Invisible orthodontics part 3: aesthetic orthodontic brackets

In vitro evaluation of a ceramic bracket with a laser-structured base

BACKGROUND

The purpose of this study was the assessment of shear bond strength (SBS), adhesive remnant characteristics, integrity of the enamel, integrity of Discovery Pearl as well as the integrity of Fascination 2 ceramic brackets following SBS testing.

METHODS

Sixty maxillary first premolars were randomly assigned into two groups. These groups were bonded with their respective brackets. The samples underwent thermocycling (1000 cycles), SBS testing and assessment of the residual adhesive. The statistical analyses used were the independent samples t-test, the Weibull analysis and the chi-square test.

RESULTS

The independent samples t-test for the comparison of the mean SBS resulted in significant differences between Fascination 2 (10.50 ± 2.61 MPa) and Pearl (13.01 ± 2.50 MPa) brackets (p = 0.0003). The results of the chi-square test for ARI demonstrated a significant difference (p = 0.000) between the groups. A higher frequency of ARI scores of 2 and 3 for Pearl brackets existed. Enamel damage and bracket fracturing was not observed.

CONCLUSIONS

The mean bond strength value, the adhesive remnant characteristics, the integrity of the enamel and the ceramic brackets as well as the Weibull analyses outcomes were highly encouraging during this in vitro screening. The way is paved for an in vivo investigation with the Pearl ceramic bracket.

Evaluation of Nanomechanical Properties, Surface Roughness, and Color Stability of Esthetic Nickel-Titanium Orthodontic Archwires

Objectives:

The objective of the study is to evaluate the surface roughness, nanomechancial properties the color stability of three brands of coated (rhodium, epoxy, and Teflon) nickel-titanium (NiTi) esthetic archwires.

Materials and Methods:

Three brands of coated (rhodium, epoxy, and Teflon) esthetic NiTi archwires and three brands of uncoated (NiTi) archwires from the same manufactures were evaluated for the surface roughness, nanomechanical properties, and color stability. The specimens with 20 mm length (n = 5) were cut from the straight buccal segments of the coated and uncoated archwires. The specimens with 20 mm length (n = 10) were subjected to color measurement after immersion in a coffee staining solution. The color measurement was evaluated after 7, 14, 21, and 28 days after immersion in staining solution using color eye 7000 spectrophotometer. The experimental data were analyzed using descriptive statistics, analyses of variance, and Tukey's post hoc test.

Results:

Epoxy (1.517 ± 0.071) and rhodium (0.297 ± 0.015) coated archwires showed the highest and lower value of surface roughness. All the intergroup comparisons showed a significant difference (P < 0.05) in surface roughness except between rhodium and control group (P = 0.998). There were significant differences between control and the experimental groups for both nanohardness and elastic modulus was observed. All the three NiTi-coated esthetic archwires demonstrated trace” (extremely slight change) color changes as measured by the National Bureau of Standards units after 4 weeks of immersion.

Conclusion:

Surface roughness of rhodium-coated archwires was almost similar to that of uncoated wires. Whereas Teflon and epoxy coated archwires showed a significant difference in surface roughness compared to uncoated archwires. Uncoated archwires showed higher nanohardness values compared to the coated archwires. Teflon-coated archwires demonstrated significantly slight color change after 4 weeks of immersion in staining solution.

Comparison of the Stress Strain Capacity between Different Clear Aligners

Background:

The rife use of aesthetic appliance in orthodontic treatment requires the study of the properties of the materials they are made of.

Objective:

The aim of the present study was to evaluate the dimensional stability of clear aligners made of three different materials after the application of in-vivo dynamic stress and in-vitro static stress.

Methods:

Three different aligners made of different materials (PET-G; PET; SmartTrack®), prepared on the dental arch of the same patient, were tested. For each material, three aligner samples were manufactured: one to be used in-vivo, one to be tested in-vitro, and one to be used as a control.

To evaluate the effects of the dynamic stress produced in-vivo, each aligner was worn by a single patient 22 hours per day, followed by a wash-out period of two weeks. To evaluate the effects of static stress, each aligner was exposed to the in-vitro continuous force of 50N. The tested and control aligners were scanned, then linear measurements were taken to evaluate their dimensional stability after different types of stresses.

Results:

PET seems to have the lowest percentage of deformation; PET-G and SmartTrack® showed a reduced deformation going from the posterior to the anterior area. The contact with human saliva induces a greater deformation.

Conclusion:

Different materials show different behavior following application of static stresses and dynamic stresses in the oral cavity. PET showed the highest dimensional stability.