Lip flip vs vertical lip lines is a question that sounds like a technique comparison and is actually an anatomy question. Both treatments weaken the orbicularis oris. They are not variations of one procedure, because the orbicularis oris is not one uniform muscle, and the part of it that produces lip eversion is not the part of it that produces perioral rhytides. Melissa Pulcini-Buttine, PA flags the distinction in passing while walking the perioral anatomy — "If I'm doing vertical lip lines I may change my technique... if I'm doing a lip flip, the orbicularis oris inserts into the vermilion border of the lip, so I would have a different technique" — and the reason behind it is worth unpacking properly, because it determines which patients are candidates for which.
This piece is about why the two differ and how to choose. It is not a technique description; the manoeuvres themselves are learned under supervision, and in a region this functionally loaded that distinction matters.
The muscle is two muscles in practice
The orbicularis oris encircles the oral aperture and is conventionally described in two parts.
The pars peripheralis is the outer, deeper portion. It is not a self-contained ring — it receives and interweaves fibres from the muscles that converge at the modiolus, and it occupies the territory extending outward from the vermilion onto the cutaneous lip. It does the sphincteric work: pursing, compressing, sealing.
The pars marginalis is the inner portion, lying at the vermilion itself. Its role is the fine control of the lip margin, including the inward rolling of the upper lip that reduces visible vermilion.
Those two jobs map directly onto the two treatments. Reducing inward rolling to increase vermilion show is a pars marginalis problem. Softening radial rhytides that extend outward onto the cutaneous lip is a pars peripheralis problem. The published description of the lip flip is explicit about the target: partial relaxation of the pars marginalis of the upper orbicularis oris, with injection placed superficially along the upper vermilion border, deliberately avoiding the oral commissures and the deeper muscle layers (JPRAS Open 2026;51:165–168).
Melissa's general rule for the muscle is consistent with that: the orbicularis oris takes superficial injection points. It is a thin muscle lying close to the skin, in the same category as the orbicularis oculi rather than the deep glabellar depressors.
Why territory, not dose, is the difference
If the two treatments differed only in how much toxin was used, they would be the same procedure at two intensities and the results would lie on a continuum. They do not.
A lip flip needs the effect confined to a narrow band at the vermilion border of the upper lip. Spread beyond it reaches the sphincteric portion, and the sphincteric portion is the part the patient uses to drink, whistle, articulate consonants and keep the mouth closed. A perioral rhytid treatment needs the effect distributed across a wider cutaneous territory — but for the same reason must remain shallow and must stay away from the commissures, where the modiolus gathers six muscles with conflicting jobs into a few millimetres.
So the two differ in the shape of the treated territory and its relationship to depth, not in the quantity of drug. That is why a lip flip performed "more thoroughly" does not become a rhytid treatment, and why a rhytid treatment performed conservatively does not produce eversion.
The finding that decides candidacy
Here is the part that changes consultations, and it is not widely taught.
The pars marginalis is not reliably present. Sonographic study of the upper labial orbicularis oris classified the muscle by how developed the pars marginalis was and found three distinct patterns at the lip midline: in 20.0 percent of volunteers the pars marginalis was rarely observed and appeared only in traces; in 42.9 percent it was well developed and continuous; and in 37.1 percent it was present but discontinuous (Park HJ, Lee KL, Gil YC, et al. Aesthetic Surgery Journal. 2020;40(7):778–783). The authors concluded that the shapes varied markedly between volunteers and that classifying the muscle by its form is useful reference information when injecting neurotoxin into the upper lip.
Read against the mechanism of a lip flip, that is a candidacy statistic. The procedure works by partially relaxing a specific muscular subdivision. In roughly one patient in five, that subdivision is present only in traces, and in more than a third it is discontinuous. A patient in the first group is unlikely to get a satisfying result from a treatment that depends on relaxing something they have very little of — and the failure will not look like a dosing problem.
It also explains a pattern most injectors have seen and attributed to technique: the same approach producing an obvious eversion in one patient and almost nothing in the next.
The two requests get conflated in the consultation
Patients rarely present with an anatomical request. They present with "I want my top lip to show more" and "I have these little lines," and those two sentences are frequently spoken by the same person in the same appointment.
Three separations are worth making explicitly before planning.
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Eversion is not volume. The published framing is useful to borrow: neurotoxin lip flip targets dynamic muscle activity, whereas fillers address volume deficiency. A patient who wants a larger lip is asking for volume and will not be satisfied by a change in lip roll. A patient whose lip is adequately volumised but rolls inward when she smiles is the candidate. If filler is where the conversation lands, Empire's page on common lip filler reactions and how to avoid them is the relevant safety reading.
Rhytides are frequently not primarily muscular. Perioral lines are a composite of muscular activity, dermal photoageing and lost structural support. Toxin softens the dynamic component. A line that is fully present at complete rest has a dermal component that muscle relaxation will not erase, which is the distinction covered in dynamic vs static wrinkles, and perioral structural loss is part of the broader picture in facial volume loss. Promising line elimination from a toxin treatment alone is the most reliable way to produce a dissatisfied perioral patient.
Both share the same functional ceiling. The orbicularis oris is a working sphincter, and the adverse events monitored in the lip flip literature describe exactly what is at stake: asymmetry, speech disturbance, difficulty drinking from a straw, whistling difficulty, oral incompetence, drooling, and abnormal smile or oral movement. That list belongs in the consent conversation for both treatments, not just the one the patient asked about.
What the evidence actually supports
The lip flip is popular well beyond its evidence base, and an honest consultation should reflect that.
The clinical report describing the anatomical rationale above followed three consecutive patients. All three showed subtle upper lip eversion and reduction of vertical upper lip rhytides at two weeks with satisfaction from "satisfied" to "very satisfied," and none reported speech disturbance, oral incompetence or difficulty with oral movement. The authors themselves state the limitations plainly: three patients only, no control group, no blinded independent assessment, descriptive outcome assessment, and short follow-up.
That is a case series, not evidence of efficacy or of safety. What it supports is that the anatomical rationale is coherent and the immediate functional risk in three carefully selected patients was not realised. It does not support a complication rate, a durability estimate, or a claim that the procedure reliably works.
For an injector, the useful posture is: the mechanism makes sense, the candidacy question is real and answerable from anatomy, the functional risk is genuine, and the published outcome data are thin. Say all four to the patient.
What changes at the chairside
- Separate the two requests before planning. Vermilion show and perioral lines are different problems with different targets, even in the same patient.
- Assess on animation. Ask for a smile, a purse and speech. Inward roll on smiling is the finding that identifies a lip flip candidate; rhytides on pursing indicate the peripheral territory.
- Expect variable response and say so in advance. The pars marginalis is well developed and continuous in fewer than half of people, and a modest result is often anatomy rather than dosing.
- Consent for function, not just appearance. Speech, drinking, whistling and oral competence belong in the conversation for either treatment.
- Stay away from the commissures in both. The modiolus is where the perioral muscles converge and where an unintended effect stops being cosmetic.
Perioral work sits at the point where neurotoxin, volume and skin quality all contribute to the same complaint, which is why it is usually planned as a combination rather than a single modality. Empire covers the combined approach in complete facial aesthetic training and the neurotoxin side in advanced botulinum toxin and filler training.
The clinical reasoning above reflects Melissa Pulcini-Buttine's practice as taught in Empire Medical Training's hands-on curriculum. Technique is learned under supervision; this article is educational and is not a substitute for training.
Melissa Pulcini-Buttine, PA is a physician assistant of two decades and has been a professor of anatomy and physiology for approximately fourteen years. She is a faculty member at Empire Medical Training and the founder of an aesthetics practice in Greenwich, Connecticut.
Frequently Asked Questions
Why do a lip flip and perioral line treatment use different techniques?
Because they target different parts of the same muscle. The lip flip depends on partial relaxation of the pars marginalis at the vermilion, the portion controlling inward roll of the lip margin. Perioral rhytides arise from the peripheral portion extending outward onto the cutaneous lip. The treated territory differs in shape and extent, not in dose.
Why does a lip flip work well in some patients and barely at all in others?
Often anatomy rather than technique. Sonographic study of the upper labial orbicularis oris found the pars marginalis well developed and continuous in only 42.9 percent of volunteers, discontinuous in 37.1 percent, and present only in traces in 20.0 percent. A procedure that works by relaxing that subdivision has less to act on in most people than is generally assumed.
Will neurotoxin remove vertical lip lines?
It softens the dynamic component. Perioral lines are a composite of muscle activity, dermal photoageing and lost structural support, and a line fully present at complete rest has a dermal component that muscle relaxation does not address. Setting that expectation before treatment is the difference between a good result and a disappointed patient.
What should be included in consent for perioral neurotoxin?
Function, not only appearance. The adverse events monitored in the published lip flip literature are asymmetry, speech disturbance, difficulty drinking from a straw, whistling difficulty, oral incompetence, drooling, and abnormal smile or oral movement. The orbicularis oris is a working sphincter and the consent should reflect that for either indication.
Disclaimer
This article reflects the clinical opinions and experience of Melissa Pulcini-Buttine, PA, an independent faculty member contributing to Empire Medical Training's curriculum. The views expressed are the author's own and do not necessarily represent those of Empire Medical Training.
It is professional education, not medical advice, and is no substitute for hands-on training or independent clinical judgment. Licensed clinicians remain responsible for their own patient selection, technique and outcomes, for verifying current product labelling, and for practising within their scope and applicable law. Empire Medical Training accepts no liability for reliance on this content.
