Soveral M, Machado V, Botelho J Effect of resin infiltration on enamel: a systematic review and meta-analysis. J Funct Biomater. 2021; 12 https://doi.org/10.3390/jfb1203004
Kim S, Kim EY, Jeong TS, Kim JW The evaluation of resin infiltration for masking labial enamel white spot lesions. Int J Paediatr Dent. 2011; 21:241-248 https://doi.org/10.1111/j.1365-263X.2011.01126.x
Kidd EA, Fejerskov O What constitutes dental caries? Histopathology of carious enamel and dentin related to the action of cariogenic biofilms. J Dent Res. 2004; 83:C35-38 https://doi.org/10.1177/154405910408301s07
Paris S, Meyer-Lueckel H, Cölfen H, Kielbassa AM Penetration coefficients of commercially available and experimental composites intended to infiltrate enamel carious lesions. Dent Mater. 2007; 23:742-748 https://doi.org/10.1016/j.dental.2006.06.029
Paris S, Meyer-Lueckel H Masking of labial enamel white spot lesions by resin infiltration – a clinical report. Quintessence Int. 2009; 40:713-718
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Resin infiltration is a minimally invasive technique to treat mild hypomineralized lesions. It seals the porosity of the affected enamel, strengthens the enamel defect and improves the aesthetics of the lesion. However, there are disadvantages such as lack of evidence on its long-term durability and microleakage. This article provides an overview on the resin infiltration concept and the procedure for its application.
CPD/Clinical Relevance:
Resin infiltration is a minimally invasive procedure that occludes the pores and inhibits further demineralization. within the lesion body.
Article
Enamel porosity could be due to an enamel defect or an early stage of enamel caries. Regardless of the aetiology, the porosity of the enamel structure leads to an optical phenomenon dependent on the pore volume of the body of the defect. During demineralization of the enamel or an interruption to the mineralization of the enamel by an insult, the pore volume of the affected enamel increases, thus changing the refractive index (RI) of the lesion. The difference in the refractive indices between sound enamel and the lesion affects light scattering, making the lesion visually distinguishable. Such lesions have a range of discolouration, including white, white-creamy, creamy-yellow or yellow-brownish colours.1
For clinical examination of the lesion, it is essential to dry the tooth because the difference in the refractive indices (RI) between sound enamel (1.63) and air (1.0) is greater than that between enamel and water (1.33). If the lesion is only visible on a dry tooth surface, the depth is probably in the outer enamel, whereas a visible lesion on a wet tooth surface will indicate that the lesion has progressed more into the enamel and possibly, into dentine.2,3
Resin infiltration, a minimally invasive technique, occludes the pores within the lesion body and efficiently inhibits further demineralization of existing lesions. It helps to strengthen the enamel mechanically and prevents the breakdown of the enamel surface (Figure 1).4 Furthermore, the resin-infiltrated lesion will appear to be similar to the surrounding sound enamel because of there is only a small difference in the refractive indices between the sound enamel (RI = 1.63) and the infiltrant (RI = 1.46). Therefore, the resin infiltrant can improve the appearance of the lesion. One clinical study showed successful masking of post-orthodontic lesions (61% completely and 33% partly masked lesions) with the infiltration treatment.2
Figure 1.
(a) white spot lesion on the surface of the tooth showing the enamel porosity. (b) Occluded white spot lesion after using infiltrant resins. Courtesy of The Dental Box, Tunbridge Wells.
This technique has the advantages of being non-invasive, the tooth structure is preserved and the procedure can be completed in a single visit. There are disadvantages: there is not enough high-quality evidence for its long-term durability and microleakage.1,5
Resin infiltration
ICON (DMG, Hamburg, Germany) is the only material available for resin infiltration. The system consists of: ICON Etch (15% hydrochloric acid), ICON Dry (99% ethanol) and ICON Infiltrant (methacrylatebased resin).
ICON Etch
For the complete occlusion of the lesion bodies with the infiltrant, it is necessary for the surface layer of the early enamel lesion to be made porous or to be removed. A previous study recommended the use of 15% hydrochloric acid gel for 120 seconds to perforate or remove the surface layer in order to increase resin infiltration to the lesion body.6 Furthermore, researchers suggested that acid etching improves remineralization of initial subsurface lesions because of the increased access of the ions required for remineralization.7 This effect might be helpful in order to increase the accessibility of resin infiltrant into the lesion, resulting in a better infiltration ability of the resin infiltrant into early enamel lesion. However, HCl is a very strong acid and is able to destroy the crystalline structure of the hydroxyapatite. It has been shown that the 2-minute application of 15% HCl to enamel leads to a surface substance loss of approximately 36 μm. Hence, it is important to ensure there is no contact of the acid with the areas of sound enamel adjacent to the lesion.6
ICON Dry
Ethanol is the drying agent in ICON Dry and it is used to remove the residual water at the bottom of the lesion body. However, it also decreases the infiltrant resin viscosity and can give rise to inhomogeneity and an uncured resin layer. Therefore, there is a balance between the use of the ethanol to dry the lesion to increase the ability of the resin to infiltrate the lesion, and its negative properties on the cured material.4
ICON Infiltrant
Paris and Meyer-Lueckel suggested a repeated application of the resin infiltrant to the surface lesion after surface pre-treatment because of polymerization shrinkage. In addition, the repeated application of dental adhesives will provide a more acid-resistant surface.5
Resin infiltration application
Figure 2 shows the step-by-step use of the resin infiltrant.8Figure 3 shows before and after pictures of resin infiltration on white-creamy and creamy-yellow hypomineralized defects. The infiltrant resin masks the white and less opaque areas to a satisfactory level, while it masks the creamy and yellow defect partially.
Figure 2. The resin infiltration application. (a) Pre-treatment intra-oral photo. (b) Isolate the affected teeth with rubber dam and clean the surface of the affected tooth with a bristle brush and slow handpiece. (c) Apply and rub ICON Etch on the lesion for 2 minutes using an etch applicator. (d) Rinse the etch with water for 30 seconds and then dry the lesion with water-free and oil-free air for 15 seconds. (e) Apply ICON Dry for 30 seconds. (f) Dry the tooth with oil-free air. (g) Apply the ICON Infiltrant to the tooth surface for 3 minutes. (h) Light cure for 40 seconds. (i) Post-treatment intra-oral photo.Figure 3.
(a) Before and (b) after photos of ICON resin infiltration.
Discussion
Resin infiltrant is considered a minimally invasive technique to treat mild hypomineralized lesions. Resin infiltrant is a good choice of treatment to mask mild white lesions, such as post-orthodontic or early enamel caries, and provides ideal aesthetic results. However, it can only reduce the yellowish colour and cannot mask the opacity fully.2 This might be related to the penetration depth of the resin and the porosity of the defect. However, this needs to be explored by further research.
The surface layer of the early enamel lesion is a highly mineralized layer. Paris et al and Cochrane et al reported on a larger range of surface thickness, ranging between 10 and 160 μm and 35 and 130 μm, respectively. Both studies reported that the lesions had 90–92% of the mineral content of that found in sound enamel.4,7 ICON Etch removes this layer for ICON Infiltrant to infiltrate the lesion.8 Therefore, some clinicians question whether the benefits of the ICON infiltration system outweigh the disadvantages of removal of the surface layer of these defects.
It should be noted that the ability of a resin infiltrant to minimize microleakage between the interface of the sound enamel and resin-infiltrated surface interface is an important factor in predicting clinical success, particularly in the long term. One in vitro study showed that resin infiltrant seals the porosity in the defect and protects against microleakage in enamel lesions immediately and in the long term. The same study showed that there is greater microleakage in sound teeth than in specimens treated with resin infiltration.9 However, the researchers did not focus on the interface microleakage only. Therefore, there is still uncertainty on long-term microleakage at the interface between sound tooth and resin infiltrant.
An additional factor is the tendency of resin infiltrants for polymerization shrinkage, which may lead to marginal microleakage and thus, possible secondary caries and long-term failure. A repeated application of the resin infiltrant to the surface lesion may prevent shrinkage and marginal microleakage.5
From the present author's point of view, it is essential to assess each individual case, select suitable candidates and monitor the treatment for the benefits of the resin infiltration in both the short and long term.
Conclusion
Resin infiltration is a minimally invasive method to mask hypomineralized areas. However, case selection plays a key role. This technique has satisfactory results on mild hypomineralized defects, such as post-orthondontic white spot lesions. On moderate and severe cases, it masks the lesion partially, and other methods along with resin infiltration are required to provide the best results.
