White Spot Lesions (Part I): A New Topographic Classification (WSTC)

Dr. Fadwa Chtioui – DDS and Postgraduate Student, Department of restorative Dentistry and Endodontics, University Hospital of Sahloul, Sousse – Tunisia (cldfadwa@hotmail.com)
Dr. Omar Marouane – Assistant Doctor, Department of restorative Dentistry and Endodontics, University Hospital of Sahloul, Sousse – Tunisia
Dr. Nabiha Douki – Head of the department of Odontology, Professor in Restorative Dentistry and Endodontics, University Hospital of Sahloul, Sousse – Tunisia

Dental News December Issue 2017

Keywords

Cosmetic dentistry, Demineralization, Esthetic dentistry, Minimally invasive dentistry, Restorative dentistry, Enamel

Abstract

Enamel demineralization is frequently encountered in dental practice. Histologically, hypomineralization is the common feature and several etiologies stand behind their clinical appearance.
Recently, resin infiltration technique was introduced to mask these enamel lesions.
The principle of coating the enamel with a low-viscosity resin was recently adopted in an innovative treatment approach through which the hypomineralized enamel is masked using a resin infiltration technique. This treatment was initially proposed for treating enamel carious lesions, the best-known superficial lesions. Over time, the indication evolved and was extended to all etiologies responsible for enamel white lesions. However, from a topographic point of view, the location of hypomineralized lesion differs based on the corresponding etiology and the appropriate choice of a specific treatment for each location is necessary. To date, the etiology of the lesion is solely considered when identifying their topographic location within the enamel. Conversely, the correlation between etiology and topography remains theoretical and is, however, regarded to be quite weak especially in cases where only a partial improvement of the esthetic appearance was seenRefrenceTherefore, the results sustain unpredictable in most cases of such lesions regardless of their plausible etiologies. As this idea kept grabbing our attention during our study, it was compelling to figure out the missing link between etiology and the topography of hypomineralized enamel areas. Likewise, a clinical evaluation of the enamel white lesion’sdepth must be adopted as, technically, the latter seems to exclusively influence the treatment outcome.

Aim This workproposea new topographic classification along with a new set or classification criteria of enamel white lesions for a more proper management of hypomineralized teeth comprising a major breakthrough in their treatment. M amd m: The means of Visual examination and transillumination have served as references to develop this new topographic classification.

Introduction

The clinical aspect of early-stage caries (white spots), fluorosis, traumatic hypomineralization and molar incisor hypomineralization (MIH) depends on the severity of the disease and involves the presence of demarcated to diffuse enamel opacities.
The defective enamel may appearas chulky-white or white-creamytoyellowish or yellow-brown spots. . [Denis et al., 2013] Whereas histologically, hypomineralization is the common feature in which such enamel lesions may result[Denis et al., 2013].

Remineralization, bleaching, microabrasion and composite restoration, or their combination, are different treatment approaches in managing this kind of lesions[Mastroberardino et al., 2012; Pini et al., 2015; Senestraro et al., 2013]. Recently,resin infiltration technique has been introduced to optically mask these enamel hypomineralizedlesions andimprove their mechanical properties [Kielbassa et al., 2010; Paris et al., 2013].
In order to successfully infiltrate these lesions, having the necessary knowledge of their topographic location seems crucial. Right up to the present day, this topographic knowledge has been based on the etiology of these lesions despite the fact that new studies have emerged to provide data on the little-known subsections of white-spot lesions[Denis et al., 2013] + ref . And while there is a good correlation between such lesions, their etiologies seem to present an unpredictable location of hypomineralized enamel surfaces. And it should be mentioned that several studies have shown only partial improvement of esthetic appearance of enamel white lesionswhile the results sustain unpredictable in most cases of such lesions regardless of their plausible etiologies[Attal et al., 2014; Tirlet et al., 2013] rephrase to more simple idea) . Indeed, in order to obtain successful infiltration of the lesion’s body, the surface layer has to be removed by the application of an etching procedure repeatedly [Meyer-Lueckel and Paris, 2008b, a]. Thus, when hypomineralized lesions are confined at the inner part of enamel, the classic protocol of infiltration technique seems to be inappropriate [Attal et al., 2014].

Therefore, the missing link between etiology and topographic position
of the hypomineralized enamel surfaces has impelled our main attention to set forth a new approach in locating enamel white lesions. Consequently, a clinical evaluation of their deepness and thickness must be consideredwith a view to identifying a specific treatment for each topographic location.
As hypomineralization is the common feature to all enamel white lesions, this conclusion can also be applied to fluorosis, traumatic hypomineralization and molar incisor hypomineralization (MIH). (Keep this for discussion )

The aim of this work is to propose a new topographic classification of enamel white lesions, seeking to introduce a new paradigm concerning their treatment regardless of their causes in which we provide for each topographic location, a codified procedure and a more conservative treatment for a better aesthetic result.A second article will be devoted more specifically to the treatment of these spots with regard to this new classification.

Widely used classification systems in enamel hypomineralization

Many classifications have been proposed for each etiology being responsible for enamel white lesion [Chawla et al., 2008b; Clarkson, 1989; Ismail et al., 2007].                                                                                                                                                                                                         Visible white lesions on wet smooth surfaces, without any cavity detected, have been regrouped in table 1.
Clinically, these descriptive classifications are based on the presence of dematerialized areas and the color of enamel opacities. The DDE indeximplies as well enamel hypomineralizationregardless, however, of the plausibly attributed etiology.
Such a descriptive classification seems to be more convenient than an etiological index, recording both, non-fluoride and fluoride-induced defects [Clarkson, 1989; Clarkson and O’mullane, 1989; Guerra et al., 2014].

However, with reference only to the topographic location (features) and the thickness of the hypomineralized enamel, the treatment can be genuinely influenced. Thus, from a therapeutic point of view, all of these classifications are inappropriate for repairing such lesions especially while using contemporary minimally invasive technique as resin infiltration.

Accordingly, reassembling all of theselesions inone single classification depending on the deepness and thickness of the lesion seems to be absolutely necessary to treat enamel hypomineralization.

 

Available methods to determine depth-related spatial distribution of the lesion

To determine the topography of an enamel white lesion, knowingthe etiology of these lesions could be helpful. Indeed, as suggested by Denis et al, white spot lesions, fluorosis and traumatic hypomineralization involve subsurface hypomineralization under a relatively well-mineralized surface layer and contrary to these lesions; MIH always begins at the dentino-enamel jonction and extends to the surface layer [Denis et al., 2013].

As much interest this approach may generate, it remains theoretical, and the correlation between etiology and topography is, however, considered to be quite weak [Attal et al., 2014]. Likewise, using this method for a direct evaluation of the contour features of hypomineralized enamel surfaces is not actually possible.

Recently, in vivo imaging of the dental surfaces is done using reflectance confocal microscopy (RCM). This scanning technique, initially processed for skin experiments, has been applied to oral imaging by several authors. It can optically scan horizontal planes, and thus, dental surfaces, layer by layer, reaching 0.3 mm of maximum depth.

However, RCM is not adaptable to all dental surfaces, and so, their uses remain limited and can’t be a clinically reliable approach [Contaldo et al., 2014].

To directly assess the surface of the enamel lesion; several studies reported the use of optical microscope or scanning electron microscope (SEM). However, these methods require tooth extraction followed by ex vivo experiments [Kielbassa et al., 2009; Pearce and Nelson, 1989].

 

Visual examination application

To date, there are no clinical methods describing the topography of enamel white lesions.

However, visual examination can be useful to determine their topographic location.
The perception of white lesions on enamel surfaces is a complex phenomenon, yet, based on the available data, a meticulous visual examination can allow us to read a “topographic mapping” of the lesion.
Optically and contrary to sound enamel, hypomineralized enamel is a relatively heterogeneous tissue made up of organic and mineral materials, with different refractive indices. In situ, the multiplicity of these indices lead to a diffuse reflection of light, and therefore the lesion appears white [Denis et al., 2013].

On the other hand, from a clinical point of view, Torlakovicshowed a good correlation between white intensity and volume of hypomineralized white lesions .[Torlakovic et al., 2012]. In fact, the depth of enamel hypomineralization can significantly explain the range of shades of white lesionsclinically observed. So genuinely, some white lesions are only slightly whiter than sound enamel, and air drying is required to detect them, whereas others are intensely white, easily seen even on a wet tooth surface [Torlakovic et al., 2012].

Moreover, enamel white lesions, may present a white-yellowish or creamy appearance [Contaldo et al., 2014]. The latter is due to the lesion depth as well as to the optical properties of sound enamel. In fact, in regard to the small size of hydroxiappatite crystals (0.15 à 0.05 μm), the enamel, most likely scatters short wavelengths leading to an increased backscatter of blue light from its surface which in return reflects a bluish appearance(20). During significant light emission however, it filters and shifts blue to red and shorter orange wavelengths [Lasserre, 2007].
Indeed, Zijp reported that sound enamel, observed in daylight, appears to be pale yellowunder transmitted light [Zijp et al., 1995]. Therefore, when the hypomineralization is confined at the inner third of the enamel, the reflected light coming out of this lesion is rather yellowish, and clinically, the lesion shows a creamy discoloration.

Discolored white lesions

Enamel hypomineralization, whether superficial or deep, may be discolored [Attal et al., 2014]. In carious lesions, it’s called brown spot. It develops from white spot lesions, which incorporates chromogenic molecules during mineralization process [West and Joiner, 2014] causing the staining of the teeth as seen during post-eruptive periods in cases of fluorosis, in which the porous hypomineralized enamel results in extrinsic dental stains [Watts and Addy, 2001]. Molar incisor hypomineralization may also become dicolored.
Recently, Chawla et al. modified the Leppaniemi index and classified MIH into three categories based on their colors. Accordingly, the white-cream opacities refer to mild hypomineralization, while teeth with yellow tobrown discolorations and/or posteruptive enamel breakdown are described as moderate to severe hypomineralized lesions [Chawla et al., 2008a; Leppaniemi et al., 2001].
Several authors have demonstrated that white enamel opacities have greater hardness, less porosity, than yellow-brown hypomineralized enamel [Fagrell et al., 2010; Jälevik and Norén, 2000]. Moreover, Farah et al. also showed a good correlation between mineral density and clinical appearance [Farah et al., 2010].

From a topographic point of view, studies have shown that MIH originates at the dentino-enamel junction and, depending on its severity; it may extend towards the enamel surface. Furthermore, while white-cream opacities have been situated in the inner part of the enamel, the yellowish or brown defects can progress through the whole enamel layer.
On the surface of more pronounced hypomineralization, no sound enamel surface zone was seen which can constitute a possible pathway for bacteria or extrinsic substances [Fagrell et al., 2010; Fagrell et al., 2013; Jälevik and Norén, 2000].

Despite the fact that there is a link between the colored lesions and topographic location of the hypomineralization,the presence of uncolored lesions does not allow us to apply this method for all lesions.

To overcome the difficulty in locating discolored lesions, transillumination can be useful. Indeed with reference to this tool, we can manage tosignificantly evaluate the opacity of the lesion.

Using transillumination

From an optical point view, sound enamel is translucent. It permits not only the passage of light, but also disperses it. However, enamel hypomineralized lesions are opaque and prevent the passage of light [Powers and Sakaguchi, 2006].

Based on this criterion, fiber optic transillumination (FOTI) has been used in vivo in caries detection for many years. It offers an alternative method of diagnosis of decayed tissue to supplement the clinical examination. It is a simple, non-invasive, painless method and can be used repeatedly with no risk to the patient.

FOTI works due to differences in light transmission between normal and carious lesions. Indeed, the disruption of crystal structure, which occurs in hypomineralization has the ability to absorb light photons producing a gray shade in this kind of lesions.

The procedure has been proven histologically and has levels of sensitivity and specificity that exceed those of radiography [Davies et al., 2001; Pitts and Stamm, 2004; Strassler, 2014; Zandoná and Zero, 2006].

 

Based on the same optical law, the supplemental use of FOTI with other etiologies responsible for enamel hypomineralization can be helpful in order to evaluate depth and thickness of these lesions. Indeed, when hypomineralized lesion is covered by enamel, the transmitted light dispersed from this translucent layer revealspoorly-defined and fuzzy enamel opacity underneath sound enamel. (25)
Presumably , we may assume that just like underwater optical imaging where illumination techniques illustrate the depths being portrayed; this new technique may provide an idea about the 3-D depth information for optically shallow areas.Accordingly, the subsurface lesion appears well demarcated by the scattered light under transilluminationas the thin layer of enamel -if it ever exists- will not distort light and rather appear transparent.

The use of transillumination and visual examination in the elaboration
of a topographic classification of enamel white lesions

As suggested by Denis enamel, a white lesion may present different locations. It may be deep, superficial, or both combined in one lesion.

Based on the optic law that defines enamel hypomineralization and sound enamel, a clinical topographic classification based on visual examination and transillumination can be made.

 

Superficial lesions

Regarding the optical properties of the enamel, the incident light transmitted towards the lesion is directly reflected to the eye and when it’s superficial since reflected light is not dispersed nor distorted; thus, the lesion appears white. Nevertheless, depending on the thickness of the lesion, the appearance may differ.

Thin superficial lesions are slightly whiter than sound enamel making the lesion hardly distinguishable from it and can only be detectable only after a prolonged air drying.
On the other hand, when the superficial lesion is quite thick, the considerable difference in refractive indices between sound and porous enamel yields to intensely white lesions easily visible even on a wet surface.

In transillumination the lesion absorbs light, transmitting the light beam entirely when it’s thin and thus yielding a slightly opaque appearance with less-pronounced edges.
This process is yet reversed in cases of thick lesions which appear quite darker as they prevent the passage of light.

The poor light dispersion through these superficial lesions gives appearance of a roughened white spot within well-demarcated margins[Fleming et al., 2004].

Deep lesions

Due to their topography, deep lesions differ from superficial ones. In fact,
a hypomineralized lesion is covered by enamel. Optically, the incident light beam passes through thetranslucentsound enamel, reflects at the lesion site,re-crosses through the translucent sound enamel coating, scatters then it re-emitsfrom the surface back to the eye.

Light-penetration and light-scatteringthrough sound enamel gives forth a creamy and yellowish appearance, a criterion ofdeep lesions. In transillumination, a more complex optical phenomenon takes place.

When the hypominerelazied lesion is covered withtranslucent sound enamel, the latter disperses thetransilluminated light away from the enamel opacity,which, as a result, appears poorly defined and fuzzy [Jälevik and Norén, 2000].Besides, the deeper is the hypomineralized enamel, the more important is the scattering and the fuzzierthe lesion would be [Fleming et al., 2004; Kersten et al., 2006].

Mixed lesion

Topographically, part of the lesion is deep and another part is superficial,which makes both characteristics present clinically and under transillumination.

Clinically the lesion takes onboth a white and creamy appearanceshowing a heterogeneous aspect in transillumination. Depending on the topography of the lesion, poorly defined edges tend to occur with the clearly demarcated ones at parts of the same lesion.

These observations can be easily concluded when a tooth shows a mixture of deep and superficial lesion aspect or when we remove the superficial layer of enamel to transform deep lesions into superficial ones.

Moreover, the degree of opaqueness reflects the degree of hypomineralization, i.e. the degree of porosity, implicating that the more opaque the enamel appears in incident light, the more porous it is since porous enamel scatters light more than does sound enamel [Villarroel et al., 2011].

A: In Hypominerilized Lesions, the changes of refractive index, the light is thus deviated at each interface and reflected, becoming imprisoned in an “opticalmaze” that is over-luminous and therefore perceived or seen as white and opaque by the eye on account of the excess brightness which depends of the thickness of the lesion in cases of Superficial Lesions.

B: In cases of deep lesions, the hypomineralized lesion is covered by enamel. The incident beam light passes through the translucent sound enamel, it is reflected at the lesion, then re-passes through the translucent sound enamel and re-emerges from the surface to the eye with a creamy to yellowish appearance.

C: Mixed Lesion show a part of the lesion is deep and another which is superficial. Then both characteristics of deep and Superficial Lesions are present on visual examination and under transillumination. 

Classification

Based on all the already-cited information, in wet conditions, meticulous visual examination, the white intensity as well aslimit-and-opacity features under transillumination of white lesions have served as reference to develop this topographic classification.

Three types of enamel white lesions were proposed. As a consequence,all the etiologies responsible of the enamel hypomineralisation are unified.

After analyzing and studying more than a hundred forms of white lesions in our dental department, we found out that they may fall under one of the following categories

 

Conclusion

The choice of the basic range of appropriate treatments existing today, erosion/infiltration and/or micro/mega-abrasion will then be much easier as the dentist who is now capable of estimating the 3-d image of the lesion. And based on the optical properties of sound and hypominerilzed enamel, we have managed to set forth a new topographic classification for enamel lesions which allows usto choose the best non-invasive treatment with a fairly predictable result.
The classification comes exclusively with a purely therapeutic goal as it clinically guides us towards the appropriate treatment option for each lesion based merely on its topography.

Acknowledgement
Research laboratory of oral health and oro facial rehabilitation LR12 ES11, Faculty of dental medicine, Monastiruniversity, Tunisia.

 

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