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CC BY 4.0 · European Journal of General Dentistry
DOI: 10.1055/s-0045-1809141
Original Article

Spectrophotometry Comparison and Microleakage Analysis of Bioactive Glass-Reinforced Resin Infiltrants: An In Vitro Study

Syed Zubairuddin Ahmed
1   Department of Restorative Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
,
Sukainah Zaki Alzayer
2   College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
,
Yasmeen Hassan Alsaeed
2   College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
,
Sakinah Hussain Al Isam
2   College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
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Abstract

Objective

White spot lesion management has evolved into minimally invasive approaches, including resin infiltration material and TEETH samples (without any material) used as negative control group.

Materials and Methods

Sixty permanent noncavitated premolars were sectioned into two halves buccolingually (n = 120). Both surfaces artificially produced a white spot lesion and randomly distributed; bioglass (45S5), borosilicate-based bioactive glass (B-BAG), fluoride-based bioactive glass, commercial resin (ICON, as +ve control), and resin without filler (Pure Resin). All the samples were immersed in coffee, soda, orange juice, and artificial saliva for 28 days, and color stability was measured weekly. For penetration depth analysis, the teeth were immersed in 2% methylene blue dye solution for 24 hours at 37°C. The microleakage analysis was performed for all the samples using the stereomicroscope.

Results

There were significant differences in the color properties of all the samples for all the groups. Immersion in coffee and soda resulted in significantly increased color alteration compared with orange juice (p = 0.001). The commercial resin-infiltrated group exhibited the highest staining values (p = 0.001). However, following artificial saliva immersion, commercial material has successfully maintained its color properties. After Pure Resin, ICON exhibited the lowest microleakage values while the B-BAG showed the highest microleakage in all the groups.

Conclusion

The exposure of specimens to colored solutions resulted in significant color alteration.


 

Keywords

bioactive glass - color stability - microleakage - resin infiltration - spectrophotometry

Introduction

According to the World Health Organization Global Oral Health Status Report (2022), oral diseases impact approximately 3.5 billion people globally, with middle-income nations accounting for three out of four cases.[1] The market for cosmetic dentistry was estimated to be worth USD 33.6 billion in 2022 and is projected to expand at a 13.5% compound annual growth rate between 2023 and 2030.[2] Aesthetic dentistry has a strong connection with incipient caries, which is the foundation of all the caries processes and is generally known as white spot lesion (WSL).

Noninvasive or minimally invasive methods have replaced traditional invasive restorations in the management of dental cavities.[3] Resin infiltration is one of the microinvasive methods. Carious lesions up to the first third of the dentin can be treated with it. Allowing the resin to permeate the porous enamel through capillary action stabilizes, fills, and reinforces demineralized enamel without compromising the integrity of the tooth structure. Another element influencing the restoration's success is color stability. It might be impacted by external and intrinsic variables. Eating acidic food can lower the pH of the oral cavity to 5.5, which can lead to the breakdown of hydroxyapatite. Moreover, they could cause swelling processes that break down resin monomers.[4] A study revealed that the ICON discolored more over time in comparison to other sealant materials (nanohybrid sealant, clear fissure sealant with fluoride, and nanofilled composite).[5]

The resistance to microleakage determines the efficacy of resin infiltration treatment. The viscosity of the resin material has an impact on microleakage. Because resin material has a low viscosity, it can pass through the enamel's porous surface.[6] [7] Reducing microleakage at the restoration and tooth interface is a key factor in clinical success for resin monomers.[8] [9] [10] Organic dyes are frequently employed in vitro to measure leakage.

This study compares the spectrophotometric characteristics and microleakage analysis of experimental resin infiltrants in vitro. The objective was to assess the degree to which these new materials replicate the optical properties of natural enamel and their ability to penetrate WSLs in comparison to currently available commercial treatments. Since commercial resin infiltrant ICON has been used and proven successful in clinical settings, it will act as a control group and performance soda-benchmark.

It is hypothesized that all the solutions will affect the color parameters of the resin materials. However, the experimental materials might stain more due to the presence of the filler particle in their composition. The microleakage might also be higher in the experimental material because of the presence of the filler particles.


 

Materials and Methods

Synthesis and Preparation of Experimental Resin Material

The chemicals used in this study, purchased from Sigma Aldrich (St. Louis, Missouri, United States), were of analytical grade. The resin infiltrant was prepared using trimethylene glycol dimethacrylate (TEGDMA, 74.5 wt.%) and diurethane dimethacrylate (24.5 wt.%) as resin monomers, with camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB) as photoinitiators. After optimizing the ratio, the monomers were mixed for 60 minutes at room temperature, followed by adding 0.5 wt.% CQ and 0.5 wt.% EDAB, which were mixed for another 60 minutes in a dark environment to create the resin-only positive control group (R1). Following the resin preparation, three different fillers were added to it to complete the final experimental groups, namely, bioglass “45S5” (G018–144; Schott Glass AG, Mainz, Germany) as the first filler, borosilicate bioactive glass as the second, while fluoride-substituted bioactive glass was the third filler material. The filler was added to the resin infiltrant at 2.5 wt.% to create experimental resin infiltrants. The blending process involved manual stirring, and magnetic stirring for 24 hours, followed by ultrasonic mixing for 15 minutes. All the experimental materials groups were named bioglass (45S5), borate-doped bioactive glass (B-BAG), fluoride-doped BAG (F-BAG), and Pure Resin (PR). The ICON (DMG-America, Ridgefield Park, New Jersey, United States) served as the commercial control material. The study included tooth-only (TH) as a negative control and commercial control (ICON) as a positive control.


 

Sample Size Calculation

The power calculation formula employed the study's means and standard deviation (SD) with an 80% confidence interval and the ClinCalc program. A sample size of 5 was obtained for every group, with a significant level of p = 0.05. Based on the following formula the sample size was calculated[11]:

n = σ2 × (Z1-α/2 + Z1-β)2 / (μ0 - μ1)2 (1)

Two different analytical techniques were used, and there is a variation in the sample size for each characterization. For the spectrophotometry, n = 5 was the final count, while for the microleakage analysis, n = 3 was the final number of samples per group.


 

Collection of Teeth Samples

Sixty extracted human premolars (for orthodontic treatment purposes) were collected from the Dental Hospital (Imam Abdulrahman Bin Faisal University, Dammam, Kingdom of Saudi Arabia) and bifurcated (buccolingually) to accommodate the required number of teeth samples (n = 120) to execute this experimental study.


 

Inclusion and Exclusion Criteria

Healthy, sound, and noncavitated premolar teeth (maxillary and mandibular), teeth that have been extracted for orthodontic/periodontal purposes, the age of the patients was kept between 13 and 40 years, teeth extracted within 4 weeks before sample preparation, and either gender, male/female.


 

Cleaning and Preservation of Teeth Samples

After removing all the debris from the surface, the samples were disinfected with an ethanol solution (70/30) and then stored in a thymol solution (0.1%) until further use. Before sectioning the teeth, two calibrated examiners thoroughly examined them with a light stereomicroscope for any cracks or damage.


 

Group Distribution

Samples were randomly distributed according to the restorative material into six groups. Group 1, bioglass (45S5) required 20 samples (n = 20), group 2, B-BAG required 20 samples (n = 20), group 3, F-BAG required 20 samples (n = 20), group 4 (ICON resin infiltration, as +ve control) required 20 samples (n = 20), and group 5, resin without bioactive glass (PR) required 20 samples (n = 20). For the microleakage analysis, each material group required three samples (n = 3), so 18 (n = 18) were included.


 

Preparation of Demineralization Solution and Production of WSL

The demineralization solution was prepared according to previous research.[12] To demineralize the teeth, a 4 mm × 4 mm window was made in the enamel on the buccal surfaces, and the surrounding areas were covered with a single coat of acid-resistant nail polish (Maybelline, Manhattan, New York, United States). The only window surfaces that were demineralized were those that were uncovered. To create artificial WSLs, the samples were subsequently submerged in a demineralization solution for 96 hours at 37°C. Note that 0.05 mM acetic acid (lot # J3530; Honeywell, Offenbach, Germany), 2.2 mM CaCl2 (lot # 5119; Cepham Life Sciences, Fulton, Maryland, United States), and 2.2 mM Na3PO4 (lot # 22141–27948; Research Products Int., Mount Prospect, Illinois, United States) were used to generate the demineralization solution. The pH of the solution was adjusted to 4.4 using a few drops of KOH (lot # BCCD2228; Sigma Aldrich).


 

Preparation of Artificial Saliva Solution

[Table 1] showing the composition followed by the past research[13] prepared the artificial saliva. For 28 days, every tooth sample was submerged in the artificial saliva solution (pH = 7). To keep each sample's surface-to-volume ratio constant, they were submerged in different containers. To maintain the mixture's efficacy, a freshly blended solution was used each week to replace the fake saliva solution.

Table 1

Composition of artificial saliva solution with their lot and CAS numbers along with their quantities that have been used for the preparation

No.

Chemical name (Lot #, CAS #)

Quantity

1

NaCl (Thomas Scientific lot # 17G3002) (7647–14–5)

0.400 g

2

KCl (PanReac AppliChem lot # 0001355892) (7447–40–7)

0.400 g

3

NaH2PO4. H2O (Research Products Int. Lot. # 22141–27948) (7558–80–7)

0.69 g

4

CaCl2. H2O (Cepham life Sciences Lot # 5119) (10043–52–4)

0.795 g

5

Na2S. 9H2O (General Reagent Lot # P1575781) (1313–82–2)

0.005 g

6

NaOH (Sigma Aldrich Lot # STBH4233) (1310–73–2)

1 mM

Abbreviation: CAS, Chemical Abstracts Service.



 

Sectioning and Production of WSL Production on Teeth Specimens

The teeth were suctioned into two halves buccolingually with the help of a low-speed straight handpiece ([Fig. 1A and B]) with a diamond disc.[14] The teeth were held with the help of specific artery forceps to make sure, not to be slipped. Then, the teeth were suctioned into two halves buccolingually with the help of a low-speed straight handpiece with a diamond disc.[14] Once the teeth were cut, all samples were covered with nail varnish, except for a 4 × 4 mm section on the buccal/lingual surface that was intended to be used to produce artificially produced WSLs and secured with a masking tape. Once the nail varnish was dried, the masking tape was removed, and the samples proceeded to the demineralization solute for the production of WSL ([Fig. 1C]).

Zoom
Fig. 1 (A–C) Bifurcation of teeth samples for the group distribution of samples. (A) During the process of cutting the tooth, (B) the tooth has been cut into two halves, and (C) window preparation for the demineralization by covering the whole tooth with nail varnish. (D) Samples immersed in the demineralized solution to create the white spot lesion (WSL) on the teeth separately.

After calculating the surface-to-volume ratio[15] the samples were dipped in the solution (10 mL/sample) to maintain their efficacy. For this purpose, four samples were put in a glass bottle with enough capacity for the solution ([Fig. 1D]). After 96 hours, the lesions were created. All the samples were carefully cleaned with deionized water.

The samples were then air-dried to ensure the removal of demineralizing solution remnants and to avoid getting false-positive results. It was anticipated that 96 hours of immersion of untreated enamel specimens in the demineralization solution would produce 100-m deep enamel lesions, which is equivalent to around 3 months of actual time.[16]


 

Application of Resin Infiltration on Specimens (Experimental/Commercial)

After the production of WSL on the teeth surface, materials were applied according to the protocol described by the manufacturer of the commercial material.[17] All the experimental resin groups and the commercial material followed the same protocol for the application of the resin material mentioned by the manufacturer of the commercial material to maintain standardization ([Fig. 2]): etching for 120 seconds (15% HCL), rinsing for 30 seconds, air drying for 10 seconds, ICON DRY for 30 seconds, air drying for 30 seconds, resin material (ICON/experimental) for 180 seconds, and light-emitting diode (LED) light cure (3M ESPE [Elipar S 10], St. Paul, Minnesota, United States) for 40 seconds and then the second layer of ICON/experimental resin for 60 seconds and LED light cure (3M ESPE [Elipar S 10]) for 40 seconds. All the material applications were applied in a darkroom to prevent premature curing.

Zoom
Fig. 2 (A–D) Application armamentarium of the resin infiltrants. (A) Light curing machine, (B) experimental resin infiltration, (C) commercial resin infiltration, and (D) polishing/finishing discs. (E–H) Immersion of teeth samples in different mediums. (E) Containers with black coffee solution, (F) containers with soda and teeth immersed into it, (G) containers with citric acid solution with immersed teeth, and (H) containers having artificial saliva and teeth immersed into it.

 

Finishing and Polishing Procedure

Surface irregularities were corrected by repolishing all specimens with OptiDisc (Nobel Biocare Services AG - Kerr, Kloten, Switzerland) finishing discs mounted on a dental low-speed handpiece, resulting in standardized surface characteristics. Finishing discs were used to contour the material and to smooth out the rough surface of the material, as shown in [Fig. 2].


 

Immersion of Samples into the Solutions

Each group was immersed in four different immersing media (coffee, soda, orange juice, and artificial saliva). The pH value of each solution was measured using a portable pH meter (Hanna Instruments HI 8424 pH probe). The soda solution had a pH of 2.52, orange juice was 3.92, black coffee was 5.08, and artificial saliva had a pH of 7.0. [Table 2] mentions all the pHs of different immersing media.

Table 2

Different mediums along with their pH, for immersion of the color stability

Immersion media

pH values

1.

Soda

2.52

2.

Orange juice

3.92

3.

Black coffee

5.08

4.

Artificial saliva

7.0

All the samples were immersed in the media at 37°C temperature in an incubator. All the solutions were replaced daily to maintain a constant pH value. The color stability was recorded weekly for 4 weeks, from week 1 to week 4, for all the teeth and every solution ([Fig. 2]).

After the resin was infused, all the samples were immersed for 28 days in a coffee staining solution (Starbucks Espresso Roast coffee from Nespresso, Nestlé S.A., Vaud, Switzerland). The duration of 28 months for coffee consumption would be equivalent to 28 days of storage at a rate of 24 hours per day.[18] Fresh coffee was utilized daily to replace the old one to maintain the pH value constant.

For the evaluation of soda immersion, von Fraunhofer and Rogers's[19] procedure was employed. A test or beverage immersion duration was used to investigate enamel breakdown in beverage solutions.

During the investigation, all of the teeth were kept in orange juice (pH: 3.9, Farms 100% Pure Orange Juice, Phoenix, Arizona, United States). The new one replaced the juice daily to keep the efficacy vital throughout the immersion.

Artificial saliva[20] was solely employed in this investigation to measure pH+; its acid-based characteristics, not its microbial burden, were interesting. By moving ions from the enamel into the saliva and vice versa, pH in vivo initiates the demineralization/remineralization process in the oral cavity.


 

Color Stability Measurement Analysis

Each sample was covered by a black tape, exposing only the window. For each sample, baseline color measurements were done using a spectrophotometer (Color-Eye 7000A Spectrophotometer, Gretag Macbeth, New Windsor, New York, United States), [Fig. 3A]. The following formula helped calculate ∆E and compare the values on day 1 and after day 28 of the immersion protocols for all the solutions used in this research:

Zoom
Fig. 3 (A–C) Process of spectrophotometry analysis. (A) Color-Eye 7000A spectrophotometry machine, (B) the application of tooth structure onto the lens to get the readings, and (C) prepared sample ready to be applied onto the machine with the black tape covering the surroundings to cover the lens. (D–F) shows the (D) stereomicroscope, (E) samples immersed in methylene blue dye, and (F) samples prepared for the microscopic analysis.

ΔE*ab = √ (L*2–L*1)2 + (a*2–a*1)2 + (b*2–b*1)2 (2)

where L* denotes a subtle difference between standard and sample colors, a* corresponds to the difference in redness or grayness, and b* implies blueness yellow.


 

Microleakage Measurement Analysis

The designated group of teeth samples for the microleakage analysis were immersed in a 2% methylene blue solution for 24 hours at 37°C (the ISO/TS 11405 immersion period was followed).[21] Methylene blue dye was used in this study to assess resin infiltrant leakage and the tooth interface because its molecular size (0.5–0.7 nm) is smaller than that of bacteria.[22] After the immersing time, the samples were washed with tap water and cut into two halves mesiodistally, with the help of the straight handpiece having a diamond-metal bonded low-speed saw (Ted Pella, Inc., United States). The samples were cut, showing the area having the resin material leakage with it. The specimens were washed again with tap water, dried, and prepared for microscopic examination. A stereomicroscope (Dino-Lite, Taipei, Taiwan) was used to check the microleakage with different resolutions ([Figs. 3] and [4]). The observations were made at multiple locations, and the average was compiled by the material's penetration ([Fig. 4]). The following grade was assigned to microleakage based on methylene blue penetration measurements[10]:

Zoom
Fig. 4 (A–E) Stereomicroscopic view of teeth samples after being immersed in the methylene blue solution to check the microleakage. (A) 45S5, (B) borosilicate-based bioactive glass (B-BAG), (C) fluoride-based bioactive glass (F-BAG), (D) ICON, and (E) Pure Resin. (F) Percentage of methylene blue penetration failure in percentage in all the resin groups.

  • 0 = methylene blue dye did not penetrate at all

  • 1 = the external hemisphere of the enamel is penetrated by methylene blue

  • 2 = the internal hemisphere of the enamel is penetrated by methylene blue

  • 3 = the external hemisphere of the dentin is penetrated by methylene blue

  • 4 = the internal hemisphere of the dentin is penetrated by methylene blue


 

Statistical Analysis

Statistical analysis was performed using computer software (SPSS), with the level of significance kept at 0.05. Descriptive statistics, including the mean and SD values, were calculated for each color coordinate for all the groups. One-way analysis of variance by the factor of material was performed with the differences in color (∆E*ab) and three-color coordinates (CIE L*, CIE a*, and CIE b*).


 

 

Results

All the results of the spectrophotometric values of all the experimental and commercial resin infiltrators are presented in the form of four tables for every immersion medium (coffee, soda, citric acid, and artificial saliva). The first table represents the data for the duration after the first week of immersion, while the second table represents the data after the immersion of the samples for 4 weeks; however, the third table represents the data of the difference of values between week 1 and week 4 of the immersion of all the samples.

The difference between the ΔE values between week 1 and week 4 are presented in [Table 3]. After immersing into the coffee solution for 4 weeks, the ICON group appeared as the one that exhibited the highest ΔE values (3.34 ± 0.09), while the PR group showed the lowest values (1.79 ± 0.77) after 4 weeks.

Table 3

Mean and SD values of the difference between week 1 and week 4 (ΔL, Δa, Δb, and ΔE) after week 4 of immersion in coffee solution

Coffee solution (difference between week 1 and week 4)

Group name

L4-L1

a4-a1

b4-b1

del E4-del E1

45S5

4.05 ± 0.29

0.38 ± –0.03

1.33 ± –0.19

1.04 ± 0.14

B-BAG

2.28 ± 0.1

0.56 ± –0.19

1.85 ± –0.3

0.9 ± 0.05

F-BAG

2.82 ± 0.01

0.21 ± –0.07

2.31 ± –0.07

1.05 ± 0.03

ICON

1.79 ± 0.12

0.22 ± –0.1

3.21 ± –0.06

1.11 ± 0.08

Pure Resin

2.82 ± –0.61

1.37 ± 0.05

1.14 ± 0.45

0.57 ± 0.03

Tooth

2.92 ± –0.13

0.45 ± 0.00

3.43 ± –0.72

1.51 ± 0.37

Abbreviations: B-BAG, borosilicate-based bioactive glass; F-BAG, fluoride-based bioactive glass; SD, standard deviation.


[Table 4] displays the variation in the ΔE values from week 1 to week 4. Following a 4-week immersion in the soda solution, the ICON group demonstrated the highest ΔE values (2.66 ± 0.47), whereas the F-BAG group displayed the lowest values (1.33 ± 0.68).

Table 4

Mean and SD values of the difference between week 1 and week 4 (ΔL, Δa, Δb, and ΔE) after week 4 of immersion in soda solution

Soda solution (difference between week 1 and week 4)

Group name

L4-L1

a4-a1

b4-b1

del E4-del E1

45S5

1.77 ± 0.19

0.65 ± –0.03

0.09 ± 0.1

0.89 ± 0.03

B-BAG

2.02 ± –0.63

1.01 ± –0.1

1.23 ± –0.06

1.52 ± 0.15

F-BAG

1.55 ± 0.52

0.25 ± –0.02

0.03 ± 0.32

0.85 ± 0.23

ICON

2.69 ± –0.41

0.58 ± 0.41

0.75 ± 0.39

1.28 ± 0.26

Pure Resin

1.57 ± 0.09

0.08 ± 0.19

1.02 ± 0.36

0.95 ± 0.26

Tooth

4.13 ± 0.01

0.43 ± 0.95

3.51 ± 1.01

2.72 ± 0.21

Abbreviations: B-BAG, borosilicate-based bioactive glass; F-BAG, fluoride-based bioactive glass; SD, standard deviation.


[Table 5] represents the difference between week 1 and week 4 of the citric acid solution. All the groups represent comparatively higher values compared with other immersion media. The B-BAG group presented with the highest ΔE values (7.13 ± 1.18), while the 45S5 group presented with the lowest ΔE values (4.75 ± 0.75).

Table 5

Mean and SD values of the difference between week 1 and week 4 (ΔL, Δa, Δb, and ΔE) after week 4 of immersion in citric acid solution

Citric acid solution (difference between week 1 and week 4)

Group name

L4-L1

a4-a1

b4-b1

del E4-del E1

45S5

5.44 ± 0.47

0.09 ± 0.46

0.34 ± 0.32

1.69 ± 0.39

B-BAG

7.19 ± 1.18

0.20 ± 0.39

0.49 ± 0.07

2.18 ± 0.36

F-BAG

6.69 ± –0.38

1.43 ± 0.02

0.85 ± –0.12

2.49 ± 0.14

ICON

6.03 ± 0.33

0.23 ± 1.35

0.19 ± –1.05

1.20 ± 0.39

Pure Resin

7.11 ± 0.30

1.23 ± 0.71

1.66 ± 0.14

3.31 ± 0.03

Tooth

8.50 ± 0.32

1.69 ± 0.14

4.17 ± –0.01

3.03 ± 0.27

Abbreviations: B-BAG, borosilicate-based bioactive glass; F-BAG, fluoride-based bioactive glass; SD, standard deviation.


The difference between week 1 and week 4 is presented in [Table 6] for the immersion of the artificial saliva solution. For the ΔE values between the differences of those weeks, the F-BAG group exhibited the highest values (2.21 ± –0.48), whereas the ICON showed the lowest values (0.07 ± –0.002).

Table 6

Mean and SD values of the difference between week 1 and week 4 (ΔL, Δa, Δb, and ΔE) after week 4 of immersion in artificial saliva solution

Artificial saliva solution (difference between week 1 and week 4)

Group name

L4-L1

a4-a1

b4-b1

del E4-del E1

45S5

7.39 ± –0.40

2.04 ± 0.01

0.69 ± 0.001

1.52 ± 0.12

B-BAG

2.38 ± –0.4

0.4 ± 0.05

1.62 ± 0.02

0.38 ± 0.08

F-BAG

7.65 ± 0.51

0.13 ± 0.96

0.25 ± 2.2

2.21 ± 0.48

ICON

0.44 ± 0.06

1.33 ± –0.01

1.96 ± 0.02

0.07 ± 0.002

Pure Resin

4.26 ± 0.74

0.73 ± 0.03

0.9 ± –0.08

1.93 ± 0.36

Tooth

5.07 ± 0.24

1.8 ± –1.11

0.37 ± –0.31

1.22 ± 0.43

Abbreviations: B-BAG, borosilicate-based bioactive glass; F-BAG, fluoride-based bioactive glass; SD, standard deviation.


[Fig. 4] and [Table 7] show the resin groups' microleakage values. In this investigation, ICON and PR inhibited methylene blue penetration, whereas the rest of the groups appeared to resist less and allowed the penetration of the methylene blue dye. In the 45S5, B-BAG, and F-BAG groups, values did not significantly differ from one another, whereas they did allow the penetration of the methylene blue dye till the inner enamel layer was 40%, while the dye could not reach the outer dentin layer. The PR and ICON groups resisted well and did allow the methylene blue penetration to the enamel's inner layer at 10% while they did not allow the dye to reach the dentin's outer layer.

Table 7

The methylene blue penetration scores

Group name

Microleakage scores

0

1

2

3

4

1

45S5

0

0

8

0

0

2

B-BAG

0

0

8

0

0

3

F-BAG

0

0

8

0

0

4

ICON

0

4

0

0

0

5

Pure Resin

0

3

0

0

0

6

Tooth

1

0

0

0

0

Abbreviations: B-BAG, borosilicate-based bioactive glass; F-BAG, fluoride-based bioactive glass.



 

Discussion

In the current investigation, the specimen's color coordinates were noted at various points in time following its exposure to the coloring chemicals. Since color is a complicated phenomenon, several variables, including illumination, translucency, opacity, light scattering, and human vision, were taken into account as potential influences on how people perceive the color of teeth in general.[23]

The experimental resin infiltrants showed better resistance against some of the staining solutions compared with the ICON resin material, hence proving partial acceptance of the hypothesis. Different treatment subgroups had varying ΔE values throughout time, according to this study. Thus, roughly all the null hypotheses were rejected. Coffee is said to have an acidic pH because it contains chlorogenic acid.[24] Additionally, it is frequently employed as a coloring agent to evaluate the color stability of materials in vitro. It is quite likely to discolor the tooth structure and dental restorative materials made of resin.[25] The stainability and color stability of polymer materials are influenced by water sorption and solubility, both of which are connected to the resin matrix's structure. The oxygen-induced polymerization inhibition and shrinkage caused by the presence of resin might result in nonhomogeneous areas, which can increase stain penetration and accumulation as well as adsorption.[26] However, the PR group resisted well against the coffee, as it sealed the demineralized surface well. The other experimental groups and the commercial group partially allowed the coffee to get into the tooth surface, and this could be due to the presence of the filler/additives in its composition, which allows the coffee to pass through microleakage/gaps in between the resin and the filler particles.[27] Another reason for having higher values for ICON is the presence of TEGDMA, which absorbs more water and hence creates more gaps due to hydrolysis. That welcomes the staining solutions to enter more rapidly.[27]

Meanwhile, they are known to be potent staining agents, and the beverages employed in this study are frequently consumed in our daily lives. According to a previous study, drinks with lower pH levels typically cause more significant stain penetration than those with higher pH levels.[28] These beverages' acidic qualities may affect the surface integrity of resin-infiltrated enamel,[29] resulting in microleakage at the interface and making the infiltrated surfaces more stainable.[30] The F-BAG appeared to show the most resistance against the soda solution. The reason could be the formation of a fluorapatite layer that resists against the medium. The experimental resins resisted against the different solutions maintaining their color properties. However, because of its hydrophilic nature, and having a higher TEGDMA percentage, ICON is susceptible to water sorption and matrix degradation.[31] [32]

The titratable acidity and citric acid in orange juice may intensify discoloration and increase the surface permeability of the superficial WSLs. Orange juice and other food solutions may hasten the breakdown of the resin-hydroxyapatite bonds on the surface, increasing the resin-infiltrated enamel's surface roughness and causing more light scattering and variations in the surface's apparent hue.[33] Some experimental groups exhibited enhanced discoloration due to their particle sizes, which enhanced the destruction of the resin: particle interface and discolored them more. This might result from the fillers' uneven distribution, which might permit greater exposure and the etching of their surface that follows. It is possible that the resins' microporosities helped to encourage pigment apposition further.

It was discovered that the artificial saliva's reliance on calcium ion deposition caused the remineralization of WSLs in both the commercial and experimental groups to proceed slowly.[34] The low-viscosity resin, on the other hand, might be able to reach deeper lesions and enhance WSL's aesthetics right away. Because of this, the ΔE for the ICON group exhibited a considerable rebound right away, while the ΔE decreased.[35] The results of previous studies confirm the findings of this study for artificial saliva, stating that resin infiltrants with refractive index (RI) that is near the enamel's RI can significantly alter the color and camouflage of WSLs.[36] [37] In the current investigation, the oral condition for releasing the bioactive material into the environment was simulated using artificial saliva. This situation facilitates the gradual replacement of calcium sodium phosphosilicate bioactive glass with hydrogen ions.[38] A thick layer of calcium and phosphate forms on the tooth surface as the process proceeds, raising the pH of the surrounding solution and stopping the demineralization process.[39]

The experimental resins proved better penetration resistance compared with the ICON resins, showing the rejection of the hypothesis. Experimental and commercial resin infiltrants both contain TEGDMA monomers. In comparison to other resin monomers, evidence suggests that TEGDMA is a hydrophilic monomer with strong water sorption. There is currently no established approach for evaluating microleakage by methylene blue penetration of resin infiltration and resin sealant in vitro, which makes it difficult to compare the results of various studies.[10] [40] [41] Dye concentrations of 0.5 to 10% were recorded by Alani and Toh, while the length of time the specimen was submerged in dye ranged from 4 to 72 hours or more.[42] The results of this study showed that samples of commercial and experimental resin infiltration had significantly different methylene blue penetration depths. Microleakage in composite resin is often caused by polymerization shrinkage of methacrylate resins.[43]

Within the constraints of the current study's in vitro setting, it is found that the resin-infiltrant color stability is significantly impacted by the coffee, soda, and solutions of citric acid. Whereas the materials could resist well against the artificial saliva solution. Patients with WSL in cosmetic areas treated with resin infiltration should be aware of the potential negative effects of citric acid and other acidic foods and beverages, such as lemons/oranges, soda drinks, and coffee.


 

Conclusion

The exposure of specimens to colored solutions resulted in significant color alteration. It can be said that solutions of coffee, soda, citric acid, and artificial saliva significantly harmed the color stability of resin-infiltrant material; yet, the acidic effect can be lessened by repolishing resin-infiltrated lesions. When compared with the other treatment groups, resin-infiltrated WSL treated to continuous pH cycling with citric acid demonstrated a statistically significant decrease in both brightness and overall color change over time.


 

 

Conflict of Interest

None declared.

Ethical Approval

Ethical approval was obtained from the Research Ethics Committee, Faculty of Dentistry, IAU, Dammam, Kingdom of Saudi Arabia (Approval no. EA-202144).


Data Availability Statement

All the data files are inserted in the manuscript.


Authors' Contributions

S.Z.A.: Conceptualization; supervision; project administration; validation; visualization; writing - review and editing; formal analysis; methodology; investigation; data curation; and roles/writing - original draft. S.A.: Formal analysis; methodology; and investigation. Y.H.A.: Formal analysis; methodology; investigation; and resources. S.H.A.: Methodology; investigation; and data curation.



Address for correspondence

Syed Zubairuddin Ahmed, PhD, MFDS RCPS (Glasg), PFUTL, MSc, BDS
Department of Restorative Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University
Dammam
Saudi Arabia   

Publication History

Article published online:
12 August 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/)

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Fig. 1 (A–C) Bifurcation of teeth samples for the group distribution of samples. (A) During the process of cutting the tooth, (B) the tooth has been cut into two halves, and (C) window preparation for the demineralization by covering the whole tooth with nail varnish. (D) Samples immersed in the demineralized solution to create the white spot lesion (WSL) on the teeth separately.
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Fig. 2 (A–D) Application armamentarium of the resin infiltrants. (A) Light curing machine, (B) experimental resin infiltration, (C) commercial resin infiltration, and (D) polishing/finishing discs. (E–H) Immersion of teeth samples in different mediums. (E) Containers with black coffee solution, (F) containers with soda and teeth immersed into it, (G) containers with citric acid solution with immersed teeth, and (H) containers having artificial saliva and teeth immersed into it.
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Fig. 3 (A–C) Process of spectrophotometry analysis. (A) Color-Eye 7000A spectrophotometry machine, (B) the application of tooth structure onto the lens to get the readings, and (C) prepared sample ready to be applied onto the machine with the black tape covering the surroundings to cover the lens. (D–F) shows the (D) stereomicroscope, (E) samples immersed in methylene blue dye, and (F) samples prepared for the microscopic analysis.
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Fig. 4 (A–E) Stereomicroscopic view of teeth samples after being immersed in the methylene blue solution to check the microleakage. (A) 45S5, (B) borosilicate-based bioactive glass (B-BAG), (C) fluoride-based bioactive glass (F-BAG), (D) ICON, and (E) Pure Resin. (F) Percentage of methylene blue penetration failure in percentage in all the resin groups.