Selecting a filler is not a single decision but a layered one: anatomical zone, tissue depth, desired mechanical property, and patient-specific risk factors all interact. This module frames selection around anatomical zones rather than brand comparison, since the same underlying rheological principles from Module 4 apply regardless of manufacturer.
Tear troughs and periorbital region
This is one of the highest-risk zones for both vascular complications and the Tyndall effect (a bluish discolouration from superficially placed HA scattering light). The tissue here is thin, mobile, and vascularly dense (proximity to the angular artery). Teaching emphasis should be on low-G′, low-viscosity, highly hydrophilic products placed deep, pre-periosteal or supraperiosteal, with conservative volumes and a strong bias toward products with well-documented rapid hyaluronidase reversibility.
Cheeks and midface
The midface tolerates — and often requires — higher G′ products for structural lift, since the goal is frequently to restore bony and fat-pad support that has receded with age. Deep, bolus, supraperiosteal technique is common here, contrasted with the more superficial, fanning techniques used in areas requiring blending rather than lift.
Lips
Lip tissue is thin, highly mobile, and cosmetically unforgiving of asymmetry or lumping — students should be taught to favour lower-viscosity, higher-cohesivity, softer gels here, generally placed submucosally or within the vermillion, with technique (linear threading, micro-boluses) mattering as much as product choice given how visible any irregularity becomes on movement.
Jawline and chin
These are load-bearing, structural zones tolerant of firmer, higher-G′ products, often placed supraperiosteally to redefine bony contour. This is also where CaHA is frequently favoured over HA, given the combination of firmness, durability, and biostimulatory collagen deposition discussed in Module 3.
Nasolabial folds and marionette lines
These dynamic folds require a filler that balances correction with the tissue's natural movement — overly rigid, high-G′ products in this zone risk an unnatural, immobile appearance during facial expression, so a moderate G′ with good cohesivity is typically favoured, injected along the fold at a mid-to-deep dermal plane.
A general teaching principle
Encourage students to reason from tissue biomechanics and rheology outward to product choice, rather than memorising a fixed brand-to-zone lookup table. Manufacturers periodically reformulate, rebrand, and introduce new crosslinking technologies; the underlying anatomical and rheological logic is what remains transferable across a career.