Keywords atraumatic restorative treatment - fissure sealants - glass ionomer sealants - resin-based
sealants
Introduction
Dental caries is the most common disease affecting almost all the communities worldwide
with an increased prevalence in school children. It is reported that around 90% of
the carious lesions occur on the susceptible occlusal surfaces of the teeth in the
school going children age group.[1 ]
[2 ] The fissure sealants have been in use since the 1960s to seal pits and fissures
(of the molars/premolars) among individuals with high caries risk. The pit and fissure
sealants are considered to be one of the effective methods for preventing dental caries.[3 ]
[4 ]
The current management of caries risk individuals involves use of one of the two main
groups of sealants, namely the resin and glass ionomer based sealants.[5 ] The resin sealants are primary treatment modalities considering individuals with
high for caries risk, owing to their superior retentive and physical properties. These
properties enable them to retain on occlusal surfaces for a considerable period of
time or boosting the longevity of restoration.[6 ] However, the routine use of these resin sealants is limited by technique sensitivity
during clinical application procedure.[3 ]
The glass ionomer sealants, on the other hand, are hydrophilic in nature and therefore
are less dependent on profound moisture control for retention on tooth surfaces.[7 ] The introduction of high viscous glass ionomer cements with improved mechanical
properties, rapid setting time, and a higher abrasive resistance led them to be used
in the atraumatic restorative treatment (ART) framework. The ART involves placing
high viscosity sealants onto the pit and fissures, followed by the press finger technique
and removal of excess material via hand instruments. These sealants are thus popularly
termed as ART sealants.[8 ]
[9 ]
The ART sealants employing high viscosity glass ionomers (HVGIC) are reported in literature
to have enjoyed a higher survival rate in comparison to conventional low viscosity
glass ionomers.[10 ]
[11 ] However, the clinical picture turns ambiguous, the moment ART sealants are stacked
up against resin-based sealants, which are considered the gold standard, in the field
of fissure caries prevention. A recent systematic review had identified a research
lacunae and stated the need for further high quality trails comparing the effectiveness
of resin sealants and high viscosity glass ionomer sealants.[12 ]
Considering the lacunae in the literature, a randomized controlled trial was carried
out among a section of school going children belonging to a district in the Southern
Indian state of Telangana, India. The objective of this trial is to report the efficacy
of ART sealants, which employ HVGICs and resin-based sealants in terms of retention
and fissure caries prevention over a period of 24 months. The null hypothesis states
no difference between these types of sealants in terms of retention and caries preventive
benefits.
Materials and Methods
Study Design
This study is a randomized controlled clinical trial employing a split mouth design,
undertaken to assess the clinical performance of ART sealants in comparison to resin-based
sealants. The current trial was registered with the U.S. National Library of Medicine
(ClinicalTrials.gov NCT02408601).
Ethical Aspects
The ethical clearance for the study was obtained from the institutional review board,
Kamineni Institute of Dental Sciences (reference number: KIDS/2015/13D), Telangana,
India. The trial was carried out in accordance with Declaration of Helsinki and in
adherence to the CONsolidated Standards of Reporting Trials (CONSORT) guidelines.
Study Population
School children belonging to the lower socioeconomic group, in the age group between
6 and 12 years, enrolled in the largest semi-autonomous school in this region were
invited to participate in the study. Appropriate permissions had been obtained from
the district educational officer and the school headmaster prior to the initial approach.
This district is one of the prominent districts in the newly carved out South Indian
state of Telangana and is a known endemic fluoride belt.[13 ] The municipal drinking water supply of this district is not fluoridated. The usage
of fluoridated toothpaste is widespread in this district, and the dental caries prevalence
of the 12/15-year-old children in this region was reported to be 56.3%.[14 ]
Only children, whose parents or guardians had given their consent, were clinically
examined by the chief investigator to assess the baseline status of mandibular permanent
first molars. The examinations were carried out within the school premises by using
portable dental chair and standard diagnostic instruments. The presence of caries
was decided based on the criteria proposed by the World Health Organization (1987).[15 ]
Sample Size Estimation
The sample was calculated based on an expected difference of 15% between the two groups,[16 ] with significance level at 5%, power of the study being 80%, at a two tailed 90%
confidence interval and the percentage success in both groups to be 50%, to be 191
per group.
Inclusion/Exclusion Criteria
The children aged 6 to 12 years, with dentin caries free contra lateral permanent
mandibular first molars with a well-defined fissure system, having a Decayed, Missing,
and Filled Teeth score >2 and with fully exposed clinical crowns were included for
the study. The radiographic examinations were not considered to screen these subjects
for presence of carious lesions. The participants with shallow fissure system, those
with preexisting cavitated carious lesions on lower permanent molars, with history
of allergic reactions toward dental materials, enamel hypoplasia, and those uncooperative
were excluded from the study.
Randomization Procedure
The ART sealants (Ketac Molar Easymix, 3 M ESPE, Seefeld, Germany) and Helioseal (Vivadent,
Schaan, Liechtenstein) were compared with each other in this clinical trial. The trial
adopted a split mouth design using contra lateral mandibular permanent first molars.
The mouth was split vertically into two sides (right and left), and a simple randomization
procedure was followed. Within each participant, random numbers were chosen to select
which side received either the resin or the glass ionomer material.
Operator Training
A single graduate student of the department was chosen for these sealant applications.
He was put through theoretical sessions and underwent hands on training session in
the simulation lab on the practical aspects of sealant handling and application. The
graduate student applied these sealants randomly to a set of 10 children, who were
not a part of the study sample. Any errors or discrepancies in the clinical procedures
were discussed and corrected appropriately.
Sealant Applications
The study subjects were summoned to the preventive clinics of the dental institute
in a systematic manner for sealant applications. The customary oral prophylaxis was
carried out for every child prior to the sealant placement with an ultrasonic scaler,
followed by polishing with slurry water and rotating brush. The isolation was achieved
by using cotton rolls and saliva ejector. The sealant applications were carried in
preventive dental clinics of the teaching institute, with active supervision from
the Department of Public Health Dentistry.
The interventional procedure for resin sealants group involved isolating the specific
molar tooth, acid etching (with 35% phosphoric acid for 15–20 seconds), followed by
washing with water. The tooth was then air dried by using a three-way in one syringe.
The resin sealant was introduced subsequently and light cured accordingly. With regard
to the ART group, the teeth were conditioned with 10% polyacrylic acid for 10 to 15
seconds and cleaned by cotton pellets. The glass ionomer material was hand mixed and
placed onto the occlusal surface by using the finger press technique.[17 ] The retention of the sealants were evaluated, and occlusal discrepancies were corrected
by using an articulating paper. The participants and their guardians were instructed
to follow postoperative guidelines following the placement of sealant material.
Postoperative Evaluation
The participants were followed up at the end of the 6 months, 1 year, 1.5 years, and
2 years, respectively. These evaluations were carried out by the chief examiner who
had been involved in the baseline examination of the study subjects prior to the start
of the study.
The retention of the sealants and the presence of caries were assessed at each of
the designated follow-ups within the school premises. A sharp sickle shaped explorers
were employed to assess the retention and community periodontal probes were used to
diagnose carious lesions that developed over time. The retention of the sealants was
graded according to Simonsen’s criteria,[18 ] which categorized sealant retention into completely retained, partially retained,
and completely lost. The occurrence of a caries lesion was considered if the depth
of the lesion involved the dentin as stated by the World Health Organization.[15 ]
Duplicate examinations were carried out at the scheduled follow-up intervals on about
10% of the sample selected randomly to reassess retention and dental caries characteristics.
The intraexaminer reproducibility of this examiner was monitored appropriately.
Data Analysis
The data were coded appropriately and entered into Microsoft Excel worksheet and analyzed
by using the SPSS software version 20 (IBM, Armonk, New York, United States). The
intraexaminer reliability for the initial baseline screening and subsequent follow-ups
calculated by means of kappa value. Significance was considered when the p -values were less than 0.05 in all instances. The Chi-square tests were employed to
assess the retention rate and the caries preventive benefits between the materials
at designated follow-up periods. The Kaplan–Meier survival analysis was performed
to assess the cumulative retention rate and the survival of dentin caries free pit
and fissures amongst both groups, with long-rank tests employed to ascertain the significance
levels. The hazards function graph was presented to depict the risk of sealant loss
over a period of time. A binary logistic regression analysis was performed to calculate
the odds of developing caries amongst the two groups.
Results
The study population included the entire cohort of children in the age group between
6 to 12 years, which stood at 523. Parents/guardians of 40 children refused to let
their children to be a part of this trial. After matching the rest against the inclusion
and exclusion criteria, 198 children (103 males, 95 females), with an mean age of
9.5 ± 2.21 years were included in the study. Each participant had received both sealants
under study, totaling to 396 sealant applications for all the 198 children. There
were 7 dropouts and 21 absentees at various stages of the study period ([Fig. 1 ]). The intraexaminer agreement values for baseline examination and sealant assessment
was 0.93 and 0.92, respectively.
Fig. 1 Consort flow chart representing the study design.
The retention rates of these sealants at designated intervals are represented in [Table 1 ]. A marginal difference in retention rates has been observed at the 6 months. At
12th month, about one-fourth of the ART sealants were completely lost, with 8.4% of
the resin sealant being lost totally. More than half of the ART sealants were completely
lost at the end of the study period, with about 30% total loss seen in the resin group.
The analysis reveals a statistically significant difference between their retention
rates at each of the designated intervals. With regard to carious lesion formation
on these sealed surfaces, a substantial percentage of occlusal surfaces have remained
carious free across both groups of sealants, with the incidence of dental caries being
10.5 and 6.66% for ART and resin group, respectively with no significant difference
observed in this domain ([Table 2 ]).
Table 1
Frequency distribution of retention rates at each of the designated follow-up intervals
among atraumatic restorative treatment and resin sealants
ART sealant group
Resin-based sealant
p -Valuea
Abbreviation: ART, atraumatic restorative treatment.
a McNemar’s test.
At 6 mo
Completely retained
147 (75.3%)
163 (83.5%)
0.039
Partially retained
37 (18.9%)
27 (13.8%)
Completely lost
11 (5.6%)
5 (2.56%)
At 12 mo
Completely retained
112 (58.9%)
139 (73.1%)
0.001
Partially retained
32 (16.8%)
34 (17.8%)
Completely lost
46 (24.2%)
17 (8.9%)
At 18 mo
Completely retained
72 (38.9%)
98 (52.9%)
0.000
Partially retained
34 (18.3%)
53 (28.6%)
Completely lost
79 (42.7%)
34 (18.3%)
At 24 mo
Completely retained
57 (31.6%)
71 (39.4%)
0.000
Partially retained
26 (14.4%)
54 (30%)
Completely lost
97 (53.8%)
55 (30.5%)
Table 2
Comparison of caries incidence between teeth sealed with atraumatic restorative treatment
and resin sealants
ART sealant group
Resin sealant group
p -Valuea
At 12 mo
Caries absent
182 (95.7%)
185 (97.3%)
Caries present
8 (4.21%)
5 (2.63%)
0.210
At 24 mo
Caries absent
161 (89.4%)
168 (93.3%)
Abbreviation: ART, atraumatic restorative treatment.
a McNemar’s test.
Caries present
19 (10.5%)
12 (6.66%)
0.265
The Kaplan–Meier survival analysis presented a cumulative survival rate of 37.5% at
the end of 2 year period and a median survival time of 24 months with resin sealants.
Similarly, ART sealants had a cumulative survival rate of 30.9%, with a median survival
time of 18 months ([Tables 3 ], [4 ]; [Fig. 2 ]). The Long-rank test showed a statistical difference between cumulative retentive
rates of these materials ([Fig. 2 ], p = 0.030). The Cox regression coefficient for the survival of these sealants was directly
proportional, with the p- value at 0.070. Analyzing the risk of sealant loss over a period of time, a hazard
function graph is depicted, which explicitly states that risk of sealant loss across
both groups exponentially increases with time ([Fig. 3 ]).
Table 3
The mean and median survival time of fully and partially retained sealants in months
with regard to atraumatic restorative treatment and resin-based sealants
Meana
Median
95% confidence interval
95% confidence interval
Estimate
SE
Lower bound
Upper bound
Estimate
SE
Lower bound
Upper bound
Abbreviations: ART, atraumatic restorative treatment; SE, standard error.
ART
16.473
0.533
15.429
17.517
18.0
1.057
15.929
20.071
Resin
18.578
0.483
17.633
19.524
24.0
1.167
21.712
26.288
Table 4
Cumulative survival percentages and standard error of fully and partially retained
resin and atraumatic restorative treatment sealants over a period of 24 months
Resin sealant
ART sealant
Interval
Survival (%)
SE
95% CI
Survival (%)
SE
95% CI
p
-Value
Abbreviations: ART, atraumatic restorative treatment; CI, confidence interval; SE,
standard error.
6 mo
84.1
2.6
0.837–0.845
73.8
3.1
0.734–0.742
<0.05
12 mo
73.8
3.1
0.734–0.742
60.4
3.5
0.599–0.609
<0.05
18 mo
51.7
3.6
0.512–0.522
40.3
3.5
0.398–0.408
<0.05
24 mo
37.5
3.5
0.370–0.380
30.9
3.4
0.304–0.314
<0.05
Fig. 2 Kaplan–Meier survival analysis of partial and fully retained sealants over a period
of 24 months, log-rank test (Mantel Cox test), p = 0.030.
Fig. 3 Hazard function graph depicting the risk of sealant loss as observed in the follow-up
evaluation.
The Kaplan–Meier survival analysis pertaining to survival of dentin carious lesion
free pits and fissures showed no significant difference between these two materials
([Fig. 4 ]). A binary logistic regression analysis calculated the odds ratio (OR) to be 0.747
(95% confidence interval: 0.493–1.13).
Fig. 4 Kaplan–Meier survival analysis pertaining to survival of dentin caries free pit and
fissures at 12th and 24th months, respectively, log-rank test (Mantel Cox test), p = 0.194.
Discussion
A randomized controlled split mouth clinical trial was conducted to test the hypothesis
pertaining to the performance of ART and resin sealants in participants with pit and
fissures of mandibular molar teeth. The initial baseline examination and follow-up
evaluations of the school children was considered as accurate, on account of the high
intra examiner agreement values that were observed.
The blinding of the operator to these clinical procedures could not be done by owning
to the nature of the trial. The lone operator did not have an inclination toward a
particular clinical procedure as he had been trained just before the start of the
trial. The participants had received these preventive therapies for the first time
and thus did not have a prediction toward any sealant material. The risk of detection
bias could not be avoided in subsequent follow-up intervals, as both sealants were
distinctly different in their clinical appearance. Nonetheless, the extent to which
this could have affected the outcome is not known and is difficult to assess.
The data obtained during the study period was coded and presented to the statistician
for analysis, with statistical interpretation done following the culmination of the
data collection. To add to this, the attrition rate for this clinical trial was minimal
(3.5%) and thus assumed to not have affected the final outcome. Taking into account
these inherent limitations, the internal validity of this trial can be considered
as adequate.
The null hypothesis pertaining to sealant retention stands rejected in the current
study. The cumulative survival percentage of ART sealants has been significantly lower
in comparison to the resin group at each designated follow-up interval. This is in
line with a recently published systematic review.[4 ] It is imperative to note that ART sealants in our study were placed by a single-trained
clinician in a controlled clinical environment rather than an outreach facility, for
which it was originally designed for.
Despite the presence of a favorable working environment, the 2-year cumulative survival
percentage of ART sealants in this study stood at 30.9%, which was way below in comparison
to studies carried out by Vieira et al[19 ] (99%, 1-year survival), Holmgren et al[20 ] (98%, 2-year survival), Luengas-Quintero et al[21 ] (48.8%, 2-year survival), Liu et al[22 ] (93%, 2-year survival), Hilgert et al[23 ] (67.7%, 2-year survival), Zhang et al[24 ] (80.7%, 2-year survival), Zhang et al[25 ] (98.5%, 2-year survival), and Frencken et al[26 ] (98%, 2-year survival). A recently published clinical trial also reported a low
ART retention rate when applied within school premises.[27 ] Interestingly, the 2-year cumulative survival percentage of 37.5% with respect to
resin sealants in our study is also well below the retention rates as documented in
the literature.[4 ]
[6 ]
A holistic perspective into the survival percentages of ART sealants indicates a possible
association between clinical experience of operators and retention of these sealants.[26 ]
[28 ] It is a well-known fact that these clinical application steps are meticulous in
nature and rely to a large extent on the handling of these materials. The lower cumulative
survival percentage observed in our study could well be attributed to the inexperience
of the graduate student, despite imparting adequate training prior to the commencement
of the study.
The only probable justification for using an inexperienced operator is that for such
large-scale preventive programs, the availability of experienced dentists is a difficult
proposition in countries lacking adequate oral health care services. However, overzealous
analysis of “retention factor” of sealants must be interpreted with caution. It is
very common in fissure caries clinical trials to use “retention” as a surrogate end
point for caries occurrence or absence, as it makes the conduct of these trials simpler,
shorter, and inexpensive. This concept has been invalidated in due course of time
and thus clinical recommendations or guidelines inclined toward a sealant with superior
retentive properties should be reconsidered.[29 ]
Now that the onus is firmly on fissure caries prevention, the null hypothesis pertaining
to this parameter is accepted, as there has been no significant difference between
dentin caries preventive benefits between these sealants. Also, no difference was
noted in cumulative survival rates of caries free pits and fissures when sealed with
ART and resin sealants at the 12th and 24th month, respectively. This is in tune with
a recent systematic review[12 ] and other similar studies conducted by Chen et al,[30 ] Oba et al,[31 ] Zhang et al,[25 ] and Liu.[22 ] A single study carried out in Syria using a parallel group design found that ART
sealants prevented dental caries significantly better than resin sealants over a 1-
to 3-year period.[32 ]
It is an established scientific fact that presence of a constant level of fluoride
within the oral environment decreases the incidence of dental caries.[33 ] The study participants reside in an endemic fluoride belt and consume drinking water,
which is naturally fluoridated. Concurrently, ART and resin sealants employed here
are also fluoride depots and release free fluoride ions into the oral environment
and thereby further contribute to the anticariogenic effect. To extent to which these
factors could have downplayed the difference between the dental caries lesion preventive
effects between these materials is not known. Moreover, in teeth sealed with glass
ionomers, evidence clearly pointed out to the presence of remnants of glass ionomer
particles in the deeper layers of fissures, even in surfaces with partial or total
loss of glass ionomer sealants, thereby buttressing the anticariogenic effect.[34 ] In a nutshell, the consumption of naturally fluoridated water, the widespread use
of fluoridated toothpastes, and fluoride release from sealants may have influenced
the true caries preventive differences among the sealants, as well as contributing
to anticariogenic effects.
Highlighting the drawbacks of this trial, the use of a split mouth study approach
makes it imperative to select a child with at least a pair of caries free permanent
first molars, in our case, a pair of caries free contra-lateral lower first permanent
molars. This is surely bound to generate selection bias, as children in the high caries
risk category may have had developed caries in one of the lower permanent molars,
therefore rendering them ineligible for the trial.[35 ] Additionally, the baseline clinical examination of the children for the presence
of caries was done in accordance with the WHO criteria,[15 ] which detects cavitated lesions extending into the dentin. The use of precise caries
detection methods such as diagnodent[36 ] might have resulted in a greater number of children being excluded from the trial,
as it is designed to pick up non cavitated dentin carious lesions. Similarly, radiographic
investigations to detect carious lesions were not performed at baseline and at subsequent
evaluations.
All the above methods were not engaged in this trial due to lack of adequate resources.
The future directions from this study are a well-designed parallel study design and
well matched in its baseline characteristics, with children belonging to the high
caries risk category in the age group between 6 and 7 years of age, without the presence
of “fluoride” confounding factor may reveal the true preventive benefits, in this
regard. The comparison of the economic factors of these sealants needs to be assessed,
for effective use in community prevention programs.
Conclusion
The study showed, within its limitations, that no significant differences existed
with respect to caries preventive benefits between the resin and glass ionomer pit
and fissure sealants. However, in the field of retention, resin sealants fared better
than ART sealants in this study population.
