Comparative evaluation of different resinous infiltrants for masking efficacy of non-cavitated enamel lesions: a one-year randomized controlled trial

INTRODUCTION

Esthetic dentistry has evolved over the past few decades, focusing on improving the natural appearance of patients’ smiles through various dental treatments [1]. With the increased demand for invisible restorations and minimally invasive techniques, advanced restora­tive techniques and preventive dentistry support healthy, functional, and esthetic smiles [2]. Teeth cavi­ties are preceded by white spot lesions (WSLs); these spots of white enamel are caused by mineral loss in the sub-surface layer of the enamel. Their opaque color can cause long-lasting esthetic problems [3]. However, restoration of WSLs may require chipping away the enamel to the de-mineralized layer and, in some cases, entry through the dentin, which might harm the integrity of teeth [4]. Therefore, modern dentistry aims to manage WSLs non-invasively, prevent caries progression, and improve tooth strength, esthetics, and function [5]. Two major strategies are suggested to manage WSLs. The first is non-invasive strategy that involves secondary prevention and reversing lesions through re-mineralizing agents, and the second is minimally invasive strategy that masks and enhances es-thetic appearance using methods, such as bleaching, micro-abrasion, or caries infiltration [6].
On the other hand, after re-mineralization of the superficial enamel layer, the outermost layer of the lesion experiences higher mineral deposition than the lesion’s body, which blocks mineral ion transportation inside the lesion’s body. That may raise the possibility of long-term dark organic stains, and WSLs color enhancement cannot be fully realized [7]. Therefore, treatment should focus on preventing caries progression and enhancing esthetics by reducing opacity [8].
With the advancements in the dental field, WSLs’ masking has been improved. The most used method is the micro-invasive resin infiltration concept (Icon), which uses capillary forces to fill body lesion’s micro-pores with low-viscosity unfilled resins, after surface layer removal by 15% hydrochloric (HCL) acid etching. It bridges the gap that exists between restoration and prevention [9]. It follows the principle of minimally invasive intervention, avoiding destruction of healthy dental tissue, and preserving dental structure [10]. Moreover, it was found that composite sealant resins, when applied as per the Icon manufacturer instruction’s steps, have the ability to mask WSLs and penetrate sub-surface micro-pores similar to the Icon [11]. By employing various types of infiltrants, resin infiltration of non-cavitated WSLs has greatly decreased the presence of white spots and shielded the enamel from additional de-mineralization [12]. Since adhesive systems and other fluid resinous materials, such as composite surface sealants, are commonly available at the dental office, it would be very interesting for the clinician to know whether or not these materials can be used as a resin infiltrant agents for color masking and infiltrate micro-pores of WSLs [13].
Color evaluation can be done visually or using an intra-oral spectrophotometer device that provides ac-curacy, consistency, and reproducibility as well as an objective evaluation of color data besides numerical information [14]. Similarly, Vita Easyshade spectrophotometer, a highly sensitive spectrophotometer, was utilized to assess the masking color of the treated WSLs, demonstrating its reliability in both in vivo and in vitro settings [15].

OBJECTIVES

Based on the above-mentioned review, there is a need for a comparative evaluation of the effectiveness of composite sealants in masking WSLs versus Icon in a randomized controlled trial. Color change was evaluated with a VITA Easyshade V spectrophotometer over one-year follow-up period. The null hypothesis was that the composite sealant treatment would enhance the esthetics of WSLs in a way similar to the effects of Icon treatment within one-year of follow-up.

MATERIAL AND METHODS

ŚMATERIAL

Icon and two unfilled composite resin sealants (PermaSeal and OptiGuard) were used in this study. The materials utilized in the current trial are listed in (Table 1).

METHODS

SAMPLE SIZE CALCULATION

According to previous clinical investigation by Gözetici et al. [16], sample size was determined as the following assumed inputs: effect size (f = 0.19), number of groups (3), number of measurements (4), power (1-β = 0.95), significance level (α = 0.05), and correlation among repeated measures (0.5). The study included fifteen participants in each group (intervention and control groups) to ensure internal validity, with a power of 0.8 in each group using an alpha level of 0.05 (5%) and a beta level of 0.20 (20%). Type I error probability of testing the null hypothesis was set at 0.05. To account for a 25% potential loss during follow-up, the number of participants in each group was increased to twenty (resulting in 60 WSLs). IBM SPSS Power Release v. 3.1.6 was applied to compute the sample size.

STUDY DESIGN AND ETHICS

The current trial was designed to compare the efficacy of two composite sealants versus Icon in their ability to mask WSLs on permanent anterior teeth over one-year period. It was a single-center, double-blinded (assessor and patient), two parallel-armed randomized control clinical trial, with an equal allocation ratio (1 : 1). Consolidated standards of reporting trials (CONSORT) statement [17] was adhered to during the course of the present study. Al-Azhar University Ethics Committee, Faculty of Dental Medicine, granted complete ethical authorization (approval No. 350/466/08/10/19). The current study protocol was registered in the (https://clinicaltrials.gov/) database, with ID number: NCT05550116.

ASSESSORS AND OPERATOR CRITERIA

Prior to commencement of the trial, two dentists were trained and calibrated as assessors to identify eligible lesions accurately, and for observation by the primary investigator (MAW). The assessors did not participate in WSLs treatments.

STUDY SETTING AND CONSENT FORM

This randomized controlled clinical trial was conducted at the Faculty of Dental Medicine, Al-Azhar University, Cairo, Egypt. Every participant was informed about the investigation’s nature, agreed to participate, and signed a consent form (in the local language) prior to starting of the study. The flow chart illustrates a schematic summary of the research methodology steps (Figure 1).

ELIGIBILITY CRITERIA

Male and female adult Egyptian patients, who consented to participate in the trial were chosen from outpatient clinics of the Department of Operative Dentistry, Faculty of Dental Medicine, Al-Azhar University, Cairo, according to eligibility criteria of populations by the primary investigator (MAW) and assessors.

INCLUSION CRITERIA

1. Adult patients between 20 and 40 years old. 2. A mini­mum of 3 WSLs on patient’s labial surfaces of the six upper anterior teeth. 3. Mild and moderate WSLs based on Gorelick’s scale [18]. 4. Individuals with good oral hygiene and who were willing to attend follow-up appointments.

EXCLUSION CRITERIA

1. Cavitated lesions and stains on anterior teeth. 2. Patients with a significant medical history. 3 Periodontal disorders, such as dental mobility or periodontal pockets. 4. Current participation in another study.

BASELINE DATA COLLECTION

MEDICAL AND DENTAL HISTORY

Baseline data were gathered and documented using a report chart of every participant’s medical and dental history by the operator at the initial clinical visit. The report was anonymous, and patients were identified by their code numbers (the first letter of their first and last name, along with their date of birth) only registered. The operator saved the participant’s complete, detailed, and personal data on a separate sheet with the patient’s code number for further contacting.

CLINICAL EXAMINATION OF WSLS

WSLs were clinically evaluated by the operator and assessors after professional dental prophylaxis to detect WSLs below direct lighting, using a dental chair, light, and afterward drying the teeth via compressed air for 5 seconds. WSLs index by Gorelick et al. [19] was used to evaluate the teeth, and lesions with scores of 1 and 2 were only considered: score 1 – observable WSLs, which do not disturb the surface and occupy less than one-third of the surface (mild de-mineralization); score 2 – observable WSLs, which occupy over one-third of the surface, and have a roughened appearance but do not require restoration (moderate de-mineralization). This was confirmed via a DIAGNOdent pen 2190 laser fluorescence device (KaVo, Biberach an der Riss, Germany). Only WSLs with fluorescence loss ranging between 11 and 20 were included in the present study, indicating outer-half enamel caries (initial de-mineralization) [20].

ENROLLMENT OF PATIENTS

A total of 45 participants were examined clinically, out of whom 15 did not fulfill inclusion criteria and 10 declined to participate. Finally, 20 patients with at least three non-cavitated WSLs on their anterior teeth and fulfilling inclusion criteria were included in the study. Every patient completed consent papers. A flowchart illustrating the participants’ enrollment is shown in Figure 2.

GROUPING

A total of sixty non-cavitated WSLs on permanent upper anterior teeth were recorded from twenty participants. Every participant had three or more WSLs, which were randomly divided into three equivalent groups (n = 20) based on materials used to treat the lesions: one control group (Icon) and two intervention groups (OptiGuard and PermaSeal) composite sealants. Partici­pants with more than 3 WSLs were treated with Icon sealant.

BLINDING AND RANDOMIZATION

Due to differences in the utilization protocols of the materials employed, the operator was not blinded to material allocation, but patients and assessors were blinded. Two connected factors were necessary for randomization to occur, i.e., allocation concealment and sequence creation.

SEQUENCE GENERATION AND ALLOCATION

Patients were enrolled with at least three WSLs on the upper permanent anterior teeth, and were divided into three groups. Each patient received all three treatments, with each treatment applied to either right side (R) or left side (L) of patient’s mouth. To determine tooth and treatment option, each patient randomly selected a sealed envelope containing a written indication of either (R) or (L) from one container for the tooth side and number as well as the treatment option, i.e., (Icon), (OptiGuard), or (PermaSeal) from another contain-er. Each patient had a separate pair of containers, one for the tooth side and number, and the other for the treatment option.
Participants were provided with their code numbers (composed of the first letter of first and last name, along with date of birth) at the time of admission, with the treatment option to be chosen randomly from opaque closed envelopes. The service ensured allocation concealment by withholding the code until the person was enrolled into the study, which happened after all baseline measurements were completed.

PRE-OPERATIVE PROCEDURES

Following the eligibility screening, the main researcher (MAW) evaluated the teeth again for verification. Prior to baseline color measurement, every tooth with a WSL was scaled, and a rubber cup was used to polish the labial tooth surface with a fluoride-free pumice paste. Finally, after scaling and polishing, the teeth were cleaned under a water spray to remove any remaining debris.

BASELINE COLOR MEASUREMENT

Baseline WSLs color was assessed prior to material application (T0) using Vita Easyshade V device (VITA Zahnfabrik, Bad Sackingen, Germany) by the assessors. The device was calibrated in accordance with the manufacturer’s guidelines prior to every patient’s assessment. Each measurement was done after air-drying for 5 seconds and before complete dryness of the field. In this study, base shade determination of a natural tooth was chosen. This measurement allows to measure the base shade of a natural tooth using the corresponding VITA 3D MASTER shade guide.

WSLS TREATMENT PROCEDURES

After the measurements of baseline color, a rubber dam system was employed to protect gingival tissues and avoid moisture contamination. Application of each material was made by the same operator, the primary investigator (MAW), according to the following Icon manufacturer’s instructions [11]:
1. Icon (control group): In the first step, the Icon-Etch gel was applied for 2 minutes on WSLs surface. Then, the lesion was sprayed with water for 30 seconds and dried via an air/water syringe for 10 seconds. The second step involved applying sufficient Icon-Dry to the etched region, and letting it set for 30 seconds. Subsequently, the lesion was completely air-dried for 10 seconds. Next step required an Icon-Infiltrant application that lasted for 3 minutes, and dental floss was used to remove any residue. After that, a light-emitting diode (LED) was applied to cure the resin infiltration for 40 seconds, using a LED-curing device (Elipar S10, 3M ESPE, St Paul, Minnesota, USA) with an intensity of 1,200 mW/cm². Finally, one more layer of Icon-Infiltrant was applied for another minute and light-cured for 40 seconds.
2. The Icon manufacturer’s instructions were followed for applying composite sealants (OptiGuard and PermaSeal) [11]. The first step involved Icon-Etch, and the second step, Icon-Dry. The two composite sealants were applied as Icon-Infiltrant application steps (third step), and then rubbed continuously for 3 minutes.
Extra resin was removed, followed by light-curing for 40 seconds. Every sealant was re-applied and brushed for 60 seconds. After removing extra resin, the resin was light-cured for 40 seconds.
3. Finally, after all materials were applied, the treated WSLs were polished with a rubber cup and polishing paste for a smooth, sheen surface, and to prevent food stains.

PATIENT INSTRUCTIONS

Following the clinical procedures, all patients in the study received oral hygiene training on the first visit. They were advised to avoid consuming foods and beverages, which could cause tooth staining or acid erosion, and to brush their teeth twice daily with a soft-textured toothbrush and fluoridated toothpaste.

OBSERVATION

Observation and data collection were completed by the assessors, who did not participate in WSLs treatments. The resin-infiltrated WSLs were evaluated after treatment with the Vita Easyshade V device to assess WSLs’ color change (ΔE) at the following time intervals: T0 – before the application of materials (baseline); T1 – immediately after treatments; T2 – three months later; T3 – six months later; and T4 – 12 months later. Prior to every color assessment, WSLs were polished using a fluoride-free polishing paste.

OUTCOMES

Primary outcome was to compare the ΔE values of the treated WSLs between different groups. This analy-sis sought to evaluate any variations in the effectiveness of treatments and determine if some treatments yielded more significant color improvements than others. Secondary outcome was to assess the treated WSLs’ durability by calculating the ΔE values at different observation times. The objective was to measure and analyze the extent of color improvement achieved after the treatment.

STATISTICAL ANALYSIS

SPSS version 21 was utilized for statistical analysis. Kolmogorov-Smirnov test was used to confirm the normality of distribution. One-way ANOVA test was employed to contrast the efficacy of different groups at different follow-up intervals. To evaluate the efficacy of each material at various follow-up times, another one-way ANOVA test was performed. Post-hoc Tukey test was used to perform multiple comparisons within each pair of groups. Additionally, Tukey test was performed to contrast the two intervals in every group. P-value ≤ 0.05 was chosen as statistically significant.

RESULTS

BASELINE DATA AND FOLLOW-UP

A total of 20 patients, with a mean age of 30.4 years participated in this clinical study. 55.15% of the patients were females (n = 11), with a mean age of 30.2 years, and 44.85% were males (n = 9), with a mean age of 30.7 years. Maxillary teeth with at least three WSLs were treated (60 teeth included into the trial). A total of 16 patients with a mean age of 27.9 years (9 females with a mean age of 28.2 years, and seven males with a mean age of 27.5 years), with 48 treated WSLs (n = 16 per group) were presented in T4. Four of the patients were excluded, as they did not attend follow-up visits. The flow diagram of the study is displayed in Figure 3.

EFFECT OF DIFFERENT MATERIALS USED ON WSLS’ COLOR CHANGE (ΔE)

Statistical analysis (ANOVA test) of the ΔE showed that there was a significant variation in color change across Icon and composite sealant materials at every follow-up interval (p < 0.00001). The post-hoc Tukey test displayed statistically significant variations among the Icon group and the two composite sealants groups (PermaSeal and OptiGuard) at all tested follow-up visits (p < 0.05). The Icon group displayed the greatest significant improvement in the ΔE value, followed by the composite sealants groups. However, there were no significant differences among the composite sealants (OptiGuard and PermaSeal) groups at follow-up intervals (p > 0.05) (Figure 4, Table 2).

EFFECT OF TIME ON WSLS COLOR CHANGE (ΔE) AFTER MATERIALS’ APPLICATION

Statistical analysis of color change (ΔE) at different follow-up visits (immediate, 3, 6, and 12 months) for the different materials used revealed a statistically significant difference among all tested groups, as deter-mined by ANOVA test (p < 0.00001).
Furthermore, a significant decrease in the mean value of ΔE was observed within all materials over time. For all groups, the results showed that the highest mean ± SD was recorded immediately after application, followed by 3 and 6 months, respectively. Whereas the lowest mean ± SD was recorded for the 12 months interval (Figure 5, Table 3).

DISCUSSION

With the advancements in the dental field, treatment modalities have been developed to mask the appearance of WSLs. The most common method is micro-invasive resin infiltration that fills the lesion’s micro-pores via low-viscosity unfilled resins, after surface layer removal by acid etching [9]. This minimally invasive approach pre-serves dental structure and prevents tissue destruction [10].
The Icon is regarded as the highest standard for WSLs’ management that effectively stops caries activity and promotes optimal esthetic [18, 21]. Similarly, composite sealants are light-cured, with low-viscosity resins, which contain little-to-no fillers. Such sealants are designed to fill in micro-defects on restoration surfaces, aiming to keep color consistency, and minimize flaws to preserve the integrity of surface [22].
Subjective color evaluation has a number of restrictions and can be incorrect. Compared with optical qualitative evaluation, spectrophotometry, spectroradiometers, colorimetry, and digital pictures are more reliable measuring techniques for an objective color evaluation [23]. Therefore, in the current study, color measurement was done using an intra-oral spectrophotometer device, VITA Easyshade V (VES). The reliability of VES was 96.4% when compared with other dental shade-matching devices in a study assessing the precision and dependability of dental shade-matching tools. It was concluded that VES is an effective method for evaluation of the color of teeth [24]. The objective of the current randomized controlled trial was to compare the efficacy of two composite sealants versus Icon in the ability to mask WSLs on permanent anterior teeth over 12 months of follow-up.
The results displayed that every group showed a significant improvement in the color change (ΔE) after immediate application, exceeding the reference threshold (below 3.7) for visual color changes between objects [13]. This outcome might be clarified by refractive index (RI) of the resins used for infiltration, which is very close to the RI of sound enamel. The replacement of air or water in micro-pores with resin reduces light scattering within the enamel, and allows low-viscosity resins to infiltrate into WSLs, blocking diffusion pathways completely [25].
Furthermore, the process of resin infiltration involves applying 15% HCL to the lesion surface layer to promote erosion and allow resin infiltration into the lesion body. Then, Icon-Dry (ethanol) is applied to re-move water remnants in micro-pores. The highly fluid resins penetrate the lesions, blocking cariogenic acid diffusion paths, and promoting early caries arrest [9].
Variations in light scattering inside lesions serve as the foundation for WSLs’ masking using the resin infiltration technique. Sound enamel has a RI of 1.62, and micro-pores filled with water or air have RIs of 1.33 and 1.0, respectively. These differences results in the dispersion of light, producing an opaque, white look, particularly when dried [26]. The Icon resin (RI, 1.46) fills the micro-pores of infiltrating lesions [25] and composite sealants (RI of Bis-GMA, 1.54), which are very similar to the RI of healthy enamel [27]. These resins, unlike watery mediums, cannot evaporate, making the difference between healthy enamel and micro-pores insignificant. WSLs resemble neighboring healthy enamel in appearance, resulting in an immediate improvement in esthetic appearance [26].
Regarding composite sealants, they are used to fill the roughness on the surface of composite restoration, and penetrate the structural micro-defects and marginal gaps via capillary action, and sealing them. Also, they have low-viscosity resins and high wetting abilities [28]. A previous study reported that the PermaSeal composite sealant displayed excellent penetration into etched enamel due to its low-viscosity resin, which allows pene­tration into the etched enamel surface [29].
Again, our findings showed a significant variation among the Icon and composite sealants groups immediately after treatment and at 3, 6, and 12 months of follow-up times, with the Icon group achieving the highest ΔE. This may be due to the fact that Icon has superior infiltration ability due to its low-viscosity monomer and low molecular weight (TEG-DMA) compared with composite sealants. This leads the infiltrated lesions with composite sealants to reduced infiltration and in-creased void density, which raises light wave RI [30]. According to our findings, the null hypothesis of the study was rejected, because Icon demonstrated significantly higher ΔE values than composite sealants over 12 months of follow-up.
Additionally, the depth of WSLs beyond the resin’s maximum infiltration capacity can hinder complete removal of lesions [31]. A previous study by Belli et al. [32] found a relationship between the lesion depth and WSL color intensity, suggesting that color intensity may estimate the depth of enamel de-mineralization. Moreover, the deep penetration of resin into sub-surface’s defects is responsible for the lesions’ enhanced color [33]. Our results are in line with those of Goda et al. [34], who evaluated the impact of Icon on WSL masking and its longevity in comparison with a standard adhesive resin using VITA Easyshade. The authors found that immediately after materials’ application and at all follow-up visits (1 year), Icon displayed a significant color enhancement. At the same time, the adhesive showed improvement, but not as significantly as Icon. Howev-er, our results do not agree with those of Theodory et al. [11], who observed that the composite sealants had slightly higher masking ability than Icon due to their yellower color and higher concentration of photo-initiators. This may enhance WSLs sealants’ masking abilities, although they have less penetrating capacity than Icon.
Regarding follow-up times, the current trial revealed a significant decrease in ΔE over follow-up visits for all groups, indicating a decrease in the efficacy of resin infiltrants in treating WSLs over time. This may be due to the acid etching that can lead to the loss of outer protective layer of a lesion, allowing fluids and stains to enter the lesions’ micro-pores, making them susceptible to staining [35]. Our results are in line with those of Kannan et al. [18], who showed a notable enhancement of WSLs esthetics immediately with the Icon treatment, but after three months, it was significantly reduced. Likewise, our outcomes are consistent with Rohym et al. [9], who found that Icon infiltrated surfaces showed a significant increase in discoloration after 12 months.
Generally, resinous materials are subjected to both extrinsic and intrinsic pigmentation over time, degra-dation, and wear, and influenced by water absorption rates. Surface pigmentation occurs due to plaque ac-cumulation, allowing coloring agents to penetrate the resin body. While intrinsic pigmentation appears due to alterations in the monomer matrix over time. Also, the oral cavity’s aqueous environment and temperature changes affect the optical properties of these materials [36].
Another reason is that the degradation of resin’s infiltrant increases pore volume, which is filled with water, potentially increasing enamel opacity due to a lower IR of water [37]. Sub-surface micro-pores that are not properly filled, arise from non-homogenous regions inside the penetrated material caused by oxygen inhibition and polymerization shrinkage of the resin infiltrant [38]. Contrary with our results, Ritwik et al. [39] assessed the color stability of Icon, dental adhesive, and sealant system. They observed that all tested mate-rials showed color change, and Icon exhibited the greatest color change in de-mineralizing solution.
The limitations of this study are the subjective measures, such as patient satisfaction that was not directly evaluated, a relatively short follow-up period, and evaluation of color only. Therefore, future studies should incorporate subjective measures of patient satisfaction and extend the duration of trials to assess color sta-bility over a longer period. Additionally, addressing other important aspects, such as caries activity, would further enhance the comprehensive evaluation of resinous infiltrants in managing non-cavitated enamel le-sions.

CONCLUSIONS

Within the limitations of this in vivo trial, we can conclude that the tested composite sealants and the Icon resin infiltration have the immediate ability of masking WSLs. However, the esthetic camouflage of the Icon resin infiltration is better than that of composite sealants. Additionally, the Icon resin infiltration shows more favorable color stability compared with composite sealants.

DISCLOSURES

1. Institutional review board statement: The study was approved by the Al-Azhar University Ethics Commit-tee, Faculty of Dental Medicine, granted complete ethical authorization (approval No. 350/466/08/ 10/19).
2. Assistance with the article: None.
3. Financial support and sponsorship: None.
4. Conflicts of interest: The authors declare no potential conflicts of interest concerning the research, authorship, and/or publication of this article.

References