Biological & esthetic management of enamel white discoloration: Erosion infiltration technique

Hana Sarraj* – Post graduate Student, Department of Restorative Dentistry-Endodontics, Faculty of Dental Medicine, Monastir, Tunisia

Emna Hidoussi* – Assistant Professor, Department of Restorative Dentistry-Endodontics, Faculty of Dental Medicine, Monastir, Tunisia

Neila Zokkar – Professor, Department of Restorative Dentistry-Endodontics, Faculty of Dental Medicine, Monastir, Tunisia

*Both authors contributed equally to this work

Dental News Magazine – March 2019

Abstract

Early stage caries (White spots), fluorosis, traumatic hypomineralizations and molar incisor hypomineralization (MIH) all present to differing degree, clinical symptoms involving white marks on the enamel. 

It can impact patients’ quality of life. The most conservative treatment in such cases is erosion-infiltration. This treatment using Icon® (DMG, Hamburg, Germany) is one of the most conservative and efficient protocols. 

The Icon® treatment was initially proposed as a simple and minimally invasive alternative for caries treatment of initial proximal lesions, but surprisingly the technique proved a high ability to mask the white spots by modifying the refractive index of the lesion. 

The proposed strategy is not based on the elimination of dysplastic enamel, but on masking the lesion by infiltrating the porous subsurface enamel with a hydrophobic resin that has a refraction index closer to that of sound enamel, after permeating the non-porous surface enamel through hydrophobic acid erosion.

This article provides an overview of different indications suitable for treatment with the technique of resin infiltration (Icon®, DMG), such as white-spot lesions (WSL), enamel fluorosis, and molar-incisor hypomineralisation (MIH) in different patients.

Key words: Infiltration, White spot lesion, Fluorosis, MIH

Introduction

Clinically, early carious lesions in enamel is initially seen as a white opaque spot and is characterized by being softer than the adjacent sound enamel. It becomes even whiter when dried with air. These lesions may present a serious aesthetic problem along with the progression of demineralization ¹. These white spots can be the result of different factors: early stage caries (due to plaque accumulation and bad oral hygiene) near the gingival line or around orthodontic brackets, fluorosis, medicine intake, molar incisal hypomineralization (MIH) and traumatic hypomineralization ². 

Management of this type of white spot lesion is generally by means of topical application of Fluoride therapy, Casein-Phospho Peptide-Amorphous Calcium Phosphate pastes, Novamin (calcium sodium phosphosilicate) ³. All these treatment modalities end up in surface remineralization, but the subsurface is still porous.

To overcome the drawback of retaining a porous subsurface caries, resin infiltration seems to be a promising and less invasive treatment modality. In this method, the subsurface porosities are occluded by a clear hydrophobic resin applied on the surface of the conditioned lesion ⁵. 

The resin infiltration technique prevents further progression of the lesion using a low-viscosity resin with a high penetration coefficient, filling the enamel intercrystalline spaces ⁶.

A reduced visibility of infiltrated WS-lesions is an additional positive side-effect, which is due to the similar refractive index of the infiltrated and sound enamel areas. This technique has been reported to remove the whitish opaque color therapy changing the color and translucency of the white lesion ⁷.

The purpose of this clinical report was to describe and illustrate a minimally invasive technique that improves the esthetic aspect of the white spot lesion.

Clinical Cases report

This article presents a series of three cases of patients aged between 20 and 26 years who exhibited enamel white discolorations in esthetically compromised tooth areas. Anamnesis and clinical assessment were performed to determine the etiology of discolorations. 

All patients signed an informed consent authorizing the treatments and use of images. The treatment decision was based on minimal intervention dentistry, using the resin infiltration technique with low-viscosity resin (Icon®, DMG, Hamburg, Germany) as an attempt to mask these lesions.

Case 1 (Figure 1) were diagnosed as postorthodontic white spot lesion. Case  2  very mild fluorosis (Figure 2) Case 3 (Figure 3) was classified as hypomineralized spots resulting from molar incisor hypomineralization.

When lesions were close to the gingival margin, a conventional rubber dam with ligatures was used to protect the oral soft tissues, deflect the gingival tissue, expose the cervical portion of the tooth, and provide a clean and dry working field. On the other hand, when no deflection of the gingival tissue was necessary, a resinous gingival barrier (liquid rubber dam) was used. After cleaning with prophylaxis pumice, the affected areas were etched with 15% hydrochloric acid (Icon-etch) for two minutes and then washed with water spray for at least 30 seconds. 

At this time, the lesions were assessed for color alteration, and if no visual color change was obtained with water, the etchant was applied again for an additional two minutes, until some color alteration could be observed at the wet eroded surface. The surface was then air dried, and ethanol (Icon-dry) was applied for 30 seconds to maximize the water removal inside the lesions. The lesions were air dried again, and the surfaces exhibited a chalky white appearance. The resin infiltrant (Icon®) was then applied on the lesion surface, and it was allowed to penetrate for three minutes. Excess resin was removed using a blow of air, and light curing was performed for 40 seconds. 

The resin infiltrant application was repeated for one minute, followed by light curing for 40 seconds. The surfaces were polished using fine-grained abrasive flexible discs, rubber points, and finishing strips, depending on the treated area. An immediate esthetic improvement, with partial or total color masking, could be observed after treatment. The final pictures were obtained one week after the end of the treatment, allowing rehydration of the teeth and gingival tissue repair.

Case Report 1

A 24-year-old female patient reported to our department of restorative dentistry and endodontics with a chief complaint of white patches in the lower tooth. 

After oral examination, she presented with mild to moderate postorthodontic WSLs at the right lower canine and premolar (Figure 1a) following treatment with a fixed orthodontic appliance for two years at the Department of Orthodontics. 

Informed consent was obtained from the patient and treatment plan was established as Caries Infiltration with ICON® (DMG, Germany) (Figure 1b, c, d) 

Case Report 2

A 26-year-old female patient who did not have any problems in her medical history was referred to the department of conservative dentistry and endodontics, with a chief complain of white lines on her maxillary incisors and brown and yellow discolorations on the other maxillary teeth. 

Informed consent was obtained from the patient and treatment plan was established as Caries Infiltration with Icon® (DMG, Germany) and dental whitening with 16% carbamide peroxide. (Figure 2)

Case Report 3

A 23-year-old female patient presented with white spot lesions on her upper teeth. The spots are easily visible in the frontal view of the anterior teeth: a big white spot on tooth number 21  and 11. This patient was looking for an esthetic solution for these defects in her smile (Fig. 3). 

After the clinical and radiographic examination, the occurrence of hypomineralization of the upper and all the first permanent molars characterizing MIH was diagnosed.

In our first case describing superficial infiltration we limited application of the erosion/infiltration technique to cases which required no dental preparation, such as early stage caries, most types of mild fluorosis and hypomineralization resulting from superficial traumatic lesions. But the technique as presented resulted in failures in many cases such as where lesions originate at the dentino-enamel junction and extend into the enamel, as in MIH. This is why treatments of MIH lesions by erosion/infiltration were never, or almost never, successful.

In view of the high level of prevalence of such cases, it was essential to find solutions to overcome these failures. The concept of deep infiltration involves paying a price in the form of mild mutilation of the enamel through preparation by sandblasting or milling so as to ensure that the infiltration can indeed reach the “ceiling” of the lesion in the case of MIH or spread through almost the whole of the lesion if the latter is deep (fluorosis or deep traumatic hypomineralization.

Discussion

White marks and white lesions on anterior teeth can be unsightly. Patients often seek treatment to have these marks eradicated. Whilst there is a wide array of treatments available, which includes whitening as a first choice⁷ and bonding over the mark as a last option, a new technique using resin infiltration has been introduced ⁸. 

Tooth-whitening techniques have been employed, with the aim of bleaching regular enamel, camouflaging the white-involved areas, and making the tooth color more uniform. Nevertheless, the results are not always satisfactory, and in many cases, microabrasion with pumice and hydrochloric acid needs to be performed. Enamel microabrasion can produce acceptable esthetic improvement in shallow lesions, ¹¹ and although the amount of enamel loss is related to the acid type and concentration, abrasive particles, duration and number of applications.

Minimal invasive dentistry by resin infiltration technique seems to provide a good solution in treating early enamel lesions. The ultimate goal of treating discoloration of teeth is to get an acceptable aesthetic result in the most conservative way possible. Initially resin infiltration was used as a method of treating incipient caries ⁹ either interproximally or on the smooth surfaces of teeth ¹⁰. 

The technique using Icon® DMG advocates the etching procedure to remove mineral of the surface layer, less than 40 µm demineralized enamel ⁵. The purpose of the etching procedure is to expose the lesion porosities there for low-viscosity light-curing resin can infiltrate, filling microporosities of the white spot lesion and replacing the initial appearance of the enamel. 

In this case, we found yellow and  brown discolorations, so  microabrasion and bleaching using 16 % de carbamide peroxide to improve the esthetic appearance of the the discolored teeth. Infiltration of the enamel by resin allows to obstruct the diffusion pathways for acids, external colorations and dissolved minerals ¹⁵.

It seems necessary to evaluate the accurate depth of the lesion, so we use trans-illumination test with polarized light. Then Two cases may occur:

•   Blurring opaque aspect means that the lesion is deep

• Limited opaque aspect means that the lesion is superficial

We might have also an heterogeneous aspect that means a variable depth and thickness of the lesion.

An indicator is required to show whether the ceiling of the lesion has been reached. The alcohol can play this role. After etching the enamel surface, it is placed onto the surface as a drying agents and left for 2 minutes. Since it has a relatively high refractive index it offers a preview, in a less effective way, of what will be achieved by the resin. When the application of alcohol seems to mask the lesion to some degree, this is a sign that ceiling of the lesion has been reached or, in the case of a deep lesion, that the infiltration will be sufficient. If alcohol does not produce this effect, either chemical erosion should be repeated or further microabrasion should be performed ¹².

At the final step, the resin (Icon-infiltrate) can be applied for 2 -5min. It is a very low viscosity, TEGDMA-based resin. It uses capillary action to infiltrate and goes very deep into the lesion. We noted that this resin appears slightly since it contains camphorquinone. After the Photopolymerization which was done for 40s, the yellow tinge will disappear because the camphorquinone has been consumed. 

A positive side effect of resin infiltration is that enamel lesions lose their whitish appearance when their microporosities are filled with the resin and look similar to sound enamel.  Since the refractive index of the infiltrant material (RIIcon = 1.52) is close to enamel (RIhydroxyapatite = 1.62-1.65), when the lesion is filled, the optical properties of affected enamel are modified and lesions are masked¹². The infiltrant (Icon®, DMG) can be used for both the vestibular and interproximal noncavitated lesions. A limitation of this technique is the need to follow accurate diagnosis criteria to distinguish between the developmental and non-developmental opacities, because the resin infiltration shows limited effects in cases of developmental defects; furthermore it is a radiolucent material, which may be a concern to some dentists. These factors determine the success of treatment ¹³. 

It is also important to consider that the depth of resin infiltration is 60 µm, therefore the best treatment must be assessed for the elimination of white spots given deeper lesions could be detected even after treatment with resin infiltration ¹⁴. Since the fluorotic and hypomineralized enamel exhibits a subsurface reduced mineral content, similar to an initial caries lesion, the indication of the low-viscosity infiltration resin technique was recently broadened to mask the undesirable esthetic appearance in these cases. ^{19, 24} Nevertheless, because of the high variety of traumatic hypomineralization topographic characteristics, the results of treatment using infiltration are difficult to predict. In fact, this case series presents an improvement of the esthetic appearance of the white discolorations, with patient satisfaction. 

However, the masking effect was not always complete, mainly in the cases of traumatic hypomineralized discolorations. This may be related to the histology of these defects, since their depth and morphology are highly variable. In some cases, the defect presents a circular shape, forming an acute angle with the enamel surface which hampers the infiltration of the resin on the margins and results in a visual contouring of the lesion known as the ‘‘edge effect.’

This deep infiltration technique has been proposed for the treatment of deep spots originating at the surface (fluorosis traumatic hypomineralization) or for those, like MIH, that originate at the dentino-enamel junction and for which, until now, no mini-invasive treatment was available. The method described can be applied to all spots, whatever their etiology. In fact, treatment of all white spots can begin without sandblasting or milling; then, if this is not sufficient, additional chemical and mechanical treatments can be undertaken until alcohol produces an optical change ¹². 

Conclusion

The infiltration technique is a minimally invasive, and esthetic treatment of white spots. It has many advantages such as preservation of hard tissue, stopping the demineralization process by increasing the resistance of the enamel to demineralization, sealing of the micropores and cavities and minimizing the risk of developing secondary caries. This procedure is also well accepted by the patient and practitioner. The only disadvantage is the high staining potential of the infiltrating resin over time. This can be resolved by covering the resin with a thin layer of composite.

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