Dental Arch Dimensions in Saudi Adults

Objective The aim of this study was to investigate the arch dimensions (width, length, and depth) in Saudi Arabia. Materials and Methods 169 orthodontic models (73 males and 96 females) made of white stone were selected according to inclusion criteria. Measurement of arch dimensions was taken including width, length, and depth at different reference points. Differences between males and females were tested using independent samples t-test. Results The sample comprised subjects aged 18–33 years old. Most measurements showed higher values for males compared to females. Saudi males showed smaller intercanine widths compared to Caucasians and Southern Chinese but larger widths in females compared to Caucasians and smaller widths compared to Southern Chinese. Saudi males and females showed larger intermolar widths compared to Caucasians but smaller intermolar widths compared to Southern Chinese. For arch length, Saudis showed longer arches compared to Yemenis for both males and females but smaller palatal depths compared to Yemenis. Conclusions Differences in intercanine width, intermolar width, and palatal length and depth were found between Saudis and other nationalities. Male and female participants had differences in most of the measurements.


Introduction
Dental arch dimensions are of special interest for dentists and orthodontists in particular. Changes in the arch width, length, and height can result from orthodontic treatment; hence, an understanding of the dental arch dimensions is crucial [1][2][3][4][5]. Dental arches have been investigated using di erent measurements and reference points, including but not limited to, intercanine, interpremolar, and intermolar widths, either between cusps or fossae, anterior palatal and mandibular lengths, molar vertical distance, total palatal and mandibular lengths, and palatal depth [6][7][8][9][10][11].
Ward et al. have reported signi cant changes in maxillary and mandibular intercanine widths in orthodontically treated group compared to untreated group [12]. In patients treated with Frankel II appliance, signi cant increases in arch width and arch perimeter were found [13].
ere are many studies that have been conducted to investigate the dental arch dimensions and relationships in di erent ethnicities and di erent geographical areas [14][15][16][17][18][19][20]. Few studies have been conducted to investigate arch dimensions in Saudi population [21,22]. erefore, the aim of this study was to investigate the arch dimensions (width, length, and depth) in Saudi adults. FRP/2014/73 and IRB approval was obtained. Inclusion criteria were as follows: (1) Saudi subjects over 18 years of age (2) Class I canine and molar relationships (3) Presence of all permanent teeth up to the second molars (4) No previous orthodontic treatment or facial surgeries (5) No more than mild crowding or spacing (<3 mm) (6) No history of parafunctional oral habits (7) No large restorations or crowns (8) No tooth anomalies Orthodontic models (n � 169; 73 males and 96 females) made of white stone in the orthodontic clinics were examined; those that satis ed the inclusion criteria were selected. Measurements of arch dimensions of the maxilla and mandible (width, length, and depth) were taken as described by Ling and Wong [9] and Al-Zubair [11]. De nitions and illustrations of all variables are shown in Figures 1-4 and Table 1. Two examiners took the measurements using a digital sliding caliper (Carrera Precision CP9806-TF, Max Tool LLC, Calif., USA).

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

Statistical Analysis.
Independent sample t-test was used to determine any statistically signi cant di erences between males and females for each measurement. Interclass correlation coe cient was used to determine interexaminer reliability. SPSS software was used for the statistical analysis (IBM SPSS Statistics for Mac, Version 24.0, IBM Corp., Armonk, NY).

Discussion
In the present study, an e ort was made to establish normal values for some parameters that have never been studied in Saudi. We chose to conduct measurements using many reference points described in the literature to allow for comparison with other populations' measurements [9,11]. Comparison of intercanine widths among di erent populations showed small di erences in Saudis between the present study and other studies and close measurements compared to Caucasians [20][21][22], while Southern Chinese showed the largest arch widths in the canine area (Table 6) [9].
Comparisons of the arch widths at the rst molar showed a di erence of about 1 mm between Saudis in our studies and Saudis in other studies. Southern Chinese were found to have the largest arch width followed by Saudis and then by Caucasians [9,20] (Tables 7 and 8).
Maxillary arch length was found to be larger in Saudis compared to Yemenis in all measurements, while palatal depth slightly larger in Yemenis compared to Saudis [11] (Table 9). e measurements established in the present study can serve as a database to which, orthodontic treatment of Saudi adults can be planned. Limitations of this study include a relatively small sample and that the study was con ned to Riyadh City.   Figure 4: Illustration of the maxillary and mandibular arches' lengths as described by Al-Zubair [11]. Anterior palatal length: the vertical distance from the incisal point to the intercanine distance line; molar vertical distance (palatal length): the vertical distance from the incisal point perpendicular to a line between the mesial lingual cusp tips of the rst molars; total palatal length: the vertical distance from the incisal point to the midpoint of a line between the distal buccal cusp tips of the second molars; anterior mandibular length: the vertical distance from the incisal point to the intercanine distance line; molar vertical distance (mandibular length): the vertical distance from the incisal point perpendicular to a line between the mesial lingual cusp tips of the rst molar; total mandibular length: the vertical distance from the incisal point to the midpoint of a line between the distal buccal cusp tips of the second molar.          International Journal of Dentistry 9