Introduction

The lower third of the face cannot be ignored as part of the facial ageing process. The following factors play a decisive role:

1. Sagging of the skin and connective tissue in the cheek area and perioral region.
2. Malar fat tissue reduction.
3. The resorption of bone in the upper and lower jaw.
4. The position of the teeth, possible tooth loss, dentures.

As a result of these processes, there is a successive reduction in the definition of the mandibular line (jowls) and surface irregularities of the chin region such as dimpled chin and chin ptosis, perioral radial wrinkles and emphasis of the mandibular crease. In this review, we focus on the chin and mandibular line. With regard to dynamic perioral wrinkles, please refer to the reviews [1-3].

Material and methods

A literature search of the years 2010-2024 was conducted via PUBMED. Inclusion criteria were:

1. Studies in English or German;
2. Information on fillers and injection techniques;
3. Performed on healthy adults;
4. Data access.

Exclusion criteria were:

Studies on fillers in other indications and outside the lower third of the face.

The search was carried out using the following keywords: “Filler”, “Face”, “Aging”, “Esthetics”, “Jawline”, “Chin”, “Marionette Lines” and “Trial”. “Filler AND Trial” yielded 1008 studies, “Filler AND Face AND Trial” yielded 362 hits. “Filler AND Face AND Trial AND Esthetics” yielded 215 studies, “Filler AND Jawline” yielded 71 studies and “Filler AND Chin” yielded 123 studies. “Filler trial AND Chin” yielded 12 studies, “Filler trail AND Marionette lines” 11 and “Filler trial AND Jawline” 6 publications.

Anatomy and aging

Jowls (“sagging cheeks”): There are various hypotheses regarding their origin. Mendelson et al. described the jowls as changes in the sub-platysmal, deep tissue layer [4]. In contrast, Reece & Rohrich assumed a supra-platysmal location [5]. More recent studies by Minelli et al. (2023) were able to confirm that the jowls are supra-platysmal [6].

The area in which the jowls develop are zones of maximum sliding of the subcutaneous tissue layers over the musculature during mandibular movements. The retinacula cutis, which connect the skin to the muscles above the mandibular ligaments, are significantly longer than in other supra-platysmal areas. With increasing age, the connective tissue fibers lose elasticity and become longer.

The age-related changes take place in several stages:

1. In patients with thin skin and minimal jowl formation, there is atrophy of the subcutaneous fatty tissue.
2. Cheek ptosis with normal skin, loss of the submalar depression and tissue fullness in the midface is caused by caudal displacement of fatty tissue compartments.
3. Cascading, confluent fatty tissue over the mandible is caused by septal dehiscence.

There are 3 retaining ligaments on the chin according to Kang et al. (2016) (Fig. 1). They are located in the sub-platysmal layer:

Fig. 1: Mandibular anatomy. Bony structures and attachments of the ligaments (L.) modified after Kang et al. (2016). ( Partyna, modified by Apatanis Zandikaulis, Wikimedia Commons).

1. The mental ligament lies ca. 9 mm lateral to the midline and 8.4 mm above the lower edge of the mandible.
2. The medial mandibular ligament, which is located almost 29 mm lateral to the midline and slightly more than 8 mm superior to the lower edge of the mandible.
3. The mandibular osteocutaneous ligament, more than 50 mm lateral to the midline and approximately 9 mm above the lower edge of the mandible [7].

According to recent anatomical studies, the mandibular ligament lies posterior to the jowl formation. The maximum caudal extension of the jowls is positioned over the posterior border of the medial mandibular ligament. The ligaments are not directly involved in the anterior and posterior borders of the jowls [6].

Mandibular fold: The labiomental or mandibular fold (“marionette line”) is formed by direct insertion of fibers of the orbicularis oris muscle and the “tectonic” transition zone of the SMAS (superficial musculoaponeurotic system) from type I (cheek) to type II (lips).

SMAS type I consists of parallel fibrous septa that connect the mimic musculature with the skin, while type II has stronger fasciae and smaller fatty tissue components [8]. The genesis of the mandibular fold is thus analogous to the nasolabial fold [6].

The mental fold is located between the lower lip and the prominence of the chin. It is created by contraction of the mentalis muscle [9].

The chin derives its shape from the bony structures, especially the symphysis, and the overlying soft tissue. Three-dimensional tomography and cadaver dissections indicate a significantly stronger vascularization of the superficial soft tissues than the deep parts [10]. This is important for esthetic filler injections.

Chin ptosis is caused by displacement of soft tissue from the symphysis of the mandible over the caudal edge of the mandible [11]. It can be dynamic, i.e. caused by muscular activity. These patients have a horizontal smile.

In “illusory chin ptosis”, the lip position and the intraoral sulcus are normal, as are the mimic movements. This type is caused by a pronounced submental crease, which can also sometimes exceed the lower edge of the mandible towards the head. Smiling does not change the perceived “ptosis”. In addition, there are variants that occur due to morphogenetic disorders or postoperatively. These changes are primarily corrected surgically and will therefore not be considered further here [12].

Dimpled chin is caused by contractions of the mentalis muscle and occurs as a dynamic phenomenon, particularly during speech [13]. Because of this mimic component, treatment with botulinum toxin is a priority [2].

Subcutaneous fatty tissue: Subcutaneous fatty tissue is involved in the development of the jowls and the mandibular fold. This is not present as a uniform layer but is structured in various compartments with stratification into deep and superficial parts.

Regarding the jowls, the lateral-temporal cheek compartment, the middle cheek compartment, the labiomandibular compartment and the jowl compartment under the middle cheek compartment are of interest. The labiomandibular compartment plays the dominant role in mandibular folds. For the dimpled chin, the chin compartment is of interest [14]. The structural and pathophysiological changes of the subcutaneous adipose tissue are of great relevance for the aging process of the face [15].

Filler for aesthetic application in the lower third of the face

In the following, we provide an overview of the published studies on filler treatment of the jowls, chin and mental folds, which are of outstanding importance for the aesthetics of the lower third of the face. For labiomental wrinkle treatment and correction of the dimpled chin, please refer to these publications [1, 16, 17].

For a safe injection technique, it is essential to consider the vascular anatomy of this region. The submental artery and the facial artery as well as the accompanying veins are the main vessels in this region. The submental artery originates from the facial artery. It can anastomose with the mental artery, which arises from a branch of the maxillary artery. The submental artery can communicate with the inferior labial artery [18].

Fig. 2: Aesthetic filler treatment of the prejowl region with HA filler in a 65-year-old woman. Creation of the V-aspect in the frontal view by deep injection along the mandible anteriorly and correction of the mandibular fold with retrograde filler application. Above untreated, below immediately after injection.

Posterior to the junction of the facial artery and vein from the neck over the mandible, the subcutaneous and supraperiosteal loge should be preferred for filler injections.

When selecting fillers, it is important to bear in mind that skin tightening effects are based on different effects. While hyaluronic acid (HA) fillers achieve a tightening effect primarily through volume, bioactive fillers such as poly-L-lactic acid and calcium hydroxyapatite (CaHA) are capable to change the connective tissue structure. However, this requires a comparatively longer time than the increase in volume using HA. The use of permanent fillers is not recommended, as severe side effects have been observed, sometimes with a delay of years. These usually result in surgical procedures to remove the filler material [19-23]. In the chin area, fillers with a high G* (gel strength or deformation resistance) and low Tan δ (phase angle, a relative measure of the viscous and elastic filler qualities) are recommended. Tan δ is the quotient of G” (viscous modulus) and G’ (elastic modulus).

The rheological properties of CaHA can be adjusted by appropriate dilutions. Higher dilutions reduce the gel strength (G* and G”) and increase Tan δ and thus the viscosity [24].

Filler studies for contouring the lower jawline

Table 1 provides information on study results after filler injection subcutaneously or supraperiosteally [25-34], both sharp and blunt needles were used. The injected volumes were between 1.2 and 4 ml. Most authors prefer a retrograde injection technique, some use the fanning or multilayered technique.

Some of the authors treated only young patients, in whom aging processes in the lower third of the face are likely to be present only slightly, if at all [32].

Only one study focused on patients >50 years of age [33]. This highlights a general problem of studies in aesthetic medicine – the focus on youth and the exclusion of advanced age.

If the sagging cheeks are less pronounced, filler injections in the midface can also help to improve the lower jawline and should be performed first [35, 36].

Table 2 provides an overview of the fillers used.

Filler for contouring the chin and treating mental wrinkles

The injection point for the prejowl region is lateral to the paramedian retraction at the edge of the mandible. The filler is injected retrogradely submuscularly and/or subcutaneously (Fig. 2). The mental fold is often also treated by injecting hyaluronic acid fillers, which are injected subcutaneously [37].

The 3-point chin technique for shaping the chin goes back to Adel. All injection points are located along the midline. The first injection point is at the mental crease. The second injection point is at the pogonion (the most anterior part of the chin) and the third injection point is at the menton (the inferior point of the chin). In a first step, a microbulus of hyaluronic acid filler is placed at these 3 points, followed by superficial retrograde linear injections [38].

Table 3 provides an overview of the filler studies [38-40].

Filler for the treatment of marionette lines (mandibular fold)

In terms of the complex treatment of the lower third of the face, the mandibular folds should not be neglected. Hyaluronic acid fillers are predominantly used here, although case reports and retrospective studies for CaHA are also available [32, 41-45]. Linear retrograde injection was predominantly used, with microdroplet or fanning techniques employed less frequently. The filler volume used was mostly 1 ml.

Safety aspects

In a systematic review, Ou et al. (2024) evaluated 917 patients with chin treatment. The most common side effects were at the injection site: swelling, bruising, pain, redness, pruritus. Only 2 more serious hub effects were observed, but no vascular complications (46). Other authors have observed tongue necrosis as a rare and serious complication [47].

Summary

Filler injections have been established as non-surgical versatile tools to correct age-related changes in the aesthetics of the lower third of the face. Biostimulatory fillers such as CaHA are used for the jawline while hyaluronic acid fillers are preferred for the chin. However, permanent fillers should not be used due to safety concerns [22, 23]. There are some possible combinations with microfocused ultrasound, injection lipolysis and neuromodulators, which allow an individualized treatment [48]. There are also other treatment options such as lipotransfer and surgical techniques [49, 50].

The advantage of minimally invasive correction with fillers are the short downtime for the patient and the manageable costs. The disadvantage is the limited duration of the effect. However, surgical measures cannot be replaced by fillers in cases of pronounced cheek ptosis and chin deformities.