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ОглавлениеBleaching
Beautiful white teeth were already important to the Romans. They polished their teeth using urea (carbamide), especially urea from Portugal because this was known to give the teeth a brillant white appearance. During the Middle Ages, tooth bleaching was a barbaric treatment. The barbers not only extracted teeth, they also bleached teeth with aqua fortis, a mixture containing nitric acid. This treatment was initiated by first filing the patient's teeth—today one would call the process “recontouring”—with an iron grater. At the beginning of the 20th century, teeth were bleached with high concentrations of hydrogen peroxide (H2O2). The micro abrasion technique, i.e., the use of a weak hydrochloric acid solution, was used to remove stains. These treatment methods were first published in 1895 in the American Journal of Dental Science (Westlake 1895). At the beginning of the 20th century, “Colorado brown stains,” a form of fluorosis, were also removed with diluted hydrochloric acid (micro abrasion) and hydrogen peroxide (bleaching).
50 Various causes of teeth discoloration before and after bleaching
Many teeth have discolored surfaces. As one ages, teeth become darker and change to a brown-orange color. In addition, external effects of tooth discoloring are observed, such as those from smoking and some beverages (coffee, tea, red wine, etc.). However, discolorations are also due to genetic conditions or caused by the use of certain medicines (tetracycline).
History of Bleaching
Bleaching in the Practice
At the end of the 19th century, dentists began to bleach vital teeth. Westlake (1895) used a mixture of peroxide and ether. Abbot used Superoxol, a stabilized mixture consisting of 30% H2O2 to bleach teeth discolored by fluorosis (Abbot 1918; Prinz 1924). Ames earned his fame with a mixture consisting of 30% H2O2 and ether that he used with a source of heat (Ames 1937). Indeed, a treatment lasted approximately 30 minutes and the sessions were repeated up to 25 times.
Zack and Cohen (1965) were the first to conduct a scientific evaluation on how the effect of the source of heat affected the pulp. They found no pulp damage. The results were later confirmed by Nyborg and Brännström (1970).
Since 1972 Arens has also tried to bleach tetracycline discolorations with 35% Superoxol kept at a temperature of 10 °C below the pain threshold.
Home Bleaching
The orthodontist Klusmier from Fort Smith, Arkansas, had, like so many other orthodontists, patients with problematic gingivitis. He examined the effect of Gly-Oxid (Marion), which his young patients used during the night in a removable appliance. This treatment resulted in a close-to-healthy gingiva. After some patients had used this gingivitis therapy for some time, Klusmier discovered that the teeth had become brighter and that lighter tetracycline discolorations had disappeared. He presented his observations between 1970 and 1975 at different “table clinic” meetings. In 1972 he experimented with the somewhat thicker Proxigel (Reed & Carnrick Pharm.) retained in a tray.
51 Survey of dentists opinion on bleaching
Survey of members of the American Academy of Cosmetic Dentistry, conducted in 1992.
The periodontist Wagner, a colleague of Klusmier's, explored the use of the method in adults and subsequently discovered that the gingiva was somewhat less inflamed and that the teeth appeared whiter. Slowly the method spread and was adopted in 1988 by Haywood at the University of North Carolina. Haywood and Heymann (1989) developed a home bleaching technique that is still the currently used standard of care.
Carbamide peroxide has been long known among periodontists as an oral antiseptic substance. Munro described in 1968 that as a side effect of using carbamide peroxide in a splint, the teeth became whiter.
Based on his findings, the first commercial bleaching agent was developed for bleaching vital teeth, namely White & Brite (Omni) containing 10% carbamide peroxide.
Vital and nonvital tooth bleaching has not been around for very long, which is reflected in the list of commercial products being introduced on the market:
| 1989 | White & Brite by Omni |
| 1991 | Opalescence by Den-Mat |
| 1992 | Nite White by Discus Dental |
| 1994 | Platinum by Colgate |
The sales figures during the past 4 years have more than quadrupled. Bleaching is popular: patients wish to have white teeth and dentists see this as a new area to do business in.
A survey conducted by the Clinical Research Associates in 1994 gave an extremely positive trend: 92% of the 7 617 dentists surveyed bleached their patients' teeth patients as a matter of routine—in more than 90% of cases to the fullest satisfaction of the patients.
Only few innovations have had such a high degree of acceptance among both the public and professionals.
Scientific Studies
Haywood published his first studies in 1990. Extracted teeth were bleached for 5 weeks in the usual manner. Examination of the teeth using the scanning electron microscope revealed no changes in the enamel. The type of bleaching materials used did not affect the topography of the enamel.
In 1991 Yarborough published a literature review of the topic regarding effectiveness and safety of bleaching. Bleaching can be performed effectively with two substances, namely carbamide peroxide and hydrogen peroxide. Carbamide peroxide disassociates into H2O2, CO2, urea, and NH3. H2O2 is the effective agent here as well. Bleaching with H2O2 has the advantage that it takes place 3 to 6 times faster than with carbamide peroxide.
Murchison examined the effect of carbamide peroxide on enamel and concluded that a short-term application did not cause any significant change to the surface and physical properties of enamel (Murchison et al. 1992).
The majority of scientific studies show that it is safe to bleach teeth with 10% carbamide peroxide (Haywood 1992).
52 Effect of bleaching on micro hardness and morphology of enamel
Left (above): A natural enamel surface exhibits well-defined perikymata with irregular contours. It was used as a control and placed in saline.
Right (above): This enamel surface was etched too aggressively (50% H2O2). It is relatively porous and has poorly defined perikymata.
Left (below): Enamel bleached with Accel (35% H2O2) has clearly defined perikymata and a smooth surface. It was not damaged by bleaching.
Right (below): The enamal appears to be relatively intact after the surface was bleached with HiLite (main component also 35%H2O2).
Bar= 50 μm
Courtesy of C. Q. Lee
A Review of Bleaching Methods
Bleaching Vital Teeth
To bleach vital teeth, chemicals are placed on the enamel surface. This method is called external bleaching and can thus only change the discoloration of enamel.
Bleaching Nonvital Teeth
To bleach nonvital teeth, the chemicals are placed in the pulp chamber. In this way the coronal dentin is changed. The process is called internal bleaching.
In-Office Bleaching
These are very aggressive bleaching methods that were used previously when bleaching was done in-office: usually 33% H2O2 was used together with heat and light. Damage to enamel could occur with this method. The technique has been named power bleaching.
Bleaching teeth in the dental practice continues to play an important role. For example, when front teeth are treated with veneers, the cuspids can be brightened up by in-office bleaching. If one wants to achieve results very quickly, then in-office bleaching is preferred to home bleaching. Stronger chemicals are applied in such situations, but no additional energy sources (heat and light) are used. In most cases, three bleaching treatments are necessary.
Home Bleaching
Advantages
—The dentist needs to spend very little time treating the patient. A requirement is that the dentist has a dental assistant or hygienist who has the necessary qualifications needed for instructing the patient about the home bleaching procedure.
—This bleaching technique is usually more affordable than the in-office bleaching.
—The patients bleach their teeth whenever they wish to do so. They do not have to come to the dental office to do this.
—In home bleaching, in contrast to in-office bleaching, no rubber dam is required. Many patients have an acquired latex allergy and cannot tolerate the rubber dam.
—The bleaching process takes longer and is therefore safer for teeth.
Disadvantages
—Patients must collaborate actively. If they do not wear the bleaching tray, no therapuetic effect will occur. If they use their tray too much each day, the result is often hypersensitive teeth.
—There are patients who prefer to get their teeth bleached by the dentist or dental staff, even if this is means higher costs and longer treatment times.
—The bleaching process takes longer in the case of home bleaching than in the case of in-office bleaching.
Side Effects of the Bleaching Agent
—Bleaching agents contain peroxides. These enhance mutagenic effects of other chemicals, such as those present in cigarette smoke. Based on present scientific knowledge, patients should not smoke while wearing a bleaching tray. In the long run, the peroxides can also change oral flora. If bleaching is done over too long a period of time, Candida albicans can accumulate and hypertrophy of the papillae can occur.
—Power bleaching changes the structure of the hard tooth tissues and resulted in pulpitis in an animal experiment.
—A common adverse effect that occurs during bleaching is temporary hypersensitivity. This disappears in almost every case when the bleaching process is interrupted and the teeth are remineralized using a toothpaste containing fluoride.
—During in-office bleaching, etching bleaching agents are used. If the gingiva is not protected it can be etched. However, the damage is temporary and disappears after a few days.
—Patients with tooth hypersensitivity should not have their teeth bleached because of the risk of postoperative sensitivity.
—When bleaching nonvital teeth, root resorptions may occur. Since the teeth are prepared internally, crown fractures are also possible.
—No restorations should be bonded directly after bleaching because the bonding ability of the adhesive material is greatly reduced. A period of approximately two weeks should elapse before any resorations are bonded.
—The patient should be informed that the bleaching result will decrease with time and it may be necessary to do a supplementary bleaching (after approximately one year). This change in color has several causes (coffee, red wine, fruit juices, soft drinks, and other drinks with low pH-values, smoking, etc.). As long as these external factors are present, the teeth will become darker.
53 Chemistry of the bleaching process
When bleaching teeth, oxidation reactions take place. After a certain amount of bleaching time, the enamel surface is saturated with the bleaching agent. When this happens, the bleaching process must be stopped, because otherwise the enamel could be damaged.
(Adapted from Adept Report)
Despite these potential risks, bleaching of vital and nonvital teeth is the most conservative therapy available in dentistry.
Which Discolorations Can Be Bleached?
Tetracycline Discoloration
The first tetracycline compound was purified in 1948, and the first tetracycline-induced tooth discoloration was described in 1956. Only some of the tetracycline accumulates in the enamel, while a much larger proportion accumulates in dentin (Brown 1974). After light-induced oxidation, a red quinone compound forms (4-a, 12-a anhydro-4-oxo-4-dimethyl-amino-tetracycline). Different bleaching agents can reduce this dye.
Tetracycline discolorations can be brownish, grayish, or bluish. They usually occur bilaterally and can involve several teeth in both upper and lower jaws. If the anterior baby teeth are involved, the tetracycline discoloration was induced some time between the fourth month of pregnancy and the ninth month after birth. However, if the permanent front teeth are discolored, the tetracycline medication most likely occurred between the third month after birth up to the seventh year of age.
The strength of the discoloration depends on duration and quantity of the tetracycline application. The type of color change depends on the type of the tetracycline derivate. Gray-brown discolorations are due to Aureomycin (Haywood and Heymann 1994). Yellow discolorations are due to Ledermycin, Terramycin, or Achromycin (Bailey and Christen 1968). Yellowish evenly discolored teeth can be successfully bleached (Bevelander 1961).
54 Causes and therapy of tooth discoloration
The best results with bleaching are achieved with color changes caused by the aging process, light fluoroses, and tetracycline discolorations of Category 1. All other discolorations should be treated using restorative methods.
The three categories of tetracycline discolorations are:
Category 1:
Slight (yellow, brown, or gray) discolorations that extend evenly over the whole tooth. They can usually be removed after three to five bleaching treatments in-office or through a 4-week bleaching treatment at home.
Category 2:
A strong, but even discoloration that can normally be removed after five to seven in-office bleachings, or after four to six weeks of treatment with the home bleaching method.
Category 3:
Strong discolorations using horizontal strips. This requires veneers or even crowns.
Fluorosis
Dental fluorosis can be induced between the second trimester of pregnancy and the ninth year of age, i.e., during tooth development when fluoride uptake is in excess of 1 ppm in the drinking water. (The fluoride level of the drinking water should be checked before fluoride medication is prescribed.) The degree of tooth discoloration—which varies from slightly chalky to strong yellow-brown spots due to precipital accumulations (secondary) after the eruption of the teeth—correlates directly with the fluoride uptake. The discolorations are restricted to the enamel (true enamel formation defects or hypoplasia); they are usually found bilaterally and in both jaws.
Bleaching is only successful when the enamel discolorations are superficial. A combination of micro abrasion and bleaching (two to four bleaching treatments), followed by facets or reconstruction of the enamel with microfilled composite is the treatment of choice. Alternatively, veneers can be made.
White Spot Lesions
These discolorations are innate or acquired during enamel formation and result from incomplete mineralization, due to a trauma, high fluoride exposure, genetic disposition, or illness. Acquired white spots are incipient carious lesions caused by plaque. They are often found around orthodontic brackets. The cause of innate acquired white spots must be removed first. That means that good oral hygiene must be established and low bacteria (caries) activity must be achieved.
Color Changes Due to Aging
Teeth become darker with age. Thus, a youthful tooth color of, for example, A1, becomes A2, A3, and A4 with age. This is a natural process which is enhanced by the presence of certain components in spicy food, alcoholic beverages, cigarette smoke or tobacco. Color changes caused by aging are ideal for bleaching.
55 Types of discolorations
A Mild tetracycline discoloration (bleaching time: three months).
B Mild tetracycline discoloration.
C Strong tetracycline discoloration (bleaching time: six months).
D Fluorosis with brown color changes.
E White spot discolorations after orthodontic treatment.
F Nonvital tooth.
Courtesy of Van B. Hoywood
Bleaching Vital Teeth
Prerequisites and Pretreatment
Radiographs must be available and the question of tooth vitality must be clarified. Existing restorations must be tight to avoid H2O2 reaching the dentin and the proximity of the pulp.
Acid treatment: The enamel of single, strongly discolored teeth can be locally etched with phosphoric acid. This improves the penetration of the bleaching agent and accelerates and reinforces the bleaching process. A general etching of enamel is not recommended. The result can be a rough enamel surface which later changes color more quickly.
In principle, tooth color should be determined before each treatment. Many patients wish to have snow-white teeth. Those beyond A1 tooth colors are also marked as “Hollywood toilet white.” One should not strive for such a goal. A tooth color change of about two shades is more realistic. Usually it is possible to reduce a tooth color of A3.5 to A2. The bleaching treatment should not proceed after Al color has been achieved, because an uncontrolled, long bleaching treatment can damage the tooth structures.
56 Status before start of bleaching treatment
Before treatment begins, the color of the teeth should be determined and the teeth should be photographed with shade tabs present. Here, the color is found to be A3.5/A4.
57 Outcome of home bleaching treatment
After completion of the treatment, the color of the upper incisors, originally A3.5/A4, has changed to A1/A2.
Courtesy of Ultradent Prod. Inc.
Use of anesthesia during the bleaching treatment is neither necessary nor sensible. The patient should register and report pain reactions (e.g., injuries to the gingiva or disturbances of the pulp caused by heat generation).
Bleaching Effect on Restorations
Patients should be informed that only enamel surfaces will be bleached and not existing restorations. That means that crowns and fillings may appear darker after bleaching treatments. In the case of fillings, one can remove the outmost layer of the filling and replace it with a new filling layer in a suitable tooth color. In the case of crowns, it may be necessary to renew these completely.
Swallowing the Bleaching Agent
In the stomach, carbamide peroxide is broken down into H2O2 and urea. H2O2 then disintegrates into water and reactive oxygen. Urea is produced naturally in the body and is removed by the kidneys.
Home Bleaching
This bleaching method has been available since 1989. It is most effective when treating orange-brown and age-induced discolorations (age-induced staining). Most bleaching agents are slightly acidic. Consequently, it is possible that exposed root surfaces respond very sensitively. Therefore, patients with exposed root surfaces should use desensitizing toothpaste with sodium fluoride right from the beginning (e.g., Sensodyne).
Possible side effects of home bleaching are:
—Gingival irritation (leaky tray)
—Temporomandibular joint disturbance (carrying the tray during the night)
—A feeling of pressure in the stomach (overfilling of the tray and swallowing the excess bleaching agent)
—Hypersensitive dental necks (excessive exposure to tray covering)
Treatment Procedure
1. Professional tooth cleaning, polishing of all tooth surfaces.
2. Determining the tooth color with the patient.
3. Radiographs of the teeth to be bleached (to detect possible internal damage).
4. Photographs with the shade tabs.
5. Diagnose and determine the causes of the tooth color changes (describe external factors).
6. Make a dental impression.
7. Fabricate a bleaching tray.
8. Hand the bleaching agent over to the patient. Demonstrate how to use the tray and the bleaching agent and hand over written instructions.
9. Recall and check the progress of treatment.
58 Adding bleaching agent to the tray
The patient is shown how to fill the bleaching tray. The patient takes the tray and sufficient bleaching agent home.
59 Inserted bleaching tray
To prevent any tooth hypersensitivity, the patient should wear the bleaching tray for only one hour per day over the first few days. Then, the patient can increase the time step-wise until a maximum of five hours per day is reached.
Indications
Yellow-orange and light brown discolorations of teeth are the ideal indications for home bleaching (age-induced staining). Also teeth with a mild form of fluorosis or a slight tetracycline discoloration can be bleached. According to newer studies by Haywood (1997), the success of bleaching tetracycline-induced discolorations increases if the patient is ready to wear a bleaching tray for half a year.
Whenever there are anatomical changes in the enamel surface, the patient should be informed in advance that it is unlikely that an ideal result can be achieved.
Home bleaching is ideal as a part of preprosthetic therapy. If the teeth are bleached before a general dental treatment, an essentially more aesthetic result can be achieved during the restorative phase.
Chemically-induced strong discolorations are a possible contraindication for home bleaching. Here the tooth colors are are usually blue or grayish. Patients with very sensitive teeth are another contraindication. Teeth that already exhibit hypersensitivity to tooth polishing should not be bleached.
60 Bleaching tetracycline discolorations
A distinctive blue-gray discoloration (left) has been significantly brightened (right).
61 Bleaching brown-orange discolorations
A strong brown-orange discoloration (left) has clearly been brightened (right).
Contraindications
Home bleaching is not suitable for:
—patients with a serious systemic illness
—patients using strong medications
—pregnant or breast-feeding women
—patients who suffer from allergic reactions to bleaching agents or the bleaching tray resin
—patients with extensively destroyed or extensively filled teeth
—patients who are heavy smokers or chew tobacco
—patients with temporomandibular joint disorders. The bleaching tray is not a bite splint. In fact, the bleaching tray can temporarily reinforce existing joint disorders,
—patients with extreme blue-gray discolorations
—patients with tooth hypersensitivity
Bleaching Agents
The newest bleaching agents for home bleaching contain carbamide peroxide. Gels containing 10–15% bleaching agent are currently being used. Carbamide peroxide is a compound consisting of urea and hydrogen peroxide. During decomposition, hydrogen peroxide splits off and disintegrates into reactive oxygen and water. A 10% carbamide peroxide solution is as effective as 3% hydrogen peroxide.
There are incidentally also home bleaching products that are purely hydrogen peroxide-based. These bleach 2.76 times faster than the same concentration of carbamide peroxide. One of the first products on offer was BriteSmile. A disadvantage of such products is that an opened package must be stored in the refrigerator.
Home bleaching products must be applied to the teeth by means of a bleaching tray. These trays must have space for the bleaching agent.
62 Bleaching equipment for home use
Many home bleaching products have been introduced on the market over the past few years. However, up until now only few have been given a CE certification.
63 Overview of products used for home bleaching
(Adapted from CRA Newsletter, April 1997)
Fabricating a Bleaching Tray
Bleaching trays are medicament carriers that keep the bleaching gel in a certain position on the tooth. They are made of soft plastic. It is important that the trays adapt well to prevent the bleaching agent from being quickly diluted by saliva, which could reduce its effect.
The bleaching agents should only and exclusively be located on the teeth and not on the gingiva. If the tray adapts insufficiently, allowing the bleaching agent to leak, it can lead to gingival irritations over a longer period of application.
64 Reservoir formation for the bleaching agent in the tray adjacent to the tooth
A reservoir for the bleaching agent is formed on the facial surface in the tray. The reservoir extends to within approx. 1 mm of the tray margin.
65 Making the bleaching tray
Left: Light-cured blocking resin is placed where the reservoirs are going to be located.
Right: The overextended tray is cut to its right extension.
66 Completing the tray
Left: The tray margins are readapted with a flame in order to enable optimal marginal adaptation.
Right: Finished bleaching tray.
In order to achieve a greater effect with the bleaching agent, a reservoir is created on the tooth surface by means of a light-cured plastic. The tray material is available in thicknesses of 0.053–0.06 inches. The thicker tray material is preferred for patients with a tendency to grind their teeth.
The illustrations (Figures 64–66) show the procedure for making a bleaching tray. The technique can also be used to manufacture a medicament carrier.
In-Office Bleaching
In-office bleaching is carried out using more aggressive materials and consequently leads to quicker results. Products with a higher concentration of bleaching agents (e.g., Quickstart with 35% carbamide peroxide or Accel with 35% H2O2) are mainly used. Because of their aggressivity, one must keep an eye on the bleaching process and make sure that the gingiva is sufficiently protected by the rubber dam.
The drawback of in-office bleaching is the expensive treatment time.
Indications
—Goal: fast result
—The patient prefers the treatment to be conducted in the office
—Only single teeth to be bleached
—As a preprosthetic procedure
Contraindications
—Patients with hypersensitive teeth
—Patients with large fillings
Treatment Procedure
1. Diagnosis and treatment planning as in the case of the home bleaching procedure (oral diagnosis, professional tooth cleaning, radiographs).
2. Color determination together with the patient.
3. Preoperative photographs.
4. Placing the rubber dam.
5. Place bleaching agent and replace after 10–20 minutes. A treatment lasts 30 to a maximum of 60 minutes and normally causes a color change of 1 to 1.5 shades on the Vita color scale.
6. After the rubber dam has been removed, remineralize the teeth with a fluoride gel.
The treatment can be repeated two to four times.
Possible Postoperative Complications
Gingiva etching: Let the patient rinse for a few minutes. Most gingiva irritations disappear after two hours.
Pain: Raised level of sensitivity usually vanishes within a few days. Use toothpaste for hypersensitive teeth as a possible accompanying treatment.
67 Bleaching procedure
Since one is working with highly concentrated bleaching agents, it is necessary that a rubber dam be applied before treatment is carried out. Fresh bleaching agent is placed on the teeth at 10-minute intervals. The bleaching process can be accelerated by exposing the tooth being bleached to the light of a polymerization lamp.
68 Effect of a 30-minute in-office bleaching treatment
69 Bleaching agents for in-office bleaching
Highly concentrated carbamide peroxide (35%) or concentrated hydrogen peroxide (35%) is used for in-office bleaching.
70 Useful bleaching agents, composition, and effects of external factors
Power Bleaching with Superoxol
1. The patient's face and, above all, the eyes must be protected since one is working with aggressive chemicals. Dentist and patient should wear goggles; cover the patient's face.
2. Protect the gingiva with Vaseline or Orabase in case the rubber dam leaks.
3. Position the rubber dam. The holes should be made small to optimize the sealing ability. Invert the rubber dam.
4. Clean the teeth with pumice and water; do not use a polishing paste containing fluoride.
5. Stir the bleaching paste and place it on the teeth.
6. The additional use of heat and light speeds up the bleaching process. It is important, though, that the patient does not experience any pain due to the heat being used. Most patients can tolerate 50—60 °C. These temperatures are also tolerated when making a hydrocolloid impression. Do not use the heat on the tooth for more than one minute. Then wait for another minute before the heat is reapplied.
7. The power bleaching process should be stopped after 10 –30 minutes, even if the goal has not been achieved. If pain is registered, the treatment must be stopped immediately.
8. Remove the source of heat and wait five minutes so that the teeth can cool down. Then, the remaining bleaching agent is rinsed away using plenty of water and sucked away.
9. Finish the procedure by treating all teeth with a neutral sodium fluoride gel for two to three minutes, whereupon the rubber dam is removed. The patient should then rinse the mouth carefully.
Possible Side Effects
Instruct the patient that the teeth may be somewhat sensitive over the next few days. After approximately two weeks, the outcome of the bleaching treatment is reassessed and, if necessary, the teeth are bleached again.
Patient Information for Home Bleaching
Home bleaching of teeth with a bleaching tray is a new treatment that is controlled and supervised by the dentist. It is a simple and very effective technique used to brighten the teeth. An important component of this treatment is an individually made and precisely fitting bleaching tray. This tray prevents the bleaching agent from becoming diluted too quickly by the saliva and from leaking out into the oral cavity. It is the tray that distinguishes this bleaching method from those that are bought as kits in a drugstore.
Carbamide peroxide or hydrogen peroxide is used as bleaching agent. They are usually contained in gels based on glycerin. All degradation products of the bleaching agents are also materials produced naturally in the body and are consequently harmless. The oxygen released produces the bleaching effect. If the patient is allergic to any constituent in the bleaching material, the bleaching treatment should not be started or continued.
Peroxides have been used for many years as oral antiseptics (disinfectant mouthrinses). Only recently have they served as bleaching agents for teeth.
Possible side effects of bleaching are:
1. Gingiva irritation
2. Temporary hypersensitivity of the dental necks
3. Short-term nausea
4. Pain in the temporomandibular joint region
The bleaching agents bleach only natural tooth structures. Large fillings or crowns are not bleached and may have to be renewed later, since they no longer match the tooth color of the bleached teeth.
Instructions for Home Bleaching
1. Clean mouth and teeth.
2. Place a small quantity of the bleaching gel into the tray and position the tray slowly.
3. Remove excess bleaching agent.
4. Do not eat while you are wearing the tray. Do not chew on the tray. Do not try to suck out bleaching agents from the tray.
5. Leave tray in place for 45-60 minutes.
6. Remove the tray. Rinse mouth with water.
7. If desired, repeat steps 2 to 6. Increase the bleaching time step-by-step.
8. Never leave the tray in place for the entire night. Maximum bleaching time is five hours per day.
9. If you should have any problems with the bleaching treatment, stop bleaching and call your dentist's office.
10. Return to the dental office as agreed for checkups on the bleaching treatment.
What You, the Patient, Must Observe
Patients should not smoke during the bleaching process. It is possible that the effect of carcinogens present in cigarette smoke can be enhanced with the relase of oxygen.
Pregnant and nursing mothers should not bleach their teeth. It is not yet known whether there could be an interaction between free oxygen radicals released and other substances and whether they can affect the pregnancy. Patients with very sensitive dental necks should not bleach their teeth.
Attainable Coals of the Bleaching Treatment
The dentist has determined the tooth color on a shade guide before the bleaching treatment starts. One can expect the teeth to become about one to two shades brighter.
The average treatment time with the home bleaching method amounts to two to six weeks. The first results are usually already recognizable after five days. Particularly strong discolorations can make a longer treatment period necessary. Strong discolorations in deeper layers of the tooth cannot be altered through the bleaching treatment.
Yellow-brown color changes (age-induced stains) can usually be bleached very easily. According to type and cause of the discoloration repetition (after approx. one to two years) of bleaching is necessary. Therefore, the individually fabricated bleaching tray must be stored safely.
Bleaching Nonvital Teeth
When bleaching nonvital teeth, the bleaching agent is placed into the pulp chamber of the tooth. This method is effective when one wants to brighten nonvital teeth that have changed color after root canal treatments.
History and State of the Art of the Technique
One of the first successful attempts to perform internal bleaching was described by Brown (1965). He mixed sodium perborate and hydrogen peroxide and placed the mixture into the pulp chamber. In 1963, Nutting and Poe proposed the technique in combination with the bleaching process of vital teeth. They used Superoxol, a stabilized hydrogen peroxide, and mixed it with sodium perborate. The mixture was put into the pulp chamber, which was then closed. Since the bleaching process extends over a relativel long period, it has also been called “walking bleach” in the American literature. If the internal dentin has been etched with 37% phosphoric acid before the bleaching agent is placed in the pulp chamber, the penetration of the bleaching agent is increased.
The bleaching process can be accelerated further if the tooth is heated. The bleaching agent in the pulp chamber is renewed after a few minutes' interval and heat applied to the tooth surface. This is known as “power bleaching.” This treatment requires chemicals such as Superoxol (30% stabilized H2O2) and sodium perborate (Amosan by Oral B or sodium peroxyborate-monohydrate from a drugstore). The two products (Superoxol and sodium perborat) are mixed together.
71 Bleaching nonvital teeth
Left: The coronal part of the root canal filling is removed.
Middle: Bleaching agent is inserted into the pulp chamber.
Right: The pulp chamber is closed with a temporary filling material (Cavit). After multiple changes of the bleaching agent and an approx. two-week total treatment period, the bleaching process is completed.
72 Placing the bleaching agent in the pulp chamber
Side Effects and Treatment Preparation
Patients must be informed about effects and side effects of the bleaching process. One of the side effects is that bleaching can cause internal root resorption. The teeth can become brittle with repeated internal bleaching and after time this can cause spontaneous fracture of the clinical crown. Root canal treatments should be completed before bleaching therapy is begun.
The coronal part of the root canal filling must be completely removed, including residual filling material located in the pulp horns. If it is a root canal filling with silver thread, the entire filling needs to be removed and filled again with gutta-percha. The root canal filling must be sealed before bleaching. A small quantity of glass ionomer cement is suitable for this purpose.
Treatment Procedure for Power Bleaching
1. Determine tooth color and take photographs.
2. Isolate the treatment area with rubber dam.
3. Seal the root canal filling with a resin-modified glass ionomer cement. Perform radiographic control.
4. Etch the pulp chamber for no longer than 30 seconds with a 37% phosphoric acid.
5. Mix Superoxol and sodium perborate. Place it in the pulp chamber.
6. Apply heat for two to five minutes. Then remove the bleaching mixture and bring in new bleaching gel. Repeat this process every five minutes over a period of 30 minutes. Overly strong heat development can lead to root resorption.
7. When the bleaching process is finished, the tooth should be rinsed and the tooth color should be checked. Under some circumstances another bleaching session may be necessary.
8. To neutralize the pulp chamber, calcium hydroxide paste is brought into the tooth and left there for about two days. Place a tight temporary restoration.
9. If after two days the tooth color has attained a result which the patient is happy with, restoration of the tooth can take place. If another bleaching process is needed within the foreseeable future, a restoration should be made through which access to the pulp chamber can be gained in the future.
Walking Bleach
The first four steps are identical to those for power bleaching.
5. Place the bleaching agent in the pulp chamber.
6. Close the opening with a Cavit or an IRM restoration. Patients must be informed that the bleaching agent present in the pulp chamber releases gases, which could cause the temporary restoration to fall out.
7. The bleaching agent remains in the tooth for between two days and one week.
8. Repeat the process.
9. Restore the tooth.
Internal bleaching should not be repeated more than four times, because the inner tooth structure becomes weakened, increasing the risk that a crown fracture may occur.
73 Bleaching nonvital teeth
The bleaching agent is placed in the pulp chamber.
74 External bleaching
In addition to internal bleaching of the nonvital tooth, all teeth can simultaneously be given an external bleaching with a bleaching tray.
Courtesy of Ultradent Prod. Inc.
Long-term Results
In 1989 Haywood began a scientific study of the bleaching procedures. In 1994, he presented the long-term results of 300 patients.
Seventy-three percent of the patients were satisfied with the bleaching results after three years. Only a few noticed a slight darkening of the teeth. A total of 3% of the patients required a regular follow-up bleaching. No patient reported postoperative sensitivity, gingiva irritation, or had had a tooth fracture. Teeth of patients with an orange-brown discoloration were brightened by about 3.3 shades on the Vita color scale guide, and this result was confirmed after three years.
A survey among dentists by the CRA (Christensen 1997) showed that:
91% of the surveyed dentists bleach teeth
79% were very satisfied with the result
12% were disappointed
62% observed tooth hypersensitivities in 10.7% of all cases
45% said that 5.6% of the patients had gingiva irritations
2.1% recognized systemic troubles in 0.2% of the cases
18.8% had not registered any side effects
75 Before start of bleaching treatment
The patient's smile before treatment began.
76 After bleaching treatment
A follow-up picture after bleaching treatment was completed.
Courtesy of Ultradent Prod. Inc.
How Long Do Bleached Teeth Remain White?
After approximately one year, patients should give their teeth a slight after-bleaching. The original tooth color returns slowly over a time period of one to four years if no after-bleaching is carried out. The slow darkening process of the teeth depends on the original color. Light-yellow color changes do not come back as quickly as gray colors. In the case of younger patients the color change is retained longer than with older patients. It must therefore be clear to the patient that after-bleaching may occasionally become necessary. Because of that, the bleaching tray should be stored in a safe place.
Special whitening toothpastes support the bleaching process very greatly and should be used at regular intervals. Normally, patients who have their teeth bleached are well aware of their teeth and return regularly to the dental hygienist. Tooth-color can thus be reassessed and after consultation with the dental hygienist a schedule for after-bleaching can be outlined. It is quite difficult for the patient to properly notice the slow change in tooth color. Here, the guidance of a dental hygienist can be very helpful.
Micro Abrasion Method
Micro abrasion is indicated for solid color spots found in the uppermost tooth surfaces. Such color inclusions do not disappear through bleaching.
History
At the beginning of the 20th century, Black already described the micro abrasion procedure using hydrochloric acid. In 1984, McCloskey used pumice mixed with 18% hydrochloric acid to remove color changes on tooth surfaces. Six years later the Primier company brought the product Prema (Primier Enamel Micro Abrasion) onto the market. Prema consisted of pumice mixed with 10% hydrochloric acid. Micro abrasion can be combined with bleaching.
Treatment Planning
Superficial color changes (white spots, fluorosis, and slight tetracycline discolorations) can be removed with the micro abrasive procedure. Hydrochloric acid is a very aggressive liquid. Electron microscopic studies have shown that 18% hydrochloric acid removes approximately 10μm enamel (7–22 μm) in five seconds. Because of this, the micro abrasive procedure should only be used for short time intervals (five seconds). A maximum of five repeated applications should not be exceeded.
77 Status before micro abrasion therapy and bleaching
In the case of micro abrasion therapy, pumice and an approx. 15% hydrochloric acid solution are used to remove the outermost enamel layer. In addition to this treatment, external bleaching can be carried out.
78 Result of treatment
Result achieved after completed micro abrasion therapy. An external bleaching treatment was conducted simultaneously.
Materials
Rubber dam, Dappen dish, 12-18% hydrochloric acid, pumice, sodium bicarbonate, fluoride paste, and possibly a bleaching gel.
Treatment Procedure
1. Perfect isolation with rubber dam: If this is not sufficiently tight, it should be additionally sealed by means of a ligature or liquid rubber dam. Patient, dentist, and dental assistant should all wear goggles.
2. Apply the acid: Mix 12–18% hydrochloric acid with pumice. This mixture is then placed on the tooth regions that are discolored. Now this paste is distributed for five seconds over the surface of the tooth with an extra slow contra-angle handpiece and a rubber polishing cup, with which the area is lightly polished. After completion, all of the hydrochloric acid-pumice mixture is immediately rinsed away with thorough suctioning, and afterwards the tooth color is checked.
3. Repetition: This process can be repeated up to a maximum of four times. However, if no drastic improvement can be seen after two to three applications, the treatment should be stopped.
4. Polishing and fluoride treatment of the teeth.
