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Treatment changes in Class II malocclusion
READERS’ FORUM
Letters to the editor* Are we moving in the right direction to improve Angle’s classification? I enjoyed the article in the September 2007 issue (Snyder R, Jerrold L. Black, white, or gray: finding commonality on how orthodontists describe the areas between Angle’s molar classifications. Am J Orthod Dentofacial Orthop 2007;132: 302-6) and the follow-up letter from Dr Katz (Angle’s classification revisited. Am J Orthod Dentofacial Orthop 2007;132:716-7) in the December issue. Recently, I received a manuscript from a well-known orthodontic journal for review. It described a new way for determining skeletal Class I, Class II, and Class III patients. The orthodontic community is trying to overcome the shortcomings of the original Angle classifications, but we are going in the same direction as we have done for the past century: new lines, angles, ratios, cutoff points, and parameters are defined to improve the classification. But it seems, at least to me, that this direction will not lead us to a suitable place. The old problem still persists, and that is our methodology. We always try to define cutoff points; that is the very problem. For example, we think that a patient should belong to only one of the Class I, Class II, or Class III groups. That is because of our “0 or 1” way of thinking: everything should be either white or black, and there is no place for gray. I think the problem cannot be solved by defining more new parameters, but fuzzy logic concepts can give us a solution.1,2 This has been used in medicine, and it is gaining its place in dentistry.3 Let me explain it a bit to make the point clear. An Iranian, Dr Lotfizadeh, first used the word “fuzzy” in Proceedings of the IRE, a leading engineering journal, in 1962. Today, fuzzy logic lessons usually begin with a typical example: how do you define a tall woman? You might answer that any woman taller than 180 cm is tall. But what about a woman whose height is 179.5 cm? Is it fair to put her in the short women category for just 0.5 cm? If you change the limit of tallness from 180 to 179.5 cm, the same questions arise about a woman with the height of 179 cm. The problem is not the exact limit of tallness, it is the philosophy of our designation system. According to the fuzzy logic theory, every woman is both tall and short at the same time! There are 2 categories in this regard: tall and short. Every woman belongs to both of these categories with different degrees of membership. A woman who is 180 cm can be designated as 80% tall and 20% short. But one with the height of 150 cm can be considered 20% tall and 80% short. Almost everything in our world has fuzzy characteristics, and it is not usually possible to define clear-cut points. Tall women, short men, warm days, high-pressure gas, small crowd, medium viscosity, and hot shower water are just a few examples of the fuzzy *The viewpoints expressed are solely those of the author(s) and do not reflect those of the editor(s), publisher(s), or Association.
336
sets we use in daily conversations. As the complexity of a system increases, it becomes more difficult and eventually impossible to make a precise statement about its behavior, eventually arriving at a point of complexity where the fuzzy logic method is the only way to get at the problem. The inputs from our environment are so complex and numerous that fuzzy logic has been the only way for humans to analyze them for survival. There are already hundreds of successful commercial products based on fuzzy logic, everything from self-focusing cameras to washing machines that adjust themselves according to how dirty the clothes are, automobile engine controls, anti-lock braking systems, color film developing systems, subway control systems, and computer programs trading successfully in the financial markets. Likewise, isn’t it possible to define a new system in which a patient is both Class I and Class II at the same time, but with different degrees of membership? I think it is. Defining new parameters is valuable but does not solve the problem. Thinking orthodontists are invited to develop a new method based on the fuzzy logic concept. Hassan Noroozi Tehran, Iran Am J Orthod Dentofacial Orthop 2008;133:336 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2007.12.019
REFERENCES 1. Kosko B. Fuzzy thinking, the new science of fuzzy logic. New York: Hyperion; 1993. 2. Kosko B. Fuzzy logic for ‘just plain folks’. Oxford, United Kingdom: Oxford University Press; 1998. 3. Noroozi H. Orthodontic treatment planning software. Am J Orthod Dentofacial Orthop 2006;129:834-7.
Treatment changes in Class II malocclusion The online-only article, “Soft-tissue treatment changes in Class II Division 1 malocclusion with and without extraction of maxillary premolars” (Janson G, Fuziy A, Freitas MR, Henriques JFC, Almeida RR. Am J Orthod Dentofacial Orthop 2007;132:729.e1-729.e8), was an interesting read. Although the study was well structured and had much relevance to clinical orthodontics, certain aspects need clarification. Headgear was an important component in the overall mechanics used for treating patients in both groups. Yet, there was no description of the type of headgear, the amount and direction of force applied relative to the center of resistance of the maxillary first molars, and the duration of its wear. Perhaps the retrospective nature of the study did not permit such quantifications. Additionally, an important factor of
American Journal of Orthodontics and Dentofacial Orthopedics Volume 133, Number 3
compliance with the headgear for the treated sample was not mentioned in either the Material and Methods or the Discussion section. (Although the authors mentioned compliance in the introduction as a possible factor affecting headgear wear, they did not relate its effect to their sample). Surely, with 44 patients in the study, it is unrealistic to expect equal compliance, especially for group 1 in which presumably the headgear was used for a longer time (for both distalization and retraction). It is a well-known fact that, with increasing treatment time, compliance decreases and lack of compliance might in turn cause longer treatment time.1 This could have played a role in the longer treatment time for the group 1 patients over group 2. Perhaps using a noncompliance-based distalizing appliance could have eliminated this confounding factor. Table III shows that the maxillae in both groups were normally positioned (SNA ⬇ 81°) with respect to the cranium, whereas the mandible was retrognathic. We believe that selecting a sample with prognathic maxilla or normally positioned mandible would have yielded more reliable results because most of the treatment in the sample was directed toward the maxillary arch, whereas the Class II skeletal discrepancy was essentially due to a retrognathic mandible. Regarding the cephalometric measurements, the authors basically relied on cranial-base superimpositions to evaluate the treatment effects on the dentofacial and soft-tissue structures. However, to delineate specifically the dental changes from the overall facial changes, local superimpositions on maxillary and mandibular structures as described by Bjork and Skieller2 could have yielded more reliable results. This becomes more pertinent because of the substantial growth the patients might have had during treatment, since their mean ages at the start and end of treatment were 12.50 and 15.12 years, respectively. Madhur Upadhyay Farmington, Conn Sumit Yadav Indianapolis, Ind Am J Orthod Dentofacial Orthop 2008;133:336-7 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2008.01.010
REFERENCES 1. Lyons EK, Ramsay DS. Preliminary tests of a new device to monitor orthodontic headgear use. Semin Orthod 2002;8:29-34. 2. Bjork A, Skieller V. Normal and abnormal growth of the mandible: a synopsis of longitudinal cephalometric implant studies over a period of 25 years. Eur J Orthod 1983;5:1-46.
Authors’ response We appreciated the interest of Drs Upadhyay and Yadav in our article and their concerns with some methodologic aspects, which we would like to clarify. We did not provide additional details regarding the type of headgear used, the direction of force applied
Readers’ forum 337
relative to the center of resistance of the maxillary first molar, and the duration of its wear because these factors did not seem to influence the aspects under investigation. There is no evidence that nonextraction treatment of a complete Class II malocclusion with cervical or high-pull headgear produces a different amount of lip retraction. Because the groups were cephalometrically similar, it would be likely that the headgear used would also be similar. Regarding the duration of its wear, it would be expected that the nonextraction group would have a longer usage time than the 2-maxillary-premolar extraction group because anchorage requirements in nonextraction protocol are greater than in the 2-maxillary-premolar extraction protocol.1-4 Since treatment time was matched between the groups, more usage time would have been required in the nonextraction group. Therefore, differences in headgear usage times would be intrinsic characteristics of these 2 treatment protocols, which had to have matching treatment times. Matching treatment times was an essential requirement for comparison, to exclude the influence of growth. These data could have been provided, but, because there seemed to be no evidence that they would affect the comparison, they were not included. Perhaps the amount of force—a mean of 400 g in both groups— could have been reported. Nevertheless, because it was similar in the groups, this did not affect the comparison. Group 1 had the patients with best compliance, and group 2 had the worst compliance. This can be stated because, as explained in the discussion, it has already been shown that the 2-maxillary-premolar extraction protocol has a significantly shorter treatment time than the nonextraction protocol.4 Consequently, to be able to match the groups’ treatment times, we had to exclude the worst compliers of group 1 and the best compliers of group 2 from our original sample. Thus, contrary to the observation of Drs Upadhyay and Yadav, there was no statistically significant difference between them, because every effort was made to have patients in the nonextraction group with the shortest treatment times and those with the longest treatment times in the extraction group to match them. We agree that a comparison with a noncompliance-based distalizing appliance would be interesting. However, because these appliances are usually used to treat milder Class II malocclusions, it would probably be even harder to match malocclusion severity.5-14 Because of the retrospective nature of the study and the mentioned difficulties in matching the groups as much as possible, ending with 22 patients in each group from the larger original samples, we could not be more restrictive by including an additional requirement of selecting only those with a prognathic maxilla and a normally positioned mandible. However, it is also unlikely that this would affect the comparison because there were no significant differences in any pretreatment cephalometric variable between the groups. We were not concerned about evaluating whether the correct treatment protocol was used in these subjects, but only whether there were differences in the soft tissues after treatment.
Letters to the editor* Are we moving in the right direction to improve Angle’s classification? I enjoyed the article in the September 2007 issue (Snyder R, Jerrold L. Black, white, or gray: finding commonality on how orthodontists describe the areas between Angle’s molar classifications. Am J Orthod Dentofacial Orthop 2007;132: 302-6) and the follow-up letter from Dr Katz (Angle’s classification revisited. Am J Orthod Dentofacial Orthop 2007;132:716-7) in the December issue. Recently, I received a manuscript from a well-known orthodontic journal for review. It described a new way for determining skeletal Class I, Class II, and Class III patients. The orthodontic community is trying to overcome the shortcomings of the original Angle classifications, but we are going in the same direction as we have done for the past century: new lines, angles, ratios, cutoff points, and parameters are defined to improve the classification. But it seems, at least to me, that this direction will not lead us to a suitable place. The old problem still persists, and that is our methodology. We always try to define cutoff points; that is the very problem. For example, we think that a patient should belong to only one of the Class I, Class II, or Class III groups. That is because of our “0 or 1” way of thinking: everything should be either white or black, and there is no place for gray. I think the problem cannot be solved by defining more new parameters, but fuzzy logic concepts can give us a solution.1,2 This has been used in medicine, and it is gaining its place in dentistry.3 Let me explain it a bit to make the point clear. An Iranian, Dr Lotfizadeh, first used the word “fuzzy” in Proceedings of the IRE, a leading engineering journal, in 1962. Today, fuzzy logic lessons usually begin with a typical example: how do you define a tall woman? You might answer that any woman taller than 180 cm is tall. But what about a woman whose height is 179.5 cm? Is it fair to put her in the short women category for just 0.5 cm? If you change the limit of tallness from 180 to 179.5 cm, the same questions arise about a woman with the height of 179 cm. The problem is not the exact limit of tallness, it is the philosophy of our designation system. According to the fuzzy logic theory, every woman is both tall and short at the same time! There are 2 categories in this regard: tall and short. Every woman belongs to both of these categories with different degrees of membership. A woman who is 180 cm can be designated as 80% tall and 20% short. But one with the height of 150 cm can be considered 20% tall and 80% short. Almost everything in our world has fuzzy characteristics, and it is not usually possible to define clear-cut points. Tall women, short men, warm days, high-pressure gas, small crowd, medium viscosity, and hot shower water are just a few examples of the fuzzy *The viewpoints expressed are solely those of the author(s) and do not reflect those of the editor(s), publisher(s), or Association.
336
sets we use in daily conversations. As the complexity of a system increases, it becomes more difficult and eventually impossible to make a precise statement about its behavior, eventually arriving at a point of complexity where the fuzzy logic method is the only way to get at the problem. The inputs from our environment are so complex and numerous that fuzzy logic has been the only way for humans to analyze them for survival. There are already hundreds of successful commercial products based on fuzzy logic, everything from self-focusing cameras to washing machines that adjust themselves according to how dirty the clothes are, automobile engine controls, anti-lock braking systems, color film developing systems, subway control systems, and computer programs trading successfully in the financial markets. Likewise, isn’t it possible to define a new system in which a patient is both Class I and Class II at the same time, but with different degrees of membership? I think it is. Defining new parameters is valuable but does not solve the problem. Thinking orthodontists are invited to develop a new method based on the fuzzy logic concept. Hassan Noroozi Tehran, Iran Am J Orthod Dentofacial Orthop 2008;133:336 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2007.12.019
REFERENCES 1. Kosko B. Fuzzy thinking, the new science of fuzzy logic. New York: Hyperion; 1993. 2. Kosko B. Fuzzy logic for ‘just plain folks’. Oxford, United Kingdom: Oxford University Press; 1998. 3. Noroozi H. Orthodontic treatment planning software. Am J Orthod Dentofacial Orthop 2006;129:834-7.
Treatment changes in Class II malocclusion The online-only article, “Soft-tissue treatment changes in Class II Division 1 malocclusion with and without extraction of maxillary premolars” (Janson G, Fuziy A, Freitas MR, Henriques JFC, Almeida RR. Am J Orthod Dentofacial Orthop 2007;132:729.e1-729.e8), was an interesting read. Although the study was well structured and had much relevance to clinical orthodontics, certain aspects need clarification. Headgear was an important component in the overall mechanics used for treating patients in both groups. Yet, there was no description of the type of headgear, the amount and direction of force applied relative to the center of resistance of the maxillary first molars, and the duration of its wear. Perhaps the retrospective nature of the study did not permit such quantifications. Additionally, an important factor of
American Journal of Orthodontics and Dentofacial Orthopedics Volume 133, Number 3
compliance with the headgear for the treated sample was not mentioned in either the Material and Methods or the Discussion section. (Although the authors mentioned compliance in the introduction as a possible factor affecting headgear wear, they did not relate its effect to their sample). Surely, with 44 patients in the study, it is unrealistic to expect equal compliance, especially for group 1 in which presumably the headgear was used for a longer time (for both distalization and retraction). It is a well-known fact that, with increasing treatment time, compliance decreases and lack of compliance might in turn cause longer treatment time.1 This could have played a role in the longer treatment time for the group 1 patients over group 2. Perhaps using a noncompliance-based distalizing appliance could have eliminated this confounding factor. Table III shows that the maxillae in both groups were normally positioned (SNA ⬇ 81°) with respect to the cranium, whereas the mandible was retrognathic. We believe that selecting a sample with prognathic maxilla or normally positioned mandible would have yielded more reliable results because most of the treatment in the sample was directed toward the maxillary arch, whereas the Class II skeletal discrepancy was essentially due to a retrognathic mandible. Regarding the cephalometric measurements, the authors basically relied on cranial-base superimpositions to evaluate the treatment effects on the dentofacial and soft-tissue structures. However, to delineate specifically the dental changes from the overall facial changes, local superimpositions on maxillary and mandibular structures as described by Bjork and Skieller2 could have yielded more reliable results. This becomes more pertinent because of the substantial growth the patients might have had during treatment, since their mean ages at the start and end of treatment were 12.50 and 15.12 years, respectively. Madhur Upadhyay Farmington, Conn Sumit Yadav Indianapolis, Ind Am J Orthod Dentofacial Orthop 2008;133:336-7 0889-5406/$34.00 Copyright © 2008 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2008.01.010
REFERENCES 1. Lyons EK, Ramsay DS. Preliminary tests of a new device to monitor orthodontic headgear use. Semin Orthod 2002;8:29-34. 2. Bjork A, Skieller V. Normal and abnormal growth of the mandible: a synopsis of longitudinal cephalometric implant studies over a period of 25 years. Eur J Orthod 1983;5:1-46.
Authors’ response We appreciated the interest of Drs Upadhyay and Yadav in our article and their concerns with some methodologic aspects, which we would like to clarify. We did not provide additional details regarding the type of headgear used, the direction of force applied
Readers’ forum 337
relative to the center of resistance of the maxillary first molar, and the duration of its wear because these factors did not seem to influence the aspects under investigation. There is no evidence that nonextraction treatment of a complete Class II malocclusion with cervical or high-pull headgear produces a different amount of lip retraction. Because the groups were cephalometrically similar, it would be likely that the headgear used would also be similar. Regarding the duration of its wear, it would be expected that the nonextraction group would have a longer usage time than the 2-maxillary-premolar extraction group because anchorage requirements in nonextraction protocol are greater than in the 2-maxillary-premolar extraction protocol.1-4 Since treatment time was matched between the groups, more usage time would have been required in the nonextraction group. Therefore, differences in headgear usage times would be intrinsic characteristics of these 2 treatment protocols, which had to have matching treatment times. Matching treatment times was an essential requirement for comparison, to exclude the influence of growth. These data could have been provided, but, because there seemed to be no evidence that they would affect the comparison, they were not included. Perhaps the amount of force—a mean of 400 g in both groups— could have been reported. Nevertheless, because it was similar in the groups, this did not affect the comparison. Group 1 had the patients with best compliance, and group 2 had the worst compliance. This can be stated because, as explained in the discussion, it has already been shown that the 2-maxillary-premolar extraction protocol has a significantly shorter treatment time than the nonextraction protocol.4 Consequently, to be able to match the groups’ treatment times, we had to exclude the worst compliers of group 1 and the best compliers of group 2 from our original sample. Thus, contrary to the observation of Drs Upadhyay and Yadav, there was no statistically significant difference between them, because every effort was made to have patients in the nonextraction group with the shortest treatment times and those with the longest treatment times in the extraction group to match them. We agree that a comparison with a noncompliance-based distalizing appliance would be interesting. However, because these appliances are usually used to treat milder Class II malocclusions, it would probably be even harder to match malocclusion severity.5-14 Because of the retrospective nature of the study and the mentioned difficulties in matching the groups as much as possible, ending with 22 patients in each group from the larger original samples, we could not be more restrictive by including an additional requirement of selecting only those with a prognathic maxilla and a normally positioned mandible. However, it is also unlikely that this would affect the comparison because there were no significant differences in any pretreatment cephalometric variable between the groups. We were not concerned about evaluating whether the correct treatment protocol was used in these subjects, but only whether there were differences in the soft tissues after treatment.