In this blog we ask the question is STO safe? Why ask, well some colleagues have
commented that they are only doing STO as its safe, where as Comprehensive Ortho isn’t. Oh, you really think that? Let’s discuss.
To begin with, the first step of Ortho treatment is the relief of crowding. The three basic options we have are Proclination, IPR and Extractions. Well we are dismissing extraction as STO systems/appliances ‘don’t do’ extractions
Proclination. …. Moving the lower incisors forward can be helpful. It can create space for the relief of the crowding. It can also help in overjet reduction, so ideal for Class 2 patients. The proclination will also reduce the overbite to some degree, but note its not intrusion despite the clear aligner brigade throwing about the term ‘relative intrusion’. So all good? Not quite. The flip side is that this proclamation can lead to violation of the alveolar housing. We know there’s not much bone on the labial surface but as its all covered in pink we seem to forget we can bone loss without loss of the pink - well, in the short term.
Then there is the issue of stability from neutral zone invasion. The teeth are in soft tissue balance with he tongue on one side and the lips/cheeks on the other. Dumping the incisors into the lip will result in the lip trying to push back… but the teeth don’t move because… because we’ve fixed them there with a bonded retainer.
One factor often over looked is the change of anterior guidance. The proclination results in shallowing the anterior guidance turning rats into cows. This change is usually ‘acceptable’ by the patient however it can result in some posterior interferences on lateral excursions in some.
Need more room? well IPR is next. Safe? In some hands, in others i ve seen a few medico legal cases where there's been an issue with tooth size and shape…. ‘the computer said I had to do it’… and then there are those with sausage fingers…. and can't hold the handpiece steady.. and results in triangular spaces.
I do think bonded retainers is the joker in the pack. The STO frequently shout ‘look the Specialist use fixed retainers’ but don’t understand the work by Little and physiological movement with age compared to relapse.
So, I would suggest STO is not safe. Do I do STO? Yes !!! but only in appropriate cases. And those use are identified by having an accurate diagnosis and obeying physiological rules.
Sometimes its acceptable to simply align the anterior teeth and leave a 12 mm overjet, as the patient declined surgery… sometimes I make the reverse overjet worse…. but they have straight teeth….and not bleeding to death as they have a coagulation disorder.
And what about litigation… well, have good records, a diagnosis, a problem list, treatment options with benefits and drawbacks and the words 'discussion' in the notes and you're much easier to defend.
Sometimes we should treat adults realistically …. but please be aware of the biological limitations.
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