**4.2 Application of sealant**

Sealant is applied on tooth's surface with delicate brushes made of camelhair, by means of special applicators with a plastic ball or with a cannula resembling a syringe needle. The time required for sealant application and its quantity depend on material type. Chemically cured sealants have a limited curing time and have to be mixed and placed before hardening commences. Otherwise they become too dense and do not reach the required depth in microfissures created by etching. Light-cured sealants have unlimited bonding time, which allows placing of resin when its viscosity is lowest. Too little sealant may cause early material loss, because it cannot cover the whole etched surface, which results in low retention. Too much sealant may impair occlusion or cause unsatisfactory retention due to

Sealing of Fissures on Masticatory Surfaces of Teeth as a Method for Caries Prophylaxis 259

radioluminescence method showed carious centers in 32.4% of sealed teeth which during previous clinical tests were deemed healthy (85). In 58% of teeth caries was observed in

The impact of fissure morphology on sealant's retention is associated with conditions of mechanical retention of material. Sealant is retained better in deep fissures than in shallow ones, and also better in fissures with initial caries, where fissure surface is uneven, than in

The degree of tooth eruption and tissues' exposure time to oral environment under sealant have a significant impact on the prophylactic effect of sealing (6). Healthy enamel during tooth eruption is relatively well mineralized, however the process of forming the nonorganic composition of the tissue is not yet finished and is subjected to constant physical and chemical changes. Physical changes are various types of abrasion, microcracks and fractures of enamel which occur when crystals of enamel surface layer become fully etched by acids from consumed food. Chemical changes include enamel maturing, which results from continuous dynamic exchange of ions between plaque and fluid in oral cavity on one hand and enamel surface on the other one. Study results indicate that anatomical group of teeth, their position in the dental arch (superior, inferior) may also impact prophylactic efficacy of tooth sealing. It has been proved that sealing of inferior teeth yields better results than sealing of superior ones. Higher efficacy of sealing of inferior teeth is caused by better access of the operator to masticatory surfaces being sealed, better penetration of viscous sealant into fissures due to pressure gradient. An analysis of available literature and own studies indicates that the lowest results are obtained in case of sealing superior second premolars. It is connected - among other things - with small occlusal surface, short fissures and proximity of the parotid gland. A comparison of sealant retention on premolars and molars shows that sealing materials demonstrate better retention on molars. Caries reduction in premolars is also lower compared to reduction on molars after sealing procedure. Lower caries reduction in premolars may be associated with later eruption of

those teeth and their generally lower susceptibility to caries compared to molars (36).

with etched enamel on cuspal slopes and not at fissure bases (3).

Type of sealing material has been deemed a particularly important factor which may impact the effect of sealing procedure to a greater degree than other factors. In caries prophylaxis of lateral teeth various methods and materials are used, e.g. fluoride varnish, resins based on bis-GMA formula (reinforced or not by microfiller particles) enriched or not by fluoride ions (44) and conventional glass-ionomer cements (chemically cured) (77,38), reinforced by silver filings (cements) and HEMA resin-modified cements (7), resins modified with polyacid (7), semi-fluid materials (13,14), ormocers (12,15). Sealing materials are characterized by liquid consistence which allows their inflow into fissures, however it is believed that sealant bonds

Results of studies on fluoride varnishes showed that despite their efficacy in suppression of caries on flat surfaces of teeth, they are less effective in suppression of caries on masticatory surfaces. This is due to the fact that compared to bis-GMA resins and glass-ionomer cements, fluoride varnishes are retained at the most for a few days only, therefore their prophylactic effect depends on the number of fluoride ions released while the varnish remains on the tooth. Fluoride varnishes reduce caries from 50 to 70% depending on frequency of application. In case of three applications during one year, caries reduction on masticatory surfaces is from 50 to 56%, whereas with three yearly applications during three

fissures, which included enamel and dentine (19).

fissures free from caries.

break-off or abrasion of material. If a loss or inaccuracy in covering of surface is observed, excess material should be removed with a coarse and fine coated diamond drill with subsequent polishing until smooth (58,60). Surveys among children and their parents on acceptance of colored sealants (red, pink, yellow, white, opalescent) indicated that a great majority of individuals prefer - for aesthetic reasons - white and opalescent sealants.
