LABIAL Indirect Bonding for Orthodontics
Labial IDB as it is often called has existed for a long time. 45 years ago “Silverman and Cohen” first described it and throughout the 70’s 80’s and 90’s various techniques were developed, using various bonding materials to position orthodontic brackets to dental models in the hope of increasing precision and decreasing chair time.
Most articles found that there was some increase in accuracy, but it really depended on extra factors that aren’t there in ‘direct bonding’, such as correct impressions, good accurate models that were an identical copy of the teeth to be bonded, the communication with the lab for the bonding prescription, individuals doing the bracket positioning and of course lastly the transfer system into the mouth! So as we see there has to be protocols that are followed strictly.
But nearly all articles were unanimous in the conclusion that chair time was saved and the indirect bonding technique was less stressful for both the patient and clinician.
However nearly all of the common methods used before, and even today were what we call “Eye & Hand”.
That is the person bonding the brackets to the models uses their ‘hands’, with the help of bracket tweezers or jigs and their ‘eyes’ to follow various reference lines drawn onto the model, using gauges and maybe measuring calipers.
Actually this is still true for most CAD CAM systems until recently.
Only height and ‘Tip’ can be accurately programmed leaving ‘Torque in slot’ somewhat to hope...hoping that the pre-programmed bracket system chosen would deliver it!
As we now know this is the problem in both ‘Direct’ and most ‘Indirect’ bonding of orthodontic brackets and is all due to Tooth Morphology.
With varying morphology, torque in slot will change and can even differ significantly between two adjacent central incisors! (Go to our download page for articles about this).
As we developed our techniques for Lingual orthodontic indirect bonding, which we know has a lot of problems with morphology of the lingual surfaces, then we thought to apply the same principles to our labial indirect bonding.
By using the same instruments TAD and BPD (now the T.T.S. and B.P.I.), then we can accurately program a torque value into the bracket slots of our IDB technique.
LIBIAL Indirect Bonding
We could bond directly onto the set-up models following the same techniques as ‘Hiro’, however we cannot then calculate, nor compensate for the “Torque Trap” as described by Prof.
Earl Johnson in 2013, and many have known existed due to play between the bracket slot and wires. Actually Torque is the torsional force between the wires and the brackets slots and as ‘slop’ exists between the two, then a certain number of degrees will be lost prior to the action of ‘Torque’. Thus 1. The desired labio-palatal crown inclination of the tooth will never be reached and 2. Height discrepancies in leveling could occur when torque is applied with the square and rectangular wires. Therefore we can conclude that not only due to the bio-mechanics involved, but also due to poor torque control, finishing will be prolonged and more tedious.
We actually prefer the more tedious and expensive ‘Memosil Transfer Trays’ for the labial technique, same as we do for the lingual technique. It was in our experience that minor bracket positions can happen when using the thermoforming technique.
Even if a bracket does not move with the applications of the trays in the machine, as the thermoformed sheets cool they shrink slightly, hence the micron precision we aimed for in the bonding can be lost making the trays. Secondly the thermoformed trays can really only be used once…initially and cannot be accurately used for any re-bonding, should it be needed. The Memosil trays can be sectioned with a scalpel, trimmed and used individually at any point during the treatment.