Do sealants deliver as promised for caries prevention?

2017 08 07 15 47 24 917 Dental Bib Girl 400

Sealants are commonly used for caries prevention, but are they all effective? With new sealant materials on the market, researchers updated a previous comprehensive review to reflect new data and to see if they are effective.

Researchers found moderate-quality evidence that certain types of sealants were effective for caries prevention, which was related to sealant retention. However, they reported only lower-quality evidence for sealant effectiveness after more than four years and insufficient evidence about the relative effectiveness of sealant types or adverse effects.

"We are moderately confident that resin-based sealants applied on occlusal surfaces of permanent molars of children and adolescents reduce caries up to 48 months when compared to no sealant," the authors wrote (Cochrane Database of Systematic Reviews, July 31, 2017).

The lead author was Anneli Ahovuo-Saloranta, DDS, senior researcher at the University of Tampere in Tampere, Finland.

Seal it up

Caries prevalence has declined since the 1970s because of improvements in living conditions and oral hygiene, the widespread use of fluoride, and other factors, according to the study authors. However, caries still remain a problem, with the first few years after tooth eruption having the highest risk for caries lesion development in permanent teeth, they noted.

“Resin-based sealants applied on occlusal surfaces of permanent molars of children and adolescents reduce caries up to 48 months when compared to no sealant.”
— Dr. Anneli Ahovuo-Saloranta and colleagues

The effectiveness of caries-preventive interventions depends on the caries risk of an individual. Among these interventions are dental sealants, which when applied to a tooth surface provide a physical barrier that prevents biofilm growth by blocking nutrition.

The current article updates a review first published in 1999 and one most recently updated in 2013, which found that sealants are effective in children with a high caries risk, but limited information was available on its benefit in other individuals. This latest review compared the effects of fissure sealants in preventing caries of occlusal surfaces of premolar or molar permanent teeth of individuals up to age 20. In all, the researchers examined 38 studies, including seven new ones. The studies comprised almost 8,000 children.

The researchers included randomized controlled trials found through searches of various medical study databases in which fissure sealant was applied to occlusal surfaces of permanent first or second molars not previously sealed. The results on these teeth were compared with teeth that had no sealant or a different type of sealant material applied with at least 12 months of follow-up.

Specifically, the group evaluated the effectiveness of the following:

  • Resin/composite-based fissure sealants compared with no sealant at various follow-up times
  • Glass ionomer-based fissure sealants compared with no sealant at various follow-up times
  • New types of fissure sealants, such as ormocer-based sealants, at various follow-up times
  • Various sealant material types

The researchers also examined sealant safety, possible harmful effects, and retention.

Use of fissure sealants concurrent with fillings disqualified studies from inclusion, as did testing of other caries-preventive treatments, such as fluoride varnishes, used concurrently with sealants. However, inclusion criteria allowed studies of fissure sealants used concurrently in test and control groups with fluoride toothpaste or fluoridated water, or in which study participants received oral health instruction or education.

For comparisons of sealant with no sealant, all sealant materials were allowed, save for first-generation resin-based sealants. Control teeth or control groups did not have any sealants placed. Participants in the studies ranged in age from 5 to 16 years and were recruited from selected schools or dental clinics in various countries.

The analysis included the following:

  • Fifteen studies comparing use of resin-based sealant to no sealant (3,620 participants in 14 studies plus 575 tooth pairs in one study)
  • Three studies comparing glass ionomer-based fissure sealant with no sealant (905 participants)
  • Twenty-four studies on the relative effectiveness of different sealant materials (4,146 participants), of which 23 studies compared glass ionomer-based sealant with resin-based sealant and one study compared ormocer-based sealant with low-viscosity glass ionomer

The authors noted that 9 of the 15 studies that compared resin-based sealant with no sealant were conducted in the 1970s and 1980s in high-income countries. Studies comparing sealant materials were published from 1993 to 2014.

The researchers determined with moderate confidence that resin-based sealants reduced caries by between 11% and 51% at 24 months when compared with no sealant. They also found similar results up to 48 months. They defined moderate quality as evidence for which further research is likely to have an important impact on their confidence in the estimate of effect and may change the estimate.

Although the quality and quantity of evidence for longer follow-up was lower, they found that the benefit associated with resin sealant was maintained up to nine years.

The effectiveness of resin-based sealants was related to sealant retention, the authors wrote.

Average resin-based sealant retention rates
by follow-up time
Follow-up period 12 and 24 months 48 to 54 months 9 years (after reapplication up to 36 months)
Average sealant retention 80% 70% 39%

The researchers calculated the effect applying a resin-based sealant would have during 24 months of follow-up on caries risk based on caries incidence in control teeth. Caries incidence in studies conducted in the 2000s was lower in control teeth (16%) than those conducted in the 1970s (40% to 70%).

Estimated caries risk reduction after sealant application
Assumed risk of caries
(carious teeth per 1,000)
Risk after resin-based sealant application
16% 5.2%
40% 6.25%
70% 8.9%

The studies included in the review were generally well-conducted, according to the authors. However, the blinding of outcome assessment for caries had a high risk of bias for all trials since outcome assessors can see and identify sealant, they noted.

"Although there was considerable heterogeneity between the results in all comparisons, results from each individual trial showed highly significant benefit for the sealant," the authors wrote.

For studies that compared the use of glass-ionomer sealant to no sealant, results at 24 months were inconclusive, they stated. In addition, the relative effectiveness of different types of sealants, based on the 24 studies that directly compared two sealant materials, was unknown and the evidence was of very low quality. Comparisons varied in terms of types of sealants assessed, outcome measures assessed, and follow-up duration. Only four studies assessed adverse events, and none were reported.

Long-term studies needed

The authors recommended the performance of studies with longer follow-up periods to better determine sealant effectiveness in populations with different caries prevalence levels. They suggested that future studies report characteristics of study populations that may be risk factors likely to predict caries development. Research on the relative effectiveness of various sealant materials is also needed, they wrote.

"While this review showed that sealants are effective for preventing caries in children and adolescents, the magnitude of effectiveness related to different caries risk levels in the population or children remained unclear," the authors concluded.

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