The aim of our study was to determine the wear resistance of vacuum-formed retainers (VFRs) made out of polyethylene terephthalate glycol (PETG), from four different manufacturers (Essix, Leone, Erkodent, Bio-Art), under high load forces (600 N), for 10000 cycles. Forty thermoplastic sheets were divided in four groups, each group consisting of a set of ten sheets from each manufacturer, thermoformed on two matching study models with an ideal occlusion. The Instron 8874 equipment was used to simulate the accelerated wear of VFR surfaces. The surfaces of the VFRs were visually inspected using a KEYENCE VHX-600 digital microscope, but this proved difficult because of the surface shine. 3D models were generated using a GOM industrial laser surface scanner. Several wear areas were identified, having various degrees of roughness, with no evident tear points or perforations. One-way ANOVA analysis showed no statistically significant differences in net mass loss between the four groups.
Our study started from the hypothesis that the gingival volume growth associated with fixed orthodontic treatment appeared during the use of leveling and aligning archwires, without any inflammatory signs, as a result of the mechanical stress and periodontal remodeling during the orthodontic dental movement.We selected and included in the study 35 patients (13 females and 12 males) between 12 and 38 years of age, all suffering from gingival overgrowth, diagnosed during the active treatment with fixed orthodontic appliances (braces). For each patient, two tissue samples were taken: one in the early stages of the lesion, coinciding with the use of leveling and aligning archwires and another in the late stages of the lesion, coinciding with the use of finishing archwires. The samples were taken from the same site in the oral cavity. Out of 35 gingival biopsies taken from patients, 8 cases showed no significant changes in the gingiva, while in the remaining 27 cases, significant changes were found after the histopathological exam.Out of 27 gingival biopsies, 16 cases presented a significantly greater number of T cells. In addition, a greater number of B cells were observed in the granulation tissues than in the gingiva. The relative number of B cells (CD20), T cells and dendritic cells (CD8) has been expressed, both in the early and the late stages of the gingival lesions. Our results revealed that the proportion of T lymphocytes and dendritic cells was greater in the early stages rather than at the late stages. The B cells showed a higher count in the late stages.
Recent assessments show an increase in the incidence of tooth decay. In addition to prophylactic treatments using fluoride and diet focused on low sugar consumption, application of sealing materials to the teeth surfaces is the best protection against the appearance of dental caries on both temporary and permanent teeth.Tooth sealing applied using conventional method, plus the application of adhesive systems can lead to noticeable results over time.An increased thickness of the adhesive layer may lead to microinfiltration and implicitly to a failure of the dental caries protection therapy.Loading the dental adhesive with magnetic nanoparticles and applying it to the surface of the teeth with the help of a the magnetic field attempts to reduce and uniformize the thickness of the adhesive layer, which can lead to a reduced decrease in the occurrence of dental caries under the sealing materials for pit and fissures on the occlusal surfaces.
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