Evaluation of Physical Properties of Silver Coated and Uncoated NiTi Arch Wires: An Invitro study

Maintenance of oral hygiene is mandatory for patient who uptake fixed orthodontic treatment Fixed appliance has various attachments and retentive plaque forms the nidus for colonization of microorganism with the risk of white spot lesion .To reduce this bacterial count in the plaque and prevent such type of carious lesion, silver known to have anti-bacterial property is added in dental materials. AIMS AND OBJECTIVES: To compare the load deflection rate and surface roughness of silver coated and uncoated NiTi arch wires. 1. To evaluate the load deflection rate of silver coated and uncoated round and rectangular NiTi wire using Universal testing machine. 2. To evaluate the surface roughness of silver coated and uncoated round and rectangular NiTi wires using three dimensional optical profilometer. 3. To compare the load deflection rate and surface roughness of silver coated round and rectangular wire with uncoated round and rectangular NiTi wire of same dimension. MATERIALS AND METHODS: Surface modification of nickel titanium orthodontic wire with silver will be carried out by thermal evaporation method. It produce thin homogenous, uniform pure film coating on metal. Pure silver (99.9%) is used to obtain thin coating on the wires. Silver is heated through its vaporization temperature in a closed chamber and was allowed to pass through a valve which can be controlled according to desired thickness. In our study 10-nm thick silver film will be coated on orthodontic wires to avoid change in its dimensions. The load deflection characteristics of specimens for each group will be evaluated using three- point bending test and the test performed at room temperature, Testing will be done under universal testing machine INSTRON. A specially designed fixture with two supports 14 mm apart will be used. The striker is attached to the upper movable head of the Instron machine. The tip of the striker is the centre of the test-wire span. The crosshead speed for loading and unloading is 1 mm per minute. The mid portion of the wire should be deflected. The loading and unloading values for each sample should be recorded at 1, 2, and 3mm deflection. Loading value and unloading value for each sample will be registered and the results will be analyzed. The three-dimensional (3D) surface profilometry analysis was performed to assess the surface roughness of the arch wires. The average absolute deviation of the surface (Sa) was assessed because of the importance of amplitude parameters. A surface profilometer (Talysurf PGI 1240) was used in this study. An area of 0.24mm2 of each coated and uncoated surface was measured. The wire was placed on the worktop and surface tip was positioned on the wire followed the profile of the surface. The mean roughness of each specimen was measured. Data were directly transferred to the connected personal computer with ultra-system software. STATISTICAL ANALYSIS: Load deflection rate of silver coated 0.016 round and 0.016x 0.022 rectangular Niti wire and uncoated 0.016 round and 0.016x 0.022 rectangular Niti wire were compared using independent sample t test with p value of <0.05. CONCLUSION: The load deflection rate of 0.016 and 0.016X0.22 silver coated and uncoated NiTi archwire showed a statistically insignificant difference. Silver coated rectangular Niti archwire had same mechanical load deflection property as that of uncoated superelastic Niti, thus maintaining its superelastic nature. The surface roughness of 0.016 silver coated and uncoated NiTi archwire showed a statistically insignificant difference, The surface roughness of 0.016x0.022 silver coated and uncoated NiTi archwire showed a statistically significant difference, stating reduced surface roughness in rectangular silver coated Niti archwire, which is suggestive of its anti-adherent and antimicrobial effect.