Objective: The aim of the present study is to evaluate the
diagnostic capability of Little irregularity index (LII) to estimate
arch length deficiency (ALD) in a dental arch.
Material and methods: Five hundred dental casts were
selected from 1000 study models from the patients (12-14 years
old) attending the Dental Clinic of Orthodontic, in Tanta
University. The casts were categorized according to sex, degree of
crowding and upper or lower. In order to classify cases according
to degree of crowding ALD was calculated as the difference
between available and required space in each dental arch anterior
to the first permanent molars. LII was calculated on each cast by
measuring the linear displacement between the six anterior teeth,
and was contrasted with the dichotomized ALD. The receiver
operator characteristic curve (ROC) was applied to suggest optimal
cut-off points for LII to estimate ALD.
Results: High correlation was observed between ALD and LII
(-0.91, P<0.0001). According to ROC curve, LII of >0, >3.5, >6mm
were optimized cut-off points to estimate minimum, moderate
and severe crowding respectively. Regarding the analysis of ROC curve for minimum crowding cases, LII was found to have the
highest diagnostic capability of >0mm or minimum crowding with
sensitivity 1.00 and specificity 1.00, then the moderate crowding
with sensitivity 96.45 and specificity 97.96 and severe crowding
with of sensitivity 91.95 and specificity 84.05.
Conclusion: The results of ROC provided useful insights of the
potentiality of LII to estimate negative ALD of the dental arch.