Resin Infiltration for Esthetic Improvement of Mild to Moderate Non-pitted Fluorosis Stains in 6–12-year-old Children: A Randomized 6-month Interventional Study

INTRODUCTION

Fluoride has a vital role in the prevention of dental caries. However, if the total systemically ingested fluoride levels go beyond the optimal limits, dental fluorosis results.¹

The treatment choices available for esthetic improvement (EI) of fluorosis teeth include non-invasive and invasive methods. Non-invasive modalities include removing the stained tooth surface by way of dental bleaching, microabrasion; while invasive options include restoring the discolored teeth with veneers, laminates or crowns. However, the extensiveness of the treatment procedures, reduction of tooth structure for esthetic correction and associated tooth sensitivity are the drawbacks associated with the conventional approaches. Nowadays, newer non-invasive treatment approaches have been advocated by various authors, especially resin infiltration (RI) for masking of mild to moderate fluorosis stains as conservatively as possible.²

Recently, RI technique, originally recommended for arresting initial caries and for EI of white spot lesions, has also been reported to manage fluorosis stains. It is a micro-invasive treatment of incipient caries confined to enamel without loss of healthy tooth structure. The principle of RI is to fill the incipient enamel pores with resin by capillary action which blocks further diffusion pathways for the bacteria by creating barriers and stops the lesion progression. Resin infiltration, with its near similar refractive index (RI = 1.46) to that of healthy enamel (RI = 1.62) creates a chameleon effect—a blend shading of the teeth lesions with the tooth surface.^3,4

The present study was done to evaluate the EI of RI over mild to moderate non-pitted fluorosis stains in 6- to 12-year-old children on visual analog scale (VAS).

ETHICAL COMMITTEE APPROVAL

Approval was obtained from the Institutional Ethics Committee before the beginning of the study (Certificate number: PGIDS/IEC/2018/23) and it was conducted in agreement with the principles postulated in the Declaration of Helsinki.

MATERIALS AND METHODS

The present study was conducted for a period of 1 year from March 2019 to March 2020. The study participants aged 6–12 years with unesthetic appearance (white or brown discoloration, stains, and/or opacities) of upper anterior teeth due to non-pitted fluorosis stains were randomly selected by independent personnel in the first 6 months of the time period. The inclusion criteria consisted of healthy cooperative children aged between 6 years and 12 years presenting with non-pitted fluorosis seeking dental treatment and whose parents gave informed written consent for participation. Children with non-fluoride opacities and pitted fluorosis, history of known allergy toward any dental material, systemic illness (mental retardation/severe psychotic disorders), severe sensory and/or motor impairment and those unwilling for participation were excluded from the study.

The “fluoride” and “non-fluoridated” enamel opacities were differentiated following Russell’s criteria⁵ according to which all bilaterally symmetrical and diffuse opaque areas of enamel are fluorosis. The baseline standardization of dental fluorosis condition was done as per Dean’s Fluorosis Index (DFI)–Modified Criteria (1942)⁶ according to which participants were classified for severity of fluorosis. The participants with DFI score of 0.5, 1, 2, 3 (non-pitted fluorosis) were taken in the study. Since fluorosis usually affects more than one tooth in the dentition, in such cases the most severely affected anterior tooth with maximum DFI score was incorporated in the study.

RESULTS

The results showed that a highly significant difference (p < 0.01) was seen statistically for values of EI (p = 0.001) and changes in white/brownish opacities/stains (SC) (p = 0.001) between the follow-up time intervals with higher mean VAS score values at time interval 6 months followed by 3 months, 1 month, and least at immediate postoperative (Table 2).

Pairwise comparison for EI at follow-up intervals revealed highly significant difference statistically (p < 0.01) for values of EI after RI procedure between immediate vs 3 months postoperative (p = 0.001), immediate vs 6 months postoperative (p = 0.001), and 1 month vs 6 months postoperative (p = 0.002) (Table 3).

Similarly, pairwise comparison for SC showed a highly significant difference (p < 0.01) between immediate vs 3 months postoperative (p = 0.01) and immediate vs 6 months postoperative (p = 0.003) (Table 3).

Inter-grade comparison of fluorosis showed that there was a highly significant difference statistically (p < 0.01) for VAS score values after RI with higher mean VAS score values in a mild degree of fluorosis for both EI and SC (Table 4).

DISCUSSION

The RI technology was first introduced at the Charite Berlin and the University of Kiel as a micro-invasive method to inhibit demineralization in incipient proximal caries and mask white spot lesions on intact smooth surfaces. It is commercially available under the trade name Icon (introduced by company DMG, Germany). Resin infiltration works on the principle of perfusing the enamel pores with resin by capillary forces rendering the white spots negligible because the refractive index of porous enamel becomes nearly similar to that of healthy enamel (1.52). Recently, RI has also been described in the esthetic management of fluorosis stains. The rationale for using resin infiltrant in fluorosis spots is that these lesions imitate white spot demineralization since they already have hypomineralized enamel subsurface under a relatively well-mineralized area that can be easily penetrated by the resin.^3,4

Subjective parameters for evaluation in our study were scoring for “esthetic improvement (EI)” and “changes in white/brown opacities/stains (SC)” on a VAS ranging from 1 (No improvement) to 7 (Exceptional improvement). VAS was adopted from similar studies done by Loguercio et al.⁷ and Price et al.⁸ and can truly measure the overall improvement in the appearance of the mottled tooth surface as stated by Celik et al.⁹

The results showed a highly significant difference statistically (p < 0.01) for mean VAS score values of EI and SC between the follow-up time intervals with highest values at time interval 6 months followed by 3 months, 1 month, and least at immediate postoperative. Our findings were in accordance with Auschill et al.,⁴ Cocco et al.,¹⁰ Owda and Sancakli,¹¹ and Garg and Chavda¹² who have reported long-term positive outcomes of RI. Improvement in esthetics by RI could be attributed to blending of enamel lesions with the surrounding sound enamel, based on changes in the refractive index.¹³

The infiltrant resin product used in the present study was based on triethylene glycol dimethacrylate (TEGDMA), a monomer with hydrophilic features, low viscosity, and a high penetration coefficient, which promotes rapid penetration of the resin into the enamel pores.¹⁴ Tooth surface mineralization is a prerequisite for the resin to penetrate the enamel, therefore etching was done via the application of 15% hydrochloric acid. Ethanol at 99% concentration was used to eliminate water from the pores, facilitating the penetration of resin.¹⁴ Two-time application of resin is recommended because in the first application the monomers convert to polymers causing contraction of the material and generation of spaces. These spaces must get filled with the second application of resin.¹⁵ In our study, EI was noted over the follow-up time span with best clinical results seen at 6 months time frame, possibly due to the absorption of water by resin over time, which was not completely removed by ethanol. As a result of this absorption, the optical interfaces in the light path are reduced, as mentioned by Attal et al.¹⁶ and Cocco et al.¹⁰ in their case reports. The polymerization of the last layer of resin is generally incomplete due to oxygen inhibition in the superficial layer.¹⁷ Hence, polishing of the enamel surface was done in the final step to removing the excess resin. Moreover, polishing helped to prevent future staining.

Furthermore, inter-grade comparison of fluorosis showed a highly significant difference (p < 0.01) for the VAS scores for both the parameters (EI and SC) with higher mean VAS score values in a mild degree of fluorosis followed by moderate degree. This difference could be attributed to the volume and depth of the subsurface pores that increase as the severity of dental fluorosis increases.¹⁸ Mild cases are characterized by white lines, following the perikymata of enamel, whereas in moderate cases the whole enamel surface may be white and opaque.¹⁸ The less the degree of fluorosis, the less porous is the enamel surface and better is the penetration of resin.

Resin infiltration is a micro-invasive treatment approach with several advantages. It erodes only 30–40 μm of enamel surface as part of etching procedure which thereby gets infiltrated with resin.¹⁹ This is in contrast with the treatment of microabrasion, composite fillings, veneers or crowns, which require a greater portion of the tooth structure to be removed. Second, the technique is a relatively quick and pain-free procedure to perform compared to other restorative options that may require local anesthetic and healing process. Third, it is a less expensive procedure than more invasive, tooth-destructive treatments.⁴ Furthermore, no need of special maintenance precautions and favorable esthetic results along with increased patient acceptance and compliance are other major advantages of RI technique.

LIMITATION

The follow-up time span of the study was 6 months. Longer durations of follow-up are necessary to evaluate the sustainability of the results based upon which the time of re-application can be established.

CONCLUSION

Resin infiltration showed significant improvement in esthetics and changes in opacities/stains on non-pitted fluorosis stains in 6–12-year-old children. Moreover, greater EI was observed in subjects with a mild degree of fluorosis over follow-up time intervals.

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