Author : Dr Dubey Rachna,


Abstract :

Enamel demineralization is one of the most common complications of fixed appliance therapy. The prevalence of this phenomenon has been reported to be very high, jeopardizing the success of orthodontic treatment outcome. It becomes mandatory for orthodontist to recognize the high risk patients, evaluate the white spot lesions, reinforce good oral hygiene measures, institute preventive fluoride regimen and manage post treatment white spot lesions to obtain optimum esthetic results.

Despite the advances in orthodontic materials & techniques in recent years, the development of enamel demineralization around the brackets remains the most undesirable and common complication of fixed appliance therapy. White spots that appear on teeth are areas of decalcified enamel and sometimes this may lead to deterioration of teeth. The overall prevalence amongst orthodontic patient’s ranges from 2-96%^1-3.Gorelick et al ² and others ^4,5,6 found that nearly 50% of orthodontic patient’s exhibit clinically visible white spot lesions (WSL) .The highest incidence was in the maxillary incisors, particularly the laterals. These WSL are due to demineralization of the enamel by organic acids produced by cariogenic bacteria⁷. Orthodontic appliances make brushing and flossing difficult and increase the surface area available for accumulation of plaque and food particles.

Demineralization around brackets can be an extremely rapid process ^2,6-10with visible WSL developing within four weeks after bonding. They appear most frequently on the cervical and middle third of the buccal surfaces of mandibular incisors, canines and first premolars.Artun and Thystrup found that removal of the cariogenic challenge after debonding results in arrest of further demineralization and a gradual regression of the lesion at the clinical level takes place primarily because of surface abrasion with some redeposition of minerals. There are macroscopic and microscopic methods used in the detection and measurement of WSL. ¹² However Ogaurd et al ¹³ observed that remineralization of surface softened enamel (such as under a loose band or bracket from one visit to another) and subsurface lesion are completely different process. The surface softened lesion remineralize slowly, probably because of lesion arrest by widespread use of fluoride.

Progression

When dental plaque lies on the surface of a tooth the acid waste products created by the bactereria that live in the plaque etch away some of the mineral content contained in the tooth’s enamel. As more and more mineral content is leeched out of the enamel its appearance becomes changed. The enamel starts to take on an opaque white appearance. This is termed as white spot lesion. There are non cavited carious lesions in enamel. These may be actively demineralizing, remineralizing or arrested. If demineralization continues, White spot lesion can progress through the enamel into the dentine. The appearance changes to a soft brown or black as cavitations occurs. Once in dentine, dentine caries progress more rapidly, eventually reaching the pulp of the tooth. Formation of an abscess, an infection at the apex of the root of the tooth may occur. In some cases the abscess forms a fistula near the site of infection. On the other hand if the tooth surface is kept plaque free, the cavity formation process can be halted. But since the mineral content of the enamel has already been altered its color will remain bright white.

Characteristics : White spot lesions are spots on the enamel that are whiter than normal. These are often found along the gum line of the upper front teeth in young children. These are non cavitated carious lesion in enamel.

Causes: 1-Nutrition 2-Genetics 3-Excessive intake of fluoride 4-After orthodontic treatment 5-Ineffective home oral hygiene practices etc.
Evaluation of WSL:
1 Macroscopic method:
a. Clinical examination: It is often difficult to distinguish white spots caused by demineralization and those that are due to other causes such as developmental hypoplasia or fluorosis. Non-fluoride opacities have a more defined shape, often located in the middle of the tooth and randomly distributed when compared to fluorotic lesions which are not well defined and have symmetrical distribution.¹³

b. Photographic examination:

Photographic techniques provide permanent record, can be digitized and are used extensively to assess the demineralization before, during and after treatment.¹⁴

c. Optical Non-fluorescent methods:

Demineralized enamel scatters light. A 100W white light can be used and the back-scatter can be measured with a densitometer or Optical Caries Monitor (OCM) described by the Ten Bosch etal.¹⁵

d. Optical fluorescent methods: De Josselin de Jong et al developed the technique of quantitative laser fluorescence for use in the mouth. Another method using laser fluorescence is an instrument called DIAGNODent (KaVo, Germany).The most promising fluorescent method of measuring demineralization in use today is QLF (Quantitative Light Induced Fluorescence) which makes use of a small portable system for intraoral use with a new light source & filter system.¹⁶

2. Microscopic Methods:

a. Caries Models:

Orthodontic caries models have usually involved placing a band or a bracket on the tooth that is destined for extraction. Following a period in the mouth, tooth is extracted and subjected to microhardness testing, polarized light microscopy or microradiograph.¹⁷

b. The In Situ Caries Model :

Enamel can be placed in a removable appliance/bonded to the tooth of a volunteer or placed in a specially designed holder attached to the orthodontic archwire. ¹⁸

Risk Factors:

Important risk factors for enamel demineralization include the patient’s oral hygiene, diet, individual salivary flow & excess or failed bonding cement around the bracket or band.

The risk factors are summarized in Table 1 ¹⁹.

Table 1: Risk factors for enamel demineralization

Prevention of Enamel demineralization


The risk of enamel demineralization during treatment can be prevented by either eliminating the plaque deposition on the enamel surface or by enhancing the enamel resistance to the microbial attacks using topical fluorides.
Prevention measures to minimize damage include: patient selection, intensive oral hygiene instruction, regular monitoring, dietary education and enhancing the enamel resistance to decalcification.

Patient Selection:

For patients with high risk of caries, orthodontic treatment should be delayed. For patients with a history of caries, treatment should be initiated only when they have been assessed over a period of time as having a good dental health, and excellent oral hygiene habits. A period of 3 months of sustained good oral hygiene is probably sufficient to evaluate a patient’s ability to confirm to meticulous oral hygiene regimen.¹⁹

Intensive Oral Hygiene Instructions:

Patients wearing fixed appliances might benefit from the use of an electric tooth brush. Sonic frequency devices such as Flex care by Sonicare have been shown to be effective while not compromising bracket bond strength.²⁰

Patients should be instructed to use the tongue cleaner at least once a day & combine it with volatile sulfur compound (vsc) neutralizing sprays to prevent staining chromogens from depositing on the teeth and / or around orthodontic brackets / bands. Mechanical flosses, interdental brushes and oral irrigators used at a higher setting are recommended.

Diet Counseling:

Before treatment, a diet counseling session, including a 5 day detailed diet record, is recommended, particularly for patients with a history of caries. 19 Bach showed an increase in decalcification following orthodontic treatment of 4.7% & 6.0% in persons with minimum & excessive carbohydrates consumption respectively.21 Patients should be advised to avoid sugar containing foods and drinks.

Regular Monitoring:

At each visit, oral hygiene and dietary education should be reinforced. Inspection of labial surface of the teeth at each appointment will identify the cases that require more intervention. If poor oral hygiene persists, the orthodontic attachments should be removed and treatment discontinued until effective oral hygiene practices are demonstrated over time.¹⁹

Enhancing The Enamel Resistance To Decalcification:

Fluoride ions prevent plaque activity and adhesion by blocking enzyme systems, reducing enamel demineralization and promoting remineralization. Therefore it is used as a principal ingredient for preventing enamel decalcification.

1. Fluoride Mouth rinses:

A Cochrane review has recommended that orthodontic patients who are at risk of caries should use a 0.05% sodium fluoride (NaF) rinse daily during treatment, in addition to fluoridated toothpaste.22 Weekly use of 1.2% acidulated phosphate fluoride (APF) rinse has been found to reduce incidence of enamel demineralization during orthodontic treatment.9, These mouth rinses have been combined with antibacterial agents like chlorhexidine, triclosan, or zinc to improve their cariostatic effect.¹³

2. Fluoride Gels:

Many investigations have tried 0.4% stannous fluoride gels (SnF2) during orthodontic treatment and reported decreased enamel decalcification. Boyd compared the use of a 1100 ppm fluoride tooth paste alone or together with either a daily 0.05% NaF rinse or 0.4% SnF2 gel applied twice daily by tooth brush. He found that both provided additional protection against decalcification when compared to toothpaste alone, but neither was superior.

3. Fluoride Dentifrices:

As orthodontic patients are at an increased caries risk, a fluoride concentration below 0.1% in dentifrices is not recommended.
Stookey²³ recommended that tooth pastes containing NaF are most effective against white spot development. On contrary Ogaard et al recommended combined use of an AmF/SnF2 toothpaste / mouth rinse daily during treatment. This combination had more inhibiting effect on white spot lesion development when compared with NaF products.

SnF₂ has a plaque inhibiting effect by interfering with the adsorption of plaque bacteria to the enamel surface. Tin atoms in stannous products also block the passage of sucrose into bacterial cells, thus inhibiting acid production. The use of fluoridated antiplaque dentifrice may reduce enamel demineralization around the brackets more than the use of a fluoridated dentifrice alone.

4. Fluoride Varnish:

Many studies have found that fluoride varnishes are effective in preventing enamel demineralization.24 it has been reported that the application of a fluoride varnish resulted in 44.3% reduction in enamel demineralization in orthodontic patients while eliminating the need for patient cooperation that is required with fluoride rinses.

5. Fluoride containing sealants & primers:

The use of fluoride containing sealants did not affect the shear bond strength (SBS) of orthodontic adhesives but were shown to a decrease release of fluoride ions with time. Proseal, a fluoride releasing sealant was capable of releasing fluoride ions for 17 weeks.25 However; it has the ability to be recharged with fluoride ions using a foaming solution of APF; fluoride release in the first week after recharging increased to 0.354 ppm/mm2. While these rates of fluoride release may be low, Ten Cate suggested that even sub-ppm levels of fluoride may have a significant impact on remineralization.

6. Luting Cement:

Fluoride releasing cements like zinc polycarboxylate & resin modified GIC demonstrated less enamel decalcification than the traditional zinc phosphate cements.²⁶

7. Fluoride in Bonding Agents:

Bonding agents containing fluoride have the potential for decreasing enamel decalcification. Glass ionomer cements have lower SBS than RMGIC and their use for bonding orthodontic brackets became fairly limited.²⁷ Because of recent improvements in the fluoride-releasing capabilities and the SBS of RMGIC, it has been suggested that these adhesives should play a greater role in bonding brackets in the future.

8. Antimicrobials in Orthodontic Adhesives:

Combining chlorhexidine with the bonding primer or applying it after bonding is completed, resulted in no significant decrease in SBS. ²⁸ But application of chlorhexidine as a separate varnish layer during bonding, either alone or as a separate layer over the sealant before placing adhesive, resulted in significant reduction in SBS . ²⁸The use of cetyl pyridinium chloride (CPC) found no significant differences in tensile bond strength between an adhesive impregnated with 2.5% CTC & a control. Moreover, the adhesive containing 2.5% CTC was shown to inhibit bacterial growth for196 days.

9. Fluoride containing Etchants:

The topical application of fluoride has been reported to decrease the bracket bond strength.²⁹ In contrast; a study by Takashashi et al reported that the application of 30% H₃Po₄ solution containing 0.02%NaF resulted in an increase in the fluoride content in the enamel surface without decreasing the bond strength. Other studies have indicated that a mixture of 37% phosphoric acid and an APF gel (50% and 66% fraction) would be used as an etchant to minimize the loss of sound enamel.

10. Fluorides in Elastomers:

Many investigations suggested that fluoride releasing modules were effective in reducing enamel decalcification around the brackets. Other studies concluded that short term fluoride release from these accessories did not affect the quantity of disclosed plaque around orthodontic brackets.³⁰ In the presence of fluoridated toothpaste & mouth rinses they imbibe the fluoride and release it significantly more.

11. Laser Irradiation:

Several authors have suggested that argon laser alters the crystalline structure of the enamel and prevents enamel decalcification.31 Blankenau et al31 for first time found an average of 29.1% reduction in depth of enamel decalcification with argon laser irradiation followed by many other studies. Harazaki et al subjected 10 orthodontic patients to a combination of Nd-YAG and APF treatment. These patients showed less number of WSL than control group.
Routine fluoride application procedures used for all patients receiving fixed appliance therapy at the Oslo University Dept of Orthodontics.
(Fluoride content of drinking water below 0.10 ppm).
I) Before Insertion of Fixed Appliances:
1. APF gel treatment (associated with impression taking) and
2. Daily mouth rinsing with 0.05% NaF (caries prone patients should rinse twice daily).
II) Throughout Period of Active Treatment:
Daily rinsing with 0.05% NaF (caries prone patients should rinse twice daily).
III) After Removal of fixed Appliances:
a) Routine Patients: Daily rinsing with 0.05% NaF.
b) Patients having received demineralization during treatment
c) Enamel fracture during debonding may occur because of the high bond strength, especially of ceramic brackets.Ghafori reviewed previous findings and suggested solutions to various clinical problems. This review concluded that ceramic brackets should be used selectively after careful evaluation of the individual malocclusion and the patient may be informed of the possible side effects of debonding.
Daily rinsing with 0.2% NaF for 2-4 months followed by daily rinsing with 0.05% NaF.
In addition to fluoride mouthrinses all patients should use a fluoride dentifrice throughout treatment period.

MANAGEMENT:

Demineralized enamel can remineralize after debonding under favorable conditions.^6,8,10, 11 Remineralization of these WSL is a natural phenomenon resulting in the partial reversal of what is an early caries lesion. Mellberg et Sal have shown an average remineralization of 20-30% over 2 weeks. Ogaard etal¹⁰, warned against treating visible white spot lesions on labial surfaces with concentrated fluoride agents as this arrests the lesion (hyper mineralization). Instead they advocated allowing remineralization by saliva, as this result in greater repair and less visible lesion. Lagerweij and Ten Cate found that fluoride toothpaste combined with a high concentration of fluoride gel (12,500 ppm) resulted in more remineralized lesion when compared with the use of only a fluoride tooth paste.
Use of Casein Phosphopeptide Amorphous Calcium phosphate: (CPP-ACP)
In 1980’s, Reynolds drew attention to the fact that CPP-ACP, which is a product derived from milk casein was capable of absorbing through enamel surface & could affect the carious process.³² The CPP-ACP is a delivering system that allows freely available calcium and phosphate ions to attach to enamel & reform into calcium phosphate crystals. The material is marketed under the trade name “Recaldent”. Studies of the effects of CCP-ACP have shown promising dose related increase in enamel remineralization within already Demineralized lesions.

Chewing gum To Promote Remineralization

In nonorthodontic patients, a regimen using a sorbitol-based chewing gum chewed for 20 minutes, 5 times daily for 3 weeks, showed significant remineralization of demineralized enamel when compared with controls without chewing gum. The use of xylitol as an alternative sweetener may be superior when compared with sorbitol because of the potential anticaries properties.33 Beneficial effect seen with the use of chewing gum are attributable to a large measure to salivary stimulation.

Vital tooth bleaching:

If time and fluoride do not improve the esthetic concerns of the patients and clinician, post orthodontic bleaching can be beneficial. Mild whitened enamel can often be camouflaged by bleaching with standard tray-based whitening systems used over night or with hydrogen-peroxide impregnated polyethylene strips.³⁴ If 2 to 4 weeks bleaching with these regimens is ineffective at camouflaging this whitened enamel, microabrasion followed by bleaching is recommended.

Dental fillings: One another cosmetic solution for white spot lesions is to place white fillings in those areas.

Crown and veneers: one difficulty with the white filling approach is that there seems to be variation in the coloration of this person’s teeth in different regions. It may be difficult for the dentist to place white filling that match well. If this is the case, the dentist and patient might decide that a better approach is to place porcelain veneers, since they cover over and uniformly change the appearance of the entire front side of the tooth. If there is a good bit of breakdown on a molar, a crown may be needed.

Instructions for patient: Keep your teeth Clean. Brush with a fluoridated tooth paste and floss thoroughly after each meal. Use special floss threader to use around your braces. After your brush and floss, look at your teeth carefully for any missed food particles. In addition use a fluoride rinse at night before you go to bed. Try not to eat acidic foods or sugary snacks very often. Acidic foods, in addition to carbonated soft drinks, sugars, sticky food and candies will add damage to your tooth.

Microabrasion:

Microabrasion has been shown as an effective treatment approach for the cosmetic improvement of long-standing post orthodontic demineralized enamel lesions.³⁵This procedure should be delayed atleast 3 months following debonding to allow for spontaneous improvement of the lesion & remineralization with fluoride applications.

Clinical procedure-A custom made abrasive gel is prepared with 18% Hydrochloric acid, fine powdered pumice and glycerine.The active mixture is applied as follows

1-The gingival is isolated using block out resin or rubber dam. Dental floss may be useful to prevent soft tissue contact and injury from the acid.

2-The abrasive gel is applied using an electric toothbrush for 3 to5 minutes. The original toothbrush tip is modified by cutting the peripheral bristles to create a smaller brush tip to fit on tooth surface better.

3-Rinse for 1 minute to prevent enamel pitting, the acid should not be left on the tooth for an extended time for best results and depending on the severity of the lesions, the procedure can be repeated monthly 2 to3 times. This makes stains disappears gradually.

The microabrasion technique is effective in removing white spots and streaks and brown yellow enamel discoloration, grinding with diamond burs under water cooling or composite restorations are inevitable.

CONCLUSION

Though many revolutionary changes in techniques & materials have marked the history of orthodontics since the time of introduction of fixed orthodontic appliances, post-orthodontic enamel demineralization unfortunately persists to be undesirable & common complication. In the light of available evidence regarding the etiology of demineralization during fixed appliance therapy, the best preventive strategy would appear to be an assessment of risk factors prior to bonding, coupled with fluoride mouth rinses, reinforcement of oral hygiene and dietary advice throughout the course of treatment.

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