If you've ever consulted the internet to find tricks for achieving knife-sharp features, you've likely come across jawline filler before and after photos. Plenty of people have shared their results from the treatment, showing off their newly sculpted face shape with a smile.

While seeing others folks' results can be a major selling point, ideally you'll dig a little deeper into the treatment before deciding to get jawline filler or anything with semi-permanent results, for that matter. So, that's where this article comes in. Grab your pen and paper because jawline filler 101 is in session.

During a jawline filler treatment, a physician, nurse practitioner, or registered nurse injects a dermal filler (a gel-like substance that can add volume to an area of your face or body) in spots along the jaw. This can temporarily change the shape of your jaw, offering results that last anywhere from six to 12 months, according to Paul Jarrod Frank, M.D., a New York-based cosmetic dermatologist and author of The Pro-Aging Playbook.

Oftentimes, the goal is to create sharper lines in people who are unsatisfied with the softness of their jaw, says Dr. Frank. For example, jawline filler can have the effect of creating "harmony" in those who have stronger features in the upper and mid-region of their face, adds Shirley Madhère, M.D., a New York-based plastic surgeon. (Related: Can You Do Anything to Define Your Jawline?)

Beyond adding balance or making your face look more sculpted, jawline filler can create a lifting effect. Some people rely on jawline filler "to give the visual impression that their neck is lifted, reducing heaviness in the jawline and neck area," notes Dr. Frank. The filler can restore volume back to the jaw area, pulling up on your neck skin in the process.

Providers will often use a cannula, which looks like a long, blunt-tipped needle, rather than a needle to inject filler in the jaw area, says Dr. Frank. "[With a cannula], you're able to place the filler along the path that you want to without having to make multiple punctures," leading to less bruising and trauma, he explains. "[That said, some] injectors may choose a needle over a cannula if that's what they're used to." Regardless of the tool, they can also adjust where they put the filler based on your desired results. Placing the filler underneath and also lateral to the jawline will create a squareness; placing it underneath the jawline rather than building it up on the side will lead to a more heart-shaped face with a tapered jaw, says Dr. Frank.

Of the various types of injectable filler, hyaluronic acid-based filler is the most commonly used option for the jaw area, says Dr. Frank. (Refresher: Hyaluronic acid is a sugar molecule that occurs naturally within the skin, and it's often the star ingredient in fillers that are used for adding volumne to lips, cheeks, or under-eyes.) Typically the thicker varieties of hyaluronic acid filler (e.g. Juvederm Voluma XC and Restylane Defyne), are used for the jaw since they tend to be superior at mimicking the look of a strong bone structure, says Dr. Madhère. "Some fine gel fillers may not be enough to create the new contour and may be too compressible under the weight of the skin of the lower face," she explains. One particular advantage of hyaluronic acid fillers? They can be reversed. So, if you have a change of heart or think your results are a case of jawline filler gone wrong, you can have an enzyme called hyaluronidase injected into the area to dissolve the filler.

Another common type of filler for the jaw area is calcium hydroxyapatite, which, FWIW, Dr. Frank prefers to use when treating this portion of the face. "The biggest issue is that hyaluronic acid products retain a lot of fluid; they create a plumpness, which is not so much of a problem if you're injecting a cheekbone or a lip," he says. "But if you're trying to create definition in the face in the jawline, having a product that retains a lot of water can just make the face look puffy."

Calcium hydroxyapatite, which is a material found in bones, "gives more of a defining aesthetic which is more appropriate for the area," he says. And while it cannot be dissolved, "the thicker hyaluronic acid fillers like Voluma are not easy to dissolve either," points out Dr. Frank. "They're not as reversible as they say they are." Calcium hydroxyapatite jawline filler (e.g. Radiesse) tends to last longer than hyaluronic acid filler, lasting about one year.

As with getting filler in other areas, minor bruising and swelling are common side effects in the days immediately following a jawline filler appointment. "Nodules or bumps may form if the filler is not placed correctly," says Dr. Madhère. Although less common, some people can develop skin reactions, such as more serious swelling and changes in skin color, especially if they have a history of similar reactions to filler, she notes. "Some of the skin reactions may be allergic reactions, which typically resolve in a few days to one week with some care."

And then there's the chance of a more severe but rare complication wherein a person experiences blood vessel damage or blockage if the filler is placed incorrectly. "Healthy skin relies on support from blood circulation," says Dr. Madhère. "Anything that interrupts or disrupts that blood supply to the skin will result in the death of that tissue ("necrosis") or tissue slough. Tissue necrosis is a complication that is not easy to correct. Ideally it must be prevented," she says. (Related: Can Jawzrsize Actually Slim Your Face and Strengthen Your Jaw Muscles?)

Judging by the number of "this is your sign to get jawline filler" posts on TikTok, though, plenty of people end up seemingly satisfied with their results. But, as with any cosmetic procedure, there's always a possibility that your expectations won't match up with your results. "Unsatisfactory results may be due to too much or insufficient filler, thereby not achieving the desired result," says Dr. Madhère.

"If done inappropriately or in the wrong candidate, it can make the face look overly square," says Dr. Frank. Another example of jawline filler gone wrong results when people turn to jawline filler in hopes of taking attention away from their jowls (skin sagging below the jawline), adds Dr. Frank. "What the filler does is it just weighs the jawline down and just makes it look heavier than it originally did."

Jawline filler cost can vary greatly depending on where you live and who you choose as your provider. Filler is typically charged by the syringe (even if the practitioner uses a cannula, as the formula comes packaged in a syringe), and injectors usually use one to four syringes of filler for the area, depending on the desired results, according to the American Society of Plastic Surgeons. (FWIW, a syringe typically gets attached to a cannula, Since hyaluronic acid filler usually costs around $700 to $1,200 per syringe, and calcium hydroxyapatite filler costs around $800 to $1,200 per syringe, you can expect to pay anywhere from $700 to $4,800 per treatment. (Related: A Complete Guide to Filler Injections)

If you're hoping to alter the look of your jaw, there are additional methods you can look into beyond jawline filler. Injecting neurotoxins (e.g. Botox or Xeomin) along your jawbone and platysmal bands (muscles that run down your neck) can tighten the angle of your jaw; injecting them into your masseter muscle below your ears can lead to a more heart-shaped face, as Shape previously reported. The neurotoxin route might be worth looking into if you're not after added volume.

There's also the surgical route. "For people seeking a more refined lower facial contour, jawline fillers offer a more flexible option to 'try out' the look before committing to a more permanent option such as a facial implant," notes Dr. Madhère. Or, if a patient's interested in getting filler in the jawline for lift, they might be interested in getting a neck lift instead, adds Dr. Frank.

If you decide to explore jawline filler, a skilled injector can help you suss out if it makes sense for you, and if so, hook you up with the results you're after.