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Dental sealants also known as fissure sealants are defined as a preventive dental treatment, where a plastic material is placed in the pits and fissures or chewing surfaces of primary or permanent molar & premolar teeth at the back of the mouth. These molar teeth are considered the most susceptible teeth to dental caries due to the anatomy of the chewing surfaces of these teeth, which unfortunately inhibits protection from saliva and fluoride and instead favours plaque accumulation.
Dental caries is a disease process that occurs within our mouths everyday. It can be described as the balance between loss and gain of minerals from a tooth surface. The loss of minerals from our teeth occurs from the bacteria within our mouths fermenting foods and producing acids, whereas the tooth gains minerals from our saliva and fluoride that is present within our mouths. When this balance is skewed due to frequent intake of fermentable carbohydrates, poor oral hygiene and lack of fluoride consumption there is a continuous loss and little gain of minerals over a long period of time, which can ultimately cause what we know as tooth decay. Fissure sealants are a preventive treatment that is part of the minimal intervention dentistry approach to dental care. This approach facilitates prevention and early intervention, in order to prevent or stop the dental caries process before it reaches the ends stage of the disease, which is also known as the “hole” or cavitation of a tooth. Once the tooth is cavitated it requires a dental restoration in order to repair the damage, this emphasizes the importance of prevention in preserving our teeth for a lifetime of chewing.
The aim of fissure sealants is to prevent or arrest the development of dental caries. Preventing tooth decay from the pits and fissures of the teeth is achieved by the fissure sealants blocking these surfaces and therefore stopping food and bacteria from getting stuck in these grooves and fissures. Fissure sealants also provide a smooth surface that is easily accessible for both our natural protective factor, saliva and the toothbrush bristles when cleaning our teeth. Multiple oral health care professionals including a dentist, dental therapist, dental hygienist, an oral health therapist and dental assistants (in some states in the USA ) are able to apply dental sealants to teeth.
There have been many attempts made within past decades to prevent the development of caries, in particular occlusal caries as it was once generally accepted that pits and fissures of teeth would become infected with bacteria within 10 years of erupting into the mouth. G.V. Black, the creator of modern dentistry, informed that more than 40% of caries incidences in permanent teeth occurred in pits and fissures due to being able to retain food and plaque.
One of the first attempts to prevent occlusal caries occurred as early as 1905 by Willoughby D. Miller. Miller, a pioneer of dentistry, was applying silver nitrate to surfaces of teeth, chemically treating the biofilm with its antibacterial functions against both Streptococcus mutans and Actinomyces naeslundii, which are both carious pathogens. Silver nitrate, which was also being practiced by H. Klein and J.W. Knutson in the 1940s, was being used in attempt to prevent and arrest occlusal caries.
In 1921, T.P. Hyatt, a pioneer researcher, was the first person to recommend prophylactic odontotomy (preventive operation). This procedure involved creating Class 1 cavity preps of teeth that were considered at risk of developing occlusal caries, which included all pits and fissures. The widening of the pits and fissures were then filled with amalgam.
C.F Bödecker, a dentist and dental researcher, also made attempts to prevent occlusal caries. Initially, in 1929, Bödecker attempted to prevent occlusal caries by cleaning the pit and fissures with an explorer and then sealing the pits and fissures with dental cement, such as oxyphosphate cement. Bödecker then later became an advocator for prophylactic odontotomy procedures (preventive operations).
It was in 1955, that M.G. Buonocore gave insight to the benefits of etching enamel with phosphoric acid. His studies demonstrated that resin could be bonded to enamel through acid etching, increasing adhesion whilst also creating an improved marginal integrity of resin restorative material. It was this bonding system that lead to the future successful creation of fissure sealants.
In 1966, E.I. Cueto created the first sealant material, which was methyl cyanoacrylate. However, this material was susceptible to bacterial breakdown over time, therefore was not an acceptable sealing material. Bunonocore made further advances in 1970 by developing bisphenol-a glycidyl dimethacrylate, which is a viscous resin commonly known as BIS-GMA. This material was used as the basis for many resin-based sealant/composite material developments in dentistry, as it is resistant to bacterial breakdown and forms a steady bond with etched enamel.
In 1974, glass ionomer cement fissure seals (GIC) were introduced by J.W. McLean and A.D. Wilson. GIC materials bond both to enamel and dentine after being cleaned with polyacrylic acid conditioner. Some other advantages GIC’s 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.
Indications & Contraindications
Indications for the use of dental sealants are individual patients or teeth that are at high risk of dental caries.
This includes patients with:
- A history of dental caries
- Deep retentive pits and fissures
- Early signs of dental caries
- Poor plaque control
- Enamel defects, such as enamel hypoplasia
- Orthodontics appliances.
Contrindications for the use of dental sealants are individual patients or teeth that are at a low risk of dental caries:
This includes patients with:
- A balanced diet low in sugars or carbohydrates
- Exceptional oral hygiene
- Teeth with shallow, self-cleansing pits and fissures
- Teeth that a partially erupted without adequate moisture control (operators may choose to use GIC in these cases)
- Teeth with previously restored pits and fissures.
After the placement of rubber dam around the tooth being treated to ensure moisture control, the operator first cleans and dries the biting surface of the tooth. Then a slightly acidic solution is applied on the tooth to create a rough surface that increases the surface area for better retention of the sealant. Finally, a thin layer of liquid plastic material is painted into the pits and fissures of the tooth. After application of the plastic liquid, blue spectrum natural light is shone on the applied material for a few seconds to cure (set) the plastic. Alternatively, a self-cure glass ionomer cement can be used which is cured via a chemical process, rather than the use of a light. After curing, the plastic becomes a hard, thin layer covering the treated portions of the tooth, which makes these surfaces easier to clean.
Although sealants do wear naturally and may become damaged over time, they have the potential to remain effective for five years or longer, despite the heavy pressures endured by teeth during chewing each day. Longevity of the dental sealants is also dependent on the type of material used for the fissure sealant, which is discussed below. It is believed that bacteria and food particles may eventually become entrapped under the dental sealants, and can thus cause decay in the very teeth intended to be protected.
Effectiveness and longevity
Sealants are accepted as an effective preventive method for caries, and as long as the sealant remains adhered to the tooth caries 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. 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. 
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 
Materials and retention rates: GIC v’s Resin.
On the basis of limited evidence both 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 fissure 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.
Fissure sealants should be reviewed annually to ensure that they are retained in the fissures of the teeth. One of the major causes to the loss of sealants in the first year is salivary contamination, therefore it is important to have adequate isolation during the placement of sealants. 
Dental sealants & Bisphenol A
In recent years, Bisphenol A (BPA) and dental sealants have been a point of discussion for researchers, dental providers, and consumers. It is known that resin based dental sealant materials are based on Bisphenol-A (BPA). The BPA structure assembles a bulk, stiff chain that offers low susceptibility to biodegradation as well as great rigidity and strength. BPA is a hormonally active, synthetic chemical and part of a broad group of chemicals known as endocrine disrupting compounds. More specifically, BPA is a xenoestrogen, which mimics the relative bioactivity of estrogen. BPA is used in the manufacture of polycarbonate plastic and epoxy resins and leaches from food and beverage containers, baby bottles, children's toys and dental sealants. BPA can additionally be found in saliva in detectable amounts (micrograms) after placement of dental sealants.  However, dental resins are composed primarily of BPA derivatives, rather than pure BPA. When resins use bisphenol A dimethacrylate (Bis-Dma), BPA can be found in saliva. Resins with bisphenol A diglycidyl ether methacrylate (Bis-Gma) do not hydrolyze into BPA. Salivary BPA levels decreased over time with highest exposures immediately after placement of the sealant. The longest duration of salivary BPA was 3 hours after placement, so there is little risk of chronic low-dose BPA exposure. The goal of the dentist is to limit the exposure after the placement of the resin/composite.. Even though the patient may come into contact with uncured composites, the release of uncured particles after setting the material has been alleged to cause BPA being detected in the saliva. The Australian Dental Association and the American Dental Association  have issued statements on their websites regarding BPA in dental sealants.The American Dental Association states that consumers are not at risk from BPA exposure through dental materials because the exposure to BPA from dental sealants are low and infrequent and pose no know health threat  Dental resins are composed primarily of BPA derivatives, rather than pure BPA. When resins use bisphenol A dimethacrylate (Bis-Dma), BPA can be found in saliva. Resins with bisphenol A diglycidyl ether methacrylate (Bis-Gma) do not hydrolyze into BPA. Salivary BPA levels decreased over time with highest exposures immediately after placement of the sealant. The longest duration of salivary BPA was 3 hours after placement, so there is little risk of chronic low-dose BPA exposure. The goal of the dentist is to limit the exposure after the placement of the resin/composite
An alternative to a resin-based sealant could be the use of glass-ionomer. Studies have shown that the use of glass-ionomer can be just as effective as resin-based sealants, and are less technique sensitive. In areas without proper dental facilities, LED cured glass-ionomer sealants were shown to be more effective than resin-based sealants. In addition, glass-ionomer sealants don’t utilize bisphenol A and can be looked at as an alternative for concerned patients.
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