By Ron Goodlin, DDS, FAGD; Holly Gilchchrist, CDA, Level II and Lori Place, CDA, Level II
The “tooth whitening” industry is a billion dollar a year bonanza for companies who are manufacturing and promoting bleaching products to the public as well as those dentists who are knowledgeable and willing to provide these services to their patients. The desire of the ordinary person to look better “now”, and the fact that the public wants everything done with a quick fix, is a fact of life in our modern fast paced society.
The popularity of tooth whitening is understandable as it provides the patient with a fast, if not, immediate result, which is non invasive and affordable. The public is bombarded with tooth whitening, articles and advertisements in glamour and lifestyle magazines The internet is filled with sites that are dedicated to tooth whitening. The stars they see and emulate in movies and on television, and the popularity of the extreme makeover shows attests to the high public interest in cosmetic procedures. As dentists it is important that we understand the etiology of tooth discoloration so we can properly advise our patients as to which form of treatment would be best for their situation.
I) SCIENTIFIC BACKGROUND
Normal tooth shade and anatomy
The reflection, absorption, translucence and opalescence of light will create the hue chroma and value of a tooth. The thickness of enamel and the colour of underlying dentin are the critical factors in the resulting tooth shade (Fig. 1).
The measurement of shade changes following tooth whitening procedures has historically been very subjective. Taken by Dentist, Patient and or Dental Auxiliary, using any one of a number of possible shade guides, some of which are supplied by the manufacturer as a printed tab on a Mylar sheet to be held up to the teeth. (How do we know if the shade difference between these different shade tab systems are not closer than those of other shade tab systems, thus six shades difference in one system may be equivalent to only three shades on another?)
Historically shades are arranged according to chromatic groups as opposed to, being arranged in order of increasing value. Newer guides such as the Vitapan 3D Master shade guide by Vident may give a truer indication of actual shade ranges and therefore become more purposeful in measuring shade changes. However, the problem of subjectivity remains, often leading to questionable claims of “ten shades difference in one week!”
Computerized colourimeters (shade scanners)–(Shadescan, Vita Easyshade, Shadevision) shade determination becomes an objective exercise. This will allow the clinician to better determine the results of tooth whitening procedures using the shade scanning devices to get an empirical measurement of before and after tooth hue, chroma and value (Fig. 2).
Etiology of tooth discoloration
Tooth discoloration is caused by large pigmented organic molecules located on the tooth surface or embedded within the enamel and/or dentin matrix.
Discoloration can be labeled according to the etiology of the staining and the associated depth and positioning of the stain.
1. Extrinsic staining:
a) Surface Extrinsic Staining: When the molecules are located on the surface of the enamel within the surface protein (pellicle) layer, they can be removed by a thorough mechanical cleaning of the tooth. This type of stain is generally caused by all forms of tobacco, tea, coffee, red wine, berries and plaque accumulation.
b) Penetrated Extrinsic Staining: Due to microscopic cracks and porosities in the enamel matrix, these molecules can penetrate into the surface layer of the enamel itself. The resulting discoloration cannot be removed by mechanical means, and must be chemically treated to remove the pigmented molecules from within the surface enamel matrix. There are times that medicaments will stain teeth as in the case of patients undergoing chemotherapy (Fig. 3).
2. Intrinsic staining:
Intrinsic stains refer to those stains which are incorporated into the dentin or enamel matrix during development of those structures embryologically. These stains include tetracycline staining, fluorosis and staining from systemic conditions such as a high fever during tooth development.
Etiology of intrinsic tooth discoloration:
i) Drug related discoloration: (Tetracycline, Monocycline)
Tetracycline molecules are actually incorporated into the enamel matrix by chelation of the tetracycline molecule with the calcium resulting in tetracycline orthophosphate. Discoloration occurs when this molecule reacts with sunlight and darkens with increased exposure (Fig. 4).
ii) Mineralization related discoloration: (Fluorosis, Calcium)
Fluorosis occurs with prolonged ingestion of fluoride ions in excess of 1-2ppm. The ameloblasts are affected, resulting in defective calcification of the developing enamel matrix. Instead of the enamel forming as a homogeneous mass, alternating areas of hypomineralized and porous subsurface layers with areas of hypermineralized enamel is formed. The result is enamel hypoplasia in the form of brown and white striations known as mottled enamel1 (Fig. 5).
iii) Systemic Conditions: (Amelogenesis Imperfecta, Dentinogenesis Imperfecta) Stain occurring from systemic conditions can range from genetic problems (amelogenesis imperfecta, dentinogenesis imperfecta (Fig. 6), cleft lip and palate) to medical situations such as high fevers and drug ingestion during periods of tooth development. These can result in hypoplasia, banding and mottled enamel, (cerebral palsy, renal disease, severe allergies, deficiencies of vitamin C, vitamin D, calcium and phosphorous during development, neurological disorders), discolorations (blue-green or brown from bilirubin staining of dentin following infantile jaundice, brown stain from blood cell destruction during erythroblastosis fetalis, and purple-brown stain from patients suffering from porphyria).
Patients undergoing chemotherapy and taking high doses of strong medications in the treatment of medical conditions become more prone to staining due to dry mouth, and various reactions to medications.
iv) Trauma: Traumatic injuries can also cause banding, enamel hypoplasia, and calcified spots. This most often occurs when a child bumps his primary anterior tooth resulting in the disruption of the enamel matrix formation in the developing permanent tooth bud.
Dark grey teeth will result from situations where there is a traumatic injury to a tooth, resulting in internal bleeding within the pulp chamber. As the blood cells travel and settle within the dentinal tubules, they eventually breakdown leaving iron molecules in the form of hemosiderin, causing a grey cast to the tooth. Many of these teeth may remain vital, while others will require endodontic therapy to treat the resulting pulpal necrosis (Fig. 7).
v) Dental Conditions:
a) Caries will appear as a grey cast, a white opacity, or a brown or black discoloration due to the degradation of bacteria and food debris.
b) Amalgam can stain the dentin and create a shadow through thin enamel.
c) Old composite materials which were colour unstable can discolour with age creating a shadowing through the overlying enamel (Fig. 8).
d) Metal posts will also create internal shadows which will result in a grey cast to the tooth.
vi) Disruption of the enamel matrix
a) The enamel matrix is constantly exposed to the effects of thermal expansion resulting in microporosities and cracks which allow pigmented molecules to leach into the enamel matrix.
b) Acids open the pores in the enamel–as we know from our acid etching and bonding studies–these micropores allow the influx of pigmented molecules.
vii) Aging Process
a) Aging will often result in yellowing of the teeth. As we age and the enamel thins due to wear and dissolution, the deep yellow colour of the underlying dentin and the laying down of secondary dentin within the tooth, reflects through the thinner enamel giving the appearance of a dull yellow older looking tooth. The thinner enamel precludes
the enamel matrix to fracture showing enamel craze lines or actual stained cracks within the tooth (Fig. 9).
b) Enamel crazing due to internal fracturing of the enamel matrix and the influx of stains into the craze lines will result in yellow brown crack lines in aged teeth.
The chemical-biological mechanism of whitening
Tooth whitening or bleaching is achieved by the oxidation of organic particles due to the release of highly unstable (perhydroxyl ion) free radicals from the activated hydrogen peroxide. The hydrogen peroxide is able to penetrate through the inorganic salts and organic matrix of the enamel, and penetrate the dentinal layer. (This penetration is what can later cause the tooth sensitivity which has been diagnosed as a mild to moderate reversible pulpitis in the form of tingling or cold sensitivity following bleaching.2)
Bleaching can be achieved by using carbamide peroxide, or hydrogen peroxide. Carbamide peroxide, also known as urea peroxide is itself broken down into water and hydrogen peroxide. The greater the concentration of hydrogen peroxide, the greater the amount of free radicals, which will be available for the bleaching process. A concentration of 10 percent carbamide peroxide is roughly equivalent to three percent hydrogen peroxide.
The activation of hydrogen peroxide is accelerated by heat which can come from body heat, or from the application of high intensity light. This results in a more efficient rapid release of free radicals which penetrate the enamel matrix.3 Some studies have suggested there is no difference in the efficacy of the bleaching materials when used with or without light activation.4 The free radicals interact with the large organic pigment molecules within the enamel and dentinal matrix. These large pigmented molecules are fractured and broken down to much smaller and less pigmented molecules as they are chemically reduced when they react with the free radicals, thus reducing the pigmentation of the tooth (Table 1).
Carbamide peroxide (CH4N2O2) also called urea peroxide–when mixed with water there is a release of urea and hydrogen peroxide (Free radicals of approximately three percent concentration with a 10 percent carbamide peroxide gel) which results in the oxidation of the organic particles. Other ingredients in the gel can include glycerin, carbopol, sodium hydroxide, sodium benzoate, triethanolamine, artificial sweeteners colorants and flavoring agents. Newer surfactant technology has added citric acids EDTA, and other chemicals to increase the penetration within the enamel matrix, and light and chemical activators to cause an increased concentration of free radicals released during activation.
Hydrogen peroxide is applied in concentrations ranging from 7.5 percent-38 percent (7.5 percent hydrogen peroxide releases approximately the three percent of oxidizing free radicals as 10 percent carbamide peroxide materials). It has been suggested by manufacturers that when used in conjunction with light or laser to enhance the activation, the whitening process is accelerated (7.5 percent H2O2 light activated has been suggested to release five percent of oxidizing free radicals).
II) DIAGNOSIS AND TREATMENT OF TOOTH DISCOLORATION
Successful treatment of tooth discolorations depends on proper diagnosis and treatment planning for the individual patient. If bleaching has been determined to be the best treatment, the efficacy of the treatment is dependant on patient compliance, condition of the teeth, type of stain and the concentration, amount of time and delivery system of the bleaching material applied.
Diagnosis of tooth discoloration
Medical history–to identify genetic, systemic conditions.
Dental History–to identify traumatic incidents, genetic conditions.
Oral Hygiene–plaque, material alba, surface material staining.
Clinical condition–existing restorations–discoloration from caries, existing restorations, posts.
Tooth vitality–endodontic condition.
Transillumination–cracked enamel matrix.
Enamel condition and thickness.
Treatment of tooth discoloration
Tooth brushing (includes those containing baking soda)
Indications for mechanical treatment
a) Large plaque accumulation.
b) Surface stain caused by tobacco, food dyes, surface agents .
Non Vital Bleaching.
Indications for chemical bleaching:
a) Light to moderate discolored or dark teeth.
b) Tooth condition is sound.
c) Patient medical history is sound.
Contraindications to chemical bleaching
b) Damaged tooth with open dentinal tubules.
c) Abfraction lesions or recession which are reactive to cold.
d) Large pulps and teeth sensitive to cold.
e) Allergy to peroxide.
f) Patient with poor compliance.
3. Combination physical and chemical
Whitening toothpastes (those containing hydrogen peroxide).
Microabrasion–Opalustre by Ultradent (slurry of 6.6 percent hydrochloric acid).
Indications for combination mechanical and chemical treatment
a) Light Surface stain can often be treated by whitening toothpastes.
b) Calcified spots and mottled enamel can often be treated with micro abrasion.
4. Restorative solutions
Veneers (both direct composite and indirect porcelain).
Composite restorations to replace old amalgams, decay.
Indications for restorative treatment
a) Active caries.
b) discolored old restorations.
c) internal staining due to restorative material, amalgam, posts.
d) Severe staining due to systemic or genetic conditions.
5. Combination of chemical and restorative treatment
Bleaching prior to veneers.
Bleaching prepped crown stump.
Internal bleaching prior to restorative treatment.
Indications for combined chemical and restorative treatments
a) Discolored teeth to be veneered after bleaching.
b) Discolored teeth prior to final crown fabrication.
c) Discolored teeth prior to composite restorations.
d) Internal bleaching prior to post endodontic restoration.
Before embarking on any cosmetic treatment, it is essential to understand the patient’s expectations. All patients expect excellent results and all patients think they are a candidate for bleaching procedure. It is up to the practitioner to properly diagnose the etiology of the discoloration, and to educate the patient of the different treatment modalities, and the rates of success to be expected.
It is absolutely imperative the patient understands that when proceeding with the chemical bleaching techniques, the level of whitening cannot be guaranteed, and the treatment will not lighten existing restorations. It is equally important to explain the procedure, the potential risks, and the importance of patient compliance in the success of the treatment. Like all treatment, it is necessary to discuss all financial arrangements before embarking on treatment. The author personally recommends taking impressions to make the bleaching trays immediately, keeping the patient excited about the pending treatment, but do not make those trays prior to payment in full for the procedure.
III) TYPES OF WHITENING SYSTEMS
Delivery Systems: There are four categories of over the counter products and three main categories of dentist supervised products.
1. Over the Counter Products (OTC)
a) Whitening toothpaste–physical action with some chemical whitening components (baking soda, sodium hydroxide, H2O2)
b) Whitening strips–chemical (6.5 percent hydrogen peroxide) applied by self adhesive strip.
Advantages–convenience, relatively inexpensive.
Disadvantages–takes long time to get desired results, frequent re-treatment required, increases long term costs.
c) Whitening Gels–chemical usually carbamide Peroxide.
i) Paint-on–carbamide peroxide or H2O2 mixed with thickening and adhesive agents to help the material stick to the tooth.
Advantages–relatively inexpensive, convenience.
Disadvantages–bad taste, requires long time to get results, frequency of application necessary.
d) Home bleaching tray systems.
Homemade tray delivery–carbamide peroxide gel placed in plastic tray which is generically produced.
Advantages–relatively inexpensive, convenience. Often purchased through the internet.
Disadvantages–poor fitting trays leads to questions about safety, takes a longer time to get results (Table 2).
2. Dentist Supervised
i) Light/Laser Activated–carbamide or Hydrogen Peroxide or combination placed on surface of tooth and activated by U.V. light, halogen light, plasma arc or laser. Zoom (Discus), Lumalite.
Advantages–very inexpensive yet immediate cosmetic procedure–soft tissue protection available without rubber dam.
Disadvantages–not legal in Canada for auxiliaries to bleach teeth time consuming for DDS. Tooth sensitivity, chance of gingival irritation.
b) In Office Bleaching using trays–chemical using high concentrations of hydrogen peroxide (35-38 percent) placed in a custom fitted tray.
Advantages–very fast results, safe. Used to jump start a case in 30 minutes.
Disadvantages–tingling sensation, numb feeling, excessive drooling, sensitivity to hot and cold.
c) Home Bleaching trays chemical usually carbamide peroxide placed in a custom fitted tray. (available in 10 percent – 16 percent – 22 percent concentrations).
Advantages–inexpensive, excellent fast results, safe. Patient controls the treatment–convenience factor very little dentist time, auxiliaries take impressions and make the trays.
Disadvantages–tingling sensation, numb feeling, excessive drooling, sensitivity to hot and cold, gingival irritation if patient uses too much or if trays made improperly. Patient must be educated on how to apply the gel. Patient compliance is out of the control of the dentist (Table 3).
METHODS AND MATERIALS
Chairside: Dentist supervised surface prophylaxis of teeth using prophy paste, cavi-jet, mechanical scaling, air abrasion to remove surface staining.
At-home: Toothpastes used at home to remove surface plaque and stains.
In-office, Chairside: light activated or laser bleaching has been shown to have the greatest effect with the least time. DDS supervised allows the use of higher concentrations of bleaching agents which is safe for the patient.
Take-home bleaching kits using professionally fabricated bleaching trays results in a safe method of bleaching whereby the results will often eventually be the same as the light activated systems; however it may take prolonged multiple treatments to achieve the same result. Home bleaching using OTC products is questionable for deeper intrinsic staining but will work well for surface extrinsic stains using a combination of mechanical and chemical bleaching when given enough time and patient compliance.
OTC products have questionable delivery systems, the active bleach may not be reaching the area of the enamel matrix in the concentrations required to actively cause organic molecular oxidation. This decreased efficacy due to the decreased chemical concentration and often questionable delivery systems will create a situation where repeated applications are required before results become noticeable, thereby dramatically increasing the time frame required for treatment. There is a much higher risk of swallowing material, gingival irritation and decreased efficacy due to this less efficient delivery system. The greatest problem is patient compliance. After a few treatments, the remainder of the material often sits in a drawer until months later, when the patient decides to try it again, and now the material has expired. The patient later complains that it didn’t work!
Discuss bleaching procedures.
Examine patient to determine type of staining and appropriate treatment procedure, is it precursor to veneering or is it a stand alone procedure etc.
Ask patient what their expectations are.
Explain that existing restorations will not lighten and will need to be replaced after the procedure.
Explain there is no guarantee bleaching will work. 10 percent no appreciable effect, 60 percent 2-5 shades difference, 20 percent more than 5 shades difference.
Discuss time expected, number of procedures.
Discuss cost involved.
Discuss difference in technique between vital and non vital teeth (endodontically treated).
Explain risks, about possibility of tooth sensitivity, gingival irritation.
Explain what you feel will be a reasonable expectation from this procedure.
In-office power bleaching of vital teeth
Thorough prophylaxis of teeth.
Take preliminary shade and photograph.
Isolate teeth with rubber dam or gingival protectant following instructions.
Orabase or gingival protectant placed to protect papillae.
Prepare power bleach according to manufacturer.s instructions.
Apply bleaching gel according to manufacturer,s instructions.
Light or laser activate gel as per material selection.
After specified bleaching time, suction and reapply fresh gel.
After completing procedure, carefully wash all material off of teeth.
Remove gingival protectant/rubber dam.
Take after shade and photograph.
When treating previously endodontically treated teeth with internal staining, the older method of heat treated hydrogen peroxide (cervical root resorption is a possible consequence of internal bleaching and is more frequently observed in teeth treated with the thermo-catalytic procedure) in combination with a “walking bleach, releases oxygen which acts to oxidize the internal organic materials causing the staining. A combination of 30 percent hydrogen peroxide, mixed with sodium-perborate in the form of tetrahydrate is left in the tooth for one week. The patient returns for repeat treatments until the desired results are achieved.(Ho and Goerig 1989, Anitua et al 1990, Baratieri et al 1995, Walton and Rotstein 1996) The placement of calcium hydroxide is placed for seven days to neutralize any effects and prevent any cervical erosion. According to this protocol, an overall 80 percent success rate has been reported. (This includes 92 percent success for ideal cases over a 5 year period, and 55 percent success rate for poor clinical condition cases over a 5 year period.6) The walking bleach technique is now the treatment of choice when a proper seal has been created first.
In-office power bleaching of non vital tooth
Evaluate endodontic situation clinically and radiographically.
Thorough prophylaxis of tooth.
Take preliminary tooth shade and photograph.
Apply rubber dam and gingival protection.
Open lingual access and remove any excess gutta percha to 1mm below the gingival margin (use a #2 round bur in slow speed handpiece).
Gently remove internal surface layer of dentin to expose fresh surface, try to remove any discolored dentinal material.
Seal gutta percha with resin ionomer componomer or hybrid composite.
Pulp chamber and entire facial and lingual surface are now coated with bleaching gel.
Light cure activation labial, and lingual according to manufacturer’s instructions for a total of 30 minutes suctioning and applying fresh gel as necessary.
After completing procedure, carefully wash all material off of teeth.
Assess if tooth requires additional bleaching, if so, place a walking bleach, by placing a mixture of Amosan (sodium perborate) and gel bleach, pack it into the chamber. Seal the tooth with cavit. Patient must be reappointed in three days to reassess.
Restore access opening using alight colored dentin shade composite material to help achieve the final tooth coloration desired.
Remove gingival protectant/rubber dam.
Take after shade and photograph.
Thorough prophylaxis of tooth
Take preliminary tooth shade and photograph.
Take impression of the arch to be bleached. Inspect for quality!
Fabrication of custom bleaching trays:
Pour Models in stone
Prepare models to eliminate vestibule and palate
Trim so the base of the model is thinner than the occlusal plane (this will help get a more accurat
e seal around the teeth during vacuforming) (Fig. 10).
Make sure all bubbles are filled, blebs are removed.
Gently scractch the gingival margins to enhance the seal of the bleaching tray at the gingival margins (Fig. 11).
Take a small amount (0.5mm) of block out resin and place over the labial portions of the teeth to create a small reservoir in the bleaching tray. Make sure this does not extend to within 1mm of the gingival margin as it will disrupt the marginal seal. Light cure each tooth.
Lubricate the model with PAM.
Preheat the tray forming machine with the plastic sheet in place, position the model in the vacuform and create the tray with a thin soft plastic sheet. (keep the pebbled finish towards the model) Once the plastic sheet is sagging about 1 inch, engage the vacuum and slowly lower the heated tray material onto the model (Fig. 12).
After the tray has cooled remove the plastic from the stone model (Fig. 13).
Using sharp scissors, trim the tray to within 2mm of the gingival margin of the teeth.
Carefully retrim using sharp precision scissors to 1/4mm of the gingival margins (Fig. 14).
Using a small butane torch, lightly flame the tray edges to gently melt the edges so they become rounded, thereby removing any rough edges (Fig. 15).
Wash, disinfect the tray and place it in a labeled case for delivery to the patient.
1. Deliver the Bleaching tray, try it in and make sure it fits tightly yet is comfortable.
2. Patient Instructions must be given both verbally and in written form. Patients can bleach while they sleep or for 2-4 hours during daytime.
Check patient in 7 days to check tissue and bleaching effect. This is a good opportunity to discuss any patient concerns. If the patient is exhibiting any lingering tooth sensitivity, topical fluoride application is advised.
3. Combination of Mechanical and Chemical
Microabrasion using a paste of abrasive and bleaching chemical applied with a prophy cup to the surface of the enamel.
Isolation of teeth with rubber dam, ligation and tissue protection using light cured gingival seal (Ultradent)
Gentle application of micro abrasive paste using prophy cup
Reapply fresh material as needed.
Note when patient reports tooth is becoming sensitive and stop procedure
Wash teeth and apply fluoride treatment.
Dismiss patient, reappoint in one week to continue treatment until achieve desired result (Figs. 16 & 17).
4. Restorative Procedures.
Cosmetic restorative techniques such as direct and indirect veneers and crowns are used to cover badly discolored, broken down teeth when it is deemed that bleaching techniques would not work, or if bleaching techniques previously attempted did not achieve the desired results (Figs. 18 & 19).
5. Combination restorative and bleaching techniquesIn situations where teeth are to be restored and are discolored, whitening techniques can be employed prior to restoration to enhance the underlying colour in order to achieve a superior cosmetic result. This can also be used on non vital teeth to lighten the underlying tooth structure prior to crown placement.
EFFICACY OF DIFFERENT DELIVERY SYSTEMS
It is generally expected that 20 percent will achieve a change of 5 or more shade 53 percent will achieve a change of 2-5 shades and 27 percent will achieve a change of less than 2 shades 7 These numbers are based on older formulations. With advances in surfactant technology we expect these numbers to be significantly skewed towards: 5 percent less than 2 shades, 35 percent 2-5 shades and 40 percent 5-7 shades and 20 percent 8 shades or more.
The active ingredient in all bleaching products is the hydrogen peroxide. This H2O2 may be applied in the form of carbamide peroxide or hydrogen peroxide and mixed with a number of different surfactants such as more advanced chemical and light activators which maximize the release of free radicals from the H2O2, and chemicals which act to maximize the penetration of the H2O2 into the enamel and dentin matrix, such as various acids. Additional products include the addition of potassium nitrate in an effort to decrease the post operative sensitivity so often experienced by patients following treatment. The more advanced the surfactant technology becomes, the bleaching process will become faster and more efficient with more pronounced shade changes as a result. Zoom appears to have the best surfactant technology at the time of writing of this article.
Immediate activation by mixing the materials at the time of use will create a more efficient release of the free radicals and a longer shelf life. Premixed materials rely on heat activation only to release the free radicals, this works but slowly and inefficiently and they show decreased efficacy as they reach their shelf life limitations.
Light or laser activation
With the proper surfactant formulation, a more efficient release of oxidizing free radicals can be achieved, making the bleaching process more efficient over a shorter amount of time. At the time of writing this article, Zoom by Discus Dental Products, utilizing an intense application of UV light appears to result in the most dramatic effect in the shortest amount of time.
Problems associated with reports in the literature:
Technology is changing so quickly, that by the time many articles are published, new products, and specifically, improvements in the surfactant technology, renders the products and techniques discussed obsolete. It is expected that the newer formulations and delivery methods will kew the reported results to a more positive position, allowing us to achieve better results in shorter times, than those previously reported in the literature. We have noticed that the results with the Zoom system were far better than any other material tested so far.
Reported cases, especially home bleaching systems, indicate results that are impossible to be fully or objectively monitored, and are predicated on assumptions of 100 percent patient compliance, proper use of the materials and zero bias when determining shade selection.
SAFETY EFFECTS AND CONCERNS
Li reports carcinogenicity and genotoxicity of peroxides when used as bleaching agents. Reports indicate hydrogen peroxide is a promoter of carcinogenicity when in the presence of cigarette smoke. Therefore it is essential that the patient refrains from smoking during the duration of the bleaching process and for a reasonable time thereafter.8
Some studies have indicated the dissolution of the enamel layer when using OTC products that contain acid over a prolonged period of time.9 Other studies have shown a decreased micro hardness in the enamel matrix following prolonged bleaching.10 It appears that when properly controlled these are not clinically significant, however this again indicates that proper dentist supervision is required for the ultimate safety of the patient.
Tissue irritation following bleaching is generally limited to mild irritation and hyperemia, however there are reports of severe blanching if the bleaching material is allowed to contact the tissue for any prolonged period of time, which can result in gingival sloughing resulting in raw areas of tissue. Again indicating that proper dentist supervision and careful fabrication of custom trays must be undertaken to create a seal preventing excess material from coming into contact with the gingival tissue. This is preferable to the stock trays available in the OTC products which is potentially dangerous to the patient.11
There is no statistical significant difference in subsequent plaque accumulation following whitening procedures.12
Oxidation free radicals can penetrate through the enamel matrix and will trigger sensitivity due to the stimulation of the exposed dentinal tubules.
Large pulps–younger patients does not appear to create a situation where the experienced sensitivity is a detriment to treatment.13
F POST OPERATIVE SENSITIVITY
Use of topical fluorides immediately following treatment appears to give the greatest relief of the tingling and cold sensitivity. Newer formulations of some bleaching products include potassium nitrate, a molecule commonly used in anti-sensitivity tooth pastes which purportedly occludes open dentinal tubules, thereby decreasing sensitivity.
Dr. Goodlin has a practice limited to Cosmetic Dentistry in Aurora ON. He is a well known lecturer and has been the author of many publications on Cosmetic Dentistry and Dental Photography.
Oral Health welcomes this original article. Part II in May, 2004 with complete references.