The influence of cigarette smoke on colour stability and friction property of aesthetic orthodontic wires-In vitro study.

OBJECTIVE: To evaluate the colour stability and friction property of aesthetic orthodontic wires when exposed to cigarette smoke. MATERIALS AND METHODS: Forty-eight samples of aesthetic orthodontic wires (0.019″×0.025″) were allocated to three experimental groups according to their brand (n=8): GAD (Aditek™); GTP (TP Orthodontics™); GRM (Rocky Mountain™) and their respective control groups (GC) (n=8). Samples were exposed to 2 cycles of smoke in a hermetic chamber while GCs were stored in artificial saliva at 37°C. Colour analysis (CIEL*a*b* colour space and NBS units) was performed on 5mm wire segments with the Vita Easyshade Compact spectrophotometer. The friction analysis was performed in a universal test machine, in segments of 5cm wires tied to ceramic brackets with maximum values recorded in N/cm. The comparison between groups was performed with the ANOVA/Tukey test (a=0.05) and the effect of the time evaluated with ANOVA-MR with Bonferroni correction (a=0.016). RESULTS: GTP and GRM did not show significant colour and friction property variations and did not differ from GC during the study (P>0.05). However, GAD was significantly sensitive to colour changes (T1-T0-L*: -4.09±1.06; a*: 2.25±0.39; b*: 1.70±0, (T2-T0-L* 0.66±0.92; a*: 2.76±0.35) and friction (T2-T0: 2.07±1.00N/cm) (P<0.016). CONCLUSION: Exposure to cigarette smoke may alter the mechanical and optical properties of aesthetic orthodontic wires.

Assessment of exogenous pigmentation in colourless elastic ligatures.

INTRODUCTION: The aim of this study was to evaluate colour alteration of transparent elastic ligatures submitted to exogenous pigmentation. METHODS: Forty test specimens were divided into eight groups corresponding to one commercial brand with five test specimens in each group. The test specimens were immersed into coffee and black tea solutions with the purpose of assessing colour alteration using a portable digital spectrophotometer (Vita Easyshade Compact). The surfaces of the ligatures under scanning electron microscope (SEM) at ×30, ×150 and ×20,000 magnification were evaluated with the purpose of observing the differences in porosity of the ligatures. The Kolmogorov-Smirnov test for normality was applied followed by the one-way analysis of variance (one-way ANOVA) and the level of significance adopted was 95%. RESULTS: All the groups showed modified initial colour that was perceptible to the human eye. The brand that showed greater colour alteration, in comparison with its initial colour, was the American® pearl elastic ligature and the ligatures that presented the smallest colour variation were the Ortho-Organizer®. The surface evaluations of the ligatures showed differences with regard to the topography evidencing more porosity in the ligatures that showed greater staining. CONCLUSION: The group that changed colour significantly was the one that presented the highest porosity, and the brand that was the least altered was the one that showed the lowest porosity.

Asymmetric headgear for differential molar movement: a study using finite element analysis.

OBJECTIVE: To compare the effects of four different asymmetric headgear systems. DESIGN: A mathematical method for three-dimensional data called finite element analysis. SETTING: The Orthodontic Department, the Federal University of Rio de Janeiro and the Metallurgical Engineering Department of the Fluminense Federal University. METHODS: Four systems of delivering an asymmetrical force to headgear were studied: using face-bow arms of different lengths, a symmetric face-bow with one of the arms bent outward in relation to the internal arch, a symmetric face-bow used in combination with a transpalatal arch activated to produce an asymmetric force, and a symmetric face-bow with the outer bow soldered to the inner bow on the side where a larger force will be applied. RESULTS: All four systems were effective in promoting asymmetric distal movement of the molars. However, the symmetrical face-bow with the outer bow soldered to the inner bow (system 4) could be used in asymmetric mechanics if the bows are soldered on the opposite side to the proposed distalization. Lateral and occlusal displacing forces were observed in all systems as well as tip-back and rotational movements. CONCLUSION: The simulated computer model used in this investigation suggests that a face-bow with a symmetrically soldered joint and arms of equal lengths used in combination with a transpalatal arch is the best headgear option when asymmetric movement of upper molars is desired.

Three palatal arches used to correct posterior dental crossbites.

OBJECTIVE: To assess the force, resilience, and elasticity modulus produced by the Coffin appliance, "W" arch, and quad-helix made with 0.032-inch and 0.036-inch stainless steel wire. MATERIALS AND METHODS: Two groups of 15 arches were made as Coffin appliances, two groups of 15 arches were made as "W" arches, and two groups of 15 arches were made as quad-helices. One group of each appliance was formed in 0.032-inch and one group in 0.036-inch stainless steel wire. All arches (6 groups of 15 each) were submitted to compression trials in the mechanical testing machine EMIC DL-10000, simulating 5-, 8-, 10-, and 12-mm activation. The force and resilience means received a one-way ANOVA statistical analysis. RESULTS: The results showed that the mechanical properties depended on the shape of the appliance, the diameter of the wire used, and the amount of activation. CONCLUSIONS: The three appliances assessed produce appropriate forces for orthodontic treatment as long as they are correctly planned during clinical application.

Applicability of three tooth size prediction methods for white Brazilians.

The objectives of this study were to evaluate the applicability of the methods of Moyers; Tanaka and Johnston; and Bernabé and Flores-Mir to Brazilian individuals and to propose new regression equations using the lower four permanent incisors as predictors for the sum of the widths of the lower permanent canine and premolars. Five hundred dental study casts (250 male and 250 female white patients) were used. The methods of Moyers and Tanaka and Johnston were tested on a sample consisting of 240 female and 223 male patients. The method of Bernabé and Flores-Mir and the new regression equations were based on the complete sample. At the 50th and 75th percentile levels, Moyers' tables tended to underestimate the actual sum of the lower permanent canine and premolars for male and female samples, with statistically significant differences. Although the same statistical significant differences were found when Tanaka and Johnston's and Bernabé and Flores-Mir's methods were used, these differences were not clinically relevant. The new regression equations proposed demonstrate similar correlation and determination coefficients to those found in other studies based on the lower four permanent incisors as predictors. Validating studies (based on similar samples) must be conducted to confirm the applicability and precision of the proposed new regression equations.

Metallic brackets bonded with resin-reinforced glass ionomer cements under different enamel conditions.

OBJECTIVE: To assess the shear bond strength of metallic orthodontic brackets bonded with either Fuji Ortho or Ortho Glass LC resin-reinforced glass ionomer cements to enamel surfaces under different conditions, namely, enamel without etching, enamel conditioned with 37% phosphoric acid and enamel conditioned with Transbond Plus Self Etching Primer (TPSEP). MATERIALS AND METHODS: One hundred and five bovine inferior incisors were divided into seven groups (n = 15). In group 1 (control) Transbond XT was used according to the manufacturer's recommendations. In groups 2, 3, and 4 all using Fuji Ortho LC, the brackets were bonded, respectively, to enamel nonetched, enamel etched with 37% phosphoric acid, and enamel etched with TPSEP. In groups 5, 6, and 7, the bonding was performed using Ortho Glass LC under the same enamel conditions observed in the other experimental groups. After 24 hours, shear bond strength tests were performed for all samples at a crosshead speed of 0.5 mm/min. RESULTS: The results (MPa) showed no statistically significant difference between groups 1, 3, and 4 (P > .05). However, such groups were statistically superior to the others (P < .05). No statistically significant difference was observed between groups 2, 6, and 7 (P > .05). Group 5 showed the lowest shear strength value, which was also statistically inferior to the other groups (P < .05). CONCLUSIONS: Regardless of the enamel treatment, Fuji Ortho LC yielded shear strength values superior to those from Ortho Glass LC.

Indicações e confecção do arco lingual / Indications and confection of the lingual arch

Os autores relatam a necessidade do conhecimento, pelo clínico geral e odontopediatra, da importância do uso do arco lingual quando indicado. Ressaltam as vantagens da sua utilização e as conseqüências decorrentes por não usá-lo quando indicado