The aims of this study were to compare blood parameters and periodontal characteristics of orthodontic patients allergic to nickel with those of nonallergic patients and to determine the correlation between blood components and periodontal abnormalities.
Ninety-six randomly selected patients participated in the study. After determining the prevalence of those allergic to nickel, 2 groups were formed: 16 allergic patients and 16 nonallergic patients. Allergies to nickel were diagnosed by using the patch test, periodontal conditions were determined by using the gingival index, and humoral characteristics were determined through a complete blood test, including the quantification of nickel in the blood and the immunoglobulin E level. Feces examinations were performed to control for parasitic infections. Periodontal evaluations were performed blindly. Statistical analysis included the unpaired t test, the Mann-Whitney test, and the Pearson and Spearman correlations ( P ≤0.05).
Statistically significant differences between groups were found for bands ( P = 0.001). There was no correlation between the concentration of nickel and immunoglobulin E level ( P = 0.674, experimental group; P = 0.605, control group). However, there was a positive correlation between the gingival index and the number of bands ( P = 0.05).
Nickel can have an influence over the periodontal status of allergic orthodontic patients, causing an increase in band quantification that was correlated to gingival index.
Allergic and inflammatory reactions have commonly been associated with release of metal ions, especially nickel, during orthodontic treatment. Although corrosion of orthodontic devices occurs, it does not appear to result in significant destruction of metallic components or have significant detrimental effects on mechanical properties. However, several studies have established an association between nickel and allergic manifestations in orthodontic patients.
A critical analysis of the literature showed a lack of consistent evidence on the subject. Part of this problem is due to the methodologic limitations in most studies (study design, sample size and characterization, type of evaluation), leading to conflicting results and compromising clinical decision making.
The prevalence of nickel sensitization is near 10% in the general population, and its frequency in women is about 5 times higher than in men. Nickel has often been pointed out as a biologic sensitizer capable of causing short-term and long-term sensitivity reactions: type IV immune response, cell-mediated by T-lymphocytes. However, during orthodontic treatment, sensitive patients are at greater risk of oral discomfort, which hinders both hygiene and treatment. More than a direct sensitizing agent of skin and mucosa, nickel appears to alter periodontal status, acting as a modifying factor of periodontal disease in sensitive patients and creating inflammatory patterns of immune reactions.
In such a context, a number of questions should be raised. What are the clinical and biologic implications of an allergy to nickel for orthodontic patients? Are the effects associated with the buildup of nickel throughout orthodontic treatment or the local release of the ions? Are reactions mediated by an allergic or inflammatory response?
The aim of this study was to determine the correlation between blood parameters and periodontal abnormalities in orthodontic patients allergic and nonallergic to nickel.
Material and methods
Ninety-six patients awaiting orthodontic treatment at a specialization course in orthodontics of the Vale do Rio Verde University, Três Corações, Brazil, were randomly selected for participation in the study. All were white; 58 (60%) were female, and 32 (40%) were male; their ages ranged from 10 to 43 years.
All subjects began orthodontic treatment at the same time (in January 2006). Before the placement of the appliances, all participants received prophylaxis with bicarbonate spray and orientation on oral hygiene. Morelli braces (Sorocaba, São Paulo, Brazil) were attached; these braces have the following composition: 16% to 18% chrome, 10% to 14% nickel, and 2% to 3% molybdenum.
Regarding the periodontal aspects, clinical gingival characteristics such as color and volume were assessed. By using a standardized millimeter probe, the presence or absence of gingival bleeding on probing in the region of the maxillary and mandibular first premolars was assessed at 3 points on the vestibular, lingual, mesial, and distal faces. The Loe index was used for periodontal status assessment, with the following classification: 0, normal gingiva; 1, mild inflammation, slight change in color, with no bleeding on probing; 2, moderate inflammation, reddish appearance, mild edema, bleeding on probing; and 3, severe inflammation, reddish appearance, clear edema, ulceration, tendency toward spontaneous bleeding. The Loe index was based on mean values of 4 first premolars multiplied by 3 sites per tooth. However, the mean value is used to make a score, which classifies the patient into 4 categories. First premolars were selected because of their location at the halfway point of each quadrant of the oral cavity. In general, first molars are preferred for periodontal status evaluation. However, they had bands, and periodontal status could not be evaluated in those teeth. The Loe index takes into account qualitative changes in the gingival tissue. If a patient had at least 2 of the classifications of each previous item, he or she was placed in the more severe category.
Assessments of periodontal status were carried out by 1 blinded, duly calibrated (kappa >0.90) examiner at regular 3-month intervals for 12 months (4 evaluations: T1, T2, T3, and T4) with braces in place. Additionally, prophylaxis with bicarbonate spray was performed at each session (after the periodontal evaluation).
The skin patch test was used for the diagnosis of nickel allergy. This is the most efficient method for confirming the etiologic diagnosis of allergic-contact eczema and consists of a 2 × 2 cm patch (Finn Chambers) attached to the dorsal region of the patient at 2 points 10 cm apart, after cleansing of the skin with cotton soaked in alcohol. Because of the extensive area involved, an ideal amount of the gel (standardized by the manufacturer) containing a 5% nickel sulfate antigen (solid petroleum jelly) (Epitest Ltd Oy, Tuusula, Finland) remained for 48 hours. During the placement of the patches, patients were instructed to remove them if they experienced any reaction beyond the expected and to call the researchers in charge and go to the municipal medical emergency room. After 48 hours, the patches were removed, and only 1 reading was made in compliance with the norms of the International Contact Dermatitis Research Group.
Its guidelines are as follows: (–) negative; (+) discrete erythema with some papules; (++) erythema, papules and vesicles; (+++) intense erythema, papules, and vesicles. All patients considered negative had no clinical condition visible to the naked eye, and all patients considered positive had erythema, edema, papules, and blisters (+++).
Nine months after the beginning of treatment, the prevalence of patients with a nickel allergy was determined by using the patch test. At this time, 1 subject with intraoral piercing, 1 who abandoned treatment for personal reasons, and 1 who was pregnant were excluded from the study. Sixteen patients (17.2%) were determined to have a nickel allergy and formed the allergic group. Among the nonallergic subjects, 16 were randomly selected to form the age-paired control group. After the prevalence of those allergic to nickel was determined and the control group was formed, all 32 participants underwent a full blood test, assessment of total immunoglobin E (IgE), and determination of the amount of circulating nickel in the blood throughout the orthodontic treatment. For the examinations, 6 mL of blood was vacuum collected (vacuo-time system) from all patients after they fasted for 8 hours. For the blood count, 3 mL of blood in a vacuum tube with the EDTA anticoagulant was analyzed on an automated hematology analyzer, by using the ABX Micros CRP device (OT-CT-OS-CS, France). The differential count of blood cells was performed through a blood smear without anticoagulant, stained with Single Prov stain (NewProv – eosin methylene blue solution of cyclohexadiene to 0.1%), viewed under a microscope and read, with the aim of immersion and platelet count. For the evaluation of total IgE, 1 mL of serum without anticoagulant was analyzed by using the chemoluminescence method on the Inmulite equipment. Two 2 mL of blood was used to assess the amount of circulating nickel, collected in a trace tube for atomic absorption spectrophotometry (graphite kiln with Zeeman corrector). In the blood count, analyses were performed of leukocytes, basophils, eosinophils, myelocytes, metamyelocytes, bands, neutrophils, lymphocytes, and monocytes.
Feces examinations were performed on all 32 participants to determine parasitic infestations (helminth eggs and larvae, protazoon cysts) that might affect the white blood cell count, especially the number of eosinophils. The feces were collected in a sterile container, and patients were instructed to avoid contamination, using the method of Hoffman, Pons, and Janer, with centrifugation and spontaneous sedimentation of recent feces with no conservatives. The material was placed on a slide and assessed under a microscope (Alphaphot, 2Y52, Nikon, New York, NY). All laboratory examinations were performed by a duly trained pharmacist-biochemist (M.A.Z.). Patients who had verminosis (1 from the allergic group and 2 from the nonallergic group) were excluded from the statistical analysis of the blood components because the parasitosis could impact the results of the blood test.
Statistical analysis included the unpaired t test and the Mann-Whitney test for the intergroup comparison of the blood components, Pearson and Spearman coefficients for correlating the amount of circulating nickel with the IgE (immunoglobin of the allergy), and the Loe index at T3 with the number of bands. Differences were considered significant at P ≤0.05.
The study received approval from the Research Ethics Committee of the Vale do Rio Verde University, Três Corações, Brazil, under process number 0001.0.380.000-07.
Preliminary analyses were conducted between the groups. The results in Table I refer to the blood parameters evaluated in both groups. Only data comprising white cells are presented, since red cells are not related to immune response. The number of bands was the only variable with a statistically significant difference between groups, with higher values found in allergic patients.