|Year : 2011 | Volume
| Issue : 1 | Page : 14-19
Progressive changes in arch width from primary to early mixed dentition period: A longitudinal study
S Sangwan1, HS Chawla2, A Goyal3, K Gauba4, U Mohanty5
1 Asst. Professor, Department of Pedodontics, Government Dental College, Rohtak, India
2 Former Prof & Head Unit of Oral Health Sciences, PGIMER, Chandigarh, India
3 Professor, Department of Pedodontics and Preventive Dentistry, PGIMER, Chandigarh, India
4 Director & Principal, HS Judge Institute of Dental Science and Research, Punjab University, Chandigarh, India
5 Senior Resident, Unit Oral Health Sciences, PGIMER, Chandigarh, India
|Date of Web Publication||23-Apr-2011|
H. No. 474, Model Colony, Yamuna Nagar, Haryana - 135 001
| Abstract|| |
Objective: The present study was conducted to evaluate, on a longitudinal basis, the changes in intercanine and intermolar widths form the primary to the early mixed dentition periods. Materials and Methods: A total of 38 children aged 4-5 years, with normal occlusion without any proximal caries or any dental anomalies, were selected. The impressions were recorded and casts were prepared. Intercanine and intermolar widths were measured on these dental casts with the help of a digital vernier calliper. After 3 years follow-up, the impressions were recorded again and dental casts were prepared. Intercanine and intermolar widths were measured again at this stage and were compared with the baseline data using the paired t-test and the chi square test. Results: There is a significant increase in the intercanine (3.93 + 1.70 mm) and intermolar width (1.49 + 1.77 mm) during the transition period from primary to early mixed dentition in both the arches and both the sexes. The gender-wise comparison showed a greater increase in males than in females, but this was not statistically significant. Conclusion: A thorough knowledge of growth changes during various stages of the mixed dentition period are important for a pediatric dentist to make an accurate diagnosis and treatment planning during preventive and interceptive orthodontics.
Keywords: Early mixed dentition period, intercanine width, intermolar width, normal occlusion
|How to cite this article:|
Sangwan S, Chawla H S, Goyal A, Gauba K, Mohanty U. Progressive changes in arch width from primary to early mixed dentition period: A longitudinal study. J Indian Soc Pedod Prev Dent 2011;29:14-9
|How to cite this URL:|
Sangwan S, Chawla H S, Goyal A, Gauba K, Mohanty U. Progressive changes in arch width from primary to early mixed dentition period: A longitudinal study. J Indian Soc Pedod Prev Dent [serial online] 2011 [cited 2013 May 23];29:14-9. Available from: http://www.jisppd.com/text.asp?2011/29/1/14/79915
| Introduction|| |
Dental arches are in a state of dynamism due to continuous growth and development to accommodate the permanent teeth, particularly during the transitional period from primary to mixed dentition. These changes occur systematically with age from deciduous to permanent dentition and also in a successional phase.,,, The changes in the dental arch are multifactorial in nature, e.g. site specificity, sutural expansion in maxilla, remodelling of alveolar bone, force due to axial inclinations of the teeth , and interarch relationship of the teeth,  which play an important role. Various parameters of dental arches in primary dentition may improve or worsen as an individual grows from the primary to the mixed and then to the permanent dentition. An adequate knowledge of normal growth and development of dentition and the expected dimensional changes in the arches with age are important and also helpful in preventive as well as interceptive orthodontic procedures, which, at times, become necessary to combat a developing malocclusion.
Normal arch dimensions measured and correlated with growth changes are arch circumference, arch length, intercanine width and bimolar width, etc. The intercanine width has been reported to be relatively stable during primary dentition; but, during transition from primary to mixed dentition, an increase in intercanine width of both maxillary as well as mandibular arches has been observed.  This increase in intercanine width allows the larger permanent incisors to get accommodated in the arch previously occupied by the smaller-sized primary incisors. Further, the measurement of bimolar width in the mixed dentition indicates whether the dental arch is narrow or normal at the premolar and molar region and helps in treatment planning during lateral expansion, if needed. 
These changes in arch dimensions from primary to mixed dentition period have been reported by a number of investigators. Bishara et al.,  Glodsten and Stanton,  Moorrees,  Knott  and others have shown that the arches become broader and shorter with age. Lundstrom  showed that the changes in size and form occur twice, once within the period of primary dentition (approximately 3-6 years) and thereafter again during permanent dentition. A majority of the investigations who have reported this aspect have been involving the western population, with arch dimensions measured during the late mixed dentition and permanent dentition periods. Studies involving primary and early mixed dentition period are relatively few. Therefore, this study was planned to investigate the changes in dental arch width from primary to early mixed dentition stage.
| Materials and Methods|| |
A total of 100 children aged 4-5 years with normal occlusion without proximal caries or dental anomalies were selected from various schools of Chandigarh by Bala et al. in 2002, after obtaining necessary permission from authorities and also from the general outpatient department of the Department of Pedodontics and Preventive Dentistry, OHSC, PGIMER, Chandigarh. After selection of children, the list of phone number and addresses was obtained from the schools. The parents of these children were requested, on phone, to visit the Department of Pedodontics and Preventive Dentistry, OHSC, PGIMER, Chandigarh, where upper and lower impressions were recorded and casts were prepared. On these casts, the intercanine and intermolar widths were measured using a digital vernier calliper (Mituoyo Corporation, Tokyo, Japan), lead pencil and scale at the baseline. These children were recalled after 1 year for evaluation. Of the sample of 100, a total of 55 children came for the second follow-up evaluation. Some of the children who developed proximal carious lesions (n = 17) were excluded from the present study. Thus, a total of 38 caries-free children (21 males, 17 females) could be followed-up longitudinally for another 3 years and were reviewed once in every 3 months. Pit and fissure sealants were applied wherever indicated and children were given preventive advice regarding the use of fluoride dentifrices, restriction of sweet intake not more than three a day and brushing twice a day. Impressions were again recorded at the age of 7-8 years, i.e. 3 years after the baseline examination, and the same arch parameters were measured and compared with the baseline measurements of the same children.
The examining investigator (SS) was standardized for measuring various parameters by repeated sessions of calibration with one of the supervisors (AG) before the start of the cast analysis and recording at the Unit of Pedodontics and Preventive Dentistry, OHSC, PGIMER, Chandigarh. Measurements of specific arch parameters were made directly from the casts using a digital vernier calliper in millimetres to the accuracy of 0.05 mm. All the models were assessed and measured twice. Individual measurements that differed by more than 0.5 mm were measured a third time to resolve the discrepancy. The measurements made on the study models were cross-checked randomly by one of the supervisors (AG) involved in this investigation. Intercanine width was measured by marking the mesiodistal midpoint of canines with a lead pencil and measuring the distance between these markings with a digital vernier calliper.  Intermolar width was measured by marking the central fossae of the second primary molars with the lead pencil on the study casts and then the distance between these central fossae of the second primary molars was measured with the help of a digital vernier calliper in each arch, maxillary as well as mandibular. 
The data were analyzed using SPPS 10. Chi square and paired "t" test were used to determine the change from primary to early mixed dentition period. The results at the follow-up visit were compared with the baseline. Further, these parameters were also analyzed for both the arches and for both the sexes.
| Results|| |
Changes in intercanine width
A significant increase in the intercanine width was noted in both the arches and in both the sexes. In the maxillary arch, a significant increase (P < 0.001) of about 3.93 + 1.70 mm was seen from the primary to the early mixed dentition stage [[Table 1]a], [[Figure 1]a]. Although the increase was higher in males than in females, the gender-wise difference was statistically not significant (P > 0.05). In males, an increase of 4.02 + 2.22 mm was seen, while in females, it was 3.81 + 0.71 mm. In the mandibular arch, a significant increase (P < 0.001) of about 3.46 + 1.77 mm was seen from the primary to the early mixed dentition [[Table 1]b], [[Figure 1]b]. When males and females were compared, a greater increase was noted in males compared with females, but the difference was not statistically significant (P > 0.05). In males, a significant increase (P < 0.001) of about 3.75 + 2.07 mm was seen, while in females, the increase was 3.11 + 1.29 mm, the difference being statistically significant (P < 0.001).
|Figure 1: (a)Changes in intercanine width from the primary (4-5 years) to the early mixed dentition (7-8 years) in children in the maxillary arch|
Figure 1b: Changes in intercanine width from the primary (4-5 years) to the early mixed dentition (7-8 years) in children in the mandibular arch
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Changes in intermolar width
A significant increase in the intermolar width was noted in both the arches and both the sexes. In the maxillary arch, a significant increase (P < 0.001) of about 1.49 + 1.77 mm was noted from a mean value of 39.36 + 2.60 mm at 4-5 years to 40.86 + 2.52 mm at 7-8 years of age [[Table 2]a], [[Figure 2]a]. When males and females were compared, a greater increase was noted in males than in females, but the difference was not statistically significant (P < 0.05). In males, the increase was 1.73 + 2.61 mm, while in females, the increase was 1.19 + 1.24 mm from 4-5 years to 7-8 years of age.
|Figure 2: (a)Changes in intermolar width at the second deciduous molar region from the primary (4-5 years) to the early mixed dentition (7-8 years) in children in the maxillary arch|
Figure 2b: Changes in intermolar width at the second deciduous molar region from the primary (4-5 years) to the early mixed dentition (7-8 years) in children in the Maxillary Arch Mandibular Arch
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In the mandibular arch, a significant increase (P < 0.001) of about 1.04 + 1.54 mm was noted from a mean value of 35.02 + 1.96 mm at 4-5 years to 36.05 + 2.05 mm at 7-8 years of age. When males and females were compared, a greater increase was noted in males than in females, although the difference was not statistically significant [[Table 2]b], [[Figure 2]b]. In males, a significant increase (P < 0.001) of about 1.28 + 1.90 mm was seen, while in females, a significant increase of 0.74 + 0.92 mm was seen from 4-5 years to 7-8 years of age (P < 0.001).
| Discussion|| |
Teeth do not remain in the same position in which they erupt into the oral cavity. Instead, the relationships change systematically within the deciduous dentition, during the mixed dentition phase and again during the permanent dentition. One assumes that the changes are an accommodation to the functional, perioral and other forces placed on the teeth.
Brudi and Moyers  suggested some important points while studying the dental arch changes, which are as follows: (1) the dimensional increase in width, which involves the growth of the alveolar process with little increase in skeletal width, particularly in the mandibular arch and (2) the direction of vertical alveolar growth differs significantly in the maxillary and the mandibular arches. Maxillary alveolar processes diverge as the teeth erupt, whereas the growth of the mandibular alveolar process is more parallel. Such changes have significant clinical implications because they may allow for a greater differential increase in the maxillary arch width during treatment.
The present investigation also showed similar trends regarding the changes in the anterior and posterior arch width. Further, in the present study, a significant increase in the intercanine width was noted from the primary to the early mixed dentition period. The increase in intercanine width was found to be higher in the maxillary arch, which was (3.93 + 1.70 mm) 0.47 mm more as compared with that in the mandibular arch (3.46 + 1.70 mm). This difference can be attributed to the fact that the maxillary alveolar processes are divergent whereas the mandibular processes are more or less parallel. Some studies in the literature have shown a similar increase in intercanine width during the transition period. Barrow and White (1952)  reported an almost similar increase in intercanine width, i.e. a 4-mm increase in maxilla and a 3-mm increase in mandible between 5 and 8 years in 51 American children. Knott (1972)  reported an increase in the maxillary arch width of 2.8 mm as compared with a 4.0-mm increase in the present study from 5 to 6 years of age to 9 to 10 years; the increase in maxillary arch in their study ranged between 1.2 and 4.9 mm and in the mandibular arch, between 1.3 and 3.8 mm. Powell and Harris (2000)  reported a 5-mm increase in the intercanine width in the maxilla between 6 and 8 years of age and a 4-mm increase in the mandible between 3 and 10 years of age. The findings of the latter two studies cannot be compared with that of the present investigation because of the wider age ranges studied. Further, in the present investigation, when increase in intercanine width was compared between males and females, it was seen that a greater increase was evident in males compared with females, which was higher in the maxillary arch compared with the mandibular arch, i.e. it was 4.02 + 2.22 mm in males and 3.81 + 0.71 mm in females in maxilla and 3.75 + 2.07 mm in males and 3.11 + 1.29 mm in females in mandible. The disparity could be due to males having broader arches than females and also because of the maxillary arch being broad compared with the mandibular arch. Bishara et al. (1997)  also showed a similar disparity in increase in width in the two arches between males and females over a 10-year study period between 3 and 13 years, i.e. 6.3-mm increase in the maxillary arch in males and 5.7 mm in females compared with 3.6 mm in males and 3.9 mm in females in the mandibular arch.
An increase in the intermolar width was noted from the primary to the early mixed dentition period in the present investigation. According to Moyers (1976),  during this period, the increase is mainly because of the growth of the alveolar processes. This increase was found to be 1.49 + 1.76 mm in the maxilla and 1.04 + 1.54 mm in the mandible. The reasons for greater value in the maxilla could be the distolabial inclination of the maxillary permanent molars as compared with the mandibular permanent molars, which are somewhat lingually tilted. Barrow and White (1952),  however, reported an almost similar increase in the intermolar width of 1.5 mm in both the arches between 5 and 8 years of age. Similar trends of an increase in intermolar width have been shown by Sillman (1964)  between 4 and 13 years of age, an increase of about 0.5 mm per year in the maxilla and 0.2 mm per year in the mandible. Hopp and Meredith (1956)  reported 1.7-mm increase in the intermolar width in 77 children between 4 and 8 years of age. Knott (1972)  also reported an increase in the intermolar width by 1.83 mm in the maxilla and 1.4 mm in the mandible between 5 and 6 years to 9 and 10 years of age. When the increase in the intermolar width was compared between males and females, the increase was higher in males as compared with that in females, and was also higher in the maxillary arch as compared with the mandibular arch. This could be due to the fact that males have broader arches than females and maxillary arches are also broader than mandibular arches as the maxillary alveolar processes are more divergent compared with the mandibular alveolar processes, which are more or less parallel.
| Conclusion|| |
It can be concluded that changes in arch width are comparable with those of the western population, and a significant increase in intercanine and intermolar width was noted during the study period. Thus, a thorough knowledge of growth changes during the transition period is important for the pediatric dentist in making an accurate diagnosis and treatment planning for space management and during preventive and interceptive orthodontics. As we know, the arch parameters are growth dependent, which change with age. Thus, to study these growth changes, it is necessary to study the skeletal condition and its relationship with the dental conditions. This requires additional radiographic assessment in the same children. This important aspect should be taken up in the future endeavours, which will help in reaching at more concrete conclusions about the skeletal and dental growth changes in various arch dimensions with age.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]