As sealants are usually placed in erupted (pre)molars, the level of caries experience of the child in their primary dentition is a good predictor of carious lesion development in pits and fissures of permanent molars (Disney et al. 1992). But being a high-caries risk child is not enough of a reason to place a sealant according to cost-effective principles. Also the caries risk at the tooth surface level should be established. Pits and fissure morphology (medium and deep) in combination with or without signs of carious lesion activity (presence of biofilm, roughness and/or whitish colour of the surface) are factors that determine the state of carious lesion in pits and fissures (see Chaps. 9, 11, 16, 19).

Sealing aims to modify patent pits and fissures into smooth surfaces that are protected from bacterial colonisation and exposure to fermentable substrates and that can be cleaned easily. The strategy is effective not only as a preventive measure but also in arresting non-cavitated enamel carious lesions in pits and fissures (Griffin et al. 2008). The superiority of pit and fissure sealants over fluoride varnish application in the prevention of occlusal carious lesions has been reported (Hiiri et al. 2010).

Glass-ionomers are more hydrophilic than are resin-based materials. It is therefore logical to assume that a glass-ionomer rather than a resin-based material should be used in sealing carious lesion-prone pits and fissures that cannot be kept absolutely moisture-free, such as in just erupting molars and in children with behaviour problems.

Resin-based materials, auto- and light-cured, have a long tradition of use as a material for sealing pits and fissures. Controversy exists about whether a resin sealant needs to be applied under rubber dam or under cotton wool roll isolation. If the latter method is used, the dentist has to ensure that the tooth surface will not be contaminated with saliva and kept moisture-free after washing the etch gel away. Four-handed dentistry might then be a necessity. Etching and light-curing time differs from one product to the other and it is therefore important to read the manufacturers’ instructions. When using light-cured resin sealant material, the dentist has to realise that the material can shrink by up to 4% and that unpolymerised sealant, containing Bisphenol A (BPA) and/or BPA-DM, is left at the surface layer. This layer can easily be removed when adjusting the bite or through wiping the surface with a cotton pellet.

One of the guiding principles of MID is that biomimetic dental material is used. As the toxic BPA and BPA derivates are released from dental resins (Fleisch et al. 2010; Kingman et al. 2012), this material needs to be adapted. These substances have been linked to a number of biological disorders (Eng et al. 2013; Jedeon et al. 2013; Yeo et al. 2013). This development has led the World Dental Federation (FDI 2013) to issue a policy statement on BPA, in which it discourages BPA use in the manufacturing of dental materials.

ART sealants use a high-viscosity glass-ionomer, which is placed over carious lesion-prone pits and fissures under finger pressure. Hand instruments (such as an excavator and an applier/carver) are used for adjusting the bite and removing excess glass-ionomer material. In applying this approach, sealants can be placed in situations independent of the need for rotary instruments and thus electricity and running water.

In the literature, effectiveness is often expressed as the survival of fully and partially retained sealants and as the survival of cavitated dentine carious lesion-free tooth surface.

We know that sealants deteriorate over time. The rate of sealant deterioration varies from brand to brand but is on average higher among the group of glass-ionomer- than resin-based materials (Kühnisch et al. 2012). Among the glass-ionomers, retention of the high-viscosity type, particularly when applied under finger pressure as part of the ART approach, is on average higher than for the medium-viscosity type (van ’t Hof MA et al. 2006). Encapsulated high-viscosity glass-ionomers (HVGIC) show higher mechanical strengths values than the hand-mix version (Dowling and Fleming 2009).

Despite the early exposure of parts of pits and fissures to the oral environment, the failure rate, expressed as the development of a cavitated dentine carious lesion, is not higher in glass-ionomer-based than in resin-based sealants (Beiruti et al. 2006a; Yengopal et al. 2009; Ahovuo-Saloranta et al. 2013). This phenomenon led Frencken and Holmgren (1999) to state that sealant retention should be considered only a surrogate endpoint of sealant effectiveness. The true endpoint is the absence of a cavitated dentine carious lesion in pits and fissures.

As most long-term comparisons between the effectiveness of glass-ionomer-based materials and resin composite sealants over the last decade have used HVGIC applied according to the ART approach, it is of interest to analyse the outcomes of these comparisons. A total of five research articles could be retrieved. These covered studies of 2–5 years long carried out between 2006 and 2015 in Brazil, China and Syria, using the hand-mixed high-viscosity glass-ionomers Fuji IX (GC, Tokyo, Japan), Ketac Molar (3M ESPE, Seefeld, Germany) and Ketac Molar Easymix (3M ESPE, Seefeld, Germany) and the light-cured resin sealants Clinpro (3M ESPE, Seefeld, Germany), Delton (3M, St Pauls, USA), Fluoroshield (Dentsply, York, USA) and Helioseal (Ivoclar, Schaan, Liechtenstein).

Of the five studies, one showed a significantly higher cavitated dentine carious lesion-preventing effect in occlusal surfaces for ART/HVGIC than for resin composite sealants (Beiruti et al. 2006b), while no difference was obtained in the four remaining studies. Three studies used the same ART carious lesion assessment criteria (Beiruti et al. 2006b; Zhang et al. 2014; Hilgert et al. 2015) while four studies sealed only high-caries risk occlusal surfaces in first permanent molars (Beiruti et al. 2006b; Zhang et al. 2014; Liu et al. 2014; Hilgert et al. 2015) (Table 18.2). Given that, in addition to the methodological differences, different brands of materials and different operators were used, it is remarkable that sealants produced through the ART procedure using high-viscosity glass-ionomers show a similar or significantly higher performance than resin composite sealants, which were considered to be the reference sealant material (Deery 2013).

On the basis of extensive evidence, the use of dental sealants is strongly recommended for all at-risk surfaces. Both resin composite material and high-viscosity glass-ionomers, in combination with the ART approach, show good results (Table 18.3).

Two retrospective studies carried out in the UK in which primary teeth remained unrestored but received preventive care showed that the majority of the teeth (82%) exfoliated naturally and symptomless (Tickle et al. 2002; Levine et al. 2002). Considering these results and the fact that primary teeth have a relatively short life span, a prospective study was performed that compared a mainly non-restorative procedure with two restorative procedures. The rationale behind the study design was that regular toothbrushing with fluoridated toothpaste (1 100 ppm) would be sufficient for preventing medium- to large-sized cavitated dentine carious lesions from progressing while the difficult-to-clean small cavities could be restored using the ART approach (Frencken et al. 2012b). Some medium and large cavities were opened further using hand instruments to allow proper removal of biofilm with a toothbrush. This protocol was termed ‘ultraconservative treatment’ (UCT). The UCT protocol was compared to the ART and to amalgam restorations in a group of high-caries risk children aged 6 to 7 years. Results showed no significant difference between the survival rates of teeth that were restored and those treated using the UCT protocol after 3.5 years (Mijan et al. 2014). There was also no significant difference in the exfoliation pattern of primary molars between the three treatment protocols after 3.5 years (Mijan et al. 2015). About 88% of teeth treated using UCT exfoliated without any pathology and/or toothache (Mijan et al. 2015).

Such results reinforce the idea postulated by Kidd (2004) that nonoperative treatments can lead cavitated deciduous teeth to exfoliate without pain. However, it is important that more studies in which similar approaches are tested are conducted. These are necessary not only to generate evidence about this treatment protocol but because nonoperative approaches based on diet and oral hygiene control may turn out to be the best strategy for overcoming the reality reported by Marcenes et al. (2013), that untreated cavitated dentine lesions in primary teeth affect more than 620 million children in the world. Treating these cavities restoratively is simply not possible and might not be needed.

The effectiveness of removing the biofilm from within a cavity in controlling carious lesion progression was thought years ago to be increased by placing silver diamine fluoride (SDF) in the open cavity. SDF is a combination of silver nitrate and sodium fluoride (Ag(NH₃)₂F). When applied to carious tissues, it inhibits carious lesion progression by its interaction with bacteria (Knight et al. 2007). For that reason, open cavities have been treated using SDF, particularly in primary teeth. The main disadvantage of using SDF is that the lesions treated will be stained black and might displease some children and parents.

In terms of effectiveness, a series of clinical trials has shown that the application of 38% SDF was effective in arresting dentine cavitated carious lesions in upper anterior teeth of children aged 3 to 5 years (Lo et al. 2001; Chu et al. 2002) and in primary canines and molars of 6-year-old schoolchildren (Llodra et al. 2005). Different concentrations (12% and 38%) of SDF were tested in arresting dentine carious lesions in children aged 5, and the results showed that a single spot application of 38% SDF is more effective than the 12% concentration after 24 months but that the effectiveness decreases over time (Yee et al. 2009).

It is concluded that SDF can be considered an alternative treatment for primary teeth where other caries control strategies are not available. However, the optimum frequency of application needs to be investigated.