Jaw Muscle and Smile Enhancement Botox Injection — Cost, Top Hospitals & Success Rates | MyMedicPlus

The lower face and smile are among the most expressive and emotionally communicative regions of human anatomy, governed by a complex interplay of more than two dozen muscles. Subtle imbalances in lower facial muscle dynamics — whether from overactive muscles (producing a gummy smile, downturned mouth corners, or a wide jaw), underactive muscles (a narrow or restrained smile), or asymmetric tone — can significantly affect how a person's face is perceived and how they feel about their appearance. Botulinum toxin type A (BTX-A) has emerged as one of the most precise and versatile tools for addressing these concerns without surgery.

Unlike the upper face (where BTX is used primarily for wrinkle relaxation in the glabella, forehead, and lateral canthi), lower face BTX injections require an exceptionally detailed understanding of the anatomy and functional interactions of the perioral musculature, because this region is responsible for speech, eating, drinking, and the entirety of human smile and emotional expression. Misdirected or excessive injection in this area carries a real and significant risk of smile asymmetry, speech difficulty, and impaired lip seal — complications that are distressing for patients and demand the highest standard of injector precision and anatomical knowledge.

This guide covers the principal applications of BTX-A in lower face and smile enhancement: masseter muscle slimming for facial contouring; correction of a gummy smile (excessive gingival display); the 'lip flip' for upper lip enhancement; depressor anguli oris (DAO) injection to correct downturned mouth corners; mentalis injection for chin dimpling; and enhancement of smile width through targeting of the zygomaticus and risorius muscles. Each represents a distinct clinical indication with its own muscle target, dose, technique, risks, and expected outcome.

Masseter hypertrophy / wide lower face: Enlargement of the masseter (jaw-closing) muscle produces a wide, square, or rectangular lower face. Masseter BTX injection slims the lower face by producing reversible chemical atrophy of this muscle. Full details are covered in the dedicated Jaw and Calf Muscle Hypertrophy guide; in the smile context, masseter slimming is frequently combined with peri-oral injections for a complete lower face aesthetic treatment.

Gummy smile (excessive gingival display): A gummy smile is defined as exposure of more than 3–4 mm of gingival tissue above the upper incisors during a natural relaxed smile. It affects an estimated 10% of young adults and causes significant self-consciousness in many. The commonest cause is hyperactivity of the levator labii superioris alaeque nasi (LLSAN) muscle — a paired muscle originating from the nasal alar base and inserting into the upper lip, which pulls the lip superiorly during smiling. Excessive gingival display may also result from vertical maxillary excess (skeletal cause), short clinical crown length, or gingival hyperplasia — but when muscular hyperactivity is the dominant factor, BTX is highly effective.

Downturned mouth corners (oral commissure depression): In some individuals — particularly with age — the corners of the mouth are pulled downward at rest and during expression by the depressor anguli oris (DAO) muscles, creating a persistently sad, stern, or disapproving facial expression that does not reflect the person's emotional state. BTX injection into the DAO reduces the downward pull on the oral commissures, allowing the counteracting zygomaticus and risorius muscles to lift the corners at rest and during smiling.

Thin or rolled-inward upper lip ('lip flip'): The 'lip flip' uses very small doses of BTX injected into the orbicularis oris muscle along the vermilion border of the upper lip. Mild relaxation of this circular lip muscle allows the upper lip to unfurl or 'flip' outward, creating the appearance of greater lip volume and a more defined Cupid's bow without filler. It is particularly effective for the upper lip that rolls inward when smiling.

Chin dimpling / 'peau d'orange' chin: Hyperactivity of the mentalis muscle — which elevates and protrudes the lower lip — creates dimpling, cobblestoning, or an uneven 'orange peel' texture of the chin skin. BTX injection into the mentalis smooths this texture.

Narrow or restricted smile width: Patients who feel their smile is narrow or shows fewer teeth than desired may benefit from BTX injection to the zygomaticus minor and modiolus area to subtly reduce muscle restriction on lateral smile movement, or from precise low-dose injection around the perioral modiolus to allow the smile to spread more laterally. This is a nuanced and less commonly performed indication requiring careful patient selection.

Lower face and smile BTX treatment demands the most thorough preoperative clinical assessment of any facial BTX application. A detailed dynamic assessment is performed with the patient seated, asked to smile naturally, show teeth, pucker lips, and produce various facial expressions while the clinician identifies which muscles are overactive, which are underactive, and whether the concern is primarily muscular or has a structural component.

For gummy smile correction: the clinician must determine that the gummy smile is due to LLSAN/levator labii superioris hyperactivity and not primarily to vertical maxillary excess (a skeletal problem requiring orthognathic surgery) or gingival overgrowth (a periodontal problem). Measurement of gingival exposure in millimetres during natural smile and maximum smile (using a standardised ruler held at the midline) quantifies the severity. A smile with 4–6 mm gingival show is ideal for BTX; >8–10 mm gingival show often indicates a skeletal component and warrants orthodontic/surgical consultation as well.

For DAO injection: the clinician assesses the downward deflection of the oral commissures at rest compared with an expressionless relaxed baseline. The course of the DAO must be anatomically mapped — its superficial location means injection too medially risks inadvertent involvement of the depressor labii inferioris (DLI) or orbicularis oris, causing functional lip impairment. The marginal mandibular branch of the facial nerve runs in this region; deep injection risks motor nerve injury.

Absolute contraindications are the same as for all BTX applications: pregnancy, breastfeeding, neuromuscular junction disorders, known hypersensitivity to the product. The orbicularis oris is particularly important to assess prior to lip flip — wind instrument musicians (trumpeters, flautists), professional singers, and athletes who need a strong lip seal (swimmers, divers) are generally poor candidates for even low-dose orbicularis injection due to the risk of impairing performance. Patients with prior lip filler should have their filler noted and the dose adjusted accordingly.

Gummy smile — LLSAN injection: The LLSAN is targeted bilaterally at a point approximately 1 cm lateral to the alar base of the nose where it emerges superficially. The injection must be placed superficially in the superficial muscular aponeurotic system (SMAS) layer; a 32-gauge needle is used, and the injection is intradermal or immediately subcutaneous. Dose: 2–4 units per side (onabotulinumtoxinA) — this is among the lowest doses used in BTX practice, reflecting the critical functional importance of this muscle and the narrow therapeutic window. The levator labii superioris (LLS) — adjacent medially — may be injected additionally at 1–2 units per side in severe gummy smile cases. The total dose for gummy smile correction is typically only 4–12 units bilaterally. Onset 3–5 days; effect duration 3–4 months.

Depressor anguli oris (DAO) injection: The DAO is a triangular muscle originating from the mandibular tubercle and converging with the orbicularis oris and other muscles at the modiolus (the fibromuscular node at the angle of the mouth). Injection is placed at the inferolateral aspect of the DAO belly, at least 1–1.5 cm below and lateral to the oral commissure, avoiding the modiolus itself and the overlying zygomaticus muscles. Dose: 2–5 units per side (onabotulinumtoxinA). The injection must remain lateral to the DLI to avoid asymmetric lower lip depression. BTX is placed intramuscularly using a 32-gauge needle; gentle aspiration to confirm no vascular penetration is advisable. Duration 3–4 months.

Lip flip — orbicularis oris injection: Small aliquots of BTX (typically 2–4 units total distributed in 4–6 injection points along the upper vermilion border) are placed superficially into the orbicularis oris at the vermilion border itself — not deeper, to avoid affecting the deeper portion of the muscle that maintains lip seal. Points are placed medially and extend to just past the Cupid's bow peaks. The technique relaxes the sphincteric action of the superficial orbicularis, causing the dry vermilion to rotate anteriorly and superiorly. Effect onset 3–5 days; duration 2–3 months (shorter than other sites due to the fine doses used). Important: patients must be warned that lip seal for drinking straws, musical instruments, and pursing is temporarily affected.

Mentalis injection for chin dimpling: The mentalis muscle lies centrally in the soft tissue of the chin, inferior to the lower lip. Hyperactive mentalis causes dimpling and 'peau d'orange' (orange peel) texture. Injection is placed at 2–4 points centrally in the chin pad, at a depth of 5–8 mm to reach the muscle belly. Dose: 4–10 units total. Care must be taken to avoid injection too inferior (which can affect the DLI or cause ptosis of the chin soft tissue) or too lateral (which may affect the DLI). Patients should be warned of transient difficulty whistling or pursing the lips. Duration 3–4 months.

Zygomaticus and risorius enhancement for smile width: This is the most anatomically demanding lower face BTX application and is performed only by very experienced injectors. Very small doses (1–2 units per point) are placed at specific perioral points to subtly reduce antagonist muscle tension that restricts lateral smile width, or to fine-tune smile symmetry by balancing zygomaticus major activity between sides. Anatomical variation in this region is high; detailed pre-treatment dynamic photography and video analysis is essential.

When performed by a clinician with expert-level anatomical knowledge and a conservative, staged dosing approach, lower face and smile BTX treatment produces transformative aesthetic results with minimal downtime and no surgical risk. The specific benefits by indication:

Gummy smile correction produces the most dramatic per-unit aesthetic improvement of any BTX application. As little as 4–8 units total relaxes the LLSAN sufficiently to reduce gingival exposure by 3–5 mm during natural smiling, converting a cosmetically distressing gummy smile to one that exposes only tooth and minimal gum. Patient satisfaction rates in published series exceed 90%, and the treatment is equally effective in male and female patients. The BTX effect on gingival display typically lasts 3–5 months; with repeated treatment, some patients develop progressive muscle atrophy that produces longer-lasting results.

DAO injection for downturned corners produces a visible lifting of the oral commissures at rest within 5–10 days, eliminating the chronically sad or stern expression that many patients find affects how others perceive them. It pairs exceptionally well with small-volume hyaluronic acid filler at the oral commissures (marionette lines), with the BTX addressing the causative muscular pull and the filler restoring lost volume — the combination produces results greater than either alone.

The lip flip creates the appearance of increased upper lip volume without filler, making it particularly attractive for patients who want a subtle enhancement without the risk of over-augmentation or the cost and longevity of filler. It is also highly effective for treating the 'disappearing upper lip' on smiling — a common complaint where the upper lip rolls inward when the patient smiles broadly.

Mentalis smoothing produces a clean, polished chin appearance and is particularly effective when combined with chin filler to address both the textural irregularity (BTX) and volume deficit (filler) simultaneously. The combined 'chin flip' technique — BTX mentalis plus filler — is one of the most popular lower face treatment combinations in current aesthetic practice.

Lower face and peri-oral BTX treatment carries specific risks that are proportionally greater than those of upper face BTX, because the muscles of the lower face serve critical functions (speech, eating, drinking, facial expression) and because misdirected toxin in this small anatomical region can affect multiple adjacent muscles:

Smile asymmetry is the most feared complication and occurs when BTX diffuses beyond the intended muscle or is placed asymmetrically between the two sides. Even a difference of 1–2 units between left and right sides of the LLSAN, DAO, or zygomaticus can produce a visibly asymmetric smile that affects the patient's quality of life and communication. Asymmetry is managed by identifying which side is over-treated and, if possible, correcting the contralateral side at the 2-week follow-up to balance the result. In most cases asymmetry is temporary (resolving as the BTX wears off), but it can persist for 3–4 months and is distressing during this period. Prevention requires: precise bilateral injection at anatomically equivalent landmarks, meticulous dose consistency between sides, and using the same syringe and needle technique on both sides.

Lip incompetence and speech difficulty: Over-relaxation of the orbicularis oris (from excessive lip flip dosing) impairs lip seal, causing difficulty drinking from a straw or bottle, playing wind instruments, and forming certain speech sounds (bilabial consonants — 'p', 'b', 'm'). Patients who rely on lip seal professionally (musicians, broadcasters, athletes) must be counselled explicitly, and the orbicularis dose must be conservative (never exceeding 4 units total in inexperienced hands).

Drooping of the upper lip: Injection of the LLSAN placed too deeply or too medially may inadvertently affect the deeper portion of the orbicularis oris or the levator anguli oris, causing an asymmetric droop of the upper lip on smiling or at rest. This is very distressing for patients and is one of the most difficult BTX complications to manage as no antidote exists — the injector must await natural resolution.

DLI injection causing lower lip asymmetry: DAO injection placed too close to the midline affects the depressor labii inferioris (DLI) — the muscle that pulls down the central lower lip during smiling (producing the natural lower lip asymmetry visible in many people when they smile fully). Injecting the DLI inadvertently produces an inability to lower the ipsilateral lower lip during smiling — a visible and asymmetric result. Keeping DAO injections well lateral to the midline and using the lowest effective dose prevents this.

Bruising and vascular injury are risks in all injection locations due to the rich vascular anatomy of the lower face, including the facial artery and labial arteries. Using a fine-gauge needle, applying gentle digital pressure post-injection, and avoiding known vascular landmarks minimises but does not eliminate bruising. Intravascular injection causing vascular occlusion is extremely rare at these doses and sites but all injectors should be trained in recognising and managing this emergency.

A follow-up appointment at 2 weeks post-treatment is standard for all lower face BTX procedures. At this point the full effect of the treatment is established (onset is complete by day 10–14 for these small muscle doses) and any asymmetry, under-treatment, or unexpected results can be identified and managed. Dynamic photographic and video assessment at rest, during natural smile, and during maximum expression allows direct comparison with baseline recordings made at the initial consultation.

If smile asymmetry is identified at the 2-week review, corrective dosing on the contralateral (under-treated or over-active) side may partially compensate — this is possible when the correction can be achieved by adding toxin to the opposite side. Over-treated sides cannot be reversed and must be awaited. For gummy smile, re-assessment measures the residual gingival display during natural smiling and determines whether a top-up injection is needed (common in patients with more prominent LLSAN hyperactivity).

For DAO and mentalis treatment, patients are asked about functional changes — difficulty eating, speaking, or expressing emotion — and these are documented. Mild functional effects are expected to resolve within 4–6 weeks as patients adapt neurologically to the altered muscle balance.

Retreatment is scheduled when the patient notices the return of the original concern — typically 3–4 months after gummy smile and DAO treatment, 2–3 months after lip flip (due to shorter-acting smaller doses), and 3–4 months after mentalis treatment. As with masseter and gastrocnemius, serial treatments over 2–3 years produce cumulative atrophy of the targeted muscles, resulting in progressively longer-lasting results and sometimes reduced dosing requirements at maintenance sessions.

Lower face smile BTX treatment involves relatively low product volumes compared with upper face wrinkle treatment or masseter slimming — gummy smile correction uses only 4–12 units total, DAO injection 4–10 units, and lip flip 2–4 units. However, pricing in most clinics reflects the expertise and time required rather than purely product volume, particularly for complex multi-muscle lower face treatments requiring dynamic analysis and careful planning.

Indicative per-treatment pricing (for lower face / smile combination treatments):

• South Korea and Southeast Asia: USD 150–400 for lower face combination (masseter + smile enhancement); individual indications (gummy smile alone) USD 100–250.
• United Kingdom: GBP 150–350 per area; lower face combination GBP 300–600.
• Australia / Canada: AUD/CAD 200–500 per indication; lower face combination 400–800.
• United States: USD 300–700 per indication; lower face combination USD 600–1,500 depending on provider type (plastic surgeon vs. dermatologist vs. nurse injector in medispa).

Many clinics offer lower face 'packages' combining masseter slimming + gummy smile correction + DAO + lip flip at a bundled price that represents a saving over individual treatment costs. Given the short duration of effect (3–4 months), annual treatment cost for a full lower face BTX programme typically ranges from USD 600–3,000 depending on the location and combination of indications treated. Injectable filler additions (for marionette lines, oral commissures, or lip volume) are charged separately and add USD 400–1,200 per product used. The total programme including maintenance may cost USD 1,500–5,000 annually for a comprehensive lower face aesthetic plan.

Lower face aesthetics can be approached through a range of complementary and alternative modalities, and the optimal treatment plan often combines BTX with other approaches for a more complete and longer-lasting result:

Dermal fillers (hyaluronic acid, HA) are the most important complementary treatment to BTX in lower face aesthetics. While BTX addresses muscle dynamics (relaxing overactive muscles), HA fillers address volume — restoring lost fat compartment volume in the marionette lines, lifting the oral commissures with a small filler bolus, augmenting the lips (direct lip augmentation is distinct from the lip flip), and smoothing static lines. The combination of HA + BTX in the lower face is synergistic: BTX reduces the repetitive muscle movement that degrades filler faster and prevents muscle-pull-related volume migration, while filler provides the volumetric correction BTX cannot achieve.

For gummy smile not responsive to BTX (due to vertical maxillary excess as the dominant cause), orthognathic surgery (Le Fort I maxillary impaction osteotomy) is the definitive corrective treatment. Crown lengthening (gingival recontouring) by a periodontist addresses gummy smile caused by gingival hyperplasia or altered passive eruption, where gum covers an excessive proportion of the tooth crown.

Thread lifting of the oral commissures provides a mechanical lift of the corner of the mouth using barbed absorbable sutures and is an alternative to DAO BTX for patients who prefer a more immediate and longer-lasting (12–18 months) result, though it carries higher procedural risks.

Surgical lip lift (subnasal bullhorn or corner lip lift) provides permanent upper lip elongation and correction of downturned corners for patients who want lasting improvement beyond what BTX and filler can provide. It involves small surgical incisions under the nose (or at the corners of the mouth) and permanent sutures; results last 5–10+ years. This surgical option is appropriate for patients with severe ptosis of the oral commissures or significant upper lip lengthening from ageing.