1

  COVER LETTER
It is stated that the submitted work has not been published before and is not being considered for
publication elsewhere and that if approved after review it will not be withdrawn.
AUTHORS
1. Dr Bushra Amin. BDS ,M Orth .UK Assisstant professor at khyber college of dentistry. E-
mail: bushraamin@gmail.com Cell: +92 3376126155.

2. Sadia Naureen. Dr Sadia Naureen, BDS, FCPS, Assistant Professor Orthodontics, Rawal
Institute of Health Sciences. E-mail: drsaadis12@gmail.com Cell: +92 3134146936

3. Col Hameed Ullah Jan (R), BDS, Dip Orth, MCPS, FCPS,(Pak) OJT (USA), Prof of
orthodontics & Chairman H.U. J, Smile Orthodontics, Dental Professionals & Research.
Centers: Peshawar, Rawalpindi & Islamabad. Email: Huj100@hotmail.com Cell:
03335124949

4 Dr Tariq Hameed, BDS, ex resident MDS, Maxillofacial Surgery, Peshawar. E mail;

drtariqhameed@live.com

5. Capt Umer Hameed, BDS, Dental officer MDC, CMH Skardu. E mail;
umerhameed0@gmail.com

Corresponding Author: Sadia Naureen. Assisstant professor at Rawal Institute of

Health Sciences. Islamabad. Phone no: 03134146936. E mail: drsaadis12@gmail.com

CONTRIBUTION OF AUTHORS
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Bushra Amin: Data collection and statistical analysis.

Sadia naureen : Corresponding author. Introduction .material and methods.

Col Hameed Ullah Jan: Discussion.

4 Dr Tariq Hameed : Results and figures.

5 Capt Umer Hameed: Referrences.

DECLARATION
It is hereby declared that all the work submitted is the original research of authors. This article
has not published any where nor it is under consideration for publication by any journal.
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Comparison Of Intermolar Arch width before and after alignment phase of Orthodontic
Treatment
Bushra Amin, Sadia naureen ,Col Hameed Ullah Jan: Discussion.,Dr Tariq Hameed : Results and
figures, Capt Umer Hameed: Referrences.

ABSTRACT
Arch width changes introduced from fixed appliance treatment are significant to the
orthodontist. An understanding of these changes is of utmost vitality to the clinician in terms of
treatment planning.
The purpose of this study is to determine and compare the inter-molar arch width in classII div I
cases before and four months into orthodontic treatment (fixed Mechanotherapy).
It was a cross sectional interventive study carried out in orthodontic department of Armed Forces
Institute of Dentistry AFID, Rawalpindi. Minimum duration of study was one year in which data
was collected. 208 patients of class II DIV 1 malocclusion were selected by non probability
purposive sampling. The age range of sampe was between 15-25 years. Upper arch impressions
were taken and maxillary intermolar width was measured on the study casts before and six
months into orthodontic treatment.Standard arch wires were used starting from .012 Niti upto .
019x.028 Niti. Intermolar arch width was taken as the transverse distance from the central fossa
of first molar on one side to the central fossa of first molar on the other side of the same arch.
The pretreatment mean values of intermolar arch width in females and males were found to be
45.01 ± 2.4mm and 46.6 ± 2.6mm respectively. However the posttreatment T2 mean intermolar
arch width was found to be 46.7 ± 2.4mm in females and 48.4 ± 2.7mm in males
Conclusion: There was a mean increase of 1.7mm in pre and post treatment intermolar arch
width so an orthodontist should be cautious in arch expansion mechanics specially when the
treatment plan is non extraction.
Key Words: Intermolar Arch width, Arch form, Class II div 1 malocclusion.

INTRODUCTION: Investigators have historically described the dental arches in simple

geometric term such as ellipse, parabola, and segments of circles joined to straight line or
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modified spheres. The proposed ideal arrangement of the teeth was described geometrically by
Angle as the line of occlusion.1-3 Dental arch dimensions are of special interest for dentists and
orthodontists in particular. In determining the normal dental arch width of a population,
intermolar width (IMW) is a key measurement which assists in diagnosis and treatment planning
of orthodontic patients, especially in patients requiring expansion as an alternate to premolar
extractions in a patient having narrow dental arches.4 Changes in the arch width, length, and
height can result from orthodontic treatment; hence, an understanding of the dental arch
dimensions is crucial.5,6 Dental arches have been investigated using different measurements and
reference points, including but not limited to, inter canine, inter premolar, and inter molar
widths, either between cusps or fossae.6 Numerous dental arch indices have been proposed, such
as, Pont and Schwarz proposed numerical indices. Howe concluded that ideal IMW are 37.4 mm
in boys and 36.2 mm in girls. However all indices gave poor estimation of maxillary arch width.
For index validity, actual upper arch width should be as close as possible to predicted arch
widths, in normal occlusion subjects. There exist certain racial differences in terms of norms of
mean IMW width. IMW in Kuwait residents was 51.32 mm ± 2.6110, in Colombian subjects
mean IMW was found to be 45.9±3.9, in Karachi population it was 45.6 mm±2.3, and in
Nepalese it was 47.94±3.34. In general, IMW dimension remains very stable with some degrees
of sexual dimorphism present. The findings of one study indicated that maxillary dental arch
width measurements were significantly narrower in the Class III group as compared to normal
occlusion group (P < .001).7
The size and shape of the arches have considerable implications in orthodontic diagnosis and
treatment planning, affecting the space available, dental esthetics, and stability of the dentition 8.
Change in arch width dimension involves the growth of the alveolar process almost totally and
little skeletal width increase particularly in the mandiblular arch. Specifically, maxillary alveolar
processes diverge as the teeth erupt; whereas the growth of the mandiblular alveolar process is
more parallel. Generally the maxillary width increases are much greater and can be more easily
altered with treatment 9.
Knowledge of arch dimensions is useful in providing a smooth occurrence of transient
malocclusion, in predicting future orthodontic problems, normal occlusal changes in mixed
dentition, and proper sequential exchange of permanent teeth.10
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Arch width changes resulting from fixed appliance treatment are important to the orthodontist.
An understanding of these changes is of utmost importance to the clinician in terms of treatment
planning. The purpose of this study is to evaluate the inter molar width changes in the maxilla
before and four months after the orthodontic treatment with fixed mechanotherapy.

MATERIALS AND METHODS:

It was a cross sectional interventive study that wass conducted in the department of orthodontics
& Dentofacial orthopedics of Armed Forces Institute of Dentistry AFID, Rawalpindi from the
period of Octobor 2009 to December 2010. In this study, 208 pairs of study models were
prepared from these patients who had class II DIV 1 malocclusion with the age range of 15-25
years from the outdoor patients of Orthodontics Department of AFID during the above
mentioned time period. The inclusion criteria was Class II div I cases with mild to moderate
crowding. No anterior and posterior open bite was present in selected cases and there was no
history of previous orthodontic treatment. No extraction was done before starting the orthodontic
treatment. Upper arch impressions were taken and maxillary inter molar width was calculated on
the study casts before the start of treatment with thhe help of a digital Vernier caliper to the
nearest of 0.01mm. MBT bracket system designed for class II div I cases was used on al patients
The inter molar width was agaiin measured after a period of six months into orthodontic
treatment. Standard arch wires were used starting from .012 Niti upto .019x.028 stanless steel
wire.a digital dial caliper to the nearest 0.01mm. All measurements of all subjects were carried
out again four weeks later by same operator to evaluate measurements error. Almost all the
measurements were same, where differed, average was taken. Inter molar arch width was taken
as the transverse distance from the central fossa of first molar on one side to the central fossa of
first molar on the other side of the same arch. After collection of data the obtained data was
checked, verified& edited. These were entered in a personal computer using the SPSS (statical
package for social science) 16 software. T test was applied for analysis of data.Level of
significance was set at <.05.

METHOD ERROR:
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For the purpose of calibration, the two examiners took all the measurements on 20 dental models
and then their measurements were compared.

RESULTS:

The total sample size comprised of 208 individuals of class II div 1 patients. The age range of the
patients was between 15 years to 25 years. The mean age of the sample was 17.6 years ±2.7.
Table 1. The most frequent age group was 15 years (22.6%).

Gender distribution (Figure 1) comprised of 131 females( 63%) and 77 males (37%). The most
frequent age in females was 14 years and in males it was 18 years.

The mean values of intermolar arch width in the overall sample were found to be 45.6mm ±
2.62mm at T1 and 47.3mm ± 2.69 at T2.(Table 2) The pretreatment mean values of intermolar
arch width in females and males were found to be 45.01 ± 2.4mm and 46.6 ± 2.6mm (figure 2)
respectively.However the posttreatment T2 mean intermolar archwidth was found to be 46.7 ±
2.4mmmm in females and 48.4 ± 2.7mm in males (FIGURE 3) .
Most frequent values in the overall sample for intermolar arch width were found to be 45mm at
T1 and 47mm at T2.(Figure4).Most frequent value for pretreatment intermolar arch width was
found to be 45mm in females and 46mm in males however most frequent post treatment values
for intermolar arch width were found to be 47 mm in both males and females.(Figure5).

The pre and post treatment intermolar arch widths were analysed by paired sample t Test to
assess the significance of difference.Results showed that there was a significant increase in arch
width four months after appliance p;acement p value 0.00 which is highly significant.(Table 3).
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DISCUSSION:
In our study the mean age of the sample was calculated to be 17.6 years ±2.7. Gender
distribution (Figure 1) consisted of 131 females (63%) and 77 males (37%). The most recurrent
age in females was 14 years and in the males it was 18 years. The inter-molar arch width is
typically established till this age. All the patients were in the permanent dentition stage but still
margin of residual growth was present in most of the patients so we cannot absolutely compare
the inter molar width of our study with other studiess.
The mean value of inter molar arch width in the overall sample were found to be 45.6mm ±
2.62mm at T1 and 47.3mm ± 2.69 at T2.(Table 2) The pretreatment mean values of inter molar
arch width in females and males were found to be 45.01 ± 2.4mm and 46.6 ± 2.6mm (figure 2)
respectively. However the posttreatment T2 mean inter molar arch width was found to be 46.7 ±
2.4mm in females and 48.4 ± 2.7mm in male. During the transitional dentition, increases in arch
width occur at a greater degree in maxilla than in the mandible. Followed through adolescence
into adulthood, inter molar width changes vary depending on the longitudinal sample, with some
investigators reporting increases, and others finding no significant changes for males and females
and few showing decreases for females.13,17In our study the greater intermolar arch width in
patients with class II div 1 malocclusion could be attributed to the racial differences, however
differences in the method of measurement can also contribute to arch width differences.
In previous studies comparison between widths of Class II division 1 and Class II
division 2 malocclusion groups with the transverse measurements of untreated normal occlusion
subjects was done. Class II division 2 dental casts had maxillary and mandibular inter canine
distances greater than average and normally distributed inter molar distances. Most of these
studies presented a limited sample size resulting iin questionable validity. No difference in the
mean maxillary and mandibular dental arch and alveolar width dimensions among Class II
division 1, Class II division 2, and a normal occlusion sample was found.18,19
Because orthodontists must often modify arch widths, there is a rich history of
attempts to individualize predictions Some of the authors evaluating transverse dimensions had
reported that maxillary arch was narrower in patients with Class II, division 1 malocclusion, and
an expansion was needed during or before treatment.20In a local study by Bhutta and Israr
concluded that no dental and alveolar differences exist between the two malocclusion samples i-
 8

e Class II div I and Class II div II except that the mandibular inter canine and inter premolar
alveolar widths are significantly narrower in class II samples.21. Most recently Yang and Chung
compared the bucco lingual inclination of the molars of untreated adults and children. The
conclusion drawn was that the maxillary first molars exhibited buccal inclination, and the
inclination in adults is more palatal than that in children.23 Our sample comprised of class 2 div 1
malocclusion in which mean pretreatment arch width was 45.6mm± 2.6mm in class 2 div 1
patients which is higher than normal. In another study, a net gain of six mm was achieved in the
maxillary arch perimeter, whereas a net gain of 4.5 mm was found for the mandibular arch
perimeter of treated subjects in the long term. The duration of retention with a fixed lower
appliance in the posttreatment period did not appear to affect the long-term outcomes of the
treatment protocol significantly. The amount of correction in both maxillary and mandibular
inter molar widths equaled two-thirds of the initial discrepancy. 22 In another study, the maxillary
bilateral first molars exhibited palatal inclination over two years, while the mesiodistal
inclination did not change significantly.8 According to a local study4 children with Class II
malocclusion have narrower maxillary arches than those with normal occlusion. Maxillary inter
canine and inter premolar arch widths were, on average, 0.8 to 0.9 mm smaller than expected.
The mean age of the subjects was 18.23±3.75 years. The mean value of inter molar (IMW) in
selected subjects was 45.33±3.42 mm. Study results concluded that in Pakistanis, ideally aligned
maxillary arch and occlusion can be achieved with upper inter molar distances of 45.33±3.42
mm. There exist certain racial differences in terms of norms of mean IMW width. IMW in
Kuwait residents was 51.32 mm ± 2.61 in Colombian subjects mean IMW was found to be
45.9±3.9, in Karachi population it was 45.6 mm±2.3, and in Nepalese it was 47.94±3.34. In
general, IMW dimension remains very stable with some degrees of sexual dimorphism present.
The findings of Uysal and Memili indicated that maxillary dental arch width measurements were
significantly narrower in the Class III group as compared to normal occlusion group (P < .001) 19.
Motamedi found that inter molar width of the extraction group decreased significantly during
treatment. In contrast to the extraction group, the control and non-extraction groups both
demonstrated an increase in mean inter molar width which was 0.66 mm and 0.91 mm
respectively.24

Shapiro26 measured the inter molar and inter canine width of 80 cases 10 years post-retention and
compared the results with post-treatment and end-of-treatment figures. He concluded that
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mandibular inter canine width has a strong tendency to return to its pretreatment dimension in all
groups, i.e., extraction, non-extraction, class I, class II division 1 and class II division 2.On the
contrary, Walter,2 studied the plaster models of 102 North American, white patients between the
ages of 6 and 36, 1-13 years following the removal of retaining devices, concluded that the
dental arch can be permanently widened or lengthened. A study by Steadman 27of 31 cases out of
retention or more years indicated that the ultimate inter molar width of the maxillary and
mandibular first molars and the ultimate inter canine width of the maxillary and mandibular
canines are not determined by orthodontic treatment. He noted that premolar extraction
decreased the maxillary and mandibular inter molar widths but produced no discernible
differences in maxillary and mandibular inter canine width. In contrast to the extraction group,
the control and non-extraction groups both demonstrated an increase in mean inter molar width
during the first period of observation.2These results are similar to our study where alignment was
done for six months till .019x.028 stainless steel wire was passed. So in non extraction cases of
class II div I an Orthodontist should expect a mean increase of 1.7mm during routine
orthodontic treatment. This should be taken into consideration while planning the treatment of
constricted maxillary arch. The limitation of our study was that we did not measre the inter molar
arch width at post treatment and post retention periods to assess the stability of our results.
Future studies should be planed to assess these changes.Furthermore intermolar arch width
changes in extraction cases also needs further research.

CONCLUSION:

We conclude from this study that in class II div I cases inter molar width automatically increases
by 1.8 mm in initial alignmet phase of fixed mechanotherapy with standard archwires. Any other
espansion measures were not taken during initial three months of treatment. Although the
increase in inter molar width was significant, still further studies are needed to assess the amount
of expansion with heavy wire in extraction/non extraction cases and post treatment stability of
this expansion.
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REFERENCES:
1. Rabbani R M G,Ali M W, Jahan E, Hasan N, Hossain M Z. A comparative Study of Arch
Widths between Class I Crowded with Normal Occlusions. Update Dental College Journal. 2018
; 8(2): 14-17
2. Al-Khateeb SN, Abu Alhaija ESJ. Tooth size discrepancies and arch parameters among different
malocclusions in a Jordanian sample. Angle Orthod. 2006;76:459-65.
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3. Al-Hilal LH, Sultan K, Hajeer MY, Mahmoud G, Wanli AA. J Contemp Dent Pract. 2018;
19(4):431-37.
4. Azeem M, Haq A, Iqbal J, Iqbal A, Hamid W. JBUMDC 2018; 8(3):139-141
5. Lione R, Buongiorno M, Franchi L, Cozza P. Evaluation of maxillary arch dimensions and
palatal morphology in mouthbreathing children by using digital dental casts. International journal
of pediatric otorhinolaryngology. 2014;78(1):91-5.
6. Alkadhi O H, Almahfouz S F, Tokhtah H A, Binhuwaishel L A. Dental Arch Dimensions in
Saudi Adults. Int J Dent. 2018; 
7. Uysal T, Usumez S, Memili B, Sari Z. Dental and alveolar arch widths in normal occlusion and
Class III malocclusion. The Angle orthodontist. 2005; 75(5):809-13.
8. Yang D, Liang S, Zhang K, Gao W, Bai Y. Evaluation of Growth and Development of Late
Mixed Dentition Upper Dental Arch with Normal Occlusion Using 3-Dimensional Digital
Models. J Healthc Eng. 2019;2019:4191848. Published 2019 Nov 14. doi:10.1155/2019/4191848
9. Park S J, Leesungbok R, Song J W , Chang S H , Lee1 S W , Ahn S J. Analysis of dimensions
and shapes of maxillary and mandibular dental arch in Korean young adults. J Adv Prosthodont
2017;9:321-7.
10. Yang B ,Chung C H, Buccolingual inclination of molars in untreated children and adults. a cone
beam computed tomography study. Angle Orthod (2019) 89 (1): 87–92.
11. Santana L, Motro M, Bamashmous MS, Kantarci A, Will LA. Buccolingual angulation and
intermolar width changes in the maxillary first molars of untreated growing children. Am J
Orthod Dentofacial Orthop. 2017 May;151(5):921-928. 
12. Eslami Amirabadi G, Golshah A, Derakhshan S, Khandan S, Saeidipour M, Nikkerdar N. Palatal
dimensions at different stages of dentition in 5 to 18-year-old Iranian children and adolescent
with normal occlusion. BMC Oral Health. 2018 May 15;18(1):87.
13. Oliva, B., Sferra, S., Greco, A.L. et al. Three-dimensional analysis of dental arch forms in Italian
population. Prog Orthod. 2018;19 (1):34, 2018.
14. Shahid F, Alam MK, Khamis MF. Maxillary and mandibular anterior crown width/height ratio
and its relation to various arch perimeters, arch length, and arch width groups. Eur J Dent. 2015
Oct-Dec;9(4):490-499.
15. Omar H, Alhajrasi M, Felemban N, Hassan A. Dental arch dimensions, form and tooth size
ratio among a Saudi sample. Saudi Med J. 2018;39:86–91.
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16. Tsujino K, Machida Y. A longitudinal study of the growth and development of the dental arch
width from childhood to adolescence in Japanese. Bull Tokyo Dent Coll. 1998;39(2):75-89.
17. Ribeiro, Jucienne Salgado, Ambrosio, Aldrieli Regina, Santos-Pinto, Ary dos, Shimizu, Isabella
Almeida, & Shimizu, Roberto Hideo. (2012). Evaluation of transverse changes in the dental
arches according to growth pattern: a longitudinal study. Dental Press Journal of
Orthodontics, 17(1), 66-73.
18. Uysal T, Memili B, Usumez S, Sari Z. Dental and alveolar arch widths in normal occlusion, class
II division 1 and class II division 2. Angle Orthod. 2005 ;75(6):941-7.
19. Bishara SE, Bayati P, Jakobsen JR. Longitudinal comparisons of dental arch changes in normal
and untreated Class II, division 1 subjects and their clinical implications. Am J Orthod
Dentofacial Orthop. 1996; 110: 483-489.
20. Bhutta N, Israr J, Ijaz A. Comparison of dental and alveolar arch widths in class i and class ii
division 1 malocclusion. PODJ .2013;33(2) :289-97.
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fixed appliances: a long-term evaluation of changes in arch dimensions. Angle Orthod. 2003;
73(4):344-53.
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normal occlusion, Class II Division 1, Class II Division 2, and Class III malocclusion in Indian
population. Contemp Clin Dent. 2015;6 (Suppl 1):S202-9.
23. Motamedi AK, Dadgar S, Teimouri F, Aslani F. Stability of changes in mandibular intermolar
and intercuspid distances following orthodontic treatment. Dent Res J (Isfahan). 2015;12 (1):71-
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24. Walter DC. Changes in the form and dimensions of dental arches resulting from
orthodontic treatment. Angle Orthod.1953;23:3-18.
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Angle Orthod.1961;31:207-15.
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Descriptive Statistics
N Minimum Maximum Mean Std. Deviation
AGE 208 15.0 25.0 17.649 2.7092
Valid N
208
(listwise)
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Table 1: mean age

Table 1.Mean age of the sample

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Table 2. Mean arch width

Descriptive Statistics
N Minimum Maximum Mean Std. Deviation Table 2.
Mean ARCH WIDTH arch
208 39.00 54.00 45.6154 2.62212
widths at T1 T1 and
ARCH WIDTH
T2 208 41.00 56.50 47.3317 2.69739
T2
Valid N
208
(listwise)
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Paired Samples Correlations Table 3.

Paired N Correlation Sig. Sample T
test Pair 1 ARCH WIDTH T1 &
208 .967 .000
ARCH WIDTH T2
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37%

FEMALES
MALES

67%

Figure 1.Distribution of males and females

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47
46.6
46.5

46
females
45.5
males
45 45.01

44.5

44

Figure 2. Mean intermolar arch width at T1 in males and females

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48.5 48.4
48

47.5
females T2
47
46.7 m ales T2
46.5

46
45.5

Figure 3. Post treatment mean arch width in males and females

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48.5 48.4
48

47.5
females T2
47
46.7 m ales T2
46.5

46
45.5

Figure 3. Post treatment mean arch width in males and females

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47
46.5
46
45.5 47
Arch w idth T1
45 Arch w idth T2
44.5 45
44
Arch Arch
w idth T1 w idth T2

Figure 4 .Most frequent arch width at T1 and T2.

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47
46.5
46
45.5 T1
45 T2

44.5
44
MALES FEMALES

Figure 5. Most frequent intermolar arch width in males and females at T1 and T2.