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Muscle Relaxing injections target the masseter muscle, the large chewing muscle at the back of the jaw, to gradually slim a square or prominent jawline and ease tension from clenching or grinding. Because the effect builds gradually as the muscle relaxes and shrinks, masseter treatment tends to suit patients looking for a softer, more V-shaped lower face without surgery, particularly where jaw width is driven by muscle bulk rather than bone structure.
The masseter is one of the main muscles used for chewing, running from the cheekbone down to the lower jaw. In people who clench or grind their teeth frequently, or who simply have a naturally strong bite, this muscle can become enlarged, contributing to a wider or more square jawline when viewed from the front.
Injections into the masseter work through chemodenervation, as it reversibly blocks acetylcholine release at the neuromuscular junction, reducing how forcefully the muscle contracts. With less repetitive, forceful use, the muscle gradually loses bulk over the following weeks, a process similar to how any muscle shrinks with reduced activity. This is different from jawline filler, which adds volume along the mandible, or from bone-reduction procedures, which alter the underlying skeletal structure.
Masseter hypertrophy refers to enlargement of the muscle, often from years of habitual clenching, grinding, or simply a strong, frequently used bite. It is more noticeable in some facial structures than others and can make the lower face appear wider or more square regardless of the underlying bone shape.
Bruxism, the habitual grinding or clenching of teeth, often during sleep or under stress, is a common driver of masseter overuse. Beyond its aesthetic effect on jaw width, bruxism is also associated with jaw fatigue, tension headaches, and, in some cases, tooth wear, which is one reason masseter treatment is used for both cosmetic and functional reasons.
Muscle relaxation itself begins within days to about two weeks, similar to wrinkle-relaxing treatment elsewhere in the face. However, the visible slimming of the jawline is a separate, slower process: it reflects the muscle gradually losing bulk from reduced use, which takes longer to become apparent than the initial relaxation of muscle strength.
Most patients begin to notice a softer jaw contour from around four to eight weeks after treatment, with the fullest slimming effect often continuing to develop, and becoming more pronounced with a second treatment cycle over the following months.
By reducing the force and frequency of masseter contraction, treatment can lower resting muscle tension and reduce the intensity of clenching, which some patients experience as less jaw fatigue, fewer tension headaches, or reduced discomfort around the temporomandibular joint.
Clinical studies of muscle relaxing treatment for bruxism have documented reduced resting muscle tension, decreased stiffness during contraction, and normalised relaxation time on muscle testing, with some patients reporting improved sleep quality and reduced jaw or tooth discomfort. Benefit tends to be most pronounced in patients who start with the highest baseline muscle tension, and self-reported symptom relief does not always track exactly with the measured muscle changes, so individual response varies.
Masseter wrinkle-relaxing injections may suit patients with a visibly square or wide lower face driven by muscle bulk, a history of teeth grinding or clenching, or jaw tension and fatigue, who are looking for a non-surgical option with no real downtime. It is not intended to change bone structure and is best assessed against your specific jaw anatomy during a consultation.
The muscle-relaxing effect generally lasts a similar duration to wrinkle-relaxing treatment elsewhere in the face, around three to six months, though the slimming effect on jaw contour tends to be more gradually cumulative and, with repeat treatment, can build over successive cycles.
Most patients repeat treatment every four to six months initially, with some finding they can space out sessions further once the muscle has been consistently reduced in size over one to two years.
The masseter sits close to other muscles involved in smiling and chewing, so imprecise injection technique or excessive dosing can occasionally affect nearby muscle function. Careful assessment of muscle boundaries and conservative, appropriately placed dosing are used to minimise this risk.
Because masseter size and strength vary significantly between individuals, dosing is not standardised across all patients. Your clinician will assess muscle bulk by palpation, sometimes while you clench, to determine an appropriate dose and injection pattern for your anatomy.
A slimmer, more relaxed jawline starts with an accurate assessment of whether your jaw width is driven by muscle, bone, or a combination of both.
At VIDASKIN, masseter treatment is planned around your individual muscle anatomy, bite pattern, and aesthetic goals, using precise dosing to support a softer jawline while maintaining natural chewing function.
To learn more or book a consultation, visit us here today.
Masseter wrinkle-relaxing injections reduce the size and activity of an overworked jaw muscle, generally narrowing the lower face. Jawline filler adds volume and definition along the mandible. Some patients benefit from one, the other, or both, depending on their anatomy.
At appropriate doses, chewing function is generally preserved. Excessive dosing can occasionally cause temporary weakness, which is why individualised dosing and technique matter.
matter.
Most patients notice initial softening after one session, with slimming becoming more pronounced over two to three treatment cycles, spaced roughly four to six months apart.
Many patients report reduced clenching intensity and jaw tension after treatment, though individual symptom relief varies and should be discussed with your dentist alongside any dental management.
The muscle-relaxing effect typically lasts three to six months, though jaw slimming tends to build cumulatively with repeated treatment over time.
Dr. Kay Low is a UK-trained medical doctor with over 7 years of clinical experience across the UK and Singapore, specialising in aesthetic medicine. A graduate of the University of Cambridge, she has worked across multiple medical and surgical disciplines in the UK and Singapore before completing postgraduate training in Family Medicine and advanced training in aesthetic medicine.
