The patient and orthodontist look forward to completing orthodontic treatment with great anticipation. While the results of orthodontic treatment can be gratifying, the compromise of the surface integrity of the enamel can often mar this otherwise pleasant event and cause concern for all parties involved.

The presence of unexpected white spot lesions (WSLs) is a well-recognised issue, and much research has focused on this in recent times. In addition to WSL orthodontic scars on enamel can be seen as, staining of the teeth surfaces, a change in colour, enamel cracks or scratches, roughness, loss of gloss, excessive attrition or abrasion, and pencil marks.

WSLs are the residual effects of orthodontic appliances left behind on the teeth. They are caused by enamel decalcification around brackets as a consequence of multiband or bonded appliances. The WSL has been defined as ‘subsurface enamel porosity from carious demineralisation’ that presents itself as ‘a milky white opacity when located on smooth surfaces. ( Fig. 105.1 ).

Visible scars of orthodontic treatment.

Note decalcification on incisal edges and labial surfaces of the anterior teeth. Also, note the lead pencil marks used as guides for correct placement of the brackets during bonding. Lead pencils or any such staining marks should be avoided.

WSLs appear dull areas on enamel and lack the natural lustre, because of reduced enamel mineral content. WSL affected spot leads to increased enamel permeability and a backscatter of light from the dentin layer underneath. The difference in the refractive index between decalcified and adjacent healthy enamel defines the WSL. WSLs of orthodontic origin need to be differentiated from idiopathic white opacities of the enamel and fluorosis. A WSL is characterised by enamel surface softening, which involves preferential removal of the interprismatic substance with maximum mineral loss at the enamel surface. The subsurface lesion is marked by dissolution in the deeper part of the enamel. The lesion is covered by a porous but mineral rich layer.

The prevalence of WSLs in orthodontic patients is reportedly varied. However, it must be noted that at least 50% of orthodontic patients develop at least one or more lesions during orthodontic treatment. ^, Using conventional visual detection methods, the prevalence of at least one WSL in orthodontic patients was 49.6% compared to 24% in an untreated control group. Using advanced methods such as quantitative light-induced fluorescence (QLF) show that a significantly larger percentage of patients are affected.

Though there is an increased prevalence of WSL in both vestibular and lingual surfaces, distribution is more in the cervical and middle one-thirds of the crowns, particularly in the maxillary and mandibular molars, maxillary lateral incisors and mandibular lateral incisors and canines ( Fig. 105.2 ). Lesions are also larger in maxillary central and lateral incisors, particularly in the gingival third. Distogingival quadrants are more affected than the mucogingival quadrants.

Shows an orthodontic appliance and poor oral hygiene.

This situation alarmingly predisposes the teeth to decalcification and the formation of white spot lesions.

The risk factors for white spot lesions are tabulated in Table 105.1

The vulnerability of the orthodontic patient to WSLs is linked to the plaque harbouring nature of the orthodontic appliances. The presence of fixed appliances in the mouth leads to an increase in plaque volume of a different composition, with high concentration of cariogenic bacteria and a subsequent reduction in pH of plaque. ^,

The biofilm that surrounds the tooth/teeth is a dynamic entity that is an aggregate of numerous microorganisms in a state of equilibrium with the enamel and oral fluids. The salivary pellicle is adherent in nature, where cells adhere to one another and to a surface, and tends to attract cariogenic bacteria. Streptococcus mutans are the first to colonise the plaque. The mucilaginous pellicle, which demonstrates increased adherence, attracts other free-floating bacteria from saliva. The cariogenic microorganisms in the presence of fermentable carbohydrates produce organic acids that lower the pH in the plaque, thereby causing a diffusion of calcium and phosphate ions from the enamel through the pellicle and into the plaque fluid. This process continues as the pH of plaque further decreases.

With progressive colonisation in the biofilm, the composition of the microflora shifts to gram-negative bacteria, increasing the susceptibility of the orthodontic patient not merely to decalcification but also to gingivitis and progressive periodontal disease.

Development of white spots has been reported to occur within 4 weeks of initiating fixed appliance therapy. The demineralised enamel is more susceptible to taking up the stain and appears unsightly. If not prevented in the initial stages, it could lead to further cavitation, which cannot be reversed. However, with improved oral hygiene and other preventive measures, when the pH of oral fluids returns to normal, calcium and phosphate ions in the saliva move through the pellicle into the enamel, following the laws of chemical equilibrium and facilitating remineralisation.

Any enamel opacities or enamel spots should be recorded before the initiation of orthodontic treatment and should be an integral part of intraoral clinical examination protocol. The enamel spots and lesions should again be evaluated immediately after the completion of the treatment and debond. A simple index was proposed by Gorelick et al. ( Fig. 105.3 ) which can be used in four zones around the bracket ( Fig. 105.4 A). Enamel decalcification can be recorded in 4 zones on crown enamel. Each zone is further divided in to 2 micro zones, thus a total of 8 zones on a tooth ( Fig. 105.4 B).

A simple index used for white spot lesion (WSL).

Based on the concept of Gorelick L, Geiger AM, Gwinnett AJ. Incidence of white spot formation after bonding and banding. Am J Orthod 1982;81(2): 93–8. doi:10.1016/0002-9416(82)90032-x. PubMed PMID: 6758594.

(A) Modified index to assess the white spot lesion (WSL) in four zones. (B) The four zones each can be further divided into two micro zones.

Based on the concept and works of Srivastav S, Duggal R, Samrit VD, and Kharbanda OP. An innovative tool for assessment of White Spot Lesion. An exploratory study Poster. August 2021 DOI: 10.13140/RG.2.2.21166.02882

Clinically, visual detection is quite satisfactorily performed by the discerning clinician and has significant validity as this is what would also be visible to the patient although photography has also been employed. Research demonstrates the use of optical non-fluorescent and optical fluorescent methods to detect WSLs. In particular, QLF has proved to be a reliable and objective method that allows early detection and evaluation of mineral loss and changes in the size of the lesions over time.

Maintenance of good oral hygiene is paramount in the orthodontic patient. It is now known that the presence of fluoride ions in the fluid phase of caries (the biofilm) goes a long way in the prevention of demineralisation and contribution to the process of remineralisation.

Application of topical fluoride leads to a reservoir of CaF ₂ in plaque, which acts as a source of fluoride ions for release when there is a carious attack. However, the protective effects of fluoride become questionable when the pH is lowered due to poor oral hygiene maintenance. Arneberg demonstrated different pH of plaque at various sites in the oral cavity. The pH of the plaque in the area of upper incisors was the lowest, which could be attributed to poor salivary clearance. The plaque with lower pH demonstrates less availability of fluoride ions, and the efficacy of fluoride alone, in the absence of good oral hygiene, is questionable. Thus, patient cooperation in the maintenance of oral hygiene is, therefore, critical for active efficacy of fluoride.

Toothpaste contains fluorides in various forms such as sodium fluoride, monofluorophosphate, stannous fluoride or amine fluoride. A local dose of at least more than 0.1% fluoride is recommended for orthodontic patients. However, a few studies have shown that toothpaste alone is inadequate for effective prevention. It is recommended that all orthodontic patients should use additional fluoride mouthwash in the concentration of 0.05% NaF in addition to using a fluoridated toothpaste.

For patients who are at high risk of WSL and those who are uncooperative in the maintenance of oral hygiene, additional professional application of fluoride varnishes is recommended. A single application of varnish is not effective in preventing WSL and should be repeated at each appointment. Fluoride varnish has shown therapeutic benefits even in the presence of plaque. ^, Other additional options of fluoride delivery are fluoride incorporated into chewing gums and elastomeric ligatures.

The use of antimicrobials alone or in addition to fluoride is another attempt to modify the biofilm. One potent antimicrobial agent is chlorhexidine, which is a positive charged molecule that binds to negative charged sites on bacterial cell walls. Chlorhexidine can damage microbial cell walls within 20 s, permeate the cell and attack the cytoplasmic membrane, leading to cell death. Though chlorhexidine is effective in bacterial control for 48 h post use, its effect on the reduction of WSLs is questionable. An additional disadvantage of chlorhexidine is its tendency to stain composite and glass ionomer. In general, antibiotics and antimicrobials as mouth washes though capable of suppressing caries infection can never eliminate it and need to be given long term for useful results.

Probiotics, which are live microbial feed consumed in the diet or applied locally in dentifrices, have proved to be effective against cariogenic bacteria in orthodontic patients. A recent systematic review, however, failed to demonstrate their beneficial effect on enamel remineralisation and suggested that more research is needed to reach a consensus on strains, dosage, regimen and modes of administration.

Xylitol, a polyol carbohydrate, is not metabolised by S. mutans and is, therefore, non-cariogenic. When incorporated in chewing gum, it has demonstrated increased stimulated saliva with increased concentrations of phosphates and calcium than non-stimulated saliva.

The use of glass ionomers or resin-modified glass ionomer cements (RMGICs) should be considered in patients with a high risk of WSLs as these would provide the advantage of fluoride and can be used without the damage caused by enamel etching.

The methods of preventing and management of early WSL during orthodontic treatment are provided in Table 105.2 .

Nanoparticles present a greater surface to volume ratio (per unit mass) and thus interact better with microbial membranes and provide a considerably larger surface area for antimicrobial activity. ^,

Most used inorganic nanomaterials are metals such as Au, Ag or Cu or metal oxides such as TiO ₂ , CuO or ZnO. TiO ₂ has been studied extensively because of its photocatalytic activities by the production of free radicals by exposure to ultraviolet light and visible light. In recent times, ZnO nanoparticles have also been extensively studied because of their efficacy and biocompatibility.

Nanomaterials have been used to coat the surface of orthodontic appliances such as brackets, wires, implants retainers and even aligners and found to be effective in reducing the concentration of cariogenic and other microorganisms. Fluoride, whose anticariogenic properties are well established, has also been studied in the nanoparticle form with promising results, as have other organic nanoparticles. However, most of these studies are in vitro, and although a few in vivo studies have demonstrated their efficacy, nano surface coatings are yet to be used in routine clinical applications.

Nanoparticles of Ag, ZnO ₂ and TiO ₂ have also been incorporated into orthodontic adhesives, composites, resin-modified glass ionomers, cements and resins for bonding. They have been incorporated into polymethyl methacrylate (PMMA) that is used to make orthodontic appliances and retainers. Some of these composites and cements are available commercially and have demonstrated to have a comparable bond strength to conventional counterparts but have the additional advantage of better aesthetics, smoother finish and reduced plaque adherence and when incorporated into resins have demonstrated an inhibitory effect on the microflora. Moradpoor et al. in their review highlighted the role of various nanoparticles in orthodontics, including their antimicrobial activities.

The orthodontist, in addition to attempting prevention of WSLs, also has to grapple with the reversal or treatment of these WSLs.

Management would depend on the severity of the WSLs. Gorelick and co-workers classified WSLs as follows:

• 1.

  No white spot formation

• 2.

  Slight white spot formation (thin rim)

• 3.

  Excessive white spot formation (thicker bands) ( Fig. 105.5 )

  

  Moderate white spot lesions (WSLs) on canines and premolars in the maxillary arch.

• 4.

  White spot formation with cavitations ( Fig. 105.6 )

  

  Severe forms of white spot lesions (WSLs) leading to cavitation.

Remineralisation is a possibility for milder forms of WSLs which are likely to become less noticeable over a period of a year or so because of the natural remineralisation that takes place due to the calcium and phosphates and other trace elements present in the saliva. Though the use of high concentration of fluorides arrests the caries process, Ogaard and co-workers have cautioned against this as this arrests both demineralisation and remineralisation by surface hypermineralisation and blocks the diffusion pathways of the enamel. This is particularly relevant for anterior teeth since it might compromise the colour of the lesion permanently.

Instead, they advocate natural remineralisation, which results in better repair and a less visible lesion. If high doses of fluoride are used locally, the arrested lesion stays the same size and frequently becomes stained. Natural remineralisation and low-dose fluoride, such as in toothpaste and mouthwashes, seem to be a cost-effective and practical solution for smaller lesions and are the basic standard of care.

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), a product of milk casein, has demonstrated effective remineralisation due to its absorption through the enamel surface. The freely available calcium and phosphate ions move from the CPP-ACP into the enamel rods and reform as apatite crystals. CPP-ACP, which can be dispensed in various forms such as mousse, topical creams, chewing gum, mouth rinses and sugar-free lozenges, appears to help although its efficacy has been viewed with cautious optimism.

Bioactive glass ceramic materials such as BioMin F (Bio-BAG) and Novamin (N-BAG) composed of calcium, phosphorous, sodium and silica have been proved to be successful in preventing and help to remineralise the WSLs. The calcium sodium phosphosilicate particles coming in contact with oral fluids release calcium and phosphate ions, forming a calcium phosphate layer, which then crystallises into hydroxycarbonate apatite, leading to enamel remineralisation. The bioactive glass paste also increases the pH, thereby inhibiting bacterial flora. Bioactive glass shows promise in remineralising WSLs and can also be incorporated into tooth pastes and into orthodontic bonding systems to prevent demineralisation.

Vital tooth bleaching with hydrogen peroxide or carbamide peroxide increases the whiteness of the surrounding enamel to match with that of the WSL, thus camouflaging the WSL without affecting its size or depth. Although bleaching does not address the integrity of the WSL, it is a non-invasive procedure that patients may find acceptable since it lightens the shade of the teeth.

Microabrasion is a technique, which involves using a slurry of pumice or silicon carbide particles and hydrochloric acid to create surface dissolution of enamel and has been demonstrated to be effective over the short term in removing superficial stains or defects which do not exceed 0.2–0.3 mm in depth.

Resin infiltration is a relatively new technique, which is based on the porous nature of demineralised enamel to allow a low-viscosity resin to permeate into the enamel matrix after etching it with 15% HCl and fill in the voids previously filled with air or water. Resin infiltration produces a refractory index comparable to healthy enamel, and there is some evidence that it is effective in masking post-orthodontic WSLs. ^,

Restorations: Patients with cavitated lesions or more severe WSL who have already attempted more conservative aesthetic treatments without significant improvement may have to resort to restorations ( Table 105.3 ).

TABLE 105.3

Management of white spot lesions after orthodontic treatment

Mild WSLs	Moderate to severe WSLs
Natural remineralisation	Bleaching
Low concentration fluorides as tooth paste and mouth wash	Microabrasion
Xylitol chewing gum	Resin infiltration
CPP-ACP as tooth mousse	Restorations (direct or indirect)
Bioactive glass as Novamine

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