Due to their macromorphologic structure, occlusal surfaces on molars are extremely caries prone (Fig 10-1). In older literature, it was hypothesized that the narrow and deep pits and fissures on the occlusal surfaces (Fig 10-1, site FL) are to be blamed for the caries development on these surfaces, as they are uncleansable.^1,2 More recently, authors stress the importance of the more open fossa areas (Fig 10-1, circled),^3,4 together with a long-lasting eruption period of these teeth without function from the antagonists.⁵ This promotes plaque accumulation, and thus leads to a high caries susceptibility of these surfaces. The interaction of the two latter problems is the hypothesis mainly accepted today. It is supported by the fact that the occlusal surfaces in the maxillary premolars (Fig 10-1a), which present with a deep and narrow fissure system, hardly ever develop caries or have to be restored in countries with low caries prevalence.

Fissure sealants were suggested as a management for caries on the occlusal surface by Buonocore in the 1950s to 1970s.^6,7 Since then, sealants have been used extremely often in countries where there is a well-established dental system caring for children and adolescents.⁸ It is tempting to suggest that fissure sealants played a major part in the caries decline observed in many countries, such as in Denmark.⁹ Contrary to this assumption, the inter-municipality variation in the number of sealed teeth among children does not mirror the respective caries levels in the different municipalities in Denmark.¹⁰ With the Nexö method, which includes special attention for tooth brushing of erupting molars and therefore limits the indication of sealants to progressing initial caries lesions, one of the lowest caries rates in the world was achieved for adolescents up to 18 years of age.¹¹ Thus sealants seem to be a valuable preventive measure, with the indication and technique discussed later in the chapter. The main aim of this chapter is to examine if fissure sealants can be recommended as a general preventive measure for all children, in the same way that dental practitioners recommend tooth brushing twice a day with fluoridated toothpaste to their patients, or if sealants should be used risk-related. In order to answer this question, the following topics are addressed:

• the progression of the caries demineralization on the occlusal surface and the reactions of the pulp dentin organ, including the radiologic appearances of the different caries stages on the occlusal surface
• at what stage of caries (no caries, initial, moderate, or extensive staged caries) sealants are indicated
• differences between preventive and therapeutic sealing and consequences for indication and technique
• how the effectiveness of fissure sealing compares to basic prevention or to fluoride treatment
• if there are differences in the effectiveness of different materials used as fissure sealants (glass-ionomer cement [GIC], composite resin)
• what recommendations can be made for proper fissure sealing technique.

Caries progression on occlusal surfaces

Based on several studies,^3,12,13 the illustrations in Figs 10-2 and Table 10-1 highlight the caries development observed clinically and radiographically. In Fig 10-2, progressive stages of caries on the occlusal surface are illustrated on sections on the occlusal surfaces with the reactions of the dentin pulp organ. Caries spreads along the direction of the rods (Figs 10-2a and c), and progresses in a pulpal direction on the occlusal surface. The bacteria in the groove-fossa system, the modern term for pits and fissure system,¹⁴ are most metabolically active in the upper part of the relatively narrow parts of the groove-fossa system and in the bottom part of the more open parts of the groove-fossa system.^3,15 The progression rate is, therefore, fastest at the upper part of the narrow grooves, as illustrated in Fig 10-2c. Just before the lesion reaches the enamel dentin boarder, the dentin below reacts with tubular sclerosis, resulting in hypermineralization (Fig 10-2f). If the lesion continues to progress, this hypermineralized dentin will demineralize and there will be a further reaction at the pulp side, where tertiary dentin is formed (Fig 10-2i). In most cases, the surface is still unbroken and the color of the lesion is whitish, yellowish, or brownish (Figs 10-2d, e, g, h, j, and k). If the dentinal de¢mineralization penetrates deeper, either a breakdown will occur in the enamel and/or a shadow will appear clinically (Figs 10-2l to n). With further progression of the lesion, the final step will be the formation of a cavitation into dentin (Figs 10-2o and p), followed by massive invasion of bacteria into the enamel and dentin (Figs 10-2l to p).

Table 10-1 Relation between clinical, radiographic, and histologic stages of occlusal caries

In Table 10-1, the radiologic appearance of progressive clinical stages of occlusal caries is shown. Due to sound enamel on the buccal and lingual surface, it is rarely possible to identify an initial enamel lesion of the occlusal caries on radiographs (Table 10-1, first row). Thus, the first radiographic appearance is a radiolucent area just below the enamel-dentin junction, caused by the demineralization in the dentin (Table 10-1, second row). If the lesion progresses, the radiolucent area will move towards the pulp and when it reaches the middle third (Table 10-1, third row), clinical breakdown of the enamel surface will often appear and/or a shadow will be seen clinically on the occlusal surface. When the radiolucency reaches the inner third of the dentin, dentin cavitation is usually seen clinically, and histologically the demineralization is also in the inner third of the dentin or already in the pulp (Table 10-1, fourth row).¹⁶

The terminology used for staging coronal lesions, including lesions on the occlusal surface, both clinically (Fig 10-2) and radiographically (Table 10-1) is:^16–20

• no lesions
• initial lesions
• moderate lesions
• extensive lesions.

Preventive and therapeutically placed fissure sealants

In the literature, two different indications for fissure sealants are discussed: preventive fissure sealing and therapeutic fissure sealing.

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