Perceptions of dental professionals and laypeople to altered maxillary incisor crowding

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The aim of this study was to determine how sensitive dental specialists and laypeople are to maxillary incisor crowding when viewed from the front. Computer technology was used to create a series of photographs of the incisors of a smiling woman viewed from the front. The photographs showed varying degrees of maxillary incisor crowding classified according to Little's irregularity index (LII). The incisors illustrated in the photos were ranked on a scale from perfect alignment to severely crowded. The rating was done by 4 groups of people: orthodontists, general dentists, laypeople with experience of orthodontic treatment, and laypeople with no history of orthodontic treatment. The orthodontists and the general dentists noted misalignment of 1 central incisor when the LII reached 1.5mm, whereas the laypeople with or without experience of orthodontic treatment were sensitive to 2.0mm of crowding. When the LII reached 2.0mm for 1 lateral incisor, it triggered the orthodontists to consider providing orthodontic treatment, whereas this degree of irregularity was ignored by the general dentists and laypeople. When both central incisors were misaligned, the orthodontists were sensitive to the fact at 2.0mm of LII, whereas the general dentists and the laypeople with experience of orthodontic treatment became sensitive at 3.0mm of LII, and the laypeople with no history of orthodontic treatment were sensitive at 4.0mm of LII. When both lateral incisors were misaligned, the orthodontists noted the crowding at an LII of 3.0mm, the general dentists became sensitive at an LII of 4.0mm, whereas both the laypeople with experience of orthodontic treatment and the laypeople with no history of orthodontic treatment ignored it. When the crowding of all maxillary incisors reached an LII of 4mm, both the orthodontists and the general dentists were alerted to the fact, but both the laypeople with experience of orthodontic treatment and the laypeople with no history of orthodontic treatment were sensitive only to a total incisor crowding equal to an LII of 6.0mm. Orthodontists are more critical than other groups when evaluating the misalignment of the maxillary incisors. It appears that the central incisors play a more important role than do the lateral incisors when dental crowding impacts smile esthetics. For all observer groups, it also appears that people are more sensitive to the misalignment of a single tooth than they are to the same level of crowding distributed over multiple teeth.