflection is increased. This counteracts the transmitted yellow light, giving teeth a less yellow appearance. 15 Using CPP-ACP in this way to treat normal enamel gives a useful improvement in tooth shade (a less yellow appearance) whilst at the same time reversing areas of hypocalcified enamel. 22,23 This is why the technique for treating normal enamel has been described as ‘tooth lightening’. It is distinct from bleaching, as it does not involve the use of oxidizing agents such as hydrogen peroxide.

It is possible to use CPP-ACP before conventional at-home or in-office bleaching, or to follow bleaching with CPP-ACP. The authors have used both approaches successfully. In the former case, it is used to reverse enamel defects and thus provide a more consistent platform of tooth colour for later bleaching. In the latter case, it can be used to address white spots that develop during or become more apparent after bleaching.

Traditional approaches to bleaching using hydrogen peroxide or other oxidants are based on the concept of irreversible oxidation of stained molecules (chromophores) within teeth. In-office products have a high concentration (typically 37.5% hydrogen peroxide), while home treatments with custom home trays use lower concentrations of hydrogen peroxide or carbamide peroxide. Traditional bleaching methods are quite successful with patients with yellow teeth shades, but are less effective, in the experience of the authors, for dark brown or grey-shaded teeth. These may contain chromogens such as sulphides that respond poorly to oxidation. There may also be molecules present that are very resistant to peroxides, such as in the case of staining from first generation tetracycline antibiotics, where the teeth have a banded appearance. Such teeth can however be treated using photodynamic therapy where photo-oxidation is used to cleave the complex formed between the antibiotic and apatite minerals. 25 Regardless of the bleaching method that is being used, the “tooth lightening” techniques described below using CPP-ACP with fluoride can be employed to enhance the end result that can be achieved.

Tooth lightening involves patient home application of a pea-sized amount of GC MI Paste Plus using their finger across the surface of the teeth. This is done each night before bed, leaving the material in place on the teeth to interact with the saliva. If done prior to bleaching, it will reduce white spot lesions and also diminish any pre-existing symptoms of cervical dentinal hypersensitivity. 26

The case shown in Figure 1 demonstrates the effects of 10 weeks of nightly application of GC MI Paste Plus. There are noticeable improvements in tooth shade, with the teeth appearing whiter and less yellow, without any additional applications of tooth bleaching agents. There has also been reversal of small hypocalcific areas, especially on the incisal edges. This is a desirable improvement in this 24-year-old female patient.

Such treatments may be followed with traditional bleaching, to enhance the end result that can be achieved (whether using in-office methods or at-home gels).

Fig. 1

Clinical Protocol for Enhancing Tooth Whitening

1. For two weeks prior to the in-office bleaching treatment, each night a pea size amount of MI Paste Plus is applied across the labial surfaces of the anterior teeth, using a clean fingertip to smear the crème over the teeth. This should be done after toothbrushing, immediately before bed. Spit out but do not rinse afterwards. If the patient has low salivary output, wet the mouth first with water as this will improve the release of calcium and phosphate ions into the saliva.
2. At the start of the in-office bleaching appointment, isolate the teeth (e.g. using an Ivoclar-Vivadent Optragate) and then remove extrinsic stains from the tooth surface using pumice (not prophylaxis paste). This will leave a hydrophilic surface that is readily wet by the bleaching gel and will ensure optimal penetration of free radicals into the teeth.
3. Follow the normal protocol for the in-office bleaching.
4. After the treatment, patients can continue to use MI Paste Plus (for weeks if needed) until the clinician and patient are satisfied with the visually improved esthetic result.
5. In the case of at-home bleaching, prepare custom-made vacuum-formed trays in the usual manner, and use those to deliver the carbamide or hydrogen peroxide gel. After removing the trays and cleaning the residues of bleaching gel from the teeth, MI Paste Plus can be used until the clinician and patient are satisfied with a visually improved esthetic result.

Protocol for Remineralization of White Spot Lesions

1. Isolate the areas on the individual teeth affected, using a flowable composite or gingival barrier/light-cured ‘liquid dam’ (Fig. 3).
2. Using a micro-brush, rub the surface of the enamel with the white spot lesion with 4-5% sodium hypochlorite solution (e.g. endodontic irrigant) for two minutes (Fig. 3). This breaks down surface proteins and increases the porosity of the treated area, and transiently elevates its pH.
3. Rinse away the sodium hypochlorite solution from the tooth surface.
4. Dry the surface using compressed air. At this stage the lesion will be more obvious.
5. Dilute a pea-sized amount of MI Paste Plus in a dappen dish with an equal volume of water or glycerine (Fig. 4). The latter is preferred as it allows higher calcium ion concentrations to be achieved and gives a more suitable final viscosity.
6. Mix with a micro-brush to combine the solvent and the MI Paste Plus (Fig. 4).
7. Apply the diluted MI Paste Plus and rub gently for 20 seconds (Fig. 5).
8. Remove the gingival barrier.
9. Discharge the patient. Instruct them to avoid mouth rinsing for the next hour.
10. Nightly, the patient will apply a pea-sized amount of MI Paste Plus with a finger, after toothbrushing. There is no rinsing afterwards.
11. A regular (e.g. weekly or monthly) clinical review appointment is undertaken to assess the results. The procedure of treating the surface with sodium hypochlorite can be undertaken additional times if desired. This approach does not damage the enamel surface or cause mineral loss, unlike traditional micro-abrasion techniques using pumice and phosphoric acid. These latter methods can still be used in extreme or unresponsive discoloration cases, but for many patients they can be avoided.

Fig. 3

Fig. 4

Fig. 5

Figure 2A shows this typical clinical example of an ‘in-office’ treatment with emphasis of white spots after tooth whitening. After pre-treatment with sodium hypochlorite and dilute CPP-ACP, this 30-year-old female patient achieved white spot reversal with home use of CPP-ACP with fluoride. The patient used home custom whitening trays for one week following the in-office procedure, (6% hydrogen peroxide gel –SDI PolaDay^ for one hour daily) followed by immediate application of MI Paste Plus. No enamel micro-abrasion was carried out. After one week, a rapid improvement in tooth aesthetics was noted, with reduction of ‘white-patches’ (Fig. 2B).

Fig. 2A

Fig. 2B

The third case shows long term changes in tooth appearance, when MI paste Plus was used after in-office bleaching. The patient is a 53-year-old male. Images taken before and after in-office bleaching (Figs. 6 & 7) show only a minor improvement from this initial treatment, and neither the patient nor the clinician were happy with the result. The patient then underwent further treatment, with seven days of use of at-home 6% hydrogen peroxide gel in a custom tray (SDI PolaDay), for one hour each day. This was followed by MI Paste Plus applied each night for five months. The final result (Fig. 8) shows a much-improved final situation with increased translucency and light reflectivity. This is in keeping with laboratory studies that show the combination of peroxide and CPP-ACP enhances aesthetics by increasing the lustre and translucency of the treated enamel. 27 Moreover, CPP-ACP may be used concurrently with the bleach, and not reduce bleaching effectiveness. 27

Fig. 6

Fig. 7

Fig. 8

Other cases have been described that show the combination in-office and take-home whitening regimen, followed by the in-office and home application of CPP-ACP topical paste, with good results.28 It is important to continue the treatment beyond the point where the lesions visibly disappear, since further mineral gain is still occurring. For bleaching cases, the recommendation for white spots that are still visible after bleaching is to keep treating for two weeks past the point where they disappear into the tooth structure. This will normally mean a treatment of several weeks.

Conclusion
To summarize, our clinical experiences with the application of MI Paste Plus before and after tooth whitening procedures shows that this can be very useful for enhancing the overall esthetic outcomes.

*GC MI Paste Plus – GC America, 3737 W. 127th St, Alsip, IL 60803, USA., www.gcamerica.com
^SDI PolaDay – Southern Dental Industries, SDI Limited. 3-13 Brunsdon Street Bayswater, VIC 3153, Australia. OH

Oral Health welcomes this original article.

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About the Authors
Dr. Andrew Brostek is a Clinical Senior lecturer of Operative Dentistry at University of Western Australia School of Dentistry, Oral Health Centre. He has been in private clinical dental practice for over 30 years, and his interests lie in practicing and teaching minimal intervention dentistry. He has published extensively on preventive and minimal intervention dentistry.

Dr. Laurence Walsh is Professor of Dental Science at the University of Queensland in Brisbane, Australia. He has worked clinically in the field of special needs dentistry for 20 years and published extensively on preventive and minimal intervention dentistry. Through his research work, he has contributed to the development and clinical assessment of a number of the technologies which underpin minimal intervention dentistry which are now in clinical use in Australia and elsewhere.

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