Effects of salivary pH on coating durability of two different aesthetic archwire coatings under a simulated intraoral environment

Abstract

Objectives This study compared the effects of normal salivary pH, and acidic pH found in patients with poor oral hygiene, on the durability of aesthetic archwire coated with epoxy resin and polytetrafluoroethylene (PTFE). Methods The posterior parts of the archwires were sectioned into 20 mm segments (N = 102) and divided among six groups. Four groups were treated with different pH levels and two served as controls. The specimens were immersed in individual test tubes containing 10 ml of artificial saliva adjusted to a pH of 6.75 or 3.5. The tubes were sealed and stored in a 37 °C water bath for 28 days. After 28 days, the specimens were ligated to brackets embedded in an acrylic block and subjected to mechanical stress using an electronic toothbrush for 210 s. The specimens were photographed, and images were measured for coating loss using AutoCAD® software. Surface morphology was observed using a scanning electron microscope (SEM). Results Significant coating loss ( p < 0.001) was found in the epoxy resin groups, regardless of pH value, but not in the PTFE groups. The acidic pH caused epoxy resin layer coating loss by twice as much as normal pH. SEM revealed existing manufacturing defects on the as-received epoxy resin coating, whereas the retrieved epoxy resin demonstrated rupture, roughness, and coating loss in multiple locations. Significance Epoxy resin coatings demonstrate poor durability in acidic environments. This condition is worsened by the existing manufacturing defects found on as-received archwires. Hence, archwires coated with epoxy resin are not recommended in patients with poor oral hygiene.

Comparison of surface roughness and hardness of three different brands of esthetic coated NiTi archwires: invitro study

“…However upon clinical use, surface roughness was shown to significantly increase in several tested coated archwires including Everwhite archwires [ 21 ]. The epoxy resin coating was reported to be unstable following exposure to saliva in several previous studies [ 15 , 22 – 24 ] ranging from increased surface roughness to tearing and coating loss in multiple locations. This instability, which is manifested clinically as unpleasant discolouration and rupture of the coating layer [ 25 ], can be attributed to the hydrophilic property of resins [ 26 ].…”

In vitro Streptococcus mutans adhesion and biofilm formation on different esthetic orthodontic archwires

“…35,36 Despite this, potentially, under the test conditions used for this study, the surface coating material from this orthodontic wire may have slightly degraded, increasing its roughness and consequently its ability to retain biofilm. 37 It is also possible that the increase in absorbance could have been a consequence of increased stain absorption by the wire coating. Although higher biofilm accumulation on this PTFE coating could indicate an increased risk to develop dental caries, future in vivo studies with these wires are needed to further assess the attraction of pathogens and biofilm accumulation differences as surface changes during placement can have significant changes in biofilm adhesion.…”

Comparison of Cell Viability and Chemical Composition of Six Latest Generation Orthodontic Wires

“…However, even though these protective oxide films are present on the metal surface, metal ions can still be released. Not only is the protective oxide layer susceptible to both mechanical and chemical disruption, but the oxide film can also slowly dissolve as the wire is exposed to oxygen from the surrounding medium [ 37 ].…”

“…Previous studies [ 38 ] reported that the PTFE coating had poor stability owing to the thinner coating layer. Moreover, this deterioration and coating loss exposes the core metal wire, causing absorption of large amounts of hydrogen because the titanium attracts hydrogen and undesirable aesthetic effects such as discoloration and ruptures that appear when the archwires are used clinically [ 37 ]. This results in a gradual change in the mechanical properties that must be considered.…”