Correcting the Bite and the Midface
How do we correct a retruded midface and an underbite once a child has nearly finished growing?
💡 Moving the set-back upper jaw forward fixes both the underbite and the flat profile, and it waits until so it will not relapse.
Prerequisite check
- The is the upper jaw and the bone of the midface, the region under the eyes and around the upper lip.
- Two forces hold the midface back: an intrinsic tendency to grow poorly forward, plus a restraining scar from surgery.
What you will learn
Goal: Explain how orthodontics, Le Fort I advancement, and correct a retruded midface, and why these are done near .
- Surgery that repositions the jaw bones is called ; it corrects the Class III bite and the flat profile together by moving the forward.
- The is a planned cut across the that frees the whole upper jaw so it can be moved forward and fixed with plates.
- cuts the bone and then slowly separates the ends so new bone grows in the gap, used for large forward moves.
- These corrections wait until , because moving a jaw that is still growing would relapse.
Model: Mateo's profile at age 15, and two ways to move the upper jaw forward
Mateo's records at age 15 show a recognizable pattern in repaired lip and . His lower jaw sits in front of his upper jaw when his teeth touch, so his lower front teeth close ahead of the upper ones (an underbite). His midface, the region under the eyes and around the upper lip, looks flat and set back. Orthodontic notes call this a Class III relationship. The cause is the one the team already knows: the grows poorly forward, and palate scar adds a restraining effect, together producing a flat, retruded midface. Children who screened positive for sleep-disordered breathing were more likely to have this Class III, maxilla-set-back pattern, so the bite problem and the airway problem share a root.
Surgeons have two main moves once growth is nearly done. A with advancement: the surgeon makes a planned cut across the above the tooth roots, frees the whole upper-jaw block, slides it forward to a new position, and fixes it there with small plates and screws. This is the classic correction for in patients. : instead of moving the whole block at once, the surgeon makes the cut and then slowly separates the two bone ends a fraction of a millimeter per day using a device; new bone forms in the widening gap. This is used when the jaw must move a long way forward, where a single slide would be too large to heal well.
These corrections wait until in the teen years, because moving a jaw that is still growing would relapse. The orthodontist aligns and levels the teeth first so the new jaw position produces a working bite.
Explore (work the model before reading on)
- Which jaw is positioned in front of the other when Mateo bites down?
- Name the two forces that together hold the midface back.
- If the upper jaw is set back, why would moving it forward fix both the underbite and the flat profile at the same time?
- Le Fort I moves the jaw all at once; distraction moves it slowly and grows new bone. Why pick distraction for a very large forward move?
- A set-back was linked to sleep-disordered breathing. Predict what advancing the maxilla forward might do to the airway behind it.
Guided notes
The bite to correct
- In a the upper teeth close ____ (behind) the lower teeth, an underbite.
- Surgery that repositions the jaw bones is called ____ surgery.
Two ways to move the jaw
- The ____ osteotomy is a planned cut across the that lets the surgeon move the whole upper jaw forward and fix it with plates.
- When the jaw must move a long distance, pulls the cut ends apart slowly so the body grows ____ (new) bone in the gap.
Why wait
- These corrections wait until ____ () because moving a still-growing jaw would relapse.
Reading the Research
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Vocabulary (the same words your classes use)
Vetted readings for this lesson
- Powell et al. 2022, Does Early Secondary ABG Influence Need for Maxillary Advancement (Cleft Palate Craniofac J)
- Dissaux et al. 2016, Evaluation of 5-Year-Old Children With Complete CLP, Part 2 (J Craniomaxillofac Surg)
- Daskalogiannakis et al. 2009, Need for Orthognathic Surgery in Repaired Complete Unilateral CLP (Cleft Palate Craniofac J)
Track your progress today
Check these off as you work through the lesson, then submit. This tells Mr. Mendoza how you're doing so he can help the class. It does not replace turning in your producible.
Use the code Mr. Mendoza gave you, not your name. Saved on this device.
- Read the Model and answered the Explore questions.
- Filled in the guided notes in my own words.
- Defined the new vocabulary with an example.
- Built the producible: Present Mateo's plan at the team meeting. In three or four sentences, recommend either Le Fort I advancement or distraction osteogenesis for him, and justify it using two facts: his Class III, set-back midface and the size of the forward move you expect. Add one sentence on why you are waiting until he is older to operate.
- Wrote my Claim, Evidence, and Reasoning exit ticket.
Exit ticket (Claim, Evidence, Reasoning)
- Claim: Mateo's underbite and flat midface can be corrected by moving his upper jaw forward.
- Evidence: Cite the Class III, retruded- pattern and one surgical method from today.
- Reasoning: Explain why moving the forward fixes both the bite and the profile, and why the team waits for .
| Criterion | Proficient | Developing | Beginning |
|---|---|---|---|
| Complete | Every required part of the artifact is present and filled in. | Most parts are present, but one is missing or left blank. | Several parts are missing. |
| Accurate | The science and data are correct and match the evidence. | Mostly correct, with a small factual slip. | Key science or data is wrong. |
| Scientific reasoning (CER) | States a claim, backs it with specific evidence, and explains the reasoning. | Has a claim and evidence, but the reasoning is thin or missing. | Gives an answer with no evidence or reasoning. |
| Professional communication | Clear, organized, and labeled the way a clinician or scientist would write it. | Readable but disorganized or missing labels. | Hard to follow. |
| Submitted | Turned in the right way (Schoology for routine work) and confirmed. | Turned in, but in the wrong place or unconfirmed. | Not turned in. |
- CompleteProficient: Nothing is left blank: the model fills every part of "Present Mateo's plan at the team meeting. In three or four sentences, recommend either Le Fort I advancement or distraction osteogenesis for him, and justify it using two facts: his Class III, set-back midface and the size of the forward move you expect. Add one sentence on why you are waiting until he is older to operate.".
- AccurateProficient: Every number and claim matches the case evidence.
- Scientific reasoning (CER)Proficient: It names a claim, cites the specific evidence, and explains the reasoning, not just the answer.
- Professional communicationProficient: It is organized and labeled like a real chart note.
- SubmittedProficient: It would be turned in on Schoology and confirmed.
Where this leads: careers
What's next: We answered how the bite and midface are corrected. But the nose sits on that midface, and even after the jaw moves forward, Mateo's nose is still asymmetric and partly blocked. How is the nose itself affected, and how is it repaired? We chase that next time.