In vivo evaluation of fluoride dentifrice and diet control on the demineralization/remineralization process using laser readouts at the margin of the orthodontic bracket/enamel interface

PURPOSE

To evaluate, in vivo, the effect of fluoride dentifrice and diet control on the demineralization/remineralization processes at the margin of bracket/enamel interface bonded with four different bonding materials, using optical microscopy and fluorescent laser (DIAGNOdent).

METHODS

Premolars in 35 subjects (11 to 20 years old) were divided into Group 1 (n = 15) and Group 2 (n = 20). Four bracket/enamel interfaces (near points) and four points at a distance of 2 mm (distant points) were observed. Evaluations were made at the following times: 15 days before bracket bonding (T0), on day of bonding (T1), 1 week after bonding (T2), and 4 weeks after bonding (T3). Subjects received fluoride dentifrice, and toothbrush and were instructed to brush 3x/day, after main meals. Group 1 received the instructions at T1 and Group 2 at T0 and these were reinforced weekly. The Microarch brackets were bonded with four materials: Transbond XT; Concise Ortodôntico; Fuji Ortho LC and Monolok2. DIAGNOdent laser readouts were used for comparison.

RESULTS

Data were statistically analyzed by Mann-Whitney, Wilcoxon and Friedman tests (P < 0.05). Higher readouts were found at nearer points than at distant points; Group 2 presented lower readouts than Group 1; No differences were observed among bonding materials.

Cephalometric assessment of vertical control in the treatment of class II malocclusion with a combined maxillary splint

Vertical control is one of the primary objectives sought by orthodontists when treating malocclusions in hyperdivergent individuals. This investigation aimed at assessing vertical control, by cephalometric measurements, during the treatment of Angle Class II Division 1 malocclusion. Thirty cases, selected from the files of the São Leopoldo Mandic Dental Research Center, Brazil, of subjects with Angle Class II Division 1 malocclusion and facial hyperdivergence, were used in this study. The patients were treated using a combined extraoral appliance during a mean treatment time of 1.1 years. Pre- and posttreatment cephalometric measurements were compared to assess vertical control. The results were submitted to ANOVA (p = 5%). The ANOVA test revealed no statistically significant difference between the pretreatment and posttreatment values of OP (Occlusal plane angle) and SN.MP. While there was a decrease in Y-axis, FMA, and PP.MP, there was an increase in SN.PP, Co-Go, AFH, PFH, and FHI. It was concluded that the divergence in the facial lower third of the patients did not increase, suggesting that the combined extraoral appliance with the line of force application directed to the resistance center of the maxilla was effective in treating Angle Class II malocclusion in hyperdivergent subjects.

Effects of short- and long-term celecoxib on orthodontic tooth movement

OBJECTIVE

To test the hypothesis that short- and long-term celecoxib administration has no effect on orthodontic tooth movement.

MATERIALS AND METHODS

Male Wistar rats were submitted to short- (3 days) and long-term (14 days) celecoxib administration, while the respective control groups received equivolumetric saline intraperitoneal injections. The upper left first molars of all rats were moved mesially for 14 days by a fixed orthodontic appliance exerting 50 g force upon insertion. After the experimental period, tooth movement was quantified and tissues around the first molar were processed for tartrate-resistant acid phosphatase (TRAP) histochemistry. The amount of tooth movement and the number of TRAP-positive cells on the alveolar bone surface were evaluated.

RESULTS

The amount of tooth movement was significantly reduced in rats submitted to short- and long-term celecoxib administration, while the number of osteoclasts on the alveolar bone did not differ between the four groups studied.

CONCLUSIONS

The hypothesis is rejected. Although celecoxib administration did not affect the number of osteoclasts, the osteoclast activity might be reduced, which could explain the inhibition of tooth movement observed in the celecoxib-treated animals. These results indicate that orthodontists should be aware of patients under short- and long-term therapy with celecoxib.

Periodontal and microbiologic evaluation of 2 methods of archwire ligation: ligature wires and elastomeric rings

INTRODUCTION

Prophylactic programs to prevent dental biofilm accumulation must be implemented to minimize the risk for periodontal diseases in orthodontic patients. Therefore, we assessed the possible periodontal and microbiologic changes resulting from the use of 2 methods of orthodontic archwire ligation: elastomeric rings and steel ligatures.

METHODS

The following parameters were measured: plaque index, gingival bleeding index, probing depth, and biofilm samples from the maxillary second premolars and the mandibular lateral incisors were evaluated in 14 subjects without clinical signs of gingival inflammation before orthodontic appliance placement and after 6 months of treatment. Each orthodontic arch was fixed with elastomeric rings on 1 side of the midline, and steel ligatures were used on the opposite side. Polymerase chain reaction analysis was used to detect Porphyromonas gingivalis, Tannerella forsythia, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and P nigrescens.

RESULTS

The elastomeric rings were associated with a higher score for plaque index and bleeding than steel ligatures, as well as many positive sites of T forsythia and P nigrescens (P <0.05).

CONCLUSIONS

Elastomeric rings favored these 2 periodontopathogens and harmed gingival conditions.

Evaluation of root resorption associated with orthodontic movement in stressed rats

AIM

The aim of this study was to investigate the effects of acute and chronic systemic stress response on orthodontically induced root resorption.

METHODS

Male Wistar rats were restrained during 1 hour a day by stress models of short (3 days) and long duration (40 days), while control group was not submitted to restraint (N.=10/group). The upper left first molars of all rats were moved mesially by a fixed orthodontic appliance exerting 50 g force upon insertion during the last 14 days of the experiment. Then, animals were killed for blood collection and mensuration of plasmatic corticosterone by radioimmunoassay; the tissues around mesial root of the first molar were processed for histological and histochemical techniques with tartrate-resistant acid phosphatase. The degree of root resorption and the number of odontoclasts were evaluated, being the contralateral side of each animal serving as its control (split-mouth design).

RESULTS

The results revealed that the plasmatic levels of corticosterone were significantly higher in both the stressed groups than in the control one. There were no significant differences in the degree of root resorption and in the number of odontoclasts on the root between the 3 groups studied.

CONCLUSIONS

These results indicate that systemic stress alone can not be considered a risk factor for root resorption induced by orthodontic tooth movement.

The effects of systemic stress on orthodontic tooth movement

OBJECTIVES

To determine if systemic stress affects the biological reactions occurring during orthodontic tooth movement.

METHODS

Four groups of male 10 week-old Wistar rats were used. Group A animals (N=10) were restrained for one hour per day for 40 days; Group B animals (N=10) were restrained for one hour per day for three days; Group C (N=10) and Group D (N=8) animals were unrestrained. The upper left first molars in the rats in Groups A (long-term stress), B (short-term stress) and C (control) were moved mesially during the last 14 days of the experiment. The animals in Group D (N=8) were used for body weight and hormonal dosage comparisons only. They were not subjected to any stress and did not have appliances fitted. All animals were killed at 18 weeks of age and blood collected for measurement of plasma corticosterone. Tooth movement was measured with an electronic caliper. The right and left hemi-maxillae of five rats from each group were removed and the number of tartrate-resistant acid phosphatase (TRAP) positive cells, defined as osteoclasts, adjacent to the mesial roots of the upper first molars counted. The contralateral side in each animal served as the control (split-mouth design).

RESULTS

Corticosterone levels were significantly higher in the stressed groups (Groups A and B) than in the control group (Group C). Tooth movement was significantly greater in Group A (long-term stress) compared with Group B (short-term stress) and Group C (control), which did not differ from each other. There were significantly more osteoclasts in the long-term stress group than in the short-term stress and control groups.

CONCLUSION

Persistent systemic stress increases bone resorption during orthodontic tooth movement. Systemic stress may affect the rate of tooth movement during orthodontic treatment.

Comparative cephalometric study between nasal and predominantly mouth breathers

Aim

to evaluate the possible correlation between the respiratory pattern in determining the craniofacial dimensions, using as baseline the Tweed-Merrifield's cephalometric analysis, added to angle SN-GoGn and to Y axis angle.

Methodology

The selected sample to this study comprised 50 teleradiographies taken in lateral and natural positions of the head in young female patients at the age of 9 to 12 years, presenting mean age of 10 years and 5 months and Class 1 malocclusion. After diagnosis of respiratory pattern, the sample was divided into two groups: control group, 25 teleradiographies of nasal breathers in lateral and natural positions of the head; experimental group, 25 teleradiographies of predominantly mouth breathers in lateral and natural positions of the head.

Results

The results were submitted to descriptive analysis (mean and standard deviation), test F and “t” Student test with significance level of 5%. There was no significant difference between the group with nasal breathing and the group with predominantly mouth breathing for any of the studied variables.

Avaliação cefalométrica da posição do osso hióide em crianças respiradoras bucais

MATERIAL E MÉTODOS: em função das relações anatomofuncionais do osso hióide com o complexo craniofacial, realizou-se avaliação cefalométrica da posição do osso hióide em relação ao padrão respiratório. A amostra consistiu de 53 crianças, gênero feminino, com idades médias de 10 anos, sendo 28 respiradoras nasais e 25, bucais. As medidas cefalométricas horizontais, verticais e angulares foram utilizadas com a finalidade de determinar a posição do osso hióide. Estabeleceu-se uma comparação entre os grupos por meio do teste "t" de student, bem como correlação de Pearson entre as variáveis. RESULTADOS: Observou-se que não ocorreram diferenças estatísticas significativas para a posição mandibular e posição do osso hióide e o tipo do padrão respiratório. No Triângulo Hióideo, o coeficiente de correlação de 0,40 foi significativo entre AA-ENP (distância entre vértebra atlas e espinha nasal posterior) e C3-H (distância entre a terceira vértebra cervical e osso hióide) demonstrando uma relação positiva entre os limites ósseos do espaço aéreo superior e inferior. Para as medidas cranianas sugeriu-se uma relação entre a posição do osso hióide com a morfologia mandibular. CONCLUSÃO: Os resultados permitiram concluir que o osso hióide mantém uma posição estável, provavelmente, para garantir as proporções corretas das vias aéreas e não depende do padrão respiratório predominante.

Comparison of cephalometric measurements from three radiological clinics

The orthodontic documentation carried out in radiological clinics is essential for diagnosis, planning and control of the orthodontic treatment. Amongst the diagnosis elements used are the cephalometric measurements, and errors can be incorporated as they are obtained. The objective of this work was to evaluate the values of some cephalometric measurements obtained in three radiological clinics using 30 lateral cephalometric radiographs of the head randomly chosen from the archives of the Department of Child Dentistry (Discipline of Orthodontics), School of Dentistry of Piracicaba, UNICAMP. These values were compared with the measurements obtained manually (control group) using variance analysis and Tukeys and Friedmans tests. Of the fourteen cephalometric measurements evaluated, the results demonstrated that only four of them presented statistically significant differences: IMPA, 1-NA, FMA, and H-nose. We concluded that although the majority of the mean cephalometric values did not present statistically significant differences, a great variability in the results was found when all the radiographic values were compared. This variability may influence the interpretation of the cephalometric measurements. Hence, we suggest that when the practitioner receives orthodontic documentation, he/she should redo the cephalometric analysis and compare the measurement values found with those presented to him. In addition, the practitioner should be prepared to use other elements for diagnosis, planning and control of the orthodontic treatment.

Cephalometric assessment of the hyoid bone position in Oral Breathing Children

Summary

Material and Methods: because of its anatomical and functional relationship with the craniofacial complex, we assessed the cephalometry of the hyoid bone position in relation to the respiratory pattern of these 53 female children, with average age of 10 years; 28 of them are nasal breathers and 25 are oral breathers. Horizontal, vertical and angular cephalometric measures were used in order to determine the hyoid bone location. The Student “t” and the Pearson correlation tests were used in order to compare the groups and the variables.

Results

We did not see statistically significant differences in mandible and hyoid bone positions and the respiratory pattern. In the hyoid triangle, the 0.40 correlation coeficient was significant between AA-ENP (distance between the Atlas vertebrae and the posterior nasal spine) and C3-H (distance between the third cervical vertebrae and the hyoid bone) showing a positive relation between the bony limits of the upper and lower air spaces. For cranial measures we have suggested a relationship between the hyoid bone position and the mandible morphology.

Conclusion

The results led us o conclude that the hyoid bone keeps a stable position, probably in order to secure correct ratios in the airways, and it does not depend on the respiratory pattern.

How may stressful experiences contribute to the development of temporomandibular disorders?

Temporomandibular disorders (TMD) comprise the most common cause of chronic facial pain conditions, and they are often associated with somatic and psychological complaints including fatigue, sleep disturbances, anxiety, and depression. For many health professionals, the subjectivity of pain experience is frequently neglected even when the clinic does not find any plausible biologic explanation for the pain. This strictly biomedical vision of pain cannot be justified scientifically. The purpose of this study is to demonstrate, by original articles from the literature and recent studies conducted in our own laboratory, the biological processes by which psychological stress can be translated into the sensation of pain and contribute to the development of TMD. The role of the hypothalamic-pituitary-adrenal axis, the serotoninergic and opioid systems in the pathogenesis of facial pain is exposed, including possible future therapeutic approaches. It is hoped that knowledge from apparently disparate fields of dentistry, integrated into a multidisciplinary clinical approach to TMD, will improve diagnosis and treatment for this condition through a clinical practice supported by scientific knowledge.

Shear bond strength of new and recycled brackets to enamel

The purpose of this study was to evaluate in vitro the shear bond strength of recycled orthodontic brackets. S2C-03Z brackets (Dental Morelli, Brazil) were bonded to the buccal surfaces of 50 extracted human premolars using Concise Orthodontic chemically cured composite resin (3M, USA). The teeth were randomly assigned to 5 groups (n=10), as follows. In group I (control), the bonded brackets remained attached until shear testing (i.e., no debonding/rebonding). In groups II, III and IV, the bonded brackets were detached and rebonded after recycling by 90-microm particle aluminum oxide blasting, silicon carbide stone grinding or an industrial process at a specialized contractor company (Abzil-Lancer, Brazil), respectively. In group V, the bonded brackets were removed and new brackets were bonded to the enamel surface. Shear bond strength was tested in an Instron machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. There was no statistically significant difference (p>0.05) between the control brackets (0.52 kgf/mm2), brackets recycled by aluminum oxide blasting (0.34 kgf/mm2) and new brackets attached to previously bonded teeth (0.43 kgf/mm2). Brackets recycled by the specialized company (0.28 kgf/mm2) and those recycled by silicon carbide stone grinding (0.14 kgf/mm2) showed the lowest shear strength means and differed statistically from control brackets (0.52 kgf/mm2) (p<0.05). In conclusion, the outcomes of this study showed that bracket recycling using 90-microm aluminum oxide particle air-abrasion was efficient and technically simple, and might provide cost reduction for orthodontists and patients alike.

Estudo cefalométrico comparativo entre respiradores nasais e predominantemente bucais

OBJETIVO: avaliar a possível influência do padrão respiratório na determinação das dimensões craniofaciais, tendo como base a análise cefalométrica de Tweed-Merrifield, acrescidas do ângulo SN-GoGn e do ângulo do eixo Y. METODOLOGIA: A amostra selecionada para o presente estudo constou de 50 telerradiografias, tomadas em norma lateral e posição natural de cabeça, de jovens do sexo feminino, na faixa etária de 9 a 12 anos (idade média de 10 anos e 5 meses) com maloclusão de Classe I. Após o diagnóstico do padrão respiratório, dividiu-se a amostra em dois grupos, assim constituídos: grupo controle - 25 telerradiografias de respiradores nasais e grupo experimental - 25 telerradiografias de respiradores predominantemente bucais. RESULTADOS: foram submetidos à análise descritiva (média e desvio padrão), teste F e teste "t" de Student com nível de significância de 5%, através dos quais foi possível constatar não existir diferença significativa entre os grupos com respiração nasal quando comparado com o grupo de respiração predominantemente bucal para nenhumas das grandezas estudadas.

Shear bond strength of metallic orthodontic brackets bonded to enamel prepared with Self-Etching Primer

The aim of this study was to determine the shear bond strength of different composites and to determine the adhesive remnant index (ARI) of metallic brackets bonded to enamel prepared with Transbond Plus Self-Etching Primer (TPSEP). Forty human premolars were divided into four equal groups. In group 1 (control), the Transbond XT was conventionally used. In groups 2-4, the TPSEP was used before bonding with Transbond XT, Z-100, and Concise Orthodontic, respectively. After the bonding, the samples were stored in distilled water at 37 degrees C for 24 hours. The brackets were debonded using a universal testing machine at a crosshead speed of 0.5 mm/ min. The shear bond strength (MPa) for group 1 (control), group 2 (TPSEP + Transbond XT), group 3 (TPSEP + Z-100), and group 4 (TPSEP + Concise Orthodontic) were of 6.43, 4.61, 4.74, and 0.02, respectively. Group 1 was statistically superior to other groups (P < .05), but there was no statistically significant difference between groups 2 and 3 (P > .05), although both were statistically superior to group 4 (P < .05). According to the ARI evaluation, most of the failures involved the bracket/composite interface (groups 1 and 2) as well as the enamel/composite interface (groups 3 and 4). The Transbond XT conventionally bonded showed better adhesion results than Transbond XT, Z-100, and Concise Orthodontic after using Transbond Plus Self-Etching Primer.

Assessment of the nasolabial angle in young Brazilian black subjects with normal occlusion

Black individuals present craniofacial characteristics which differ from those of other races, especially the white race, whose cephalometric analyses are usually considered as the standard in routine orthodontic diagnosis and treatment planning. Further studies are therefore needed to enable more accurate and specific diagnoses for this ethnic group. The present study was conducted in order to assess average values for the nasolabial angle in young Brazilian black individuals with normal occlusion, and to assess the occurence of sexual dimorphism. Thirty-six lateral skull, extraoral radiographs from Brazilian black individuals were selected from the archives of the Scientific Recordings Department, Orthodontics Graduate Program, School of Dentistry of Piracicaba, State University of Campinas (UNICAMP). The patients' ages varied from 10 to 14 years, they presented normal occlusion upon clinical examination, and had not been submitted to orthodontic treatment. The cephalometric landmarks from which the nasolabial angle was obtained and measured were traced by a single researcher. Statistical analysis and evaluation of the results led to the conclusion that the nasolabial angle of young Brazilian black individuals is sharper, i.e., the soft tissue profile is more protruded. The average value for the whole sample was 88.14 degrees +/- 12.52 degrees. The nasolabial angle was statistically smaller among females (p < 0.05), demonstrating the occurrence of sexual dimorphism.

Analysis of the coefficient of variation in shear and tensile bond strength tests

The coefficient of variation is a dispersion measurement that does not depend on the unit scales, thus allowing the comparison of experimental results involving different variables. Its calculation is crucial for the adhesive experiments performed in laboratories because both precision and reliability can be verified. The aim of this study was to evaluate and to suggest a classification of the coefficient variation (CV) for in vitro experiments on shear and tensile strengths. The experiments were performed in laboratory by fifty international and national studies on adhesion materials. Statistical data allowing the estimation of the coefficient of variation was gathered from each scientific article since none of them had such a measurement previously calculated. Excel worksheet was used for organizing the data while the sample normality was tested by using Shapiro Wilk tests (alpha = 0.05) and the Statistical Analysis System software (SAS). A mean value of 6.11 (SD = 1.83) for the coefficient of variation was found by the data analysis and the data had a normal distribution (p>0.05). A range classification was proposed for the coefficient of variation from such data, that is, it should be considered low for a value lesser than 2.44; intermediate for a value between 2.44 and 7.94, high for a value between 7.94 and 9.78, and finally, very high for a value greater than 9.78. Such classification can be used as a guide for experiments on adhesion materials, thus making the planning easier as well as revealing precision and validity concerning the data.

Esporão lingual colado Nogueira®: tratamento coadjuvante da deglutição atípica por pressionamento lingual

Este artigo tem como objetivo apresentar à comunidade ortodôntica um novo material denominado esporão lingual colado Nogueira®. Este material foi idealizado e desenhado com base nos princípios dos esporões tradicionais, sendo desenvolvido e produzido pela companhia Abzil para realização de uma pesquisa clínica no tratamento da deglutição atípica por pressionamento lingual. Este material pode ser aplicado tanto no arco superior como no inferior, depois de realizado o diagnóstico da posição lingual atípica. São apresentados três casos clínicos de pacientes tratados com o referido sistema associado ao tratamento ortodôntico. Os três pacientes submeteram-se ao exame de eletromiografia (EMG), antes e 10 meses após o inicío do tratamento para avaliação neuromuscular. Os músculos avaliados foram o masseter, temporal anterior, digástrico anterior e orbicular inferior da boca, avaliando a atividade muscular (µv) e o tempo de contração muscular (s) durante a deglutição. Os resultados obtidos foram uma melhor relação interarcos tanto nos sentidos ântero-posterior, vertical e transversal com o uso dos aparelhos ortopédicos e ortodônticos utilizados e melhora nas funções de deglutição, fonação e repouso, isto provavelmente ocorreu porque não foram encontrados nenhum sinal ou ferimento na língua. Em relação à Eletromiografia (EMG) houve uma redução nos potenciais (µv) dos músculos peribucais digástrico anterior e orbicular inferior da boca com aumento do seu tempo de contração (s) resultando em uma menor atividade protrusiva da língua durante a deglutição.

Craniofacial analysis of the Tweed Foundation in Angle Class II, division 1 malocclusion

This study has defined the cephalometric values of the Craniofacial Analysis of the Tweed Foundation for a sample of Brazilian subjects. The sample consisted of 211 cephalometric radiographs from subjects aged 12-15, which were divided into two groups: Class II group, with 168 lateral teleradiographs (cephalograms) of white Brazilian subjects, with Angle Class II, division 1 malocclusion, of both genders (82 males and 86 females); and the Control Group, with 43 lateral teleradiographs (cephalograms) of subjects whose occlusion was clinically excellent, and also of both genders (21 males and 22 females). The teleradiographs were selected from the files of the Department of Orthodontics, School of Dentistry of Piracicaba, State University of Campinas, previously to the orthodontic treatment. The results demonstrated no sexual dimorphism for each group, as attested by the Student's t-test. The exploratory analysis (± 0.5 standard deviation) enabled the tolerance limits to be determined and a Craniofacial Analysis Table to be constructed using the respective cephalometric intervals. In addition, the difference between the two groups was not statistically significant according to the maxilla position. The maxilla was in a good position in relation to the cranial base. On the other hand, the mandible was retruded in relation to the cranial base in the Class II cases. The skeletal pattern was not defined because only the Facial Height Index (FHI) showed a vertical pattern in Class II subjects, while the Y Axis, SN.PlO, SN.GoMe and FMA values did not show any statistically significant difference between the groups. The Class II division 1 subjects showed lower incisors more labially tipped and a convex facial profile.

Clinical and microbiologic changes after removal of orthodontic appliances

The goal of this study was to evaluate the clinical and microbiological factors associated with orthodontic appliances during an episode of gingival inflammation and the impact of appliance removal on periodontal health. This prospective study included 10 patients, aged 12 to 20 years, with clinical signs of gingival inflammation at the final phase of orthodontic treatment (appliance removal). Plaque index, gingival index, and probing depth were evaluated, and microbiological samples were collected from teeth 16, 11, and 26 at 2 times: during the gingival inflammation (baseline) and 30 days after the removal of the appliance and professional prophylaxis. Polymerase chain reaction analysis was used to detect Porphyromonas gingivalis, Bacteroides forsythus, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Prevotella nigrescens. A statistically significant improvement of the plaque and gingival indexes was seen, as well as a reduction in probing depth (P <.05). Periodontal pathogens were associated with gingival inflammation during orthodontic treatment. The improvement in periodontal health at 30 days was concomitant with a reduction of sites positive for A. actinomycetemcomitans and B. forsythus (P <.05). Periodontal pathogens associated with gingival inflammation during orthodontic treatment can be significantly reduced by orthodontic appliance removal and professional prophylaxis.

Evaluation of immunologic profile in patients with nickel sensitivity due to use of fixed orthodontic appliances

The aim of this study was to develop a new approach to testing the impact of nickel antigen on in vitro cell-proliferation assay, to identify adverse reactions to casting alloys among orthodontic patients. Cell-proliferation assay in vitro was used as the basic methodology to assess the influence of such variables as source of nickel antigen, type of serum used to supplement the culture medium, and number of cells in the culture. We selected 35 orthodontic patients who were classified as nickel sensitive and non-nickel sensitive, based on their clinical records. Our results showed that hexahydrated nickel sulfate at 10 microg/mL, 10% of autologous sera, and 2 x 10(5) cells was the best condition for inducing the most marked nickel proliferation response in vitro. This optimized method was able to distinguish nickel-sensitive from non-nickel-sensitive dental patients and also to discriminate those with positive skin tests. Our data suggest that continuous exposure to nickel casting alloys might lead to oral tolerance mechanisms that modulate nickel sensitivity, as evidenced by the lower cell proliferation index in patients undergoing orthodontic treatment over 24 months. Finally, our findings demonstrated a known nickel-induced type 2 immune response and a marked lack of type 1 immunity (interferon gamma) as the hallmarks of nickel-sensitive patients. Further studies are needed to clarify the major cell phenotype associated with this type 2 immune response and the lack of type 1 immunity observed in nickel-sensitive people.