engleski

Microbiologically induced corrosion: influence of the probiotics on microhardness and surface microgeometry of the orthodontic appliance

Probiotics activity could cause corrosion processes and change mechanical properties of the orthodontic appliances. Microbes could be directly involved in corrosion processes or through activity of their metabolites. The aim of this research was to determine effects of the probiotics on microhardness and surface microgeometry of the archwires comprising orthodontic appliances. Four types of orthodontic archwires were examined: stainless steel, uncoated, rhodium coated and nitrified nickel-titanium (NiTi) (0, 508 x 0, 508 mm). Thermocycling was performed to simulate intraoral conditions, 2500 cycles from 5˚C to 50˚C through first 5 days. After that wires were exposed to artificial saliva with pH 4.8 and artificial saliva with addition of probiotic bacteria Lactobacillus reuteri through 28 days and temperature of the 37±2˚C. Mechanical properties were examined on the unexposed wires and after exposure to the media. Microhardness by Vickers hardness method and surface microgeometry by profilometer, expressed through variables: roughness average (Ra), maximum height (Rz) and maximum roughness depth (Rmax) were measured. RESULTS: Examined media do not change microhardness of the same type of wire. Unexposed stainless steel wire is significantly harder than all NiTi, and rhodium wire is harder then uncoated (p˂0.001). Exposure to the saliva decrease Ra in rhodium coated wire (p=0.015), while exposure to the probiotic decrease Rz in stainless steel (p=0.031). Media do not significantly influence surface microgeometry in nitrified and uncoated wires. There is no difference in surface microgeometry between different types of wires before corrosion, but stainless steel wire has less surface roughness than all NiTi wires (p˂0.001). The same result can be found after probiotic corrosion (p˂0.001). Probiotic doesn't influence the microhardness neither increases microgeometry surface irregularity of the orthodontic archwires.

Orthodontic appliances ; corrosion ; probiotic ; microhardness ; microgeometry

Projekt financiran sredstvima Hrvatske zaklade za znanost "Imunosne i regenerativne implikacije korozije dentalnih materijala u djece i adolescenata" HRZZ-7500