Study of dental arch width in patients with idiopathic condylar resorption / 临床耳鼻咽喉头颈外科杂志

Objective:To investigate the relationship between idiopathic condylar resorption （ICR） and arch width disorder. Methods:Thirty-two patients with ICR and twenty patients without condylar resorption were enrolled according to the same inclusion criteria. They were divided into experimental group and control group. The experimental group was divided into unilateral ICR group and bilateral ICR group according to the affected side of condylar resorption, and then experimental group was divided into subgroups ICR Ⅰ, ICRⅡand ICR Ⅲ according to the degree of condylar resorption. Patients with no condylar resorption were used as a control group. The width of anterior, middle and posterior segments of dental arch on cone beam computed tomography（CBCT） was measured and the two groups of measured values were statistically analyzed. Results:Compared with the control group, the width of maxillary anterior, middle and posterior segments in ICR group was significantly reduced, and the difference was statistically significant（P<0.01）. But the width of mandibular segment was not significantly different from that in control group（P>0.05）. There was no significant difference in the width of anterior, middle and posterior dental arch between subgroups（P>0.05）. Conclusion:Almost all patients with ICR have malocclusion of maxillary and mandibular arch width, but there is no significant correlation between the malocclusion width and the severity of condylar resorption.

Study on the transverse relationship of the mandible between different skeletal vertical patterns in patients with skeletal ClassⅠ malocclusion / 口腔疾病防治

Objective@#To analyze the correlation between skeletal vertical patterns and mandibular dental arch width, basal arch width and the dental buccolingual inclination of patients with skeletal ClassⅠ@*Methods@#The CBCT data of 62 skeletal ClassⅠ malocclusion patients were collected and divided into a high-angle group with 19 cases, a mean-angle group with 22 cases, and a low-angle group with 21 cases according to the GoGn-SN angle. Mandible 3D reconstruction of the three groups was performed using Dolphin software, and dental arch widths, basal arch widths and buccolingual inclination of canines, first premolars and first molars, were measured and statistically analyzed respectively. @*Redults@#Mandibular dental arch width showed no significant difference among the three groups (P>0.05). The basal arch widths of mandibular canines and first premolars in low-angle group were larger than those in the other groups (P<0.05). The buccolingual inclinations of mandibular canines and first premolars in high-angle group were larger than those in the other groups (P<0.05). The buccolingual inclination and basal arch width of the first molars among the three groups showed no significant differences (P>0.05). Pearson correlation tests showed that the basal arch widths of mandibular canines and first premolars were negatively correlated with GoGn-SN angle. Excluding the influence of dental arch width and basal arch width, there was still a significant positive correlation between the buccolingual inclination of mandibular canines and first premolars and the GoGn-SN angle (P<0.05).@*Conclusion@#The width of the basal bone arch between different skeletal vertical patterns mainly differs in the canine segment and the premolar segment, and the difference in the buccolingual inclination of the teeth is mainly to compensate for the difference in the GoGn-SN angle. In clinical practice, individualized therapy should be adopted according to the differences to achieve the long-term efficacy of correction.

Evaluation of Maxillary and Mandibular Arch Widths among Various Malocclusions

Background: Arch dimensions such as arch width, arch lengthand arch form are very significant to orthodontic treatment.Diagnosis of arch length and width discrepancies are importantdiagnostic aids, with the help of which treatment outcome canbe predicted. The present study was conducted to evaluate thearch width among class I normal occlusion, Class II division 1and Class III malocclusions.Materials and Methods: In the present study a total of 75pairs of study models were selected to evaluate the arch widthamong class I normal occlusion, Class II division 1and Class IIImalocclusion. For the evaluation of arch width pretreatmentorthodontic study models were selected from orthodonticrecords. Each malocclusion class consisted of 25 studymodels. Measurements were performed on the orthodonticstudy models using an electronic digital caliper measuring tothe nearest 0.01 mm. One operator measured the arch widthparameters on both jaws. Statistical analysis was performedusing the Statistical Package for the Social Sciences softwareversion 21.0 (SPSS Inc., Chicago, IL, USA). A p-value <0.05was predetermined as statistically significant.Results: In the present study each malocclusion classconsisted of 25 study models of participants seekingorthodontic treatment. Class III and Class I groups showedsignificantly larger maxillary intercanine widths, larger maxillaryintermolar, inter premolar and alveolar widths than Class IIdivision1 groups. In mandible Class III group showedsignificantly larger mandibular intercanine, inter rmolar thanClass I and Class II division 1 groups. Class I shows largerinter-premolar width and inter alveolar width than Class III andClass II division 1 groups.Conclusion: Our study concluded that arch widh dimensionsvary according to malocclusion and hence measurement ofarch width provides important information for diagnosis andtreatment planning.

Lower Dental Arch Widths Changes Following Fixed Orthodontic Treatment

@#To determine the number of cases that are at risk of poor stability in terms of arch width changes following fixed appliances treatment at the Orthodontic Unit, Klinik Pergigian Cahaya Suria, Kuala Lumpur. In a retrospective audit, 101 pre- and post-treatment lower study casts were selected from cases completed in the year 2015 at the Orthodontic Unit, Klinik Pergigian Cahaya Suria, Kuala Lumpur. Samples were measured using a universal caliper by a single calibrated operator. Samples was categorised as extraction or non-extraction types. Arch width changes was determined using paired T-test. The recommended limit was 0mm for inter-canine width, 2 mm for inter-first premolar width and 3mm for inter-second premolar and inter-molar width. Differences were considered “within limits”, if the changes were within the recommended limit ±0.25mm (for possible marginal measurement error) and “expanded”, if above the range for within limits. 42.6% were non-extraction while 57.4% were extraction cases. In the non-extraction group, 52.2% cases had expanded inter-canine widths, followed by inter-first and second premolars (27.9%) and inter-first molar (20.9%) widths. Arch width changes for the inter-first and second premolars and inter-molars widths were statistically significantly different (p<0.05) but bot clinically significant. In the extraction group, 67.2% had expanded inter-canine widths, followed by inter-first premolar (64.3%), inter-second premolar (9.1%) and inter-first molar (5.2%) widths. The inter-canine (M=1.43; SD=2.71, p<0.05) and inter-first premolar (M=2.87; SD=2.61, p<0.05) widths statistically and clinically significant expansion but the inter-second premolar and molar were significantly contracted (p<0.05). The number of cases with expanded arch widths was high regardless of the extraction type.

Validity of pont’s analysis in a sample of Bangladeshi orthodontics patients

To assess the applicability of Pont’s index for arch width prediction among the Bangladeshi population. Materials and Methods: Models of 37 male and 63 female subjects ranging in age between 16 to 25 years were randomly selected out of all patients attending the Orthodontic clinic of Bangabandhu Sheikh Mujib Medical University (BSMMU). Teeth size and arch size were measured to determine the Pont’s value. Results: The reported value of Pont’s ratio is 0.87 +/- 0.08 (premolar) and 0.67 +/- 0.05 (molar). The mean value of Pont’s ratio in the present study is 0.88 +/- 0.07 and 0.67 +/- 0.05 for females, and 0.89 +/- 0.09 and 0.66 +/- 0.05 for males. The reported mean index value of Pont is 0.80 and 0.64 with the differences 0.03 and 0.01 whereas, in this study, index value were 0.87 and 0.67, and the differences are 0.07 and 0.03 respectively which are statistically significant compared to the reported values. Conclusion: Based on the results of the current study, Pont’s index is not applicable in the Bangladeshi population.

Sex Determination by Means of Inter-Canine Width - A Study in Karnataka Population.

Background: Sex determination using dental features is primarily based upon the comparison of tooth dimensions in males and females. Aims and Objectives: To determine the role of inter-canine width in identification of sex of individuals. Methods: 50 subjects were included in the study. Impressions were taken with alginate and study models prepared. Inter canine width was measured in all the cases and findings tabulated. Results: Inter canine width for males were higher than females in both maxilla and mandible. Conclusion: Inter-canine widths can be used as a tool in sex determination.

Analysis of Malay Arch Width and Anthropometric Correlations

@#The objectives of the study were to determine the normal dental arch width of Malays, their correlation with the facial framework and the ideal size of orthodontic impression trays that fit the dental arch. Eighteen adult Malays with normal Class I occlusion were evaluated. Arch width was measured on each subject’s dental cast. Direct anthropometric measurements were taken for 8 facial landmarks. Orthodontic impression trays were tried on each subject’s dental cast to determine the best fitting tray. Correlations analysis was made between the arch widths and the best fitting impression trays used and also with various craniofacial anthropometric measurements. The eight measurements from the craniofacial region were compared with the maxillary and mandibular intercanine, interpremolar and intermolar widths. In the maxillary arch, there were significant correlation between the face width and the interpremolar and intermolar widths respectively, while in the mandibular arch, significant correlations were noted between the mandible depth and the interpremolar and intermolar widths respectively. The most common fitting impression tray was size 6 for the upper jaw and size 5 for the lower jaw. There was a significant correlation between the maxillary intercanine width and the size of the impression trays. The significant correlation between upper and lower interpremolar and intermolar widths and the anthropometric measurements of this Malay population may assist in predicting arch expansion to achieve Class 1 occlusion during orthodontic or maxillofacial surgical treatment. The significant correlation between the upper intercanine width and the size of impression tray can be a useful parameter when determining the size of impression tray.

Comparative study on the influence of two kinds of different self-locking brackets on the dental arch shape change in non-extraction patients / 口腔疾病防治

Objective@# By analyzing changes of dental arch width and length during the aligning and leveling period (non-extraction case) with two kinds of self-locking bracket, compare the difference between the active self-locking bracket with the passive bracket.@*Methods@#The data of dental arch perimeter change amount and dental arch width and length change amount (WU/L3, WU/L4, WU/L5, WU/L6, U/LL) were statistically analyzed using the correlation and regression method by comparing active and passive brackets for the correction of dental arch variations. Two different brackets for the correction of the measured values of the dental arch variations was analyzed by t-test. Results There were statistical relationships between the amount of arch perimeter increase and the amount of width and length increase. The regression equation was statistically significant (P < 0.05), It was greater impacted arch width increase to arch perimeter in the self-locking. The t-test results showed WU3, WL3, WL6, LR 4 measured values (P < 0.05) statistically significant in the active self-locking group and passive group. @*Results @#There were statistical relationships between the amount of arch perimeter increase and the amount of width and length increase. The regression equation was statistically significant (P < 0.05), It was greater impacted arch width increase to arch perimeter in the self-locking. The t-test results showed WU3, WL3, WL6, LR 4 measured values (P < 0.05) statistically significant in the active self-locking group and passive group. @*Conclusin @#Active and passive self-locking bracket have good arch expansion effecting. The active self-locking bracket is slightly dominant than the passive bracket in the expansion of the canine width whereas the active self-locking bracket is better than the passive in the expansion of the mandibular first molar and arch perimeter which should be widely applied to the appropriate cases.

The relationship between arch width and vertical facial skeletal types of the adults with individual normal occlusion / 实用口腔医学杂志

Objective:To analyze the correlation between arch width and different vertical facial skeletal types of the adults with individual normal occlusion.Methods:52 adults with individual normal occlusions(females 31,males 21) were included.According to the values of mandibular plane angle MP-FH,SN-MP measured on CBCT image the subjects were divided into 3 groups(13 cases with highangle,19 with average-angle and 20 with low-angle groups).12 parameters were measured for each sample,including maxillary and mandible arch width and alveolar arch width between canines,between first premolars and between first molars,the difference between the maxillary arch width and mandibular arch width were calculated.The data were statistically analyzed by one-way ANOVA and Pearson~ rank correlation test.Results:In the group of high-angle,average-angle and low-angle the alveolar arch width(mm) between maxillary canines was 38.03 ± 1.90,39.65 ± 1.80 and 39.78 ± 2.20 respectively(P ＜ 0.05).The arch width between maxillary first premolars of high-angle group(37.01 ± 1.60) was smaller than that of low-angle group(38.65 ± 1.30).The arch width difference in canine area between maxillary and mandibular alveolar in high-angle,average-angle and low-angle groups was 7.39 ± 1.82,9.04 ± 1.43 and 9.26 ± 1.67 respectively(P ＜0.05);in maxillary first premolars area in high-angle(6.8 ± 1.59) was smaller than that in averageangle(7.79 ± 1.09),maxillary and mandibular arch width showed no statistical difference.Pearson correlation test showed that among 3 groups,upper and lower alveolar arch width difference in canine and first premolars area was negatively correlated with the mandibular plane angle.while upper and lower arch width difference showed no statistical correlation with the mandibular plane angle.Conclusion:The maxillary middle arch width of the subjects with individual normal occlusion was correlated with vertical facial type.

Maxillomandibular arch width differences at estimated centers of resistance: Comparison between normal occlusion and skeletal Class III malocclusion / 대한치과교정학회지

OBJECTIVE: To evaluate the differences in maxillomandibular transverse measurements at either the crown or the estimated center of resistance (CR), and to compare values between normal occlusion and Class III malocclusion groups. METHODS: Dental casts and computed tomography (CT) data from 30 individuals with normal occlusion and 30 with skeletal Class III malocclusions were evaluated. Using the casts, dental arch widths (DAWs) were measured from the cusp tips, and basal arch widths (BAWs-cast) were measured as the distance between the points at the mucogingival junction adjacent to the respective cusp tips. The BAWs determined from CT (BAWs-CT) images were measured from the estimated CRs of the teeth. RESULTS: None of the DAW measurements or maxillomandibular DAW differences showed statistically significant intergroup differences. In contrast, the maxillary BAWs-CT and BAWs-cast were lesser in the Class III malocclusion group than in the normal occlusion group. The mandibular BAWs-CT were significantly greater in the Class III malocclusion group than in the normal occlusion group. Moreover, the maxillomandibular BAW differences on both CT and cast showed significant intergroup differences in all transverse measurements. CONCLUSIONS: The maxillomandibular DAW differences showed no significant intergroup differences. In contrast, the maxillomandibular BAW differences on both CT and cast showed significant intergroup differences in all transverse measurements. The maxillomandibular BAW differences at the estimated CRs, measured using CT or casts, can reveal underlying transverse maxillary basal arch deficiencies in patients with skeletal Class III malocclusions.

A Preliminary Study of Malay and Chinese Bite Mark in UKM Using Dental Wax / Jurnal Sains Kesihatan Malaysia

Identifi cation of unknown suspect through bite marks has always been challenging. Narrowing list of suspects through sex and race markers is always recommend but rarely utilized due to limited publication in this area. Thus, this preliminary research was aimed to study the difference of bite mark made on dental wax between sex and race. A sample size of 40 UKM undergraduates comprising of Malay (male = 10, female = 10) and Chinese (male = 10, female = 10) were used in this study. Bite mark of subject was obtained through dental wax, digitally scanned and analyzed using Image-J software. Parameters measured were anterior teeth size, intercanine width and anterior teeth relative rotation. Result indicated that mandible left canine tooth size had signifi cant sexual dimorphism (p < 0.05) in differentiating sex. The means for male and female measured were 4.63 ± 1.05 mm and 5.35 ± 0.87 mm respectively. In addition to the result, tooth size of maxillary left canine and mandible left lateral incisor were signifi cantly different (p < 0.05) between races. Means for mandible left canine Malay and Chinese were 5.27 ± 1.01 mm and 4.50 ± 1.22 mm respectively. Furthermore, left lateral incisor mandible had means of 5.15 ± 0.87 mm and 4.60 ± 0.74 mm for Malay and Chinese respectively. Unfortunately, there were no signifi cant differences for intercanine width and anterior teeth relative rotation between the two major races in Malaysia. In conclusion, this research has demonstrated the possibility of using tooth size of mandible left canine, maxillary left canine and mandible left lateral discriminate sex and race.

Changes in Dental Arch and Hard and Soft Tissue Caused by the Self-Ligating Bracket and Conventional Bracket with Non-Extraction Treatment in Maxillary Mild-to-Moderate Crowding Cases / 天津医药

Objective To compare changes in dental arch and soft and hard tissue produced by the Damon Q self-ligating bracket and 3M metal bracket with non-extraction treatment in maxillary mild-to-moderate crowding cases. Meth-ods Eighty seven patients were selected in our study, who were assigned to 4 groups by the crowding degree of maxillary and appliance type:ⅠandⅡcrowding degree using Damon Q self-ligating bracket groups (41 cases);ⅠandⅡcrowding de-gree 3M metal bracket groups (46 cases). We measured lateral cephalometric radiographs and dental casts at both beginning and end of treatment. Paired t-tests and group t-tests were used in statistical analysis to compare the alteration in dental arch and soft and hard tissue. Results There was significant increase in width and length of maxillary dental arch by non-extraction treatment withⅠandⅡcrowding degree maxillary, but the results of both groups were not of statistical difference. To compare hard and soft tissue in two groups withⅡcrowding degree maxillary, the reduction of nasolabial angle, angle of inclination of upper lip, angle of upper lip and lower lip had obvious statistical significance and it is more prominent in self-ligating bracket group than in conventional bracket group. Conclusion Using non-extraction treatment, when maxillary crowding is moderate, ,Damon Q self-ligation bracket group result in more prominent changes of upper lip protrusion than 3M bracket with more marked crowding . Therefore, clinical doctors should pay more attention to choose bracket and treat-ment system for patients with marked crowding of maxillary dentition.

Advance research on space analysis related factors / 医学研究生学报

Orthodontics is the procedure of managing the space .Space analysis is a comprehensive quantitative analysis that can analyze the factors that influence the arch space .It also helps to judge if the treatment goals can be reached , thus helping the treat-ment plan making and guiding clinical orthodontics .And space analysis related factors include crowding , curve of Spee, arch width, arch growth, arch protrusion, mesiodistal angulation, an so on.In this review, we summarizes the above-mentioned factors.

Long-term effect of quad helix expansion of dental arch*☆ / 中国组织工程研究

BACKGROUND: Rapid expansion of the dental arch is an effective way to rapidly expanse the jaw. Compared with rapid expansion, the slow expansion has higher stability and less recurrence, but the reports on the long-term stability of quad helix expansion are rare. OBJECTIVE: To retrospectively analyze the clinical effect of quad helix expansion in orthodontics. METHODS: Twenty-two subjects with dental arch stenosis in mixed dentition and early permanent dentition who experienced an expansion of at least 3 mm with quad helix appliance were selected for this study. Plaster dental casts and posteroanterior radiographs were evaluated at the beginning of the treatment (T1), at the completion of phase I quad helix expansion or ful treatment (T2), and approximately 2 years fol owing the completion of treatment (T3). The distance between two first molars was measured on the model. J point was drawn on the posteroanterior radiograph in order to measure the distance between the bilateral base bones and the molar inclination, as wel as to evaluate the corrective and orthopedic effects of dental arch expansion. RESULTS AND CONCLUSION: Compared with that before expansion, the first permanent molar inclination and the distance between base bones on two sides were significant increased after quad helix expansion; there were no significant differences in the distance between two first permanent molars, first permanent molar inclination and the distance between bilateral base bones on two sides when compared after quad helix expansion and after 2-year fol ow-up (P > 0.05). The results indicate that the long-term effect of quad helix expansion is stable with orthopedic effect.

Changes of the maxillary arch produced by different self-ligating appliance systems during the leveling and aligning phases / 实用口腔医学杂志

Objective:To evaluate the changes in the transverse dimension and the perimeters of the maxillary archs produced by 3 self-ligating appliance systems during the leveling and aligning phases. Methods: 45 patients who had class I skeletal pattern and upper arch crowding 3-6 mm were divided into 3 groups with 15 subjects in every group. The dental casts were analyzed. Results: Statistically significant increases were recorded of all dentoalveolar widths (with the exception of intermolar width measured lingually) and arch perimeters. The increase in arch perimeter showed a significant negative relationship with the individual perimeter of the maxillary arch before treatment. No significant change was found in arch depth. Conclusion: The self-ligating appliance systems produce statistically significant increases in the transverse dentoalveolar width and the perimeter of the maxillary arch during the leveling and aligning phases of treatment.

Effect of orthodontic extraction treatment and non-extraction treatment on esthetical smile / 中华医学美学美容杂志

Objective To investigate the effect of orthodontic tooth extraction and non-extraction on dental arch width and esthetical smile. Methods 100 patients treated without extraction and 100 patients treated by 4 first-premolars extraction were selected. The study models of the patients were measured before and after the treatment and compared statistically. Measurements were made in the maxillary and mandibular canine regions from the most labial aspect of the buccal axial surfaces of the canine roots. Results Before treatment, maxillary and mandibular arch widths were the same between both groups (P＞0.05). In non-extraction group, mandibular arch width of posttreatment was 0.88 mm larger than that of pretreatment (P＜0.001), and maxillary arch width of posttreatment was 0.84 mm large (P＜0.001). In extraction group, mandibular arch width of posttreatment was 1.64 mm larger than that of pretreatment (P＜0.001), and maxillary arch width of posttreatment was 1.50 mm large (P＜0.001). After treatment, the width of mandibular arch in the extraction group was 0.59 mm larger than that in the non-extraction group (P>0.05), while the width of maxillary arch in the extraction group was 0.10 mm less (P>0.05).Conclusion Both extraction treatment and non-extraction treatment do not result in narrower dental arch, but wider. The view that orthodontic extraction results in narrower arch widths and unaesthetic smiling is untenable.

Change in arch width in extraction vs nonextraction treatment / 대한치과교정학회지

OBJECTIVE: This study was performed to investigate the influences of extraction and nonextraction treatment on smile esthetics by measuring dental arch width changes. METHODS: Pretreatment and posttreatment study models of 30 first premolar extraction cases and 30 nonextraction cases were randomly selected to determine whether extraction treatment results in narrow dental arches, and a consequent unaesthetic smile. Arch widths were measured from the cusp tips of the canines and the first molars. Posterior arch widths were also measured at a constant arch depth derived by averaging randomly chosen nonextraction models. RESULTS: The intercanine widths increased significantly in the extraction sample, whereas the intermolar widths decreased significantly. The arch width at a standardized arch depth was significantly wider in the extraction subjects. CONCLUSION: These results elucidate that constriction in arch width is not a materialized consequence of extraction treatment. It leads to postulate that an esthetically compromising effect from narrow dental arches on smile is hardly anticipated with extraction treatment.

Effect of maxillary premolar extraction on transverse arch dimension in Class III surgical-orthodontic treatment / 대한치과교정학회지

Collective changes caused by orthodontic tooth movement evaluated in a specific treatment modality could give suggestive information on the specific treatment strategy. The aim of this study was to investigate retrospectively the characteristics of the orthodontic tooth movement during surgical-orthodontic treatment in order to provide an effective presurgical orthodontic treatment planning for the maxillary premolar extraction modality in the skeletal Class III malocclusion patient. Pre- and posttreatment dental casts of skeletal Class III malocclusion patients with nonextraction (N=24) and the maxillary premolar extraction (N=31) were collected. The angulation and inclination measuring gauge (Invisitech Co. Seoul, Korea) was used to evaluate the orthodontic tooth movement. The changes in the maxillary and mandibular dental arch widths were also measured from the canines to the second molars. As a result, more palatal inclination change in the maxillary dentition was found with the premolar extraction modality than with the nonextraction modality. Linear regression analysis showed that the inter-arch width coordination was mainly due to the inclination changes of maxillary posterior teeth. We conclude that the indications and proper treatment planning for surgical-orthodontic treatment in skeletal Class III malocclusion with maxillary premolar extraction could depend partly on the magnitude of the transverse inter-arch coordination especially in the maxillary dentition.

Tooth size and arch parameters of normal occlusion in a large Korean sample / 대한치과교정학회지

The aim of this study was to establish normative data on the tooth size and arch parameters of Koreans with normal occlusion. This study employed the dental casts of 296 (male: 179; female 117) normal occlusion samples, who were selected from 15,836 adults through a community dental health survey. The mesiodistal diameters of teeth, arch width, and arch length were measured by digital electronic calipers (accurate to 0.01 mm) and Bolton's indices as well as intermaxillary arch width ratios were calculated. In order to ensure reliability, intra- and inter-examiner error were evaluated. Although our dimensional data showed overt differences between genders, the indices and intermaxillary ratios evaluated were the same. The resultant data obtained were compared with the previous data to reveal whether any changes have occurred over the time. The clinical implication of the present findings was also discussed. This biometric study seemed to provide a clinically applicable diagnostic criteria for an individual malocclusion patient.

Relationship of dental crowding to tooth size and arch width / 대한치과교정학회지

The purpose of the present study was to investigate the relationship of dental crowding to tooth size and arch dimension in Korean subjects. Two groups of dental casts with Class I molar relationship, were selected on the basis of crowding. One group, consisting of 82 pairs of study cast (29 males and 53 females), exhibited at least 7 millimeters of crowding in each arch. A second group, consisting of 82 sets of study cast (37 males and 45 females), exhibited normal occlusion with little or no crowding. Mesiodistal tooth diameters, and buccal and lingual dental arch widths were measured and compared between the crowding and normal occlusion groups. Significant differences were observed between the two groups not only in arch widths but also in tooth sizes. The results of the present study suggest that both etraction and expansion can be used as a treatment approach for the crowding cases.