Internal or external thread? Or skip the thread.

This whole drama is far greater than the strength of the evidence that supports it and one of those slippery slopes where marketing has gotten way ahead of reality.

There are many simplifications in the piercing community that are then passed around the internet like sacred dogma. Unfortunately, a significant portion of what is considered "fact" in the industry is actually expert recommendation based on engineering and experience, not solid clinical evidence.

"The external thread is the devil incarnate and tears the piercing canal"!

A significant portion of the industry is downright paranoid about demonizing external threads. Why? Perhaps it has something to do with prehistory, as a mere two decades ago, most civilian piercing jewelry was made of inferior steel, with sharp thread edges, and generally lacking in attention to detail. During insertion, the threads were indeed quite clumsy and could act like a file. The problem, however, wasn't the thread itself, but the quality of its workmanship.

What is it really like?

A well-made external thread, with a rounded starting point, polished, and installed with a taper or transfer pin, causes virtually NO visible or even perceptible damage! It is therefore untrue to say that using external threads in practice is a red flag, as there are NO scientific studies to support such an assumption. Just as there are NO studies demonstrating the superiority of internal threads over external threads. THEY DO NOT EXIST.

INTERNAL THREAD

It's currently the gold standard in the industry. But is it the best? Indeed, it is. A smooth rod passes through the channel, without any threads or grooves, as everything is "inside." That's true. But that doesn't automatically mean higher quality. Sure, you can buy an internally threaded earring, but it might be poorly made, poorly matched to other components, made of low-quality titanium, and poorly machined. And what then? So, the thread type alone doesn't define anything—and here we return to production technology.

PIN / THREADLESS

Probably the most promoted system in recent years. Promoted because it doesn't defend itself very well. Threadless jewelry uses no threads at all. Instead, a press-fit method is used—a thin wire with a ball is inserted into the free space of the rod. But! Exactly. The pin wears out. It wears out quickly. Each manipulation straightens it slightly, reduces tension, and after a few replacements, it's much less durable. It's very easy to lose the pin in such a case. And since they can be really expensive... the loss hurts ten times more.

But it could be worse. We all get infections and other nasty little mishaps. In such a case, the real surgical procedure is to try to remove the pin without jerking it and causing more damage.

Generally, threadless piercings aren't perfectly standardized. A pin from one brand might be too loose, too difficult, or not fit at all into another brand's labret. Furthermore... durability. A well-made external thread can withstand hundreds of insertions and removals. Internal threads, too. And a thin, delicate pin-type wire? Oh well.

This is undoubtedly a convenient solution for customers, but is it suitable for their wallets?

It's a terrible mistake and a sign of utter ignorance to judge jewelry solely by its thread type. In everyday practice, material quality, precision machining, surface polishing, and manufacturing tolerances have a much greater impact on safety and comfort than the mere fact that an earring has threads and what type.

So it seems that in piercers' minds, threads are some kind of sharp, dysmorphic screw. But not all threads look the same! In our industry, there's no distinction between, say, sharp CNC threads, rounded threads, or polished threads; no consideration is given to their length or angle. All of these are conveniently lumped together.

And do you know the difference between a marketing slogan and an assessment based on mechanics and workmanship? The statement "external threading always damages a piercing" is too categorical. A more precise one would be: a poorly made external thread can increase the risk of injury during insertion, while high-quality externally threaded jewelry, when used properly, does not necessarily cause significant damage to the piercing canal.

The behavior of jewelry during replacement is determined by the entire design of the tip—its geometry, surface finish, tolerances, and replacement technique—not just the thread type. Much also depends on the anatomy, age, location of the piercing, and the jewelry model. There are no studies showing that external threading alone causes more complications.

And what is it like in practice?

A well-made external thread gradually increases in diameter, first entering a thin point, then the subsequent threads, and finally the full diameter of the rod. This is similar to the action of a short expanding cone.

Internally threaded jewelry, on the other hand, has a practically flat tip. The channel immediately receives the full-diameter element, sometimes with a rather sharp transition between the tip and the barrel. Therefore, if you don't use a taper or transfer pin, you may actually experience greater resistance when passing through the channel.

What does biomechanics say about this?

In this case, we're dealing with two mechanical types of loading: friction (when something slides across the tissue) and expansion (when the diameter increases rapidly). An external thread may generate more friction on the grooves, but a blunt barrel may require more force to expand the channel. These are two different mechanisms, and it's impossible to predict in advance that one is always worse than the other.

Friction increases tissue damage—a fact well documented in the field of biomechanics. The greater the roughness, coefficient of friction, and sharp edges, the more micro-damage occurs. This principle applies not only to piercings but also to any manipulation of soft tissue.

The geometry of the tip influences the force required for penetration. This has also been proven. The shape of the tip changes the stress distribution, the force required to separate tissues, and the way biological material is deformed. Conical tips require a different force distribution than blunt cylindrical tips.

From a mechanical engineering perspective, there are also other parameters that should be included in this discussion, such as:

• tip rounding radius,

• approach angle,

• the force needed to expand the channel,

• contact surface during the first millimeters of insertion.

Does this thread really matter THAT much?

Probably... not as much as the industry suggests.

How much of this thread actually touches the tissue? Consider a classic labret (flatback) with a thickness of 1.2 mm. The thread is typically about 2-3 mm long, with 3-5 threads, and a height of each thread is about 0.1 mm. This means that only a very small surface area contacts the tissue. If the thread is well polished, the contact is spot-like and lasts literally a fraction of a second during insertion.

Now compare this to: sliding the entire rod through the canal, removing and replacing the ball or cap, manipulation with tweezers, scissors or forceps, and pressure when gripping the jewelry - these are the very things that often generate much greater forces than the thread itself.

Moreover, there's a scale factor here. The piercing channel is approximately 1.2 mm in diameter. The tissue, however, is flexible, hydrated, and capable of deformation. The difference between a smooth cylinder and a well-made thread is often tenths of a millimeter. Does it matter? Yes. Or is it significant? No one has demonstrated this.

What damages the canal the most?

Taking biomechanics and clinical practice into account, if one could rank the factors according to their likely effect on tissue, it would look something like this:

1) Replacement in a fresh piercing,

2) Struggling and repeatedly trying to hit the channel,

3) Dry tissue without adequate slippage,

4) Poorly polished jewelry,

5) Sharp edges,

6) Incorrect jewelry size,

7) Thread type .

Does the client_ feel it?

If the external thread were truly disrupting the canal to such a significant degree, one would expect, for example, increased pain with each replacement, more frequent bleeding, more granulation and scarring, and longer healing times. At the same time, surprise, surprise, there is no research on this topic.

In light of this information, it's hard not to get the impression that the industry has significantly overestimated the importance of thread type. In fact, it's a very simple parameter to communicate. It's easier to say, "We use internal threads" than "We use jewelry with the right metal alloy, low surface roughness, precise tolerances, proper tip geometry, and we choose the right replacement technique for the situation."

The latter is much closer to what actually influences the healing process, but is much more difficult to convey to the Client_.

Why does APP (Association of Professional Piercers) promote internal threading?

This stems primarily from the assumption of safety for the entire market. If an organization is creating standards for thousands of studios and even more piercers, it must also consider the cheapest and lowest-quality jewelry. Historically, external threads have been poorly made, so the safest approach was to adopt the "avoid them" narrative. This, of course, was a very reasonable population recommendation, but it doesn't automatically mean that every external thread is inferior to every internal thread.

There is currently no clinical evidence to support the idea that thread type (external, internal, or threadless) alone affects piercing healing. Available recommendations are based primarily on biomechanics, materials science, and expert experience. The quality of the jewelry's craftsmanship, surface finish, tip geometry, replacement technique, and piercer's skill likely play a greater role than the thread type itself.

APP doesn't cite clinical studies because they simply don't exist. These are American standards, valuable and important as they may be, but they are developed by experts based on experience and extensive knowledge from various fields, not scientific research. The official narrative is: "external damages the canal," but there's a lack of meaningful clinical evidence on this matter, such as histological images, microscopy, SEM, OCT, or other studies. Therefore, APP promotes a conceptual framework, but not a scientific one.

Interestingly, virtually all articles condemning external threads cite each other or APP/AUPP standards, not clinical studies. This doesn't mean they're wrong, of course, but it does show that the level of evidence is different than one might think. A solid 90% of the texts and graphics circulating online follow the same pattern: external threads destroy tissue, internal threads are great, and threadless is even better. And that's it.

But no one shows... how it massacres. There are no mechanical models, cross-sections, geometric analyses, contact surface comparisons, pressure distributions, etc. Just one sentence, repeated practically word for word on subsequent pages: "Threads tear tissue."

The professional market has almost entirely transitioned to internal threads and threadless. As top manufacturers embraced this approach, quality standards began to be identified with specific design solutions.

It's therefore important to be able to separate what we know from research from what results from expert consensus. In the case of threads, this consensus exists, but it is not supported by strong comparative research.

Do you have a different opinion?

Do you think you just read the most unrelated sci-fi of your life? Or perhaps you had a completely different experience? Do you think something needs to be added? Is something missing, or do you have a better idea?

Write!

I love constructive discussion and Open Minds! Maybe together we can achieve something even better?

Paula Peszka, Paoli

F-Skin 2.0 EduLITE Academy

contact: paula.lapeszka@gmail.com

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