As described in the previous chapter, MIH teeth must also be included into a prophylaxis concept. Pit and fissure sealants are a microinvasive preventive measure to avoid the development of caries or to arrest carious lesions without cavities.1 They act as a physical barrier to decay. On the one hand, they prevent bacteria from entering the fissure and on the other hand, remaining bacteria are cut off from their carbohydrate substrate by the sealing, so that they die. Substantial cariogenic activity is not expected from these sealed bacteria.² Furthermore, a surface that is difficult to clean is converted into one that can be cleaned.

The clinical efficacy of fissure sealants has been confirmed in numerous studies. A comprehensive systematic review showed that fissure sealing with resin-based sealants leads to an 11–51% reduction in caries.³

An important parameter for the success of a fissure sealant is the retention of the sealant. The effectiveness is reduced or lost if the marginal seal between the tooth and the sealing material is not given.^4,5 For non-structurally compromised molars, there are well-formulated or evaluated application protocols and material recommendations in this regard.

However, the question arises as to whether molars exhibiting hypomineralization can also be sealed and what the chances of success of this treatment are. Retention losses observed in clinical practice raised doubts about the effectiveness for some time. Kotsanos et al⁶ were able to show that MIH molars required retreatment approximately 2 years earlier and the risk of loss was approximately three times higher compared with sound teeth using classical treatment protocols.

The problem is due to the characteristics of hypomineralized enamel, described in Chapter 3, which is characterized by less dense prismatic structures, porosities, and a lower mineral content, which correlates with reduced strength and hardness.^7–9 These dispositions explain the risk of failure in restorative therapy and the more rapid caries development. MIH molars generally require therapy about ten times more frequently than healthy molars.¹⁰

The indications for fissure sealants of hypomineralized molars, as well as the available materials, the clinical procedure, and the prospects of success are explained in more detail next.

11.1 Indications

Early diagnosis in combination with assessment of the severity of MIH, as well as the age and compliance of the patient are essential for the selection of the correct time of treatment. Fissure sealings can generally be performed on hypomineralized molars if they do not show posteruptive enamel breakdowns on the occlusal surface and are not cariously cavitated¹¹ (Fig 11-1).

Fig 11-1 Sealing recommendations within the therapy plan of the Würzburg concept (after Bekes et al¹¹; courtesy of DGKiZ). a) Low caries risk. b) High caries risk.

The localization of the opacity and its extension, as well as the degree of the porosity, recognizable by the type of discoloration, play a minor role. However, it is understandable that molars with milder forms of MIH and smaller hypomineralized areas offer better conditions for the durability of a sealant than extensively malstructured molars or darker opacities.

11.2 Materials

A large number of materials are available for sealing, primarily low-viscosity methacrylate-based sealants used in conjunction with acid conditioning. For teeth that are in the process of eruption or where adequate moisture control is not possible, glass-ionomer cements can be used as an alternative. In MIH in particular, this class of material must be used again and again, as the pain symptoms often necessitate early action.

Figures 11-2 to 11-4 show the sealed MIH molars in different intraoral situations and with different materials.

Fig 11-2 Fissure sealing of an MIH molar with a resin-based sealer. a) Before sealing. b) After sealing.

Fig 11-3 Fissure sealing of an MIH molar with a glass-ionomer cement. a) Before sealing. b) After sealing.

Fig 11-4 Extensive fissure sealing of an MIH molar with glass-ionomer cement. The tooth has not yet erupted completely and already exhibits hypersensitivity. Oral hygiene is difficult. a) Before sealing. b) After sealing.

11.3 Clinical procedure

11.3.1 Isolation

General aspects

Drying can be performed using cotton rolls or using a rubber dam. It is evident that the retention rates of sealants placed in absolute isolation or under relative contamination control using the four-hand technique do not differ significantly in non-structurally damaged molars.¹²

Special features of MIH teeth

Since sealing is also frequently carried out in MIH molars at a time when the occlusal surface is fully visible but the gingiva has not yet retracted significantly below the dental equator, a rubber dam clamp usually cannot be positioned without causing pain. Since it is necessary to preserve the child’s cooperation, relative isolation will therefore be the approach of choice in the majority of cases.

11.3.2 Cleaning

The tooth surface must be thoroughly cleaned to remove adhering plaque and debris as much as possible before application of the fissure sealant. Cleaning can be accomplished in various ways: with a rotating brush and pumice, with a rotating brush without any paste, or with air polishing or air abrasion.¹² The use of a brush with or without a paste can be regarded as a routine procedure due to its simple, fast, and child-friendly handling.^13–15

11.3.3 Etching of the enamel surface

General aspects

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