Morphological characteristics of dental arch in untreated adult mandibular incisor crowding

MA Shu-fang; CAO Jun

Abstract：AIM:To investigate the effect of mandibular incisor crowding on arch form and mandible development.METHODS:Models of 114 untreated adult subjects(62 men,19.7 years of average age and 52 women,20.5 years of average age)without skeletal malocclusion and with varying degrees of incisor crowding were studied.The control group was composed of 137 mandibular models of ndividuals with normal occlusion(79 men,19.8 years of average age and 58 women,20.0 years of average age).Incisor crowding was quantified by using Little's irregularity index(LII).The following variables were measured to an accuracy of 0.1 mm:mandibular intercanine width(ICW),mandibular interfirst premolar width(IFPW),mandibular intermolar width(IMW),mandibular anterior arch length(La),mandibular arch length(Lb)and LII.RESULTS:①There were statistically significant(P<0.05)differences between the sexes for the variables measured(La,Lb,ICW,IMW).②In the meu,all variations of incisor crowding group were less than those of control group(P<0.05).In the women.there was no statistically significant difference(P>0.05)in Lb between the two groups and other variables of incisor crowding group were smaller(P<0.05).③LII wag negativly correlated with IFPW in men(r=-0.408,P=0.001),and LII was negatively correlated with ICW(r=-0.362,P=0.008)and IMW(r=-0.398,P=0.003)in women.CONCLUSION:Incisor crowding may contribute to decreased dental arch length and narrowed dental arch width.It suggested that we should take early interventions to prevent the deficiency of dental arch length and width which might occur in the end of mandibular growth and development.