# 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
[PERSON] et al., 1996, first suggested that prolonged breastfeeding can generate enamel mineralization defects, possibly because of environmental contaminants such as dioxin and dioxin-like compounds that hamper amelogenesis [57; 58]. There are also researchers who found no correlations between the duration of breastfeeding and the presence of enamel defects [49; 59]. [PERSON] et al., 2008, showed no statistically significant correlation between the exposure of the child to dioxins via mother's milk and the occurrence of MIH lesions [60]. Furthermore, [PERSON] et al., 2020, reported a high prevalence of MIH in cases of early weaning, showing that the nutritional status of the child is compromised in this situation, with unfavorable consequences on enamel development [56]. Scientific evidence shows a strong link between many medical conditions in the first years of life and MIH. Respiratory diseases such as pneumonia, lung and airway infections, and asthma can generate metabolic disturbances with further impact on dental hard tissues [56]. These conditions trigger the phenomenon of hypoventilation that favors tissue acidosis [56]. As a result of the pH changes in the enamel matrix, an inhibition of proteolytic enzymes and of hydroxyapatite crystals development occurs, ultimately leading to the hypomineralization of dental hard tissues [56]. [PERSON] et al., in their study (2020), found a strong correlation between MIH with postnatal acute ailments like unexplained fever and chest infections other than pneumonia and pneumonia [56]. [PERSON] et al., 2012, showed that chicken px, renal failure, asthma, and allergic reactions were more common in children with MIH than in controls [61]. In another study, the prevalence of MIH was positively correlated with asthma, adenoid infections, tonsillitis, and fever in the first four years of life [62]. A positive correlation between the prevalence of MIH and otitis in the first three years of life and atopic dermatitis was demonstrated by [PERSON] et al., 2022 [63]. Upper respiratory infections and their complications, such as otitis media, bronchitis, bronchiolitis, laryngitis, tonsillitis, repeated episodes of high fever due to common cold/coryza, neonatal illness, and viral gastroenteritis were the most commonly encountered conditions by [PERSON] et al., 2008, in the postnatal period [54]. The correlation between MIH and viral gastroenteritis is explained by the hypocalcemia the disease generates in infants [54]. The latter authors identified more than one medical condition in MIH subjects [54]. Significant correlations between MIH and both chickenpx and measles before the age of four were found by [PERSON] et al., 2013 [49]. The same authors also reported pneumonia and gastrointestinal diseases to be associated with MIH lesions [49]. [PERSON] et al., 2022, found a positive association between genetic syndromes and MIH [55]. Correlations between prolonged use of corticosteroids and antibiotics due to respiratory or urinary tract problems and MIH were reported by [PERSON] et al., 2008 [54]. Antibiotic intake during the second year of life was also found to be positively correlated with MIH lesions in the study by [PERSON] et al., 2022 [55]. The role of antibiotics in MIH occurrence is still controversial because it is not possible to establish if the childhood illness itself or the medication intake is the causative factor or if both are responsible [51]. MIH etiology is subject to controversy, and no consensus exists in the scientific literature. [PERSON] et al., 2019 and [PERSON] et al. 2021, by their systematic reviews and meta-analyses, emphasized on the multifactorial etiology of MIH [64; 65]. MIH Diagnosis  
Hypomineralization is a qualitative defect that is clinically identified as a disturbance in the enamel translucency (opacity) [42; 43]. It is characterized by the presence of creamy-white, yellow, or brown enamel opacities, which have distinct margins with the adjacent normal enamel, hence the name \"demarcated opacities\" [42].