Botulinum toxin and smile design in dentistry
- Muscle
- Highlighted area
Quick facts
- Topic
- The role of toxin in smile design, in dialogue with dentistry
- Structures
- Upper lip elevators, zygomaticus, orbicularis, modiolus
- Partnerships
- HOF, orthodontics, restorative dentistry, periodontics and prosthodontics
- Main safeguard
- Teeth and gums define the planning, the toxin is one of the options
The smile is where HOF and dentistry meet. For the dentist who does harmonization, and for the professional from another background who works with a dentist partner, smile design involves teeth, gums, lips and muscles that move together. Botulinum toxin comes in as one option for adjusting lip movement, and it is at this interface that gains are usually made, and mistakes too.
This text presents the dialogue between the toxin and smile design at a review level. It gives no dose, injection point or protocol. Management and scope of practice are defined by the qualified professional and the rules of their professional council.
What is smile design?
It is the planning of the relationship between the teeth, gums, lips and face during the smile. Elements that usually enter the analysis:
- Smile line: how much tooth and gum show when smiling.
- Smile arc: the relationship between the curve of the upper teeth edges and the lower lip.
- Buccal corridor: the dark space between the teeth and the corner of the mouth.
- Incisor display at rest and when smiling.
- Symmetry between sides, of the lip and the midline.
- Lip dynamics, that is, how it moves in speech and expression.
A good part of these elements is dental and skeletal. But the movement of the upper lip, determined by the muscles, defines how much of the whole shows, and that is where the toxin can act.
Which muscles move the smile?
The upper lip and the mouth corner are moved by a group of muscles that converge on the modiolus. The most cited:
| Muscle | Role | Relevance to smile design |
|---|---|---|
| Levator labii superioris | Lifts the upper lip | Main one in gum display |
| Levator labii superioris alaeque nasi | Lifts the lip and the ala | Contributes to the anterior gummy smile |
| Zygomaticus major | Pulls the corner up and outward | Defines the lateral opening of the smile |
| Zygomaticus minor | Lifts the upper lip, laterally | Influences lateral display |
| Levator anguli oris | Lifts the corner | Contributes to the contour of the smile |
| Risorius | Pulls the corner laterally | A "stretched" smile look |
| Orbicularis oris | Sphincter | Balance and competence of the lips |
| Depressor anguli oris | Lowers the corner | Antagonist |
Acting on any one of them affects the whole, which is why the reasoning starts from the patient's smile dynamics and not from an isolated point.
When the toxin enters the conversation
The most discussed use is for the gummy smile, detailed in botulinum toxin for the gummy smile. Other situations in which the conversation may arise:
- Smile with excessive gum display from hyperactivity of the lip elevators.
- Dynamic smile asymmetry, where one side rises more than the other.
- Preparation or complement to orthodontic treatment, when the aesthetics of the smile in motion are being discussed.
- Smile adjustment after orthognathic surgery, in dialogue with the team, as in harmonization after orthognathic surgery.
- Stabilizing the upper lip in restorative treatments, in selected cases.
That a situation is possible does not mean it is indicated. The decision depends on the cause of the problem and on assessing the whole.
The four most common causes of excess gum
| Cause | Feature | Role of the toxin |
|---|---|---|
| Muscular (lip hyperactivity) | The lip rises more than usual when smiling | May help |
| Skeletal (vertical maxillary excess) | Long face, short teeth at rest | Limited, surgery may be considered |
| Dental (altered passive eruption) | Short clinical crowns | Does not solve it, periodontics may be indicated |
| Combined | Several causes added together | Partial, usually part of a larger plan |
This table shows why the decision should not belong only to the person giving the toxin, but to a team that sees all four causes.
Partnership between HOF, orthodontics, restorative dentistry and periodontics
A well-conducted smile design usually involves more than one professional. The multidisciplinary team in HOF describes this model. In practice:
- Orthodontics assesses tooth position, occlusion and skeletal relationship.
- Restorative dentistry and prosthodontics work on tooth shape, size and color, including with veneers and smile planning.
- Periodontics assesses the gums and the possibility of gum contouring corrections.
- Surgery comes in when the cause is skeletal.
- HOF works on soft tissues, with toxin, filler and other options, according to the rules of each professional's council.
Who may do what varies between councils, and this page does not indicate scope of practice. What helps is a shared record of the case, with standardized photos, and clarity about who decides each step.
Risks and precautions
Changing the movement of the upper lip has implications for aesthetics and function:
- Asymmetric smile, if the response is uneven between sides.
- "Heavy" or long upper lip, when the effect is excessive.
- Speech changes, especially in sounds that depend on the upper lip.
- Loss of expression and a rigid smile.
- Spread to neighboring muscles, described in stiff smile after toxin.
- Difficulty drinking or blowing in cases of excessive effect.
How to talk to the patient
Patients often describe a smile in terms of "small teeth", "too much gum" or "crooked smile". Translating that into cause and option helps align expectations.
Harmy in the context of the smile
Harmy has the Mouth corner point and the Lips point, which are used to simulate volume with hyaluronic acid. The app does not simulate toxin in the smile, nor the movement of the smile, nor tooth design. The frontal photo is taken with a neutral expression, and the projection does not represent a smile.
In plans that combine smile and lip volume, the app can show the effect of volume at rest, while the smile design continues to be assessed clinically.
Timeline
Quick review
Smile design is teamwork. Botulinum toxin can be a good option when the cause is lip movement, as long as it is recommended after understanding the whole and carried out with respect for functional limits and the rules of each profession.
Frequently asked questions
Can botulinum toxin improve a gummy smile?
It can, in selected cases, by reducing the action of the upper lip elevators and letting the lip rise less. The indication depends on the cause of the gummy smile, which can be muscular, skeletal, dental or a combination.
Who should plan the smile design?
Ideally a team: the professional who gives the toxin and the dentist (orthodontics, restorative, periodontics) who assesses teeth, gums and occlusion. The division of roles follows the rules of each professional council.
Does the toxin change the shape of the teeth?
No. It changes the movement of the lip and, with it, how much tooth and gum show when smiling, but it does not change the shape or position of the teeth.
Why can the smile look odd after the toxin?
Because the smile muscles work in balance. Weakening one of them, or spread to its neighbors, can change symmetry and shape. Caution, prior assessment and follow-up reduce this risk.
Harmy images are illustrative simulations generated by AI from the patient's photo to support the conversation between practitioner and patient. They are not a promise of results. Indication, technique, product and volume are solely the decision of the licensed practitioner. This content is for information only and does not replace a clinical assessment.