Effect of Er:YAG laser enamel conditioning and moisture on the microleakage of a hydrophilic sealant
Effect of Er:YAG laser enamel conditioning and moisture on the microleakage of a hydrophilic sealant
Zeynep Aslı Güçlü 0 1 2
Andrew Paul Hurt 0 1 2
Nazmiye Dönmez 0 1 2
Nichola Jayne Coleman 0 1 2
0 Department of Dental Diseases and Treatment, Bezmiâlem Vakif University , Istanbul , Turkey
1 Department of Pharmaceutical, Chemical and Environmental Sciences, Faculty of Engineering and Science, University of Greenwich , Chatham Maritime, Kent , UK
2 Department of Paediatric Dentistry, Faculty of Dentistry, Erciyes University , Kayseri , Turkey
3 Nichola Jayne Coleman
For a given sealant, successful pit and fissure sealing is principally governed by the enamel conditioning technique and the presence of moisture contamination. A new generation of hydrophilic resin sealants is reported to tolerate moisture. This study investigates the impact of Er:YAG laser pre-conditioning and moisture contamination on the microleakage of a recent hydrophilic sealant. Occlusal surfaces of extracted human molars were either acid etched (n = 30), or successively lased and acid etched (n = 30). Ten teeth from each group were either air-dried, water-contaminated, or saliva-contaminated prior to sealing with UltraSeal XT® hydro™. Samples were inspected for penetration of fuchsin dye following 3000 thermocycles between 5 and 50 °C, and the enamel-sealant interfaces were observed by scanning electron microscopy (SEM). Significant differences in microleakage were evaluated using the Mann-Whitney U test with Bonferroni adjustment (p = 0.05). Laser pre-conditioning significantly reduced dye penetration irrespective of whether the enamel surface was moist or dry. Microleakage of water-contaminated acid etched teeth was significantly greater than that of their air-dried or saliva-contaminated counterparts. SEM analysis demonstrated good adaptation in all groups with the exception of water-contaminated acid etched teeth which exhibited relatively wide gaps. In conclusion, this hydrophilic sealant tolerates the presence of saliva, although water was found to impair its sealing ability. Laser pre-conditioning significantly decreases microleakage in all cases.
Hydrophilic sealant; Laser; Microleakage; Moisture; Saliva
A wide range of light-cured resin-based sealants is
commercially available for the isolation and defence of occlusal
surfaces of molars and premolars [
]. The majority of these
pit and fissure sealants are hydrophobic materials that bond
to etched air-dried enamel via micromechanically
interlocking tags. Moisture contamination compromises the quality of
adhesion at the sealant–enamel interface, and is a common
challenge encountered in paediatric dentistry where patient
compliance is low . To address this problem, hydrophilic
sealants have appeared on the market during the past
decade which are specifically designed to be placed on moist
Current research has indicated that the application of
laser ablation as an adjunct to traditional phosphoric acid
etching may improve the adhesion, adaptation, retention, and
resistance to microleakage of resin-based sealants [
Recent clinical and in vitro studies support the use of laser
ablation prior to acid etching [
], although these
findings are not unanimously confirmed [
] In practice, the
effectiveness of laser pre-conditioning appears to depend on
many factors relating to the rheological and physicochemical
properties of the particular sealant, lasing parameters and
The principal objectives of this study were to
investigate the impact of laser pre-conditioning and moisture
contamination on the resistance to microleakage of the new
hydrophilic self-adhesive sealant, UltraSeal XT® hydro™
(Ultradent Products, USA) [
], in vitro. The occlusal
surfaces of extracted human molars were either acid etched
(n = 30), or successively lased and acid etched (n = 30).
Ten teeth from each group were then either air-dried,
watercontaminated, or saliva-contaminated prior to sealing
with UltraSeal XT® hydro™. The samples were inspected
for microleakage using fuchsin dye penetration following
3000 thermocycles between 5 and 50 °C. Microleakage
scores were analysed using the Kruskal–Wallis test and
Mann–Whitney U test with Bonferroni adjustment. The
following null hypotheses were tested (p = 0.05): (1) there
is no difference in microleakage among traditionally acid
etched teeth that are either air-dried, water-contaminated or
saliva-contaminated; (2) enamel pre-conditioning by laser
ablation prior to acid etching has no impact on resistance
to microleakage; and (3) the presence of moisture does not
influence microleakage of teeth that have been successively
lased and acid etched.
During this study, the nature of the enamel–sealant
interface was also observed by scanning electron microscopy
(SEM) with energy-dispersive X-ray (EDX) analysis.
Materials and methods
Ethical approval for this project was obtained on the 1st of
October 2014 by the Ethical Committee of Bezmiâlem Vakif
University (reference number 71306642/050-01-04/282).
The study was performed in accordance with the ethical
standards laid down in the 1964 Declaration of Helsinki and
its later amendments.
Sixty sound extracted human molar teeth were obtained
from patients with orthodontic or periodontal problems who
had provided their written informed consent. The teeth were
debrided with manual scaling instruments, cleaned with
bristle brush and pumice paste and stored in distilled water
for up to 5 days. The teeth were then randomly divided into
6 groups, as indicated in Table 1. All samples were prepared
by the same operator.
The occlusal surfaces of Group I teeth were acid etched
for 20 s with 35% phosphoric acid gel (UltraSeal XT®
hydro™, Ultradent Products, USA), rinsed and air-dried.
The UltraSeal XT® hydro™ sealant (Ultradent Products,
USA) was then applied, according to the manufacturer’s
instructions and light cured for 20 s with a BA Optima 10
curing light (BA International Ltd., Northampton,
Group II and III teeth were acid etched, rinsed and
airdried (as outlined above). The occlusal surfaces were then
contaminated with 0.1 cm3 of either distilled water (Group
II) or fresh saliva (Group (III) for 20 s using a dropping
pipette and then lightly dried using a cotton pellet which
was applied for 5 s, prior to the application of the sealant [
Laser conditioning of the occlusal surfaces of Group
IV teeth was carried out using an Er:YAG laser system
(LightWalker®, Fotona, Slovenia) operating at a
wavelength of 2940 nm, a power output of 1.2 W, pulse energy
of 120 mJ and a frequency of 10 Hz. Laser ablation was
carried out using a 600 μm diameter sapphire tip with a
beam spot size of 0.63 mm2, energy density of 19 mJ cm2 at
a working distance of 8 mm at an angle of 90° under water
cooling at 50 cm3 min−1. The teeth were then rinsed with
water, air-dried and acid etched, as described above, prior
to the application and curing of the UltraSeal XT® hydro™
sealant. Groups V and VI teeth were sequentially lased and
acid etched (as outlined above). The occlusal surfaces of
Group V were contaminated with distilled water and Group
VI teeth were contaminated with fresh saliva prior to the
application of the sealant.
Immediately after sealing, the teeth were placed in distilled
water at 37 °C for 24 h and then thermocycled 3000 times
between 5 and 55 °C with a transfer time of 10 s and a dwell
time of 30 s [
]. Subsequent microleakage was assessed
via dye penetration. The teeth were coated with nail
varnish, leaving a 2 mm window around the sealant, and the
roots were embedded in an acrylic resin cylinder (Meliodent,
Bayer Dental, UK). The teeth were then placed in 0.5%
basic fuchsin dye solution for 24 h. Following immersion,
the teeth were rinsed under running tap water for 5 min to
remove excess dye and sectioned in the buccolingual
direction using a water-cooled diamond saw to obtain three slices.
Each of the tooth sample slices was then examined by two
blind investigators under a stereomicroscope (SMZ 800,
Nikon, Japan) at 20× magnification. Microleakage scoring
criteria are listed in Table 2 .
Inter-examiner reproducibility was analysed with the
kappa statistic. Median differences among the
microleakage data for each of the groups were compared using the
Kruskal–Wallis test (p = 0.05). Significant differences were
evaluated using the Mann–Whitney U test with Bonferroni
adjustment (p = 0.05).
Scanning electron microscopy was carried out on the central
slices of the sectioned teeth using uncoated samples attached
to carbon tabs on a JEOL JSM-5410 LV electron microscope
with an Oxford Instruments X-MaxN EDX detector in low
vacuum mode. All back-scattered electron images and EDX
maps were obtained with an accelerating voltage of 20 kV
at a working distance of 20 mm.
The distributions of microleakage scores for each
experimental group are listed in Table 3. An inter-examiner kappa
statistic of 0.90 was obtained for the microleakage
evaluation which indicates high reproducibility.
No significant difference in marginal leakage was found
between the separately acid etched groups that were either
air-dried (Group I) or saliva-contaminated (Group III)
(p = 0.09), although the number of samples that exhibited
no visible microleakage was greater in the former case.
Conversely, Group II teeth that were acid etched and
water-contaminated exhibited significantly higher microleakage than
those of both Group I (p < 0.001) and Group III (p < 0.001).
Hence, the null hypothesis that there is no difference in
microleakage between acid etched samples that were
airdried or moist is rejected in the case of water contamination,
but retained in the case of saliva contamination. None of the
samples in Group II was entirely resistant to dye
penetration, with over half of the specimens in this group exhibiting
maximum penetration to the sealant base. Furthermore, the
sealant partially detached (i.e. ‘debonded’) from the
central section of one of the samples in the water-contaminated
group prior to inspection for microleakage.
In all cases, irrespective of whether the teeth were
airdried or contaminated with either water or saliva, laser
ablation as an adjunct to acid etching was found to significantly
improve resistance to microleakage (p < 0.05). The median
and modal microleakage scores for Groups IV, V, and VI
were zero, indicating that the majority of the lased samples
completely resisted dye penetration. Among these groups,
there were no significant differences in microleakage
irrespective of the presence or absence of either water or saliva.
Therefore, the null hypothesis that enamel pre-conditioning
by laser ablation prior to acid etching has no impact on
microleakage is rejected across all groups. Conversely, the
null hypothesis that water or saliva contamination does not
influence microleakage of sealed teeth that have been
consecutively lased and acid etched is retained.
Scanning electron microscopy
The back-scattered electron image of the enamel–sealant
interface of a random Group I acid etched air-dried tooth
is shown in Fig. 1 along with the corresponding EDX
elemental maps of carbon, barium, silicon and aluminium. In
this group, the sealant was well adapted to the acid etched
air-dried enamel and the barium-, aluminium- and
siliconbearing inorganic filler phases remained homogeneously
distributed throughout the organic resin matrix.
SEM analysis indicated that Group II acid etched
watercontaminated samples were characterised by relatively wide
gaps of several tens of microns between the sealant and the
enamel (Fig. 2). It is likely that the low vacuum pressure of
approximately 15 Pa encountered in the electron microscope
caused the poorly adapted sealant of the water-contaminated
samples to detach from the enamel. On the contrary, the
* Different letters indicate significant differences among the groups (p < 0.05), whereas the same letters
indicate no significant differences (p > 0.05)
sealant was generally observed to be in intimate contact with
the saliva-contaminated enamel of the Group III teeth, with
occasional margins of a few microns (Fig. 3). The inorganic
filler phases were seen to be uniformly distributed
throughout the organic resin matrix of the sealant in Groups II and
Representative back-scattered electron micrographs of
the interfaces of the sealant and the laser pre-conditioned
enamel of Groups IV, V, and VI are shown in Figs. 4, 5, and
6, respectively. In all cases, the sealant was observed to be in
direct contact with the enamel. These samples also exhibited
regions of sub-surface enamel cracking at depths of up to
150 μm from the interface. Some zoning of the inorganic
filler particles at the enamel–sealant interface was noted
for samples in Groups IV and V (Figs. 4, 5, respectively),
although the filler remained homogeneously distributed in
the Group VI specimens. The increased concentration of
the filler at the enamel surface is attributed to the enhanced
surface roughness of the lased enamel [
], which appears
to be mitigated by the lubricating effect of saliva.
UltraSeal XT® hydro™ is a recently marketed
moisture-tolerant, self-adhesive, acrylate-based pit and fissure sealant
which has been developed by Ultradent Products, USA [
It is highly filled with 53% inorganic phases which are
incorporated to confer radiopacity and to improve
wear-resistance. UltraSeal XT® hydro™ is reported to ‘chase’ moisture
into the pits and fissures, thus eliminating moisture-related
failures in adaptation and retention which are common to
hydrophobic sealant materials [
Since this is a new material, at the present time, only one
report could be located in the scientific literature concerning
the relative sealing performance of UltraSeal XT® hydro™
on air-dried or saliva-contaminated primary second molars
]. This research confirms the manufacturer’s claim that
surface contamination by saliva does not affect the sealing
ability of this material; although, the impact of water
contamination is not addressed in the study. Our present results
also confirm that, after 3000 thermocycles between 5 and
55 °C, there is no difference in the extent of dye penetration
when UltraSeal XT® hydro™ is placed on conventionally
etched enamel that is either air-dried or saliva-contaminated.
To best identify any differences in sealing ability among
the various experimental groups, our microleakage study
employed relatively aggressive thermocycling parameters
and 0.5% basic fuchsin solution which is considered the
most effective dye for revealing microleakage [
Conversely, our results indicate that UltraSeal XT®
hydro™ does not effectively tolerate contamination by water
to the same extent that it tolerates saliva. In the case of water
contamination, wide gaps between the sealant and enamel
were noted in all corresponding SEM images, and the
relative resistance to dye penetration was diminished.
The direct clinical relevance of in vitro microleakage tests
is questionable, although it is generally agreed that they can
provide useful information on a dental sealant’s capacity
to maintain good marginal adaptation to prevent bacterial
ingress. The potential clinical significance of this study is
that caution should be applied when considering the nature
of the moisture contamination present at the time of
placement and sealing with UltraSeal XT® hydro™, as, in this
respect, a discrepancy in performance has been identified
between water and saliva.
Recent reports by the authors [
] have demonstrated
that teeth treated with a successive combination of Er:YAG
laser irradiation and acid etching prior to sealing with
UltraSeal XT® hydro™ showed significantly lower microleakage
scores than those that were exclusively acid etched. These
studies included only air-dried enamel and did not consider
the impact of moisture contamination on sealing ability.
From the results obtained in our present study, it appears that
laser pre-conditioning prior to acid etching improves
resistance to microleakage irrespective of whether the enamel is
air-dried or contaminated with either water or saliva. These
findings concur with those of a similar study on another
commercial hydrophilic sealant (Embrace WetBond™,
Pulpdent/Gaba, USA) which demonstrated significant
improvements in resistance to microleakage for laser pre-conditioned
enamel which was contaminated with either water or saliva
There is, currently, no universal agreement regarding
the potential benefits of laser pre-conditioning on the
retention and microleakage of self-adhesive resin-based
fissure sealants. For example, studies by Ciucchi et al. [
Borsatto et al. [
] and Youssef et al. [
] report no
significant differences in hydrophobic sealant microleakage
between teeth that were exclusively acid etched and
those that were consecutively Er:YAG laser ablated and
acid etched. It is speculated that highly viscous sealants
adapt poorly to the enhanced roughness of lased enamel,
which may account for the observed discrepancies in the
A further consideration associated with the application
of laser-pre-conditioning is the occurrence of sub-surface
enamel cracking that has been noted in this and previous
4, 5, 14
]. The presence of sub-surface
microcracking is not visible to the clinician, and is also not readily
observed in vitro using light microscopy, so the reported
incidences are limited to the few studies in which scanning
electron microscopy has been employed. At this point in
time, the significance of laser-induced microcracking with
respect to the longevity of the sealant and the ongoing
welfare of the tooth has not yet been determined.
This study concerns the impact of Er:YAG laser
pre-conditioning and moisture contamination on the microleakage
of a recent hydrophilic sealant (UltraSeal XT® hydro™).
No significant difference was observed in microleakage of
acid etched teeth that were either air-dried or
saliva-contaminated; unlike their water-contaminated counterpart
which exhibited more extensive dye penetration. Laser
pre-conditioning prior to conventional acid etching
significantly increased resistance to microleakage irrespective
of whether the enamel surface was moist or dry. Scanning
electron microscopy (SEM) demonstrated good adaptation
in all cases with the exception of water-contaminated acid
etched teeth which exhibited relatively wide gaps between
the sealant and enamel. SEM analysis also revealed
subsurface cracking of the enamel of teeth subjected to laser
Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of
Open Access This article is distributed under the terms of the Creative
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credit to the original author(s) and the source, provide a link to the
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