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Longitudinal changes in dental arches from mixed to permanent dentition in a Turkish population
ORIGINAL ARTICLE
Longitudinal changes in dental arches from mixed to permanent dentition in a Turkish population Seher Gündüz Arslan,a Jalan Deveciog˘lu Kama,b Semra S¸ahin,c and Orhan Hamamcid Diyarbakir and Bursa, Turkey Introduction: Orthodontists can benefit from understanding occlusal changes during every stage of human development. The growth and development period is influenced by environmental factors, nutrition, and ethnic variations; systemic health and individual variations can also occur. Our aim in this study was to investigate the longitudinal changes in dental arch dimensions during the transition from mixed dentition (T1) to permanent dentition (T2) in children living in Turkey. Methods: Sixty-five patients (36 girls, 29 boys) with complete records from the mixed dentition to the early permanent dentition stages were included in this study (total, 130 dental casts). All casts (T1 and T2) had been prepared in centric relation by wax bites, and 14 parameters were measured on these casts. Results: The initial parameters in this Turkish population showed sexual dimorphism; however, during the observation period (T2-T1), there was no sexual dimorphism in arch dimension changes. There were significant changes in arch width parameters (especially in girls), overjet, and overbite in Turkish children between the midmixed and the permanent dentitions. Conclusions: These results should be useful in planning orthodontic treatment for patients in the mixed and early permanent dentition. (Am J Orthod Dentofacial Orthop 2007;132:576.e15-576.e21)
O
rthodontists can benefit from understanding occlusal changes during every stage of human development. Graber1 stated that a balanced, healthy, stable occlusion could be considered normal, even with small tooth rotations and small tooth sizearch length discrepancies. However, when orthodontists observe dental crowding, increased overjet, open bite, and other undesirable characteristics in a patient at the posttreatment stage, they tend to search for causes of failure. Questions can arise as to whether the final excellent occlusion will be stable, and whether the physiology of the masticatory system will lead to occlusal modifications, changing the pattern established by orthodontic treatment. In persons with normal occlusion who have not previously undergone orthodontic treatment, an initial evaluation of adaptive longitudinal changes in the occlusion should be performed. These
a
Assistant professor, Department of Orthodontics, Dental Faculty, Dicle University, Diyarbakır, Turkey. Professor, Department of Orthodontics, Dental Faculty, Dicle University, Diyarbakır, Turkey. c Assistant professor, Oral Health Centre, Bursa, Turkey. d Professor and chair, Department of Orthodontics, Dental Faculty, Dicle University, Diyarbakır, Turkey. Reprint requests to: Seher Gündüz Arslan, Dicle University, Orthodontics, Dental Faculty, Diyarbakır, Turkey 21280; e-mail, [email protected]. Submitted, March 2007; revised and accepted, June 2007. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2007.06.009 b
changes become especially important in growing patients. Based on these initial observations, changes that might occur in the posttreatment period could be determined.2 This article focuses on several important factors related to arch width, including the effect of extraction vs nonextraction3-7 and the general effect of orthodontic treatment and normal growth on arch width.7 Arch dimensions change with growth8; therefore, it is necessary to distinguish changes induced by appliance therapy from those that occur as a result of natural growth. Naturally occurring changes in untreated persons should be used as the gold standard for evaluating dental arch changes produced by orthodontic treatment.9 Many studies have investigated arch dimensional changes in various stages of the growth and development period: arch widths,3,10-13 arch dimensions,2,9,14-21 overjet and overbite,13,17,20,22 and dental crowding.17,23 Yet, few studies including all those parameters evaluated the transition from the mixed to the permanent dentition.17,20 It has been reported that the growth and development period is influenced by environmental factors, nutrition, and ethnic variations; systemic,24,25 health, and individual variations can also occur.26,27 Our aim in this study was to investigate the longitudinal changes in dental arch dimensions during the transition from the mixed to the permanent dentition in children living in Turkey. 576.e15
576.e16 Arslan et al
Table I.
American Journal of Orthodontics and Dentofacial Orthopedics November 2007
Chronologic and skeletal ages (in years) at T1
Chronologic age, girls Skeletal age, girls Chronologic age, boys Skeletal age, boys
n
Mean
SD
36 36 29 29
9.64 8.98 9.44 9.00
1.51 1.48 1.34 1.70
MATERIAL AND METHODS
The subjects in this study were selected from the archives of the Department of Orthodontics, Faculty of Dentistry, Dicle University, Diyarbakir, Turkey. Sixtyfive patients (36 girls, 29 boys) with complete records from the mixed dentition to the early permanent dentition stages were included. These subjects were judged to have clinically good occlusion and therefore represented orthodontic normals rather than orthodontic ideals. Sample selection was initially based on good-quality longitudinal records, no malformed or congenitally absent teeth, and all points to be measured clearly identifiable. The casts, made in our clinic for a previous study, represented 2 time points. At the mixed-dentition stage (T1), the mandibular and maxillary permanent incisors and first molars and the second deciduous molars were present. In addition, either the deciduous canines or the deciduous first molars were in place. The chronologic and skeletal ages of subjects at T1 are shown in Table I. At the permanent-dentition stage (T2), a second cast was made 5 years after the first. At this stage, the permanent dentition was complete (except for the third molars), with all teeth in the mouth and their marginal ridges and entire occlusal surfaces visible. A total of 130 dental casts were used in this study at the 2 stages. All casts had been prepared in centric relation by wax bites. Cast measurements were made by the same trained operator (S.G.A.) using a digital caliper (150 mm HS/R3/lA; Knuth Werkzeugmaschinen KG, Wassbek, Germany) with an accuracy of ⫾ 0.01 mm. The caliper was modified to have narrower and more accurate ends that could touch precisely the proximal contact points.26,27 Each cast was measured on 3 occasions, and the mean values were recorded. These casts were evaluated in 3 groups: boys, girls, and total group. The following parameters were measured on these casts: (1) maxillary arch perimeter, the sum of 5 maxillary segments between the mesial aspects of the molars (Fig 1); (2) mandibular arch perimeter, the sum of 5 mandibular segments between the mesial aspects of the molars (Fig 1); (3) maxillary arch depth, the perpendicular distance from the labial
surfaces of the central incisors to the line between the central fossae of the maxillary first molars (Fig 1); (4) mandibular arch depth, like maxillary arch length, but for the mandibular first molars (Fig 1); (5) maxillary molar width, the distance between the first molars’ central points, marked in the line of the mesiobuccal groove (Fig 2); (6) mandibular molar width, the distance between the most lingual points of the first molars (Fig 2); (7) maxillary premolar width, the distance between the centers of the first premolar fossae (Fig 2); (8) mandibular premolar width, the distance between the most lingual points of the first premolars (Fig 2); (9) maxillary canine width, the distance between the cusps of the canines (Fig 2); (10) mandibular canine width, the distance between the most lingual points of the canines (Fig 2); (11) overbite, the mean overlap of maxillary to mandibular central incisors; (12) overjet, the distance parallel to the occlusal plane from the incisal edges of the most labial maxillary to the most labial mandibular central incisor; (13) maxillary incisor irregularity, irregularity of the maxillary incisors as adapted from Little28; and (14) mandibular incisor irregularity, as suggested by Little,28 the summed displacement of the anatomic contact points of the mandibular anterior teeth (Fig 3). Statistical analysis
To determine the method error, measurements on 15 casts were repeated at 3-week intervals, and Dahlberg’s formula29 was used to assess differences among the measurements. The paired samples t test was used to verify the significance of the values in each group separately, over the 2 time periods (P ⬍.05). An independent samples t test was used to evaluate the difference in the change from T1 to T2 between the sexes. RESULTS
The method error was less than 0.4 mm. When the sexes were compared at T1, sexual dimorphism was found in some parameters (Table II). However, when the changes in the cast measurements (T2-T1) were compared (Table III), no sexual dimorphism was found except in overjet. Descriptive statistics and paired t test results of the measurements from the total group at T1 and T2, and the changes between T2 and T1 are given in Table IV. Table III shows the results of the paired-samples t test of changes in male and female parameters during the transition from mixed to permanent dentition and the comparisons of these changes between the sexes (independent-samples t test results).
American Journal of Orthodontics and Dentofacial Orthopedics Volume 132, Number 5
Arslan et al 576.e17
Fig 1. Arch perimeter and arch depth measurements in the maxilla and the mandible. U, Upper arch; L, lower arch; AP, arch perimeter; AD, arch depth.
Fig 2. Intercanine, interpremolar, and intermolar widths measured on dental casts. U, Upper arch; L, lower arch; C-C, intercanine width; PM-PM, interpremolar width; M-M, intermolar width.
There were no statistically significant differences in arch perimeter and arch depth during the transition from mixed to permanent dentition in all groups. The paired-samples t test in the total group showed significant increases in both maxillary (P ⬍.001) and mandibular (P ⬍.001) intermolar widths (Table IV). Statistically significant increases were found between T2 and T1 in maxillary (P ⬍.001) and mandibular (P ⬍.01) intermolar widths in the girls (Table IV), and a significant increase in maxillary intermolar width (P ⬍.05) ws found in the boys.
In the total group; there were significant increases in maxillary (P ⬍.01) and mandibular (P ⬍.001) interpremolar widths (Table IV). There were significant increases in interpremolar widths for both the maxilla (P ⬍.01) and the mandible (P ⬍.01) in the girls (Table III). In the boys, a significant increase was found in mandibular interpremolar width (P ⬍.05). In the total group, intercanine widths showed a significant increase in the maxilla (P ⬍.05) (Table IV). In the girls, intercanine widths had no statistically significant differences. In the boys, the
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American Journal of Orthodontics and Dentofacial Orthopedics November 2007
Fig 3. Little’s index of irregularity is the sum of the contact point displacements from anatomic contact point to contact point (A ⫹ B ⫹ C ⫹ D ⫹ E). Table II. Descriptive statistics by sex and comparison of arch parameters between the sexes at T1 (independent samples t test results) Boys T1
Girls T1
Measurement (mm)
Mean
SD
Mean
SD
P
Maxillary arch perimeter Mandibular arch perimeter Maxillary arch depth Mandibular arch depth Maxillary molar width Mandibular molar width Maxillary premolar width Mandibular premolar width Maxillary canine width Mandibular canine width Overbite Overjet Maxillary incisor irregularity Mandibular incisor irregularity
79.64 70.00 28.16 24.51 45.84 34.55 35.55 26.18 31.97 21.08 2.35 2.11 0.97 1.39
6.12 6.50 3.51 3.07 2.66 2.71 2.02 2.55 3.47 1.85 0.42 0.33 0.26 0.87
75.39 67.09 26.88 22.90 44.15 32.12 34.43 25.22 31.29 20.01 2.36 2.14 1.98 1.50
4.87 5.62 2.29 3.02 2.04 2.66 1.51 2.42 3.31 1.84 0.37 0.18 0.30 0.92
‡
NS NS * † ‡
* NS NS NS NS NS * NS
*P ⬍.05; †P ⬍.01; ‡P ⬍.001; NS, not significant.
maxillary increase was statistically significant (P ⬍.05) (Table III). Overjet and overbite showed significant increases in all groups (P ⬍.001). The decrease of the irregularity index was statistically insignificant in all groups. DISCUSSION
Several studies9,14,21,30 investigated the changes in the dental arches during the periods of growth and adulthood, providing strong evidence of individualized mechanisms that influence the form of the dental arch. Our findings suggest a highly complex, variable, and often unquantifiable interrelationship of factors involved in the maturation of the normal dentition. The midmixed dentition stage of development was chosen because it corresponds to the time when early orthodontic therapy might be started in patients with severe malocclusion. The permanent dentition stage
was chosen because it corresponds to the time when full conventional orthodontic therapy might begin. We found insignificant decreases in arch length between T1 and T2. Maxillary arch length increases until age 13, and mandibular arch length increases until age 8; then arch perimeters are reported to begin decreasing.2 Bishara et al21 reported that the maxillary perimeter decreases insignificantly in both sexes, and the mandibular perimeter decreases by 2.4 mm in boys and 3.2 mm in girls between the ages of 8 and 13. Sillman18 reported arch perimeter decreases of 1.5 mm in the maxilla and 2 mm in the mandible between the ages of 3 and 19. Moorrees17 reported that the arch perimeters of both sexes decreased between the ages of 9 and 14 because of changes in the dentition; this decrease was more significant in girls, and arch length remained constant after the age of 14. Several studies agree with these findings.14,16,17 The main causes of these length changes are the closure of posterior interproximal spaces by the replacement of the deciduous dentition with the permanent dentition, lingual tipping of the anterior teeth (especially maxillary incisors), and the interproximal contacts made by the permanent teeth.16 The arch length decreases in the maxilla and mandible were acceptable in that age group because of the mesial shifting of the permanent first molars. Nevertheless, the decreases we found were smaller than those of previous studies. There was an insignificant decrease in arch depths. This decrease might be related to the mesial shifting of the first molars to leeway spaces. A study of children between the ages of 8 and 14 showed an increase in the molar region transversally, but this increase did not affect the arch dimension.15 In a study of twins, arch depth decreases of 1.3 mm in the maxilla and 1.6 mm in the mandible were reported.19 In our study, the decreases in arch depths were smaller than in the other studies and can be related to individual variations. In several previous studies, the maxillary or mandibular (or both) widths were larger in the male subjects than in the female subjects.30-32 Similarly, in this study, the widths and other parameters were greater in the boys than in the girls (Table II). In our study, arch width changes varied between boys and girls living in the southeastern Anatolia region of Turkey. In girls, there were increases of 1.36 mm in maxillary intermolar width and 1.64 mm in mandibular intermolar width. In boys, the respective values were 1.58 and 0.91 mm. Considering these findings, it can be concluded that the time period studied here represents when most of the transverse growth of the molar region
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American Journal of Orthodontics and Dentofacial Orthopedics Volume 132, Number 5
Table III.
Paired samples t test results of changes in parameters during the transition from mixed to permanent dentition and comparisons of these changes between sexes (independent samples t test results) Boys T2 -T1 Measurement (mm) Maxillary arch perimeter Mandibular arch perimeter Maxillary arch depth Mandibular arch depth Maxillary molar width Mandibular molar width Maxillary premolar width Mandibular premolar width Maxillary canine width Mandibular canine width Overbite Overjet Maxillary incisor irregularity Mandibular incisor irregularity
Comparison (T2-T1)
Girls T2 -T1
Mean differences
SD
P
⫺2.30 ⫺1.88 ⫺0.35 ⫺0.75 1.58 0.91 0.70 1.37 1.59 ⫺0.59 0.44 0.17 ⫺0.41 ⫺0.20
1.31 1.71 0.83 0.59 0.65 0.53 0.48 0.59 0.62 0.40 0.02 0.02 0.23 0.78
NS NS NS NS * NS NS * * NS ‡ ‡
NS NS
Mean differences
SD
P
P
⫺0.35 ⫺0.48 ⫺0.48 ⫺0.28 1.36 1.64 1.49 1.88 0.39 ⫺0.11 0.38 0.28 ⫺0.56 ⫺0.40
0.71 0.93 0.54 0.53 0.31 0.51 0.54 0.44 0.59 0.27 0.02 0.02 0.15 0.20
NS NS NS NS
NS NS NS NS NS NS NS NS NS NS NS * NS NS
‡ † † ‡
NS NS ‡ ‡
NS NS
*P ⬍.05; †P ⬍.01; ‡P ⬍.001; NS, not significant. Table IV.
Descriptive statistic and paired t test results of the measurements from casts of the total group in mixed (T1) and permanent (T2) dentition and the change between T2 and T1 T1
T2
Change (T2-T1)
Measurement (mm)
Mean
SD
Mean
SD
Mean differences
SD
P
Maxillary arch perimeter Mandibular arch perimeter Maxillary arch depth Mandibular arch depth Maxillary molar width Mandibular molar width Maxillary premolar width Mandibular premolar width Maxillary canine width Mandibular canine width Overbite Overjet Maxillary incisor irregularity Mandibular incisor irregularity
77.09 68.12 27.45 23.62 44.91 33.21 34.93 25.65 31.59 20.48 1.35 2.12 1.01 1.31
6.21 7.31 2.94 3.13 2.47 2.92 1.83 2.50 3.37 1.91 0.39 0.31 0.28 0.78
76.26 67.54 27.02 23.12 46.37 34.52 36.08 27.30 32.52 20.15 1.77 2.36 0.89 1.11
5.26 6.60 3.00 2.41 3.05 2.97 3.13 2.95 3.82 1.92 0.51 0.36 0.38 0.86
⫺0.83 ⫺0.57 ⫺0.42 ⫺0.49 1.46 1.31 1.14 1.65 0.92 ⫺0.33 0.41 0.23 ⫺0.12 ⫺0.19
5.83 7.46 3.83 3.17 2.71 3.02 3.01 2.91 3.50 1.90 0.38 0.17 0.26 0.69
NS NS NS NS ‡ ‡ † ‡
* NS ‡ ‡
NS NS
*P ⬍.05; †P ⬍.01; ‡P ⬍.001; NS, not significant.
occurs in girls and most of the transverse growth of the maxillary molar region occurs in boys. In the boys, the transverse growth of the mandibular molar region must have occurred before the start of this study. In the boys, the higher values at T1 proved this. In a study conducted in the United Kingdom, decreases were found in intermolar and intercanine widths between the ages of 11 and 14, but those parameters increased between the ages of 24 and 30.10 Moorrees17 found that the mandibular intermolar width increased between the ages of 9 and 14 and remained
constant after the age of 14; our results are consistent with his. There were statistically significant increases in maxillary and mandibular interpremolar widths in the girls and the total group. There was a significant increase only in mandibular interpremolar width in the boys.The increases in interpremolar widths were 1.49 mm in the maxilla and 1.88 mm in the mandible for girls, and 1.37 mm in the mandible for boys. These changes in arch widths are related to the growth and development period and the vestibular
576.e20 Arslan et al
eruption of the permanent teeth. The forward growth of the anterior region of the maxilla during the replacement of the dentition was insignificant, but the lateral growth of the arch to adapt to the permanent dentition was significant. These also affect width increases transversally.33 The reason for the transverse width increases in the maxillary deciduous second molar and the permanent first molar areas is the oblique buccal loading of the alveolar process.34 The maxillary intermolar width increase was insignificant in boys; this might be because their growth and development period ended before the starting time (mixed dentition) of this study. In the study of Lundström19 on twins between the ages of 9 and 19, there were minimal increases in permanent intermolar and interpremolar widths. The Michigan Growth Study11-13 showed premolar width increases in both jaws, with a greater increase in the maxilla than in the mandible. However, in our study, we observed that the increase in interpremolar width was greater in the mandible than in the maxilla. This finding might indicate that growth of maxillary interpremolar width ended before the start of this study. The significant increases in intercanine width were in the maxillary area in boys (1.59 mm) and in the total group (0.92 mm). The main change in mandibular intercanine width was an insignificant decrease in all groups. The intercanine width changes in girls were insignificant, and this finding might indicate that the increase of this parameter by the growth and development period ended before the start (mixed dentition) of this study. Intercanine widths were studied by Barrow and White,16 Moorrees,17 and Sillman,18 who all observed a rapid increase between the ages of 6 and 9 associated with the eruption of the permanent canines and incisors. According to Moorrees,17 a decrease occurs between the ages of 10 and 12, with no change after that. However, other authors16-18 suggested that intercanine width continues to decrease after age 12. In a longitudinal study by Knott,35 there was an average change in intercanine width during the transition from the deciduous to the permanent dentition, but there were highly individual variations during the transition from the mixed to the permanent dentition. In our study, there were insignificant decreases in mandibular intercanine widths in both sexes between the ages of 9 and 14. These differences could be related to genetic or ethnic variations. Sinclair and Little20 found a decrease in mandibular intercanine width between the mixed and early permanent dentitions, consistent with our study.
American Journal of Orthodontics and Dentofacial Orthopedics November 2007
Overjet and overbite exhibited increases in all groups. Overbite increased 0.41 mm overall. Overjet increased 0.23 mm overall. The increase in overbite is probably related to the use of leeway spaces and the mesial shifting of the permanent first molars. The increase in overjet indicates that the translation of the mandible had not yet occurred. Several longitudinal studies reported significant increases in overjet and overbite during the replacement of the dentition.13,17,20,22 Our findings are consistent with those reports. In this study, the irregularity index decreases were statistically insignificant in all groups. In a crosssectional study, Foster et al23 found differences in the pattern of dental arch crowding among 4 age groups; the incidence of mandibular crowding increased to 90% by age 14 and decreased somewhat by age 25. Moorrees17 observed a different pattern. He suggested that there was considerable crowding in the 8-to-10 year age period, corresponding to the eruption of the permanent canines, but that this decreased between the ages of 12 and 14 and then increased again from 14 to 18 years of age. Our finding might be related either to canine and incisor distalization to leeway space or to facial growth. In untreated subjects, attempts to correlate incisor crowding with other dental and skeletal features have been limited because of the difficulties in quantifying incisor crowding and the apparent multifactorial etiology of malalignment. Nevertheless, growth has been implicated by some authors as a primary factor, with Bjork and Skieller36 suggesting that incisor position might be correlated with the amount and direction of facial growth. CONCLUSIONS
After examining diagnostic dental casts taken during the mixed dentition stage and after reaching the permanent dentition stage in 65 untreated subjects, we reached the following conclusions. 1. Our results with Turkish children were compatible with those of studies in other countries. 2. The initial parameters in this Turkish population showed sexual dimorphism; however, during the observation period (T2-T1), there was no sexual dimorphism in arch dimension changes. 3. There were significant changes in arch width parameters (especially in girls), overjet, and overbite in Turkish children between the midmixed and the permanent dentitions. These results should be useful in planning orthodontic treatment for patients in the mixed and early permanent dentitions.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 132, Number 5
REFERENCES 1. Graber TM. Normal occlusion. Dent Clin North Am 1968;273-90. 2. Bishara SE, Jakobsen JR, Treder J, Nowak A. Arch width changes from 6 weeks to 45 years of age. Am J Orthod Dentofacial Orthop 1997;111:401-9. 3. Bishara SE, Bayati P, Zaher AR, Jakobsen JR. Comparisons of the dental arch changes in patients with Class II, division 1 malocclusions: extraction vs nonextraction treatments. Angle Orthod 1994;64:351-8. 4. Bishara SE, Cummins DM, Zaher AR. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop 1997;111:18-27. 5. Burke SP, Silveira AM, Goldsmith LJ, Yancey JM, Van Stewart A, Scarfe WC. A meta-analysis of mandibular intercanine width in treatment and postretention. Angle Orthod 1998;68:53-60. 6. Gianelly AA. Arch width after extraction and nonextraction. Am J Orthod Dentofacial Orthop 2003;123:25-8. 7. Shearn BN, Woods MG. An occlusal and cephalometric analysis of lower first and second premolar extraction effects. Am J Orthod Dentofacial Orthop 2000;117:351-61. 8. De La Cruz A, Sampson P, Little RM, Årtun J, Shapiro PA. Long-term changes in arch form after orthodontic treatment and retention. Am J Orthod Dentofacial Orthop 1995;107:518-30. 9. Carter GA, McNamara JA Jr. Longitudinal dental arch changes in adults. Am J Orthod Dentofacial Orthop 1998;114:88-99. 10. Ward ED, Workman J, Brown R, Richmond S. Changes in arch width. A 20-year longitudinal study of orthodontic treatment. Angle Orthod 2006;76:6-13. 11. Moyers RE, van der Linden FPGM, Riolo ML, McNamara JA Jr. Standards of human occlusal development. Monograph 5. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1976. 12. Van der Linden FPGM. Development of the dentition. Chicago: Quintessence; 1983. 13. Van der Linden FPGM. Facial growth and facial orthopedics. Chicago: Quintessence; 1989. p. 148-52. 14. Brown VP, Daugaard-Jensen I. Changes in the dentition from the early teens to the early twenties: a longitudinal cast study. Acta Odontol Scand 1951;9:177-92. 15. Aprile EC. Sobre histopatologia de la gingivitis (thesis). Buenos Aires: Universidad Nacional de Buenos Aires; 1945. 16. Barrow CG, White JR. Developmental changes of the maxillary and mandibular dental arches. Angle Orthod 1952;22:41-6.
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17. Moorrees CFA. The dentition of the growing child. Cambridge, Mass: Harvard University Press; 1959. 18. Sillman JH. Dimensional changes of the dental arches: longitudinal study from birth to 25 years. Am J Orthod 1964;50:824-42. 19. Lundström A. Changes in crowding and spacing of the teeth with age. Dent Pract Dent Rec 1969;19:218-24. 20. Sinclair PM, Little RM. Maturation of untreated normal occlusions. Am J Orthod 1983;83:114-23. 21. Bishara SE, Jakobsen JR, Treder JE, Stasi MJ. Changes in the maxillary and mandibular tooth-size arch length relationship from early adolescence to early adulthood. A longitudinal study. Am J Orthod Dentofacial Orthop 1989;95:46-59. 22. Bjork A. Variability and age changes in overjet and overbite. Am J Orthod 1953;39:774-801. 23. Foster TD, Hamilton MC, Lavelle CL. A study of dental arch crowding in four age groups. Dent Pract Dent Rec 1970;21:9-12. 24. Krogman WM. The meaningful interpretation of growth and growth data by the clinician. Am J Orthod 1958;44:411-32. 25. Demirjian A, Buschang PH, Tanguay R, Patterson K. Interrelationships among measures of somatic, skeletal, dental, and sexual maturity. Am J Orthod 1985;88:433-8. 26. Ursus RS, Wiltshire WA. Orthodontic probability tables for black patients of African descent: mixed dentition analysis. Am J Orthod Dentofacial Orthop 1997;112:545-51. 27. Bailit HL. Dental variation among populations—an anthropologic view. Dent Clin North Am 1975;29:125-39. 28. Little R. The irregularity index: a quantitative score of mandibular anterior alignment. Am J Orthod 1975;68:554-63. 29. Dahlberg G. Statistical methods for medical and biological students. New York: Interscience Publications; 1940. 30. Cassidy KM, Harris EF, Tolley EA, Keim RG. Genetic influence on dental arch form in orthodontic patients. Angle Orthod 1998;68:445-54. 31. Staley RN, Stuntz WR, Peterson LC. Comparison of arch widths in adults with normal occlusions and adults with Class II, division 1 malocclusion. Am J Orthod 1985;88:163-9. 32. Raberin M, Laumon B, Martin JL, Brunner F. Dimensions and form of dental arches in subjects with normal occlusion. Am J Orthod Dentofacial Orthop 1993;104:67-72. 33. Friel S. Occlusion: observations on its development from infancy to old ageInt J Orthod 1927;13:322-43. 34. Brash JC. Growth of alveolar bone. Int J Orthod 1928;14.291-2. 35. Knott VB. Longitudinal study of dental arch width at four stages of dentition. Angle Orthod 1972;42:387-95. 36. Bjork A, Skieller V. Facial development and tooth eruption. An implant study at the age of puberty. Am J Orthod 1972;62:339-83.
Longitudinal changes in dental arches from mixed to permanent dentition in a Turkish population Seher Gündüz Arslan,a Jalan Deveciog˘lu Kama,b Semra S¸ahin,c and Orhan Hamamcid Diyarbakir and Bursa, Turkey Introduction: Orthodontists can benefit from understanding occlusal changes during every stage of human development. The growth and development period is influenced by environmental factors, nutrition, and ethnic variations; systemic health and individual variations can also occur. Our aim in this study was to investigate the longitudinal changes in dental arch dimensions during the transition from mixed dentition (T1) to permanent dentition (T2) in children living in Turkey. Methods: Sixty-five patients (36 girls, 29 boys) with complete records from the mixed dentition to the early permanent dentition stages were included in this study (total, 130 dental casts). All casts (T1 and T2) had been prepared in centric relation by wax bites, and 14 parameters were measured on these casts. Results: The initial parameters in this Turkish population showed sexual dimorphism; however, during the observation period (T2-T1), there was no sexual dimorphism in arch dimension changes. There were significant changes in arch width parameters (especially in girls), overjet, and overbite in Turkish children between the midmixed and the permanent dentitions. Conclusions: These results should be useful in planning orthodontic treatment for patients in the mixed and early permanent dentition. (Am J Orthod Dentofacial Orthop 2007;132:576.e15-576.e21)
O
rthodontists can benefit from understanding occlusal changes during every stage of human development. Graber1 stated that a balanced, healthy, stable occlusion could be considered normal, even with small tooth rotations and small tooth sizearch length discrepancies. However, when orthodontists observe dental crowding, increased overjet, open bite, and other undesirable characteristics in a patient at the posttreatment stage, they tend to search for causes of failure. Questions can arise as to whether the final excellent occlusion will be stable, and whether the physiology of the masticatory system will lead to occlusal modifications, changing the pattern established by orthodontic treatment. In persons with normal occlusion who have not previously undergone orthodontic treatment, an initial evaluation of adaptive longitudinal changes in the occlusion should be performed. These
a
Assistant professor, Department of Orthodontics, Dental Faculty, Dicle University, Diyarbakır, Turkey. Professor, Department of Orthodontics, Dental Faculty, Dicle University, Diyarbakır, Turkey. c Assistant professor, Oral Health Centre, Bursa, Turkey. d Professor and chair, Department of Orthodontics, Dental Faculty, Dicle University, Diyarbakır, Turkey. Reprint requests to: Seher Gündüz Arslan, Dicle University, Orthodontics, Dental Faculty, Diyarbakır, Turkey 21280; e-mail, [email protected]. Submitted, March 2007; revised and accepted, June 2007. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2007.06.009 b
changes become especially important in growing patients. Based on these initial observations, changes that might occur in the posttreatment period could be determined.2 This article focuses on several important factors related to arch width, including the effect of extraction vs nonextraction3-7 and the general effect of orthodontic treatment and normal growth on arch width.7 Arch dimensions change with growth8; therefore, it is necessary to distinguish changes induced by appliance therapy from those that occur as a result of natural growth. Naturally occurring changes in untreated persons should be used as the gold standard for evaluating dental arch changes produced by orthodontic treatment.9 Many studies have investigated arch dimensional changes in various stages of the growth and development period: arch widths,3,10-13 arch dimensions,2,9,14-21 overjet and overbite,13,17,20,22 and dental crowding.17,23 Yet, few studies including all those parameters evaluated the transition from the mixed to the permanent dentition.17,20 It has been reported that the growth and development period is influenced by environmental factors, nutrition, and ethnic variations; systemic,24,25 health, and individual variations can also occur.26,27 Our aim in this study was to investigate the longitudinal changes in dental arch dimensions during the transition from the mixed to the permanent dentition in children living in Turkey. 576.e15
576.e16 Arslan et al
Table I.
American Journal of Orthodontics and Dentofacial Orthopedics November 2007
Chronologic and skeletal ages (in years) at T1
Chronologic age, girls Skeletal age, girls Chronologic age, boys Skeletal age, boys
n
Mean
SD
36 36 29 29
9.64 8.98 9.44 9.00
1.51 1.48 1.34 1.70
MATERIAL AND METHODS
The subjects in this study were selected from the archives of the Department of Orthodontics, Faculty of Dentistry, Dicle University, Diyarbakir, Turkey. Sixtyfive patients (36 girls, 29 boys) with complete records from the mixed dentition to the early permanent dentition stages were included. These subjects were judged to have clinically good occlusion and therefore represented orthodontic normals rather than orthodontic ideals. Sample selection was initially based on good-quality longitudinal records, no malformed or congenitally absent teeth, and all points to be measured clearly identifiable. The casts, made in our clinic for a previous study, represented 2 time points. At the mixed-dentition stage (T1), the mandibular and maxillary permanent incisors and first molars and the second deciduous molars were present. In addition, either the deciduous canines or the deciduous first molars were in place. The chronologic and skeletal ages of subjects at T1 are shown in Table I. At the permanent-dentition stage (T2), a second cast was made 5 years after the first. At this stage, the permanent dentition was complete (except for the third molars), with all teeth in the mouth and their marginal ridges and entire occlusal surfaces visible. A total of 130 dental casts were used in this study at the 2 stages. All casts had been prepared in centric relation by wax bites. Cast measurements were made by the same trained operator (S.G.A.) using a digital caliper (150 mm HS/R3/lA; Knuth Werkzeugmaschinen KG, Wassbek, Germany) with an accuracy of ⫾ 0.01 mm. The caliper was modified to have narrower and more accurate ends that could touch precisely the proximal contact points.26,27 Each cast was measured on 3 occasions, and the mean values were recorded. These casts were evaluated in 3 groups: boys, girls, and total group. The following parameters were measured on these casts: (1) maxillary arch perimeter, the sum of 5 maxillary segments between the mesial aspects of the molars (Fig 1); (2) mandibular arch perimeter, the sum of 5 mandibular segments between the mesial aspects of the molars (Fig 1); (3) maxillary arch depth, the perpendicular distance from the labial
surfaces of the central incisors to the line between the central fossae of the maxillary first molars (Fig 1); (4) mandibular arch depth, like maxillary arch length, but for the mandibular first molars (Fig 1); (5) maxillary molar width, the distance between the first molars’ central points, marked in the line of the mesiobuccal groove (Fig 2); (6) mandibular molar width, the distance between the most lingual points of the first molars (Fig 2); (7) maxillary premolar width, the distance between the centers of the first premolar fossae (Fig 2); (8) mandibular premolar width, the distance between the most lingual points of the first premolars (Fig 2); (9) maxillary canine width, the distance between the cusps of the canines (Fig 2); (10) mandibular canine width, the distance between the most lingual points of the canines (Fig 2); (11) overbite, the mean overlap of maxillary to mandibular central incisors; (12) overjet, the distance parallel to the occlusal plane from the incisal edges of the most labial maxillary to the most labial mandibular central incisor; (13) maxillary incisor irregularity, irregularity of the maxillary incisors as adapted from Little28; and (14) mandibular incisor irregularity, as suggested by Little,28 the summed displacement of the anatomic contact points of the mandibular anterior teeth (Fig 3). Statistical analysis
To determine the method error, measurements on 15 casts were repeated at 3-week intervals, and Dahlberg’s formula29 was used to assess differences among the measurements. The paired samples t test was used to verify the significance of the values in each group separately, over the 2 time periods (P ⬍.05). An independent samples t test was used to evaluate the difference in the change from T1 to T2 between the sexes. RESULTS
The method error was less than 0.4 mm. When the sexes were compared at T1, sexual dimorphism was found in some parameters (Table II). However, when the changes in the cast measurements (T2-T1) were compared (Table III), no sexual dimorphism was found except in overjet. Descriptive statistics and paired t test results of the measurements from the total group at T1 and T2, and the changes between T2 and T1 are given in Table IV. Table III shows the results of the paired-samples t test of changes in male and female parameters during the transition from mixed to permanent dentition and the comparisons of these changes between the sexes (independent-samples t test results).
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Arslan et al 576.e17
Fig 1. Arch perimeter and arch depth measurements in the maxilla and the mandible. U, Upper arch; L, lower arch; AP, arch perimeter; AD, arch depth.
Fig 2. Intercanine, interpremolar, and intermolar widths measured on dental casts. U, Upper arch; L, lower arch; C-C, intercanine width; PM-PM, interpremolar width; M-M, intermolar width.
There were no statistically significant differences in arch perimeter and arch depth during the transition from mixed to permanent dentition in all groups. The paired-samples t test in the total group showed significant increases in both maxillary (P ⬍.001) and mandibular (P ⬍.001) intermolar widths (Table IV). Statistically significant increases were found between T2 and T1 in maxillary (P ⬍.001) and mandibular (P ⬍.01) intermolar widths in the girls (Table IV), and a significant increase in maxillary intermolar width (P ⬍.05) ws found in the boys.
In the total group; there were significant increases in maxillary (P ⬍.01) and mandibular (P ⬍.001) interpremolar widths (Table IV). There were significant increases in interpremolar widths for both the maxilla (P ⬍.01) and the mandible (P ⬍.01) in the girls (Table III). In the boys, a significant increase was found in mandibular interpremolar width (P ⬍.05). In the total group, intercanine widths showed a significant increase in the maxilla (P ⬍.05) (Table IV). In the girls, intercanine widths had no statistically significant differences. In the boys, the
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American Journal of Orthodontics and Dentofacial Orthopedics November 2007
Fig 3. Little’s index of irregularity is the sum of the contact point displacements from anatomic contact point to contact point (A ⫹ B ⫹ C ⫹ D ⫹ E). Table II. Descriptive statistics by sex and comparison of arch parameters between the sexes at T1 (independent samples t test results) Boys T1
Girls T1
Measurement (mm)
Mean
SD
Mean
SD
P
Maxillary arch perimeter Mandibular arch perimeter Maxillary arch depth Mandibular arch depth Maxillary molar width Mandibular molar width Maxillary premolar width Mandibular premolar width Maxillary canine width Mandibular canine width Overbite Overjet Maxillary incisor irregularity Mandibular incisor irregularity
79.64 70.00 28.16 24.51 45.84 34.55 35.55 26.18 31.97 21.08 2.35 2.11 0.97 1.39
6.12 6.50 3.51 3.07 2.66 2.71 2.02 2.55 3.47 1.85 0.42 0.33 0.26 0.87
75.39 67.09 26.88 22.90 44.15 32.12 34.43 25.22 31.29 20.01 2.36 2.14 1.98 1.50
4.87 5.62 2.29 3.02 2.04 2.66 1.51 2.42 3.31 1.84 0.37 0.18 0.30 0.92
‡
NS NS * † ‡
* NS NS NS NS NS * NS
*P ⬍.05; †P ⬍.01; ‡P ⬍.001; NS, not significant.
maxillary increase was statistically significant (P ⬍.05) (Table III). Overjet and overbite showed significant increases in all groups (P ⬍.001). The decrease of the irregularity index was statistically insignificant in all groups. DISCUSSION
Several studies9,14,21,30 investigated the changes in the dental arches during the periods of growth and adulthood, providing strong evidence of individualized mechanisms that influence the form of the dental arch. Our findings suggest a highly complex, variable, and often unquantifiable interrelationship of factors involved in the maturation of the normal dentition. The midmixed dentition stage of development was chosen because it corresponds to the time when early orthodontic therapy might be started in patients with severe malocclusion. The permanent dentition stage
was chosen because it corresponds to the time when full conventional orthodontic therapy might begin. We found insignificant decreases in arch length between T1 and T2. Maxillary arch length increases until age 13, and mandibular arch length increases until age 8; then arch perimeters are reported to begin decreasing.2 Bishara et al21 reported that the maxillary perimeter decreases insignificantly in both sexes, and the mandibular perimeter decreases by 2.4 mm in boys and 3.2 mm in girls between the ages of 8 and 13. Sillman18 reported arch perimeter decreases of 1.5 mm in the maxilla and 2 mm in the mandible between the ages of 3 and 19. Moorrees17 reported that the arch perimeters of both sexes decreased between the ages of 9 and 14 because of changes in the dentition; this decrease was more significant in girls, and arch length remained constant after the age of 14. Several studies agree with these findings.14,16,17 The main causes of these length changes are the closure of posterior interproximal spaces by the replacement of the deciduous dentition with the permanent dentition, lingual tipping of the anterior teeth (especially maxillary incisors), and the interproximal contacts made by the permanent teeth.16 The arch length decreases in the maxilla and mandible were acceptable in that age group because of the mesial shifting of the permanent first molars. Nevertheless, the decreases we found were smaller than those of previous studies. There was an insignificant decrease in arch depths. This decrease might be related to the mesial shifting of the first molars to leeway spaces. A study of children between the ages of 8 and 14 showed an increase in the molar region transversally, but this increase did not affect the arch dimension.15 In a study of twins, arch depth decreases of 1.3 mm in the maxilla and 1.6 mm in the mandible were reported.19 In our study, the decreases in arch depths were smaller than in the other studies and can be related to individual variations. In several previous studies, the maxillary or mandibular (or both) widths were larger in the male subjects than in the female subjects.30-32 Similarly, in this study, the widths and other parameters were greater in the boys than in the girls (Table II). In our study, arch width changes varied between boys and girls living in the southeastern Anatolia region of Turkey. In girls, there were increases of 1.36 mm in maxillary intermolar width and 1.64 mm in mandibular intermolar width. In boys, the respective values were 1.58 and 0.91 mm. Considering these findings, it can be concluded that the time period studied here represents when most of the transverse growth of the molar region
Arslan et al 576.e19
American Journal of Orthodontics and Dentofacial Orthopedics Volume 132, Number 5
Table III.
Paired samples t test results of changes in parameters during the transition from mixed to permanent dentition and comparisons of these changes between sexes (independent samples t test results) Boys T2 -T1 Measurement (mm) Maxillary arch perimeter Mandibular arch perimeter Maxillary arch depth Mandibular arch depth Maxillary molar width Mandibular molar width Maxillary premolar width Mandibular premolar width Maxillary canine width Mandibular canine width Overbite Overjet Maxillary incisor irregularity Mandibular incisor irregularity
Comparison (T2-T1)
Girls T2 -T1
Mean differences
SD
P
⫺2.30 ⫺1.88 ⫺0.35 ⫺0.75 1.58 0.91 0.70 1.37 1.59 ⫺0.59 0.44 0.17 ⫺0.41 ⫺0.20
1.31 1.71 0.83 0.59 0.65 0.53 0.48 0.59 0.62 0.40 0.02 0.02 0.23 0.78
NS NS NS NS * NS NS * * NS ‡ ‡
NS NS
Mean differences
SD
P
P
⫺0.35 ⫺0.48 ⫺0.48 ⫺0.28 1.36 1.64 1.49 1.88 0.39 ⫺0.11 0.38 0.28 ⫺0.56 ⫺0.40
0.71 0.93 0.54 0.53 0.31 0.51 0.54 0.44 0.59 0.27 0.02 0.02 0.15 0.20
NS NS NS NS
NS NS NS NS NS NS NS NS NS NS NS * NS NS
‡ † † ‡
NS NS ‡ ‡
NS NS
*P ⬍.05; †P ⬍.01; ‡P ⬍.001; NS, not significant. Table IV.
Descriptive statistic and paired t test results of the measurements from casts of the total group in mixed (T1) and permanent (T2) dentition and the change between T2 and T1 T1
T2
Change (T2-T1)
Measurement (mm)
Mean
SD
Mean
SD
Mean differences
SD
P
Maxillary arch perimeter Mandibular arch perimeter Maxillary arch depth Mandibular arch depth Maxillary molar width Mandibular molar width Maxillary premolar width Mandibular premolar width Maxillary canine width Mandibular canine width Overbite Overjet Maxillary incisor irregularity Mandibular incisor irregularity
77.09 68.12 27.45 23.62 44.91 33.21 34.93 25.65 31.59 20.48 1.35 2.12 1.01 1.31
6.21 7.31 2.94 3.13 2.47 2.92 1.83 2.50 3.37 1.91 0.39 0.31 0.28 0.78
76.26 67.54 27.02 23.12 46.37 34.52 36.08 27.30 32.52 20.15 1.77 2.36 0.89 1.11
5.26 6.60 3.00 2.41 3.05 2.97 3.13 2.95 3.82 1.92 0.51 0.36 0.38 0.86
⫺0.83 ⫺0.57 ⫺0.42 ⫺0.49 1.46 1.31 1.14 1.65 0.92 ⫺0.33 0.41 0.23 ⫺0.12 ⫺0.19
5.83 7.46 3.83 3.17 2.71 3.02 3.01 2.91 3.50 1.90 0.38 0.17 0.26 0.69
NS NS NS NS ‡ ‡ † ‡
* NS ‡ ‡
NS NS
*P ⬍.05; †P ⬍.01; ‡P ⬍.001; NS, not significant.
occurs in girls and most of the transverse growth of the maxillary molar region occurs in boys. In the boys, the transverse growth of the mandibular molar region must have occurred before the start of this study. In the boys, the higher values at T1 proved this. In a study conducted in the United Kingdom, decreases were found in intermolar and intercanine widths between the ages of 11 and 14, but those parameters increased between the ages of 24 and 30.10 Moorrees17 found that the mandibular intermolar width increased between the ages of 9 and 14 and remained
constant after the age of 14; our results are consistent with his. There were statistically significant increases in maxillary and mandibular interpremolar widths in the girls and the total group. There was a significant increase only in mandibular interpremolar width in the boys.The increases in interpremolar widths were 1.49 mm in the maxilla and 1.88 mm in the mandible for girls, and 1.37 mm in the mandible for boys. These changes in arch widths are related to the growth and development period and the vestibular
576.e20 Arslan et al
eruption of the permanent teeth. The forward growth of the anterior region of the maxilla during the replacement of the dentition was insignificant, but the lateral growth of the arch to adapt to the permanent dentition was significant. These also affect width increases transversally.33 The reason for the transverse width increases in the maxillary deciduous second molar and the permanent first molar areas is the oblique buccal loading of the alveolar process.34 The maxillary intermolar width increase was insignificant in boys; this might be because their growth and development period ended before the starting time (mixed dentition) of this study. In the study of Lundström19 on twins between the ages of 9 and 19, there were minimal increases in permanent intermolar and interpremolar widths. The Michigan Growth Study11-13 showed premolar width increases in both jaws, with a greater increase in the maxilla than in the mandible. However, in our study, we observed that the increase in interpremolar width was greater in the mandible than in the maxilla. This finding might indicate that growth of maxillary interpremolar width ended before the start of this study. The significant increases in intercanine width were in the maxillary area in boys (1.59 mm) and in the total group (0.92 mm). The main change in mandibular intercanine width was an insignificant decrease in all groups. The intercanine width changes in girls were insignificant, and this finding might indicate that the increase of this parameter by the growth and development period ended before the start (mixed dentition) of this study. Intercanine widths were studied by Barrow and White,16 Moorrees,17 and Sillman,18 who all observed a rapid increase between the ages of 6 and 9 associated with the eruption of the permanent canines and incisors. According to Moorrees,17 a decrease occurs between the ages of 10 and 12, with no change after that. However, other authors16-18 suggested that intercanine width continues to decrease after age 12. In a longitudinal study by Knott,35 there was an average change in intercanine width during the transition from the deciduous to the permanent dentition, but there were highly individual variations during the transition from the mixed to the permanent dentition. In our study, there were insignificant decreases in mandibular intercanine widths in both sexes between the ages of 9 and 14. These differences could be related to genetic or ethnic variations. Sinclair and Little20 found a decrease in mandibular intercanine width between the mixed and early permanent dentitions, consistent with our study.
American Journal of Orthodontics and Dentofacial Orthopedics November 2007
Overjet and overbite exhibited increases in all groups. Overbite increased 0.41 mm overall. Overjet increased 0.23 mm overall. The increase in overbite is probably related to the use of leeway spaces and the mesial shifting of the permanent first molars. The increase in overjet indicates that the translation of the mandible had not yet occurred. Several longitudinal studies reported significant increases in overjet and overbite during the replacement of the dentition.13,17,20,22 Our findings are consistent with those reports. In this study, the irregularity index decreases were statistically insignificant in all groups. In a crosssectional study, Foster et al23 found differences in the pattern of dental arch crowding among 4 age groups; the incidence of mandibular crowding increased to 90% by age 14 and decreased somewhat by age 25. Moorrees17 observed a different pattern. He suggested that there was considerable crowding in the 8-to-10 year age period, corresponding to the eruption of the permanent canines, but that this decreased between the ages of 12 and 14 and then increased again from 14 to 18 years of age. Our finding might be related either to canine and incisor distalization to leeway space or to facial growth. In untreated subjects, attempts to correlate incisor crowding with other dental and skeletal features have been limited because of the difficulties in quantifying incisor crowding and the apparent multifactorial etiology of malalignment. Nevertheless, growth has been implicated by some authors as a primary factor, with Bjork and Skieller36 suggesting that incisor position might be correlated with the amount and direction of facial growth. CONCLUSIONS
After examining diagnostic dental casts taken during the mixed dentition stage and after reaching the permanent dentition stage in 65 untreated subjects, we reached the following conclusions. 1. Our results with Turkish children were compatible with those of studies in other countries. 2. The initial parameters in this Turkish population showed sexual dimorphism; however, during the observation period (T2-T1), there was no sexual dimorphism in arch dimension changes. 3. There were significant changes in arch width parameters (especially in girls), overjet, and overbite in Turkish children between the midmixed and the permanent dentitions. These results should be useful in planning orthodontic treatment for patients in the mixed and early permanent dentitions.
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REFERENCES 1. Graber TM. Normal occlusion. Dent Clin North Am 1968;273-90. 2. Bishara SE, Jakobsen JR, Treder J, Nowak A. Arch width changes from 6 weeks to 45 years of age. Am J Orthod Dentofacial Orthop 1997;111:401-9. 3. Bishara SE, Bayati P, Zaher AR, Jakobsen JR. Comparisons of the dental arch changes in patients with Class II, division 1 malocclusions: extraction vs nonextraction treatments. Angle Orthod 1994;64:351-8. 4. Bishara SE, Cummins DM, Zaher AR. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop 1997;111:18-27. 5. Burke SP, Silveira AM, Goldsmith LJ, Yancey JM, Van Stewart A, Scarfe WC. A meta-analysis of mandibular intercanine width in treatment and postretention. Angle Orthod 1998;68:53-60. 6. Gianelly AA. Arch width after extraction and nonextraction. Am J Orthod Dentofacial Orthop 2003;123:25-8. 7. Shearn BN, Woods MG. An occlusal and cephalometric analysis of lower first and second premolar extraction effects. Am J Orthod Dentofacial Orthop 2000;117:351-61. 8. De La Cruz A, Sampson P, Little RM, Årtun J, Shapiro PA. Long-term changes in arch form after orthodontic treatment and retention. Am J Orthod Dentofacial Orthop 1995;107:518-30. 9. Carter GA, McNamara JA Jr. Longitudinal dental arch changes in adults. Am J Orthod Dentofacial Orthop 1998;114:88-99. 10. Ward ED, Workman J, Brown R, Richmond S. Changes in arch width. A 20-year longitudinal study of orthodontic treatment. Angle Orthod 2006;76:6-13. 11. Moyers RE, van der Linden FPGM, Riolo ML, McNamara JA Jr. Standards of human occlusal development. Monograph 5. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development; University of Michigan; 1976. 12. Van der Linden FPGM. Development of the dentition. Chicago: Quintessence; 1983. 13. Van der Linden FPGM. Facial growth and facial orthopedics. Chicago: Quintessence; 1989. p. 148-52. 14. Brown VP, Daugaard-Jensen I. Changes in the dentition from the early teens to the early twenties: a longitudinal cast study. Acta Odontol Scand 1951;9:177-92. 15. Aprile EC. Sobre histopatologia de la gingivitis (thesis). Buenos Aires: Universidad Nacional de Buenos Aires; 1945. 16. Barrow CG, White JR. Developmental changes of the maxillary and mandibular dental arches. Angle Orthod 1952;22:41-6.
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17. Moorrees CFA. The dentition of the growing child. Cambridge, Mass: Harvard University Press; 1959. 18. Sillman JH. Dimensional changes of the dental arches: longitudinal study from birth to 25 years. Am J Orthod 1964;50:824-42. 19. Lundström A. Changes in crowding and spacing of the teeth with age. Dent Pract Dent Rec 1969;19:218-24. 20. Sinclair PM, Little RM. Maturation of untreated normal occlusions. Am J Orthod 1983;83:114-23. 21. Bishara SE, Jakobsen JR, Treder JE, Stasi MJ. Changes in the maxillary and mandibular tooth-size arch length relationship from early adolescence to early adulthood. A longitudinal study. Am J Orthod Dentofacial Orthop 1989;95:46-59. 22. Bjork A. Variability and age changes in overjet and overbite. Am J Orthod 1953;39:774-801. 23. Foster TD, Hamilton MC, Lavelle CL. A study of dental arch crowding in four age groups. Dent Pract Dent Rec 1970;21:9-12. 24. Krogman WM. The meaningful interpretation of growth and growth data by the clinician. Am J Orthod 1958;44:411-32. 25. Demirjian A, Buschang PH, Tanguay R, Patterson K. Interrelationships among measures of somatic, skeletal, dental, and sexual maturity. Am J Orthod 1985;88:433-8. 26. Ursus RS, Wiltshire WA. Orthodontic probability tables for black patients of African descent: mixed dentition analysis. Am J Orthod Dentofacial Orthop 1997;112:545-51. 27. Bailit HL. Dental variation among populations—an anthropologic view. Dent Clin North Am 1975;29:125-39. 28. Little R. The irregularity index: a quantitative score of mandibular anterior alignment. Am J Orthod 1975;68:554-63. 29. Dahlberg G. Statistical methods for medical and biological students. New York: Interscience Publications; 1940. 30. Cassidy KM, Harris EF, Tolley EA, Keim RG. Genetic influence on dental arch form in orthodontic patients. Angle Orthod 1998;68:445-54. 31. Staley RN, Stuntz WR, Peterson LC. Comparison of arch widths in adults with normal occlusions and adults with Class II, division 1 malocclusion. Am J Orthod 1985;88:163-9. 32. Raberin M, Laumon B, Martin JL, Brunner F. Dimensions and form of dental arches in subjects with normal occlusion. Am J Orthod Dentofacial Orthop 1993;104:67-72. 33. Friel S. Occlusion: observations on its development from infancy to old ageInt J Orthod 1927;13:322-43. 34. Brash JC. Growth of alveolar bone. Int J Orthod 1928;14.291-2. 35. Knott VB. Longitudinal study of dental arch width at four stages of dentition. Angle Orthod 1972;42:387-95. 36. Bjork A, Skieller V. Facial development and tooth eruption. An implant study at the age of puberty. Am J Orthod 1972;62:339-83.