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Rapid palatal expansion, with and without alternating constriction
779
Readers' forum
Table II. Initial age, distribution of the Michigan and Bauru subjects among the evaluated groups, sex distribution between the Michigan and Bauru subjects and among evaluated groups Michigan 8.68 (60.75)
Bauru 8.71 (60.97)
P 0.873*
Group 1A, Michigan 3 Bauru subjects (%) Group 2A, Michigan 3 Bauru subjects (%)
60 70.8
40 29.2
0.869y
Group 2B, Michigan 3 Bauru subjects (%) Group 3A, Michigan 3 Bauru subjects (%)
65.6 66.2
34.4 33.8
Michigan subjects, male 3 female (%)
Male 58.4
Female 41.6
P 0.091y
Bauru subjects, male 3 female (%) Group 1A, male 3 female (%)
44.4 63.3
55.6 36.7
0.106y
Group 2A, male 3 female (%) Group 2B, male 3 female (%)
45.8 68.7
54.2 31.3
Group 3A, male 3 female (%)
46.3
53.7
Variable Initial age, Michigan 3 Bauru subjects (y), Mean (SD)
*t tests.; ychi-square.
ideal sample may not be always achieved under these conditions, but we used vigorous efforts to minimize as much as possible the confounding factors that could have compromised the reliability of the results. Thank you for your interest. Sergio Estelita Barros Porto Alegre, Brazil Guilherme Janson Bauru, Brazil Kelly Chiqueto Porto Alegre, Brazil Am J Orthod Dentofacial Orthop 2016;149:777-9 0889-5406/$36.00 Copyright Ó 2016 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2016.03.007 REFERENCES 1. Martins DR, Janson GR, Pinzan A, Freitas MR, Henriques JFC. Atlas de crescimento craniofacial. S~ao Paulo, Brazil: Santos; 1998. 2. Riolo ML, Moyers RE, McNamara Jr JA, Hunter WS. An atlas of craniofacial growth. Monograph 2. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1974. 3. Anderson AA. Occlusal development in children of African American descent. Types of terminal plane relationships in the primary dentition. Angle Orthod 2006;76:817–23. 4. Bishara SE, Hoppens BJ, Jakobsen JR, Kohout FJ. Changes in the molar relationship between the deciduous and permanent dentitions: a longitudinal study. Am J Orthod Dentofacial Orthop 1988;93:19–28. 5. Kirzioglu Z, Simsek S, Yilmaz Y. Longitudinal occlusal changes during the primary dentition and during the passage from primary dentition to mixed dentition among a group of Turkish children. Eur Arch Paediatr Dent 2013;14:97–103. 6. Guest SS, McNamara Jr JA, Baccetti T, Franchi L. Improving Class II malocclusion as a side-effect of rapid maxillary expansion: a
prospective clinical study. Am J Orthod Dentofacial Orthop 2010; 138:582–91. 7. McNamara Jr JA, Sigler LM, Franchi L, Guest SS, Baccetti T. Changes in occlusal relationships in mixed dentition patients treated with rapid maxillary expansion. A prospective clinical study. Angle Orthod 2010;80:230–8. 8. Zimmerman DW. A note on preliminary tests of equality of variances. Br J Math Stat Psychol 2004;57:173–81.
Rapid palatal expansion, with and without alternating constriction e read the article “Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial” in the October 2015 issue with great interest.1 The study compared the effects of facemask protraction combined with alternating rapid palatal expansion and constriction (Alt-RPE/C) vs rapid palatal expansion alone in maxillary retrusive patients and concluded that AltRPE/C with maxillary protraction positively affects the forward movement of the maxilla compared with rapid palatal expansion alone. The confounding factors such as age and sex were not mentioned in the article. Whereas we do accept that this study was a welldesigned randomized control trial providing considerable evidence for clinicians to adopt the new expansion regimen, we request the authors to consider the following.
W
1.
American Journal of Orthodontics and Dentofacial Orthopedics
In this study, the achievement of a positive overjet was the treatment completion criterion. The authors concluded that Alt-RPE/C with maxillary protraction might result in a greater orthopedic-orthodontic
June 2016 Vol 149 Issue 6
780
2.
3.
4.
Readers' forum
ratio in maxillary movement with similar treatment times. We wonder whether the pretreatment overjet considerations would have altered the duration of time required for different patients and whether this would have made a difference and altered the secondary outcome. The authors correctly observed that the elastic protraction direction is 1 cause for maxillary rotation. They concluded that the palatal plane rotated more counterclockwise in the Alt-RPE/C group, and this was attributed to the expansion protocol. We humbly submit that the pretreatment occlusal plane also has a role to play in the perceived effect. With the mandibular plane angles (MP-SN) of 33.11 and 35.14 in the RPE and Alt-RPE/C groups, respectively, we would like to know why a bonded rapid maxillary expander was not considered. The results also showed a statistically significant increase in the mandibular plane angle after treatment in both groups.2 Although the anteroposterior and vertical planes of space were considered, a note on the dimensional changes brought about in the transverse plane by both regimens would have enabled readers to make an informed decision. Akshaya Pandian Anjana Devi.M.S Prabhakar Veginadu Sridevi Padmanabhan Chennai, India
Am J Orthod Dentofacial Orthop 2016;149:779-80 0889-5406/$36.00 Copyright Ó 2016 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2016.03.004 REFERENCES 1. Liu W, Zhou Y, Wang X, Liu D, Zhou S. Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial. Am J Orthod Dentofacial Orthop 2015; 148:641–51. 2. McNamara JA, Brudon WL. Orthodontics and dentofacial orthopedics.
Authors' response
W
e appreciate the comments of Dr Pandian et al related to our article “Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial.”1 We will attempt to answer their queries in the order presented.
June 2016 Vol 149 Issue 6
During the study, we did find that patients with larger overjet might require more treatment time. Obviously, the value of the pretreatment overjet may represent the degree of maxillary retrusion or mandibular protrusion. Because a large sample was hard to obtain, in our study, we did not restrict the pretreatment overjet to a smaller range. Some investigators have reported a research protocol that may improve research methods when facing such a confounding factor.2,3 In their studies, the posttreatment records were obtained after the same treatment duration in both groups. Due to ethical considerations, we did not use this protocol but performed a more common method, in which lateral cephalometric radiographs were taken at the beginning and end of treatment.4,5 However, to test the homogeneity of the patients in both groups, independent t tests were used to compare the 2 groups before treatment, including their ages and all the cephalometric values listed in our article. No significant difference was observed in the ages between the 2 groups, either integrally or for each sex (P .0.05). No significant difference was found in the cephalometric values before treatment between the 2 groups (P .0.05). The homogeneity of the values at baseline was considered good between the 2 groups. The direction of elastic protraction, the intraoral point of force application, and the position of the maxillary center of resistance may play leading roles in maxillary rotation.6,7 As Dr Pandian et al mentioned, some other causes might also affect the results, such as the vertical movement of the maxillary teeth during treatment, the occlusal plane angle, and the anteroposterior position of the maxillary banded teeth before treatment. We agree that using bonded rapid maxillary expansion might be more helpful for patients with a high mandibular plane. In this study, we focused more on the degree of maxillary forward movement after treatment. Because of the limitation of the sample size, we did not divide the patients into several groups and apply different types of expanders according to their mandibular plane angle. On the other hand, the duration of patient recruitment was 2 years, and the patients were treated according to the plan made at the beginning of the research. Thus, we could not predict their average mandibular plane angles. It is really a good suggestion to investigate the 3dimensional changes of the 2 protocols. We are indeed aware of the limitations of 2-dimensional films. In our study, we did not obtain any valuable results in the transverse direction. However, we have conducted a different clinical trial to investigate the 3-dimensional changes of maxillary protraction combined with
American Journal of Orthodontics and Dentofacial Orthopedics
Readers' forum
Table II. Initial age, distribution of the Michigan and Bauru subjects among the evaluated groups, sex distribution between the Michigan and Bauru subjects and among evaluated groups Michigan 8.68 (60.75)
Bauru 8.71 (60.97)
P 0.873*
Group 1A, Michigan 3 Bauru subjects (%) Group 2A, Michigan 3 Bauru subjects (%)
60 70.8
40 29.2
0.869y
Group 2B, Michigan 3 Bauru subjects (%) Group 3A, Michigan 3 Bauru subjects (%)
65.6 66.2
34.4 33.8
Michigan subjects, male 3 female (%)
Male 58.4
Female 41.6
P 0.091y
Bauru subjects, male 3 female (%) Group 1A, male 3 female (%)
44.4 63.3
55.6 36.7
0.106y
Group 2A, male 3 female (%) Group 2B, male 3 female (%)
45.8 68.7
54.2 31.3
Group 3A, male 3 female (%)
46.3
53.7
Variable Initial age, Michigan 3 Bauru subjects (y), Mean (SD)
*t tests.; ychi-square.
ideal sample may not be always achieved under these conditions, but we used vigorous efforts to minimize as much as possible the confounding factors that could have compromised the reliability of the results. Thank you for your interest. Sergio Estelita Barros Porto Alegre, Brazil Guilherme Janson Bauru, Brazil Kelly Chiqueto Porto Alegre, Brazil Am J Orthod Dentofacial Orthop 2016;149:777-9 0889-5406/$36.00 Copyright Ó 2016 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2016.03.007 REFERENCES 1. Martins DR, Janson GR, Pinzan A, Freitas MR, Henriques JFC. Atlas de crescimento craniofacial. S~ao Paulo, Brazil: Santos; 1998. 2. Riolo ML, Moyers RE, McNamara Jr JA, Hunter WS. An atlas of craniofacial growth. Monograph 2. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1974. 3. Anderson AA. Occlusal development in children of African American descent. Types of terminal plane relationships in the primary dentition. Angle Orthod 2006;76:817–23. 4. Bishara SE, Hoppens BJ, Jakobsen JR, Kohout FJ. Changes in the molar relationship between the deciduous and permanent dentitions: a longitudinal study. Am J Orthod Dentofacial Orthop 1988;93:19–28. 5. Kirzioglu Z, Simsek S, Yilmaz Y. Longitudinal occlusal changes during the primary dentition and during the passage from primary dentition to mixed dentition among a group of Turkish children. Eur Arch Paediatr Dent 2013;14:97–103. 6. Guest SS, McNamara Jr JA, Baccetti T, Franchi L. Improving Class II malocclusion as a side-effect of rapid maxillary expansion: a
prospective clinical study. Am J Orthod Dentofacial Orthop 2010; 138:582–91. 7. McNamara Jr JA, Sigler LM, Franchi L, Guest SS, Baccetti T. Changes in occlusal relationships in mixed dentition patients treated with rapid maxillary expansion. A prospective clinical study. Angle Orthod 2010;80:230–8. 8. Zimmerman DW. A note on preliminary tests of equality of variances. Br J Math Stat Psychol 2004;57:173–81.
Rapid palatal expansion, with and without alternating constriction e read the article “Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial” in the October 2015 issue with great interest.1 The study compared the effects of facemask protraction combined with alternating rapid palatal expansion and constriction (Alt-RPE/C) vs rapid palatal expansion alone in maxillary retrusive patients and concluded that AltRPE/C with maxillary protraction positively affects the forward movement of the maxilla compared with rapid palatal expansion alone. The confounding factors such as age and sex were not mentioned in the article. Whereas we do accept that this study was a welldesigned randomized control trial providing considerable evidence for clinicians to adopt the new expansion regimen, we request the authors to consider the following.
W
1.
American Journal of Orthodontics and Dentofacial Orthopedics
In this study, the achievement of a positive overjet was the treatment completion criterion. The authors concluded that Alt-RPE/C with maxillary protraction might result in a greater orthopedic-orthodontic
June 2016 Vol 149 Issue 6
780
2.
3.
4.
Readers' forum
ratio in maxillary movement with similar treatment times. We wonder whether the pretreatment overjet considerations would have altered the duration of time required for different patients and whether this would have made a difference and altered the secondary outcome. The authors correctly observed that the elastic protraction direction is 1 cause for maxillary rotation. They concluded that the palatal plane rotated more counterclockwise in the Alt-RPE/C group, and this was attributed to the expansion protocol. We humbly submit that the pretreatment occlusal plane also has a role to play in the perceived effect. With the mandibular plane angles (MP-SN) of 33.11 and 35.14 in the RPE and Alt-RPE/C groups, respectively, we would like to know why a bonded rapid maxillary expander was not considered. The results also showed a statistically significant increase in the mandibular plane angle after treatment in both groups.2 Although the anteroposterior and vertical planes of space were considered, a note on the dimensional changes brought about in the transverse plane by both regimens would have enabled readers to make an informed decision. Akshaya Pandian Anjana Devi.M.S Prabhakar Veginadu Sridevi Padmanabhan Chennai, India
Am J Orthod Dentofacial Orthop 2016;149:779-80 0889-5406/$36.00 Copyright Ó 2016 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2016.03.004 REFERENCES 1. Liu W, Zhou Y, Wang X, Liu D, Zhou S. Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial. Am J Orthod Dentofacial Orthop 2015; 148:641–51. 2. McNamara JA, Brudon WL. Orthodontics and dentofacial orthopedics.
Authors' response
W
e appreciate the comments of Dr Pandian et al related to our article “Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial.”1 We will attempt to answer their queries in the order presented.
June 2016 Vol 149 Issue 6
During the study, we did find that patients with larger overjet might require more treatment time. Obviously, the value of the pretreatment overjet may represent the degree of maxillary retrusion or mandibular protrusion. Because a large sample was hard to obtain, in our study, we did not restrict the pretreatment overjet to a smaller range. Some investigators have reported a research protocol that may improve research methods when facing such a confounding factor.2,3 In their studies, the posttreatment records were obtained after the same treatment duration in both groups. Due to ethical considerations, we did not use this protocol but performed a more common method, in which lateral cephalometric radiographs were taken at the beginning and end of treatment.4,5 However, to test the homogeneity of the patients in both groups, independent t tests were used to compare the 2 groups before treatment, including their ages and all the cephalometric values listed in our article. No significant difference was observed in the ages between the 2 groups, either integrally or for each sex (P .0.05). No significant difference was found in the cephalometric values before treatment between the 2 groups (P .0.05). The homogeneity of the values at baseline was considered good between the 2 groups. The direction of elastic protraction, the intraoral point of force application, and the position of the maxillary center of resistance may play leading roles in maxillary rotation.6,7 As Dr Pandian et al mentioned, some other causes might also affect the results, such as the vertical movement of the maxillary teeth during treatment, the occlusal plane angle, and the anteroposterior position of the maxillary banded teeth before treatment. We agree that using bonded rapid maxillary expansion might be more helpful for patients with a high mandibular plane. In this study, we focused more on the degree of maxillary forward movement after treatment. Because of the limitation of the sample size, we did not divide the patients into several groups and apply different types of expanders according to their mandibular plane angle. On the other hand, the duration of patient recruitment was 2 years, and the patients were treated according to the plan made at the beginning of the research. Thus, we could not predict their average mandibular plane angles. It is really a good suggestion to investigate the 3dimensional changes of the 2 protocols. We are indeed aware of the limitations of 2-dimensional films. In our study, we did not obtain any valuable results in the transverse direction. However, we have conducted a different clinical trial to investigate the 3-dimensional changes of maxillary protraction combined with
American Journal of Orthodontics and Dentofacial Orthopedics