Colour Stability of Tooth-Coloured Restorative Materials Following Exposure to Paediatric Oral Iron Supplementation: An In-Vitro Study

ABSTRACT

Objective:  To assess the color stability of resin-modified glass ionomer cement and composite-based restorative materials exposed to Ayurvedic-based iron supplements for pediatric patients.

Material and Methods:  Twenty disk-shaped samples were fabricated from composite and resin-modified glass ionomer cement (RMGIC). The baseline color values of both materials were measured via the CIE l*a*b* system. The samples were divided into groups A (RMGIC) and B (composites), which were exposed to 2 iron supplements, Tonoferon and Lohasava (n=40), over a 40-day test period. The colors of all the samples were measured again. The data were analyzed using one-way ANOVA with Tukey's post hoc test and an independent sample t-test (p<0.05).

Results:  Dental restorative materials based on composites and RMGIC are susceptible to color changes when exposed to pediatric iron supplements. A significant color change was observed in RMGIC discs immersed in Lohasava, followed by composite discs immersed in Lohasava when subjected to immersion in composite discs immersed in standard pediatric iron syrup (Tonoferon).

Conclusion:  Compared with conventional iron supplements, Ayurvedic iron supplements cause more discolouration in composites and resin-modified glass ionomer cement.

Keywords:
Tooth Discoloration; Iron; Dietary; Anemia; Dental Restoration Failure.

ν Introduction

Smile aesthetics influence social perception during childhood and adolescence [¹], with tooth discoloration leading to social judgment among schoolchildren and their peers. The increasing demand for aesthetic dental care in children has led to the development of dental materials that simulate the natural tooth structure. Composite resins, polyacid-modified compounds, and glass ionomer cements (GICs) are generally used in pediatric patients to obtain optimum aesthetic results [²-⁴].

The prevalence of iron deficiency anaemia has been reported in more than 70% of Indian and Asian populations [⁵]. Iron supplements are administered to anemic children as young as 6 months of age [⁴]. Oral iron supplementation is the most commonly prescribed treatment and is available in modern and traditional medicinal systems [⁶]. Iron in ayurvedic syrups is composed of calcined iron oxide, termed lohabhasma, whereas modern iron medications contain elemental iron in colloidal form [⁷].

One of the major reported drawbacks of iron-supplemented syrups is the black discoloration of the teeth [⁸]. Several studies have reported tooth discoloration among young people who consume iron syrups, drops, and other preparations [¹]. In addition, the staining potential of these iron supplements on dental restorative materials is well documented in the literature [⁹]. The discoloration of restorative materials can occur due to various intrinsic, extrinsic, and age-related factors that affect their optical properties over time. One of the primary causes is polymer degradation, particularly in composite resins, which can lead to color instability. Chemical reactions, such as the oxidation of amine accelerators in self-cured and dual-cured composites, contribute to yellowing.

In contrast, UV light exposure causes photodegradation of resin components, particularly photoinitiators, further affecting their color stability [¹,²,⁹]. Compositional differences exist between modern and traditional iron syrups. Modern iron syrups contain a colloidal form of iron, whereas traditional iron supplements contain a calcined form of iron. While the staining potential of modern iron supplements has been documented in the literature [⁹-¹¹], no investigations have been conducted to assess the effects of ayurvedic iron supplements on restorative materials.

In view of the above, the present study aimed to investigate the staining potential of standard and aqueous oral iron supplementation on tooth-colored restorative materials. The null hypothesis of the present study is that there will be no difference in the staining potential of standard and aqueous oral iron supplements.

ν Material and Methods

Two commercially available dental restorative materials widely used for pediatric patients were selected. Similarly, two different commercially available iron supplement syrups were selected, as shown in Table 1. A2 shades of packable composite resin (3 M Filtek Z350 XT universal enamel, 3M ESPE, St. Paul, MN, USA) and resin-modified glass ionomer cement (GC Gold Label 2 LC, GC Corp., Tokyo, Japan) were used in the study. Resin-modified glass ionomer cement, supplied as a powder and liquid, was mixed at a powder:liquid ratio of 3.2:1 by weight, whereas the composite material was supplied by the manufacturer.

Table 1
Description of the materials used.

Product	Manufacturer	Lot Number
GG Gold 2 LC (A2 Shade)	GC Corp., Tokyo, Japan	2210121
3 M Espe Filtek Z350 Xt (A2 Shade)	3M Espe Dental Products, St. Paul, MN, USA	Ne89544
Tonoferon	East India Pharmaceutical Works Ltd, Kolkata, India	Not available
Lohasava	Baidyanath Ayurvedic Bhawan Ltd, Kolkata, India	Not available

Table 2
Comparison of the mean ∆E between baseline and 40 days among various test solutions and restorative materials.

Materials	Baseline		40 Days		p-value
	Mean	SD	Mean	SD
RMGIC
Pediatric Iron Syrup	27.37	1.57	56.30	2.34	<0.001*
Lohasava	26.57	2.65	58.98	2.23	<0.001*
Composite
Pediatric Iron Syrup	27.37	1.57	53.60	2.49	<0.001*
Lohasava	26.57	2.65	57.11	3.09	<0.001*

• ^*
  Statistically significant.

Sample size was calculated based on the formula: $n=\frac{2\times {(Z_{\alpha /2}+Z_{\beta })}^2\times {\sigma }^2}{{\mathrm{\Delta }}^2}$

Where: • Zα/2 = Z value for desired significance level (e.g., 1.96 for α = 0.05); • Zβ = Z value for desired power (e.g., 0.84 for 80% power); • σ = estimated standard deviation of ∆E values = 2.5; • ∆ = minimum detectable difference in ∆E values (effect size) = 2.5 based on previous studies. Based on this, the sample size was 10 specimens per group, for a total of 40 specimens.

Specimen Preparation

Forty discs of 8 mm in diameter and 2 mm in thickness were fabricated via a custom-made putty mold with punched holes of the desired dimensions. The restorative materials were dispensed and light-cured. Prior to light curing, a mylar strip was placed on the top and bottom surfaces of the glass slab to ensure a smooth surface of each material. The top and bottom surfaces of each sample were light-cured for 40 seconds (20 seconds on each side) via a calibrated Monitex Blue LEX LED (light-emitting diodes) unit (intensity: 1000 mW/cm²; output: 9 V, 1.3 A, 5 W; wavelength: 420-490 nm). The tip of the light guide was in contact with the glass slab from both the top and the bottom surfaces during the light polymerization process [¹²]. A 1 kg weight was placed onto the glass slab to ensure the removal of excess material. After the samples were removed from the molds, they were stored in distilled water for 24 hrs at 37 degrees Celsius for the completion of polymerization. The edges of all the samples were polished with 80, 1000, and 1500 silicon carbide papers. TruStar silicon carbide sandpaper was used in the study (23cm x 28cm) to minimize surface irregularities that could influence staining. These combined procedures guaranteed a highly controlled, standardized, and calibrated assessment of stain potential across all groups.

Next, the samples of each restorative material were randomly divided and immersed in two different solutions. To suspend the sample in the immersion solution, a wax floss 5 cm in length was attached to the edge of the sample during its preparation.

The samples were divided into the following groups:

• Group 1: RMGIC Fuji II Light-Cured immersed in standard pediatric iron syrup solution;

• Group 2: RMGIC Fuji II Light-Cured immersed in Lohasava solution;

• Group 3: Composite immersed in standard pediatric iron syrup solution;

• Group 4: Composites immersed in Lohasava solution.

Staining Regimen

Each group was exposed to the following iron supplements:

• Standard pediatric iron syrup - Tonoferon Pediatric Syrup 100 ml (combination of colloidal iron, folic acid, and vitamin B12). Each 5 mL sample contained colloidal iron, equivalent to 80 mg of elemental iron.

• Ayurvedic Iron Syrup - Lohasava, which holds ShodhitaLoha (purified herbal processed Iron= 192 gm), along with other herbs. To ensure uniform exposure of the samples in both groups, 1 mL of Tonoferon contained 50 mg of colloidal iron, and 77 mL of Lohasava contained 50 mg of calcined iron.

The samples were immersed in standard and aqueous iron syrups. One milliliter of standard pediatric iron syrup was dispensed into a plastic container using a plastic dropper. Similarly, 77 mL of Lohasava was stored in a plastic bottle with a plastic dropper and a cylindrical beaker. Consequently, 20 containers contained 1 mL of Tonoferon, and 20 containers contained 77 mL of Lohasava. The samples were suspended in nylon thread or dental floss at the edge and fully immersed in the syrups.

Color Measurement

The samples were placed on white chart paper and labeled individually. The samples were mounted on a calibrated spectrophotometer (i1Pro 3 Spectrometer, X-Rite Inc., Grand Rapids, MI, USA), and color was measured via a CIE lab system. Once the sample was mounted, its color (L*, a*, b*) was measured under D65 light against a white background to maintain uniformity. The overall color of the samples was calculated by keeping the stain assessment standardized and calibrated to ensure accurate results. The color difference between the samples was reported as ∆E.

To simulate clinical conditions, the samples were incubated in an incubator at 37°C to simulate normal oral temperature. The immersion time was three hours per day at 37°C for a 40-day test period. The samples were placed in distilled water to remove excess solution, then placed in plastic sealed bags. All the containers and sealed bags were properly labeled to avoid any errors. The suspension medium was changed daily for 40 days. Following immersion, the samples were rinsed with distilled water and then air-dried.

Post-Staining color Testing

The samples were again placed on a white background and segregated into their respective groups. Consequently, the L*, a*, and b* values were again measured using the CIE lab system. The ∆E values were also calculated, and the samples were stored in a spreadsheet.

Statistical Analysis

The data were analyzed for normality via the Shapiro-Wilk test. The mean difference in ∆E among the four groups was compared via one-way ANOVA with Tukey’s post hoc test. The mean difference in ∆E (baseline - 40 days) among the four groups was compared via one-way ANOVA with Tukey’s post hoc test. The mean difference in ∆E between the two restorative materials was determined via an independent sample t-test. For all statistical tests, p<0.05 was considered statistically significant, with α=5 % and β=20 %, providing 80% power to the study.

ν Results

Figure 1 gives the mean ∆E values at baseline and 40 days in various test solutions and restorative materials. The mean ∆E at 40 days was significantly (p < 0.000) greater than the mean ∆E at baseline in all four groups (Table 2).

Figure 1
Mean ∆E values at baseline and 40 days in various test solutions and restorative materials.

The mean difference (∆E) from baseline to 40 days was greatest for RMGIC discs immersed in Lohasava (32.413), followed by composite discs immersed in Lohasava (29.691) and RMGIC discs immersed in standard pediatric iron syrup (28.927), with the lowest value for composite discs immersed in standard pediatric iron syrup (26.615) (Table 3). One-way ANOVA revealed significant differences in the mean difference in ∆E among the four groups (Table 3). Tukey’s post hoc analysis revealed a significant difference only between RMGIC discs immersed in Lohasava and composite discs immersed in standard pediatric iron syrup (p = 0.018).

Table 3
Mean difference between baseline and 40 days for Diffr E (∆E) values among various test solutions and restorative materials.

Materiais	Mean Difference E (∆E)	95% CI for Mean		Std. Error	p-value (F-value)	Post-hoc test
		Lower Bound	Upper Bound
RMGIC
Pediatric Iron Syrup (G1)	28.927	26.570	31.285	1.042	0.031* (3.301)	G 2 > G3
Lohasva (G2)	32.413	29.637	35.189	1.227
Composite
Pediatric Iron Syrup (G3)	26.615	23.937	29.295	1.184
Lohasva (G4)	29.691	25.820	33.562	1.711

• ^*
  ANOVA with Tukey’s post hoc test; p-value significant at p<0.05.

ν Discussion

Iron supplementation in the form of syrups is commonly prescribed to growing individuals who are anemic. Studies have documented their potential to stain enamel [¹,¹²-¹⁴], as well as tooth-colored restorative materials [⁹-¹¹]. While the staining potential of modern supplements has been documented in the literature [¹,⁹-¹¹], no studies have assessed the effects of traditional iron supplements on restorative materials. Iron present in modern iron supplements, such as Tonoferon, is elemental iron, whereas iron in traditional iron supplements, such as Lohasava, is iron bhasma, which is the calcined form of iron or iron oxide. These products are prepared from purified iron filings/ferric oxide or magnetic iron incinerated with a decoction of Triphala, Aloe barbadensis, vinegar, and sesame oil [⁶]. A difference in the staining potential of the two iron syrups may be anticipated owing to differences in their formulations. The most used aesthetic restorative materials in pediatric dentistry, including resin-modified glass ionomer cement and composites, were included in our study.

Therefore, this in vitro study aimed to assess and compare the color stability of a resin-modified glass ionomer cement (RMGIC) and composite following exposure to modern (TonoFeron) and traditional (Lohasava) iron supplements. The changes in hue, value and chroma of restorative materials following exposure to iron supplements were also quantified.

After a 40-day test period, the results showed that RMGIC exhibited the highest staining, whereas the composite was relatively more resistant. Various existing studies have shown both similar and contrasting results, depending on factors such as the type of restorative material, iron supplementation, and the methodology used.

Kathiria et al. [⁹] evaluated the effects of commonly prescribed pediatric medications, including amoxicillin, cephalexin, iron supplements, ibuprofen and paracetamol, on the color stability of various aesthetic restorations, such as glass ionomer cements and composites. They reported that iron supplements caused the greatest discoloration in the composites. The reason was the composite's high water absorption, which led to gaps at the matrix‒filler interface, allowing more iron supplements to penetrate and stain [⁹]. In our study, resin-modified glass ionomer cement, which has a higher water absorption capacity than the other composites, was used. Therefore, compared with RMGIC, the composite was more resistant to staining.

A study by Yildırım et al. [⁸] concluded that the content of iron syrup was also a crucial factor in the color change. In their study, compomers, hybrid microcomposites and nanohybrid composites were evaluated. The result was that the nanohybrid composite appeared more resistant to staining with iron syrups due to its smaller filler particle size and its ability to fill surface defects and fissures via capillary action [⁸]. This can be related to our present study, as the filler particle size of the packable composite used was smaller than that of the resin-modified glass ionomer cement. In another study, the effects of tooth brushing and various pediatric drugs, including iron formulas, antibiotics, analgesics, common cold syrup, cough syrup, and vitamin formulas, on color changes in restorative materials used in pediatric dentistry were investigated. The restorative materials used were compomers [Dyract XP], glass hybrids [Equia Forte], and glass carbomers [GCP Glass Fill]. After 14 days of testing, the greatest color difference was observed for the sample that was not brushed and was immersed in the iron formula. The compomer showed greater staining potential than the glass hybrid samples did [¹⁵]. In our study, tooth brushing was not considered; thus, we observed greater staining potential in the composite and resin-modified glass ionomer samples, whereas the resin-modified glass ionomer cement showed the greatest staining potential..

Similarly, Pani et al. [¹], Lokhande et al. [¹⁶], and Almutairi et al. [¹⁷] investigated the staining effect of various formulations of iron, including ferric and ferrous iron, and a combination of these syrups on primary teeth. They concluded that both iron syrup groups showed significantly greater clinically visible staining than the combination solution group at 72 h [¹,¹⁶,¹⁷]. Our study used the ferric oxide form of iron, which has stronger chemical interactions than ferrous formulations, so the discolouration observed was also greater. Patel et al. [¹⁸] and others reported that the degree of color change was related to the type of staining solution used and did not depend on the type of composite resin. The surface roughness, amount and size of filler particles, and the physical, chemical, and mechanical characteristics of the resin matrix, such as water sorption, hydrophilicity, and degree of conversion, are factors that affect composite resin stainability [¹⁶-²¹]. Babaei et al. [²¹] analyzed the effects of five types of iron drops with varying pH and viscosity on the color of deciduous teeth. All the iron drops displayed discolouration that was easily distinguished to the naked eye, and low pH increased the risk of tooth erosion [²¹]. The following literature suggests that iron supplements can result in positive staining of both teeth and restorative materials. Various factors, such as smaller filler particle size and lower water absorption than RMGIC, were observed in the composites due to the higher staining resistance of the iron formulations.

In our study, spectrophotometry is used to assess staining potential. Spectrophotometry is considered the gold standard due to its precision and reproducibility using CIELAB. Colorimeters provide similar data but are slightly less accurate. Digital image analysis offers a semi-objective, cost-effective method using software, though it is highly dependent on lighting and calibration [²²,²³].

Mahajan et al. [²⁴] evaluated the solubility of nanohybrid composites in saliva substitute and distilled water. The study showed that solubility characteristics are similar in both artificial saliva and distilled water. There was no statistically significant difference in solubility, so we used distilled water instead of artificial saliva, as our study was conducted under wet conditions. Pani et al. [¹] conducted an in vitro study to evaluate the extrinsic staining potential of high-dose oral iron formulations on primary teeth. To accurately simulate the exposure of teeth to iron syrups in the oral cavity, the researchers immersed extracted primary teeth in liquid iron supplements. This wet condition was essential to mimic the clinical scenario in which children's teeth are frequently in contact with iron-rich syrups in the presence of saliva. By using liquid immersion, the study effectively replicated the real-life dynamics of iron-induced staining [¹,²⁴].

All the following studies reported positive staining potential of iron supplements on teeth and tooth-colored restorative materials, but none have discussed the staining potential of an aqueous iron supplement. To address this research gap, in our current study, we evaluated the effects of traditional iron syrup (i.e., Lohasava), on RMGIC and composites by comparing them with those of modern iron syrup. The results showed that traditional iron syrup (Lohasava) had much greater staining potential than modern commercial iron syrup. Among the two types of tooth-colored restorative materials, resin-modified glass ionomer cement resulted in more intense staining than the other composite materials.

The following limitations of this study should be considered when interpreting the results. This in vitro study does not accurately simulate the oral environment, where factors such as dietary coloring agents, oral hygiene, and salivary proteins, enzymes, and pH may further influence the staining potential of the solutions. The results of this study are based solely on one type of traditional iron syrup, i.e., Lohasava, and its effect on RMGIC and composite restorative materials; therefore, the results may differ when other types of traditional iron supplements or restorative materials are used.

This study will help promote patient awareness and pave the way for future research to formulate dental materials that are more resistant to discoloration. A better understanding of the staining potential of available iron supplements, as well as oral intrinsic and extrinsic factors, may contribute to the development of dental materials that offer greater resistance to discoloration. Further studies are needed to investigate the effects of different types of sealant agents on restorative materials to prevent staining caused by iron syrups. Additionally, tooth brushing should be considered.

ν Conclusion

The greatest color difference was observed in the resin-modified glass ionomer cement immersed in the traditional iron supplement Lohasava. Compared with resin-modified glass ionomer cement, the iron syrup formulations appeared to be more resistant to staining. Compared with the modern iron supplement, traditional iron syrup has greater staining potential.

• 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.

ν References

• ^[1] Pani SC, Alenazi FM, Alotain AM, Alanazi HD, Alasmari AS. Extrinsic tooth staining potential of high dose and sustained release iron syrups on primary teeth. BMC Oral Health 2015; 15(1):90. https://doi.org/10.1186/s12903-015-0072-0
  » https://doi.org/10.1186/s12903-015-0072-0
• ^[2] Iazzetti G, Burgess JO, Gardiner D, Ripps A. Color stability of fluoride-containing restorative materials. Oper Dent 2000; 25(6):520-525.
• ^[3] García-Godoy F. Resin-based composites and compomers in primary molars. Dent Clin North Am 2000; 44(3):541-570.
• ^[4] Gupta SK, Bansal D, Malhi P, Das R. Developmental profile in children with iron deficiency anemia and its changes after therapeutic iron supplementation. Indian J Pediatr 2010; 77(4):375-379. https://doi.org/10.1007/s12098-010-0046-9
  » https://doi.org/10.1007/s12098-010-0046-9
• ^[5] Kotecha P. Nutritional anemia in young children with focus on Asia and India. Indian J Community Med 2011; 36(1):8-16. https://doi.org/10.4103/0970-0218.80786
  » https://doi.org/10.4103/0970-0218.80786
• ^[6] Kumar A, Nair AGC, Reddy AVR, Garg AN. Bhasmas: Unique ayurvedic metallic-herbal preparations, chemical characterization. Biol Trace Elem Res 2006; 109(3):231-254. https://doi.org/10.1385/bter:109:3:231
  » https://doi.org/10.1385/bter:109:3:231
• ^[7] Singh K, Sethi Chopra D, Singh D, Singh N. Nanoformulations in treatment of iron deficiency anemia: An overview. Clin Nutr ESPEN 2022; 52:12-19. https://doi.org/10.1016/j.clnesp.2022.08.032
  » https://doi.org/10.1016/j.clnesp.2022.08.032
• ^[8] Yıldırım S, Kaya E. Can the use of surface sealant on restorative materials prevent discoloration related to iron syrup supplements? Eur Arch Paediatr Dent 2021; 22(4):739-750. https://doi.org/10.1007/s40368-021-00614-5
  » https://doi.org/10.1007/s40368-021-00614-5
• ^[9] Kathiria H, Panda A, Virda M, Budakoti V, Dave P, Malge R. Effect of pediatric drugs on color stability of various esthetic restorations in pediatric dentistry. Int J Prev Clin Dent Res 2021; 8(2):35-37. https://doi.org/10.4103/ijpcdr.ijpcdr_11_21
  » https://doi.org/10.4103/ijpcdr.ijpcdr_11_21
• ^[10] Curtin JA, Lu H, Milledge JT, Hong L, Peterson J. In vitro staining of resin composites by liquids ingested by children. Pediatr Dent 2008; 30(4):317-322.
• ^[11] Malek Afzali B, Ghasemi A, Mirani A, Abdolazimi Z, Akbarzade Baghban A, Kharazifard MJ. Effect of ingested liquids on color change of composite resins. J Dent Tehran Iran 2015; 12(8):577-584.
• ^[12] Chami VO, Gebert F, Assaf DDC, Centeno ACT, Ferrazzo VA, Durand LB, et al. Color stability of resin composites for orthodontic attachments: An in vitro study. Dental Press J Orthod 2022; 27(1):e2220432. https://doi.org/10.1590/2177-6709.27.1.e2220432.oar
  » https://doi.org/10.1590/2177-6709.27.1.e2220432.oar
• ^[13] Janjua U, Bahia G, Barry S. Black staining: An overview for the general dental practitioner. Br Dent J 2022; 232(12):857-860. https://doi.org/10.1038/s41415-022-4345-0
  » https://doi.org/10.1038/s41415-022-4345-0
• ^[14] Kumar A, Kumar V, Singh J, Hooda A, Dutta S. Drug-induced discoloration of teeth: An updated review. Clin Pediatr 2012; 51(2):181-185. https://doi.org/10.1177/0009922811421000
  » https://doi.org/10.1177/0009922811421000
• ^[15] Lu H, Roeder LB, Lei L, Powers JM. Effect of surface roughness on stain resistance of dental resin composites. J Esthet Restor Dent 2005; 17(2):102-108. https://doi.org/10.1111/j.1708-8240.2005.tb00094.x
  » https://doi.org/10.1111/j.1708-8240.2005.tb00094.x
• ^[16] Lokhande RS, Nagarathna PJ, Deoghare A, Chhatani N, Busi S, Malladi S. Effect of different iron supplements on color stability of nanocomposite restorative materials. Int J Clin Pediatr Dent 2024; 17(3):274-278. https://doi.org/10.5005/jp-journals-10005-2790
  » https://doi.org/10.5005/jp-journals-10005-2790
• ^[17] Almutairi M, Moussa I, Alsaeri N, Alqahtani A, Alsulaiman S, Alhajri M. The effects of different pediatric drugs and brushing on the color stability of esthetic restorative materials used in pediatric dentistry. Children 2022; 9(7):1026. https://doi.org/10.3390/children9071026
  » https://doi.org/10.3390/children9071026
• ^[18] Patel SB, Gordan VV, Barrett AA, Shen C. The effect of surface finishing and storage solutions on the color stability of resin-based composites. J Am Dent Assoc 2004; 135(5):587-594. https://doi.org/10.14219/jada.archive.2004.0246
  » https://doi.org/10.14219/jada.archive.2004.0246
• ^[19] Doğu Kaya B, Yılmaz Atalı P, Özmen S, Öztürk S, Tarçın B. Effect of an effervescent multivitamin on color and surface roughness of micro‑hybrid dental resin composites. Materials 2024; 17(5):1040. https://doi.org/10.3390/ma17051040
  » https://doi.org/10.3390/ma17051040
• ^[20] Arregui M, Contreras Arellano JP, Veloso Durán A, Guinot Jimeno F. Effect of multivitamins on the color stability of dental materials used in pediatric dentistry: An in-vitro study. Polymers 2024; 16(20):2948. https://doi.org/10.3390/polym16202948
  » https://doi.org/10.3390/polym16202948
• ^[21] Babaei N, Molaei T, Belyad S, Hekmatfar S. Relationship of pH and the viscosity of five different iron supplements with the absorption of iron ions and enamel discoloration in the anterior primary teeth (an in vitro study). Dent Res J 2021; 18:7.
• ^[22] Alqahtani F. Methods and parameters of tooth color measurement: A review. J Prosthodont 2020; 29(6):494-500.
• ^[23] Paul S, Peter A, Pietrobon N, Hämmerle CHF. Visual and spectrophotometric shade analysis of human teeth. J Dent Res 2002; 81(8):578-582. https://doi.org/10.1177/154405910208100815
  » https://doi.org/10.1177/154405910208100815
• ^[24] Mahajan RP, Shenoy VU, MV S, Walzade PS. Comparative evaluation of solubilities of two nanohybrid composite resins in saliva substitute and distilled water: An in vitro study. J Contemp Dent 2017; 7(2):82-85. https://doi.org/10.5005/jp-journals-10031-1190
  » https://doi.org/10.5005/jp-journals-10031-1190

Edited by

• Academic Editor:
  Catarina Ribeiro Barros de Alencar

Publication Dates

• Publication in this collection
  23 Mar 2026
• Date of issue
  2026

History

• Received
  06 June 2025
• Reviewed
  14 July 2025
• Accepted
  12 Aug 2025