Enhancing Facial Balance: 2 Dermal Filler Techniques for Chin Augmentation
The chin is a crucial component of facial proportion and, consequently, of how attractive someone is perceived to be. By age 35, the aging face exhibits a marked reduction in the number of osteons, osteocytes, and matrix nanocrystallites throughout the entire skull, including the mandible. An obtuse mandibular angle, chin retrusion, and an enlarged prejowl sulcus are the results of lost mandibular height and length. The appearance of the chin has been associated with not only attractiveness but also the perception of young, despite regional and gender variances in chin morphology. Therefore, chin augmentation for those with retrusion and correction in those who present for facial rejuvenation should be included in a comprehensive facial rejuvenation approach.
Genioplasty surgery, alloplastic implants, autologous fat transfer, and dermal filler injection are all options for chin augmentation. 16,668 surgical chin augmentations were carried out in 2016, according to the American Society of Plastic Surgery, a decrease of 4% from 2015 and 38% from 2000. Although the causes of the decline in surgical mentoplasty are unknown, the rising acceptance of minimally invasive treatment options is probably a contributing factor. The anatomy of the patient as well as the advantages and disadvantages of each treatment must be carefully considered in order to choose the optimal method for the patient. In the right patient, dermal fillers provide a nonsurgical, temporary solution to chin retrusion.
Structural Factors
Surface landmarks can be used to describe the chin in detail. On the chin, the menton is the point that projects the most inferiorly, while the pogonion is the point that projects the most anteriorly. Between the pogonion and the menton, the gnathion sits in the middle.
See below the figure where the progonion, gnathon, and menton is: pogonion (Pg) is the most anteriorly projected point on the chin. The menton (Me) is the most inferiorly projecting point. The gnathion (Gn) is the midpoint between the pogonion and menton.
The area of the chin is surrounded by distinct boundaries such as the mentolabial groove superiorly, the labiomandibular grooves laterally, and the submental ligaments inferiorly. This chin area is well-separated from the jowl and submental regions. The skin in this region is thick, approximately 2,000 to 2,5000 mm in adults, and the subcutaneous fat underneath is firmly attached to the skin and underlying muscles. The chin muscles consist of the depressor anguli oris (DAO), depressor labii inferioris (DLI), and paired mentalis centrally, with the DAO and DLI fibers interwoven with the platysma. The mandible forms the structural foundation for the chin area, situated deep to the muscular tissue.
The chin and lower lip region have complex blood supply with highly interconnected arteries that vary in pattern and location. The mental arteries, which are the primary blood supply to the chin, are terminal branches of the inferior alveolar arteries that arise from the maxillary artery. These mental arteries exit the mental foramina on either side of the lateral chin at the second bicuspid or approximately the mid-pupillary line. Additionally, the inferior labial artery and labiomental artery also contribute to the blood supply in the area. The labiomental artery may branch off either the facial artery or inferior labial artery and pass between the DLI and orbicularis oris muscles, coursing superficially to be submucosal in the lower lip. Similarly, after branching from the facial artery, the inferior labial artery runs deep to the DAO, coursing to the submucosal plane along the vermilion border of the lower lip. The submental artery, which is the largest of the cervical branches of the facial artery, arises as the facial artery exits the submandibular gland and runs anteriorly over the mylohyoid, crossing over the mandible near the mandibular symphysis. The submental artery gives rise to the vertical labiomental artery, which has both superficial and deep branches.
The inferior alveolar nerve travels through the mandible to exit as the mental nerve through the mental foramen and provides sensory innervation to the chin and lower lip.
See below the illustration of the arterial supply to the chin with the DAO removed. (From Anatomy to Surgery, Lips and Chin. 2014; p. 265)
Patient Evaluation for Chin Augmentation
Careful aesthetic evaluation of the patient is necessary to determine whether chin augmentation with fillers is appropriate. Patients should be examined both at rest and with animation. Photographs should be taken in the anteroposterior, oblique, and lateral positions. Video recordings of the patient in animation are also helpful in assessment and post-treatment follow-up to ensure a natural-appearing result.
There is a straightforward validated scale for chin projection, but it only takes into account anterior projection in the sagittal plane. Along with other elements of the lower face like the morphology of the labiomental sulcus and volume of the lateral chin (i.e., prejowl sulcus), consideration must also be given to the contour, vertical height, and transverse width of the chin. The teeth, lips, and nose should be taken into account as well because they play a crucial role in achieving an aesthetically pleasing appearance.
There are various standards for determining the ideal projection of the chin in the sagittal plane. One commonly used reference line is the Gonzalez-Ulloa line, which is a vertical line that starts at the nasion and extends downwards perpendicular to the Frankfurt plane - a line that runs from the inferior orbital rim to the superior margin of the external auditory meatus. An ideal chin is expected to align with, or be slightly behind, this line, without protruding beyond it. Another straightforward and reproducible approach is the Silver method, which involves drawing a vertical line from the vermilion border of the lower lip that is perpendicular to the Frankfurt plane. For males, an ideal chin will meet this line at the pogonion, while for females, the chin should be slightly behind this line. Some practitioners use a simple rule that the chin should project as far as the lower lip in men, while in women, the lower lip should project 1 to 2 mm beyond the chin.
See below the Gonzalez-Ulloa line that consists of a vertical line extending down from the nasion perpendicular to the Frankfurt plane. An ideal chin is thought to meet, or fall just short of, this line (From Role of Nonsurgical Chin Augmentation in Full Face Rejuvenation: A Review and Our Experience)
See below the silver method uses a vertical line perpendicular to the Frankfurt line from the vermilion border of the lower lip. An ideal chin will meet, or fall just short of, this line at the pogonion (From Role of Nonsurgical Chin Augmentation in Full Face Rejuvenation: A Review and Our Experience)
In relation to the entire face, vertical chin height should also be taken into account. The top third of the face, which runs from the hairline to the nasion, the middle third, which runs from the nasion to the subnasale, and the bottom third, which runs from the subnasale to the menton, should all be equal in height. Consider the fact that the distance from the subnasale to the stomion superius (inferior margin of the upper lip vermilion) should ideally be one-third of the distance from the subnasale to the menton as an alternate approach of measuring chin height.
Ideal transverse width of the chin is largely dependent on sex and ethnicity. An approximate guideline is that the chin should span the distance between the medial canthi in female patients, whereas it should extend to the oral commissures in males.
Of course, these idealized proportions should only be used as a guideline for analysis as patient preferences, sex, ethnicity, and overall facial anatomy can influence the goal of aesthetic treatment. It has been suggested that chin retrusion up to 4 mm is clinically unnoticeable and likely does not warrant surgical intervention. Mild to moderate retrusion may be more amenable to correction with dermal fillers, whereas more significant retrusion (greater than 10 mm) should be considered for surgical intervention.
When to choose Implants and when to choose fillers for Chin Augmentation?
Alloplastic implants are best for those patients who have adequate vertical chin height but need more projection because implants can only produce significant changes in anterior projection. Surgical genioplasty is a larger procedure that can correct both vertical and anterior deficiencies. Both of these surgical approaches involve extensive dissection and are thus subject to potential complications such as implant rejection or migration, scarring, infection, bone resorption, and mental nerve injury. When compared with injection of dermal fillers, surgical approaches confer higher risk of significant complications and result in a permanent alteration of the chin, which may not look natural or appropriate as aging and mandibular bony resorption continue over the years.
By contrast, injectable fillers offer a nonsurgical, temporary alternative that requires no incisions. Fillers allow for correction of anterior, vertical, and transverse deficiencies, as well as treatment of adjacent structures such as lips, marionettes, and prejowl sulci.
Fillers used for chin injection include autologous fat, hyaluronic acid (HA), and calcium hydroxylapatite (CaHA). The specific choice of filler depends on the patient’s anatomy, injector preference, and cost as there are no data directly comparing these approaches for chin augmentation. In this article, we will discuss the injectable fillers--its techniques and benefits.
1. Autologous Fat Grafting
A research study that examined patients who received autologous fat grafting for their chin concluded that this technique was an effective means of achieving sustained improvement in the anterior projection of the chin, with a maximum increase of 3 to 5 mm. However, when evaluated by both injectors and patients, the ability of fat grafting to improve vertical height was found to be limited. The study involved injecting autologous fat through blunt cannula in multiple layers, both subcutaneously and submuscularly. The injections were initially performed to augment the anterior dimension of the chin, followed by addressing the vertical dimension by locating the menton and moving it downwards using the multilayered technique if necessary. Finally, the authors performed tapered injections on both sides towards the jawline. Patients received up to three rounds of injections. The authors noted that the drawbacks of this method are the variable survival rate of fat grafts and the relatively limited improvement in the vertical dimension of the chin.
2. High-viscosity HA or CaHA
A group of researchers provided a set of guidelines based on consensus regarding the optimal technique for augmenting the chin with high-viscosity HA or CaHA in Asian patients. The recommended procedure involves injecting 1 to 3 mL of the filler in the supraperiosteal and subdermal planes using either a needle or cannula. Needle injections should be administered in a vertical fashion at the gnathion and slightly superolateral to it on both sides. On the other hand, cannula augmentation is performed using a fanning technique with an entry site at the gnathion. The researchers also suggest that while needle injections are more effective in achieving anterior projection of the pogonion and menton, using cannulas may lower the risk of bruising.
In an 18-month, open label study of rejuvenation using an HA filler in subjects with facial volume loss, 15% required chin injection with a mean injection volume of 1.1 6 0.9 mL. At 18 months, 98.3% of all study subjects were satisfied or very satisfied with their results.
The use of high-viscosity HA and CaHA dermal fillers has been found to effectively improve the dimensions of the chin in a study. The authors typically inject no more than 1 to 2 mL of filler per session. If augmentation of the gnathion is required, a needle is used to inject 0.1 to 0.2 mL of high-viscosity HA filler as a depot in the midline, at an angle of 45 degrees to the mental crease, placed supraperiosteally. Smaller supraperiosteal depots are placed lateral to the midline injection on both sides to taper and round out the chin, while respecting the transverse width proportions mentioned above. The pogonion is then assessed, and if anterior projection is required, 0.1 to 0.2 mL of high-viscosity HA filler is injected as a horizontal supraperiosteal depot in the midline through a needle, with one smaller volume injection performed laterally on both sides.
See below a 38 year-old woman with chin retrusion before (left-sided) and after injection (right-sided) of 0.8 mL of HA filler to the chin. HA, hyaluronic acid.
The vertical height of the chin is evaluated in relation to the upper, middle, and lower thirds of the face. If it needs to be enhanced, a high-viscosity HA filler is injected supraperiosteally in the midline using a needle, usually at a volume of 0.025 to 0.1 mL, creating a vertical depot. Additionally, two to three smaller depots are injected supraperiosteally laterally to the midline depot on both sides to taper and round the chin, creating a smooth transition from the gnathion.
To refine the projection of the chin, a blunt-tipped cannula with a size of 22 to 25 G and 1.5 inches is utilized to blend it with the surrounding features. By injecting the filler deep to the Depressor Labii Inferioris (DLI) and Depressor Anguli Oris (DAO) along the mandible, a linear thread of filler is placed to soften the prejowl sulcus. The cannula is then moved to the pogonion to add filler supraperiosteally, making use of a fanning technique and going deep to the DLI and DAO towards the superolateral area to smoothen the transition from the pogonion to the mentolabial and labiomandibular grooves. For retrograde fanning technique, a 28 G, ¾ inch or 25 G, 1-inch needle is sometimes preferred over the cannula. When using needles, HA fillers are the authors' preference because they are reversible if an intra-arterial injection occurs. For the cannula technique, both HA and CaHA fillers are used.
Common Complications
The same risks that come with using injectable fillers on other areas of the face also apply to chin augmentation. These risks include swelling, bruising, delayed nodules, granulomas, and infection. If these complications arise, they should be treated similarly to how they are handled in other areas of the face. Since the skin on the chin is typically thick, contour irregularities that result from subperiosteal injection are often not a significant concern. However, there is a risk of irregularities with superficial injections, especially when the mentalis muscle contracts or during animation.
Vascular compromise is quite rare but has been reported. It has been described after injecting 0.1 mL of PLLA in the right lateral chin characterized by an immediate sensation of warmth extending to the lower lip and central chin numbness. The patient subsequently developed erosions on the mucosal lower lip, but ultimately healed without scarring. The authors suspected mental artery occlusion, but because of the anatomic variability and anastomoses in chin arterial circulation, it is unclear if the insult was to the mental artery, inferior labial artery, or labiomental artery. Suspected ischemic complications of chin filler injection should be addressed with hyaluronidase if appropriate, warm compresses, massage, and possibly topical nitroglycerin, although this remains controversial.
Conclusion
The evolution of neck-lifting techniques has led to improved outcomes, including patient’s self-esteem. This review evidences the use of multiple safe surgeries, during which patients with the right indication have minimal chances of complications. We highlight the importance of hematomas and their prevention during neck-lifting procedures. The hemostatic net has emerged as a safe and reliable technique that could be used to prevent hematomas. Future prospective and retrospective studies should evaluate the patient perception of this technique and the safety of its use.
Reference
Role of Nonsurgical Chin Augmentation in Full FaceRejuvenation: A Review and Our Experience (2020)
Aging of the mandible and its aesthetic implications (2010)
The gender and age-specific differences in the structure of the styloid processes of the temporal bone (2014)
Changes in the facial skeleton with aging: implications and clinical applications in facial rejuvenation (2012)
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