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nt Er,Cr:YSGG Laser Pretreatment of Primary Teeth for e ss e n z Bonded Fissure Sealant Application: A Quantitative Microleakage Study S. Burcak Cehrelia/H. Cem Gungorb/Erdem Karabulutc
Purpose: Laser pretreatment of dental hard tissues prior to preventive or restorative procedures has been a subject of research. Unground primary enamel bears a prismless superficial layer which is known to be acid resistant. This in vitro study was conducted in order to evaluate the potential use of Er,Cr:YSGG laser in the pretreatment of occlusal surfaces of primary teeth prior to bonded fissure sealant application. Materials and Methods: Occlusal surfaces of human primary mandibular molars were used (n =140). After pretreatment with Er,Cr:YSGG laser (group A) or not (group B), occlusal fissures were treated with one of the following in each of 7 subgroups (n = 10): 1. phosphoric acid-etch only; 2. Clearfil SE Bond; 3. FL Bond; 4. Adper Prompt L-Pop; 5. NRC+Prime & Bond NT; 6. One-Up Bond F; 7. Xeno III. All teeth were sealed with Fissurit F. The specimens were thermocycled (1000 times) and stored thereafter in distilled water at 37°C for 8 months. Following immersion in 0.5% basic fuchsin solution, three bucco-lingual sections were made from each tooth. They were digitally photographed and the extent of dye penetration along the enamel-sealant interface was measured (in mm) with image analysis software. Results: There was no difference between the Er,Cr:YSGG laser pretreated group (group A) and the nonlased group (group B) (p > 0.05). The lowest microleakage values were observed in subgroups A1 and B1. Within the laser pretreated group, subgroups A1, A4, and A5 showed lower microleakage scores when compared to subgroups A2, A3, A6, and A7 (p < 0.05). As for the nonlased group, subgroups B1, B3, B4, and B5 demonstrated significantly lower microleakage scores than subgroups B2, B6, and B7 (p < 0.05). Conclusion: Er,Cr:YSGG laser pretreatment was not found to influence the resistance to microleakage of bonded fissure sealant application in primary teeth. Keywords: primary teeth, laser, Er,Cr:YSGG laser, fissure sealant, microleakage, self-etching adhesive. J Adhes Dent 2006; 8: 381-386.
D
ue to their complex morphology, occlusal pits and fissures are the most susceptible areas to development of caries, accounting for more than 85% of the caries-affected tooth surfaces.20,49 For this reason, pit and fissure sealants have been widely used for more than 30 years to prevent caries in pits and fissures of occlusal tooth surfaces.40,44 Sealants are also capable of inhibiting further progress of incipient enamel lesions under demineralizing conditions in vitro1,3,41,42 or as long as 10 years in vivo.31
a Research Assistant, Department of Pediatric Dentistry, Baskent University,
Ankara, Turkey. b Assistant Professor, Department of Pediatric Dentistry, Hacettepe University,
Ankara, Turkey. c Research Assistant, Department of Biostatistics, Hacettepe University,
Ankara, Turkey. Reprint requests: Dr. S. Burcak Cehreli, 11. Sokak No. 26, Bahcelievler, 06490 Ankara, Turkey. Fax:+90-312-215-2962. e-mail:
[email protected]
Vol 8, No 6, 2006
Submitted for publication: 24.01.06; accepted for publication: 10.04.06.
Today, it is well recognized that the success of fissure sealants is based on their retention and resistance to microleakage, both of which depend on the quality of adhesion between the sealant material and enamel.45 Conventionally, enamel pretreatment with various concentrations of phosphoric acid has been the standard method for creating microporosities that serve for the retention of the sealant material.38 Additionally, phosphoric acid pretreatment increases the wettability of enamel and provides an antibacterial effect.1,4 The use of hydrophilic adhesive resins as an intermediate layer under sealant materials has been suggested with the rationale of reducing the risk of sealant failure due to saliva contamination.47 Later, the effectiveness of the “bonded sealant” concept was substantiated in vitro and in vivo.12,21 The recent introduction of self-etching adhesives may provide potential improvement of the bonded sealant technique, as these adhesive systems eliminate a separate etching-rinsing-drying procedure,36 thereby reducing the risk of saliva contamination as well as the treatment time and the 381
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Noncarious human mandibular primary molars, extracted for orthodontic reasons, were collected and stored in saline solution for up to 1 month at 4°C. After surface debridement with a hand-scaling instrument and cleaning the pits and fissures with a low-speed water-cooled rotating brush, the teeth were examined at 20X under a dissecting microscope to discard those with any visible structural defects, cracks or incipient lesions. One hundred forty intact teeth were selected and assigned randomly to 2 main groups (n = 70 each). In the first group (group A), occlusal fissures were irradiated with an Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) hydrokinetic laser system (Millenium System, Biolase Technology; San Clemente, CA, USA). Before operation, the power output was set at 3.5 W (output parameters: wavelength = 2.78 μm, pulsed with duration from 140 to 200 μs and a repetition rate of 20 Hz). Air and water was sprayed through the handpiece at a level of 85% water and 90% air to prevent enamel surfaces from overheating. The laser beam was delivered in noncontact mode, with the handpiece positioned 1 mm above and perpendicular to the fissures. The duration of exposure depended on the time needed to evenly guide the laser beam across the pits and fissures to be irradiated. Fissures were then rinsed and air dried. In the second group (group B), occlusal fissures did not receive laser pretreatment. In each main group, specimens were assigned randomly to 7 subgroups (n = 10 each). The materials and procedures applied in each subgroup are as follows. 382
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MATERIALS AND METHODS
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be • Subgroup 1: 37% orthophosphoric acid (Adper Etchant, ha 3M/ESPE; Seefeld, Germany). Occlusal surfaces werelten nt etched for 60 s, rinsed for 15 s, and air dried essfore10 nzs. • Subgroup 2: A two-step self-etching adhesive system (Clearfil SE Bond, Kuraray; Osaka, Japan). • Subgroup 3: A two-step self-etching adhesive system (FL Bond, Shofu; Kyoto, Japan). • Subgroup 4: A two-step self-etching adhesive system (Adper Prompt L-Pop, 3M/ESPE). • Subgroup 5: A nonrinse conditioner (NRC, Dentsply/DeTrey; Konstanz, Germany) and an acetone-based totaletch adhesive (Prime&Bond NT, Dentsply/DeTrey). • Subgroup 6: A one-step self-etching adhesive system (One-Up Bond F, Tokuyama; Tokyo, Japan), • Subgroup 7: A one-step self-etching adhesive system (Xeno III, Dentsply/DeTrey).
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need for patient compliance. Peutzfeld and Nielsen38 showed that the shear bond strength of a light-cured sealant material bonded with a self-etching adhesive yielded equivalent bond strength to that applied over phosphoric acidtreated enamel at 1 week and after 1 year. However, the authors did not investigate the effect of adhesive application on microleakage. The effect of laser irradiation on dental hard tissues has been a subject of increasing research interest. Especially Nd:YAG and Er:YAG laser systems have been investigated in a vast field of applications, including cavity preparation and alteration of enamel and dentin to facilitate their receptiveness to adhesive procedures.7,11 Laser irradiation of dental hard tissues leads to the formation of more stable and less acid-soluble compounds, thus reducing susceptibility to acid attack and caries.20,46 It has also been suggested that laser etching might create remineralization microspaces that trap free ions,35 while providing an antibacterial effect.9,32 These favorable effects appear to be potentially useful in the pretreatment of pits and fissures prior to sealant application, particularly in the case of unground primary enamel, which bears an acid-resistant prismless superficial layer.4 This in vitro study aimed to evaluate the effect of Er,Cr:YSGG laser pretreatment on the microleakage of a fissure sealant bonded with self-etching adhesives on primary teeth. The null hypothesis tested was that Er,Cr:YSGG laser pretreatment of primary enamel does not affect the microleakage of bonded fissure sealants.
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Manufacturers’ recommendations were followed during application of bonding agents (Table 1). Following these procedures, all teeth were sealed with the same fissure sealant material (Fissurit F, Voco; Cuxhaven, Germany), and photopolymerized with a conventional QTH curing unit (Optilux 501, Kerr; Orange, CA, USA) for 40 s at 480 mW/cm2. A new curing unit was used to ensure complete polymerization. Immediately after curing, the teeth were placed in deionized water at 37°C for 24 h and thermocycled (1000 times at 5 ± 2°C to 55 ± 2°C; dwell time = 15 s and transfer time = 10 s). Finally, the teeth were stored in distilled water at 37°C for 8 months. The water was changed every week.29 Microleakage was assessed with a conventional dye-penetration method. First, the apices were sealed with sticky wax and the specimens were coated with two consecutive layers of nail varnish up to 1 mm from the sealant margins. Specimens were then immersed in 0.5% basic fuchsin solution (Wako Pure Chemical Industry; Osaka, Japan) for 24 h. After thoroughly rinsing with distilled water, the specimens were air dried and embedded in epoxy resin (Struers; Copenhagen, Denmark). Three parallel longitudinal sections were made through the occlusal surfaces using a water-cooled low-speed diamond saw (Isomet, Buehler; IL, USA) in the bucco-lingual direction. A digital photograph of each section was obtained at 20X (1280 x 1024 resolution) under a stereomicroscope (Olympus; Tokyo, Japan). The images were transferred to an IBM-compatible PC. Image analysis software (Scion Image; Frederick, MD, USA) was used to measure (in mm) the extent of buccal and lingual dye penetration along the enamel-sealant interface. The microleakage value for each section was calculated by dividing the sum of buccal and lingual dye penetration values by the sum of the lengths of buccal and lingual enamel-sealant interfaces10 (Fig 1). The measurements were made by one calibrated operator, blinded to treatment groups. The microleakage value for each specimen, and thereafter, for each tooth and subgroup was calculated as the mean ± SD. Preliminary analysis of the data showed that not all data for the experimental groups conformed to a normal distribution (Kolmogorov-Smirnov test) and homogenity of variances (Levene’s test). Thus, further statistical analysis was performed with nonparametric test methods, using the Kruskal-Wallis test and Mann-Whitney U-test with Bonferroni The Journal of Adhesive Dentistry
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Table 1 Composition and application mode of the tested materials
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Product
Composition
Application
Liquid A Purified water, ethanolurethane dimethacrylate resin, butylated hydroxytoluene, highly dispersed silicon dioxide
Liquid B Phosphoric acid, modified polymethacrylate resin, monofluorophosphazene, modified methacrylate resin, UDMA butylated hydroxitoluene, ethyl- 4 -dimethylaminobenzoate
Adper Prompt L-Pop (3M-ESPE; Seefeld, Germany)
Liquid 1 Methacrylated phosphoric esters, bis-GMA initiators based on camphorquinone, stabilizers
Liquid 2 Water, HEMA Polyalkenoic acid, stabilizers
Clearfil SE Bond (Kuraray; Osaka, Japan)
Primer MDP, HEMA, hydrophilic dimethacrylate
Adhesive MDP, bis-GMA, HEMA, silanated colloidal silica
Bonding agent A Phosphoric monomer propanedioic acid, 2-methyl1-oxo-2-propenyl oxy decyl, bis-GMA, multifunctional methacrylic monomers co-initiator
Bonding agent B HEMA monofunctional monomers, silicate filler, dye-sensitizer, borate derivative, water
Xeno III (Dentsply DeTrey; Konstanz, Germany)
One-Up Bond F (Tokuyama; Tokyo, Japan)
NRC (Dentsply DeTrey)
FL Bond (Shofu, Tokyo, Japan)
Itaconic acid, maleic acid, carboxylic acid, water, solvent
Primer Primer A: water, acetone photoinitiator Primer B: 4-AET, HEMA, 4-AETA, initiator
Adhesive 4-AET, HEMA, UDMA, TEG-DMA, SiO2 microfillers
se nz
Mix primer A&B 50:50 ratio for 5 s, apply, leave 20 s, gently air dry, light cure for 10 s
Apply scrubbing continuously for 15 s, gently air dry, light cure for 10 s
Apply primer and leave for 20 s, gently air dry, apply adhesive, light cure for 10 s
Mix A&B, apply, leave 20 s, gently air dry, light cure for 1 s
Apply and leave for 20 s, air dry for 15 s
Mix primer A&B 50:50 ratio, apply, leave 10 s and air dry Apply adhesive, light cure for 10 s
HEMA: 2-hydroxyethylmethacrylate; bis-GMA, bisphenol-A-dimethacrylate; UDMA: urethane dimethacrylate; 4-AET: 4-acryloyloxyethyl trimellitate; 4-AETA: 4-acryloxyetyl trimellitate anhydride; MDP: 10-methacryloyloxydecyl dihydrogen phosphate; PENTA: dipentaerythritol penta acrylate monophosphate.
corrections for pair-wise multiple comparisons. The level of significance was set as α = 0.05.
RESULTS Regardless of the pretreatments or bonding procedures employed, all subgroups demonstrated microleakage. Comparisons between the lased and nonlased version of each pretreatment protocol (eg, subgroups A1 and B1) showed that Er,Cr:YSGG laser pretreatment had no significant effect on the marginal seal (p > 0.05). Overall, the lowest microleakVol 8, No 6, 2006
age values were obtained in specimens that received Er,Cr:YSGG pretreatment supplemented with phosphoricacid etching (subgroup A1) and phosphoric-acid etching only (subgroup B1). Levels of dye penetration between these two groups did not differ significantly (p > 0.05). The microleakage values of the experimental groups are presented in Table 2. Within the laser-irradiated specimens, subgroups A1 (phosphoric-acid etching only), A4 (Adper Prompt L-Pop), and A5 (NRC + Prime & Bond NT) displayed similar microleakage values (p > 0.05), with those of A1 displaying the least amount of microleakage. Subgroups A2 (Clearfil SE Bond), 383
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be miXeno III (subgroup B7) demonstrated significantly higher ha croleakage values than subgroups B1, B3,n B4 and B5 (p 0.05). One-Up Bond F and Xeno III almost equally yielded the highest microleakage scores within the nonlased specimens (Table 2).
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DISCUSSION
Fig 1 Scoring system utilized for the evaluation of microleakage (modified from Duangthip and Lussi10). A+B (mm) = length of dye penetration along the lingual and buccal walls. C+D (mm) = length of sealant-tooth interface. The proportion of A+B and C+D provides the mean microleakage value for the section. (*=adhesive resin).
A3 (FL Bond), A6 (One-Up Bond F), and A7 (Xeno III) had significantly greater microleakage values than subgroups A1, A4, and A5 (p < 0.05). The difference between the subgroups A2, A3, A6, and A7 was not statistically significant (p > 0.05). Among laser-irradiated specimens, subgroup A7 (Xeno III) displayed the highest microleakage values (Table 2). As for the nonlased specimens, subgroups B1 (phosphoric-acid etching only), B3 (FL Bond), B4 (Adper Prompt LPop), and B5 (NRC + Prime & Bond NT) showed similar microleakage values (p > 0.05). Fissures treated with Clearfil SE Bond (subgroup B2), One-Up Bond F (subgroup B6), and
The clinically undetectable passage of bacteria, fluids, molecules, or ions between the cavity wall and the applied restorative material has been defined as microleakage.28 The success of a restorative or preventive procedure (eg, sealant application) may be undermined if the applied material cannot resist microleakage. Failure results in initiation and/or progression of caries which, in turn, lowers the cost effectiveness of the procedure.44 Microleakage tests are useful methods to evaluate the sealing performance of adhesive systems.6 Among different methods employed, dye penetration measurements on sections of restored teeth are the most commonly used technique. In the present study, three sections were made through each sealant to increase the reliability of measurements.39 This technique was combined with image analysis in order to obtain quantitative results instead of a conventional subjective scoring. A relative merit of this objective approach compared with a subjective scoring system was to discard the need for scoring by separate evaluators and for consensus scoring in borderline cases, as well as statistical procedures with regard to interexaminer reliability. The effect of water storage on the embrittlement (plasticization) of resin-based biomaterials and on the deterioration of resin-tooth bonds is well established.2,15,27 In the present study, an 8-month water storage of the test specimens following thermocycling was utilized as a similar approach to promote degradation of resin-enamel bonds.34 During this
Table 2 Microleakage values obtained in the study Group
Subgroup
Fissure pretreatment
(n)
Mean ± SD (mm)
A
1a 2b 3b 4a 5a 6b 7b
Laser irradiation+37% phosphoric acid Laser irradiation+Clearfil SE Bond Laser irradiation+FL Bond Laser irradiation+AdperPrompt L-Pop Laser irradiation+ NRC+Prime & Bond NT Laser irradiation+One-Up Bond F Laser irradiation+ Xeno III
10 10 10 10 10 10 10
0.12 ± 0.06 0.41 ± 0.04 0.42 ± 0.16 0.25 ± 0.06 0.23 ± 0.07 0.54 ± 0.12 0.66 ± 0.07
B
1a 2b 3a 4a 5a 6b 7b
37% phosphoric acid Clearfil SE Bond FL Bond AdperPrompt L-Pop NRC+Prime & Bond NT One-Up Bond F Xeno III
10 10 10 10 10 10 10
0.13 ± 0.06 0.42 ± 0.03 0.22 ± 0.04 0.14 ± 0.08 0.23 ± 0.04 0.65 ± 0.10 0.65 ± 0.07
Different superscripts (a, b) show statistically significant differences between subgroups.
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t es etchic acid esters in self-etching adhesives form shallower se nz ing patterns than those observed after etching with phosphoric acid.36 Perry and Rueggeberg26 have observed a greater incidence of microleakage related to sealants placed in extracted permanent molars conditioned with Prompt LPop as compared with conventional acid etching. The use of of Xeno III on previously etched (phosphoric acid 35%) intact enamel and its effect on sealant microleakage and tag formation have been studied by Celiberti and Lussi.37 The authors reported that the best results were obtained by etching fissures with phosphoric acid for 60 s, and the additional use of Xeno III did not improve fissure sealing. Using Xeno III solely as a fissure sealant on permanent teeth was also not recommended.48 FL Bond on nonlased enamel (subgroup B3) had a comparable performance to that of acid-etched specimens. However, significantly higher microleakage scores were observed with its use on lased enamel (subgroup A3). This somewhat confusing result may be explained by the composition of FL Bond and its interaction with lased enamel. FL Bond contains 4-acryloxyethyl trimellitic acid (4-AET), an adhesionpromoting monomer, which bonds to dental hard tissues via ionic interaction with hydroxyapatite.19,24 Scanning electron microscopy and x-ray microanalysis (SEM-XMA) studies on bonded interfaces of a self-etching primer containing 4-AET have demonstrated a considerable amount of calcium entrapped in the hybrid zone.19 The ionized carboxyl groups in the 4-AET monomer is capable of combining with Ca2+ of the original and remnant apatite crystallites within the toothresin adhesive interface to form insoluble salts.19 This may explain the better performance of FL Bond on nonlased enamel. Nevertheless, laser irradiation can significantly alter the chemical composition of superficial enamel, leading to formation of metastable crystalline products. such as ß-tricalcium phosphate (ß-TCP),14,25,50 resulting in a reduction of previously available surface Ca2+.30 As a result, application of FL Bond over the lased enamel could not further promote ionic interaction by virtue of 4-AET, and thus presumably resulted in a compromised sealing performance when compared to its nonlased counterpart. The present study failed to demonstrate improvement of microleakage resistance by Er,Cr:YSGG laser pretreatment, leading to the acceptance of the null hypothesis. Further studies are required to provide evidence for acquired caries resistance of lased fissures under bonded sealants. If this proved to be true, Er,Cr:YSGG laser pretreatment could signficantly aid in the prevention of inevitable microleakage-related secondary caries, which cannot be prevented with today’s conventional acid-pretreatment techniques. i
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period, the storage medium (water) was changed every week. Using this protocol, Kitasako et al29 demonstrated dramatic loss of bond strength compared to specimens stored in water for 1 year without changing. The present study evaluated, in terms of microleakage, the quality of fissure sealing of occlusal surfaces of primary teeth obtained by self-etching adhesive and phosphoric acid usage with or without Er,Cr:YSGG laser pretreatment. Hardtissue cutting lasers have been introduced for use in preventive and restorative dentistry, and their interactions with dental tissues have been studied.17,18,23 Er,Cr:YSSG laser systems, in conjunction with an air-water spray, have been found effective for caries removal and Class I, III and V cavity preparations.18 In a study by Gutknecht et al,17 the extent of microleakage in composite fillings was highest in permanent teeth prepared with Er,Cr:YSGG laser without additional etching. Thus, the authors recommended Er,Cr:YSGG laser preparation to be supplemented with acid etching. A contradictory result has been reported by Hossain et al,23 who compared the microleakage of composite resin restorations in primary teeth prepared with either Er,Cr:YSGG laser or conventional diamond burs. They concluded that laserprepared cavity surfaces facilitate good adhesion with restorative materials and that the acid-etching step could be avoided if laser was used. Studies on the microleakage of fissure sealants have also displayed different results.3,33 Borsatto et al3 reported no significant difference between phosphoric acid-etched plus Er:YAG-lased and acid-etched primary enamel, concluding that laser irradiation did not eliminate the need for acid etching. On the other hand, Moshonov et al33 reported no difference in microleakage of sealants placed with lasing or acid etching in permanent teeth. In the present study, the use of Er,Cr:YSGG laser prior to bonded fissure sealant application did not significantly improve microleakage resistance in primary teeth. Self-etching adhesives contain nonrinse acidic monomers that condition and prime enamel simultaneously. With the rinsing step omitted, the application time and technique sensitivity of the bonding procedure is reduced. The application of the self-etching primer is, in its most conventional form, followed by the application of a hydrophobic bonding resin. The simplified form of this procedure combines the primer with the adhesive resin, known as “one-step self-etching adhesives” or “all-in-one adhesives”.16 Except for Adper Prompt L-Pop and FL Bond (only in nonlased fissures), the self-etching adhesives of this study could not produce satisfactory results when compared to those of phosphoric acid and the total-etch adhesive system used (NRC + Prime & Bond NT). Several in vitro studies have discouraged the use of selfetching adhesives on intact enamel due to significantly lower bond strengths; greater microleakage, and shallow etching patterns that prevent good penetration of the bonding resin.5,8,26,37 Insufficient etching can be attributed to diminishing abilities of decalcification due to total inactivation of the acid in contact with the enamel surface. Together with the presence of dissolved calcium phosphates, which are not removed by rinsing when using self-etching systems, this might result in a lower resistance of the bond to thermomechanical stress, and thus promote the development of
C All eR echCehreli et al te vo r e marginal openings of the fissure seal.43 Especially inbfisha sures of the occlusal surface, the methacrylated n phosphor- lten
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Clinical relevance: Pretreatment of primary enamel with Er,Cr:YSGG laser does not improve the sealing ability of fissure selants.
The Journal of Adhesive Dentistry
