Alignment Efficiency and Coating Durability of Aesthetic Archwires

Randomised Controlled Trial of the Alignment Efficiency and Coating Durability of Aesthetic Archwires

This study investigates the efficiency of orthodontic aesthetic archwires which are coated with tooth-colored materials and the durability of the coatings after being used. Theoretically, the coatings provide excellent aesthetics throughout treatment and faster tooth alignment. However, from our clinical experience, these claims are the opposite. Cracks and ruptures as well as archwire fractures have been noted. Therefore, it is presumed that the aesthetic archwires may not be any different from the conventional uncoated archwires.

The development of superelastics nickel titanium (SE NiTi) has overcome problems with previous aligning archwires. This archwire is deemed to be the gold standard aligning archwire for Straight Wire® system due to its shape memory effect, high elasticity and low permanent deformation which delivers continuous force for orthodontic tooth alignment. The only drawbacks of this wire type are it is expensive, have high frictional resistance (Kapila et al., 1990) and is associated with hypersensitivity reaction in nickel allergic patients (Bass et al., 1993).

Development of teflon or polytetrafluoroethylene (PTFE) which is anti-adherent and possesses aesthetic property had been used as orthodontic bracket, archwire and ligature coating. This polymer consists of synthetic fluorine-containing resin or epoxy resin composed mainly of polytetrafluoroethylyene to simulate tooth colour. The polymeric chain with good mechanical stability had been shown to reduce the frictional resistance between bracket-archwire interface and when used as archwire ligature (Farronato et al., 2012, De Franco et al., 1995). PTFE-coated brackets were reported to minimise the formation of biofilm during treatment which can reduce the risk of enamel decalcification (Demling et al., 2010). Furthermore, the coated aesthetic archwires have potential to obviate any allergic reaction during orthodontic treatment in patients with known hypersensitivity to nickel alloy.

Manufacturers have claimed that the aesthetic archwires available in the market have good color stability (remains unchanged for 6 to 8-week duration), good coating durability and low friction, allowing faster tooth movement. However, to our experience, these claims are the opposite.

As these aesthetic archwires are much more expensive than the conventional superelastic nickel titanium, it is therefore important to establish a clinical data to allow clinicians and patients to make a justifiable choice on treatment and develop further research in this area.

Inclusion Criteria:

• Patient aged 11 years old and above in permanent dentition with all teeth from upper and lower 6 - 6 are present, tooth apices are closed
• Patients who require complete bond-up with upper and lower pre-adjusted edgewise bracket system, MBT prescription with bracket slot size 0.022"
• Able to give consent* *Assent form is required for children below 18 years of age

Exclusion Criteria:

• Patients with cleft lip and palate and other craniofacial deformities and syndromes
• Patients with medical problems / medications that can influence rate of tooth movement
• Teeth blocked out of the arch / ectopic teeth not allowing bracket placement and ligation at bond-up
• Hypodontia with more than one tooth missing in any quadrant
• Have had orthodontic treatment before