diagnosis of arch length and width discrepancies are important diagnostic aids , with the help of which an orthodontist can predict the treatment outcome of a particular case . it is essential for an orthodontist to have knowledge of normal growth and development of dentition and the expected spatial changes in the arches with age . it will help in preventive as well as interceptive orthodontic procedures , which , at times , become necessary to deal with developing malocclusion . ample factors such as heredity , growth of the bone , eruption and inclination of the teeth , external influences , function , and ethnic background could affect the size and shape of the dental arches . the evaluation of dental arches is important for proper diagnosis and treatment planning of any orthodontic case as it affects the availability of space , esthetics , and stability of the dentition . these considerations , in association with the antero - posterior movements of the dentition , will also help in determination of the need for extraction or nonextraction treatment . they facilitate the analysis of tooth size and shape ; alignment and rotations of the teeth , arch width , length , form and symmetry and the occlusal relationship . knowledge of arch widths associated with class ii ( cii ) and class iii ( ciii ) malocclusions is essential for determination of treatment goals and likely posttreatment sequel for these malocclusions . however , there is little information available regarding this issue among the indian population where there is a relatively large demand for orthodontic treatment . the objectives of this study was to test the hypothesis that there is no difference between class i ( ci ) normal occlusion , class ii division 1 ( ciid1 ) and class ii division 2 ( ciid2 ) , and ciii malocclusion with respect to arch widths , width of the maxillary and mandibular arches , gender dimorphism within groups and gender comparisons . study models of 40 subjects ( 20 males and 20 females in each category ) are selected in ci , ciid1 , and ciid2 occlusion groups . study models of 34 subjects ( 20 males and 14 females ) are selected for ciii group . the minimum age of the subjects chosen for this study is based on earlier evidence reporting no significant change occurring in intermolar widths at permanent first molars and canine arch widths between permanent canines after 13 years in girls and 16 years in boys . the inclusion criteria for ci normal occlusion are first molars bilaterally in ci in centric occlusion , with mesiobuccal cusp tip of the maxillary first molar occluding with the buccal groove of the mandibular first molar , overjet not more than 4 mm , teeth well aligned within the dental arches with <3 mm of crowding or spacing and no teeth in crossbite . for ciid1 group , there should be bilateral cii molar relationship in centric occlusion , with the distobuccal cusp tip of the maxillary first molar occluding with the buccal groove of the mandibular first molar , labially inclined maxillary incisors , and overjet > 7.5 mm . one male and one female subject in ciid1 have posterior crossbite . for ciid2 group , along with bilateral cii molar relationship in centric occlusion , there should be at least one maxillary central incisor inclined lingually , overjet not more than 5 mm , deep overbite , and no teeth in crossbite . for ciii group , there should be bilateral ciii molar relationship in centric occlusion , with the mesiobuccal cusp tip of the maxillary first molar occluded within 1 mm of the distal marginal ridge of the mandibular first molar and no tooth crowded out of the arch ( to avoid confusion in angle classification ) . an electronic digital vernier calliper with fine tips measuring within 0.01 mm ( mitutoyo corporation , kawasaki , japan ) is used in this study to measure the parameters on the maxillary and mandibular study models . these measurements are as follows : 
 maxillary intercanine width  between the cusp tips of maxillary caninesmaxillary intermolar width  between the mesiobuccal cusp tips of the first molarsmaxillary alveolar width  at the mucogingival junctions above the mesiobuccal cusp tips of the maxillary first molarsmandibular alveolar width  at the mucogingival junctions below the buccal grooves of the mandibular first molarsmandibular intermolar width  between the most gingival extensions of the buccal grooves on the first molars or , when the grooves had no distinct terminus on the buccal surface , between points on the grooves located at the middle of the buccal surfacesmandibular intercanine width  between the cusp tips of mandibular canines . maxillary intercanine width  between the cusp tips of maxillary canines maxillary intermolar width  between the mesiobuccal cusp tips of the first molars maxillary alveolar width  at the mucogingival junctions above the mesiobuccal cusp tips of the maxillary first molars mandibular alveolar width  at the mucogingival junctions below the buccal grooves of the mandibular first molars mandibular intermolar width  between the most gingival extensions of the buccal grooves on the first molars or , when the grooves had no distinct terminus on the buccal surface , between points on the grooves located at the middle of the buccal surfaces mandibular intercanine width  between the cusp tips of mandibular canines . mandibular arch widths are subtracted from maxillary arch widths to calculate the maxillary / mandibular arch width differences . all the data collected were tabulated according to groups and subjected to appropriate statistical analysis . statistical analysis is performed using the microsoft office excel 2007 and ibm spss version 22 software . the statistical methods employed in the present study are mean [ tables 15 ] , standard deviation [ tables 25 ] , analysis of variance ( anova ) [ tables 6 and 8 ] , and duncan 's multiple range test [ tables 68 ] sd ) in adult ci arch widths ( mean , sd ) in adult ciid1 arch widths ( mean , sd ) in adult ciid2 arch widths ( mean , sd ) in adult ciii comparison of arch widths in ciii , ciid2 , ciid1 malocclusion and ci normal occlusion ( genders pooled ) gender differences in arch widths between occlusion groups gender differences in maxillary minus mandibular arch width differences between occlusion groups all the data collected were tabulated according to groups and subjected to appropriate statistical analysis . statistical analysis is performed using the microsoft office excel 2007 and ibm spss version 22 software . the statistical methods employed in the present study are mean [ tables 15 ] , standard deviation [ tables 25 ] , analysis of variance ( anova ) [ tables 6 and 8 ] , and duncan 's multiple range test [ tables 68 ] . ages of subjects in years arch widths ( mean , sd ) in adult ci arch widths ( mean , sd ) in adult ciid1 arch widths ( mean , sd ) in adult ciid2 arch widths ( mean , sd ) in adult ciii comparison of arch widths in ciii , ciid2 , ciid1 malocclusion and ci normal occlusion ( genders pooled ) gender differences in arch widths between occlusion groups gender differences in maxillary minus mandibular arch width differences between occlusion groups with genders pooled , ciii and ci groups showed significantly larger maxillary intercanine widths than ciid1 group and larger maxillary intermolar and alveolar widths than ciid2 and ciid1 groups . gender dimorphism occurred in maxillary intermolar and alveolar width in ci occlusion and in maxillary intercanine width in ciid2 occlusion [ table 6 ] . with genders pooled , ciii group showed significantly larger mandibular intercanine , intermolar , and alveolar width than ci , ciid2 , and ciid1 groups . however , gender dimorphism can be seen in mandibular intermolar width in ciii , ci , and ciid2 occlusion and in mandibular alveolar width in ciii and ci occlusions [ table 6 ] . with genders pooled , ci group showed significantly larger mean intercanine width difference than ciii and ciid1 group and also , ciid2 and ciii showed significantly larger mean intermolar and alveolar width differences than ciid1 group . gender dimorphism did not occur in mean intercanine , intermolar and alveolar width difference [ table 6 ] . gender differences amongst maxillary and mandibular width and their differences are shown in tables 7 and 8 . with genders pooled , ciii and ci groups showed significantly larger maxillary intercanine widths than ciid1 group and larger maxillary intermolar and alveolar widths than ciid2 and ciid1 groups . gender dimorphism occurred in maxillary intermolar and alveolar width in ci occlusion and in maxillary intercanine width in ciid2 occlusion [ table 6 ] . with genders pooled , ciii group showed significantly larger mandibular intercanine , intermolar , and alveolar width than ci , ciid2 , and ciid1 groups . however , gender dimorphism can be seen in mandibular intermolar width in ciii , ci , and ciid2 occlusion and in mandibular alveolar width in ciii and ci occlusions [ table 6 ] . with genders pooled , ci group showed significantly larger mean intercanine width difference than ciii and ciid1 group and mean intermolar and alveolar width difference than ciid2 , ciii and ciid1 groups . also , ciid2 and ciii showed significantly larger mean intermolar and alveolar width differences than ciid1 group . gender dimorphism did not occur in mean intercanine , intermolar and alveolar width difference [ table 6 ] . gender differences amongst maxillary and mandibular width and their differences are shown in tables 7 and 8 . the size and shape of arches have considerable implications in orthodontic diagnosis and treatment planning , as it affects the space available , dental esthetics , and stability of the dentition . unfortunately , most studies investigated the transverse structure of the mandibular - maxillary base in ci and cii malocclusions . previous studies that compared arch widths in adult subjects having angle ci normal occlusions and ciii malocclusions have left unanswered questions . a statistical analysis based on data collected from previous arch width studies it was concluded that a sample size of approximately 20 subjects for each gender gave adequate power . however , for ciii subjects 34 samples could be obtained due to low prevalence rate . in this study , the null hypothesis for arch widths is rejected . the null hypothesis for maxillary / mandibular differences is rejected , except for mandibular intercanine widths and intercanine , intermolar and alveolar width difference . the null hypothesis for gender comparisons is rejected for maxillary intercanine and alveolar widths between ci and ciid1 , maxillary intermolar and alveolar width between c1 and ciid2 , mandibular intercanine , intermolar and alveolar widths between ciii and ciid1 [ table 7 ] and intercanine width difference [ table 8 ] in females . comparison of the results with already published studies shows agreement as well as conflict in some aspects . this disagreement among studies of comparison of arch widths in ci , cii , and ciii malocclusions may be explained by several factors : gender dimorphism , ethnic and racial differences , sample selection and size , and age of subjects . intercanine widths were investigated in a few of the previous studies , and conflicting results were found . in this study , with genders pooled , ci group showed significantly larger maxillary intercanine width than ciid1 group . this is in concurrence with studies by staley et al . and huth et al . , but differed from studies by sayin and turkkahraman and al - khateeb and abu alhaija . no difference is found in the maxillary intercanine width between the ci and ciii groups which is in concurrence with studies by kuntz et al . , al - khateeb and abu alhaija , uysal et al . although it differed from study of al - khateeb and abu alhaija , our study also showed that ciii group has significantly larger maxillary intercanine width than ciid1 group . this suggests that maxillary arches are narrower in intercanine region in ciid1 patients in indian population . in our study , it is in concurrence with studies staley et al . , huth et al . , sayin and turkkahraman , al - khateeb and abu alhaija , tollaro et al . and lux et al . , but differed from studies by frohlich and uysal et al . it is in concurrence with a study by huth et al . , but differed from a study by al - khateeb and abu alhaija . in this study , no difference is observed ciid1 and ciid2 group for maxillary intermolar width which differed from studies by huth et al . similarly , no difference is observed between ci and ciii groups for maxillary intermolar width in this study . this result is in concurrence with study by al - khateeb and abu alhaija , but differed from studies by chen et al . , kuntz et al . , uysal et al . , braun et al . , and slaj et al . this suggested maxillary arches are narrower in molar region in ciid1 and ciid2 malocclusions in indian population . clinicians have speculated that nasal obstruction , finger habits , tongue thrusting , low tongue position and abnormal swallowing , and sucking behavior were reasons for narrower maxillary dental arch widths in ciid1 malocclusions compared with a normal occlusion sample . to achieve ci molar relationship , expansion should be done in maxillary intermolar region in cii malocclusions . in this study , , huth et al . , uysal et al . , lux et al . , and alarashi et al . this suggested maxillary alveolar base is narrower in ciid1 malocclusions . in cases of crossbite , expansion of maxillary arch should be done to relieve posterior crossbite in ciid1 malocclusion . in this study , no difference is observed between ci , ciid1 , and ciid2 groups for mandibular intercanine , intermolar , and alveolar width . these results are is in concurrence with studies by staley et al . , and huth et al . ( mandibular alveolar width ) but differed from sayin and turkkahraman , uysal et al . , and walkow and peck ( mandibular intercanine width ) , by huth et al . , and uysal et al . however , ciii group showed significantly larger mandibular intercanine and intermolar width than ci , ciid1 , and ciid2 groups . these results are is in concurrence with studies by al - khateeb and abu alhaija , and uysal et al . ( mandibular intercanine width ) , by chen et al . , and kuntz et al . braun et al . concluded that the possible explanation for the increase in arch width seen in ciii dental arches may be the adaptability of the tongue to the decrease in available arch depth reflected in an increased lateral tongue dimension . it may be due to dental compensation , because mandibular posterior teeth were buccally inclined in ciii patients . staley et al . , and bishara et al . pointed out that it is clinically useful to compare differences between molar widths besides comparing absolute molar widths because on the basis of such differences , more consistent and interpretable results could be obtained . the ci group showed significantly larger mean intercanine and intermolar width difference than ciid1 and ciii groups . the mean intermolar width difference is positive for ci group and negative for ciid1 and ciii group . negative intermolar width differences suggested crossbite tendency in cii and ciii malocclusions . according to this study , the crossbite in ciid1 group is due to constricted maxillary with normal mandibular arch while in ciii group , it is due to normal maxillary arch with enlarged mandibular arch . according to some authors , it is the mesio - distal dimension of mandibular teeth which is responsible for such changes . sperry et al . reported that ciii patients often have wider lower teeth than ci and cii subjects . another possible explanation is that a shorter and larger mandibular arch in subjects with ciii could be a consequence of dental compensation in that patients with that malocclusion tend to have the mandibular incisors inclined to the lingual , and the lateral teeth inclined to the buccal . these findings occurred due to narrow maxillary arch in ciid1 malocclusion and wider mandibular arch in ciii malocclusion in molar region . the mean alveolar width difference is positive for ci , but negative for the ciid1 group . negative alveolar width difference in ciid1 patient occurred due to narrow maxillary alveolar width . in male subjects , in contrast , in female , although maxillary intercanine width is narrower in ciid1 group when compared with ci group , it is not statistically significant . similarly , in male subjects , ci normal occlusion showed significantly larger maxillary intermolar and alveolar widths than ciid2 malocclusion . however , although female subjects with ci normal occlusion showed larger maxillary intermolar and alveolar width than ciid2 malocclusion , it is not statistically significant . for mandibular arch widths , males showed significantly larger mandibular intercanine , intermolar and alveolar widths in ciii group than ciid1 group in contrast to female subjects where difference is not statistically significant . in male subjects , ci group showed significantly larger mean intercanine width difference than ciii and cii1 groups . in female subjects , no statistically significant difference is observed between the occlusion groups for mean intercanine width difference . these gender comparisons revealed that arch width differences between different types of malocclusions more pronounced in males than in females . males showed greater maxillary and mandibular intermolar and alveolar widths as compared to females in ci normal occlusion , greater maxillary intercanine and mandibular intermolar width as compared to females in ciid2 malocclusion and greater mandibular intermolar and alveolar widths as compared to females in ciii malocclusion . in male subjects , ci group showed significantly larger maxillary intercanine and alveolar width than ciid1 group . in contrast , in female , although maxillary intercanine width is narrower in ciid1 group when compared with ci group , it is not statistically significant . similarly , in male subjects , ci normal occlusion showed significantly larger maxillary intermolar and alveolar widths than ciid2 malocclusion . however , although female subjects with ci normal occlusion showed larger maxillary intermolar and alveolar width than ciid2 malocclusion , it is not statistically significant . for mandibular arch widths , males showed significantly larger mandibular intercanine , intermolar and alveolar widths in ciii group than ciid1 group in contrast to female subjects where difference is not statistically significant . in male subjects , ci group showed significantly larger mean intercanine width difference than ciii and cii1 groups . in female subjects , no statistically significant difference is observed between the occlusion groups for mean intercanine width difference . these gender comparisons revealed that arch width differences between different types of malocclusions more pronounced in males than in females . males showed greater maxillary and mandibular intermolar and alveolar widths as compared to females in ci normal occlusion , greater maxillary intercanine and mandibular intermolar width as compared to females in ciid2 malocclusion and greater mandibular intermolar and alveolar widths as compared to females in ciii malocclusion . ciid1 malocclusion showed the narrowest maxillary arch compared with the other types of malocclusionsciii malocclusion showed largest mandibular arch than other types of malocclusionsgender dimorphism is more commonly seen in ci normal occlusion than other types of malocclusions . gender dimorphism is not observed in ciid1 groupgender comparisons revealed , arch width differences between different types of malocclusions more pronounced in males than in femalesthe maxillary / mandibular intermolar width difference is positive for ci normal occlusion and negative for ciid1 , ciid2 , and ciii malocclusions , which suggested , the presence of crossbite tendency in cii and ciii malocclusions . ciid1 malocclusion showed the narrowest maxillary arch compared with the other types of malocclusions ciii malocclusion showed largest mandibular arch than other types of malocclusions gender dimorphism is more commonly seen in ci normal occlusion than other types of malocclusions . gender dimorphism is not observed in ciid1 group gender comparisons revealed , arch width differences between different types of malocclusions more pronounced in males than in females the maxillary / mandibular intermolar width difference is positive for ci normal occlusion and negative for ciid1 , ciid2 , and ciii malocclusions , which suggested , the presence of crossbite tendency in cii and ciii malocclusions .
objective : to test the hypothesis that there is no difference between class i ( ci ) normal occlusion , class ii division 1 ( ciid1 ) and cii division 2 ( ciid2 ) , and class iii ( ciii ) malocclusion with respect to arch widths , width of the maxillary and mandibular arches , gender dimorphism within groups , and gender comparisons.materials and methods : samples of 40 ci subjects , 40 ciid1 subjects , 40 ciid2 subjects , and 34 ciii subjects were studied . 
 all subjects were indians with no history of orthodontic treatment . 
 an analysis of variance and duncan 's test statistically compared the groups and genders.results:ciid1 malocclusion showed the narrowest maxillary arch compared with the other types of malocclusions . 
 ciii malocclusion showed largest mandibular arch than other types of malocclusions . 
 gender dimorphism is more commonly seen in ci normal occlusion than other types of malocclusions . 
 gender dimorphism is not observed in ciid1 group . 
 gender comparisons revealed arch width differences between different types of malocclusions more pronounced in males than in females . 
 the maxillary / mandibular intermolar width difference is positive for ci normal occlusion and negative for ciid1 , ciid2 , and ciii malocclusions , which suggested , the presence of crossbite tendency in cii and ciii malocclusions.conclusion:the hypothesis is rejected by the findings of this study .