If you've spent any time on plastic surgery TikTok, you've probably seen the videos: a visible step-off along the jaw after jaw angle implant surgery, worse when clenching. Many people call this masseter dehiscence. Dr. Jonathan Zelken breaks down what's actually happening, and why the standard diagnosis might not always be the right one.
If you've been on TikTok or Instagram lately, and you follow anything related to jaw surgery or facial implants, there's a good chance you've come across videos of patients showing a strange contour abnormality along the lower jaw after jaw angle implant surgery - like a visible step-off, a double bubble, a shelf-like depression that deepens when you clench your teeth. The internet has labeled this masseter dehiscence. The literature has done this for some time, and surgeons, myself included, are now having to answer questions about it in every consultation.
Today I want to do something a little different. I don't just want to explain what masseter muscle dehiscence is. I want to question whether what we're actually seeing in many of these cases truly is dehiscence at all, and why that distinction matters enormously for how we treat it.
What Masseter Muscle Dehiscence Actually Means
The masseter is the powerful muscle of mastication that runs from the cheekbone (the zygomatic arch) down to the lower jaw (the mandible). When you clench your teeth, you can feel it bulge just in front of your ear and along your lower jaw line. When jaw angle implants are placed, the surgeon accesses the mandibular angle through a small incision inside the mouth. The tissue elevated off the bone creates a pocket for the implant that includes the periosteum - a thin, paper-like connective tissue sleeve that covers the bone - as well as the overlying muscle attachments, collectively sometimes referred to as the pterygomasseteric sling.
Masseter dehiscence, in the traditional anatomical sense, means that the masseter muscle has detached completely from its insertion on the mandible and has migrated upward toward the cheekbone.
Why the Jaw Looks Hollow: Classical Mechanism
When that happens, the lower border of the jaw appears hollow or deficient with muscle contraction, because the muscle that normally fills this space is no longer there - it has retracted upward. That is the classical definition, and the mechanism that most of the literature and most surgical discussions about this complication are based on.
The Literature Problem: No Consistent Definition
Here is where things get complicated. If you go looking for the true incidence of masseter dehiscence after jaw angle implant surgery, you are not going to find a clean answer. The literature reports rates that vary very widely, with some series citing incidences as low as a few percent, and others going as high as 20 to 30 percent. That would be an extraordinary complication rate for an elective aesthetic procedure.
The problem is there is no consensus definition being applied uniformly across these studies. Different surgeons are likely calling different things by the same name. Some may be reporting any visible contour change as dehiscence; others may require imaging confirmation of muscle displacement. This inconsistency makes it nearly impossible to give a patient a realistic and reliable number during a consultation.
Dr. Zelken's Own Practice: ~100 Jaw Angle Implants
In my own practice, I have placed approximately 100 jaw angle implants over the past two years. Of those, I am aware of one case that raised concern for masseter dehiscence. Underreporting is real - patients may experience mild changes and never return, or attribute them to normal healing variations.
A Patient Case That Raised Concern
This patient was a young man who came to me for jaw widening and lengthening surgery. He had notably prominent masseters to begin with, which is a relevant detail. His implants were custom designed, and I was intentionally conservative with those dimensions. The access was through an intraoral approach, used to elevate the periosteum off the mandibular angle using a blunt instrument called an osteotome.
At approximately four months postoperatively, the patient sent photographs describing a double bubble: a visible contour irregularity along the lower jaw at certain angles when he clenched his jaw shut. He had found videos online that mirrored his appearance and was understandably concerned.
Dynamic Examination: What He Observed
I invited this young man back immediately and photographed him at rest and during dynamic jaw clenching. There was a noticeable step-off - a shelf-like depression at the lower border of the masseter that became more pronounced when he clenched his jaw. But here is what caught my attention: the length of the masseter did not shorten when he clenched his jaw.
The Key Finding: Muscle Length Did Not Shorten
In true masseter dehiscence, when the muscle retracts upward toward the cheekbone, you would expect the functional length of the visible muscle to shorten significantly - the muscle literally sits higher on the face. But that is not what I was seeing. The muscle was the exact same length as it was pre-operatively. It was just developing a surface contour change, almost a depression at the lower pole.
An Alternative Hypothesis: Periosteal Stretching
This is where I want to make an argument with serious clinical implications. What if what we are calling masseter dehiscence in many of these cases is not true anatomical separation of the muscle from the bone at all?
My alternative hypothesis: when we elevate the periosteum off the mandibular angle to create the implant pocket, we strip away that thin connective tissue sleeve. In some patients, the periosteum heals in a way that leaves a narrow isthmus of tissue bridging across the lower pole of the implant. Over time, with the repetitive mechanical force of chewing and clenching - especially alongside weight loss - that periosteal isthmus stretches and thins over the hard, prominent implant edge. The masseter, which is not actually separated from its bony insertion, continues to function at its normal length.
Why This Distinction Changes Everything
The surface contour changes because the soft tissue envelope overlying the lower pole of the implant is no longer providing uniform support. What the patient and the camera see - a step-off, a depression with clenching - looks exactly like dehiscence. But what may actually be happening is a periosteal stretch mechanism over a prominent implant edge, without any true muscular separation. This distinction has direct implications for treatment.
Surgical Treatment for True Dehiscence and Its Risks
The surgical treatment for true masseter dehiscence involves opening an external incision - a visible scar along or below the jaw - and repairing the detached muscle back to the mandible. It is a real operation, with real recovery, a permanent mark on the skin, and its own risk profile.
If the underlying anatomy reflects true muscular separation, that repair is anatomically rational. But if we are dealing with periosteal stretching over the lower pole of the implant, with the muscle still functionally attached and at normal length, then that repair does not address the problem and is prone to failure. The patient would have a visible scar with little to show for it.
Non-Surgical Strategy: Neurotoxin and Filler
For my own patient, before committing to revision surgery, I offered a non-surgical strategy: neurotoxin injection (including Botox or Dysport) to selectively weaken the masseter muscle. By reducing the force of muscular contraction, we reduce the dynamic contour change that occurs with clenching. Simultaneously, a small amount of soft tissue filler can volumize that lower pole defect of the jaw, providing surface support where the periosteal envelope has thinned. My patient's result is currently satisfactory - the contour is improved and the dynamic step-off is less visible.
Transparency: What We Still Don't Know
We do not yet know the longevity of this strategy, or how often it will work. Neurotoxin wears off, and filler can migrate or resorb. This is not a permanent solution. But for a patient who may not have true dehiscence, a reversible, non-surgical approach that avoids a visible scar and a second operation is a reasonable first line before any surgical revision is attempted.
Two Different Problems, One Label
The literature on masseter dehiscence is inconsistent. Reported incidences range widely and are likely influenced both by underreporting and by the absence of a standardized definition.
More importantly, what the literature calls masseter dehiscence may represent more than one distinct anatomical event. Some cases are likely true muscular separation. Others may represent periosteal stretching over the lower pole of a prominent implant, with the muscle functionally still intact. These two scenarios look similar in photographs and in viral videos - but they are not the same problem, and they may not respond to the same treatment.
If you are a patient who has experienced this after jaw implant surgery: seek evaluation from a surgeon who is willing to examine you dynamically, in person, and who is asking whether your muscle length changes with clenching. If you are a surgeon: we owe it to our patients to be more precise about what we are diagnosing before recommending an irreversible operation with a visible external scar.
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