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For novice beauticians, injection methods can be confusing as they are not as straightforward as multiple-choice questions. The method used depends on various factors, including the type of filler used, the patient’s age, gender, and skin condition.
The most commonly used fillers on the market currently include autologous fat, hyaluronic acid (HA), calcium hydroxyapatite (CaHA), poly-L-lactic acid (PLLA) and polymethyl methacrylate (PMMA). These components differ in terms of their duration of effect, bioactivity, filling properties and water absorption.
In addition, carefully assessing the patient’s condition, particularly their skin, is crucial for achieving the best possible treatment results. When assessing the face, it is helpful to divide it into three sections:
1) the upper face, from the hairline to the outer canthus level;
2) the midface, from the outer canthus level to the upper lip;
3) the lower face, from the upper lip to the upper neckline (see Figure 1).
Figure 1: Injection diagram for the three facial zones.
Upper face: Forehead contour, temporal hollow and brow bone shape.
Mid-face: lateral and medial cheek area, under-eye area, and nose shaping.
Lower face: jawline, lips, chin, marionette lines and hollows in the cheeks.
Secondly, three filling schemes can be adopted when carrying out injection moulding, depending on the filler used and the injection area: 1:1 filling, overfilling and underfilling.
Our goal when using fillers is to achieve the desired corrective effect. However, slight overcorrection is sometimes necessary, particularly with certain areas (such as the lips) and fillers (such as autologous fat). Undercorrection is most commonly used with Sculptra and Bellafill, since multiple injections are needed to allow the effects of the product to build up gradually.
Finally, we come to the main focus of this article: the most commonly used injection techniques. There are six such techniques, and each injector has their own preference. Taking into account the anatomical structure of the injection site and the injection depth, a technique is selected for each injection. The main techniques include dot, linear, cross-linear, fan-shaped, and cluster injection (see Figures 2–6).
While most injectors prefer percutaneous techniques, some intraoral techniques are also suitable for filling the lower face. One recently reported technique is the ‘pyramid’ injection technique, which involves inserting a sharp or blunt needle vertically (at a 90° angle to the base of the injection site) and gradually administering the drug as the needle is withdrawn (see Figure 7). Depending on the treatment goal, pyramid-shaped stacking rather than layered injection may be chosen. Injection depth also varies; most injections for deep volume replenishment are administered at the periosteum, whereas superficial injections are administered into the dermis or subcutaneous layer. Injections that are too superficial, especially in areas with thin skin, may lead to adverse reactions. Key visual indicators that the needle is in the correct plane include: The grey colour of the needle is not visible; the shape of the needle is not obvious; and the injector can press down on the fat when pressing the needle tip downwards.
Figure 2: Dot injection. Insert the needle into the skin at a 10° angle, following the direction of the wrinkles. Connect the injection points closely together to create a smooth, even finish. Gently massage the injection site with your fingers or a cotton bud.
Figure 3: Linear injection. Insert the needle fully into the skin at an angle of approximately 30° to the length of the wrinkle or fold. Administer the medication while withdrawing the needle in a linear fashion. Gently massage the injection site with your finger or a cotton bud. The dot-to-line injection technique combines dot-to-dot and linear injection techniques.
Figure 4: Fan-shaped injection. After a linear injection is performed along a line, the needle is withdrawn in order to change direction. Another linear injection is then performed and this process is repeated.
Figure 5: Bulk injection. Insert the needle into the periosteum, withdraw it slightly, then inject a large amount of filler.
Figure 6: Cross-linear injection. A linear injection technique is used at the edge of the depression. The needle is then withdrawn from the skin and reinserted 5–10 mm away from the initial injection site. This process is repeated. This process is then repeated along a line perpendicular to the initial injection line.
Figure 7: Tower-shaped injection
a. Schematic diagram of skin wrinkles.
b. Drug delivery via retrograde needle withdrawal from the upper periosteum using the vertical injection technique. A very small amount of filler is administered as the needle is withdrawn.
In conclusion, novice beauticians should not feel anxious or impatient when confronted with the many options and techniques available for filler injections. Every experienced practitioner had to start somewhere. True skill development comes from consistently practising the principles of ‘safety, effectiveness and reversibility’. Successful filler injections require a combination of factors, including an in-depth knowledge of the properties of different fillers, a thorough clinical assessment of each patient’s individual needs and the application of techniques that cannot be used in other areas. We customise a plan for each patient rather than applying a one-size-fits-all approach.
