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Transverse skeletal and dental asymmetry in adults with unilateral lingual posterior crossbite
Langberg, Arai, and Miner 15
American Journal of Orthodontics and Dentofacial Orthopedics Volume 127, Number 1
7. Ahlgren J, Posselt U. Need of functional analysis and selective grinding in orthodontics. A clinical and electromyographic study. Acta Odont Scand 1963;21:187-226. 8. Kürol J, Berglund L. Longitudinal study and cost-benefit analysis of the effect of early treatment of posterior crossbites in the primary dentition. Eur J Orthod 1992;14:173-9. 9. Thilander B, Wahlund S, Lennartsson B. The effect of early interceptive treatment in children with posterior crossbite. Eur J Orthod 1984;6:25-34. 10. Lam PH, Sadowsky C, Omerza F. Mandibular asymmetry and condylar position in children with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1999;115:569-75. 11. Pirttiniemi P, Kantomaa T, Lahtela P. Relationship between craniofacial and condyle path asymmetry in unilateral posterior crossbite patients. Eur J Orthod 1990;12:408-13. 12. Nerder PH, Bakke M, Solow B. The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study. Eur J Orthod 1999;21:155-66. 13. Schmid W, Mongini F, Felisio A. A computer-based assessment of structural and displacement asymmetries of the mandible. Am J Orthod Dentofacial Orthop 1991;100:19-34. 14. Mongini F, Schmid W. Treatment of mandibular asymmetries during growth—a longitudinal study. Eur J Orthod 1987;9:51-67. 15. Lindner A, Hendrickson C, Odenrick L, Modeer T. Maxillary expansion of unilateral cross-bite in preschool children. Scand J Dent Res 1986;94:411-8. 16. Purcell PD. Effectiveness of posterior crossbite correction during the mixed dentition. J Pedodont 1985;9:302-11. 17. Maurice TJ, Kula K. Dental arch asymmetry in the mixed dentition. Angle Orthod 1998;68:37-44. 18. O’Byrn BL, Sadowsky C, Schneider B, BeGole EA. An evaluation of mandibular asymmetry in adults with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1995;107:394-400. 19. Kantomaa T. The shape of the glenoid fossa affects the growth of the mandible. Eur J Orthod 1988;10:249-54. 20. Pirttiniemi P, Raustia A, Kantomaa T, Pyhtinen J. Relationship between craniofacial and condyle path asymmetry in unilateral cross-bite patients. Eur J Orthod 1991;13:441-5. 21. Cohlmia JT, Ghosh J, Sinha PK, Nanda RS, Currier GF. Tomographic assessment of temporomandibular joints in patients with malocclusion. Angle Orthod 1996;66:27-36. 22. Wood DP, Elliott RW. Reproducibility of the centric relation bite registration technique. Angle Orthod 1994;64:211-9. 23. Major PW, Johnson DE, Hesse KL, Glover KE. Landmark identification error in posterior anterior cephalometrics. Angle Orthod 1994;64:447-54. 24. Shah SM, Joshi MR. An assessment of asymmetry in the normal craniofacial complex. Angle Orthod 1978;48:141-8. 25. Vig PS, Hewitt AB. Asymmetry of the human facial skeleton. Angle Orthod 1975;45:125-9. 26. Svanholt P, Solow B. Assessment of midline discrepancies on the postero-anterior cephalometric radiograph. Trans Eur Orthod Soc 1977;1:261-8. 27. Crawford SD. Condylar axis position, as determined by the occlusion and measured by the CPI instrument, and signs and symptoms of the temporomandibular dysfunction. Angle Orthod 1999;69:103-16. 28. Langberg BJ. An assessment of dental and skeletal asymmetry and condylar position in adult patients with a posterior unilateral lingual crossbite [thesis]. Boston: Harvard School of Dental Medicine; 2002.
29. Alavi DG, BeGole EA, Schneider BJ. Facial and dental arch asymmetries in Class II subdivision malocclusion. Am J Orthod Dentofacial Orthop 1988;93:38-46. 30. Brin I, Ben-Bassat Y, Blustein Y, Ehrlich J, Hochman N, Marmary Y, et al. Skeletal and functional effects of treatment for unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1996;109:173-9. 31. Ben-Bassat Y, Yaffe A, Brin I, Freeman J, Ehrlich J. Functional and morphological-occlusal aspects in children treated for unilateral posterior cross-bite. Eur J Orthod 1993;15:57-63. 32. Williamson EH. The role of cranio-mandibular dysfunction in orthodontic diagnosis and treatment planning. Dent Clin North Am 1983;27:541-60. 33. Roth RH. Temporomandibular pain-dysfunction and occlusal relationships. Angle Orthod 1973;43:136-53. 34. Dawson PE. New definition for relating occlusion to varying conditions of the temporomandibular joint. J Prosthet Dent 1995;74:619-27. 35. Alexander SR, Moore RN, DuBois LM. Mandibular condyle position: comparison of articular mountings and magnetic resonance imaging. Am J Orthod Dentofacial Orthop 1993;104: 230-9. 36. Hinton RJ. Changes in articular eminence morphology with dental function. Am J Orthod 1981;54:439-55. 37. Hinton RJ, McNamara J. Temporal bone adaptations in response to protrusive function in juvenile and young adult rhesus monkeys. Eur J Orthod 1984;6:155-74. 38. Woodside DG, Metaxas A, Altunas G. The influence of functional appliance therapy on glenoid fossa remodeling. Am J Orthod Dentofacial Orthop 1987;92:181-98. 39. Troelstrup B, Møller E. Electromyography of the temporalis and masseter muscles in children with unilateral cross-bite. Scand J Dent Res 1970;78:425-30. 40. Ingerval B, Thilander B. Activity of temporal and masseter muscles in children with a lateral forced bite. Angle Orthod 1975;45:249-58.
COMMENTARY
This article reports that mandibular skeletal asymmetry is not evident in a group of adults with posterior unilateral crossbite when compared with an adult control group. Furthermore, the authors claim that posterior crossbite is due to increased width of the mandible and not a result of transverse deficiency of the maxilla. This study makes use of posteroanterior (PA) radiographs, in preference to previously used submental vertex radiographs, as used by Lam et al1 to assess facial asymmetry in adolescents and O’Byrn et al2 to evaluate skeletal asymmetry in adults. According to Cook,3 as little as 5° of side-to-side head rotation for a PA radiograph caused the side of the asymmetry to switch. In addition, PA radiographs could not be used to determine whether the source of the asymmetry was dentoalveolar, skeletal, or both. Furthermore, clarity of mandibular reference points is compromised by the use of PA radiographs. In Table I, one third of the sample of crossbite subjects demonstrate a switch in side of mandibular positional deviation relative to the mandibular midline
16 Langberg, Arai, and Miner
deviation, and an almost equal number show a switch in side relative to the dentoalveolar crossbite side when PA radiographs are used. Furthermore, this method of investigation demonstrated mandibular asymmetry in approximately 50% of the noncrossbite control sample (Table II). The authors acknowledge the weaknesses inherent in the use of PA cephalometric radiographs4,5 but have excluded intraexaminer reliability measurements and stated intraclass correlation statistics. In addition, there is no mention of the standardization techniques used to reduce the margin of error associated with PA radiography. The authors have gone to considerable lengths to describe the novel assessment of dental asymmetry but have not provided much information about the triangulation method and which anatomic regions these various triangles represent. Also, little information is provided in this text about the positional deviation method. They discuss the use of univariate 2-sided Student t tests for analyzing the data. If these statistical assessments are to be used, possibly a Bonferroni adjustment should have been applied based on the set of a priori or planned comparisons designed for this study.6 With this approach, t statistics are computed for only these carefully chosen comparisons. The ␣ for the entire set of comparisons can be selected at .05 and is distributed equally across the entire set of a priori comparisons to arrive at the Bonferroni adjustment for these data. This controls the type I error probabilities in the entire set of planned comparisons so that the maximum probability of type I error is 0.05, according to Bonferroni inequality. The Bonferroni adjustment is more conservative than the independent t tests without the correction.6 The authors might also have considered the use of withingroup and between-group differences by using analysis of variance (ANOVA) statistics. The ANOVA might have been used to assess condylar position and to describe differences in skeletal pattern, making use of the triangulation method. In the discussion, the authors note, “We found that adults with PUXB malocclusions display more transverse dental-arch asymmetry in both arches.” Table III shows statistical differences only for the mandibular arch; it is not appropriate to infer differences based on trends in nonsignificant variables for maxillary dental variables, especially because only t tests were used. On the basis of a comparison of 15 adult crossbite subjects with 15 noncrossbite subjects, the authors have concluded, “Unilateral posterior crossbite develops as a result of a large mandible rather than a deficient maxilla, as commonly believed.” Possibly a larger
American Journal of Orthodontics and Dentofacial Orthopedics January 2005
sample size would have provided a more balanced perspective, as previously published data have shown.7,8 PA radiography and submental vertex imaging might not provide adequate information for determining skeletal asymmetry, especially when area triangulation is used on a 3-dimensional object, such as the skeleton of the face. Localized disturbances seem to lead to distant areas of compensations to ensure adequate form and function of the stomatognathic system. Possibly the truth will be discovered soon with evaluation and assessment of 3-dimensional images of the face. True volumetric evaluation of anatomic regions will provide greater insight into area remodeling. Anatomic planes can be used and converted into 3-dimensional vectors to assess the vector resolution of the developmental effect. Three-dimensional imaging might even be used to determine localized alveolar bone and dental compensations associated with uncorrected posterior crossbites and provide information necessary for treatment planning and treatment execution. Until we have caught up with our current imaging capabilities, many of our questions might remain unanswered or difficult to explain. Brian Nebbe Sherwood Park, Alberta, Canada REFERENCES 1. Lam PH, Sadowsky C, Omerza F. Mandibular asymmetry and condylar position in children with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1999;115:569-75. 2. O’Byrn BL, Sadowsky C, Schneider BJ, BeGole E. An evaluation of mandibular asymmetry in adults with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1995;107:394-400. 3. Cook J. Asymmetry of the craniofacial complex. Br J Orthod 1980;7:33-8. 4. Major PW, Johnson DE, Hesse KL, Glover KE. Landmark identification error in posterior anterior cephalometrics. Angle Orthod 1994; 64:447-54. 5. Major PW, Johnson DE, Hesse KL, Glover KE. Effect of head orientation on posterior anterior cephalometric landmark identification. Angle Orthod. 1996;66:51-60. 6. Marascuilo LA, Levin JR. Multivariate statistics in the social sciences: a researcher’s guide. Monterey, Calif: Brooks/Cole; 1983. 7. Allen D, Rebellato J, Sheats R, Ceron AM. Skeletal and dental contributions to posterior crossbites. Angle Orthod. 2003;73:515-24. 8. Thilander B, Lennartsson B. A study of children with unilateral posterior crossbite, treated and untreated, in the deciduous dentition— occlusal and skeletal characteristics of significance in predicting the long-term outcome. J Orofac Orthop. 2002;63:371-83. Am J Orthod Dentofacial Orthop 2005;127:15– 6 0889-5406/$30.00 Copyright © 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2004.08.001
American Journal of Orthodontics and Dentofacial Orthopedics Volume 127, Number 1
7. Ahlgren J, Posselt U. Need of functional analysis and selective grinding in orthodontics. A clinical and electromyographic study. Acta Odont Scand 1963;21:187-226. 8. Kürol J, Berglund L. Longitudinal study and cost-benefit analysis of the effect of early treatment of posterior crossbites in the primary dentition. Eur J Orthod 1992;14:173-9. 9. Thilander B, Wahlund S, Lennartsson B. The effect of early interceptive treatment in children with posterior crossbite. Eur J Orthod 1984;6:25-34. 10. Lam PH, Sadowsky C, Omerza F. Mandibular asymmetry and condylar position in children with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1999;115:569-75. 11. Pirttiniemi P, Kantomaa T, Lahtela P. Relationship between craniofacial and condyle path asymmetry in unilateral posterior crossbite patients. Eur J Orthod 1990;12:408-13. 12. Nerder PH, Bakke M, Solow B. The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study. Eur J Orthod 1999;21:155-66. 13. Schmid W, Mongini F, Felisio A. A computer-based assessment of structural and displacement asymmetries of the mandible. Am J Orthod Dentofacial Orthop 1991;100:19-34. 14. Mongini F, Schmid W. Treatment of mandibular asymmetries during growth—a longitudinal study. Eur J Orthod 1987;9:51-67. 15. Lindner A, Hendrickson C, Odenrick L, Modeer T. Maxillary expansion of unilateral cross-bite in preschool children. Scand J Dent Res 1986;94:411-8. 16. Purcell PD. Effectiveness of posterior crossbite correction during the mixed dentition. J Pedodont 1985;9:302-11. 17. Maurice TJ, Kula K. Dental arch asymmetry in the mixed dentition. Angle Orthod 1998;68:37-44. 18. O’Byrn BL, Sadowsky C, Schneider B, BeGole EA. An evaluation of mandibular asymmetry in adults with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1995;107:394-400. 19. Kantomaa T. The shape of the glenoid fossa affects the growth of the mandible. Eur J Orthod 1988;10:249-54. 20. Pirttiniemi P, Raustia A, Kantomaa T, Pyhtinen J. Relationship between craniofacial and condyle path asymmetry in unilateral cross-bite patients. Eur J Orthod 1991;13:441-5. 21. Cohlmia JT, Ghosh J, Sinha PK, Nanda RS, Currier GF. Tomographic assessment of temporomandibular joints in patients with malocclusion. Angle Orthod 1996;66:27-36. 22. Wood DP, Elliott RW. Reproducibility of the centric relation bite registration technique. Angle Orthod 1994;64:211-9. 23. Major PW, Johnson DE, Hesse KL, Glover KE. Landmark identification error in posterior anterior cephalometrics. Angle Orthod 1994;64:447-54. 24. Shah SM, Joshi MR. An assessment of asymmetry in the normal craniofacial complex. Angle Orthod 1978;48:141-8. 25. Vig PS, Hewitt AB. Asymmetry of the human facial skeleton. Angle Orthod 1975;45:125-9. 26. Svanholt P, Solow B. Assessment of midline discrepancies on the postero-anterior cephalometric radiograph. Trans Eur Orthod Soc 1977;1:261-8. 27. Crawford SD. Condylar axis position, as determined by the occlusion and measured by the CPI instrument, and signs and symptoms of the temporomandibular dysfunction. Angle Orthod 1999;69:103-16. 28. Langberg BJ. An assessment of dental and skeletal asymmetry and condylar position in adult patients with a posterior unilateral lingual crossbite [thesis]. Boston: Harvard School of Dental Medicine; 2002.
29. Alavi DG, BeGole EA, Schneider BJ. Facial and dental arch asymmetries in Class II subdivision malocclusion. Am J Orthod Dentofacial Orthop 1988;93:38-46. 30. Brin I, Ben-Bassat Y, Blustein Y, Ehrlich J, Hochman N, Marmary Y, et al. Skeletal and functional effects of treatment for unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1996;109:173-9. 31. Ben-Bassat Y, Yaffe A, Brin I, Freeman J, Ehrlich J. Functional and morphological-occlusal aspects in children treated for unilateral posterior cross-bite. Eur J Orthod 1993;15:57-63. 32. Williamson EH. The role of cranio-mandibular dysfunction in orthodontic diagnosis and treatment planning. Dent Clin North Am 1983;27:541-60. 33. Roth RH. Temporomandibular pain-dysfunction and occlusal relationships. Angle Orthod 1973;43:136-53. 34. Dawson PE. New definition for relating occlusion to varying conditions of the temporomandibular joint. J Prosthet Dent 1995;74:619-27. 35. Alexander SR, Moore RN, DuBois LM. Mandibular condyle position: comparison of articular mountings and magnetic resonance imaging. Am J Orthod Dentofacial Orthop 1993;104: 230-9. 36. Hinton RJ. Changes in articular eminence morphology with dental function. Am J Orthod 1981;54:439-55. 37. Hinton RJ, McNamara J. Temporal bone adaptations in response to protrusive function in juvenile and young adult rhesus monkeys. Eur J Orthod 1984;6:155-74. 38. Woodside DG, Metaxas A, Altunas G. The influence of functional appliance therapy on glenoid fossa remodeling. Am J Orthod Dentofacial Orthop 1987;92:181-98. 39. Troelstrup B, Møller E. Electromyography of the temporalis and masseter muscles in children with unilateral cross-bite. Scand J Dent Res 1970;78:425-30. 40. Ingerval B, Thilander B. Activity of temporal and masseter muscles in children with a lateral forced bite. Angle Orthod 1975;45:249-58.
COMMENTARY
This article reports that mandibular skeletal asymmetry is not evident in a group of adults with posterior unilateral crossbite when compared with an adult control group. Furthermore, the authors claim that posterior crossbite is due to increased width of the mandible and not a result of transverse deficiency of the maxilla. This study makes use of posteroanterior (PA) radiographs, in preference to previously used submental vertex radiographs, as used by Lam et al1 to assess facial asymmetry in adolescents and O’Byrn et al2 to evaluate skeletal asymmetry in adults. According to Cook,3 as little as 5° of side-to-side head rotation for a PA radiograph caused the side of the asymmetry to switch. In addition, PA radiographs could not be used to determine whether the source of the asymmetry was dentoalveolar, skeletal, or both. Furthermore, clarity of mandibular reference points is compromised by the use of PA radiographs. In Table I, one third of the sample of crossbite subjects demonstrate a switch in side of mandibular positional deviation relative to the mandibular midline
16 Langberg, Arai, and Miner
deviation, and an almost equal number show a switch in side relative to the dentoalveolar crossbite side when PA radiographs are used. Furthermore, this method of investigation demonstrated mandibular asymmetry in approximately 50% of the noncrossbite control sample (Table II). The authors acknowledge the weaknesses inherent in the use of PA cephalometric radiographs4,5 but have excluded intraexaminer reliability measurements and stated intraclass correlation statistics. In addition, there is no mention of the standardization techniques used to reduce the margin of error associated with PA radiography. The authors have gone to considerable lengths to describe the novel assessment of dental asymmetry but have not provided much information about the triangulation method and which anatomic regions these various triangles represent. Also, little information is provided in this text about the positional deviation method. They discuss the use of univariate 2-sided Student t tests for analyzing the data. If these statistical assessments are to be used, possibly a Bonferroni adjustment should have been applied based on the set of a priori or planned comparisons designed for this study.6 With this approach, t statistics are computed for only these carefully chosen comparisons. The ␣ for the entire set of comparisons can be selected at .05 and is distributed equally across the entire set of a priori comparisons to arrive at the Bonferroni adjustment for these data. This controls the type I error probabilities in the entire set of planned comparisons so that the maximum probability of type I error is 0.05, according to Bonferroni inequality. The Bonferroni adjustment is more conservative than the independent t tests without the correction.6 The authors might also have considered the use of withingroup and between-group differences by using analysis of variance (ANOVA) statistics. The ANOVA might have been used to assess condylar position and to describe differences in skeletal pattern, making use of the triangulation method. In the discussion, the authors note, “We found that adults with PUXB malocclusions display more transverse dental-arch asymmetry in both arches.” Table III shows statistical differences only for the mandibular arch; it is not appropriate to infer differences based on trends in nonsignificant variables for maxillary dental variables, especially because only t tests were used. On the basis of a comparison of 15 adult crossbite subjects with 15 noncrossbite subjects, the authors have concluded, “Unilateral posterior crossbite develops as a result of a large mandible rather than a deficient maxilla, as commonly believed.” Possibly a larger
American Journal of Orthodontics and Dentofacial Orthopedics January 2005
sample size would have provided a more balanced perspective, as previously published data have shown.7,8 PA radiography and submental vertex imaging might not provide adequate information for determining skeletal asymmetry, especially when area triangulation is used on a 3-dimensional object, such as the skeleton of the face. Localized disturbances seem to lead to distant areas of compensations to ensure adequate form and function of the stomatognathic system. Possibly the truth will be discovered soon with evaluation and assessment of 3-dimensional images of the face. True volumetric evaluation of anatomic regions will provide greater insight into area remodeling. Anatomic planes can be used and converted into 3-dimensional vectors to assess the vector resolution of the developmental effect. Three-dimensional imaging might even be used to determine localized alveolar bone and dental compensations associated with uncorrected posterior crossbites and provide information necessary for treatment planning and treatment execution. Until we have caught up with our current imaging capabilities, many of our questions might remain unanswered or difficult to explain. Brian Nebbe Sherwood Park, Alberta, Canada REFERENCES 1. Lam PH, Sadowsky C, Omerza F. Mandibular asymmetry and condylar position in children with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1999;115:569-75. 2. O’Byrn BL, Sadowsky C, Schneider BJ, BeGole E. An evaluation of mandibular asymmetry in adults with unilateral posterior crossbite. Am J Orthod Dentofacial Orthop 1995;107:394-400. 3. Cook J. Asymmetry of the craniofacial complex. Br J Orthod 1980;7:33-8. 4. Major PW, Johnson DE, Hesse KL, Glover KE. Landmark identification error in posterior anterior cephalometrics. Angle Orthod 1994; 64:447-54. 5. Major PW, Johnson DE, Hesse KL, Glover KE. Effect of head orientation on posterior anterior cephalometric landmark identification. Angle Orthod. 1996;66:51-60. 6. Marascuilo LA, Levin JR. Multivariate statistics in the social sciences: a researcher’s guide. Monterey, Calif: Brooks/Cole; 1983. 7. Allen D, Rebellato J, Sheats R, Ceron AM. Skeletal and dental contributions to posterior crossbites. Angle Orthod. 2003;73:515-24. 8. Thilander B, Lennartsson B. A study of children with unilateral posterior crossbite, treated and untreated, in the deciduous dentition— occlusal and skeletal characteristics of significance in predicting the long-term outcome. J Orofac Orthop. 2002;63:371-83. Am J Orthod Dentofacial Orthop 2005;127:15– 6 0889-5406/$30.00 Copyright © 2005 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2004.08.001