After a long period of web-absence, I am back to share something very interesting that I recently learnt while attending the Congress organized by the Swiss Orthodontic Society and Swiss universities in St. Moritz (such a wonderful mountain town: even more when the sun is kissing the white mountains!).
As a Swiss part-time academic (in Geneva), I rarely meet peers of other Swiss universities. In St Moritz I had the chances to be finally exposed to the research lines of Bale, Bern and Zurich universities. What à thrill. Actually, Swiss academic is cool!
I was especially impressed by the lecture on orthodontic material given by Prof. Eliades, the chairman of Zurich. I actually didn’t even think that there were so much things to learns about evidence & materials! I want to share with you some of the useful tips that I learnt.
Etching
Better static etching (without scratching the etchant around) rather than dynamic -> It leaves bigger and mechanically more retentive island of etched enamel
There’s no sure data on minimal etching time but it seem that 20 to 30 seconds is fine for permanent teeth while a longer time is needed for milk teeth (up to 60 seconds)
There’s no sure data on minimal rinsing time, after etching. It’s suggested the minimal time to remove any visible etchant residual.
Bonding
Do not spread air to dry the bonding -> oxygen inhibits adhesion
Primeless bonding are ideal (from AO or GAC)
Polymerization lamp
It’s useless to buy a super powerful lamp (with claims of 3 to 5 second of polymerization) at the wrong wave length
468 nm is the average wave length where polymerization begins
Led halogen lamps (350 to 500 nm of wave length) are the gold standard
BPA (BisPhenol-A) & resine
BPA is present in the composite of current use
BPA is slowly released by sealants and composite that stay in the mouth (think at fix retainers, but no data are available for an evidence based approach)
BPA is now known to have a feminizing (extrogen like) effect
A big amount of BPA is released during debonding due to grinding of the resin
We should say to our patient to rinse at least a couple times after each debonding and bonding procedure
BPA 1 – 2 – 4 -5 are fine, 3 – 7 are toxic. If possible avoid plastic bottles, anyway.
Debonding
A tooth that has been bonded has structural and color permanent alterations because of the hybrid layer created by the reaction between enamel and adhesive
It can get colored easier than a never bonded tooth
To avoid excessive post-bonding porosity is better to use appropriate burs.
Tungsten carbide 8 blades burs for gross abrasion and 24-30 blades for fine smoothing
When an assistant is pregnant, she shouldn’t perform debonding to avoid inhalation of a big concentration of BPA.
Every operator performing debonding should wear a mask
Air-rotor or red contrangle is better than blue micromotor because it’s faster.
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