Using Chi squared test is correct for qualitative data. In case dental caries is as dependent variable, and you may dichotomized it such as (having caries - not having caries), or categorized it like (low caries- moderate caries-high caries) you can use chi2 test. But if data for dental caries is mean number of decayed teeth, you have a quantitative variable, so you can not use chi2 test and you may use t-test or ANOVA. The latter tests are preferable to analyse dental caries.

Zahra Saied-Moallemi given good explanation for Chi squared test