This chapter addresses the question of whether children with molar incisor hypomineralization (MIH) are at greater risk for caries, have an increased need for treatment, or have a higher caries experience.

As already explained in detail, hypomineralized enamel is characterized by lower hardness, higher porosity, and higher protein content.¹ The lower strength may lead to posteruptive enamel breakdown soon after tooth eruption or at a later time due to the action of masticatory forces.² Such enamel breakdown, in turn, may promote plaque accumulation³ and subsequently promote the formation of a carious lesion.

In addition to this burden, the possible occurrence of hypersensitivity characterizes the clinical picture as a further key symptom. Affected molars can be highly sensitive to temperature and tactile stimuli. The reason for this is the porosity of the enamel, which leads to bacterial invasion and chronic pulp inflammation at an early stage.^4–6 This hypersensitivity can not only limit the consumption of cold and hot foods but also oral hygiene⁷ (Fig 16-1). Here, too, plaque accumulation is then promoted, which may subsequently lead to caries.

Fig 16-1 A 9-year-old patient with a severely hypersensitive and carious lower right MIH molar. The tooth was restored with a stainless steel crown. a) Clinical appearance before cleaning the tooth: heavy plaque accumulation and food debris are visible. b) Clinical appearance after careful cleaning of the tooth under local anesthesia: the posteruptive enamel breakdown and the carious lesion become visible. c) Situation after caries excavation, preparation, and placement of the stainless steel crown. d) After 1 month: no plaque accumulation is visible on tooth 46. The patient reports that the pain symptoms have disappeared and brushing teeth in the region is now easier.

16.1 Caries

According to our current understanding, caries is a disease caused by sugar consumption⁸ but influenced by multiple factors. Whether and how quickly caries develops depends on the complex interaction of the various pathogenic and protective factors involved. The frequent intake of low molecular weight carbohydrates leads to pathological changes in the oral microflora, favoring acidogenic and aciduric species.⁹ Consumption also causes potentially cariogenic bacteria such as Streptococcus mutans to produce organic acids in the dental biofilm, which induce demineralization of tooth hard tissues. On the protective side, both the host defense and the patient’s oral hygiene have an effect. They limit the growth and metabolic activity of the oral biofilm and its acid production. In addition, saliva, with its buffering properties and mineral content, promotes remineralization of the dental hard tissues. The remineralizing effect of saliva can be increased by an external supply of fluorides. In addition to these local and direct acting factors, other behavioral and socioeconomic factors are associated with dental caries.¹⁰

16.2 Caries experience in children with MIH

Studies have shown that children diagnosed with MIH have a higher caries prevalence than healthy children. This applies to populations with a high caries experience as well as to those with a low one.^11–13 Compared to children without MIH, the permanent teeth of MIH-affected patients are 2 to 6.6 times more likely to be affected by caries.^14–16

The caries index, measured with the DMF-T index, is also (usually significantly) increased.¹⁷ If only the first molars are evaluated using this index, MIH patients also have more teeth and tooth surfaces with a DMF index > 0 compared with healthy patients.

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