Analysis of the point-counting and planimetric methods in the quantification of the biofilm of dentures: a study of methodological validation

Dois métodos de quantificação de biofilme da dentadura (contagem de pontos e planímetro) foram testados e comparados com o método de pesagem de papel e Índice de Higiene de Prótese. Superfícies internas de 62 próteses foram coradas, fotografadas e as áreas total e do biofilme foram projetadas em papel e contornadas com grafite. O método de contagem de pontos (experimental 1) foi aplicado com uma grade de pontos. Para o método do planímetro (experimental 2), as áreas foram medidas com um planímetro digital e para o método de pesagem (controle 1) foram recortadas e pesadas em balança de precisão. No Índice de Higiene de Prótese (controle 2), utilizou-se a atribuição de escores. Os resultados mostraram uma porcentagem de concordância entre os métodos experimentais e controle 1 de 82% (contagem de pontos) e 95% (planímetro), bem como alto grau de correlação (r = 0,98; r = 0,99) entre os valores obtidos. Quando comparados com o controle 2, houve concordância em 55% (contagem de pontos) e 37% (planímetro) dos casos. Os métodos experimentais podem ser úteis em estudos clínicos para avaliação da eficácia de agentes de higienização. Two methods of quantification of the biofilm (point-counting and planimetric) were tested and compared with the paper-weighing method and with the Prosthesis Hygiene Index. The internal surfaces of 62 complete dentures were stained and photographed. The slides were projected on a paper sheet. The total area and the area covered with biofilm were contoured using a black pencil. The point-counting method (experimental 1) was carried out on a mesh of equidistant points. For the planimetric method (experimental 2), the areas of interest were measured by means of a digital planimeter. In the paper-weighing method (control 1) the areas of interest were cut and weighed on a precision scale. In the determination of the Prosthesis Hygiene Index (control 2), the accumulation of biofilm was estimated by means of a scoring method. The results revealed an agreement rate of 82% between the paper-weighing method and the point-counting method, and an agreement rate of 95% between the former and the planimetric method, which was confirmed by high coefficients of correlation (0.98 and 0.99, respectively). The comparison with the Prosthesis Hygiene Index resulted in 55% of agreement with the point-counting method and in 37% of agreement with the planimetric method. The experimental methods can be useful in clinical studies involving the evaluation of the performance of denture cleansers.