Dear Drs,

Thank you for your compliments regarding the article on the standardised studies on molar incisor hypomineralisation (MIH) and hypomineralised second primary molars (HSPM). In the article we mention the age of 5 years as an optimal age mainly due to the ability of young children to cooperate with an accurate examination, but examination of younger children is not excluded by any means. The optimal age for diagnosing HSPM depends on several factors: presence of the molars, cooperation of the child with oral examination and caries prevalence. In countries with low caries prevalence, the age of 5 years seems to be an optimal age because in many cases the children can cooperate well with the oral examination. We agree with your opinion that when examining 5-year-olds, you will notice more post-eruptive enamel loss, atypical caries, atypical restorations and atypical extractions, so the researcher needs to be aware of the more difficult to diagnose characteristics of HSPM. A younger age group can be examined, but the issue of higher drop-out because of the cooperation needs to be taken into consideration, as does its influence on the representative nature of the subsequent sample.