Diagnostic capability of Little irregularity index to estimate arch length discrepancy

Abstract

In 1975 Little proposed the irregularity index as valid and reliable method for assessing lower incisor alignment, although it was formulated for use in lower arch it has also been applied to upper arch. Recently Bernabe and Flores reintroduced the index for registration of crowding in whole dental arch for epidemiological surveys and their work based on offering cut-off points to estimate negative ALD. However, they strongly recommended further studies to test the reliability of this approach in field setting. The aim of the study was to reevaluate the potentiality of LII to be used in epidemiological survey as a valid and less consuming measurement of crowding compared with ALD. 500 dental casts with full permanent dentition excluding third molars, the selection criteria were children ranged 12-16 years, permanent dentition completely erupted, no previous orthodontic treatment, dental caries, restorations, proximal attrition or tooth anomaly. The casts were categorized according to age, sex and severity of crowding. In order to categorize casts according to amount of crowding ALD was calculated as the difference between available and required space difference in dental arch anterior to the first permanent molars. After the categorization process was finished incisal irregularity of the casts was measured using LII.