Effect of light-curing units in shear bond strength of metallic brackets: an in vitro study

OBJECTIVES: To determine the influence of the light curing units on the shear bond strength of orthodontic brackets. MATERIAL AND METHODS: Seventy-two premolars were divided into six groups (n=12): Group I: brackets bonded with Transbond and polymerization with halogen light; Group II: Transbond and LED; Group III: Fuji Ortho and halogen light; Group IV: Fuji Ortho and LED; Group V: Fuji Ortho, without acid and halogen light; Group VI: Fuji Ortho, without acid and LED. The groups were tested to shear strength in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by ANOVA and Tukey's test. RESULTS: The composite resin presented higher shear bond strength than the resin-modified glass ionomer cement (p;0.05). CONCLUSION: The shear bond strength was influenced by the material but not by the light-curing unit. The use of LED reduced the experimental time by approximately 60%, with the same curing efficiency

Prevalence of candida spp. in the dental biofilm of fixed orthodontic appliances users

Objetivos: O presente estudo tem como objetivo avaliar a prevalência de Candida spp. em biofilme dentário de usuários de aparelhos ortodônticos fixos (AOF) e relacionar com seus hábitos e características. Materiais e métodos: Foram isolados e identificados cepas de Candida em amostras de saliva em indivíduos usuários de AOF com presença de biofilme microbiano e indivíduos usuários de AOF mas sem presença de biofilme (grupo controle), a partir do cultivo em laboratório. Resultados: Neste estudo foram analisadas 108 amostras de indivíduos com biofilme, e 51 indivíduos no grupo controle. Das 108 amostras analisadas, 52 (48,1%) foram negativas para o gênero Candida e 56 (55,2%) foram positivas, sendo que em oito pacientes foram isolados duas espécies de Candida, quatro pacientes com C. albicans e C. krusei, um com C. albicans e C. tropicalis, um com C. albicans e C. glabrata, um com C. tropicalis e C. glabrata e um com C. tropicalis e C. krusei. No grupo controle 33,3% apresentaram isolamento de Candida, mesmo não apresentando biofilme. Conclusão: Foram detectadas espécies de Candida patogênicas e intrinsicamente resistentes aos convencionais antifúngicos, ressaltando a importância do diagnóstico micológico para um tratamento adequado das infecções causadas por este grupo de fungos presentes na cavidade oral dos indivíduos.Objectives: This study aims to evaluate the prevalence of Candida spp. in dental plaque of users of fixed orthodontic appliances (FOA) and relate to their habits and characteristics. Materials and methods: We isolated and identified strains of Candida in saliva samples from individuals using FOA with the presence of microbial biofilm and individuals without the presence of biofilm (control group) in the laboratory cultivation. Results: We analyzed 108 samples from individuals with biofilm and 51 individuals in the control group. Of the 108 samples analyzed, 52 (48.1%) were negative for Candida and 56 (55.2%) were positive, with eight patients were isolated two species of Candida, four patients with C. albicans and C. krusei, with one C. albicans and C. tropicalis, with one C. albicans and C. glabrata, with one C. tropicalis and C. glabrata and with one C. tropicalis and C. krusei. In the control group 33.3% had isolated Candida, even showing no biofilm. Conclusion: Were detected and pathogenic Candida species intrinsically resistant to conventional antifungal agents, emphasizing the importance of mycological diagnosis for appropriate treatment of infections caused by this group of fungi present in the oral cavity of individuals

Enamel surface evaluation after bracket debonding and different resin removal methods

OBJECTIVE: To assess enamel surface under scanning electron microscopy (SEM) after resin removal and enamel polishing procedures following brackets debonding, as well as compare the time required for these procedures. METHODS: A total of 180 deciduous bovine incisors were used. The enamel surface of each tooth was prepared and brackets were bonded with light cured Transbond XT composite resin. Brackets were removed in a testing machine. The samples were randomized and equally distributed into nine groups according to the resin removal and polishing technique: Group 1, 30-blade tungsten carbide bur in high speed; Group 2, 30-blade tungsten carbide bur in high speed followed by a sequence of 4 Sof-lex polishing discs (3M); Group 3, 30-blade tungsten carbide bur in high speed followed by Enhance tips (Dentsply). All groups were subdivided into (a) unpolished; (b) polished with aluminum oxide paste; and (c) polished with water slurry of fine pumice. Subsequently, the enamel surface was assessed and statistical analysis was carried out. RESULTS: There were statistically significant differences in enamel roughness and removal time among all groups. Groups 3a, 3b and 3c appeared to be the most efficient methods of removing resin with low damages to enamel. Groups 2a, 2b and 2c were the most time consuming procedures, and Group 2a caused more damages to enamel. CONCLUSION: The suggested protocol for resin removal is the 30-blade tungsten carbide bur in high speed followed by Enhance tips and polishing with aluminum oxide paste. This procedure seems to produce less damages and is less time consuming

Assessment of the dimensions and surface characteristics of orthodontic wires and bracket slots

OBJECTIVE: The purpose of this study was to evaluate the dimensions and surface characteristics of orthodontic wires and bracket slots of different commercial brands. METHODS: Thirty metallic brackets (0.022 x 0.028-in and 0.022 x 0.030-in) were divided in three groups: DYN/3M group = Dyna-Lock, 3M/Unitek (stainless steel, or SS); STD/MO group = Slim Morelli (SS); and Ni-Free/MO group = Slim Morelli (Ni-Free). The stainless steel wires (0.019 x 0.025in) were divided into two groups: MO group = Morelli; and 3M group = 3M/Unitek. The bracket and wire measurements were done by two methods: (a) Surface Electron Microscopy (SEM), and (b) Profile projection. The surface analysis was done qualitatively, based on SEM images and/or by a rugosimeter. The quantitative results were analyzed by ANOVA with Tukey's test (p < 0.05) and Student's t test. RESULTS: A significant difference in the dimensions of slots was observed, and the NiFree/MO group showed the greatest changes when compared to the other groups. The analysis of surface topography of the brackets indicated greater homogeneity of the metallic matrix for DYN/3M and STD/MO groups. As for the dimensions of the wires, groups showed statistically different mean heights. CONCLUSIONS: It was concluded that wires and brackets slots can present altered dimensions, which might directly and unintentionally affect the planned tooth movement

Assessment of force decay in orthodontic elastomeric chains: An in vitro study

Introduction: Elastomeric materials are considered important sources of orthodontic forces. Objective: To assess force degradation over time of four commercially available orthodontic elastomeric chains (Morelli, Ormco, TP and Unitek). Methods: The synthetic elastics were submerged in 37 oC synthetic saliva and stretched by a force of 150 g (15 mm - Morelli and TP; 16mm - Unitek and Ormco). With a dynamometer, the delivered force was evaluated at different intervals: 30 minutes, 7 days, 14 days and 21 days. The results were subjected to ANOVA and Tukey's test. Results: There was a force decay between 19% to 26.67% after 30 minutes, and 36.67% to 57% after 21 days of activation. Conclusions: TP elastomeric chains exhibited the smallest percentage of force decay, with greater stability at all time intervals tested. Meanwhile, the Unitek chains displayed the highest percentage of force degradation, and no statically significant difference was found in force decay between Ormco and Morelli elastomeric chains during the study period