Evaluation of Penetration and Adaptation of a Silver Nano-Crystal Incorporated Pit and Fissure Sealant: A Stereomicroscopic Analysis

ABSTRACT

Objective:  To compare the penetration and adaptation of a silver nanocrystal-incorporated pit and fissure sealant with a conventional resin-based sealant using stereomicroscopy and scanning electron microscopy (SEM) analysis.

Material and Methods:  In this in vitro comparative study, 28 non-carious premolars and molars were divided into two groups (n=14). One group received a conventional sealant and the other a silver nanocrystal-incorporated sealant. All the teeth were sectioned buccolingually, following which one half of each sectioned tooth was used to assess sealant penetration and adaptation using stereomicroscopy, and among the remaining other halves, seven randomly selected samples from each group were evaluated qualitatively under SEM.

Results:  A statistically significant difference (p=0.002) was observed in the number of resin tags at the fissure base, with the conventional sealant showing superior penetration. SEM images also revealed more resin tag formation in the conventional group.

Conclusion:  While both sealants showed comparable overall performance, the conventional sealant demonstrated better penetration into fissure bases. However, further research is needed to optimize the physical properties of silver nanocrystal-based sealants.

Keywords:
Pit and Fissure Sealants; Preventive Dentistry; Dental Materials; Tooth Remineralization.

Introduction

The occlusal surface of permanent premolars and molars is particularly susceptible to carious lesions, with a significant percentage originating in their pits and fissures [¹,²]. The application of a sealant to correct these anatomical enamel imperfections is a key preventive strategy. Studies have shown that sealants applied to the first permanent molar prevent dental caries and reduce the need for subsequent restorations [³]. To facilitate adhesion, sealants utilize an acid to penetrate the minute pores of pre-conditioned enamel, forming resin tags that adapt the resin material to the tooth surface [⁴,⁵]. The success or failure of a sealant is determined by its ability to penetrate, adapt, and form a strong bond [⁶].

Silver nanoparticles have demonstrated potent antimicrobial efficacy against a diverse spectrum of pathogens, notably Streptococcus mutans, exhibiting a minimum inhibitory concentration (MIC) of 4.86 g/ml and a minimum bacteriostatic concentration (MBC) of 6.25 g/ml, thus confirming their bactericidal and bacteriostatic capabilities [⁷,⁸]. Beyond their antimicrobial properties, silver nanoparticles also possess the capacity to promote remineralization. This process is further enhanced by the addition of fluoride, which also encourages remineralization in the presence of cariogenic microorganisms [⁹]. In addition to this, silver nanoparticles within a 50 to 100 nm in size range have shown favourable biocompatibility with periodontal tissues and exhibit low levels of toxicity [¹⁰]. However, there is limited literature evaluating the impact of silver nanocrystal incorporation on the mechanical properties of sealants, particularly their ability to penetrate and adapt in deep fissures. This study aims to address this critical gap in existing literature by comparing the penetration and adaptation of silver nanocrystal-incorporated resin sealant to conventional resin sealant, given its potential advantages in antibacterial and remineralizing properties.

Thus, the objective of the study was to assess the adaptability and penetration of a sealant containing silver nanocrystals using stereomicroscopy and scanning electron microscopy (SEM). The null hypothesis for the study posits that there will be no significant difference in the penetration and adaptability between a silver nanocrystal-integrated sealant and a conventional sealant.

Material and Methods

Study Design and Ethical Clearance

This in vitro experimental intergroup comparative study was conducted after obtaining the Institutional Ethics Committee clearance (reference no.: 22090).

Sample

The study used permanent teeth removed for orthodontic and therapeutic purposes. Premolars and molars with extensive retentive pits and fissures were included to more accurately simulate morphological characteristics typically associated with high cariogenic susceptibility. Teeth exhibiting any signs of attrition, pre-existing restorations, fracture, or cracks were excluded to ensure uniformity of the sample.

Based on the values from the study by Garg et al. [¹¹] and using the formula to determine the sample size for two groups, a total sample size of 28 was obtained, with two ratios of 62.5% and 25% at an alpha error of 5% and a power of 80%.

$$N=\frac{2{(Z_{1-\frac{\alpha }{2}}+Z_{1-\beta })}^2(\sigma 1-\sigma 2{)}^2}{d^2}$$

Procedure

The twenty-eight intact premolars and molars, meticulously selected according to the set inclusion and exclusion criteria, underwent prophylaxis, including cleaning and polishing with a pumice-water slurry using a rubber cup, followed by air-drying. Subsequently, the entire fissure area was etched for 30 seconds by the application of 37% phosphoric acid gel (Scotch Bond Etchant, 3M ESPE, St. Paul, MN, USA). After this, the teeth were rinsed with water and dried with compressed air. This was followed by a random division of the teeth into two groups of 14 each. Following the manufacturer's recommendations, a conventional sealant (Clinpro sealant, 3M ESPE, St. Paul, MN, USA) was subsequently applied to the group I samples, and a silver nanocrystal-incorporated sealant (Kids-e-dental LLP, Mumbai, India) was applied to the group II samples. The sealant was then polymerized using visible-light curing (3M Elipar, 3M ESPE, St. Paul, MN, USA) after a 20-second dwell time to allow optimal penetration into the fissure. All 28 teeth, comprising 14 from each group, were sectioned buccolingually. For each sectioned tooth, one half was used for stereomicroscopic analysis. Of the remaining 14 halves, 7 samples from each group were prepared for SEM visualization.

Stereomicroscopic Evaluation

To dissolve the tooth samples and retrieve the sealant, the sectioned samples (n=28, 14 from each group) were submerged in a 30% nitric acid (HNO₃) solution for 6 hours. The fissure was represented by the base of the sealant. After being placed on a slide, the replicas were rinsed with deionized water and analyzed using a stereomicroscope. Stereomicroscopy was performed at 40x magnification. The parameters recorded during the analysis of sealant penetration and adaptation, based on visual identification of discontinuities or extensions within the replica, included the following observations: a) Bubbles at the bottom of the fissure; b) Debris within the fissure; c) Tags located at the bottom of the fissure, and d) Tags found at the cuspal slopes and entrances of the fissures.

SEM Visualization

For scanning electron microscopy, 14 sectioned samples (7 from each group) were randomly selected and prepared. These specimens were mounted onto aluminum stubs using a conductive colloidal silver adhesive. Subsequently, the mounted tooth specimens were desiccated for 2 hours, after which they were coated with a conductive gold-palladium film using a sputter coater. Finally, these prepared specimens were visualized via SEM (Carl Zeiss AG, Oberkochen, Germany). The qualitative evaluation of the SEM imaging was done at 1000x magnification.

Statistical Analysis

The statistical assessment was performed using SPSS version 20.0 (IBM Corp., Chicago, IL, USA). The chi-square test was employed to determine the presence or absence of the parameters assessed by stereomicroscopic examination of the sample. A p-value <0.05 indicated statistical significance.

Results

When different variables that reflect the adaptation and penetration properties as analyzed through stereomicroscopy were compared between the groups, a statistically significant difference was identified when tags present at the bottom of the fissure were compared (p=0.002). All the samples belonging to the silver nanocrystal-incorporated pit and fissure sealant group showed an absence of resin tags at the bottom of the fissure, whereas 50% of the samples in the conventional sealant group displayed it (Figure 1). However, no significant differences were noted between the two groups for the other tested parameters (Table 1).

Table 1
Analysis of different parameters between the conventional and the silver nanocrystal incorporated sealants.

Parameters		Conventional Sealant	Silver Nanocrystal-Incorporated Sealant	p-value
		N (%)	N (%)
Bubbles in the bottom of the fissure
Absent	7	5 (35.7)	2 (14.3)	0.19
Present	21	9 (64.3)	12 (85.7)
Debris in the fissure
Absent	11	6 (42.9)	5 (35.7)	0.699
Present	17	8 (57.1)	9 (64.3)
Tags in the bottom of the fissure
Absent	21	7 (50.0)	14 (100.0)	0.002*
Present	7	7 (50.0)	0 (0.0)
Tags at cuspal slopes and fissure entrance
Absent	27	13 (92.9)	14 (100.0)	0.309
Present	1	1 (7.1)	0 (0.0)

• ^*
  Statistically significant.

Figure 1
Stereomicroscopy images of the pit and fissure sealant base: A) Conventional sealant; B) Silver nanocrystal-incorporated sealant.

Upon SEM (1000x magnification) visualization of the tooth-sealant interface, the conventional sealant was found to be irregular, with more resin tags in all tested samples (Figure 2). A qualitative summary of SEM observations is presented in Table 2.

Table 2
Qualitative summary of SEM observations between groups.

Group	Interface Regularity	Resin Tags Visible	Observations
Conventional Sealant	Irregular	Clearly present	Distinct resin tags at fissure base
Silver Nanocrystal Sealant	Relatively smoother	Less or not visible	Minimal tagging; limited adaptation visible

Figure 2
SEM images at 1000x magnification demonstrating the sealant-tooth interface: A) Conventional sealant with more resin tags; B) Silver nanocrystal sealant with smoother interface.

Discussion

Although dental caries is among the most prevalent pediatric diseases, it is largely preventable. Pit and fissure sealants have long been recognized as the most effective method for preventing occlusal caries [¹²,¹³]. Ongoing research consistently seeks to identify the optimal sealant formulation that can provide the highest level of protection against caries. The recent incorporation of silver nanocrystals into resin sealants represents a significant advancement in this pursuit. This innovation enhances the remineralization and antibacterial properties of the sealant compared to conventional sealants. Studies have demonstrated that sealants with silver nanocrystals significantly decreased demineralization and promoted remineralization [⁴]. However, an ideal sealant must also exhibit excellent adaptation to the tooth surface and possess good retention [¹¹]. Consequently, the present study utilized stereomicroscopic analysis to assess the adaptability and penetration characteristics of the silver nanocrystal-incorporated sealant.

According to the study's findings, there was a notable difference in the formation of resin tags, with the conventional sealant group showing a substantially greater number of tags at the base of the fissure than the silver nanocrystal sealant group. These results suggest that while silver nanocrystal-incorporated sealants offer antibacterial and remineralizing properties, they appear to exhibit mechanical limitations in terms of penetration and adaptation. The significantly lower number of resin tags at the fissure base could affect long-term retention and overall sealing capacity. Therefore, despite their theoretical promise, the current formulation of silver nanocrystal sealants may require further optimization to achieve physical performance comparable to that of conventional sealants.

Additionally, the amount of debris at the bottom of the fissure was greater for the silver nanocrystal-incorporated sealant, although the difference was not statistically significant. The observed discrepancies may be attributed to the low viscosity of the conventional pit and fissure sealant, which permits deeper fissure penetration [¹⁴]. These findings align with a study by Salas-López et al. [⁴], which reported greater microleakage in the silver nanocrystal-incorporated sealant group than in the conventional sealant group, with a non-significant p-value. Collectively, the results of the present study, bolstered by the findings of Salas- López et al. [⁴], indicate a deficit in close adaptation when silver nanocrystals are incorporated into the sealant.

The high depth of focus and magnification of the SEM enable clear visualization of the pit and fissure sealant penetration and adaptation to the enamel walls [¹⁵]. In the present study, SEM imaging of selected samples from both groups revealed a more irregular tooth-sealant interface in the conventional resin sealant, attributed to the greater presence of resin tags. This finding complements the observation made under stereomicroscopic evaluation, which also indicated a higher number of resin tags at the fissure base for conventional resin sealants.

The sealant application in the current study adhered to the traditional method of cleaning, etching, and sealing the tooth according to the manufacturer’s instructions. The application of bonding agent after etching remains a disputable issue, with proponents citing concerns about increased time and cost [¹⁴]. Long-term clinical investigations by Mascarenhas et al. [¹⁶] and Boksman et al. [¹⁷] found that using a bonding agent before sealing did not improve sealant retention. While other studies [¹⁸-²¹] reported a significant reduction in microleakage scores with pre-sealing bonding agent application, this procedure is less feasible in younger, uncooperative children due to extended treatment time and potential breach of isolation [¹⁴]. Consequently, a bonding agent was not employed in this study.

To the best of our knowledge, this study was the first to assess the penetration and adaptability characteristics of such sealants. Although the present investigation revealed limited adaptation and penetration of silver nanocrystal sealants, a comprehensive review of existing literature did not yield additional evidence to support these findings. A limitation of the current study is the inclusion of both molars and premolars, which may introduce heterogeneity and potentially influence the results. Furthermore, as an in vitro study, it inherently lacks the complexities and dynamic environmental factors present in a clinical scenario. Thus, given the limited literature on silver nanocrystal-incorporated sealants, further studies are recommended and should be conducted by standardizing the type of teeth used to reduce variability and should include in vivo designs to better replicate clinical conditions and validate the preliminary findings of the present study.

Conclusion

Within the confines of the current study, upon evaluation of penetration and adaptation, the conventional sealant and silver nanocrystal-incorporated sealant performed similarly in most parameters. However, the conventional sealant demonstrated significantly better penetration at the fissure base. Correspondingly, the number of resin tags at the bottom of the fissure was significantly lower in the silver nanocrystal-incorporated sealant.

• Financial Support
  None.

Data Availability

The data used to support the findings of this study can be made available upon request to the corresponding author.

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Edited by

• Academic Editor: Wilton Wilney Nascimento Padilha

Publication Dates

• Publication in this collection
  27 July 2026
• Date of issue
  2026

History

• Received
  02 May 2024
• Reviewed
  08 July 2025
• Accepted
  15 Dec 2025