**4.1.1 Tooth selection**

254 Contemporary Approach to Dental Caries

highest values were observed for Nuva Seal, which was conditioned by material composition. For example, Kerr had 40% of quartz filler particles by volume, which increased its resistance to abrasion and decreased the risk of damaging the surface layer of resin susceptible to abrasion. Due to the necessity of avoiding mastication impairment, sealing material should be present only in anatomical fissures and crevices. Therefore its

Every substance of foreign origin which is introduced into oral environment may have an adverse impact and induce certain biological or health effects. Almost all organic ingredients can be washed out from polymerized sealing material by organic solvents, e.g. methanol, ethanol or water. Released formaldehyde and metacrylic acid are particularly dangerous, the latter creating an inhibitory oxygen layer in the surface layer of sealant after polymerization and it can release into oral environment for a long time (up to 115 days after polymerization). Admittedly it does not cause toxic effect, but it may contribute to a local allergic reaction. During monomer particle disintegration, alcohol may be formed (e.g. from bis-GMA resin - bivalent alcohol). Further metabolism of alcohol occurs in digestive tract, leads to release of bisphenol A (BPA), which is a constituent of many compounds, such as bis-GMA, bis-EMA (bisphenol ethoxylate dimethacrylate), TEGDMA (triethylene glycol dimethacrylate), applied in sealing materials. Bisphenol A was detected in saliva of patients subjected to prophylactic fissure sealing. The substance belongs to the group of chemical compounds called xenoestrogens, which - joining with estrogen receptors - imitate the activity of natural hormones, thus they may impact human health. In a study by Olea *et al.* (56) on the presence of bisphenol A, it was detected at the level of 90-931µg/ml in saliva samples collected from patients one hour after sealing. The study also demonstrated that sealing material exposed to 100oC temperature for 30 minutes in buffers with pH 1 and pH 13, released bisphenol A in concentrations causing increased proliferation of MCF-7 cells up to one hour after application, which indicates induction of para estrogenic activity. In other studies authors assessing seven different sealants *in vitro* did not confirm the presence of bisphenol A in any of the assessed materials. However, determinable amounts of TEGDMA were detected in all studied sealants. It can also be supposed that with proper proceeding, bisphenol A will not be released if substances reacting with each other have a sufficient degree of purity. Only in products containing bis-GMA, small amounts of bisphenol A are released, and it occurs only directly after material curing. In most studies bisphenol A was detected in saliva only directly after application of sealant, and this was the case especially with "older" generation of Delton sealant, which still contained bis-DMA (bisphenol A dimethacrylate) in concentrations not affecting the organism. Approximate calculations of bisphenol A released from sealants showed that its level is lower than 1.5%, and such concentrations are too small to cause carcinogenic effect. A study assessing the presence and concentration of BPA (bisphenol A) in blood serum and saliva in 30 individuals aged 18-40 years before sealing and one, three and twenty-four hours after sealing (Delton Pit&Fssure Sealant Dentsplay) indicated the presence of bisphenol A in all examined patients before sealing at the level from 0.07 to 6.00 ng/ml. The level of bisphenol A three hours after sealing had the highest value and after twenty-for hours it returned to the same value as before sealing. The highest recorded concentrations of bisphenol A after a single application and after four subsequent applications were 3.98mg/ml and 9.08mg/ml respectively. Bisphenol A was not observed in blood serum at any stage of the study (89). Exposures to BPA from other sources than resins contributed to a change of BPA level in saliva. What is

excess should be removed from occlusal surface.

Sealing procedure should be performed not later than four months after eruption of first permanent molars, at the age of 5-6 years, but practically even after 10 years of age premolars at the age of 8-12 years, especially if caries is observed in deciduous teeth and first permanent molars, second permanent molars at the age of 11-13 years, and the procedure can be performed up to the 15th year of age. In a population with a high caries risk, also deciduous molars and permanent premolars should be sealed.

Sealant should be applied in teeth with narrow and deep fissures and in teeth with developmental abnormalities on masticatory surfaces. Sealing depends mainly on meticulousness during clinical procedure, i.e. isolation of teeth from moist oral environment, thorough cleaning of occlusal surfaces, etching, rinsing, drying and application of sealant.

#### **4.1.2 Isolation of teeth to be sealed**

This is a very important stage of the procedure. Maintaining the area dry is critical for successful sealing procedure. Usage of dental dam, saliva ejector and alternatively lignin rolls is recommended.

Sealing of Fissures on Masticatory Surfaces of Teeth as a Method for Caries Prophylaxis 257

liquid etches. Acid penetration is hampered by impurities left over after mechanical

It is advisable to repetitively moisten enamel with acid solution during etching, in order to unblock dentine microtubules by removal of calcium salts precipitated during chemical reaction, which limit the effect of etching. After introduction of one-stage etching (of enamel and dentine), dentists have been using self-etching systems based on non-washable acid monomers (low-concentration acids, 10% phosphoric or maleinic acid, 2.5% nitric acid or their mixtures including extra ingredients such as metal ions, glycerin) (2), which eliminate the rinsing phase thus shortening application time and greatly limit the risk of infection of the operative site by saliva and the risk of a mistake during application, which makes the

A soft brush is recommended for etch application, whereas cotton wool balls are not advisable as they contain bubbles of trapped air hampering even spreading of etching solution. Acid solution leads to creation of microfissures in enamel, whose presence enables sealant's penetration deep into tissues. Microscopically, enamel surface becomes rough and appears matt, in electron microscope view - pits of various shapes are visible which were

After etching, the etched surfaces of teeth are rinsed with high pressure water for 10-20 seconds in order to remove acid and residue after the chemical reaction of etching. If etching

After rinsing the tooth's surface should be dried with compressed air for about 15 seconds and isolated from saliva by dental dam which constitutes a simple and effective method of protecting operative field against infection by microorganisms from saliva. This is necessary because any water remaining after rinsing as well as organic impurities from saliva left on the etched surface, impair sealant's penetration into microfissures, thus decreasing the strength of bonding between sealant and enamel. In case of contact with saliva, etching should be repeated for 15 seconds with subsequent rinsing and drying of the tooth. It should be checked with special attention that the compressed air is not polluted by water or oil.

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

cleaning of fissures.

**4.1.5 Rinsing** 

procedure insusceptible to operator's manual "skills".

**4.1.6 Drying of etched surface of teeth** 

**4.2 Application of sealant** 

created by a loss of some enamel prisms. The pits are 50-52µm deep.

was performed with an acid in gel form, rinsing time should be doubled.

Difficulties with proper procedure occur during sealing of molars in maxilla (neighboring parotid gland) and in fissures of freshly erupted molars in maxilla and mandible, when a fold of mucous membrane covers tooth crown which is not fully erupted.

#### **4.1.3 Cleaning of masticatory surface**

Masticatory surfaces should be carefully cleaned of bacterial plaque with the use of a hard rotating brush with paste containing a small amount of pumice but no fluorine compounds. Many published reports assess various of cleaning masticatory surfaces before procedure and techniques of applying sealant. One of suggestions is to use a brush dampened with hydrogen peroxide, without pumice. Research demonstrated that after cleaning with pumice, its particles are forced into fissures, which may impair resin's penetration into fissures. Botti et al. assessed cleaning of occlusal surfaces from dental plaque with the use of a synthetic fiber brush and PROPHYflex 3 device (11). The results suggest that the assessed device was the most effective in removing dental plaque compared to cleaning by synthetic fibers. Preparation of masticatory surface by air abrasion was conducted with Air Flow sandblaster at 4.5-7 bars of pressure and at 90° angle from a distance of 1 mm. The abrasive material is aluminum trioxide. The high value of kinetic energy of particles ejected as a stream enables effective preparation of hard tissues. It is recommended to use grains below 50 microns and to abrade intermittently (35,54). Sound systems are based on pneumatic scaler working within the range 6000-6500Hz, vibration amplitude 60-1000 microns. The correct pressure should not exceed 1.5N. Diamond drill bits with 25 and 40 micron coating.

Laser etching with Er Cr:YSGG, 2W and 40Hz laser (8) and erbium laser Er:YAG 7W, Er:YAG (5.5W) (49,70,71). Er:YAG laser demonstrates a 15-fold higher water absorption than CO2 laser and 20,000-fold higher than Nd:YAG laser. Activity time is thousandths of a second with a minimal energy dose. The energetic level for enamel ablation is 3.3J/cm3 and for dentine ablation it is 2.8J/cm3. Carisolv system and sodium hypochlorite demonstrated not only effective cleaning of fissures but also antibacterial properties (49,87). Fissure surface preparation with compressed air was assessed by Kramer N *et al.* (43), whereas Mosemi *et al.* studied the impact of masticatory surface preparation with Er Cr YSGG laser and air abrasion, as well as with 37% phosphoric acid on bonding strength on the wall with INSTRON servohydraulic machine. Samples were divided into three groups. In group A, masticatory surface was etched with acid only, in group B air abrasion and acid were applied, and in group C initial etching with laser and phosphoric acid was performed (53). The results indicate that bond strength was highest in the group where air abrasion and acid etching were applied, compared to the group with acid only etching or initial preparation by means of a laser and phosphoric acid etching (43).

#### **4.1.4 Etching**

After protecting a site from access of saliva, after cleaning and drying, etching procedure can be started. In order to obtain enamel etch, acid solution has to be spread on intercusp fissure surface for 15 seconds. The recommended concentration of phosphoric acid is 37%. The introduction of gel etches allowed to limit the impact of acid used to prepare enamel surface before application of sealant and to decrease the risk of uncontrollable contact of etch with dentine. Gels are applied only once, whereas liquid solutions of acids require multiple application. Etches in the gel form penetrate fissure enamel to the same degree as liquid etches. Acid penetration is hampered by impurities left over after mechanical cleaning of fissures.

It is advisable to repetitively moisten enamel with acid solution during etching, in order to unblock dentine microtubules by removal of calcium salts precipitated during chemical reaction, which limit the effect of etching. After introduction of one-stage etching (of enamel and dentine), dentists have been using self-etching systems based on non-washable acid monomers (low-concentration acids, 10% phosphoric or maleinic acid, 2.5% nitric acid or their mixtures including extra ingredients such as metal ions, glycerin) (2), which eliminate the rinsing phase thus shortening application time and greatly limit the risk of infection of the operative site by saliva and the risk of a mistake during application, which makes the procedure insusceptible to operator's manual "skills".

A soft brush is recommended for etch application, whereas cotton wool balls are not advisable as they contain bubbles of trapped air hampering even spreading of etching solution. Acid solution leads to creation of microfissures in enamel, whose presence enables sealant's penetration deep into tissues. Microscopically, enamel surface becomes rough and appears matt, in electron microscope view - pits of various shapes are visible which were created by a loss of some enamel prisms. The pits are 50-52µm deep.
