Mono, Cog and Screw Threads: PDO Thread Types Explained

PDO threads come in three broad designs. Mono threads are smooth and mainly support skin quality; cog threads have tiny barbs that grip tissue so it can be lifted; and screw threads are twisted to add a little more bulk and support. Each is suited to different areas and goals, and many treatment plans use more than one type. The choice affects what you can expect, how recovery feels and which risks matter most.

What all PDO threads have in common

All three types are made from polydioxanone, a dissolvable material long used in surgical stitches. Each thread comes preloaded in a fine needle or blunt cannula, which is passed under the skin and then withdrawn, leaving the thread behind. Over several months, the body breaks the thread down.

As this happens, a mild healing response around the thread is thought to encourage new collagen. That collagen effect is shared by all types, although the evidence comes mostly from small studies and clinical experience. What differs is the thread's shape, which changes how it interacts with tissue. For a general introduction, see PDO thread lift explained.

Mono threads: smooth and fine

Structure: a single smooth strand with no barbs, usually very fine.

Purpose: mono threads are not designed to lift. They are placed in larger numbers, often in a grid or mesh pattern, to support skin texture and firmness through the collagen response.

Typical areas: crepey neck skin, fine lines in the lower face, the area under the jaw, and sometimes around the mouth or forehead. They may also be used on the body in some practices, though evidence there is more limited.

What to expect: changes, if they come, are gradual and subtle, developing over two to three months. Recovery is usually lighter than with barbed threads, with mild swelling and bruising along the paths.

Screw threads: twisted for extra support

Structure: one or two strands wound around the needle in a spiral, giving more material in a small space.

Purpose: the twisted shape adds a little more structure than a smooth thread. They are used to support areas with slight hollowing or deeper lines, rather than to lift.

Typical areas: along deeper folds, the cheeks or areas where skin needs firmer support. They may be combined with mono threads in a mesh or placed under a crease.

What to expect: a firmer feel under the skin for a few weeks and a slightly stronger collagen response than mono threads alone. They cannot replace the volume that filler provides.

Cog threads: barbed for lifting

Structure: thicker threads with tiny barbs or cones along their length. Designs vary: some have barbs in one direction, some in two directions, and some are moulded rather than cut. These details affect how firmly they hold.

Purpose: the barbs grip the soft tissue under the skin. Once placed, the injector can ease the tissue upward along the thread, creating a modest lift. This is the type most people mean by a "thread lift."

Typical areas: the jawline and jowls, the cheeks, the outer brow and sometimes the neck. Our articles on threads for the brows and midface and on early jowls cover these areas in more detail.

What to expect: an initial lift that softens over the first few weeks as swelling settles, followed by gradual collagen changes. Recovery is more noticeable than with smooth threads, with more swelling, tightness and a higher chance of dimpling.

Comparing the three at a glance

• Lift: cog threads provide some; mono and screw threads provide little or none.
• Skin quality: all three may contribute through collagen, with mono and screw threads used mainly for this purpose.
• Number used: mono threads are typically used in larger numbers; cog threads in smaller numbers per side.
• Recovery: generally lightest with mono threads and most noticeable with cog threads.
• Risk profile: barbed threads carry a higher chance of dimpling, pulling sensations and asymmetry; any thread can become visible, extrude or become infected.

Why thread choice matters

Using a lifting thread where no lift is needed adds risk without benefit. Using smooth threads when someone hopes for lift leads to disappointment. Thread length, thickness and barb design also need to match the area and skin thickness: a robust cog thread under very thin skin is more likely to show, while a fine mono thread in heavy tissue may make no visible difference.

This is why the decision is made after examining your face, often by gently lifting the tissue to see how it responds, and discussing your goals. Many plans combine cog threads for support with mono threads for texture. It is reasonable to ask how many threads are planned, of which type, and what each is meant to achieve.

Who should not have threads, or should wait

Regardless of type, threads are usually avoided or postponed during pregnancy or breastfeeding, with an active infection or cold sore in the area, with a keloid tendency, with an autoimmune condition, bleeding disorder or poorly controlled diabetes not yet reviewed, and with permanent fillers or implants nearby. Very heavy tissue or significant loose skin is often better addressed in other ways. Share all medicines and supplements, and do not stop a prescribed medicine without speaking to the doctor who prescribed it.

Frequently asked questions

Do barbed threads last longer than smooth ones?

Thicker threads may take longer to dissolve, but how long a result lasts depends more on your tissue, the area and lifestyle factors than on thread type alone.

Are there threads made of other materials?

Yes. Some threads use other dissolvable materials that break down at different rates. Ask what is being used and why.

Can I choose which type I get?

Your preferences matter, but the type should fit your anatomy and goals. Your physician should explain the reasoning behind any recommendation.

Understanding your plan

Knowing which thread is being used, and why, helps set realistic expectations. If you are curious whether threads of any type could help, a consultation with HealthPark Medical Aesthetics can explain the options and whether another approach might suit you better.