ICON Treatment of Post Orthodontic White Spot Lesions

by Carla Elizabeth Cohn, DDS

In the dental world, new products are introduced all the time. Dental technology and our materials are evolving daily. In this evolution, products are often introduced and labeled as “ground breaking” or “revolutionary.” These descriptions are all too often thrown around indiscriminately. As dental professionals we must be able to make informed decisions about the products we choose to use in our practices.

Research and development, literature and in vitro studies bring a product to clinical trials. Clinical trials illustrate the performance of that product in vivo under ‘ideal conditions.’ However it is only once those hurdles are crossed, that it can be assessed for success in the “real world.” When I was introduced to the Icon system of caries infiltration, I was skeptical. “Prove it to me,” I thought. Since then, I have had the occasion to use Icon on several patients over the past months and I have turned from skeptic to believer. The Icon infiltration concept is truly remarkable.

Icon (DMG), caries Infiltration CONcept, is a product used to arrest further demineralization of lesions. In a nutshell, the procedure involves the use of an HCl etchant to erode the surface of the lesion for the purpose of exposing the lesion porosities. This step is followed by drying and infiltration of an incipient lesion with an unfilled low viscosity light cured resin material. This micro-invasive treatment method creates a diffusion barrier not only on the surface but within the hard tissue thus stabilizing and arresting the caries progression.

In order to understand the process and the rationale for case selection, one must first look at the aetiology of demineralization. The demineralization process begins with an acid attack (H+) and subsequent mineral loss (Ca+ and PO4) from the enamel surface of the tooth (Fig. 1).

In delving further in the study of the aetiology of demineralization and the end result, caries, there are three basic requirements that affect that development. These three prerequisites are: cariogenic bacteria, fermentable carbohydrates and a tooth, as is pictured in the centre of the Venn diagram (Fig. 2).1 Affecting the development of caries, in the innermost green circle, are those protective factors which, if present, can enhance remineralization and prevent demineralization. These include, but are not limited to; fluoride exposure, calcium and phosphate availability, glass ionomer restorative or preventative therapy, chlorhexidine use, xylitol exposure, and use of sealants. The outermost blue circle represents both the controllable and uncontrollable risk factors that a patient presents with, including but not limited to; their oral hygiene habits, medical history, dental history, socioeconomic status, diet, and dental IQ. The protective factors and the risk factors all interact and determine the remineralization and demineralization equilibrium and thus the risk, or predictability, of a patient developing a carious lesion.2

In a healthy mouth, this demineralization process is balanced with remineralization, as described by Featherstone. Although remineralization can occur naturally, from salivary minerals, it is a slow process. The demineralization/remineralization balance is influenced by many circumstances (Fig. 3).3

In an unhealthy, or unbalanced mouth, with repeated acid attacks, the demineralization process overtakes the remineralization. With continued mineral loss, white spot lesions can occur. White spot lesions are a preliminary stage of the caries process. These lesions occur with breaching of the enamel layer by acids resulting in subsurface demineralization. This leads to an increase in the porosity of the tooth and subsequent change in the optical properties of the enamel. The subsurface mineral loss alters the refractive index. In other words, light reflecting off the lesion behaves differently and thus we see a “white spot.”

Left unchecked, this will proceed to the stage of frank cavitations.4

Mechanism of Caries Infiltration
As long as the surface of a lesion remains intact there is a possibility for arrest or remineralization. DMG has developed a process by which these early lesions can be infiltrated with an unfilled low viscosity light cured resin and halt the progress of the demineralization. The procedure is similar in many ways to traditional restorative methods that we use daily in restorative dentistry and so it is familiar to the general dentist. The lesion must first be isolated, rubber dam is ideal for the purpose of protecting gingiva and soft tissue as well as to maintain a dry field. Local anaesthetic is not required. The tooth must be cleaned with a pumice or non fluoridated prophylaxis paste. The surface of the lesion is then treated with Icon-Etch an etchant of 15% hydrochloric acid.5-7 This is applied with the provided syringe to an area extending approximately 2mm around the edges of the lesion. The hydrochloric acid is left in place for the prescribed time, washed and dried. It is advisable to agitate the acid during this time period to prevent buffering and allow for a better result. An ethanol drying agent Icon-Dry, supplied in a syringe in the Icon kit, is applied as directed.8 After the drying step, an intermediate check can be carried out to see if the etching step has been successful. At this point the final result can be previewed. This preview can be seen when the Icon-Dry is applied to the lesion. If the white appearance of the lesion persists after water penetration, the etching step can be repeated up to two additional times. For particularly persistent discolorations, the Icon-Etch can be mixed with pumice powder; the Icon-Etch can then be activated when applied, i.e. applied with gentle pressure throughout the reaction time using a circular motion. Icon-Infiltrant, a resin with a high penetration coefficient, is then applied with the supplied applicator in a series of two applications and cured as prescribed.9,10 Due to the dry field created by application of the Icon-Dry, the resin is drawn into the lesion by capillary action. Once light cured, the resin infiltrant occludes the microporosities thereby preventing further demineralization.11,12 The Icon-infiltrant is applied a second time in order to stop progression of demineralization and increase the microhardness of the enamel.13 In addition to halting the progression of the demineralization, treatment with infiltration changes the appearance of the lesion. The whitish appearance is masked due to reduction of light scattering.14 The refraction index of the Icon-infiltrant is similar to enamel and so the white spot lesion is virtually “erased,” giving an excellent cosmetic result.15 The method is straightforward and the results are immediate and permanent.

Candidates for Caries Inflitration
(case selection)
It is critical to correctly identify which lesions are candidates for caries infiltration as they contain the necessary porosities for infiltration. Lesions that occur from demineralization are the only suitable candidates for this procedure. Lesions from fluorosis, hypocalcification, hypoplasia, erosion, developmental anomalies or trauma leading to enamel defects are not appropriate for caries infiltration. Think of this in simple terms, as the name implies, only lesions from caries are suitable for caries infiltration.

Post -Orthodontic White Spot Lesions
Let us examine the scenario of demineralization and remineralization in the case of a patient with orthodontic banding and bracketing. The combination of a decreased ability of the patient to maintain proper oral hygiene, an increase in surface area for plaque and biofilm to accumulate, and a lack of motivation of a teenaged patient will l
ead to continuous acid attack. White spot lesions can develop in as little as one month.16-18 These lesions have been reported at incidences as high as 73%-95%.19-20 The lesions are not usually detected until debanding, presenting a significant esthetic problem. Patients, parents, orthodontists and general dentists all have the same perception that the appearance is highly undesirable.21 Studies show that Icon proved to be most effective at masking white spot lesions22 and less resistant to formation of new white spot lesions when compared to treatment with therapeutic fluoride solutions.23 Furthermore the colour stability of caries infiltrated teeth is durable.24,25 Case studies have been reported with excellent outcomes.26,27 In cases where white spot lesions are treated during active orthodontic therapy, the question of bond strength to treated surfaces must be raised. It has been shown that resin infiltration of demineralized enamel does not affect the bond strength of ortho-dontic brackets.28

Case Study
Recently a beautiful young girl was in my office for her post orthodontic cleaning and fluoride treatment. The young lady and her family had been patients of mine for several years. When I sat down to do her “check up,” the young girl and her father told me how upset they were at the unsightly spots left behind after her braces had come off. Her home care had been less than stellar during her orthodontic treatment and she had white spot lesions from cuspid to cuspid. Lovely straight teeth, covered in blemishes (Fig. 4).

Not wanting to make any promises I couldn’t keep, I told her I had a new product I could try.

No local anaesthesia is necessary, however to help keep my patient as comfortable as possible, I placed a liberal amount of topical anaesthetic to the gingiva, particularly where the rubber dam clamps would be placed.

I prefer a triple mix of topical anaesthesia — a compounded mix of 10% lidocaine, 10% prilocaine and 4% tetracaine in an aqueous base. Dry field is essential for success. Rubber dam is placed to isolate the field — do not use rubber dam made with thermoplastic elastomers (Figs. 5 & 6). Rubber dam should be inverted, or ideally ligated to prevent leakage or saliva contamination.

Prophylaxis is completed, teeth are rinsed, then dried. Attach the smooth surface tip to the Icon-Etch syringe and extrude the hydrochloric acid by twisting the syringe. Etch should extend approximately 2mm around the edges of the lesion and be placed for two minutes (Fig. 7). Once in place the etch should be agitated with the brush tip as it will buffer shortly after contact with the surface of the tooth. Etching process was repeated a second time for this case. Rinse for 30 seconds and dry completely with oil free air.

Apply Icon-Dry (99% ethanol) to the dried surface and leave undisturbed for 30 seconds (Fig. 8). Dry completely with air.

At this point remove direct overhead light source to avoid premature curing of the infiltrant. Attach a vestibular tip to the Icon-Infiltrant and apply infiltrant by twisting the syringe. Leave undisturbed for three minutes (Figs. 9 & 10). Maintain a moist surface by continuing to add infiltrant periodically during this time period. This ensures an adequate supply of resin to the lesion. Remove any excess material and light cure 40 seconds. Repeat the infiltration process with a new vestibular tip. Leave undisturbed for one minute, remove excess again and light cure an additional 40 seconds. Final polish with Shofu OneGloss (Fig. 11). Remove rubber dam (Fig. 12).

I’m not sure who was more excited about the outcome of this case. Perhaps it was a toss up between my patient, her father and myself. The procedure was fast, incredibly simple and completely pain free. Immediate result was nothing short of incredible. For patients who present with unsightly white spot lesions this truly is a life changing procedure.OH

Dr. Cohn maintains a private practice at Kid’s Dental and at Western Surgery Centre in Winnipeg, MB. She is a clinical instructor, part-time, in the Department of Preventive Sciences, U. of Manitoba. A small honorarium was received for this article.

Oral Health welcomes this original article.

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