The Correlation Between Occlusal Plaque and Dental Caries in Schoolchildren

For the purpose of studying the correlation between the amount of occlusal plaque and the prevalence of dental caries, 829 school-children of Aji Island and Ichinoseki aged 6 to 15 years were examined. The occlusal surfaces of their permanent premolar and molar teeth which had erupted completely and were not decayed nor filled were scored 0 to 3 according to the extent of the area covered with dental plaque. The criteria of scoring were as follows:Score 0-No clinical plaque. Linear staining only of the contents of pits and fissures.1-Less than one-third of the occlual surface covered with stained palaque.2-Less than two-thirds of the occlusal surface covered with stained plaque.3-More than two-thirds of the occlusal surface covered with stained plaque.The mean score per kind of tooth in one individual was called the individual Occlusal Plaque Index (O.P.I.), and the mean of the individual values was called the population O.P.I. of each kind of tooth. The O.P.I. was calculated for the following kinds of teeth; first molars, the second molars, whole molars, premolars, and premolar-and-molars.The values of all kinds of population O.P.I. were already high immediately after complete eruption and declined with age for some years. While the declination was slight in the first molars, it was very marked in premolars. The means of molar O.P.I. were constantly higher in females, but the means of premolars were not so.The coefficients of correlation between the various O.P.I. 's and the numbers of DMFT and DMFS were calculated and investigated statistically. All the correlations seemed to be basically a positive relationship, and statistically significant correlations were frequently found in the several kinds of O.P.I. except for the period just after eruption. High significant correlations were very often present in the O.P.I. of molars but were rarely present in the premolars. The highest coefficients were obtained between the number of DMFS and the O.P.I. of the first molars and whole molars in the 5th and 6th grade elementary schoolchildren because almost all of the children with a high value of the O.P.I. had suffered from more carious lesions than average.From these findings it was concluded that the O.P.I. of the permanent first molars and whole molars had a highly significant correlation with the prevalence of dental caries in schoolchildren.