White spots (WS) related to orthodontic treatment are severe cariologic and cosmetic complications, but they are shown to be partially reduced by remineralization or abrasion in short-term follow-ups. In this prospective study, we quantitatively analyzed changes in WS in general and in treatment-related white spot lesions (WSL) during orthodontic treatment and at a 12-year follow-up after treatment. In addition, we quantitatively compared the effects of an acrylic bonding material vs a glass ionomer cement (GIC) on WSL.
Sum areas of WS and WSL were calculated on scans of standardized photos of the vestibular surfaces of 4 teeth in consecutive orthodontic patients (median treatment time, 1.7 years) bonded with the 2 materials in a split-mouth design. Comparisons were made in 59 patients before treatment (BF), at debonding (T0), at 1 year (T1), and at 2 years (T2), and in 30 patients at a 12-year follow-up (T3) with the Friedman test followed by pairwise comparisons with the Wilcoxon matched-pairs signed rank test. Differences of the effects of acrylic vs GIC on the sum areas of WSL were tested for each observation period with the Mann-Whitney U test.
Increases in the sum areas of WS and WSL from BF to T0 ( P <0.001) were followed by significant decreases at T1 ( P <0.001) and T2 ( P <0.01 for WS; P <0.001 for WSL). Significant changes were also found in the sum areas for WS at T3 compared with T2 ( P <0.01), but not for WSL ( P = 0.328). The sum areas of WS and WSL at T3 did not return to BF levels ( P <0.001). Sum areas of WSL were higher for surfaces bonded with acrylic compared with GIC for each observation period from BF to T2 ( P >0.001), and from T2 to T3 ( P >0.05).
Although significantly reduced during the 12-year follow-up and significantly lower with the GIC than the acrylic material at bonding, WSL are a cariologic and cosmetic problem for many orthodontic patients.
White spot lesions are well-known complications of orthodontic treatment. These areas of local decalcification of enamel without cavity formation are found in up to 95% of orthodontic patients and are often exacerbated by the difficulties of maintaining good oral hygiene around fixed appliances.
This article makes a significant contribution to the literature in several areas. First, 30 patients were followed for 12 years after their orthodontic treatments. This is the longest follow-up reported in the literature. There is often a tendency to assume that white spot lesions might fade over time, and this study shows that, although the total areas of white spot lesions decreased, they did not totally disappear.
Additionally, the photographic technique developed by the authors was shown to be valid and reliable, as well as more accurate in detecting changes than previous rating scales.
Finally, the authors limited their assessment to lesions in areas where decalcification caused by cariogenic plaque collects. Although it was impossible to accurately assess the origins of all lesions, this undoubtedly improved the applicability of the study to orthodontic treatment.
Clinicians still must be concerned about the potential for their patients to develop decalcification areas during orthodontic treatment. Although the use of glass ionomer cement might reduce their incidence, white spot lesions will not go away, even after 12 years.
Leslie Will, Associate Editor
Q & A
Will: In your article, you mentioned that the selection of the maxillary lateral incisors and mandibular canines for examination was based on the available knowledge when the study was planned. Is better information available today about which teeth are most susceptible to decalcification during orthodontic treatment?
Shungin: The most recent studies, including a randomized controlled trial, showed that, if fluoride varnishes are not used, maxillary lateral incisors (studied here) are more susceptible to WSL compared with other maxillary teeth. In the mandible, the first molars have the highest prevalence of WSL. Because of difficulties in standardizing photographic records, these molars could not be studied for our article.
Will: Although statistically significant, are the findings comparing the incidence of WSL with glass ionomer and acrylic bonding materials clinically significant? Would you recommend routine use of GICs for bonding?
Shungin: The clinical significance of differences between the 2 products in the long run was speculated to be explained by more severe (deeper) lesions associated with acrylic bonding materials; this was supported by a recent study.
A number of factors and steps in the bonding process are known to influence bond strength of glass ionomer-based materials. However, studies have shown that light-cured GICs have the bond strength values needed for successful clinical bonding and can be routinely used. This supports the possible promotion of wider usage of GICs, especially when their fluoride-releasing ability is considered.
Will: Although the area of a lesion might or might not have changed, did the intensity of discoloration change over time? That is, could a lesion be faded, although still present?
Shungin: The main focus of our article was to study changes in the area of orthodontically induced WSL. Our study was also blind and randomized by both examination and patient; this means that the time sequence of the photos was not known to us while assessing the photographic images. When the assessment was completed and the time sequence was restored, the general impressions were that the borders of the demineralization areas were less prominent and also a slight decrease in intensity of the whiteness of the spot occurred with time (in line with the impressions of “less chalky” at clinical examinations). It is a well-known clinical phenomenon that lesions can stop over time, but the demineralized enamel, covered by the “healed” surface layer, remains as a scar.