The relationship between irregularity of the incisor teeth, plaque, and gingivitis: a study in a group of schoolchildren aged 11-14 years.

The relationship between irregularity of teeth and periodontal disease was investigated in 201 children aged 11-14 years. The upper and lower incisor teeth were assessed for spacing, labio-lingual displacement, and mesiodistal overlap at each of the six contact areas. Plaque and gingivitis were assessed at six sites on each of the four upper and four lower incisor teeth. There was evidence for a direct relationship between the number of contact areas with tooth displacement combined with overlap and the number of sites with gingival redness (R = 0.25, P < 0.001), bleeding (R = 0.18, P < 0.01), and profuse bleeding (R = 0.25, P < 0.001). There was no evidence for a relationship between labio-lingual displacement alone and gingivitis. One-hundred-and-twenty-eight subjects without tooth displacement combined with incisor overlap had, respectively, 34, 15, and 35 per cent fewer sites with redness (P < 0.01), bleeding (P < 0.05), or profuse bleeding (P < 0.01) than the 73 subjects with overlap. The statistical significance of these differences was unaffected by covariate adjustment to take account of the effect on gingivitis of variation in the number of sites with plaque. There was no evidence of a relationship between incisor overlap and amount of plaque in these subjects. The results indicate that overlapping of incisor teeth is directly related to gingivitis and this relationship cannot be explained simply by an effect on oral hygiene.