Same PCL, Different Results: Thread vs. Filler — How to Choose

PCL (polycaprolactone) is used as both a thread and an injectable filler, but their roles differ. The thread physically lifts tissue by catching it with barbs, while the injectable filler stimulates collagen production through microparticles to add volume and firmness.[1][2]. Whether your concern is Sagging (skin laxity) or volume loss determines which option is right for you.[1].

What do threads and fillers do inside the body?

Threads "support," and fillers "build" — those are their main functions. Thread lift is understood to differ from fillers and lasers that work on volume and skin quality, in that it can physically lift sagging (skin laxity) tissue.[1]Smooth threads without barbs aim only at skin activation, while barbed threads catch tissue and change its position — expert consensus documents also distinguish between these.[3].

PCL in injectable form is made by mixing fine particles with a carrier and does not have a grasping structure. Injectable stimulating agents such as PLLA, PCL, and calcium hydroxyapatite share a common mechanism of enhancing collagen production and improving dermal quality, according to the review.[2]In rat experiments, PCL particles injected over the periosteum induced greater production of collagen and elastin compared to hyaluronic acid, and recruited blood vessels and stem cells, according to reports.[4].

Which has longer-lasting results?

The injectable form has reports of longer duration. PCL injectables can take 2–3 years to degrade, during which volume and wrinkle correction may continue, as research comparing PLLA and PCL in nasolabial folds explains.[5]The same study reported that at 12-month follow-up, PCL showed greater improvement in wrinkle severity compared to PLLA.[5]Liquid-type PCL is shorter at around 12 months, and pilot studies of the mid-face note that duration varies from 1–4 years depending on the formulation.[6].

With threads, the period during which the material remains in the body does not align with the duration of effect. In a compilation of 111,948 cases, the duration of Thread lift effects is approximately 6–12 months depending on material and location, with PCL threads noted to persist for around 12 months.[7].

If it's "sagging," Thread lift; if it's "volume loss," Filler injection?

Broadly speaking, that's how you can think about it. Thread lift has the property of lifting immediately after insertion, and a real-world clinical study of PLCL (a copolymer of PCL and lactic acid) barbed sutures in Indian patients reported approximately 96% improvement immediately after the procedure, and approximately 71% showed further improvement with follow-up observation.[8].

If the main concern is hollowness or loss of elasticity, a catching structure is not necessary. A pilot study of 30 patients who received liquid PCL injected into the midface twice reported improved skin quality and volume and high satisfaction over 6 months, with adverse events being mild and temporary.[6].

How do complications differ?

Thread lift has its own complications, and filler injection has its own. A meta-analysis summarizing complications of facial Thread lift organizes them into 5 types: short-term symptoms such as bruising and swelling; skin depression and contour irregularities; sensory changes such as numbness; infection and thread exposure; and damage to surrounding nerves or the parotid gland.[9].

With fillers, careful injection technique is recommended because particle distribution and injection technique affect outcomes and complications.[6]Whichever you choose, it's reassuring to ask in advance about the types of complications that can occur and how they are managed if they do.

Is there a difference in the thickness of data?

Yes. The filler PCL has a clinical study compared with PLLA over 12 months.[5]PCL thread comparisons are mainly limited to experiments in rats and mice.[10]Human reports center on real-world clinical studies without a comparison subject.[8]Even looking at dissolvable threads overall, systematic reviews conclude that there are no studies demonstrating long-term efficacy.[11].

Distinguishing at the consultation

First, stand in front of a mirror, point to the area of concern, and discuss with your doctor whether it is "sagging in position" or "loss of volume." Even with the same PCL name, the answer changes there.

Often both are mixed, and whether to address one first or combine them on the same day will be decided after confirming the degree of sagging and skin thickness at the consultation.