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Sample test
Good Morning!
For this case, I did not understand:
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why is it just a retrusive mandibe and not protrusive maxilla?
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The ceph shows proclination of maxillary and mandibular incisors so I expected them to want to extract prior to surgery but they did not?
Thank you in advance!
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11 Replies
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Joti, Fantastic Questions!
Here are a couple of my thoughts:
1) Protrusive vs. Normal Maxilla – Yes, I agree that the mandible is clearly retrusive. Now for the maxilla I would consider a couple items. First, if you using SNA the ABO likes the norm of 82 with a standard deviation of about 3 degrees. In addition, her cranial base angle (FH – SN) just a touch off the standard of 7 degrees which also affects SNA. So for me that gets me to the same point of is this a protrusive or normal maxilla?? Then I start looking at the Position of the max incisors – considering AP position and proclination. I agree those max incisors look proclined – then when I see there is a diastema and space to close I start thinking “Yup, I’ll use that space to help me upright incisors a bit”. Now in the AP position of those max incisors I like to use Andrews Anterior Limit Goal line based on Glabella. Looking at her profile I think her max incisors are in a good AP position. So this is a long answer to say after all these considerations I then come down with – Ok, I don’t want to move her maxilla in the AP. That is where the rubber meets the road – is it something you are going to treat? That is my analysis of why the board suggested answers does not include protrusive maxilla. NOW REALITY! Remember the board doesn’t mark “wrong” answers to you could in your list of responses type “Protrusive maxilla” if you diagnose that as the case but just be mindful of what your upcoming treatment will encompass. Is there a dental/skeletal objective where you will address that issue?
2) Proclined Incisors – I agree the numbers show proclination. As I mentioned above, I think the max incisors have space to work with in aligning. In addition, the AP position of the max incisors based on the anterior goal line from her forehead and incisal display are where I am comfortable keeping them. The man incisors make me think extraction for sure and in order to maximize the advancement and leveling the curve of spee as well. The catch is that there is minimal crowding. Now, the suggested ABO answer is non-extraction but notice that it’s not a “deal breaker” answer. I think there is plenty here that you’ll knock it out of the park with your assessment.
Keep up the great work!
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Thank you for your detailed reply it was so helpful! SNA makes sense, I didn’t think about the range. For the upper incsiors, how much do you think U1-SN would decrease by closing the diastema? What is hard is that if you decide to not extract in the upper it makes sense to not extract in the lower (OJ) but if you wrongly extract in the upper you will incorrectly extract in the lower as well.
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Answering: For the upper incisors, how much do you think U1-SN would decrease by closing the diastema?
When looking at crowding and spacing with incisor angles I think back on the term “Cephalometric Crowding” or “Cephalometric Spacing”. Basically it’s the idea that if there are teeth that are overly proclined that once you correct the inclination you will loose space – therefore “crowding” that is due to a proclination issue identified on the lateral ceph. (Ceph Spacing is the reverse, overly upright teeth that once you procline them they will “create” space).
Now for getting a ballpark estimate the rough guess is from the McLaughlin, Bennett, Trevisi textbook on Systemised Orthodontic Treatment Mechanics. They proposed the estimate that 2.5 degrees of proclination gains 2mm of space. I tend to think better in 5 degrees so I just say if I procline 5 degrees I will “roughly” expect to get 4mm of space. If I have 4mm of space (such as this diastema) then I can expect to upright about 5 degrees.
It’s a good quick estimate but there are other studies that show it’s not precise. That’s why this is the Art and Science of Orthodontics!
(McLaughlin RP, Bennett JC, Trevisi H. Systemised Orthodontic Treatment Mechanics. Maryland Heights, MO: Mosby; 2001. p. 179. – I’m putting a screen shot of that page here and so citing the full source)
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Joti, great questions as always!
Answering the second part – I agree about getting the extractions right in one arch drives what you do to coordinate arches.
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Very helpful. TY!!
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You are very welcome! Good luck with the studying everyone
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In this case, would it be wrong to say ext Upper 5s and Lower 4s along with orthognathic surgery? Or ext lower 4s and consider U5s after diastema closure?
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Donna, good question to ask
What are your thoughts on extracting the U5s? What’s your reason and what’s your treatment goal?
Everyone feel free to jump in BTW! Dialogue together helps us hash these things out.
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I’m trying to address the proclination of the upper incisors but not over-retract them so we can still maximize mandibular advancement.
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Donna, That sounds like good reasons to me! One of the things I appreciate on the ABO samples is that the list a range of possible answers. Sometimes their solutions say “must include” – when I look at that it’s generally slam dunk. Now I think U5s here is a “could include” response – so fine to list but if you did or did not put it don’t think they’d say “failed question”
Good work!
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Thanks!
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