Summary
This in vitro study examined the effects of toothbrushing with fluoride-containing and fluoride-free toothpastes on the surface roughness of superelastic nickel-titanium (NiTi) orthodontic wires as an indirect indicator of corrosion-related surface degradation. 30 rectangular superelastic NiTi wires (0.019 x 0.025 inch, 20 mm length) were randomly allocated to three groups (n=10): Group 1 (fluoride toothpaste + brushing), Group 2 (fluoride toothpaste, no brushing), Group 3 (fluoride-free natural toothpaste + brushing). Fluoride-containing toothpaste combined with brushing significantly increased NiTi wire surface roughness compared to baseline and to Group 3. This study does not measure heavy-metal contamination in toothpaste products. The nickel signal in this paper refers to nickel in the NiTi orthodontic wire substrate, not nickel contamination of toothpaste formulations. It is catalogued here because it was deposited in the HMI-FILL-0055 toothpaste batch.
Evidence Fitness
Context only for toothpaste metals. The study measures corrosion-related surface changes in NiTi wires exposed to fluoride toothpaste, not heavy-metal content of toothpaste. The nickel-release implications (fluoride-accelerated electrochemical corrosion can increase nickel ion release from NiTi wires) are tangentially relevant to occupational or orthodontic nickel exposure, not to toothpaste heavy-metal contamination as a consumer product category. This source does not contribute to the metals evidence tables on Toothpaste (Cat 2).
Methods (brief)
30 rectangular NiTi wires randomly allocated to three groups (n=10 per group). Group 1: Encident Brackets fluoride toothpaste (1,450 ppm NaF) applied by electric toothbrush (Oral-B iO10, Procter & Gamble) twice daily for 1 minute over 28 days. Group 2: same fluoride toothpaste applied directly without brushing. Group 3: Propolis Dental fluoride-free natural toothpaste applied by electric toothbrush. Wires immersed 24 hours in 20 mL artificial saliva before brushing. Surface roughness (Rz, micrometres) measured using a portable roughness tester (MarSurf PS 10) before and after the 28-day protocol. Statistical analysis: paired Student t-test for within-group comparisons; one-way ANOVA with Tukey post-hoc for between-group comparisons.
Main result: Mean final Rz Group 1 (fluoride + brushing): 2.440 micrometres vs baseline 0.717. Mean final Rz Group 2 (fluoride, no brushing): 1.904 micrometres vs baseline 0.791. Mean final Rz Group 3 (fluoride-free + brushing): 0.828 micrometres vs baseline 0.723 (non-significant increase). Statistically significant intergroup differences post-treatment (p < 0.001): Group 1 > Group 2 > Group 3.
Implications
- Certification: No contribution to toothpaste heavy-metal contamination data or threshold work. Tangential to nickel exposure from orthodontic appliances via a separate pathway (corrosion of NiTi wires by fluoride ions).
- Courses: May be useful as background context in a module on fluoride toothpaste interactions with dental materials.
- App: Not applicable.
Related evidence
None — this source does not carry metals contamination data applicable to the toothpaste wiki page.
Update history
No substantive edit history is available in this build. The full commit record is available in git.