8th Adjustment: The female ortho, elastics, and a question.

[tofino]

Hi.

I had my 8th adjustment yesterday. I was seen by the female ortho, which was good because she is more inclined to talk about my case with me than the usual guy. She said to the assistant, "Class I on the left, Class II on the right". Then without any fanfare the assistant was suddenly showing me how to put elastics from my top 1st molar hooks down to the canines. Wow, the pain is just settling down as I write this.

SEE PHOTO HERE: http://karlrove.ca/dental/adjust8.png

When I asked about the purpose of the elastics, I received vague answers about 'meshing teeth', Newton's 3rd Law, and so on, but she did say quite clearly that my bite was going to worsen as my teeth are prepped for surgery. I assume that means my overjet will worsen as the lower teeth retract.

So, what precisely are these elastics accomplishing?

Cheers

Glen

[tofino]

Hi.

You mean nobody else has had this elastic configuration !?

Wow, I'm starting to feel special.

Cheers

Glen

[stclair5211]

Not sure what there doing. I was told I'll wear some that go in the other direction. Upper front to the lower back that will get rid of my overjet. Yours look like there creating an overjet. I'd just trust the ortho, there what you call "college edu-ma-cated."

[jcdamon3]

It looks like they are trying to pull your top teeth forward because if your bite is like it is in the picture your teeth are not meshing together properly. I don't know how to explain this but your pointy part of your top teeth should mesh with the "valleys" (or speaces between) of the lower teeth. Someone on the board had a url for the description of perfect teeth. I should have book marked it. Anyone have it?

[rsprouse]

Class I is what is considered ideal. Everything is judged based on the location of the first molars (maxillary arch compared to mandible). Class I has the front outer (mesial buccal) cusp of the upper first molar sitting in the middle on the outside of the lower first molar (buccal groove). Class III is when the relationship of the first molars has the lower first molar further forward. So the upper first molar contacts in between the space of the first and second mandibular molars. Class II is when the mandibular first molar is further back in the mouth, say behind the maxillary first molar for example. The elastics are simply using anchorage to create a force to pull you closer into a class I relationship. Hope that helps.

-Rory

[tofino]

Hi and thanks.

But I'm told that my bite will get intentionally worse as mandibular advancement surgery approaches - more severe Class II than I have now. (I've seen this referenced elsewhere in journals). Is that why, using the upper first molars as essentially anchors, the forces on the canines will draw them back (closing some small extraction gaps), and retracting the entire lower arch? If the upper molars are anchors, then I don't see how this configuration affects the upper arch.

I must confess: I have a background in physics, and what I don't get is how this configuration does not yard the lower canines vertically out of their sockets. Somebody check my understanding: these are 3.5 oz elastics, or roughly 100 g, or more meaningfully, have a working tension of about 1 Newton of force. The angle on my elastics is about 30 degrees above horizontal. This results in a vertical component of force on each canine of about 0.5 Newtons. Does the archwire resist this force?

Maybe this post should be in Ask the Docs.

Cheers

Glen

[rsprouse]

Hi Glen,

I am not an orthodontist so this is probably best asked to your treating doctor. I assume that you are going to have a sagital split osteotomy? Since you are going to have your jaw advanced you may be having your teeth moved posteriorly so that they line up after your surgery.

Typically (about 75% of the time) space is closed by moving the anterior segment backwards. Although the mandibular canine has a long thick root, the maxillary molar has three large roots that are anchored very well and are a great way to anchor tooth movement. The maxillary first molar has an anchorage value of twice the mandibular canine. You also have the second molar with three large roots and your premolar(s) to help as an anchor which are greater than the canine.

I do not have enough of a background to know what specific net force is being exerted on each tooth. But the archwire can in fact resist force depending on how it is placed. You have elastics from the upper posteriors to lower anteriors, which are pitting forward movement of the entire upper arch against the distal movement of lower anterior segment.

[victory1]

Hi.

I had my 8th adjustment yesterday. I was seen by the female ortho, which was good because she is more inclined to talk about my case with me than the usual guy. She said to the assistant, "Class I on the left, Class II on the right". Then without any fanfare the assistant was suddenly showing me how to put elastics from my top 1st molar hooks down to the canines. Wow, the pain is just settling down as I write this.

SEE PHOTO HERE: http://karlrove.ca/dental/adjust8.png

When I asked about the purpose of the elastics, I received vague answers about 'meshing teeth', Newton's 3rd Law, and so on, but she did say quite clearly that my bite was going to worsen as my teeth are prepped for surgery. I assume that means my overjet will worsen as the lower teeth retract.

So, what precisely are these elastics accomplishing?

Cheers

Glen

I have the exact set-up, but I'm in my last 3 months of braces. I got this set-up on Jan 30th, before my braces where not rubbing inside of my mouth, now I can feel them and they are cutting inside of mouth and the elastics are also rubbing. What ever she's trying to fix, the movement is more irritating then before she put the elastics.

[ingyandbert]

Wow, you guys! I feel like I'm doing post-grad work just reading your messages!

[sunluvr]

My elastics were put on after 11 months of treatment. They form a triangle with one point on the top and two on the bottom. I have no idea what they are there for. I'm one of those who doesn't ask questions. I just do what I'm told which is change them about 5 times per day.

If I new how to attach a photo I would include one. Sorry![/img]