Residency · Residency · Oral Maxillofacial Surgery
Injectable Therapeutics: Botulinum Toxin and Dermal Fillers
Introduction
Injectable therapeutics — botulinum toxin and dermal fillers — have become the most commonly performed minimally invasive aesthetic procedures worldwide. The OMFS surgeon's comprehensive understanding of facial anatomy, including the muscles of facial expression, neurovascular structures, and danger zones, provides an ideal foundation for safe and effective injectable treatment. These agents also have important therapeutic applications in OMFS practice.
Botulinum Toxin
Mechanism of Action
Botulinum toxin is a neurotoxin produced by Clostridium botulinum that inhibits the release of acetylcholine at the neuromuscular junction. It achieves this by cleaving SNARE proteins (specifically SNAP-25) required for vesicle fusion and neurotransmitter release, resulting in temporary, reversible chemodenervation of the target muscle. Onset occurs within 3 to 7 days, with peak effect at 2 to 4 weeks and a duration of 3 to 4 months. Function is eventually restored as nerve terminals regenerate through axonal sprouting.
Available Products
| Product | Generic Name | Conversion (vs Botox) | Duration | Key Feature |
|---|---|---|---|---|
| Botox | OnabotulinumtoxinA | 1:1 (reference) | 3-4 months | Most widely used; cosmetic + therapeutic |
| Dysport | AbobotulinumtoxinA | 2.5-3:1 | 3-4 months | Greater diffusion |
| Xeomin | IncobotulinumtoxinA | 1:1 | 3-4 months | No complexing proteins; lower immunogenicity |
| Jeuveau | PrabotulinumtoxinA | 1:1 | 3-4 months | Aesthetic-only approval |
| Daxxify | DaxibotulinumtoxinA | ~1:1 | 6-9 months | Peptide-stabilized; longer duration |
OnabotulinumtoxinA (Botox) is the most widely used product, FDA-approved for both cosmetic and therapeutic indications. AbobotulinumtoxinA (Dysport) has different dilution and diffusion properties, with a conversion ratio of approximately 2.5 to 3:1 relative to Botox. IncobotulinumtoxinA (Xeomin) is free from complexing proteins and may have lower immunogenicity. PrabotulinumtoxinA (Jeuveau) is approved specifically for aesthetic use. DaxibotulinumtoxinA (Daxxify) features a peptide-stabilized formulation that provides a longer duration of 6 to 9 months.
Cosmetic Applications
Glabellar lines (frown lines) are treated by injecting the corrugator supercilii and procerus muscles, typically with 20 units of Botox. Forehead lines are addressed through the frontalis muscle with conservative dosing of 8 to 15 units to avoid brow ptosis. Lateral canthal lines (crow's feet) involve injection of the orbicularis oculi with 8 to 12 units per side. Bunny lines are treated with 4 to 6 units in the nasalis muscle, and lip lines (smoker's lines) require very low doses of 2 to 4 units in the orbicularis oris to avoid functional impairment. Chin dimpling (peau d'orange) is managed with 4 to 6 units in the mentalis muscle, while platysmal bands receive 2 to 5 units per band using the Nefertiti lift technique. Gummy smile correction targets the levator labii superioris alaeque nasi with 2 to 4 units per side and represents a specific OMFS application. Masseteric hypertrophy is treated with 25 to 50 units per masseter for facial slimming and bruxism management.
Therapeutic Applications in OMFS
For TMJ disorders and bruxism, injection of the masseter and temporalis muscles at 25 to 50 units per muscle reduces clenching force. Sialorrhea is managed by parotid and submandibular gland injection to reduce salivary flow. Myofascial pain may be treated with trigger point injection for masticatory muscle pain, and post-surgical spasm can be reduced with targeted injections to protect surgical outcomes. Hemifacial spasm is addressed with targeted injection of the affected muscles.
Complications
Bruising and edema are the most common complications and can be minimized with ice and avoidance of blood thinners. Brow ptosis results from over-treatment of the frontalis and typically resolves in 2 to 4 weeks with proper technique being the best prevention. Eyelid ptosis occurs when the toxin migrates to the levator palpebrae and is treated with apraclonidine 0.5% drops. Asymmetry may result from uneven dosing or injection technique. Antibody formation is rare but can occur with frequent high-dose injections, leading to treatment resistance. Dysphagia is a dose-dependent risk with perioral or platysmal injection.
Dermal Fillers
Categories
| Filler Type | Example | Mechanism | Duration | Reversible | Key Consideration |
|---|---|---|---|---|---|
| Hyaluronic acid (HA) | Juvederm, Restylane | Volumization + hydration | 6-18 months | Yes (hyaluronidase) | Most commonly used; safest |
| Calcium hydroxylapatite | Radiesse | Volumization + collagen biostimulation | 12-18 months | No | Radiopaque; avoid in lips |
| Poly-L-lactic acid (PLLA) | Sculptra | Collagen biostimulation | Up to 2 years | No | Gradual; multiple sessions |
| PMMA | Bellafill | Permanent volumization | Permanent | No | Highest long-term complication risk |
Hyaluronic Acid (HA) Fillers
Hyaluronic acid fillers are the most commonly used filler category and are uniquely reversible with hyaluronidase. HA is a naturally occurring glycosaminoglycan with high biocompatibility that is cross-linked to varying degrees to achieve different viscosities and longevities. Major product families include Juvederm (Allergan) and Restylane (Galderma), with duration ranging from 6 to 18 months depending on the product and injection location. Different formulations are tailored for specific applications: softer products for lips, more viscous products for cheeks, and thin products for fine lines.
Calcium Hydroxylapatite (CaHA)
Radiesse consists of microspheres of CaHA suspended in a carboxymethylcellulose gel carrier. It functions as a biostimulatory filler, stimulating collagen biogenesis, with a duration of 12 to 18 months. It is not reversible and should not be used in the lips due to the risk of nodule formation. Because it is radiopaque on imaging, radiology should be informed if imaging is planned after treatment.
Poly-L-Lactic Acid (PLLA)
Sculptra is a biostimulatory agent that induces neocollagenesis, producing gradual volume increase over 2 to 3 months with multiple sessions required. Its duration extends up to 2 years, and it is indicated for diffuse facial volume loss from lipoatrophy or aging. The product is reconstituted 24 to 72 hours before injection and must be injected deeply at the subcutaneous or supraperiosteal level.
Polymethylmethacrylate (PMMA)
Bellafill is a permanent filler composed of PMMA microspheres in a collagen carrier. It is FDA-approved for nasolabial folds and acne scarring. Its permanent nature increases the risk of long-term complications including granuloma and biofilm formation.
Injection Techniques
Linear threading involves advancing the needle along the plane and depositing filler on withdrawal. Serial puncture uses multiple small bolus injections along the treatment area. Fanning employs a single entry point with multiple passes in a fan pattern. Cross-hatching layers perpendicular linear threads for volumization. Bolus injection places a deep supraperiosteal bolus for structural support in areas such as the malar eminence or chin. The cannula technique uses a blunt-tip cannula to reduce vascular injury risk and is preferred for high-risk areas.
Common Treatment Areas
Nasolabial folds are treated with HA filler injected at the deep supraperiosteal or subdermal level. Marionette lines are addressed in the depressor anguli oris region with pre-jowl sulcus filling. Lip treatment includes vermilion border definition, volume enhancement, and philtral column augmentation using soft HA products. Cheek and malar augmentation uses deep bolus injection to restore midface volume. Chin augmentation employs supraperiosteal bolus injection as an alternative to mentoplasty for mild deficiency. Tear trough treatment in the infraorbital hollow requires conservative technique due to the high risk of Tyndall effect. Jawline contouring defines the mandibular border and angle.
Danger Zones and Vascular Anatomy
Vascular occlusion is the most feared complication of dermal filler injection. The highest-risk areas include the glabella, where the supratrochlear and supraorbital arteries create risk of retinal artery occlusion via ophthalmic artery anastomoses. The nasal tip and alar region are supplied by the lateral nasal artery and angular artery. The nasolabial fold lies in the territory of the facial artery and its branches, and the temple contains the superficial temporal artery. Signs of vascular occlusion include blanching, pain disproportionate to the injection, livedo reticularis, and dusky tissue discoloration. Immediate management requires stopping the injection, aspirating, injecting hyaluronidase (200 to 300 units) into and around the affected area, applying warm compresses and nitroglycerin paste, administering low-dose aspirin, and obtaining urgent ophthalmology referral if visual changes are present.
Complications
Bruising and edema are the most common complications and can be minimized with cannula use, ice, and avoidance of anticoagulants. Asymmetry is corrected with additional filler or dissolved with hyaluronidase. Nodules and granulomas present as palpable lumps and are treated with hyaluronidase, steroid injection, or excision. Tyndall effect is a bluish discoloration from superficially placed HA that is dissolved with hyaluronidase. Biofilm and infection present as late-onset nodules treated with antibiotics and hyaluronidase. Vascular occlusion and necrosis represent a medical emergency and can cause blindness if the ophthalmic artery is affected. Filler migration from the injection site is more common with repeated high-volume treatments.
OMFS-Specific Considerations
Injectable fillers complement orthognathic surgery and osseous genioplasty for soft tissue refinement. Botulinum toxin serves as a valuable adjunct for TMD, bruxism, and gummy smile management. The OMFS surgeon's knowledge of facial vasculature and deep anatomy provides a safety advantage when performing these procedures. Hyaluronidase must always be readily available when injecting HA fillers, and thorough documentation of product type, lot number, volume, and injection sites is essential.
Clinical Pearls
Hyaluronidase is the reversal agent for HA fillers and must be immediately available as the critical rescue medication for vascular occlusion. The glabella is the highest-risk zone for filler injection because vascular occlusion can cause blindness via retrograde flow to the ophthalmic artery. Botulinum toxin for masseteric hypertrophy and bruxism is an expanding therapeutic application for the OMFS surgeon. The cannula technique significantly reduces the risk of vascular injury compared to needle injection in high-risk areas. Conservative dosing and staged treatment produce the most natural and safest outcomes.
References
- Carruthers J, Carruthers A. Procedures in Cosmetic Dermatology: Botulinum Toxin. 5th ed. Elsevier; 2022.
- Signorini M, et al. "Global Aesthetics Consensus: Avoidance and Management of Complications from Hyaluronic Acid Fillers." Plastic and Reconstructive Surgery. 2016;137(6):961e-971e.
- Niamtu J. "Cosmetic Injectable Agents in OMFS Practice." Oral and Maxillofacial Surgery Clinics of North America. 2019;31(4):539-554.
- DeLorenzi C. "New High Dose Pulsed Hyaluronidase Protocol for Hyaluronic Acid Filler Vascular Adverse Events." Aesthetic Surgery Journal. 2017;37(7):814-825.