Severity and extent of hypomineralised defects located on working and balancing cusps: a comparative study between primary and permanent teeth.

Objective: To assess whether defects related to Molar Incisor Hypomineralisation (MIH) and Hypomineralised Second Primary Molar (HSPM), located on working cusps, exhibit greater extent and severity than those on balancing cusps.

Materials and methods: A total of 605 children aged 6 to 12 years were evaluated, of whom 110 presented with MIH/HSPM, comprising 268 molars (65 primary and 203 permanent). The molars were divided into two groups based on defect location: G1 (n = 170) with defects on working cusps, and G2 (n = 98) with defects on balancing cusps. Comparative assessments of defect location, extent, and severity were performed using Chi-square and Mann-Whitney tests, with a significance level of 5%.

Results: In the overall sample, including both primary and permanent molars, no statistically significant differences were observed between G1 and G2 regarding extent (p = 0.15) or severity (p = 0.46). However, in primary molars only, significant differences were found for extent (p = 0.008), with greater lesion extension on working cusps, while severity showed no significant difference (p = 0.568).

Conclusion: Hypomineralisation-related defects located on working cusps of primary molars exhibited greater extent than those on balancing cusps.