- Email: [email protected]
BLEACHING AGENTS: Authors' response
L E T T E R S
study kept the teeth in distilled water. This points again to distilled water, not carbamide peroxide, as being the agent in some studies to decrease microhardness. Knoop microhardness values in an in situ study by Araujo and colleagues1 showed no significant decrease in hardness after 21 days of bleaching with 10 percent carbamide peroxide. Now we have a dilemma— which study do we accept? Bruce A. Matis, D.D.S., M.S.D. Professor and Director of Clinical Research Section Indiana University School of Dentistry Indianapolis 1. Araujo EM, Baratieri LN, Vieira LC, Ritter AV. In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time. J Esthet Restor Dent 2003;15(3):166-73. 2. Basting RT, Rodrigues Junior AL, Serra MC. The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ. Oper Dent 2001;26(6):531-9.
Authors’ response: To answer Dr. Matis’ questions, baseline values were taken one day after the fragments were immersed in distilled and deionized water. Some decrease in microhardness values may occur after immersion in distilled water, as reported by Araujo and colleagues.1 However, additional decreases in microhardness values may be related to the presence of carbopol, which could act as a demineralizing agent as discussed in the article. The placebo continued to decrease in microhardness for an additional two weeks, even though samples were not exposed to distilled water. These low microhardness values at baseline also may be attributed to the flattening pro554
cedures used to obtain a smooth surface for microhardness tests. Perhaps a thin enamel layer remained after leveling and polishing the surfaces, even though an enamel surface without dentin exposure was observed on a stereomicroscope. A recent study conducted by our research group, aiming to evaluate the components in bleaching agents as responsible for a decrease in microhardness values in enamel and dentin, also shows this decrease mainly attributed to the carbopol, and because the specimens were stored in artificial saliva. Although the dental fragments were immersed in artificial saliva during the application of the bleaching agents, this was not enough to allow a recovery of the microhardness values during the first eight hours of the treatment period. The bleaching agents and the tray may have acted as a mechanical barrier, isolating the free contact between the surface of the fragments and saliva, and the saliva used did not include enzymes that could quickly break down hydrogen peroxide and urea, which could allow an increase in microhardness. But an increase was observed over time, as a result of enamel remineralization by artificial saliva. This effect may be stronger in vivo, where a combination of factors may strengthen mineral deposition. Furthermore, it is difficult to compare different study designs, products, regimen application (number of hours or days of duration), preparation and number of specimens, and the statistical analysis employed. In our in vitro study, a split-plot design was used with a long-
term regimen application (eight hours a day for 42 days) while, in our in situ study, a threeweek regimen application was employed in a crossover design that involved 30 volunteers. So these differences make comparisons between studies difficult. Laboratory studies are important to evaluate the interaction between bleaching agents and dental hard tissues, but in vitro results should not be extrapolated to intraoral conditions. While developing in vitro studies, almost all the variables are controlled, and the same does not occur in vivo, due to the combination of different conditions related to patients, saliva composition, diet, use of fluoride and others as observed in the studies performed by Araujo and colleagues1 and Basting and colleagues.2 Both studies used in situ models, while our JADA article showed an in vitro evaluation, and fluoride, diet, natural saliva and toothbrushing abrasion were not considered. Furthermore, differences in values considering the variable “time” were not measured, and we could not state if the decrease in microhardness was significant or not. Although in vitro, in situ and in vivo studies should be evaluated with caution, all studies should be accepted within the limitations of each model adopted. Roberta Tarkany Basting, D.D.S., M.S.D., Ph.D. Coordinating Professor, Master of Science Course in Restorative Dentistry Department of Restorative Dentistry Dentistry Research Center and Dentistry School São Leopoldo Mandic Campinas, Brazil
JADA, Vol. 135, May 2004 Copyright ©2004 American Dental Association. All rights reserved.
L E T T E R S
Mônica Campos Serra, D.D.S., M.S., Sc.D. Professor Department of Restorative Dentistry Ribeirão Preto Dentistry School University of São Paulo Ribeirão Preto, Brazil 1. Araujo EM, Baratieri LN, Vieira LC, Ritter AV. In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time. J Esthet Restor Dent 2003;15(3):166-73. 2. Basting RT, Rodrigues Junior AL, Serra MC. The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ. Oper Dent 2001;26(6):531-9.
THE EBD APPROACH
I appreciated the January JADA article by Drs. Amid Ismail and James Bader, “Evidence-Based Dentistry in Clinical Practice,” because we are all often frustrated when we try a new product that we have read about or heard about, and we do not get the results we expected. As health care professionals, it is important that we have ready access to good, reliable and independent studies on the many techniques and products we use every day. However, I am concerned that getting completely on the medical bandwagon for an “evidence-based approach,” with an emphasis on randomized and double-blind studies, has some significant pitfalls for dentistry. Not everything can be evaluated by that approach. That is because dentistry is still, and always will be, an art as well as a science. Dentistry has fundamental principles that must be applied, just like surgical medicine. In dentistry and surgical medicine, there is no doubt that one of the most significant variables is the skill of the clinician with regard to his or her
ability to execute the technical procedures. Surgical medicine and dentistry are very different from internal medicine. We understand that one can easily construct randomized, blinded and controlled studies for a new pharmaceutical agent. Medical researchers can take a randomized patient population, give coded pills or injections to blinded patients, and then statistically analyze their response. We understand that there is always a placebo factor in every medical and dental encounter, and it is essential to understand where the effect of the relationship between the practitioner and patient ends, and the effect of the treatment begins and ends. However, in medicine they do not pretend to do double-blind studies for surgical procedures, simply because surgeons cannot be blinded from what they are doing. In surgery, various procedures are tried and outcomes compared, but the ultimate judge is the response of the patient. When a surgical procedure is based on sound biology and has been proven to stand the test of time and have merit, the procedure should be performed and included in the protocols, and thus it becomes a standard of care. The authors select occlusal treatment as an example of a procedure that has been applied without “evidence-based protocols” to prove that it is safe and effective. To prove their point, the authors quote an article by Forssell and colleagues,1 a literature review of studies on the effectiveness of occlusal treatment on temporomandibular dysfunction, or TMD. The au-
thors state that the studies do not prove that there is a direct relationship between bite treatment and TMD. Below is part of the conclusion from the Forssell and colleagues article1 (the italics are mine): The overall quality of the trials was fairly low, the mean quality score was 0.43/1.00 (range 0.12-0.78). The most obvious methodological shortcomings were inadequate blinding, small sample sizes, short follow-up times, great diversity of outcome measures and numerous control treatments, some of unknown effectiveness. Splint therapy was found superior to 3, and comparable to 12 control treatments, and superior or comparable to 4 passive controls, respectively. Occlusal adjustment was found comparable to 2 and inferior to one control treatment and comparable to passive control in one study. Because of the methodological problems, only suggestive conclusions can be drawn. The use of occlusal splints may be of some benefit in the treatment of TMD. Evidence for the use of occlusal adjustment is lacking. There is an obvious need for well designed controlled studies to analyze the current clinical practices.
The fact that the writers could not solve bite problems is only proof of the lack of standards in the studies. The reality is that there is a 75-year history of dentists researching, documenting and providing this type of treatment for their patients. Thousands of articles have been published and hundreds of textbooks written by such noted and dedicated dental practitioners and researchers as Peter Dawson, Parker Mahan, L.D. Pankey, Peter Neff, Charles Stuart, Bob Lee, Clyde Schyler and on and on. Tens of thousands of dentists who have studied with these leaders provide appropriate and effective bite treatment for their patients
JADA, Vol. 135, May 2004 Copyright ©2004 American Dental Association. All rights reserved.
555
study kept the teeth in distilled water. This points again to distilled water, not carbamide peroxide, as being the agent in some studies to decrease microhardness. Knoop microhardness values in an in situ study by Araujo and colleagues1 showed no significant decrease in hardness after 21 days of bleaching with 10 percent carbamide peroxide. Now we have a dilemma— which study do we accept? Bruce A. Matis, D.D.S., M.S.D. Professor and Director of Clinical Research Section Indiana University School of Dentistry Indianapolis 1. Araujo EM, Baratieri LN, Vieira LC, Ritter AV. In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time. J Esthet Restor Dent 2003;15(3):166-73. 2. Basting RT, Rodrigues Junior AL, Serra MC. The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ. Oper Dent 2001;26(6):531-9.
Authors’ response: To answer Dr. Matis’ questions, baseline values were taken one day after the fragments were immersed in distilled and deionized water. Some decrease in microhardness values may occur after immersion in distilled water, as reported by Araujo and colleagues.1 However, additional decreases in microhardness values may be related to the presence of carbopol, which could act as a demineralizing agent as discussed in the article. The placebo continued to decrease in microhardness for an additional two weeks, even though samples were not exposed to distilled water. These low microhardness values at baseline also may be attributed to the flattening pro554
cedures used to obtain a smooth surface for microhardness tests. Perhaps a thin enamel layer remained after leveling and polishing the surfaces, even though an enamel surface without dentin exposure was observed on a stereomicroscope. A recent study conducted by our research group, aiming to evaluate the components in bleaching agents as responsible for a decrease in microhardness values in enamel and dentin, also shows this decrease mainly attributed to the carbopol, and because the specimens were stored in artificial saliva. Although the dental fragments were immersed in artificial saliva during the application of the bleaching agents, this was not enough to allow a recovery of the microhardness values during the first eight hours of the treatment period. The bleaching agents and the tray may have acted as a mechanical barrier, isolating the free contact between the surface of the fragments and saliva, and the saliva used did not include enzymes that could quickly break down hydrogen peroxide and urea, which could allow an increase in microhardness. But an increase was observed over time, as a result of enamel remineralization by artificial saliva. This effect may be stronger in vivo, where a combination of factors may strengthen mineral deposition. Furthermore, it is difficult to compare different study designs, products, regimen application (number of hours or days of duration), preparation and number of specimens, and the statistical analysis employed. In our in vitro study, a split-plot design was used with a long-
term regimen application (eight hours a day for 42 days) while, in our in situ study, a threeweek regimen application was employed in a crossover design that involved 30 volunteers. So these differences make comparisons between studies difficult. Laboratory studies are important to evaluate the interaction between bleaching agents and dental hard tissues, but in vitro results should not be extrapolated to intraoral conditions. While developing in vitro studies, almost all the variables are controlled, and the same does not occur in vivo, due to the combination of different conditions related to patients, saliva composition, diet, use of fluoride and others as observed in the studies performed by Araujo and colleagues1 and Basting and colleagues.2 Both studies used in situ models, while our JADA article showed an in vitro evaluation, and fluoride, diet, natural saliva and toothbrushing abrasion were not considered. Furthermore, differences in values considering the variable “time” were not measured, and we could not state if the decrease in microhardness was significant or not. Although in vitro, in situ and in vivo studies should be evaluated with caution, all studies should be accepted within the limitations of each model adopted. Roberta Tarkany Basting, D.D.S., M.S.D., Ph.D. Coordinating Professor, Master of Science Course in Restorative Dentistry Department of Restorative Dentistry Dentistry Research Center and Dentistry School São Leopoldo Mandic Campinas, Brazil
JADA, Vol. 135, May 2004 Copyright ©2004 American Dental Association. All rights reserved.
L E T T E R S
Mônica Campos Serra, D.D.S., M.S., Sc.D. Professor Department of Restorative Dentistry Ribeirão Preto Dentistry School University of São Paulo Ribeirão Preto, Brazil 1. Araujo EM, Baratieri LN, Vieira LC, Ritter AV. In situ effect of 10% carbamide peroxide on microhardness of human enamel: function of time. J Esthet Restor Dent 2003;15(3):166-73. 2. Basting RT, Rodrigues Junior AL, Serra MC. The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ. Oper Dent 2001;26(6):531-9.
THE EBD APPROACH
I appreciated the January JADA article by Drs. Amid Ismail and James Bader, “Evidence-Based Dentistry in Clinical Practice,” because we are all often frustrated when we try a new product that we have read about or heard about, and we do not get the results we expected. As health care professionals, it is important that we have ready access to good, reliable and independent studies on the many techniques and products we use every day. However, I am concerned that getting completely on the medical bandwagon for an “evidence-based approach,” with an emphasis on randomized and double-blind studies, has some significant pitfalls for dentistry. Not everything can be evaluated by that approach. That is because dentistry is still, and always will be, an art as well as a science. Dentistry has fundamental principles that must be applied, just like surgical medicine. In dentistry and surgical medicine, there is no doubt that one of the most significant variables is the skill of the clinician with regard to his or her
ability to execute the technical procedures. Surgical medicine and dentistry are very different from internal medicine. We understand that one can easily construct randomized, blinded and controlled studies for a new pharmaceutical agent. Medical researchers can take a randomized patient population, give coded pills or injections to blinded patients, and then statistically analyze their response. We understand that there is always a placebo factor in every medical and dental encounter, and it is essential to understand where the effect of the relationship between the practitioner and patient ends, and the effect of the treatment begins and ends. However, in medicine they do not pretend to do double-blind studies for surgical procedures, simply because surgeons cannot be blinded from what they are doing. In surgery, various procedures are tried and outcomes compared, but the ultimate judge is the response of the patient. When a surgical procedure is based on sound biology and has been proven to stand the test of time and have merit, the procedure should be performed and included in the protocols, and thus it becomes a standard of care. The authors select occlusal treatment as an example of a procedure that has been applied without “evidence-based protocols” to prove that it is safe and effective. To prove their point, the authors quote an article by Forssell and colleagues,1 a literature review of studies on the effectiveness of occlusal treatment on temporomandibular dysfunction, or TMD. The au-
thors state that the studies do not prove that there is a direct relationship between bite treatment and TMD. Below is part of the conclusion from the Forssell and colleagues article1 (the italics are mine): The overall quality of the trials was fairly low, the mean quality score was 0.43/1.00 (range 0.12-0.78). The most obvious methodological shortcomings were inadequate blinding, small sample sizes, short follow-up times, great diversity of outcome measures and numerous control treatments, some of unknown effectiveness. Splint therapy was found superior to 3, and comparable to 12 control treatments, and superior or comparable to 4 passive controls, respectively. Occlusal adjustment was found comparable to 2 and inferior to one control treatment and comparable to passive control in one study. Because of the methodological problems, only suggestive conclusions can be drawn. The use of occlusal splints may be of some benefit in the treatment of TMD. Evidence for the use of occlusal adjustment is lacking. There is an obvious need for well designed controlled studies to analyze the current clinical practices.
The fact that the writers could not solve bite problems is only proof of the lack of standards in the studies. The reality is that there is a 75-year history of dentists researching, documenting and providing this type of treatment for their patients. Thousands of articles have been published and hundreds of textbooks written by such noted and dedicated dental practitioners and researchers as Peter Dawson, Parker Mahan, L.D. Pankey, Peter Neff, Charles Stuart, Bob Lee, Clyde Schyler and on and on. Tens of thousands of dentists who have studied with these leaders provide appropriate and effective bite treatment for their patients
JADA, Vol. 135, May 2004 Copyright ©2004 American Dental Association. All rights reserved.
555