Year : 2008 | Volume
: 26 | Issue : 3 | Page : 114--120
Retention of a resin-based sealant and a glass ionomer used as a fissure sealant: A comparative clinical study
P Subramaniam, S Konde, DK Mandanna
Department of Pedodontics and Preventive Dentistry, The Oxford Dental College, Hospital and Research Centre, Bommanahalli, Hosur Road, Bangalore-560068, Karnataka, India
Department of Pedodontics and Preventive Dentistry, The Oxford Dental College, Hospital and Research Centre, Bommana Halli, Hosur Road, Bangalore-560068, Karnataka
Sealing occlusal pits and fissures with resin-based sealants is a proven method of preventing occlusal caries. Retention of the sealant is very essential for its efficiency. This study evaluated the retention of glass ionomer used as a fissure sealant when compared to a self-cure resin-based sealant.
One hundred and seven children between the ages of 6-9 years, with all four newly erupted permanent first molars were selected. Two permanent first molars on one side of the mouth were sealed with Delton, a resin-based sealant, and the contralateral two permanent first molars were sealed with Fuji VII glass ionomer cement. Evaluation of sealant retention was performed at regular intervals over 12 months, using Simonsen«SQ»s criteria. At the end of the study period, the retention of the resin sealant was seen to be superior to that of the glass ionomer sealant.
|How to cite this article:|
Subramaniam P, Konde S, Mandanna D K. Retention of a resin-based sealant and a glass ionomer used as a fissure sealant: A comparative clinical study.J Indian Soc Pedod Prev Dent 2008;26:114-120
|How to cite this URL:|
Subramaniam P, Konde S, Mandanna D K. Retention of a resin-based sealant and a glass ionomer used as a fissure sealant: A comparative clinical study. J Indian Soc Pedod Prev Dent [serial online] 2008 [cited 2020 Jun 2 ];26:114-120
Available from: http://www.jisppd.com/text.asp?2008/26/3/114/43192
Methods of caries prevention should pay special attention to surfaces with pits and fissures because they have always been the earliest and most common sites to be affected by caries. Occlusal caries is most prevalent in children as a result of the morphology of pit and fissure surfaces: they are stagnation areas, where plaque formed is anatomically protected from even a single toothbrush filament by the dimensions of the fissure.  Probably, the most caries-susceptible period of a first permanent molar is the long eruption phase. At this period, the enamel immatured, the child and parents often do not know that a new tooth is erupting, and it is usually difficult for the child to clean the erupting tooth surfaces.  Preventive measures such as control of bacterial plaque and topical applications of fluoride solutions have little effect on such surfaces.  More effective measures are therefore necessary, such as the application of occlusal sealants. 
Since their introduction in Dentistry many commercial preparations are available. These sealants differ according to the base material used, the method of polymerization, and whether or not they contain fluoride. Although the majority of sealants available in the market have the same basic chemical composition hence, it is important to know the effectiveness and retention capacity of each sealants.  The ability of a sealant to release fluoride, in addition to occluding pits and fissures, would be a distinct advantage over the conventional resin-based sealants. 
Ionomeric cements have been suggested to be ideal material for sealing pits and fissures due to their ability to release fluoride and adhere to the enamel.  The new glass ionomer Fuji VII (GC Corporation, Tokyo, Japan) which has a high fluoride release has been introduced for caries stabilization and protection of susceptible tooth surfaces. This study was taken up to compare the retention of a self-cure resin-based pit and fissure sealants with a glass ionomer cement.
Materials and Methods
Children aged between 6-9 years were examined in their respective schools after obtaining consent from the concerned school authorities. Dental examination was performed in natural daylight using sterile and disposable mouth mirrors with good reflecting surfaces and dental explorers.
Healthy cooperative children with all four newly erupted caries-free and untreated permanent first molars were selected for inclusion in the study. The inclusion criteria specified that the occlusal surfaces had to be fully visible and free of mucosal tissue. The children with hypoplastic permanent first molars, developmental anomalies were excluded from the study.
Out of 120 children who fulfilled the inclusion criteria, the parents of 107 children gave their written consent for participation in the study. Ethical clearance to conduct the study was obtained from the institutional review board.
The children were brought to the Department of Pedodontics and Preventive Dentistry for pit and fissure sealant application. A single operator carried out oral prophylases procedures for each child, followed by prophylaxis using a slurry of pumice and a rotating brush to ensure the removal of debris from the fissures.  The occlusal surfaces of the first permanent molars were thoroughly flushed with water to remove the traces of isolation of permanent first molars was achieved using cotton rolls and a saliva ejector held by an assistant. 
The self-cure opaque resin-based sealant, Delton (Dentsply International, York, PA) was applied following the manufacturer's instructions on 16 and 46. The occlusal surface was dried and the liquid etchant provided (35% phosphoric acid) was applied with a disposable nylon brush into the pits and fissures and extended up the cuspal inclines.  Each tooth was etched for 60 s and then rinsed thoroughly for 30 s using an oil-free air-water syringe. The cotton rolls were substituted, taking care not to contaminate the etched surfaces, which were then thoroughly blow-dried. Etching was confirmed by a dull frosty-white appearance of the enamel. If salivary contamination occurred, the surface was again cleaned, dried, and re-etched. 
The two sealant components were mixed together thoroughly for 10 second and disposable applicator tubes inserted into applicator handles were used to draw up a measured amount of sealant. This amount of sealant, which was suitable for an occlusal surface, was gradually dispensed along the fissures. A probe was used to remove air bubbles and ensure sealant flow into all pits and fissures. An explorer was used to check for complete application of pits and fissures.
The pink-colored glass ionomer was applied as a sealant on 26 and 36. The occlusal surfaces were gently cleaned with GC Dentin Conditioner for 20 s, rinsed for 20 s, and then dried by blotting with a cotton pellet. The surfaces were not desiccated and appeared moist and glistening. The cement was mixed as per the manufacturer's instructions and applied to the occlusal surface using a plastic filling instrument. A disposable nylon brush was used to spread it properus on to the pits and fissures. The sealant was protected with a coat of petroleum jelly.
The patients were instructed not to eat or drink anything for 30 min, they were recalled for assessment of sealant retention at intervals of 3, 6, 9, and 12 months.
Intra-examiner variability was minimized by reexamining on 10% of patients. Retention of the sealants at the specified time intervals was evaluated using Simonsen's criteria.  The data obtained was tabulated and subjected to statistical analysis using the Chi-square test and the Fisher exact test.
Comparison of retention of the two sealants [Table 1] and [Figure 1]
At the third month of evaluation, 58% of resin sealant was completely retained, as compared to only 27.2% of glass ionomer sealant. On 77 teeth (37.4%), resin sealant was partially retained and on 139 teeth (67.5%) glass ionomer sealant was partially retained. The difference in the degree of retention between the two sealants was highly significant. Nine of the resin-sealed teeth (4.4%) and 11 of the glass ionomer-sealed teeth (5.3%) showed missing sealant.
Both sealants showed highest loss at the sixth month of evaluation. Thirty-eight percent of resin sealant (79 teeth) was completely retained as compared to only 13.1% of glass ionomer sealant (27 teeth). This difference was highly significant. Partial sealant retention was seen in 104 teeth (50.5%) sealed with resin sealant as compared to 101 teeth (49.0%) sealed with glass ionomer sealant. Twenty-three teeth (11.2%) showed missing resin sealant and 78 teeth (37.9%) showed missing glass ionomer sealant, a difference was statistically significant.
A significant difference was also seen in the retention of the two sealants at the ninth month of evaluation. Twenty percent of resin sealant (43 teeth) was completely retained as compared to only 2.9% of glass ionomer sealant (6 teeth). Forty-nine percent (102 teeth) of resin sealant was partially retained, while glass ionomer sealant was partially retained on 76 teeth (36.9%),. Twenty-nine percent (61 teeth) showed missing resin sealant and 60.2% (124 teeth) showed missing glass ionomer sealant.
Comparison of the two sealants at the end of 1 year showed complete retention of 14% of resin sealant as compared to only 0.9% of glass ionomer sealant (2 teeth). This difference was highly significant. Partial sealant retention was seen in 39.3% (81 teeth) that had resin sealant applied, as compared to only 27.7% (57 teeth) that had glass ionomer sealant treatment. This difference was also significant. Forty-six percent (95 teeth) showed missing resin sealant and a significantly higher number of teeth, 147 (71.4%), exibited missing glass ionomer sealant.
Comparison of sealant retention on upper and lower first permanent molars [Table 2] and [Figure 2]
At the third month, 57.28% (59 teeth) of resin sealant was completely retained on upper teeth as compared to 59.22% (61 teeth) of sealant on lower teeth. Partial retention of resin sealant was seen on 39 upper teeth (37.86%) and on 38 lower teeth (36.89%). The resin sealant was missing on 4% of upper teeth (5 teeth) and 3.88% of lower teeth (4 teeth). At the sixth month, 31.07% of sealant (32 teeth) was completely retained on upper teeth as compared to 45.63% of sealant (47 teeth) on lower teeth. This difference was significant. Sealant was partially retained on 60 upper teeth (58.25%) and on 44 lower teeth (42.72%). This difference was also significant. The sealant was missing on 11 upper teeth (10%) and 12 lower teeth (11.65%). At the ninth month, 14 upper teeth (13.59%) showed complete sealant retention as compared to 29 lower teeth (28.15%). This difference was significant. The sealant was partially retained on 56 upper teeth (54.36%) and on 46 lower teeth (44.66%). Thirty-two percent (33 teeth) of upper teeth and 27.18% (28 teeth) of lower teeth showed missing sealant. At the twelfth month, 7.76% of resin sealant (8 teeth) was completely retained on upper teeth as compared to 21.36% of sealant (22 teeth) on lower teeth. This difference was significant. Sealant was partially retained on 44 upper teeth (42.72%) and on 37 lower teeth (35.92%). The resin sealant was missing from 49% of upper teeth (51 teeth) and from 42.71% of lower teeth (44 teeth).
Glass ionomer sealant
At the third month, 25.24% of sealant (26 teeth) was completely retained on upper teeth as compared to 29.13% (30 teeth) on lower teeth. It was partially retained on 70 upper teeth (67.96%) and on 69 (66.99%) lower teeth. Sealant was missing from seven upper teeth (6%) and four lower teeth (3.88%). At the sixth month, 8.74% of glass ionomer sealant (nine teeth) was completely retained on upper teeth as compared to 17.47% of sealant (18 teeth) on lower teeth. This difference was significant. The sealant was partially retained on 44 upper teeth (42.72%) and on 57 lower teeth (55.33%). Forty-eight percent (50 teeth) of upper teeth and 27.18% of lower teeth (28 teeyh) showed missing sealant. This difference was significant. At the ninth month, none of the glass ionomer sealant was completely retained on upper teeth as compared to 5.83% of sealant (six teeth) on lower teeth. This difference was significant. Thirty percent of partial retention was seen in 31 upper teeth which was significantly different from 44% on 45 lower teeth. The glass ionomer sealant was missing from 72 upper teeth (70%) and 52 lower teeth (50%); this was a significant difference. At the twelfth month, none of the glass ionomer sealant was completely retained on upper teeth as compared to only 1.94% of sealant (two teeth) on lower teeth. The glass ionomer sealant was partially retained on 25 upper teeth (24.27%) and on 32 lower teeth (31.07%). Seventy-six percent (78 teeth) of upper teeth and 67% of lower teeth showed a missing sealant.
Dental sealants have been proved to be highly effective in the prevention of pit and fissure caries. The caries-preventive property of sealants is based on the establishment of a seal which prevents nutrients from reaching the microflora in the fissure. The preventive effects of the sealant are maintained only as long as it remains completely intact and bonded in place.  Adequate retention of sealant requires the sealed tooth to have a maximum surface area with deep, irregular pits and fissures, and to be clean and dry at the time of the procedure. 
Most of the sealants available in the market are resin based. However, placement of a resin is very technique-sensitive and is influenced by several factors, such as patient cooperation, operator variability, and contamination of the operating field.  A major drawback of sealing fissures with resins is that the clinical procedure is extremely sensitive to moisture, which makes it difficult to etch partially erupted molars. 
Isolation by rubber dam or cotton rolls are equally effective in retention rates. , In this study, cotton rolls were used, a technique that has been referred to as partial isolation.  It has been stated that absolute isolation is not necessary for the application of sealants as long as extreme care is taken to avoid salivary contamination of the etched surface. 
Etching roughens the tooth surface and produces a honeycomb-like structure so that tags of sealant can penetrate deeply into the enamel and form an effective mechanical bond, thus retaining the sealant. The disadvantages of resin sealants lie in their hydrophobic nature. Resins do not form hydrolytically stable bonds, so their retention on tooth structure depends on the durability of the mechanical bond. A 15-20 s etch, for either primary or permanent dentition, should be adequate for sealant retention. 
Many researchers confirm that the Glassionomers are seperately be preferable for sealing newly erupted teeth.  Glass ionomer sealants offer similar caries-preventive effects as resin-based sealants, with easier manipulation and without the use of acid etching. The glass ionomer may be valuable as a sealant in cases of difficult operating conditions i.e. difficulty with moisture control in partially erupted teeth or in children with management problems or in very young children.  The ease of application, reduction in operating time, and the adherence of these materials to moist teeth favors their placement.  They are biocompatible and have a coefficient of thermal expansion slightly lower than that of tooth structure.  These advantages of glass ionomer cement make it a suitable sealant for community care programs.
Most of the studies on sealants have used the half-mouth design, in which the teeth on one side of the mouth were treated, while the contralateral teeth remained unsealed.  Unsealed homologous paired teeth cannot, to be used as controls. An alternative is to compare the retention of at least two sealants in the same mouth, eliminating the need for untreated control teeth.  Such studies should use a split-mouth design that does not withhold treatment benefit from the patient.
The addition of color to a sealant greatly improves perception at application and on recall examination; it also simplifies record keeping by use of clinical photographs, as compared with patients who have clear resin sealants placed. These tinted sealants are easily visible and chairside time is saved at follow-up.  Also, parents are reassured when they can see the sealants on their child's teeth.  As the sealant is clearly visible to the child, it is of benefit to encourage the child to look periodically for any sealant loss. This constant reminder of the presence of a preventive agent will help in the motivational aspects of the preventive program.  White was found to be the most esthetically acceptable color for patients.  However, the chief criticism of opaque sealants is the inability to visually detect progression of caries underneath them.
Reported evidence of sealants needing replacement or repair in contemporary studies averages between 5 and 10% per year.  Clinical evidence suggests that sealant loss (retention failure) occurs in two phases: there is an initial loss due to faulty technique (such as moisture contamination), followed by a second loss associated with material wear under the forces of occlusion. 
In our study, at the end of 1 year, the resin sealant showed 14.6% complete retention, 39.3% partial retention, and 46% missing sealant, i.e., the resin sealant was missing from nearly half the treated teeth. The highest rate of sealant loss was seen at the sixth month, with only 38% of sealant completely retained and 51% partially retained. This was in accordance with Whitehurst and Soni, who found that the greatest sealant loss occurred during the first 6 months. They also reported only 18% of first and second molars were completely sealed after 1 year.  Also, Stephen et al. reported that only 12 out of nearly 400 teeth remained completely sealed after 1 year in a study performed under field conditions. 
A high retention rate of 76-85% after 10 months was observed by Shashikiran et al. , which could be attributed to their use of rubber dam isolation and sealant reapplication.  Lygidakis et al. observed a retention rate of 89% after 4 years following mechanical preparation of pits and fissures. 
Considering possible reasons for failure of resin sealant, Anson et al. listed poor placement technique (inadequate moisture control, not sealing all pits/fissures, inadequate etching, inadequate rinsing and drying, and insufficient curing time); material wear; non-sealant failure (extraction of tooth, proximal caries, and exfoliation); and finally, failure due to a combination of these factors.  Other variables which influence sealant retention include the position of the tooth in the mouth, the skill of the operator, and the age of the patient.  The presence of prismless enamel on newly erupted teeth confers a morphological difference in the etching pattern and a smaller surface area for bonding, which can influence the clinical performance of sealants. 
Taylor and Gwinnett reported that pumice particles lodged in the fissures are not removed after rinsing.  However; the effect of pumice prophylaxis on retention of sealants was not of any significant effect.  Also, a disadvantage of autopolymerizing resins is that they should be in place before setting of the resin begins, since this phase is marked by a significant increase in viscosity which inhibits resin penetration and thereby retention.
In present study, the sixth month of evaluation revealed the highest rate of loss of glass ionomer sealant, with only 13.1% completely retained, 49% partially retained, and 37.9% missing. The twelfth month evaluation showed very low retention, with only 0.9% showing complete retention, 27.7% showing partial retention, and 71.4% showing missing sealant, i.e., the glass ionomer sealant was missing from more than half the treated teeth.
According to Boksman and colleagues (1987), the routine clinical use of a glass ionomer sealant was unreliable because of poor retention. They observed a total loss of 94% after 6 months.  McKenna and Grundy, however, reported a 93% retention rate after 6 months and 82.5% after 1 year. 
One main reason for the loss of the glass ionomer sealants could be inadequate adhesion of the cement to the enamel surface.  In addition, the cement may have been exposed to saliva before it had completely set, which would predispose to surface degradation and early loss of sealant.  The topography of the occlusal surfaces may be an obstacle for good adhesion. Surface irregularities may result in entrapment of air voids, hence reducing the strength of the adhesive joint. 
Other possible explanations for the poor retention of glass ionomer sealant include inability to obtain adequate cooperation for isolation in the younger children, difficulty in application on partially erupted teeth, excessive salivation, and mucosal tissue covering the occlusal surface, which would make sealant application more cumbersome. The low wear resistance of glass ionomer materials to occlusal forces may contribute for cement disintegration, by thinning the sealant and eventually erosion of material.
In vitro studies on the influence of various pretreatment procedures on adhesion between glass ionomer and enamel indicate that adhesion can be considerably improved by conditioning the enamel surface before application of cement.  Some manufacturers recommend that the enamel surface be cleaned with a diluted polyacrylic acid solution prior to sealant application. This procedure, however, might compromise the wettability and penetration of the sealant into enamel producing a low retention rate.  Also, as the setting reaction of glass ionomer sealant is fast, the ability of the sealant to penetrate into fissures, and hence its adhesive strength, may decrease if the instructions are not followed properly.  Increase in the proportion of powder results in a more viscous cement which also sets faster, thus reducing the ability of the cement to flow readily and to adhere to the surface. 
The considerably lower retention rate obtained with the glass ionomer compared with the resin-based sealant is in agreement with previous studies. Songpaisan and coworkers in a field trial, found retention of resin sealant to be 92% after 6 months, while retention of glass ionomer sealant was a low 2-8%.  Poulsen et al. found that 3 years after application, the glass ionomer sealant (Fuji III) was lost in almost 90% of teeth compared to only 10% loss of the resin sealant Delton. 
Maintenance of sealants is vital for long-term success. However, there is evidence that teeth sealed very early after eruption require more frequent reapplication of the fissure sealant than teeth sealed later.  When resins are attached to enamel by acid-etching techniques they provide stronger mechanical bonds than the molecular bonds of glass ionomer cements. For this reason, glass ionomers, when used as fissure sealants, are not successful when placed in fissures that have no orifice. Although the cement may be applied to such a fissure, it will soon be lost through erosion / abrasion. By contrast, when glass ionomer was used as sealant in patent fissures (exceeding 100 µm in width). 
The caries-preventive effect of glass ionomer sealant depends on both retention of sealant and release of fluoride from the sealant. It has been suggested that fluoride released by the glass ionomer sealant material and taken up by the adjacent enamel can prevent the development of caries even after visible loss of sealant material. Even where glass ionomer sealants appear clinically to have been totally lost, there remain small particles of material attached to the enamel of the occlusal fissures.  Scanning electron microscopy of fissures has shown the cement to remain in the deeper recesses, acting as a plug. The bioavailability of the leachable fluoride ion, which diffuses into surrounding enamel during the retention period, would increase the resistance of enamel to demineralization.  The establishment of a fluoride reservoir might be expected to contribute to caries prevention and to make the effectiveness of glass ionomer materials as sealants less dependent on the long-term retention of the material. Williams et al. suggested that glass ionomers used as sealants should be regarded as slow-release fluoride reservoirs and be called 'fluoride depot cements.'
This study revealed higher sealant retention rates for the mandibular teeth. This is in agreement with other studies that have compared resin-based sealants and glass ionomer sealants. , This could be because of direct visualization during application, gravity-aided flow of the sealant, and the presence of well-defined pits and fissures contribute to superior retention.  Also, the effect of occlusal stress on the sealant of the maxillary molar appeared at an earlier stage of eruption compared with that of the mandibular molar. The decrease in retention rates found in 8-9-year-old children may be related to the occlusal stress that occurs during eruption. In the earlier stages of mandibular eruption, the maxillary teeth contact only mandibular cusps not reaching the sealant. 
Recently, concerns have been raised about the possibility that estrogenic chemicals, especially bisphenol-A (BPA) and bisphenol-A dimethacrylate (BPADMA) resin-based sealants. Thus, glass ionomer sealants can be considered as a viable alternative. 
Dental sealants are a proven tool in caries prevention.  Whether the prevention of caries is due to obturation of the fissures or to the local presence of fluoride, or due to both, it would appear that long-term retention of glass ionomer fissure sealants is not a prerequisite for caries prevention and such treatment should perhaps be regarded more as a form of very prolonged fluoride application rather than as a sealing of fissures.
In children with high risk of caries and partially erupted molars, the use of a glass ionomer as a fissure sealant should be encouraged rather than the traditional approach of waiting until the tooth fully erupts. The use of glass ionomers as interim sealants is highly beneficial in newly erupted teeth when the risk of caries is highest.
The following conclusions were drawn from the study:
The retention of the resin sealant was superior to that of the glass ionomer cement at the end of 1 year.The retention of sealants on mandibular teeth was superior to that on maxillary teeth.
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