Dental sealants (also termed pit and fissure sealants, or simply fissure sealants) are a dental treatment intended to prevent tooth decay. Teeth have recesses on their biting surfaces; the back teeth have fissures (grooves) and some front teeth have cingulum pits. It is these pits and fissures which are most vulnerable to tooth decay because food and bacteria stick in them and because they are hard-to-clean areas. Dental sealants are materials placed in these pits and fissures to fill them in, creating a smooth surface which is easy to clean. Dental sealants are mainly used in children who are at higher risk of tooth decay, and are usually placed as soon as the adult molar teeth come through.
Modern Sealant Materials
Resin Based Sealants
It is customary to refer to the development of resin based sealants in generations:
First generation: set with UV curing. They are no longer marketed.
Second generation: chemical-curing (autopolymerized).
Third generation: visible light-cured.
Fourth generation: contain fluoride.
As part of the wider debate over the safety of bisphenol A (BPA), concerns have been raised over the use of resin based sealants. BPA is a xenoestrogen, i.e. it mimics the relative bioactivity of estrogen, a female sex hormone. Pure BPA is rarely present in dental sealants, however they may contain BPA derivatives. There is very little research about the potential estrogen-like effects of BPA derivatives. A transient presence of BPA in saliva has been reported immediately following placement of some resin based sealants. The longest duration of salivary BPA was 3 hours after placement, so there is little risk of chronic low-dose BPA exposure. The currently available evidence suggests that there is no risk of estrogen-like side effects with resin based sealants. Several national dental organizations have published position statements regarding the safety of resin based dental materials, e.g. the American Dental Association,[nb 1] the Australian Dental Association,[nb 2] the British Dental Association,[nb 3] and the Canadian Dental Association.
Glass Ionomer Sealants
GIC materials bond both to enamel and dentine after being cleaned with polyacrylic acid conditioner. Some other advantages GICs have is that they contain fluoride and are less moisture sensitive, with suggestions being made that despite having poor retention, they may prevent occlusal caries even after the sealant has fallen out due to their ability to release fluoride.
Resin Based Sealants Versus Glass Ionomer Sealants
It was shown that GIC materials were more effective in prevention of development of caries despite the higher non-successful rate compared to resin based sealants. This may be accounted for due to the fluoride-releasing property of GIC which increases salivary fluoride level that may aid in preventing dental caries.
Resin-based sealants are normally the preferred choice of material for denture sealants. GIC material may be used as a provisional protective material when there are concerns regarding adequate moisture control.
Dental sealants are accepted as an effective preventive method for cavities and as long as the sealant remains adhered to the tooth, cavities can be prevented. It is for this reason that sealant success is now measured by the length of time a sealant remains on the tooth, rather than the decay experienced in sealed and unsealed teeth. The ability of a pit and fissure sealant to prevent dental caries is highly dependent on its ability to retain on the tooth surface.
It has been demonstrated that the use of adhesive systems before applying dental sealants improves retention. Traditional retention of a sealant on tooth surface is through acid etching.
The most common reason for sealant failure is salivary contamination during sealing placement. Other factors include clinician inexperience, lack of client co-operation, and less effective sealant material used.
Sealants may be in conjunction with fluoride varnish as a preventive method which is shown to be significantly more successful than fluoride varnish alone.
Various factors can help contribute to the retention of fissure sealants. These include:
- Isolation of teeth from saliva
- Not placing sealants on partially erupted teeth as there is gingival tissue on the crown
- Good operator techniques
- Preparation of the fissure by cleaning out plaque and debris prior to placement
Although dental sealants do wear naturally and may become damaged over time, they usually last for around five to ten years, despite the heavy pressures endured by teeth during chewing each day. Longevity of dental sealants is also dependent on the type of material used. It is not uncommon for dental sealants to be retained well into adulthood. It is believed that bacteria and food particles may eventually become entrapped under dental sealants, and can thus cause decay in the very teeth intended to be protected.[medical citation needed] Dental sealants are inspected during routine dental visits to ensure that they are retained in the fissures of the teeth. Damaged sealants can simply be repaired by adding new sealant material. One of the major causes of the loss of sealants in the first year is salivary contamination.
On the basis of limited evidence both GIC and resin materials are equally acceptable in caries prevention, however retention rates between GIC and Resin have been shown to differ. Resin has been shown to be the superior product for retention. A 2-year clinical trial comparing GIC and Resin for dental sealants demonstrated that the GIC had a total loss rate of 31.78%, in contrast to the resin which had a total loss rate of 5.96% The study did acknowledge that GIC had its therapeutic advantages other than retention, this included the benefit of fluoride release and its use on partially erupted teeth. Though GIC has poorer retention rates, the fact that they release active fluoride in the surrounding enamel is very important. They can exert a cariostatic effect and increased release of fluoride, and for these reasons GIC is more of a fluoride vehicle rather than a traditional fissure sealant. All three materials are as effective as each other if the correct techniques are used to complete the procedure.