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ORIGINAL ARTICLE
Year : 2020  |  Volume : 23  |  Issue : 9  |  Page : 1312-1317

Investigation of the esthetic outcomes of white spot lesion treatments


1 Department of Developmental Dentistry, School of Dentistry, University of Texas Health San Antonio, Texas, USA
2 Department of Restorative Dentistry, Faculty of Dentistry, College of Medicine, University of Nigeria, Enugu, Nigeria
3 Department of Comprehensive Dentistry, School of Dentistry, University of Texas Health San Antonio, Texas, USA

Date of Submission08-Mar-2020
Date of Acceptance28-May-2020
Date of Web Publication10-Sep-2020

Correspondence Address:
Dr. L O Okoye
Department of Restorative Dentistry, Faculty of Dentistry, College of Medicine, University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_119_20

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   Abstract 


Objective: The present study compared the ability of bleaching, resin infiltration and microabrasion to restore the appearance of existing white spot lesions (WSL) on tooth surfaces as close as possible to that of the original healthy enamel. Materials and Methods: Sixty extracted human teeth with WSL were randomly assigned to three treatment groups (20/group). Prior to treatment, the colour of the surrounding healthy enamel and the WSL were measured as the baseline and pre-treatment (PreRX) colours respectively using spectrophotometer based on CIE L*A*B. The L-value was used for the statistical comparison. WSLs in each group were treated respectively by bleaching, infiltration or microabrasion following the manufacturer's instructions. Colour measurement was repeated after treatment. Both intragroup and intergroup comparisons were performed using ANOVA followed by Tukey's multiple comparison test (α=0.05). Result: In all groups the mean L-values were significantly higher in PreRX WSL (P < 0.01; Tukey) compared to baseline (sound enamel). After treatment the difference in mean L-value between baseline and WSL increased significantly (P < 0.01, Tukey) in Bleaching and Microabrasion groups by 1.4% and 1% respectively, but decreased in Infiltration group by 3.4%. Thus resin infiltration decreased the L-value of the WSL, bringing it closer to the L-value of the sound enamel while bleaching and microabrasion increased the L-value. Conclusions: Among the three treatment modalities investigated in this study, resin infiltration was the most effective in masking the WSLs.

Keywords: Bleaching, microabrasion, resin infiltration, spectrophotometer, white spot lesion


How to cite this article:
Lee J, Okoye L O, Lima P P, Gakunga P T, Amaechi B T. Investigation of the esthetic outcomes of white spot lesion treatments. Niger J Clin Pract 2020;23:1312-7

How to cite this URL:
Lee J, Okoye L O, Lima P P, Gakunga P T, Amaechi B T. Investigation of the esthetic outcomes of white spot lesion treatments. Niger J Clin Pract [serial online] 2020 [cited 2020 Sep 24];23:1312-7. Available from: http://www.njcponline.com/text.asp?2020/23/9/1312/294673




   Introduction Top


Patients often seek orthodontic treatment for esthetic reasons. During orthodontic treatment, patients are often placed at risk of enamel demineralization adjacent to the orthodontic appliances due to poor oral hygiene with retained plaque. Acidogenic bacteria such as Streptococcus mutans that are harbored in dental plaque metabolize fermentable carbohydrates in our diet, and their byproducts of organic acids cause demineralization of tooth enamel, which manifests as white spot lesion (noncavitated caries lesion). If the white spot lesion (WSL) remains untreated, it may progress to cavitated caries lesion.[1],[2] Clinically, formation of WSL around orthodontic appliances can occur within 4 weeks into orthodontic treatment, and prevalence among orthodontic patients ranges from 2%–96%.[1]

The ideal solution to WSL is prevention of formation of the lesions in the first place. Prevention of WSLs begins by implementing a good oral hygiene regimen including proper and frequent tooth brushing technique along with use of a ffluoridated dentifrice.[3],[4] Additional sources of ffluoride such as mouth rinses, gels or varnishes may be beneficial for those patients at high caries risk and should be considered by the clinician as part of the oral hygiene and preventive regimen.[4],[5] The use of ffluoride slows down the caries process and increases the rate of remineralization of WSLs.[2] Other prevention modalities against WSLs formation include the use of surface sealants, particularly the antimicrobial and/or fluoride-releasing sealants.[6],[7] Surface sealants offer physical barrier against acid demineralization of tooth surface; however, the antimicrobial sealant has the additional benefit of preventing plaque formation.[6],[7]

Despite efforts to prevent WSLs, a number of patients still require treatment for WSLs after orthodontic treatment.[8],[9] The conventional approach for treating WSLs is restorative treatment; however, this technique has the disadvantage of being invasive.[10] Current noninvasive treatment options include lesion remineralization using fluoride varnish,[11] tooth-whitening (bleaching),[12] microabrasion,[13] resin infiltration,[14] or in combination.[15] Fluoride varnish has been reported to cause 44.3% reduction in enamel demineralization in orthodontic patients,[3] while bleaching has successfully camouflaged WSLs.[12],[16],[17] Caries lesion infiltration with resin has been claimed to mask WSLs and restore enamel surface to its original appearance.[14],[15] Microabrasion improves esthetics by physical removal of the discolored enamel resulting in a smooth and lustrous surface sheen.[13]

Presently, there is no known quantitative study that compared the ability of these WSL treatment modalities to restore the appearance of white spot lesion to that of the original healthy enamel. Therefore, the main objective of the presentin vitro study was to compare the ability of microabrasion, bleaching, and resin infiltration to restore the appearance of existing WSLs on tooth surface as close as possible to that of the original healthy enamel. The most effective method is the technique that will restore the white spot lesion most closely to the color of the healthy immediate surrounding enamel. We hypothesized that among the tested treatment modalities, bleaching will restore white spot area most closely to the appearance of the original healthy enamel as measured by Spectrophotometer.


   Materials and Methods Top


Teeth preparation and experimental grouping

Extracted human maxillary incisor teeth were collected from various clinics of the school of dentistry of the University of Texas Health San Antonio (UTHSA), and were stored in 0.1% thymol solution prior to use. Maxillary incisors were chosen because the Spectrophotometer (5 mm diameter) used for color measurement requires flat enamel surface, thus canines and premolars were not suitable. Only teeth with WSLs were selected and cleaned of debris and stains. The selected teeth were sterilized in an autoclave. Following sterilization, the teeth were randomly assigned to three treatment groups (20 teeth/group). A three-sided die was used to determine which treatment group a selected tooth should be assigned. To be included in the study, tooth should have a preexisting WSL with a minimum size of at least 1 mm × 1 mm (or 1 mm diameter). Approval of the Institutional Review Board of University of Texas Health San Antonio was obtained (IRB Approval #: HSC20080233N) was obtained on April 3, 2019.

Pretreatment color measurement

Prior to any treatment, the color of each tooth was measured at two points as follows. (1) Measurement of the color of the sound enamel surface area adjacent to the WSL. This color served as the baseline shade of the tooth enamel prior to white spot development. This is the reference against which all posttreatment data were compared for closeness. (2) Measurement of the color of the WSL on the selected tooth. The tooth surface color was assessed using a ShadeEye Spectrophotometer (Shofu Inc., Japan) in Analyze Mode.[18] Prior to taking readings, the spectrophotometer was calibrated using a “Standard” provided by the manufacturer. The sensor was placed directly in contact with the tooth surface for each reading. Three readings were taken on each tooth surface, and each reading was taken twice to confirm the same value and to ensure accuracy. Samples were dried with absorbent paper, and not desiccated, before reading. For WSLs, reading was taken at the center of the lesion. The measurement system used to measure color in this study was CIE L*A*B.[17] The L-value corresponds to the degree of lightness in the Munsell system, whereas the a-values and the b-values give the position on red or green (+a = red, -a = green) and yellow or blue (+b = yellow, -b = blue) axes. During shade measurement, the Spectrophotometer described the tooth shade with three values, Hue, Value, and Chroma. Value is the most important characteristic of shade.[17],[19] In our study, we measured the L-value of each tooth, which represents the Value component in shade description.

Treatment procedures

Bleaching group: A bleaching gel containing 10% carbamide peroxide with potassium nitrate and fluoride (Ultradent Inc., Jordan, Utah, USA) was used. Each tooth was bleached for 8 h per day for 14 days in accordance with the manufacturer's instruction. A thin layer of less than 1 mm in thickness of the bleaching gel was applied to the WSL and the surrounding healthy enamel where baseline reading was taken.

Infiltration group: Resin infiltration of each WSL was carried out using Icon™ (DMG, New Jersey, USA) as follows. Icon-Etch (15% HCL) was applied on the WSL for 2 min. Tooth was rinsed with water for 30 s and dried. Then, Icon Dry (95% ethanol) was applied onto the WSL for 30 s and dried with oil-free and water-free air. This was followed with applying the Icon-Infiltrant on the WSL for 3 min and light-cured for 40 s. A second layer of the Icon-Infiltrant was placed for 1 min and light cured for 40 s.

Microabrasion group: Microabrasion was performed using Opalustre Enamel Microabrasion Slurry (Ultradent Inc., Jordan, Utah, USA), and following the manufacturer's instructions as follows. Approximately 1.0 mm thick layer of Opalustre was applied over the WSL. Using a rubber prophy cup at rotation speed of approximately 500 RPM, the tooth surface was polished using medium to heavy pressure for 60 s at a time. The tooth surface was then rinsed. The procedure was repeated twice.

Following each treatment, the color measurements were repeated as described at the pretreatment stage, and were taken at the same two sites that were measured at pretreatment, i.e., sound enamel surface adjacent to the WSL and the center of the WSL.

Data was analyzed statistically using SPSS (version 14.0, Chicago Illinois) with the level of significance (α) prechosen at 0.05. Both intragroup time points (Baseline, Pretreatment and posttreatment) comparisons and intergroup comparisons were performed using ANOVA followed by Tukey's multiple comparison test.


   Results Top


[Table 1] shows the three treatment modalities and their mean L-values at baseline, WSL pretreatment (PreRX), and WSL posttreatment (PostRX). There was no significant difference among the three treatment modalities in the mean values of L-value at baseline (sound enamel) and WSL pretreatment (natural WSL), thus indicating that groups were comparable at baseline and WSL before treatment. However, in all groups, the mean values of L-value were significantly higher in PreRX WSL (P < 0.01; Tukey) compared to baseline (sound enamel). After treatment (WSL PostRX), the mean values of the L-value increased in both Bleaching and Microabrasion groups and decreased in Infiltration group, but these changes were not statistically significant in any group when compared with WSL PreRX. However, when compared with baseline, the changes were significant (P < 0.01, Tukey) only in Bleaching and Microabrasion groups but not in Infiltration group. The mean difference between infiltration and the other two treatments groups was statistically significant (P < 0.005, Tukey). Thus, following treatment, the difference in mean values of L-value between sound enamel (baseline) and WSL (PreRX) increased in Bleaching and Microabrasion groups from 8.5% and 6.9% to 9.9% and 7.9%, respectively, but decreased in Infiltration group from 6.2% to 2.8% [Table 1]. Thus, [Table 1] clearly demonstrates that resin infiltration decreased the L-value of the WSL, bringing it closer to the L-value of the sound enamel while bleaching and microabrasion increased the L-value, taking the tooth shade farther away from the shade of the natural enamel.
Table 1: Means (Standard deviation) values of L-value for Sound enamel and White spot lesions (Pretreatment (PreRX) and Posttreatment (PostRX))

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   Discussion Top


Enamel demineralization (WSL) around orthodontic fixed appliances presents both clinical and esthetic problems to the patient. Therefore, in orthodontics, WSL prevention is of particular importance. Unfortunately, most available preventive methods demand patients' compliance. Noncompliance with the thorough oral hygiene regimen required during orthodontic treatment with fixed appliances is the main cause of WSL development; thus, a number of patients still require treatment for WSLs after orthodontic treatment.[8],[9] The most popular noninvasive treatment options, among others, are tooth bleaching,[12] microabrasion,[13] and resin infiltration.[14] Thus, the present study investigated and compared the ability of tooth bleaching, microabrasion, and resin infiltration to restore the appearance of WSL to that of the original sound enamel. An effective WSL treatment should restore the WSL as close as possible to the shade of the immediate surrounding sound enamel.

In the present study, the bleaching group started with a baseline shade of 68.6, which correlates with a VitaPan Classical shade of D2. As bleaching progressed, the final shade of the entire tooth surface was brought to a mean L-value of 74, which correlates with a VitaPan Classical shade of ~A1. In terms of clinical observations, the teeth were significantly whiter. This would correlate to a shade increase of approximately five shades. This amount of change may not be necessary for every patient. The manufacturer suggests monitoring whitening every 1 to 3 days to treat each patient according to their individual needs. On average, bleaching WSLs with 10% carbamide peroxide increased shade approximately 1.7 units in L-value, indicating an increase in brightness. The final difference between baseline and posttreatment WSL was approximately an L-value of 7 units (equivalent to six shades, on the Vita classic shade guide). Only 25% of the teeth in the bleaching group were successfully masked. Overall, bleaching was able to produce teeth which appeared, on average, 10% different in shade discrepancy from the baseline value (natural enamel shade). It is worth noting that bleaching often whitens the whole tooth, thereby increasing the overall baseline shade, and thus masked the WSL by increasing baseline shade. However, strictly from comparing bleaching to the original baseline shade, bleaching was a valid method of camouflaging white spot lesions in only 25% of the sample size. Compared with other bleaching studies, patients typically achieve two shades of whitening after bleaching for 2 weeks.[5],[16],[17] The ADA has also defined whitening as efficient if two shades of whitening are achieved.[20] It is possible to say from the present study that bleaching should be able to camouflage the WSLs after the removal of the orthodontic appliances. However, it has been reported in a previous study that some bleaching agents have the potential to damage the surface finish of microhybrid and microfilled composite restorations,[21] thus care should be taken in selection of bleaching materials for patients with such restorations. Unfortunately, the present study did not assess the effects of the used bleaching material and microabrasion on the surface roughness properties of the investigated teeth.

Consistent with other studies,[14],[15] in the present study, resin infiltration worked very well for some lesions and not as well for deeper lesions. On average, the amount of color change in L-value with infiltration was 2.4 units, which would correlate with approximately four to five shades. Some lesions were so well-camouflaged that it was difficult to discern the previous location of the WSL. These lesions were typically observed to be shallow lesions. On severe lesions, infiltration was not able to mask the lesion. Severe lesions improved slightly, but the WSL was still apparent and appeared to have a shiny surface sheen to it. It is believed that the strong acid of the etchant (15% HCL) etches off the demineralized tissue (WSL) and replaces the tissue with the clear resin. The etching-off is complete in shallow lesions and partial in deeper lesions, thus the incomplete masking of the deeper lesions. Despite not working on all lesions, on average, infiltration was able to correct pretreatment WSL with an average of negative 2.4 units in L-value. The negative value in this measurement implies that after treatment, the lesion reduced in lightness than before, thus bringing the shade of the lesion surface closer to the baseline value (normal enamel shade). On the CIE Lab scale, zero represents the color black, and one hundred represents the color white, so any shift toward zero indicates a decrease in lightness. Infiltration was the only method that was able to lower posttreatment WSL toward baseline values [Table 1]. On average, infiltration produced lesions which were only different from baseline values by 2.8%. Therefore, based on this in vitro study, we considered infiltration as a valid option for addressing white spot lesions. Thus, the result of the present study rejected our hypothesis that among the tested treatment modalities, bleaching will restore white spot area most closely to the appearance of the original healthy enamel. It is conceivable that the better treatment outcome with Resin Infiltration treatment is attributable to the fact that strong acid of the etchant etches off the demineralized tissue (WSL) and replaces the tissue with resin that has translucency very close to that of enamel. The slight difference in shade (2.8%), particularly in deeper lesion, is believed to be due to the original enamel (baseline value) having a dentin base underneath, while the resin has a residual demineralized tissue (WSL) underneath. Thus, the near similar translucency of enamel and resin may explain the better treatment outcome with Resin Infiltration.

Of all the treatment methods, microabrasion appeared to be the messiest during application. The slurry would often splatter, and thus, the use of a rubber dam application was a must as stated by the manufacturer. During data collection, microabrasion slurry seemed to make the entire tooth surface lighter in color. One explanation is that the acid in the slurry (6.6% hydrochloric acid) etches the enamel surface, producing a whitish frosty appearance, which is traditionally seen in enamel etching procedures. It is also possible that microabrasion removed the surface layer, and exposed a deeper and perhaps even more prominent portion of the WSL in some teeth. After removing the slurry, we also observed the luster as described in other studies.[13] Microabrasion was only able to change the pretreatment WSL by 0.7 units in terms of L-value. This change in shade was considered clinically insignificant. At this point, it is pertinent to mention that prior to actual study assessments, multiple readings of a sample test tooth were performed to observe the differences in taking repeated readings at the same site to reveal any errors that may have arisen from measurement error. We found differences only varied by at most one unit after multiple readings. Because multiple readings had a tolerance of one unit, we concluded any changes equal to or less than one unit should be classified as insignificant or negligible because it could have been attributed to instrument measurement error. Statistical analysis also confirmed nonsignificance of this change. The positive L-value also indicates the WSL became whiter. This was consistent with visual observation that WSL appeared to be unchanged or even whiter, after two applications of microabrasion. We, therefore, considered it that using microabrasion did not improve WSL significantly in this study.

Of the three investigated methods, bleaching and infiltration seemed the most promising. Resin infiltration was able to mask WSL the most by lowering the color difference in value from pretreatment to posttreatment by a negative 2.4 units. This was the only method to mask and lower the value of the WSL relative to baseline. Other methods increased the whiteness of the WSL, which was expected for bleaching at 1.7 units, but were surprising for microabrasion at 0.7 units. Thus, our hypothesis that among the tested treatment modalities, bleaching will restore white spot area most closely to the appearance of the original sound enamel was rejected. With regards to a no treatment option, WSL will presumably remain on the teeth indefinitely. On average the difference between a baseline reading and a WSL with no treatment, in this study ranged from 4.2 to 5.1 in L-value [Table 1]. In order of effectiveness, resin infiltration was most effective in masking WSL, followed by bleaching and microabrasion.

The mechanisms by which white spot masking occurs vary. Microabrasion was the application of an acidic and abrasive compound to the surface of the enamel and removes on average 12 μm on the first application and 26 μm on subsequent applications.[13] Caries infiltration exploits capillary forces to transport resins with high penetration coefficients into enamel porosities.[22] After polymerization, the infiltrant blocks pathways for cariogenic acids to diffuse into and dissolve the tooth tissue,[23],[24] thus preventing further progression of the caries lesion. For bleaching, there was a great controversy regarding the effect of bleaching agents on mineral contents of enamel. Some in situ studies have been performed to verify the interaction of bleaching agents with saliva, soft tissues, and dental structures; however, further evaluations regarding this matter were needed.[25] The mechanism by which teeth are whitened by oxidizing materials such as hydrogen peroxide and carbamide peroxide is currently not fully understood.[26]

Although the present study achieved its objective of determining the treatment modality that can restore the appearance of an existing white spot lesion as close as possible to that of the immediate surrounding healthy enamel, it has some limitations. The study did not assess the effects of the bleaching and microabrasion on the surface roughness properties and mineral contents of the enamel surface, which may affect the clinicians' decision on the use of these techniques. Furthermore, photographs of the treated teeth would have helped the readership to appreciate the reported outcome of the treatments. Finally, the use of only the L value of the CIE L*A*B measurement system for assessing the outcome of the study is another limitation of this study. Future studies in this area should put these points into consideration.


   Conclusions Top


Among the three investigated treatment modalities in thisin vitro study, resin infiltration was able to mask WSLs the most. On average, lesions treated by resin infiltration improved by two to three units in L-Value. Bleaching was able to mask approximately 25% of the samples in this experiment and should be considered. Last was microabrasion, which has been successful in other studies, but did not appear to produce a significant improvement in this study. Further research involving a clinical trial is needed to evaluate the long-term effects of resin infiltration. We recommend a future study on resin infiltration and a comparison with remineralization.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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