Molar-incisor hypomineralization (MIH) is defined as enamel developmental defects in one or more first permanent molars and may include permanent incisors.1 An estimated 14.2% of the world's population has molar-incisor hypomineralization (MIH).2 MIH reveals a multifactorial etiology model, with Perinatal and postnatal etiological factors being the most likely.3 The evidence indicates the effect of systemic factors at different stages of tooth development on the formation of lesions. The enamel formation of the first permanent molar begins between 28 weeks of gestation and the first 10 days after birth. Since ameloblasts are one of the most sensitive cells, any minor environmental change can lead to temporary or permanent damage and result in hypoplasia (damage to the enamel matrix formation) or hypomineralization (damage in the calcification or maturation stage). The probable risk factors include the type of delivery and associated problems, fever, mother or child hypoxia, respiratory infections, low birth weight, and electrolyte imbalance in premature infants, metabolic disorders of calcium and phosphorus, recurrent infection episodes in the first three years of life, and using antibiotics as well as a combination of several etiological factors that synergy each other.4,5 However, geographical differences in MIH prevalence and the uncertainty of the exact reason for the lesions suggest the role of genetics in its etiology.3,6

Clinically, MIH brings many problems for the child and the dentist. Affected children at 9 years (after the first permanent molars erupt) need ten times more dental treatment than other children. Because children avoid brushing sensitive molars. The hypomineralized areas of these teeth break down in the posterior region under pressure, and caries progress rapidly. In incisors, these lesions appear milder than in the molars, and due to the lack of masticatory forces, their demineralized enamel does not disintegrate after the eruption. MIH generally requires extensive treatments, from extensive restorations, endodontics, and veneers to molar teeth extraction. Lack of proper anesthesia is another problem in dentistry.1

Oral conditions, such as oral diseases or oral health significantly affect the quality of life,7,8 which can significantly affect individuals' psychological and social aspects. The adverse effects of poor tooth appearance are significant, especially in children.9,10

OHRQoL includes a set of indicators that determine the effect of oral and dental conditions on a person's life.11 These indicators measure oral health, well-being, the level of expectations and satisfaction with the received dental care, and self-concept in the individual.12 Studies show that low socio-economic status, orthodontic and periodontal problems, dental caries, and fluorosis are all associated with decreased OHRQoL.13,14

In a study of children aged 7-16, the dental aesthetic perception was shown to be associated with changes in OHRQoL.10 Various studies have shown that MIH negatively affects the quality of life and OHRQoL, which is more obvious in moderate and severe cases.15,16 These effects were significantly severe in children at the beginning of the mixed dentition period (8 years old).17 A study of 129 children aged 8-12 with MIH showed evidence of decreased OHRQoL.18 In addition, some children show their anterior teeth with white to yellowish-brown spots that can create a negative image of themselves and disrupt their social interaction. These patients usually have problems with school and socializing with other children,19 so early detection of this defect may prevent the severity of the lesion and reduce its effect on OHRQoL.

Some studies revealed that MIH does not affect OHRQoL.20, 21, 22 while some others showed that suffering from MIH leads to decreased OHRQoL.15,17,23 As a result, there is conflicting evidence about the effect of MIH on OHRQoL in children. Therefore, this meta-analysis study evaluated the effect of MIH on OHRQoL in children aged 8-10.