INTRODUCTION

It is difficult to effectively educate, train, and encourage patients to reduce plaque solely by mechanical means since mechanical methods of plaque removal require time, motivation, and manual dexterity.1 This is especially true with fixed orthodontic appliances, in which a high plaque accumulation has been described.2–5 Plaque in association with fixed appliances can result in clinical problems such as demineralization of the adjacent enamel367 and gingival inflammation.478 This is more prevalent in adolescents than in adults.9

It is generally accepted that gingival health is jeopardized when orthodontic bands are worn.591011 However, an increase of periodontopathogenic bacteria and a subsequent enhancement of inflammation have been observed around orthodontic bands and brackets in comparison to nonbanded or bonded teeth.1213 It has also been shown that periodontal pathogens are significantly more prevalent in orthodontic patients than in the control group.14 Recent studies confirm that fixed orthodontic appliances impede correct hygiene, resulting in more plaque accumulation, inflammation, and bleeding.15 In previous studies, plaque accumulation and levels of gingivitis were higher for banded than for bonded teeth.910 However, as recently shown, even the placement of brackets influences the accumulation and composition of the subgingival microbiota, resulting in an increase of inflammation in comparison to nonbonded teeth.2

Gingivitis and the often described gingival enlargement810 are the result of the inflammatory response to the plaque microbiota and its products. Inflammatory mediators cause an increased vascular permeability and dilatation. The exudative fluid and proteins swell the tissue, and an influx of inflammatory cells into the connective tissue subjacent to the junctional epithelium occurs. Periodontal pathogens elicit signals in resident gingival cells or in immune cells infiltrating the gingival tissues, which results in immune response.16 Cytokines in inflamed periodontal tissues have been cited as being of major importance in periodontal disease progression.17 It has been shown that the local production of interleukin (IL)–1β in the gingival crevicular fluid rises with the increase of inflammation.1618 Hence, IL-1β is a reliable marker for the degree of gingival inflammation.

Preventive measures that do not require the compliance of the patient seem to be more appropriate for orthodontically treated adolescents. Chlorhexidine (CHX), commonly administered through rinsing solutions, can be used in the form of gels or varnishes to control plaque development and thereby prevent gingivitis.1920 The enhanced antibacterial effect of CHX-containing varnishes has been suggested to be due to a prolonged contact of the varnish on the teeth and the sustained release of the CHX.2122

The antibacterial effect of such varnishes has been confirmed by many studies, in which the suppression of mutans streptococci colonization around bands and brackets was evident.21–25 Hereby, the development of white spot lesions was inhibited. The improvement of the gingival conditions has been described during orthodontic treatment1926 as well as for adolescents without fixed orthodontic appliances.2627 For the latter patients, the CHX varnish improved the clinical parameters, in particular when an elevated plaque accumulation was present at the beginning of the study.28

The aim of this prospective randomized controlled trial (RCT) was to compare the severity of clinical inflammation parameters and the level of the inflammatory mediator IL-1β during orthodontic treatment by using brackets and bands within a split-mouth design. In addition, the effect of a CHX varnish was investigated.

MATERIALS AND METHODS

In this prospective longitudinal RCT, 40 healthy children who required orthodontic treatment were examined. The inclusion criteria were good general health, mild tooth irregularities, and a Class I molar relationship. A healthy periodontal tissue and the absence of any drug administration (especially anti-inflammatory drugs) or an antibiotic therapy within the past 6 months and during the examination were also required.

Prior to beginning orthodontic treatment, the children were given oral hygiene instructions (modified Bass technique, fluoridated toothpaste). The study was approved by the ethics committee, and a written consent was obtained from the patients and their parents.

Twenty children (12.9 ± 2.0 years) received a CHX-containing varnish (Cervitec, Ivoclar Vivaden, Schaan, Liechtenstein) during the treatment, while the remaining children (12.4 ± 1.3 years) served as controls. Consequently, two groups (each group containing 8 males and 12 females) were established. The orthodontic attachments (brackets from OmniArch, GAC International Inc, Bohemia, NY, and bands from Snap-Fit, GAC International Inc, Bohemia, NY) were randomly allocated in a split-mouth design to the teeth (first and second premolar) that were to be tested.

After the bonding or the banding procedure, as well as after 12 and 24 weeks, a standardized amount of Cervitec (0.05 mL), which contains 1% chlorhexidine diacetat and 1% thymol, was applied according to the recommended interval2429 and the manufacturer's instructions.

Periodontal pocket depths (PDs) in millimeters and bleeding following probing were noted by using a periodontal probe (PCP11) at baseline and every 4 weeks during the 6-month study. In addition, the plaque index30 (PI) and the gingival index (GI) by Loe and Silness31 were evaluated. The data were recorded at three surfaces (mesial, buccal, and distal) by one experienced operator. Gingival hyperplasia was detected by measuring the distance of the gingiva from the position of the slot at each appointment. The PDs were corrected by subtracting the hyperplasia (PD-H).

Gingival crevicular fluid (GCF) samples were taken at each appointment from the distal pocket of each second premolar with sterile filter paper strips using the method of Offenbacher.32 The total protein concentrations were estimated by the method of Bradford33 (QuickStart Bradford Protein Assay, Bio-Rad, Hercules, Calif). A quantitative enzyme-linked immunoassay technique (Quantikine, R&D Systems Inc, Minneapolis, Minn) was used to detect differences in IL-1β level between banded and bonded teeth. Furthermore, the IL-1β levels of the children who received the CHX varnish and the control group were assessed in duplicate (ng/μg protein), and the means were compared. Blood-contaminated strips were discarded.

The data were analyzed by SPSS 12.0 software (SPSS Inc, Chicago, Ill). The Wilcoxon test was used for the dependent data, and the Mann-Whitney U test was used for the independent data. Homogenous subgroups were statistically generated by analysis of variance (ANOVA) and post hoc Tukey test. The Kruskal-Wallis test was used to verify the ANOVA results. The significance was predetermined at P < .05.

RESULTS

For all the evaluated clinical parameters within the control group (Table 1), at baseline (t0), no significant differences between teeth with bands and those with brackets were noted (P > .05). Regarding the PD, teeth with bands showed statistically significantly higher PD and even higher PD-H values in comparison to bonded teeth at all follow-ups (t1–t6). A higher impact of band on gingival health was also reflected by the GI. In contrast, the PI from the second until the sixth follow-up was significantly higher for the bonded teeth (P = .0001). The changes of the evaluated parameters over time are shown in the linear diagrams (Figure 1) and in the results of the ANOVA (Table 2).

Table 1. Clinical Parameters: Bands vs Brackets Separately Listed for Both Groups

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Table 2. Changes of the Evaluated Clinical Parameters Over Time for Both Groups^a

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Within the Cervitec group (Table 1), no significant differences (P > .05) could be found at baseline (t0) between the attachments. In contrast to the control group, the PD and the GI were significantly higher merely in the third and sixth follow-up for the banded teeth. However, the PD-Hs were not significantly different between the two attachments for all the follow-ups. At four follow-ups, the PI was higher for bonded teeth (second, third, fifth, and sixth; P < .03). The effect of Cervitec can also be seen by the homogenous subgroups that were statistically characterized (Table 2) as well as by the linear diagrams (Figure 2) of the evaluated parameters.

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Considering the upper and lower jaw and the first and second premolar, the second premolars in the upper jaw showed the highest values. Regarding the surfaces, the proximal and especially the distal surfaces were affected more (data not shown).

By comparing the bonded and the banded teeth within the two groups (Table 3), the teeth that received Cervitec showed significantly lower values in most of the follow-ups for the clinically observed parameters (PD_Band, PI_Band, PI_Bracket, GI_Band, GI_Bracket) in comparison to the teeth without Cervitec (P > .015). Therefore, for the PD_Band, the PI_Bracket, and the GI_Band, highly significant differences were found (P = .0001). In particular, the probing depths of the bands were interesting. As mentioned before, there were highly significant differences between the control and the Cervitec groups. By taking notice of the hyperplasia, which could be measured with reference to the slot position (PD-H) of the bands, no significant differences were available (P > .05).

Table 3. Comparison of the Evaluated Parameters for Banded and Bonded Teeth Between the Two Groups^a

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The IL-1β levels within the control group (Table 4a) confirmed the results of the clinical parameters, as the banded teeth showed a significantly higher level in comparison to the bonded teeth at the last four follow-ups.

Table 4a. IL-1β Levels Between the Banded and Bonded Teeth Within Each Group

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Within the Cervitec group, the IL-1β levels between the banded and bonded teeth were not significant different. This supports the effect of Cervitec.

The decrease of the IL-1β level for the banded and bonded teeth after the Cervitec application is obvious in Figure 3b. This amount of decrease was not found within the control group (Figure 3a). The direct comparison of the IL-1β levels between the two investigated groups (Table 4b) showed no significant differences.

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DISCUSSION

During orthodontic treatment, an increased accumulation of plaque can be found around the bands and brackets because of the lack of adequate oral hygiene, which is often the case in pubertal young people.3 In accordance with the literature,910 we found that bands showed more gingival inflammation, gingival hyperplasia, and deeper pocket depths. Furthermore, the posterior surfaces were more affected.8

Contrary to the findings of previous studies,91012 in this study, the teeth bonded with brackets showed a higher plaque accumulation. One possible explanation for this is that our investigated teeth were premolars. This was done to prevent excessively overhanging gingival margins, since they are commonly linked to banded molars and are known to make plaque removal more difficult.934 In addition, by choosing the premolars, the possible impact of the manual dexterity was minimized since this is more important when cleaning the molars. Despite lower plaque accumulation, the banded teeth showed a higher impact on the gingival health.

Therefore, it can be stated that plaque may be the main but not the only reason for gingival inflammation.2 Some investigations are dealing with the possible impact of materials on gingival health.3536 Plaque was also found on the banded teeth, so this last hypothesis may have a secondary rather than a primary influence.

For the Cervitec application, we found a positive effect on gingival health, which is in accordance with the literature.192026 Within our investigation, the necessity of a more frequent application was evident because at least after two follow-ups, a reincrease of the evaluated parameters (including that of the IL-1β level) took place. This is in agreement with studies that showed that recolonization with pathogenic bacteria happens quickly.23 In addition, Øgaard et al37 stated that the main reason for some discrepancies with respect to the effectiveness of CHX varnish in the literature might be due to its less frequent application in comparison to daily rinsing. However, this is partly compensated for by the higher concentration of CHX in the varnish and by the synergetic effect of thymol. In this context, the possible side effects20 of more frequent CHX use have to be considered. The varnish, however, has been reported to show less adverse effects than other types of CHX administration.38

IL-1β was chosen as the cytokine of interest in this study because it is thought to be a sensitive and appropriate marker of the degree of gingival inflammation.3940

In contrast to the investigation of Yucel-Lindberg et al,19 in which a split-mouth design was used to prove the effect of Cervitec by measuring the IL-1β levels after 3, 8, and 30 days, we established a control group. In addition, in our study, the period of investigation was 6 months, which is recommended for the evaluation of such products.20 A control group was established to avoid the results' being influenced by an enrichment of the saliva by the prior locally applied CHX. In addition, we investigated the effect on different orthodontic attachments and the total cytokine amount in GCF, as the latter has been suggested to be more representative of the disease status in comparison to the concentrations.162241

Although the IL-1β level for banded teeth was significantly higher than that of bonded teeth within the control group for the last follow-ups and within the Cervitec group, the IL-1β level was not significantly different, which supports the effect of Cervitec. The direct comparison of the two groups showed no significant differences. This is perhaps biased by individual variations42 because we found a decrease of the IL-1β level for the banded and bonded teeth after Cervitec application, whereas within the control group, this decrease was not found. Cervitec might be more effective by decreasing the application interval.

CONCLUSIONS

• If the clinical situation allows, brackets should be preferred rather than bands, as they show less influence on gingival health. The increased risk for demineralization due to a higher plaque accumulation must be considered.

• In particular, Cervitec was effective in the reduction of gingival inflammation for bands and of plaque accumulation for brackets.