|Year : 2012 | Volume
| Issue : 4 | Page : 288-292
Comparative evaluation of shear bond strength of three pit and fissure sealants using conventional etch or self-etching primer
JK Dhillon1, A Pathak2
1 Division of Pedodontics and Preventive Dentistry, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India
2 Department of Pedodontics and Preventive Dentistry, Government Dental College and Hospital, Patiala, India
|Date of Web Publication||19-Mar-2013|
J K Dhillon
Division of Pediatric and Preventive Dentistry, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aims: To compare the shear bond strength of three different pit and fissure sealants and evaluate the effect of a self-etching primer on shear bond strength of these three pit and fissure sealants as compared to conventional etch. Materials and Methods: One hundred and eighty newly extracted non carious permanent molars were selected. The mesial or distal surface was cleaned and polished to obtain a flat enamel surface. The specimens were randomly divided into three groups of sixty teeth each and each group further divided into two subgroups of thirty each. The teeth in one subgroup were treated with 37% phosphoric acid etchant and the other subgroup with self-etching primer before formation of a sealant button using a Teflon mold. Then specimens were tested in a shear mode at a crosshead speed of 1 mm/minute. Results: The average bond strengths using conventional etch were: (1) Eco-S = 13.0986 MPa; (2) ClinPro = 13.4317 MPa; and (3) Dyract Flow = 13.0292 MPa and with self - etching primer were: (1) Eco-S = 19.7011MPa; (2) ClinPro = 20.8069 MPa; and (3) Dyract Flow = 19.5207 MPa. The values with self-etching primer were higher than and statistically different from those with the conventional etch system (student t test, P < 0.005). Conclusion: It was concluded that the bond strengths of self - etching primer in conjunction with pit and fissure sealant, exceeded those of conventional etch.
Keywords: Compomer, pit and fissure sealant, self-etching primer, shear bond strength
|How to cite this article:|
Dhillon J K, Pathak A. Comparative evaluation of shear bond strength of three pit and fissure sealants using conventional etch or self-etching primer. J Indian Soc Pedod Prev Dent 2012;30:288-92
|How to cite this URL:|
Dhillon J K, Pathak A. Comparative evaluation of shear bond strength of three pit and fissure sealants using conventional etch or self-etching primer. J Indian Soc Pedod Prev Dent [serial online] 2012 [cited 2020 Feb 18];30:288-92. Available from: http://www.jisppd.com/text.asp?2012/30/4/288/108922
| Introduction|| |
Pit and fissure caries account for 80% of total caries experience. , The morphology of pits and fissures provides an environment for plaque and bacteria retention. Moreover, enamel is thinner in pits and fissures, which allows accelerated demineralization into dentin. This is especially true for erupting teeth that are in the process of maturation. The high susceptibility of pits and fissures to caries provides the rationale for protection of these areas.
Sealant has been described as a material introduced into the occlusal pits and fissures of caries-susceptible teeth, forming a micromechanically bonded protective layer cutting access of caries-producing bacteria from their source of nutrients.  The ability of fissure sealants to prevent caries has been demonstrated by several studies ,,, and is related to sealant retention. , The retention rate of a pit and fissure sealant is directly related to the micromechanical bond between the sealant and enamel. Shear bond strength measures the ability of sealant to bond to tooth structure. Higher shear bond strength is equated with enhanced performance. 
The self-etching system does not need an "etch and rinse" phase which not only lessens clinical application time but also reduces technique sensitivity. Another important advantage of self-etching primer is that infiltration of adhesive resin occurs simultaneously with the etching process. Self-etching primer can be used for sealant application to shorten the treatment time and complexity by eliminating a separate step for application of bonding agent after acid etching. The present study was undertaken to evaluate and compare the shear bond strength of three different pit and fissure sealants to enamel using conventional etch or a self-etching primer.
| Materials and Methods|| |
A total of 180 caries-free human permanent molars extracted for periodontal reasons were collected. The teeth were cleaned by soaking them in 5% sodium hypochlorite. The remaining periodontal tissue and calculus was removed. The crown surfaces of the teeth were cleaned and polished with pumice slurry.
Grouping of samples
The teeth were randomly divided into three groups of 60 teeth each, based on the pit and fissure sealant applied. Each group was further divided into two subgroups of 30 teeth each, depending upon whether conventional etch or self-etching primer was used.
Group I: Unfilled resin-based sealant (Eco-S)
Subgroup IA: 37% phosphoric acid (Scotchbond)
Subgroup IB: Self-etching primer (Xeno III)
Group II: Fluoride releasing resin-based sealant (ClinPro)
Subgroup IIA: 37% phosphoric acid (Scotchbond)
Subgroup IIB: Self-etching primer (Xeno III)
Group III: Compomer-based sealant (Dyract Flow)
Subgroup IIIA: 37% phosphoric acid (Scotchbond)
Subgroup IIIB: Self-etching primer (Xeno III)
The mesial or distal surface of the crown of each tooth was polished with silicon carbide paper. The polished surface was etched with 37% phosphoric acid for 20 s, rinsed for 20 s, and then air dried in subgroups IA, IIA, and IIIA. The polished surface of each tooth was treated with self-etching primer (Xeno III) which was mixed, applied, and light cured as per manufacturer's instructions in subgroups IB, IIB, and IIIB. An adhesive tape was taken and a circular hole of 3 mm diameter in the middle was made using the punch. The etched surface was covered with this adhesive tape. A Teflon mold of 3 mm diameter and 3 mm height was placed over the circular hole and the respective sealant in each group was injected in the mold and light cured as per manufacturer's instructions to obtain a sealant button.
The specimens of each group were stored in distilled water in separate containers. Before testing, each specimen was embedded in acrylic resin block with the treated surface exposed. The specimens were then subjected to shear bond strength testing.
Shear bond strength testing
Each specimen was placed in the Universal testing machine so that the treated surface was parallel to the shearing rod of the Universal testing machine [Figure 1]. Load was applied at a cross-head speed of 1 mm/min. This was repeated for all the specimens.
The readings were obtained in kilograms and recorded. These readings were then converted into Newtons by multiplying the reading by 9.81 (1 kg = 9.81 N). The shear bond strength of the pit and fissure sealants in N/mm 2 (MPa) was calculated using the formula:
Bond strength (MPa) = load/area,
where area of the bonding surface in mm 2 was obtained with the following formula:
Area = πr 2 ,
where r is equal to the radius of the sealant button in mm and π is a constant with value equal to 3.14. 
Shear bond strength of all the specimens was calculated and recorded. Then the compiled data were subjected to statistical analysis.
| Results|| |
The mean (±SD) values of the shear bond strength of the three materials etched with either conventional etch or self-etching primer in this study are presented in [Figure 2].
|Figure 2: Mean shear bond strength of different pit and fissure sealants using conventional etch or self-etching primer|
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Analysis of variance (ANOVA) test was applied to compare the shear bond strength of the three different pit and fissure sealants [Table 1]. No significant difference was observed in the shear bond strength between the three different sealants.
|Table 1: Mean difference in the shear bond strength of various pit and fissure sealants using analysis of variance test|
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Statistical analysis was performed to compare the shear bond strength of the pit and fissure sealants with conventional etch or with the self-etching primer (Xeno III) using Student's t-test [Table 2]. It was observed that the pit and fissure sealants used in this study showed higher shear bond strength values when self-etching primer was used as compared to conventional etch and the difference was statistically significant (P < 0.05).
|Table 2: Mean difference in shear bond strength of various pit and fissure sealants using conventional etch or self-etching primer using student's t test|
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| Discussion|| |
No significant difference was observed in our study in the bond strength of resin-based sealants and compomer-based sealants, which is in concurrence with the study conducted by Papacchini et al.  Dyract Flow pit and fissure sealant used in this study is a flowable compomer. It combines the properties of both glass ionomer and composite resin. It has good flow similar to that of unfilled resin-based sealants. The methacrylate resin monomers in Dyract Flow promote diffusion of the material onto tooth surface. The hydrophilic carboxylate groups of the glass ionomer particles and the phosphate group of resin monomers are responsible for its good wetting ability.  These factors are responsible for the bond strength of Dyract Flow being comparable with resin-based sealants. The results showed that there was no significant difference between the bond strength of the two resin-based sealants. This is in accordance with the studies conducted by Park et al.  and Marcushamer et al.,  which compared the shear bond strength of fluoride-releasing resin-based pit and fissure sealants and non-fluoridated resin-based pit and fissure sealants. They observed in their respective studies that there was no difference in the bond strength amongst the different resin-based pit and fissure sealants.
Al-Sarheed  concluded in an in vitro study that shear bond strength of pit and fissure sealants was higher with self-etching primer as compared to conventional etch, which is in concurrence with the results of this study. It could be due to the primer which allows the pit and fissure sealant to flow and penetrate better onto enamel and form a thick hybrid layer, thus improving bonding. This can be attributed to the following reasons:
In the conventional etch technique, etching of the enamel with phosphoric acid is done followed by rinsing and drying. After this treatment, the tooth must be maintained in an isolated, dry condition so that there is no contamination.  Correr  and Barroso et al.  observed that contamination of tooth surface decreased the bond strength, and hence the retention of pit and fissure sealants. Rinsing the tooth after acid etching can be unpleasant and become a source of disruptive behavior, particularly in young children. Self-etching primers do not require a separate etch and rinse phase, which makes the time involved in sealant placement less.
- The self-etching primer helps to improve the rheology of the fissure sealant, which allows it to flow better onto enamel, thus improving bonding. 
- Methacrylate components such as HEMA (2-Hydroxyethyl methacrylate) present in self-etching primer are responsible for monomer infiltration.  Polymerization of this primer causes formation of a thick hybrid layer. 
- Self-etching primer (Xeno III) contains PEM-F (pentamethacryloxyethyl cyclophosphazen mono Fluoride) which is a strong cross-linking monomer that contributes to cohesive strength. 
- Pyro-EMA (Tetramethacryloxyethyl pyrophosphate) is a phosphate-containing polymer present in self-etching primer (Xeno III) and may contribute to adhesion by forming chemical bond between calcium present in hydroxyapatite and methacrylate monomer in pit and fissure sealants. 
In the conventional etch technique, after acid etching, the sealant flows onto the etched surface and forms resin tags. After polymerization, these tags harden. The bond formed between the sealant and tooth is mechanical. Hitt and Feigal  first reported the benefits of adding a bonding agent layer between the etched enamel and the sealant as a way of optimizing bond strength. Choi et al.  and Tulunoglu et al.  observed that pit and fissure sealants showed higher shear bond strength when adhesive was used. Self-etching primers contain methacrylate components such as HEMA which infiltrate the enamel porosities created by acidic monomers and also bond with the methacrylate resins present in pit and fissure sealants. This increases the bond strength of pit and fissure sealants to enamel.
| Conclusion|| |
Results of this study showed that there was an increase in the shear bond strength of pit and fissure sealants when self-etching primer was used as compared to conventional etch with phosphoric acid. It could be due to the primer which allows the pit and fissure sealant to flow and penetrate better onto enamel and form a thick hybrid layer, thus improving bonding. The self-etching primer (Xeno III) contains Pyro-EMA which may contribute to bond strength by forming chemical bond between calcium present in hydroxyapatite and methacrylate monomer in pit and fissure sealants. However, long-term clinical trials as well as in vitro studies on larger samples and at a larger scale need to be undertaken using different surface treatments for sealant application before drawing any definite conclusions.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]