Making your mouth physically wider is surgically possible, but the procedure exists almost entirely for medical reasons rather than cosmetic ones. The surgery, called commissuroplasty, was developed to help people whose mouth opening has become dangerously small due to burns, autoimmune disease, or prior operations. For someone without a medical condition, the realistic options are much more limited and lean heavily on illusion rather than structural change.
What Actually Controls Mouth Width
Your mouth corners are not simple hinges. Each corner sits at a junction called the modiolus, a dense knot of muscle fibers where several facial muscles converge. Recent anatomical research identified a ligament at this junction that connects the orbicularis oris (the muscle encircling your lips), the buccinator (the cheek muscle), and the zygomaticus major (the muscle that pulls your mouth upward when you smile) to the overlying skin and deeper supportive structures.1PubMed Central. Discovery of the Ligament of Modiolus: Anatomical Insights and Clinical Relevance This means your mouth width is not determined by a single tissue you could simply stretch or cut. It is anchored by an interlocking web of muscles, ligaments, and skin that together define how far apart your mouth corners sit and how widely they can move.
This architecture is why mouth width is remarkably stable in healthy adults. You can smile wider by training yourself to engage the zygomaticus more, but the resting distance between your mouth corners stays the same. It is also why any permanent widening requires surgery rather than exercises or devices.
When a Wider Mouth Is a Medical Necessity
The clinical term for a mouth that has become abnormally small is microstomia. People with microstomia can struggle to eat, speak, maintain oral hygiene, or even open wide enough for a dentist to work. The condition is not cosmetic; it is functional and sometimes life-threatening, particularly when it prevents adequate nutrition or makes emergency intubation difficult.
The common causes include scleroderma (an autoimmune disease that tightens and hardens the skin), burns to the face, surgical removal of oral cancers, and severe scarring of the jaw joint.2PubMed Central. Microstomia-a treatment challenge to a prosthodontist Burn survivors are an especially large group: scar tissue around the mouth contracts over time, gradually pulling the mouth opening smaller. In severe cases, the opening can shrink to just 15 millimeters, barely wider than a thumb.
If you are reading this article because you feel your mouth looks narrow but have no diagnosed condition, your situation is fundamentally different from the cases surgeons operate on. The surgical and rehabilitative tools described below were designed for functional restoration, not aesthetic widening in otherwise healthy mouths.
Commissuroplasty and How It Works
Commissuroplasty is the main surgical approach for widening the mouth. The surgeon cuts through the scar tissue or tight skin at one or both mouth corners, then rearranges local tissue flaps to cover the newly created raw surfaces and reconstruct something resembling a natural commissure. Without flap coverage, the wound would heal by scarring down again, often recreating the original problem.
Several flap techniques exist. One reported approach divides the dry lip into muscle and skin flaps that are transposed into the new opening. In a published case of postoperative microstomia, this method improved mouth opening enough for the patient to wear dentures again.3PubMed Central. Commissuroplasty Using Split Dry Lips: A Case Report Another technique uses rhomboid-shaped flaps taken from the inner cheek lining. In a particularly dramatic case involving an infant born with an extremely small mouth, surgeons used four such flaps to reconstruct both mouth corners. The primary goal was survival: allowing the child to eat and eventually develop normal speech.4PubMed Central. Extreme Microstomia in an 8-Month-Old Infant: Bilateral Commissuroplasty Using Rhomboid Buccal Flaps
The gains can be substantial. One case report documented a patient whose mouth opening went from 15 millimeters before surgery to 55 millimeters afterward, accomplished through a Dieffenbach commissuroplasty on both sides.5PubMed Central. Microstomia Release in Post-burn Contractures: A Case Report That kind of improvement is transformative for daily life, though the starting point (15 mm) was severely restricted.
Why Commissuroplasty Is Not a Cosmetic Procedure
No mainstream cosmetic surgery practice offers commissuroplasty to healthy patients who simply want a wider-looking mouth. The reasons are straightforward. Cutting into the mouth corners risks permanent scarring at a highly visible part of the face. The modiolus, that muscular junction at each corner, controls smile symmetry and lip competence (the ability to keep your lips sealed at rest). Damage to it can cause drooling, asymmetry, or difficulty with oral function. For a patient with microstomia, those risks are worth taking because the alternative is worse. For someone with a normal-sized mouth, the risk-benefit calculation does not add up.
The Relapse Problem
Even after a successful commissuroplasty, the mouth tends to contract again as new scar tissue forms during healing. This is why many protocols pair surgery with splints, devices worn inside the mouth to hold it open during recovery. A modified approach combining commissuroplasty with semidynamic acrylic splints has shown effective and stable outcomes in maintaining the widened opening. Without a splint or ongoing stretching, relapse is common, which underscores how powerfully the body’s healing response fights against a wider mouth opening.
Non-Surgical Stretching and Splints
For patients whose microstomia is mild or whose surgical risk is high, non-surgical stretching is sometimes the first line of treatment. This involves mechanically forcing the mouth open over time, either with specially designed splints or with exercises that pull the commissures apart.
A study of intraoral stretching in patients with long-term orofacial contractures found modest improvements. One participant’s mouth opening increased from 30 millimeters to about 31.4 millimeters after five weeks of intervention. A second participant gained more, going from 50 millimeters to 56 millimeters over eight weeks.6PubMed Central. Managing Long-term Orofacial Contractures and Microstomia Through Intraoral Stretching The gains are real but small, and they require sustained effort. Stop stretching, and scar tissue will tighten again.
Dynamic mouth splints designed for burn patients have also shown functional improvements in case studies. A modified splint described in the burn care literature demonstrated that combining splint use with ongoing therapy improved both mouth opening and the ability to eat and speak.7PubMed. A modified dynamic mouth splint for burn patients These devices are custom-fitted and worn for extended periods, often months. They are medical devices prescribed for scar management, not products you can buy to widen a healthy mouth.
The takeaway from the non-surgical evidence is that even in people with pathologically tight mouths, widening without surgery is slow and limited. In a healthy person without scar contracture, there is no tight tissue to stretch, so these techniques would not produce meaningful change.
Jaw Surgery and Its Effects on Lip Width
Orthognathic surgery, the broad category of operations that reposition the upper jaw, lower jaw, or both, changes how the lips drape over the new skeletal position. People sometimes wonder whether jaw surgery could make their smile or mouth look wider, since the underlying bone is being physically moved.
The answer is complicated. Studies tracking three-dimensional soft tissue changes after mandibular setback surgery (where the lower jaw is moved backward) found that the mouth corners shifted backward and downward. However, the actual width between the corners did not change significantly.8PubMed Central. Changes of lip morphology following mandibular setback surgery using 3D cone-beam computed tomography images Upper lip vermilion length increased, and lower lip vermilion length decreased, meaning the visible red part of the lips changed shape even though the mouth corners stayed roughly the same distance apart.
Research on bimaxillary surgery (repositioning both jaws) tells a similar story. One study using stereophotogrammetry found significant changes in lip area and height, particularly an increase in upper lip area and a decrease in lower lip dimensions, but it focused on vertical and surface changes rather than horizontal widening.9PubMed Central. Assessment of lip morphology changes after bimaxillary orthognathic surgery using stereophotogrammetry Jaw surgery reshapes the lower face dramatically, but it does not reliably make the mouth wider in the way most people imagine.
What jaw surgery can do is change how wide your smile appears by altering how the lips sit relative to the teeth and cheeks. That distinction matters: perceived smile width and actual inter-commissural distance are not the same thing.
Orthodontics and the Buccal Corridor Question
If you have searched for ways to make your smile look wider, you have probably encountered the term “buccal corridor.” These are the dark spaces visible between your teeth and your cheeks when you smile. A narrow dental arch creates larger buccal corridors, which can make the smile appear less full. Orthodontic expansion of the upper jaw, particularly a technique called mini-screw-assisted rapid palatal expansion (MARPE), can widen the dental arch and reduce those dark spaces.10APOS Trends in Orthodontics. Buccal corridor and gummy smile treatment with MARPE and gingivoplasty: A 2-year follow-up case report
Here is where things get interesting, though. Research comparing smile attractiveness in patients treated with and without rapid maxillary expansion found no significant difference in how attractive observers rated the smiles. There was also no significant correlation between buccal corridor size and smile attractiveness.11PubMed. Smile attractiveness in cases treated with self-ligating and conventional appliances with and without rapid maxillary expansion In other words, while expanding the dental arch does physically reduce those dark spaces, outside observers do not consistently notice or care. The perceived benefit may be more about how you feel about your own smile than about how others judge it.
This does not mean palatal expansion is pointless. It has well-established benefits for breathing, bite alignment, and dental crowding. But if your only goal is making your mouth look wider to others, orthodontics alone is unlikely to produce the dramatic difference you might expect.
Cosmetic Approaches That Simulate Width
The most accessible way to make your mouth appear wider is through cosmetic techniques that create an optical illusion. Lip liner applied slightly beyond the natural lip border at the corners, combined with lighter shades at the center and darker tones blended outward, can make the mouth look broader. Highlighting the cupid’s bow and applying a touch of concealer just outside each corner to blur the boundary between lip and skin are standard techniques in professional makeup artistry. These tricks exploit the way the brain interprets contrast and shadow to estimate facial proportions.
Dermal fillers in the lips can also change the perception of mouth width, though they primarily add volume and projection rather than literally widening the commissures. A skilled injector can place filler strategically near the mouth corners to create a subtle lift and outward pull, but the underlying distance between the corners stays the same. Overfilling or poorly placed filler in this area carries risks of distortion and an unnatural appearance, so this is firmly in the category of “discuss with a board-certified dermatologist or plastic surgeon.”
Neither makeup nor filler changes the actual structural width of your mouth. They change how the mouth reads in a photo or across a room. For many people, that distinction does not matter much: looking wider is the goal, and these methods achieve it without surgery.
Predicting Soft Tissue Changes Before Surgery
For patients who are undergoing jaw surgery for medical or orthodontic reasons and want to know how their lips will change, the field has made real progress in predictive modeling. Finite element modeling combined with a realistic lip-sliding effect has improved the accuracy of simulations in the lip region specifically, which has historically been the hardest part of the face to predict after bone repositioning.12PubMed Central. A novel incremental simulation of facial changes following orthognathic surgery using FEM with realistic lip sliding effect Deep-learning algorithms trained on 3D photographs and imaging data can now predict the post-surgical soft tissue profile of the lower face with clinically acceptable accuracy.13PubMed. Three-dimensional virtual planning in mandibular advancement surgery: Soft tissue prediction based on deep learning
This technology does not help you widen your mouth, but it is relevant if you are considering jaw surgery for other reasons and want to understand how it will affect your lip shape. Being able to preview the likely soft tissue outcome before the operation reduces surprises and helps surgeons plan the bone movements to achieve the best facial balance.
Why Human Mouths and Jaws Keep Getting Smaller
There is a broader context worth knowing about. Modern human jaws are considerably smaller than those of our ancestors, and the change happened far too quickly to be driven by genetic evolution. Comparisons of medieval and modern skulls show that tooth crowding was much less common in the Middle Ages, and hunter-gatherer populations had roomy jaws with little to no malocclusion. The shift toward smaller jaws and more crowded teeth has accelerated over just the last few hundred years and appears linked to changes in diet and chewing behavior rather than DNA.14PubMed Central. The Jaw Epidemic: Recognition, Origins, Cures, and Prevention
Softer diets during childhood provide less mechanical stimulus for jaw growth, which may result in narrower dental arches and less forward growth of the lower face. While this research focuses on jaw size and tooth crowding rather than mouth width per se, the two are related. A narrower maxilla means a narrower palate, less room for the tongue, and a smile that may appear less broad relative to the rest of the face. Some researchers have framed this as an epidemic, arguing that preventive approaches, such as encouraging harder chewing in childhood, could be more effective than corrective orthodontics later.
This evolutionary angle does not give you a way to make your mouth wider today, but it does reframe the question. If you feel like your mouth is too narrow, you are not alone, and the issue may be partly structural, rooted in how modern lifestyles shape facial development during growth. Palatal expansion in childhood and adolescence, when the bones are still growing, can address some of this. In adults, the options are more constrained because the sutures in the upper jaw have largely fused, which is exactly why techniques like MARPE use mini-screws to force the bone apart mechanically.