Pits and fissures are the developmental defects naturally present on the tooth surface. These imperfections are caused by the imperfect coalescence of the developing enamel lobes. The geometry of the pits and fissures offer an ideal niche which provide cariogenic bacteria an environment to reside in and produce acid that is essential for the carious attack. Most fissures are shallow and end blindly but some are deep and may communicate up to the dentin. In order to prevent caries propagation into pits and fissures, various approaches have been suggested in the dental literature. Blocking the fissures with zinc oxide-based cements or preparing the cavity walls by intentionally extending into the fissures (known as extension for prevention) or prophylactic odontotomy were some procedures advocated in old literature. In contemporary dental practice, occluding these defects with fissure sealants is the most commonly used method.
Fissure sealants were introduced in dental practice in early 1970s. The sealants physically occlude the pits and fissures and deny the bacteria of the ecologic environment required for caries propagation. One of the basic requirements of sealants material is to be fluid enough to be flown easily into the fissures. Moreover, it has to provide a perfect seal around the walls of the fissures. In other words, the desirable quality of a sealant is to be perfectly adaptable into the fissure anatomy. Resin-modified glass ionomer-based sealant (RMGIC) and flowable resin-based sealant (RC) are the two most widely used varieties of the fissure sealants The RC are generally accepted as the “gold standard.”
Enameloplasty was introduced as one of the pretreatments that could improve the sealant retention. However, the utility of enameloplasty in improving the adaptability of sealant material into fissure is not established. There is evidence in favor of enameloplasty and against it. The key argument against enameloplasty is that it worsens the microleakage. In between these two extremes, there are studies which demonstrate no difference whether enameloplasty is done or not.
We hypothesized that adaptability of sealant material is different in the fissures of teeth treated with enameloplasty versus no enameloplasty. The objective of the study is to explore the effect of enameloplasty on the adaptability of the two sealant materials, namely RMGIC and RC.
MATERIALS AND METHODS
An invitro, experimental study was done from July to November 2017. For sample size calculations, the WHO calculator (sample size determination in health studies by Lwanga) was used. We employed the study by Khanal etal.; who evaluated microleakage and adaptability of glass ionomer and resin sealants with invasive and noninvasive technique. Keeping the mean difference of mean adaptability scores among study groups 1.8 ± 0.83 and 2.6 ± 0.89 at confidence level 95% and power of study 80%, we needed at least 17 specimens per group. We inflated it to 20 per group to compensate for processing errors in preparation of the study slides. Since there were four study groups, we took 80 teeth. The formula for sample size calculation was:
Eighty human extracted premolars and molars were collected from dental clinics from subjects who were scheduled for extraction for advanced periodontal disease. We excluded teeth that were cracked, had fractured crown or were malformed, or with erosion, caries, attrition or previous restorations. Presence of such defects would adversely affect the sealant adaptability and hence act as a confounder to distort the study results.
After cleaning with pumice water and disinfecting with hydrogen peroxide, the extracted teeth were stored in 0.9% NaCl at 4°C. Teeth were randomly assigned into four groups (n = 20) each. Groups were based on type of fissure sealants (RMGIC or RC) and whether enameloplasty was done or not. The distribution is shown in Table 1.
For enameloplasty, a pear-shaped diamond bur, American Dental Association no. 330 (SwissTec, Switzerland) was used in a high speed handpiece while keeping the bur right angle to the tooth surface. The dimensions of the enameloplasty were essentially dictated by the dimensions of the bur (0.80 mm diameter, 8° taper and 1 mm depth). All the preparation were standardized. Each bur was used for making 10 enameloplasty preparation, thus a total of four burs were used in the study.
Following products were employed for sealants: RMGIC: Vitremer; 3M-ESPE, St. Paul, MN, USA. Adhesive (Adper Single Bond; 3M-ESPE, St. Paul, MN, USA). Flowable resin sealants: Filtek Flow; 3M-ESPE, St. Paul, MN, USA). Once the enameloplasty is done, etchant (37% phosphoric acid, Ultradent, USA) was used on the prepared teeth for 15 s. Then teeth were washed (15 s) and dried thoroughly (5–10 s) using air water syringe. Adper single bond adhesive was applied over the fissures; air-thinned and light cured for 20 s followed by Filtek flow which was cured for similar amount of time.
Quartz–tungsten–halogen-based curing light (Polylux, Kavo, Germany) were used to cure all the specimens. The light output intensity was measured by the light intensity meter (Caulk Cure-Rite by L. D. Caulk/Dentsply, USA). It was above 500 mW/cm.
For RMGIC, the liquid and powder were first mixed in a ratio of 2:1, the mixed material was applied over the selected teeth using corpule tip gun (Dentsply, USA), air-thinned and light cured for 40 s. Thermo-cycling of the specimen were carried out to simulate clinical environment to the sample teeth using controlled digital water bath (Human Lab Instrument Co, Korea). The water bath regulated the temperatures of 60°C ± 2°C, and 37°C ± 2°C along the crushed ice container in refrigerator maintained 4°C ± 2°C with dwell time of 30 s.
The teeth crowns were sectioned at the cementoenamel junction using high speed handpiece (NSK, Japan) and were then embedded into the epoxy resin. Crowns were then sectioned buccolingually using diamond cutting saw (EQ MT 4, MTI Corp., USA).
Sample slides were exposed to sunlight for 24 h to control the moisture. The sample slides were then sputter coated with silver in JEOL JFC-1500 AutoFine coater for 120 s before being examined with an analytical scanning electron microscope (SEM) by JEOL JSM 6380 LA, Japan using magnification of ×20X–×450. Samples were scored as following:
- Good: Complete adaptation of material in all fissures
- Fair: Failure of adaptation to only one interface
- Poor: Failure of adaptation to more than one interface.
Four specimens in one group were discarded due to processing error, resulting in 76 slides which were examined under SEM A single trained assessor observed the sample slides under magnification of ×50 and rated the adaptability of sealant using the ordinal score as described above.
SPSS version 23.0 (IBM, Chicago, USA). was used for data analysis. Mann–Whitney U-test was used to compare the adaptability of sealant in the presence or absence of enameloplasty in the two types of sealants. Ordinal regression was applied to see the effect of sealant material and enameloplasty over the outcome (adaptability of sealant in the fissure). Level of significance was kept at 0.05.
The sealant adaptability scores are shown in Table 1. The best adaptability (corresponding with lowest mean ranks) was demonstrated by RC-based sealants (34.81 ± 4.07) placed without any enameloplasty. The least adaptable were RC-based sealants (44.5 ± 4.66) observed with enameloplasty. The details are shown in Table 1.
Figure 1 shows that there was no significant difference in the adaptability scores when two types of sealants (RC vs. RMGIC) were compared. Enameloplasty exerted a negative influence over the adaptability scores of sealants (P = 0.02) as stated in Table 2.
A perfect seal at the tooth-restoration interface that is impervious to saliva and other fluids is the key factor in the success of any dental restoration. Sealing does not only depend upon the type of bond a dental restoration has made with the tooth substance, but also on the chemical nature of the material used. In this respect, the present study compares two varieties of sealant materials for their adaptability into the pits and fissures of the teeth. Moreover, the effect of enameloplasty was also evaluated to determine if it improves the adaptability of sealant or not.
We employed an adhesive (Adper Single Bond) prior to the application of RC-based sealant. This practice is not universally followed. Similarly, an adhesive was also used as a primer prior to the RMGIC-based sealants placement. The idea was to standardize the methodology and offer similar priming of the surfaces.
With regards to the adaptability, both RC and RMGIC exhibited similar scores [Table 1]. Our findings are similar to Goncalves and Kobayashi who compared the adaptability results of RC with GIC-based sealants and concluded that adaptability of both were similar. This suggests that use of a priming adhesive before sealants does improve the adaptability of the sealant material.
It has been known that the adhesive primers improve wettability of sealant materials. An interesting observation was that the use of adhesive primer prevented the propagation of crack under RMGIC material. This was evident by the fact that a number RMGIC material exhibited cracks on surface but the crack disappeared at the adhesive-RMGIC interface, suggesting that adhesive had a protective effect under RMGIC. It was documented in detail in a previous study. This phenomenon can be explained by the fact that adhesive primers are resilient in nature and if used as pretreatment, these can at least camouflage, if not prevent the desiccation of the overlying brittle RMGIC material.
Owing to the brittle nature, glass ionomers are easily desiccated. Incorporation of resin in traditional glass ionomer (i.e., RMGIC) makes it more resilient and flowable. Various approaches have been recommended in literature to improve the adaptability of the sealant material. These include application of alcohol wipes, application of pumice slurry, or fissurotomy (commonly referred to as enameloplasty). However, no material or technique has been considered as gold standard in this regard. Enameloplasty is believed to be enhancing the surface area for sealant adhesion. However, its clinical effectiveness is still questionable. The present study also shows that enameloplasty did not bring any improvement in the adaptability of sealant into the fissure.
There is no consensus over the bur selection for the enameloplasty. Geiger et al. did suggest that for enameloplasty, pear-shaped burs or tapered burs produce better morphology than round burs. For the same reasons, #330 bur was used in the present study. However, our data indicated that enameloplasty did not have any beneficial value with respect to the adaptability of sealant. One of the probable explanations of this observation would be the “C” factor. The C-factor is the ratio between bounded to unbounded surface areas of a polymer-based restoration.
This C-factor appears to be the primary factor responsible for exacerbating the polymerization stresses which could have led to the weakening of the bond between sealant and tooth substance. This speculation may hold true for resin-based sealants which set with polymerization reaction but what could be the explanation of poor performance of enameloplasty subjected RMGIC-based sealants (whose primary setting reaction is an acid-base reaction)? The answer is not clear.
Xalabarde etal. have done detailed investigation on fissures after enameloplasty, and studied the effect of thermocycling on the adaptation of enamel surfaces of filled and unfilled sealants. They concluded that sealant adaptation to enamel was superior when the enameloplasty was used. However, there was no difference in penetration and adaptation between the filled and the unfilled sealants or between the thermocycled or un-thermocycled sealants. Interestingly, in a later investigation by Xalabarde etal., where they evaluated microleakage of a filled and an unfilled sealants after occlusal enameloplasty, they concluded that there is no statistical significant difference in the microleakage between the thermocycled and nonthermocycled groups, between the enameloplasty or with no enameloplasty or between the filled and unfilled sealants. Thus, it appears that the overall adaptability of the sealant material has more to do with the material flowability, bonding with tooth substance, handling characteristics, and placement technique than the enameloplasty.
The strengths of the study include adequate sample size, using two common varieties of sealants, and addressing a common clinical question which entails use of an additional procedure (enameloplasty) which was believed to yield superior outcome but it turned out that the opposite is true. Another strength in our methodology was that the thermocycling was carried out to simulate intraoral environment. The limitations of the present study are an in vitro experiment and only one type of bur (pear-shaped) for enameloplasty was used.
No significant difference was observed between resin and RMGIC-based sealants for their in situ adaptability in the tooth fissures. Enameloplasty exerted a negative impact on the adaptability of the sealant irrespective of the chemistry of sealant material employed.
The study was ethically approved by the IRB committee of the Dow University of Health Sciences, Reference no.: IRB-252/DUHS - 11.
Financial support and sponsorship
The study was funded by the research facilitating committee of the Dow University of Health Sciences. Grant #DUHS/Dr/2011/738.
Conflicts of interest
There are no conflicts of interest.
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