Orthodontics and enamel spots. Benefits of a minimally invasive approach, guidelines for the orthodontist

Enamel spots are frequently reported as an aesthetic complaint. In the case of orthodontic treatment, these spots can be a cause for concern, on one hand, for the orthodontist: what is the origin of these spots? Is it possible to bond directly on these areas without any risk? How and when should they be treated? On the other hand, from the patient’s point of view, the appearance or persistence of these spots can decrease the esthetic benefits of treatment.The aim of this article is to describe the diagnosis, treatments, and management guidelines (protocols and chronology); present the benefits of the minimally invasive approach; and propose systematic guidelines for orthodontists.


INTRODUCTION
Orthodontics and enamel spots. Benefits of a minimally invasive approach, guidelines for the orthodontist  -to describe a simple approach to set the correct diagnosis; -to analyze, according to the literature, the impact of preventive techniques on the appearance and/or development of enamel spots; -to show the benefits of minimally invasive techniques for the treatment of these spots within the framework of orthodontic care; -to propose a care procedure before.
White enamel spots, also called opacities, are always related to hypomineralization, which is a decrease in the local concentration of minerals.
This decrease may be because of -a loss of minerals. This is the case with early-stage carious lesions. During the carious process, bacteria produce acids, which dissolve minerals; -a lack of minerals being incorporated during amelogenesis, which occurs in some pathologies during the mineralization phase: fluorosis, permanent tooth trauma, and molar incisor hypomineralization (MIH). It is therefore possible to distinguish between two types of lesions:  These lesions are characterized by the following: always located around the plaque accumulation zone; circular in shape when anterior, semicircular in shape when posterior; chalky white/yellow/brown appearance; may be associated with a loss of enamel. amelogenesis process. These lesions are visible as soon as the tooth erupts on the arch; -posteruptive lesions, which are exclusively linked to the carious process and are thus systematically classified as early-stage carious lesions.
The time of occurrence of these lesions occur in relation to the orthodontic treatment facilitates their diagnosis: The total absence of a lesion before treatment will point to a diagnosis of enamel carious lesions of the enamel (formerly called precarious leucomas).
In the end, there are only four possible diagnoses ( Fig. 1) for an almost total opacity of the enamel.

)
Pre-carious leucomas correspond to the 1st clinically visible stage of the carious process. They therefore have to appear around the plaque accumulation zone. The most common locations and forms are -circular, vestibular to the anterior teeth. This localization is specifically linked to multiattachment treatments; -semicircular, at the cervical level of the posterior mandibular teeth.
The enamel appears matte white, rough on the surface, but without any enamel cavities.
At the tissue level, the lesion starts on the surface and develops toward the dentin.

Fluorosis (Fig. 3)
Fluorosis is a hypomineralization of the enamel associated with fluoride poisoning during amelogenesis.
It is a systemic poisoning. As a result, fluorosis-related lesions are always symmetrical on homologous teeth and often found on several groups of teeth. They may appear white, yellow, or brown, depending on the degree of hypomineralization. They can be accompanied by horizontal striations.
A. ATLAN, M. DENIS, G. TIRLET, J.-P. ATTAL Trauma/infection of temporary teeth (Fig. 4) Any disturbance to the roots during amelogenesis may result in a hypomineralization lesion. This disturbance can be mechanical, such as temporary tooth trauma or infections.
The lesions associated with it can take any shape, location, or shade. They are related to the age when the trauma occurred. They are most often punctiform, located on the incisors, and are most often limited to one or two teeth. The contralateral teeth are not affected; however, there may be antagonistic tooth damage in the case of chin trauma with pressure on the temporary antagonistic teeth.
However, the most benign trauma is likely the cause of such a lesion. It is therefore common for parents or patients to not be able to remember how the trauma occurred. This aspect should not eliminate this diagnosis, which is most often a diagnosis of exclusion.

MIH (Fig. 5)
MIH is a pathological entity whose etiology remains unknown. It is defined as the presence of at least one hypomineralization lesion on a permanent first molar, whether or not it is associated with lesions on the incisors. It usually affects the canines and the second molars.
Clinically, in painless forms, the clinical course is reversed: Patients consult for spots on the incisors and it is up to the practitioner to inspect the first molars for making this diagnosis.
These lesions appear as well-defined opacities of white, yellow, or brown color involving the incisors.
The presence of restorations on the first molars or the absence of these teeth in the mouth of a person deemed to be at a low risk of developing carious lesions can point toward the diagnosis of MIH.
In the case of MIH, the lesion always starts from the junction between the enamel and the dentin. Regardless of whether it affects all or part of the enamel layer, it is always deep.  Are orthodontic treatments the cause of such lesions?
Only early-stage carious lesions may be related to orthodontic treatment.
The prevalence of early-stage carious lesions is twice as high in patients receiving orthodontic treatment (49% vs. 24%) 17 .
In 75% patients, these lesions affect more than two teeth.
The age of the patient seems to be the most predictive factor 21 : these lesions are found in 52% patients who received orthodontic treatment between the ages of 11 and 15 years, compared with 7% for patients who have been treated orthodontically between the ages of 19 and 24 years.
The retention of bacterial plaque related to the use of orthodontic equipment appears to be the basis of this problem. Thus, prevention is the best approach.
Classically, it is built around three axes: Hygiene: This is the critical point when wearing orthodontic braces. A specific toothbrush is insufficient. Additional measures must be put in place. Interdental brushes and flosses must be used daily; Diet: Limitation of the frequency of intake of sugar; Fluorination (toothpaste >1,500 ppm)/ remineralization (combination of casein phosphopeptide and amorphous calcium phosphate, Recaldent ® ): professional and outpatient, in the form of toothpaste and mouthwash.
It is evident from the perspective of the practitioner that the lack of compliance with hygiene is the cause and not the orthodontic treatment itself.

However, a study shows two interesting facts:
-There is indeed a relationship between the compliance of patients in relation to the prophylactic techniques and the development of early-stage carious lesions, but this relationship is not strong enough to be statistically significant in a sample of 80 patients 18 . -Patients with the best compliance still present with new lesions after orthodontic treatment.
In conclusion, the establishment of a strong prophylaxis is mandatory, and the compliance of the patients must be regularly evaluated. A strong compliance does not fully prevent the onset of early-stage carious lesions.
How to decrease the risk of appearance? (Clinical case # 1:

Figs. 6-8)
From an etiological point of view, it is therefore not possible to say that orthodontic treatment causes lesions. On the other hand, the likelihood of the onset of these lesions following orthodontic treatment is very high and no prophylactic techniques can completely prevent it.
Patients should be warned of this risk. In response to this problem, proposals for attaching orthodontic devices using bioactive materials, such as glass ionomer cement have been de-      appearance of these postorthodontic white spots 41,11,9,24,36 . These studies also report similar adhesion values between composites and GIC, particularly in the case of a previous etching treatment using orthophosphoric acid. However, GIC is not often used. Ergonomics and habits seem to be important barriers. Although it is easily understandable to prefer the use of composite resins in the case of direct attachment techniques, it could be very interesting to use indirect techniques for which the use of GIC is so simple, especially in cases of young patients, or in patients with poor hygiene and compliance.
Other proposals have been published, including the use of the following: -protective coatings; -elastomeric ligatures containing tin fluorides; -antimicrobials (iodine, chlorhexidine, cetylpiridimine chloride); -antibacterial nanoparticles coated on orthodontic attachments (titanium dioxide, zinc oxide); -new processes for the manufacture of ceramics by freezing (freeze casting) allowing the incorporation of antimicrobial polymers.
These proposals have not yet shown merit, or are still being evaluated.

Associated mechanical risks
Hypomineralization lesions can cause esthetic problems, but it can also make the enamel more fragile, especially when the lesion is located on the surface (clinical case no. 2, Figs. 14 and 15). This aspect is particularly problematic when attaching the orthodontic devices.   Pretreatment of the injured enamel is then recommended before orthodontic treatment. (see the § following "infiltration")

Remineralization
Because these lesions correspond to a decrease in the mineral concentration, the ideal treatment is their remineralization 7 . Unfortunately, remineralization treatments are exclusively indicated for eruptive lesions, when the mineral loss occurred after the eruption of the tooth, i.e., in the case of early-stage carious lesions.
On the other hand, their effectiveness is limited to the most superficial of lesions.
ICDAS (International Caries Detection and Assessment System) Stage-1 lesions (see table) disappear completely after remineralization treatment. However, these lesions do not create cosmetic problems for patients.
In the case of ICDAS Stage-2 lesions, the remineralization treatments result in a reduction of up to half the size of the lesion 40 . On the other hand, after 3 months of treatment, there is no more improvement 30 An alternative treatment should be considered.
There are currently no clinically evaluated protocols that have demonstrated superiority. The results of the different studies cannot be compared because of the diversity of protocols used, including the use of various chemicals, duration of treatment, application modality, and compliance monitoring.
On the other hand, all studies conclude a beneficial effect in terms of decreasing the risk of caries by stopping the process in esthetic and mechanical terms at the enamel tissue level. ICDAS is a system for classifying carious lesions 20  The entire thickness of the enamel is reached, the dentine is infected.
the clinical aspect of the lesion and the histological characteristics. Note: Studies report remineralization protocols for eruptive lesions. The results look promising, but the available studies do not yet allow for widespread use 25,12 Bleading Even if dental lightening treatment does not deal with the hypomineralization problem in any way, its use can be very interesting for two reasons: -At the esthetic level, the perception of these lesions can be accentuated by the contrast between the stain and the surrounding healthy enamel. Thus, the lightening helps to decrease this contrast and the visual perception of the spots; -These hypomineralization lesions do not always appear white. They can be discolored and appear yellow or brown. Histologically, this results in the presence of molecules or chromophores within the porous structure of the hypomineralized enamel. The esthetic problem is then twofold: There is the opacity and the discoloration. Lightening is, therefore, used to extract the chromophores from the lesion to make it white.
The infiltration treatment will then restore the hypomineralized opaque enamel to its translucent appearance.
Superficial treatments using thermoformed gutters and 10% carbamide peroxide gels for 3 weeks demonstrated long-term effectiveness and safety.

Infiltration
The idea of treating white spots with resin infiltration was first developed by Davila and Buonocore in 1975 13 as part of the early treatment of enamel caries, but it was not successful. It was not until the 2000s that Meyer-Lueckel and Paris 27,31,32,33,28 improved the protocols and the performance of the materials and develop a system dedicated to this new type of treatment called infiltration.
The idea of treating enamel cavities with resin infiltration is based on the following reasoning: -the white spots caused by the carious process are areas of hypomineralized enamel and are therefore present porosities; -the infiltration of these porosities with a polymerizable resin blocks the diffusion of bacterial acids and the passage of nutrients and stops the carious process.
Before being able to infiltrate these porosities, it is necessary to make the surface enamel layer permeable, which is most often hypermineralized. This permeabilization is carried out using a 15% concentrated hydrochloric acid gel during a preliminary erosion stage.
Today, a single system is currently available commercially for this indication: it is the Icon (DMG) System ® .
Beyond the biological uses, these techniques are accompanied by two additional desirable effects:        Although these techniques have been developed for the treatment of early stage carious enamel lesions, the esthetic results have prompted clinicians and researchers to broaden the scope of the indications. Because all enamel spots have porosities, it has been possible to describe specific protocols depending on the type of stain and the diagnosis 16,6,37,5,15,4 , There are now two infiltration protocols 6,3 -a simple infiltration protocol, with an exclusive chemical treatment, without the addition of a composite. This technique is reserved for lesions near the enamel surface (clinical case no. 1); -a deep infiltration protocol, which combines a mechanical and chemical treatment, and which requires the filling of an induced cavity, with a composite contribution, in a single shade without stratification (clinical case 3, Fig. 22-39).  (Fig. 22-39).

Figure 24
Loss of substance is associated with these lesions, particularly on the lateral side. Lesions are found on the 1st permanent molars. MIH is provided as a diagnosis.

Figure 32 An ethanol solution (Icon Dry ® ) is applied after
rinsing. This step makes it possible to dehydrate the periosteal areas to prepare for infiltration with a hydrophobic resin, which provided intraoperative stimulation.       Early orthodontic treatment is planned. The patient and her mother reported a relative esthetic complaint.  Two situations must be distinguished.
Spots are present before treatment (Decision Tree Fig. 43) The indication of an orthodontic treatment is suggested but spots are visible (clinical cases no. 2, 3, and 4).
In the case of early-stage carious lesions, the priority is to stop the carious process, through the management of risk factors, the control of the general practitioner, the setting up of outpatient and professional fluoridation, and the treatment of active dentin lesions, if necessary.

GUIDELINES FOR THE ORTHODONTIST
The second objective, regardless of the diagnosis, is to decrease the mechanical risk. Indeed, the hypomineralized enamel is less mechanically resistant than healthy enamel (clinical case no. 2, Figs. 14 and 15). Attaching a device directly to this area without specific pretreatment can be detrimental, especially when removing the fasteners: tearing may be at the expense of hypomineralized enamel and not within the bonding composite.
An infiltration treatment before orthodontic treatment is therefore recommended-it will not only strengthen the damaged enamel but also ensure good adhesion to the area. It has indeed been shown that the adhesion quality on hypomineralized and infiltrated enamel are the same as those on healthy enamel 29,39 In the case of deep lesions, a concavity will have been created by the deep infiltration. This concavity is repaired using the composite. Adhesion in this area can be completed using a standard composite: sandblasting, adhesive, and bonding material.
However, in young patients with deep lesions, the surface enamel stays perfectly healthy and resilient. The problem is only esthetic. In the case of orthodontic care, it is better to wait until the orthodontic treatment is completed before taking care of the esthetic problem. To remove a stain then to attach a device to the area, even a ceramic device, can be a questionable approach (clinical case no. 4  the visible spots after treatment are most likely early-stage carious lesions. A protocol to manage the carious process is therefore to be put in place, as well as a remineralization protocol. Unfortunately, as has already been mentioned, the effectiveness of these treatments is limited.
After 3 months of treatment, there is no more room for improvement.
The infiltration treatment is then indicated, associated or not with a prior lightening treatment.
The orthodontist is regularly confronted with the problem of enamel spots.
A few simple guidelines make it possible to reach the correct diagnosis in most cases.
The timing of the treatment is determined by observing the surfaces and possible substance losses at these spots.
In the case of spots detected before orthodontic treatment, the treatment is indicated before the placement of the device if the spots: -reach the surface of the enamel; -are associated with substance losses.
In other cases, their management can be carried out after orthodontic CONCLUSION treatment without decreasing the chances of a good prognosis.
Prophylaxis and prevention are fundamental to orthodontic treatment. Unfortunately, they cannot guarantee the absence of spots at the end of treatment, even in compliant patients. In the case of postorthodontic spots, management may be offered to the patient. It consists of a combination of three treatments: remineralization, bleading, and infiltration.
These are simple, reproducible, easyto-implement treatments that present a particularly favorable benefit-stability relationship. They help to secure and optimize the orthodontic treatment.