Effect of Covering Orthodontic Brackets With Calcium Phosphate Film on the Hardness of Bovine Enamel Undergoing In Vitro Demineralization in vitro
Name: Luiz Felicio Fernandes Louzada Fiorotti
Type: MSc dissertation
Publication date: 26/03/2019
Advisor:
Name |
Role |
|---|---|
| Juliana Malacarne Zanon | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| Américo Bortolazzo Correr | External Examiner * |
| Juliana Malacarne Zanon | Advisor * |
| Liliana Aparecida Pimenta de Barros | Internal Examiner * |
Summary: Despite the widespread use of fixed orthodontic appliances to correct malocclusions, White spot lesion (WSL) is routinely adverse effects associated with this treatment modality. Thus, the aim of this in vitro study was to evaluate the calcium leaching ability of calcium phosphate (CaP) thin film coated orthodontic brackets in distilled water, as well to evaluate the surface Vickers nanohardness (VHN) of experimental bracket coated with calcium phosphate (CaP) after demineralizing challenge. For this, original manufacturer's orthodontic brackets were used as control (n=15) and fifteen were coated with CaP film by electrodeposition. The film was characterized morphologically by scanning electron microscopy (SEM) and dispersive energy spectroscopy (EDS) for elemental analysis. Twenty-eight coated brackets were stored in distilled water for 7, 15 and 30 days and analyzed at 7, 15 and 30 d for calcium leaching. Thirty blocks (8 x 10 mm) of enamel, obtained from the vestibular face of healthy bovine incisors and submitted to metallographic polishing, were used. The VHN of bovine enamels was evaluated before and after demineralizing challenge using 50 mN of force, for 15 seconds, in five previously determined peripheral areas. Then, the enamel blocks were divided into 2 groups (n = 15) according to the protocol that was attached to the dental enamel: test group, CaP coated bracket; and control group, manufacturer's original brackets. For the union of the rinses to the bovine bone, the system Transbond XT was used in all the collages. After storage in distilled water at 37 °C for 24 h, the specimens underwent a demineralization process in pH 5.0 solution for 32 hours at 37 °C. Soon after the VHN was remeasured. In the SEM the surface of the coating was amorphous and crystalline, in both structures there is presence of calcium and phosphate, proving the coating. Calcium leaching occurred with greater intensity in 7 d (p <0.05). The group with orthodontic brackets covered with CaP showed lower hardness loss after the demineralization process than the control group (p <0.05). Thus, the coating has been shown to be a means of maintaining bovine enamel hardness after in vitro demineralization.
