Dr. Proffit on Enamel Damage at Debond - New Data

From Cochrane et al. Electron microscopy images of bracket pads. Green is calcium, purple is silicon, orange is phosphorus.

BY WILLIAM R. PROFFIT, DDS, PHD

STUDY SYNOPSIS
This study at the University of Melbourne, Australia, provides new data for the prevalence of enamel damage from debonding brackets, and relates such damage to the type of bracket, the type of adhesive, and the surface preparation of the enamel for bonding. Four groups of brackets and bonding techniques were examined. All brackets were GAC Innovation – either the metal “R” version or the ceramic “C” version. All brackets were bonded and removed in the setting of 5 private orthodontic practices. 437 total brackets from anterior teeth were analyzed.
 
The four in-vivo bracket and bonding protocol combinations were:

1. MEC, metal bracket bonded with etch & rinse + bonding agent (Orthosolo) and composite resin (n=150)
   
2. CEC, ceramic bracket bonded with etch & rinse + bonding agent (Orthosolo) and composite resin (n=126)
   
3. CSEP, ceramic bracket bonded with a self-etching primer (Transbond-Plus Self-Etching Primer after pumice) and composite resin (n= 144)
   
4. CGIC, ceramic bracket bonded with polyacrlic acid etch and resin-modified glass ionomer cement (GIC - Fuji Ortho LC) (n=66).
   

 
Debonding was accomplished for metal brackets with a debonding instrument (444-761 bracket lifter from Unitek) and for ceramic brackets with a debonding plier. Only maxillary canine to canine brackets were collected. The back of each bracket was visualized with scanning electron microscopy at 60 x magnification. An elemental map was made using dispersive x-ray spectrometry to detect calcium, phosphorus, aluminum, and silicon. Calcium and Phosphorus together indicated the presence of enamel that had sheared from the tooth. Areas of bonding material and enamel were mapped, the amount of bonding material was categorized, and bracket fracture was tabulated.
 
  The results:

• 26% of the bracket pads examined had detectable enamel on them.
• Only 4% of all brackets had more than 10% of their surface area covered with enamel, with lateral incisors most likely to be damaged.
• The composite resin-bonded metal brackets and the ceramic GIC bonded brackets were approximately equal (no significant difference) in terms of the presence of enamel on them.
• The ceramic brackets with resin bonding differed significantly, with both a higher percentage of affected teeth and a higher percentage area of enamel present on the brackets.

---

WHAT THE PROFESSOR THINKS
This is a particularly interesting study because it analyzes data from patients treated across several orthodontics clinics, rather than just from laboratory testing. Despite some limitations, clinical orthodontists can use the following points to help inform their practice:

1. The prevalence of enamel damage on debonding is higher than previously reported, but fortunately the damage for most teeth is minor.
2. Major enamel damage on debonding is much more likely with ceramic than metal or composite brackets, apparently because ceramic brackets do not distort as they are removed but the others do. Knowing that, debonding with deliberate distortion of the non-ceramic brackets is preferable.
3. Bonding with a resin-modified glass ionomer cement now provides adequate bond strength to retain brackets when the surface is cleaned with NaOH first, and has been reported to decrease the development of white spots around brackets.
4. Given that fact and the decrease in enamel damage, bonding ceramic brackets with the GIC technique now can be recommended.

 
Article Reviewed: Cochrane NJ, Lo TWG, Adams GG, Schneider PM. Quantitative analysis of enamel on debonded orthodontic brackets. Am J Orthod Dentofac Orthop 152:312-319, 2017.