Variations in orthodontic bracket retention related to base design. Comparison of foil mesh and anchor pylons brackets

Aim of the study. To compare the shear bond strength of metal brackets with foil mesh (3M, Victory Series), one piece metal brackets (Cannon Ultra) and aesthetic plastic brackets (Cannon Ultra) and to evaluate the sandblasting effect on previously used metal bracket bases regarding their bonding ability. Materials and Methods.A total of seventy human third molars were divided into four groups, and brackets were bonded to the enamel using Transbond XT. After 24 hours of storage, brackets were debonded with Instron Universal Testing Machine® and shear bond strength was recorded. Metal brackets were sandblasted until all visible bonding material was removed from the bracket base and then the bonding procedure and shear bond testing were repeated. Shapiro-Wilk test was used to check normal distribution. Student’s t-test was used to compare the shear bond strength. Results. The shear bond strength of one-piece metal brackets is significantly bigger (18.93MPa) than metal brackets with foil mesh (12.53MPa). Metal brackets in general demonstrate better bonding properties than aesthetic plastic brackets (8.61MPa). There is no statistically significant difference in shear bond strength between new and re-used sandblasted brackets. Conclusions. One-piece brackets with anchor pylons demonstrate better bonding properties but there is a higher risk of enamel damage during debonding of re-used sandblasted brackets.

Surface roughness of three types of modern plastic bracket slot floors and frictional resistance

ABSTRACT Objective: To quantitatively analyze the surface roughness of the slot floors of three types of modern plastic brackets and to measure static frictional force during sliding mechanics in vitro. Materials and Methods: Control groups comprised stainless steel brackets and monocrystalline ceramic brackets. Test groups comprised three types of 0.022-in slot, Roth prescription, plastic, maxillary right central incisor brackets. Test groups included glass fiber-reinforced polycarbonate, filler-reinforced polycarbonate, and hybrid polymer with inserted metal slot brackets. The static frictional resistance caused by sliding movements with an archwire (stainless steel) in vitro was quantitatively analyzed. Both scanning electron microscope and three-dimensional optical surface profiling were used. Results: Scanning electron microscope and three-dimensional optical surface profiler revealed that all as-received brackets had irregular slot floor surfaces, and both irregularity and roughness increased after the archwire sliding test. The ceramic brackets in the control group showed significantly lower surface roughness values and higher frictional values during the archwire sliding test compared with the other brackets. The glass or filler-reinforced plastic brackets exhibited significantly higher static frictional values than the metallic slot type brackets (P < .001). The hybrid polymer with inserted metal slot brackets showed relatively lower surface roughness and frictional values compared with the stainless steel control bracket. Conclusion: Glass or filler-reinforced plastic brackets showed higher frictional resistance than metallic slot–type brackets. A plastic bracket with inserted metal slot may be the best choice among plastic brackets for low frictional resistance and to avoid damage from sliding movements of the archwire.

The effect of two different bracket types on the salivary levels of S mutans and S sobrinus in the early phase of orthodontic treatment

Objective:To determine the difference in the levels of Streptococcus mutans and S sobrinus in stimulated saliva in orthodontic patients with different bracket types (stainless steel and esthetic brackets) using polymerase chain reaction and cultivation method.Materials and Methods:Thirty-two patients, aged 13 to 30 years, were selected following these criteria: 1) orthodontic treatment indication, 2) systemic health, and 3) no tobacco and antibiotic consummation for three months prior to the commencement of the study. Patients were divided into two groups according to the bracket type; 16 patients formed the conventional bracket group (stainless steel brackets), and 16 patients formed the esthetic bracket group (plastic brackets). The levels of S mutans and S sobrinus in stimulated whole saliva samples were collected prior to fixed orthodontic appliance placement (T1) and 12 weeks after placement (T2), as were the Decayed, Missing, and Filled Surface Index (DMFS) and Oral Hygiene Index-Simplified (OHI-S). Mann-Whitney, Wilcoxon, and chi-square tests were used for statistical analysis.Results:Statistical analysis (chi-square test) showed no difference in S mutans and S sobrinus counts among patients with different brackets at either T1 or T2. There was no difference in total bacteria counts after fixed orthodontic appliance placement.Conclusion:The number of colony-forming units of S mutans and S sobrinus in stimulated saliva samples does not seem to be significantly different between patients with stainless steel brackets and patients with plastic brackets.