(Super)hydrophobic coating of orthodontic dental devices and reduction of early oral biofilm retention.

This study was designed to apply (super)hydrophobic crosslinked coatings by means of a sol-gel process on the surface of orthodontic devices and investigate the potential effect of these coatings in reducing the early retention of oral biofilm. Two organosilane-based hydrophobic solutions (HSs) were prepared containing hexadecyltrimethoxysilane diluted in ethanol (HS1) or 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane diluted in dimethyl sulfoxide (HS2). Stainless steel plates and ceramic discs were coated with HS1 or HS2 and heated at 150 °C for 2 h for condensation of a crosslinked SiO x network. Organosilane coatings were applied after previous, or no, surface sandblasting. Commercial stainless steel and ceramic brackets were used to evaluate oral biofilm retention after 12 h or 24 h of biofilm growth, using a microcosm model with human saliva as the inoculum. Surface roughness analysis (Ra, µm) indicated that sandblasting associated with organosilane coatings increased roughness for stainless steel brackets only. Analysis of the water contact angle showed that the stainless steel surface treated with HS1 was hydrophobic (~123°), while the ceramic surface treated with HS2 was superhydrophobic (~155°). Biofilm retention after 24 h was significantly lower in groups treated with hydrophobic coatings. An exponential reduction in biofilm accumulation was associated with increased water contact angle for both stainless steel and ceramic at 24 h. Application of (super)hydrophobic coatings on the surface of stainless steel and ceramic orthodontic devices might reduce the retention of oral biofilm.

Influence of whitening and regular dentifrices on orthodontic clear ligature color stability.

OBJECTIVES: This study evaluated the effect of brushing orthodontic clear ligatures with a whitening dentifrice containing a blue pigment (Close Up White Now, Unilever, London, UK) on their color stability, when exposed to a staining agent. MATERIALS AND METHODS: Ligatures from 3M Unitek (Monrovia, CA, USA) and Morelli (Sorocaba, SP, Brazil) were tested. Baseline color measurements were performed and nonstained groups (control) were stored in distilled water whereas test groups were exposed for 1 hour daily to red wine. Specimens were brushed daily using regular or whitening dentifrice. Color measurements were repeated after 7, 14, 21, and 28 days using a spectrophotometer based on the CIE L*a*b* system. RESULTS: Decreased luminosity (CIE L*), increased red discoloration (CIE a* axis), and increased yellow discoloration (CIE b* axis) were generally observed for ligatures exposed to the staining agent. Color variation was generally lower in specimens brushed with regular dentifrice, but ligatures brushed with whitening dentifrice were generally less red and less yellow than regular dentifrice. The whitening dentifrice led to blue discoloration trend, with visually detectable differences particularly apparent according to storage condition and ligature brand. CONCLUSIONS: The whitening dentifrice containing blue pigment did not improve the ligature color stability, but it decreased yellow discoloration and increased a blue coloration. CLINICAL SIGNIFICANCE: The use of a whitening dentifrice containing blue pigment during orthodontic treatment might decrease the yellow discoloration of elastic ligatures.

Impact of bracket displacement or rotation during bonding and time of removal of excess adhesive on the bracket-enamel bond strength.

OBJECTIVE: This study investigated the the influence of bracket displacement or rotation during fixation and the time of excess adhesive removal from around the bracket on bond strength to enamel. METHODS: Stainless steel brackets were bonded to the buccal faces of bovine incisors using Transbond XT® adhesive resin. The teeth were divided into five groups (n = 20). In the control group, no displacement or rotation of the bracket was carried out. In the Displac-A group, excess adhesive was removed after the bracket was displaced 2 mm incisally. In the B-Displac group, excess adhesive was removed before the bracket was displaced incisally. In the Rotat-A group, excess adhesive was removed after the bracket was rotated 45°. In the B-Rotat group, excess adhesive was removed before the bracket was rotated. Photoactivation was carried out on the lateral sides of the bracket. A shear test was conducted 10 min after fixation using a knife-edged chisel. Bond strength data were analysed using ANOVA and Fisher's test (5%). The adhesive remnant index (ARI) was scored under magnification. ARI data were analysed using the Kruskal-Wallis test (5%). RESULTS: No significant differences were detected among the Control, Displac-A, Rotat-A and B-Rotat groups. The B-Displac group showed lower bond strength than all of the other groups, except Displac-A. No significant differences were observed in ARI scores across groups. CONCLUSIONS: Displacements of the brackets during fixation did not seem to affect the enamel bond strength when excess adhesive is removed after the final positioning of the bracket.

Color stability of five orthodontic clear elastic ligatures.

AIM: In this study the color stability of five commercially available orthodontic clear elastic ligatures daily exposed to a staining agent (red wine) was investigated. METHODS: The commercial brands tested were 3M Unitek, Abzil, American Orthodontics, Dentsply GAC, and Morelli. Baseline color readings (Commission Internationale de l'Eclairage [CIE] L*a*b* parameters) of 20 ligatures for each brand were carried out using a spectrophotometer. The ligatures were divided in two groups (n = 10): one group remained immersed in distilled water (control) throughout the period, while the other group was daily exposed to red wine (1 hour of immersion). Immersion media were daily renewed. Successive color readings were carried out after 7, 14, 21, and 28 days, and the chromatic variations calculated. Color variation data were analyzed by two-way repeated measures analysis of variance and Student-Newman-Keuls test (P < .05). RESULTS: Storage in water increased staining until 14 days, and color receded after this period, irrespective of the brand. After 28 days of immersion in water, no significant difference among the commercial brands was observed. For the groups exposed to red wine, a significant increase in staining over the course of time was detected, irrespective of the brand. Ligatures from GAC and Morelli showed higher staining than the other materials, irrespective of the evaluation time. Ligatures from 3M Unitek and American generally showed lower pigmentation than the other brands. CONCLUSION: Exposure to a staining agent, cumulative exposure time, and commercial brand are factors that influence the color stability of clear elastic ligatures.

Influence of water concentration on the etching aggressiveness of self-etch primers to ground primary enamel.

PURPOSE: The purpose of this study was to investigate the influence of water concentration in self-etch primers on their etching aggressiveness to ground primary human enamel. METHODS: Five hydroxylethyl methacrylate/glycerol dimethacrylate phosphate-based experimental self-etch primers with the same pH (1.1) and different water concentrations (0%, 5%, 10%, 20%, or 40%) were formulated. The enamel of primary molars was flattened, and the primers were applied vigorously for 30 seconds. The etching morphology was assessed via scanning electron microscopy. Thirty-seven percent phosphoric acid gel was tested as a positive control. RESULTS: Increasing etching aggressiveness was associated with increased water content. The etching potential of the anhydrous primer was marginal to none. Primers with 5% and 10% water concentration showed similar etching potentials, producing slight enamel demineralization. The primer with 20% water concentration produced removal of crystals within and around the enamel prisms, with the outline of the prisms being clearly visible. The aggressiveness of the primer with 40% water concentration was more pronounced, with generalized porosity involving the center and periphery of the prisms, with vast surface irregularity. The etching pattern of the phosphoric acid gel was more pronounced than the primer with 20% water concentration, but less aggressive than the primer with 40% water concentration. CONCLUSION: Water content has a significant role on the aggressiveness of self-etch primers applied to the ground primary enamel.