|Year : 2007 | Volume
| Issue : 4 | Page : 169-173
Retention and penetration of a conventional resin-based sealant and a photochromatic flowable composite resin placed on occlusal pits and fissures
FG Aguilar1, B Drubi-Filho1, LA Casemiro2, M.G.C Watanabe3, F.C.P Pires-de-Souza4
1 Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil
2 Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, and Professor, School of Dentistry, University of Franca, Franca, Brazil
3 Department of Pediatric Clinics, Preventive and Social Dentistry, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
4 Department of Dental Materials and Prosthodontics, Faculty of Dentistry of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
Department Dental Materials and Prosthesis, Faculty of Dentistry Odontologia of Ribeirão Preto, University of São Paulo, Av. Do Café, S/N, 14040-904, Ribeirão Preto, São Paulo
Source of Support: None, Conflict of Interest: None
| Abstract|| |
This study compares the retention and penetration of a conventional resin-based sealant (Fluroshield) and a photochromatic flowable composite resin (Tetric Flow Chroma) placed on occlusal pits and fissures and submitted to thermal or chemical cycling regimens. Penetration assessment - ten premolars were sealed with each material, isolated (except for the sealed surface) and immersed in 0.2% Rhodamine B. The teeth were serially sectioned in a mesiodistal direction. The images of the sections were digitized and analyzed (ImageLab). The distance between the most superficial and the deepest points on the occlusal central groove was calculated to determine the groove's total depth. The length of the central groove filled with the sealant was divided by its total depth to obtain the percentage of sealing of the occlusal groove. Retention assessment - 30 premolars were sealed, their occlusal surfaces were photographed and the area occupied by the sealing materials was demarcated (ImageLab). The teeth were submitted to different treatments: thermocycled, stored in artificial saliva and immersed in acetic acid and saliva (10 cycles/day protocol for 30 days). New photographs were taken to assess the final area occupied by the materials. The difference between the final and initial area was calculated to obtain the material loss. The data was analyzed (two-way anova and Tukey's test P < 0.05). Both materials presented similar penetration of the occlusal central groove. After thermal and chemical cycling, the materials did not differ with respect to retention, except for immersion in acetic acid. In this case, Tetric Flow Chroma presented greater retention than Fluoroshield.
Keywords: Flowable composite resin, pit-and-fissure sealants, retention
|How to cite this article:|
Aguilar F G, Drubi-Filho B, Casemiro L A, Watanabe M, Pires-de-Souza F. Retention and penetration of a conventional resin-based sealant and a photochromatic flowable composite resin placed on occlusal pits and fissures. J Indian Soc Pedod Prev Dent 2007;25:169-73
|How to cite this URL:|
Aguilar F G, Drubi-Filho B, Casemiro L A, Watanabe M, Pires-de-Souza F. Retention and penetration of a conventional resin-based sealant and a photochromatic flowable composite resin placed on occlusal pits and fissures. J Indian Soc Pedod Prev Dent [serial online] 2007 [cited 2019 May 26];25:169-73. Available from: http://www.jisppd.com/text.asp?2007/25/4/169/37012
| Introduction|| |
In spite of traditional and innovative prevention methods, dental caries, an infectious, microbial and multifactorial disease, is still a highly prevalent pathology in the worldwide population.
Fluoridation of drinking water has become one of the most widely used methods for caries prevention and has been shown to reduce caries experience in proximal surfaces.  However, its action is less effective on occlusal surfaces, in which the complex anatomy predisposes to enamel demineralization.
The technique of occlusal sealing was introduced in the 1960s when a mixture of cyanoacrylate, polymethylmethacrylate and an inorganic powder was used as a sealing material.  With the advent of Bis-GMA, the use of pit-and-fissure sealants became more popular and widespread, especially because of the possibility of adding filler particles to sealant composition, which increased considerably their wear resistance. 
Sealant placement is considered as an effective treatment modality for prevention of caries onset on occlusal pits and fissures. , The advantages of occlusal sealing include the decrease of caries risk up to nine times compared to non-sealed teeth, as well as the lower cost compared to placement of restorations.  Several materials have shown good results when used as pit-and-fissure sealants, among which are the flowable composite resins. The preventive benefits of such treatment, however, rely on the sealant's ability to thoroughly fill pits, fissures and/or anatomical defects and not to prematurely detach either partially or completely from occlusal surface. 
Therefore, retention is one of the most important prerequisites of pit-and-fissure sealants. The longer the material remains bonded to tooth surface, the more effective will be its protective action. Several factors interfere with sealant retention, including the stress induced by polymerization shrinkage, thermocycling, deflection caused by occlusal forces and water sorption. It has been demonstrated that 5-10% of sealant volume is lost per year. ,,
Within the oral environment, dental materials are subjected to action of different factors, such as salivary flow and composition, which vary throughout the day. , pH variations are also observed in the oral cavity, ranging from neutral to acidic. Enamel demineralization  and alterations of the mechanical properties of restorative materials take place under conditions of acidic pH. ,,,
The purpose of this study was to compare the retention and penetration of a conventional resin-based sealant and a photochromatic flowable composite resin placed on occlusal pits and fissures and submitted to thermal and chemical cycling.
| Materials and Methods|| |
The tested materials with their compositions, specifications and manufacturers are listed in [Table - 1]. The research protocol was submitted for review by the Ethics Research Committee of the Faculty of Dentistry of Ribeirγo Preto (University of Sγo Paulo) and the designed methodology was approved.
Eighty premolars extracted for orthodontic purposes were thoroughly cleaned with water/pumice slurry using Robinson bristle brushes at low speed. Their occlusal surfaces were etched with 37% phosphoric acid for 15 s, rinsed with air/water spray for 15 s and dried with a mild oil-free air stream for 20 s until a uniform whitened surface with chalk-like appearance was obtained. The teeth were assigned to two groups ( n = 40) that were sealed with either a conventional light-cured resin-based pit-and-fissure sealant (Fluroshield; Dentsply Caulk, Milford, DE, USA) or a light-cured, photochromatic flowable composite resin (Tetric Flow Chroma; Ivoclar Vivadent Inc., Amherst, NY, USA). In each group, ten teeth were assessed for sealant penetration and the other 30 teeth were evaluated for sealant retention.
For the teeth sealed with Fluroshield, the sealant was applied to the acid-etched occlusal surface using a disposable applicator tip and was light cured for 20 s using a conventional visible light-curing unit at 450 mW/cm 2 output (Ultralux; Dabi-Atlante, Ribeirγo Preto, SP, Brazil). For the teeth sealed with Tetric Flow Chroma, a layer of Single-Bond (3M ESPE, St. Paul, MN, USA), a one-bottle adhesive system was applied to the acid-etched surface and light cured for 10 s. The flowable resin was then applied to the occlusal pits and fissures and light cured for 20 s. This material contains a photochromatic dye that reversibly changes its colour to green when exposed to halogen light for a period as short as 3 s, becoming visible to naked eye. The dark green colour remains visible for nearly 30 s. The material returns to its original state within 2 to 3 min. After sealing, the teeth were stored in artificial saliva at 37°C for 24 h.
Assessment of sealant penetration
The entire tooth surface (except for the area sealed with the tested materials) was isolated with a layer of epoxy resin (Araldite; Brascola, Sγo Bernardo do Campo, SP, Brazil) and a layer of colorless nail polish (Risquι; Niasi, Taboγo da Serra, SP, Brazil). After drying, the teeth (ten samples of each group) were immersed in 0.2% Rhodamine B fluorescent dye (Carlo Erba AnalytiCals, Milan, Italy) for 24 h and thereafter washed in running water and embedded in polyester resin (SeriFix; Struers A/S, Ballerup, Denmark). The tooth-resin blocks were serially sectioned longitudinally in a mesiodistal direction using the water-cooled diamond saw of a sectioning machine (Minitom; Struers A/S, Copenhagen, Denmark).
The images of the sections were digitized using a desk scanner (Scanner ColorPage-HR7X Slim; Genius-Kye, Taipei, Taiwan) at 400 dpi. To enhance material visualization, the specimens sealed with Tetric Flow Chroma were exposed to the halogen lamp for 3 s to change the shade of the resin into dark green. All images were analyzed by ImageLab software (Dircom Bio Informαtica, Sγo Paulo, SP, Brazil).
To determine the depth of penetration of the materials on the occlusal surface, the distance between the most superficial (most occlusal) and the deepest points on the occlusal central groove was calculated and expressed as the groove's total depth. The measurement corresponding to the length of the central groove filled with the sealing material was divided by the measurement corresponding to its total depth to obtain the percentage of sealing of the occlusal groove. Data was analyzed statistically by Student's t -test at 5% significance level.
Assessment of sealant retention
The occlusal surface of the remaining teeth (30 of each material) were photographed (FinePix 4900; Fujifilm, Japan) at 12× magnification. To enhance the visualization of the material, the specimens sealed with Tetric Flow Chroma were first exposed to the halogen lamp for 3 s to change the shade of the resin to dark green. The occlusal area filled with the sealing materials and designated as the initial area (mm 2 ) was demarcated using ImageLab software (Dircom Bio Informαtica).
Thirty teeth sealed with each of the tested materials were divided into three subgroups: ten teeth were submitted to a thermocycling regimen (1000 cycles; 5/55°C), ten teeth were stored in artificial saliva at 37°C for 30 min (control) and ten teeth were immersed in 4% acetic acid (15 min) and artificial saliva (15 min). A 10-cycle/day protocol was followed for 30 days (total of 300 cycles).
Photographs were taken to assess the final area occupied by the sealing material (mm 2 ). To obtain standardized images, the position of the teeth and the camera were previously fixed. The difference between the final area and the initial area occupied by the sealing material was calculated to obtain the material loss. The material that presented the least loss of substance was considered to have the best retention. The mean material loss that occurred during thermal and chemical cycling regimens was analyzed statistically by two-way anova. Multiple comparisons were done by Tukey's post hoc test at 5% significance level.
| Results|| |
The materials did not show statistically significant differences regarding their penetration in the occlusal central groove ( P > 0.05) [Table - 2].
Although Fluroshield presented greater retention (i.e. less loss of material) than Tetric Flow Chroma [Table - 3], this difference was not statistically significant ( P > 0.05).
Regarding the behavior of each material relative to the treatments performed prior to assessment of retention, it was observed that the specimens immersed in artificial saliva presented the least material loss while those immersed in 4% acetic acid plus artificial saliva showed the greatest material loss. There was statistically significant difference ( P < 0.05) between the group sealed with Fluoroshield and immersed in acid plus artificial saliva compared to the groups submitted to the other two treatments. For Tetric Flow Chroma, no statistically significant difference ( P > 0.05) was observed among the treatments.
| Discussion|| |
Pit-and-fissure sealants are considered as an effective method for prevention of occlusal caries due to their penetration, sealing capability and retention. Several authors have reported that, after 1 year, sealant retention is around 85-95%, which might be considered as a clinical success according to Romcke et al.  and Vrbic. 
Manufacturers have added inorganic filler particles to sealant formulation in order to increase their wear resistance. Nevertheless, this would increase sealant viscosity and compromise its penetration within the etched enamel surface, thus, affecting sealing and retention. , In view of this, the present study investigated the hypothesis that a sealing material with higher percentage of filler but with high flow would provide better penetration and retention outcomes than a conventional pit-and-fissure sealant.
The findings of this study indicated that there was no statistically significant difference ( P > 0.05) between the materials with respect to depth of penetration. Regarding the retention test, the materials had different behaviors with respect to the area of the occlusal central groove occupied by the sealing material before and after thermocycling. Fluroshield (50% load weight) presented higher retention rate than Tetric Flow Chroma, except for the subgroup immersed in acetic acid plus artificial saliva. In this case, Tetric Flow Chroma (64.6% load weight) presented lesser loss of material (11.90 ± 6.8) than the conventional pit-and-fissure sealant (14.16 ± 9.9). However, the difference was not significant statistically ( P > 0.05) for thermocycling and immersion in saliva.
The results of the present study are consistent with those of Autio-Gold  and Duangthip and Lussi  and might be explained by the materials' polymerization shrinkage, which is related to factors such as cavity geometry, quality of adhesion, curing process and materials' viscoelastic properties.  Composites with higher filler content and high modulus of elasticity usually undergo high polymerization shrinkage, which leads to breakdown of the enamel/material micromechanical union that is essential to the retention of the sealing material.  Feigal et al.  suggested the use of adhesive agents underneath pit-and-fissure sealants to improve retention.
Several storage media have been used in polymer degradation assays. According to Soderholm et al .,  artificial saliva causes greater degradation of composites than distilled water. In addition, studies have shown that storage in acidic media compromise the surface integrity of restorative materials. , In this study, Fluroshield pit-and-fissure sealant and Tetric Flow Chroma photochromatic flowable resin were immersed in different storage media to investigate the behavior of these materials under conditions similar to those observed in the oral environment. 
The teeth submitted to pH cycling presented less material retention, especially those sealed with Fluroshield. This might be attributed to the chemical degradation of the essential components of this material, i.e. the resin matrix and the filler particles. , The matrix/filler interface may also deteriorate under low pH conditions. 
Most studies investigating sealant retention are clinical trials and assess either partial or total loss or maintenance of the sealing material based on the evaluation of calibrated examiners who use criteria such as "present", "partially present" or "absent". Among the difficulties faced in studies that use this methodology, is the management of the children enrolled in the clinical trial, appropriate time for sealant placement, the level of patient commitment and the stage of tooth eruption. ,, In vitro methodologies, such as the one used in the present study, have the advantage of quantifying the loss of sealing material (by means of a software-based measurement technique) rather than rating material loss on the basis of pre-established criteria, which would lead to less subjective outcomes.
However, measuring the area occupied by Fluroshield pit-and fissure sealant on the occlusal surface was a difficult task, because in many cases the material was hardly distinguishable from tooth surface. According to Simonsen,  it is practically impossible to distinguish the sealant from enamel some time after placement. On the other hand, the occlusal area occupied by Tetric Flow Chroma was easily identified because of the photochromatic characteristic of this material. The exposure of the sealed surface to a halogen lamp reversibly changed the color of the resin into dark green and made it visible to the naked eye for approximately 2 min. 
The findings of this study suggest that Tetric Flow Chroma flowable photochromatic composite resin can potentially be used as a pit-and-fissure sealant, benefiting from its characteristic of reversible color change to help checking sealant integrity. Nevertheless, several other factors should be considered while evaluating the behavior of materials used to seal occlusal pits and fissures. Further research investigating physical properties as well as wear resistance of this material must be conducted.
| Conclusions|| |
It may be concluded that:
- Both materials presented similar penetration in occlusal pits and fissures.
- With respect to the material used, the conventional pit-and-fissure sealant and the flowable composite resin presented similar results in terms of retention.
- Regarding their behavior relative to the thermal and chemical cycling regimens, the materials did not differ with respect to retention, except for immersion in acetic acid. In this case, Tetric Flow Chroma presented greater retention than Fluoroshield.
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[Table - 1], [Table - 2], [Table - 3]
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