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1、A STUDY OF TOOTH WHITENING: SAFETY, EFFICACY AND MECHANISM OF ACTIONGerard KugelA STUDY OF TOOTH WHITENING: SAFETY, EFFICACY AND MECHANISM OF ACTIONA STUDY OF TOOTH WHITENING: SAFETY, EFFICACY AND MECHANISM OF ACTIONDipartimento di Scienze OdontostomatologicheUniversit di SienaViale Bracci53100 Sien
2、aPrepared for the graduate committee on June 13, 2004Gerard KugelBoston, MA, USAThe present thesis is respectfully submitted to Prof Piero Tosi, Rector of the University of Siena, to Prof Alberto Auteri, Dean of the Faculty of Medicine, Universityof Siena, to Prof Egidio Bertelli, vice-Dean of the F
3、aculty of Medicine and Director of the Department of Dental Science, and to Prof Marco Ferrari, Pro-Rector forinternational affairs and President of Dental School, University of Siena. Graduate Committee:PromotorProf. Dr Marco FerrariCommitteeProf. Dr C.L. DavidsonProf. Dr F. TayProf. Dr ToledanoPro
4、f. Dr BalleriThis thesis was prepared at Tufts University School of Dental Medicine, Boston MA, USA and at the School of Dentistry University of Siena, Italy.ContentsChapters1Introduction2A Novel Low Dose Tooth-Whitening Delivery System Efficacy and Safety: A Randomized and Controlled Clinical Trial
5、3 Concentration and Dose ResponseClinical Trial Evaluating the Peroxide Concentration Response of a Polyethylene strip Delivery System over 28 Day4Light activated Tooth Whitening Clinical Evaluation of a 35% Hydrogen Peroxide In-Office Whitening System5Chemical Vs Light activated Tooth WhiteningClin
6、ical Evaluation of Chemical And Light-Activated Tooth Whitening Systems6 Tooth whitening and its Effect on Enamel and DentinDaily Use of Whitening Strips on Tetracycline Stained Teeth: Comparative Results after Two Months7Long Term Hydrogen Peroxide Exposure and its Effect on Dentin Comparative Stud
7、y of 6.5% Hydrogen Peroxide Bleaching Strips on Tetracycline Stain: Clinical Response after Six Months Daily Use 8Paint on delivery systemsA clinical Comparison of two Paint on Whitening Systems9Maintenance of WhiteningClinical Study to Evaluate the Maintenance of Whitening after Bleaching Treatment
8、10 Intrapulpal Temperatures with Light Activated WhiteningEffects of a Light Activated Bleaching System on Pulp Chamber Temperature in Vitro11 Effect of Tooth Whitening on Enamel An exploratory study using SEM to evaluate the enamel surface effects in vivo of a 6% hydrogen peroxide strip bleaching s
9、ystem with that of a 2.5% chlorite tray bleaching system12 Summary and ConclusionsChapter 1INTRODUCTIONThe dental profession has succeeded in reducing caries and periodontal diseases and as a result dental problems have decrease to the point where esthetic improvements are now more attainable 1. One
10、 of the fastest growing areas of esthetic dentistry today is the management of the discolored and hypoplastic dentition. The demand for an improved appearance and a whiter smile has made tooth whitening a very popular dental procedure. Tooth whitening, sometimes referred to as “bleaching”, offers a
11、conservative treatment option for discolored teeth in comparison to resin bonded composites, porcelain veneers or crowns 2,3. Candidates for whitening procedures include patients whose teeth are stained by aging, chromogenic foods, endodontic treatment, tetracycline use and smoking or use of other t
12、obacco products. Success of the treatment depends on type, intensity and location of the discoloration and a careful diagnosis by the practitioner. History of Tooth WhiteningMany attempts to find an effective bleaching method have been made through out the history of dentistry. The desire to have wh
13、iter teeth dates back at least 2000 years ago. During the first century the Romans physicians claimed the use of urine, especially Portuguese, to brush the teeth would whiten the teeth 4. Barber-surgeons used a solution of nitric acid to lighten the teeth after using a course metal file to abrade th
14、e enamel 4, practice until late eighteenth century. In 1895 it was reported the combination use of pyrozone 25% and electricity to bleach the endodontically treated teeth 5. Later on, in 1916, it was stated the use of hypochloric acid to treat endemic fluorosis 6. In 1939 it was advocated the use of
15、 30% hydrogen peroxide, ether and heat to treat fluorosis staining 7. In 1966, it was promoted the combination use of hydrochloric acid and hydrogen peroxide to remove “brown stain from mottled teeth” due to a chronic endemic dental fluorosis 8. The early efforts to whiten teeth relied on the assump
16、tion that the process involved the removal of extrinsic enamel stain. The mechanism of action was poorly understood.It was only on 1970 that Cohen and Parkins first published a method for bleaching the discolored dentin of young adults with cystic fibrosis who has undergone tetracycline treatment 9.
17、 This publication indicated that the mechanism of tooth whitening using hydrogen peroxide involves penetration to the dentin. In 1976, Nutting and Poe introduced the walking bleach technique, which uses 35% hydrogen peroxide and sodium perborate for nonvital teeth bleaching10. The breakthrough in to
18、oth whitening was in 1989 when Haywood and Heymann published the nightguard vital bleaching technique 11. This is procedure is still widely used among the dental community as the take-home bleaching system.Tooth Whitening Systems Tooth whitening with various concentrations of peroxide has been demon
19、strated to be safe and effective in a variety of regimens, including in-office procedures, dentist-prescribed and supervised home treatments and over the counter system approaches 12. Most dental practices in the United States offer some form of tooth whitening system. A) Take- home SystemThe most c
20、ommon regimen is the at-home use for 2 to 4 weeks, based on the color of the teeth at the start of whitening 13,11 .The use of hydrogen peroxide for removing intrinsic stains from vital teeth has been used for many years. Haywood and Heymann published the first article describing night guard vital b
21、leaching in 1989 11. A tray is fabricated from a model of the patients teeth using a soft plastic nightguard. This tray is the loaded with carbamide peroxide gel and seated over the teeth for approximately 2 hours. The most commonly prescribed concentrations are 10% to 22% carbamide peroxide.The adv
22、antage of the take-home systems is the decreased cost when compared to the in office bleaching options. The major disadvantages associated with take-home systems are: (a) they require significant patient compliance with the number of applications usually involving 1-2 hours twice a day or overnight
23、wear, and (b) the entire treatment usually takes at least four weeks.B) In-Office SystemThe most acceptable applications involve are in-office techniques, dentist prescribed take-home systems or a combination of both. The in-office bleaching technique generally employs a 15%, 30% or 35% hydrogen per
24、oxide bleaching agent (heated or non-heated). The advantages of the in-office procedure are: (a) it requires minimal patient compliance, and (b) immediate results are attainable. The disadvantages to this treatment are: (a) chair-time requirement, and (b) cost to the patient. It is important to note
25、 that this procedure usually requires multiple office visits.C) Combination TechniqueBy combining the two techniques (in-office and take-home), there is a reduction in the amount of time and the need for repeated office visits as well as the expense associated with in-office bleaching as a stand-alo
26、ne technique 14. The combined technique increases overall success and patient satisfaction. This procedure involves the use of a high concentration of hydrogen peroxide (35%) delivered chair side for one hour followed by a take home regimen of 5days. This is often followed by an additional chair sid
27、e application. 15D) Whitening StripsA new method involves using a 5.3% hydrogen peroxide-impregnated polyethylene strip (CrestWhitestrips) for 30 minutes twice daily. This method is recommended for maintaining already whitened teeth. It can also be a good option to patients who cannot afford the cos
28、t of other whitening treatment or who do not have the time for multiple dental visits for tray fabrication 13. It was published in 2002 the use of the whitening strips for tetracycline stained teeth 13.Development of this flexible, polyethylene whitening strips allows for consistent bleaching using
29、shorter contact times. Fixing the daily strip regimen at 30 minutes per day, a randomized, double blind, a double placebo-controlled clinical study was conducted to evaluate the effects of increasing the dosing regimen on tooth shade 17 . Also, an in vitro study explored the impact of varying concen
30、tration of carbamide peroxide ranging from 0.4% to 10% on bleaching efficacy and the impact of increasing hydrogen peroxide concentration on bleaching strip efficacy and tolerability under clinical conditions 18. These studies demonstrated that a modest increase in peroxide concentration on a flexib
31、le bleaching strip results in increased whitening effectiveness, without adversely impacting on overall tolerability.E) Light Activated Whitening SystemsThe introduction of light activated devices such as Plasma arc, Light Emitting Diodes (LED), Argon lasers, metal halide and xenon-halogen lights by
32、 dental manufacturers have helped create a public demand for the light enhanced tooth whitening systems. Controversial papers were published evaluating the efficacy of light activated bleaching agents in 2002. The first article reported positive results19. The other articles concluded the opposite f
33、indings 20, 21. These articles either maintained 22 or questioned the results 23. The dental profession still needs more evidence of its effectiveness in order to provide better and more efficient treatment. The high demand for “up to date” dental office by patients and clinicians stimulates manufac
34、turers to inundate the dental profession with advertisements emphasizing that light activated tooth whitening is “the state of the art” and should be part of the armamentarium of the office, with not clear evidence of its usefulness.The use of hydrogen peroxide (H202) for bleaching teeth has been ev
35、ident with use of heat or not 24. In order to gain treatment time, clinicians have attempted to accelerate the degradation of H202 by using heat or light. Cohen and Parkins introduced a technique for bleaching discolored teeth using hydrogen peroxide and a hand-held heating source 9. Recent in vitro
36、 study has shown that the use of intense lights does elevate temperature of the bleaching material and as a result caused an increase in intrapulpal temperature. This may have an impact on post bleaching tooth sensitivity and pulpal health 25 . Another research in vitro has verified that the use of
37、laser-activated hydrogen peroxide did not produce any perceivable colour change 26. Light-activated chair side bleaching systems probably offer the benefit of being less time-consuming while producing faster results. The assumption is that clinically tolerable levels of heat will speed the breakdown
38、 of H2O2 tooth bleaching chemicals and this accelerated H2O2 breakdown will cause teeth to lighten more rapidly per unit time. In a recent study the decomposition of hydrogen peroxide was measured by the amount of oxygen released. The data from this study indicated that at temperatures of up to 85 C
39、 accelerated decomposition of the 35% H2O2 was minimal when compared to the control gel 20.The use of light activated bleaching system to accelerate the bleaching process is still on question and more evidence needs to be gathered in order to make a more precise assertion of its effectiveness.F) Too
40、thpasteMany types of toothpaste are available in the market as tooth whitening products, but only a small number of them show stain removal ability and effectiveness. Most of these toothpastes do not contain bleaching agents in their formulation. The ones that do have very low bleach concentration a
41、nd contact times relatively too short to be effective 27. Whitening toothpastes contain mild abrasives to remove surface stains. The peroxide content in the toothpastes are very low (1% or less), also the exposures of the toothpastes on the tooth is minimal hence any whitening minimal 28.G) Over the
42、 Counter ProductsEasy availability of over the counter whitening products has made whitening of teeth more popular amongst people of all ages. There are different types of over the counter products like whitening dentifrices, tray based, whitening strips and the recently introduced brush application
43、s. The latest inclusion to OTC products is a Brush technique. This technique is non-tray based paint on application. Gingival irritation can be prevented due to the ease in application. Over the counter bleaching kit requires the consumer to use either a prefabricated tray or fabricate their own sem
44、i-molded tray then fill it with supplied bleaching agents. These types are less than ideal because the trays are not custom fitted and the formulation is not sophisticated as those dispensed by the dentist 29.Mechanism of ActionMany studies have been conducted to evaluate the effectiveness of variou
45、s bleaching materials and techniques 27, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 15, 41, 42. The brightening effect of the carbamide peroxide and hydrogen peroxide or of both in a combined technique was reported during the above investigations. The exact mechanism of action is not completely und
46、erstood. Hydrogen peroxide diffuses through the organic matrix of the enamel and dentin 43, 44, 45. Because the radicals have unpaired electrons, they are extremely electrophylic and unstable and will attack most other organic molecules to achieve stability, generating other radicals. These radicals
47、 can react with most unsaturated bonds, resulting in disruption of electron conjugation and a change in the absorption energy of the organic molecules in tooth enamel. Simpler molecules that reflect less light are formed, creating a successful whitening action. This process occurs when the oxidizing agent (hydrogen peroxide) reacts with organic material in the spaces between the inorganic salts in tooth enamel 46. Bleaching PenetrationEnamel is the most dense tissue of the body a study conducted by Bartelstone in 1951 showed the penetration of I-
