# The Pathology of the First Permanent Molar during the Mixed Dentition Stage--Review
## 3 Results and Discussion
### Pathology of the Dental Hard Tissues
#### 3.2.1 Molar Incisor Hypomineralization
The burden of MIH was driven by the country-specific demographics: heavily populated countries like India, China, and the United States significantly contributed to the number of prevalent cases, while growing countries like India, Pakistan, and Indonesia ranked first with respect to the number of incident cases. The authors determined that 27.4% of the cases were or will be in need of therapy due to MIH pathology [83]. Many researchers highlighted the high prevalence of dental caries and high caries scores (decayed, missing, and filled primary teeth--dmft and Decayed, Missing, and Filled permanent Teeth--DMFT) in association with MIH. [PERSON] et al., 2013, investigating 152 Iraqi, 7 to 9-year-old children diagnosed with molar hypomineralization (MH), found statistically significantly higher caries mean scores for both primary and permanent teeth in the MH-affected group than in control one (dmft 4.82 \(\pm\) 2.73 vs. 3.36 \(\pm\) 2.30 and DMFT 2.79 \(\pm\) 1.39 vs. 1.28 \(\pm\) 1.39) [84]. In a 2017 systematic review, a significant correlation between MIH and dental caries was found, with both DMF index and caries prevalence being higher in MIH-affected children than in non-affected ones [85]. In a 2017 case-control study on a pediatric sample, 9.63 \(\pm\) 1.29 years, a large difference was noticed between MIH cases and controls in what concerns DMFT score (more than six times higher in MIH cases than in controls), given that dmft score was similar for the two groups [86]. Since the latter indicated that the patients were exposed to the same caries risk factors, it follows that the high caries prevalence in the permanent teeth was the consequence of the presence of MIH lesions [86]. Further investigating only the FPMs of MIH cases, the same authors noticed that MIH-affected FPMs presented a higher number of dentine carious lesions than the non-affected ones [86]. In another case-control study, [PERSON] et al., 2002, showed that by the age of nine, children diagnosed with severe MIH had undergone dental treatment of their FPMs ten times more frequently than the unaffected controls, and on average, each affected tooth had been treated twice [69]. The management of MIH-affected children is a real challenge for the pediatric dentist. Enamel hypomineralization is a dynamic defect [84]; therefore, treatment should intercept it. It is recommended that children with poor general health in the first four years of life be considered at risk for MIH and to be monitored more frequently during eruption of FPMs [45]. The therapeutic approach should be oriented toward controlling post-eruptive enamel breakdown, dental caries, and associated symptoms like sensitivity and pain and improving the long-term prognosis of the affected teeth [45]. In cases of enamel breakdown, \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Study**} & \multirow{2}{*}{**Year**} & \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**Prevalence of** **MH**} & \multirow{2}{*}{**Gender** **Distribution**} & \multicolumn{2}{c}{**Degree of Severity of Affected Molars**} \\ \cline{5-7}  & & & & **MHF** & & **Middle** & **Moderate** & **Severe** \\ \hline [PERSON] et al. [79] & 2020 & 659 & 176 & F-96 (54.55\%) & 74.45\% & 23.04\% & 2.51\% \\  & & & (26.7\%) & M-80 (45.45\%) & & \\ \hline [PERSON] et al. [80] & 2020 & 5318 & 216 & F-96 & 361 & 103 & 210 \\  & & & (4.1\%) & M-120 & (53.9\%) & (15.3\%) & (31.2\%) \\ \hline [PERSON] et al. [81] & 2020 & 407 & 99 & F-26 (44.1\%) & & \\  & & & (14.5\%) & M-33 (55.9\%) & 68.75\% & - & 31.25\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._severe restorative problems arise [45]. The margins of the restoration should be placed in sound enamel, and it is very difficult to find where the boundary between hypomineralized and sound enamel is [45]. Taking into consideration the altered prismatic morphology in the hypomineralized enamel, the bonding to it is unachievable [69]. Therefore, failure of direct restorations and continuing breakdown of the enamel occurs [69].