A dental implant is a small titanium screw that has to hold a tooth in place through decades of chewing. That makes it as much an engineering problem as a dental one.
We learned to look at implants that way from our mentor, Dr. Robert Stanley, who is trained as both an engineer and a dentist. One guideline he published shapes how we plan implants here. It’s called the five-thread rule.
Before we place an implant, we want to know that at least five of its threads will be held by your own bone.
What the five-thread rule says
The rule is simple: before an implant goes in, make sure at least five of its threads will be held by the patient’s own bone, what dentists call native bone. Threads that sit in an empty extraction socket, or in graft material that hasn’t become bone yet, don’t count.
The idea comes straight from engineering. When a bolt is tightened into a nut, the threads don’t share the load evenly; the first few do almost all the work. Dr. Stanley’s paper notes that about 93% of the load lands on the first five threads. An implant works the same way: when its first five threads are held by solid bone, it starts out stable.
That starting stability is called primary stability, and it matters because bone needs a still implant to grow onto. An implant that moves while it heals can fail to fuse with the bone.
How we use it
- We count the threads before surgery. A 3D scan lets us place the implant on screen first and check, from every angle, how many threads will meet native bone. That’s how the guideline is meant to be used: with a 3D scan and planning software, not by eye.
- We place it where we planned it. The plan becomes a surgical guide, so the implant goes into the position we checked.
- We measure stability instead of guessing. An instrument reads how firmly the implant is held, so decisions about when it’s ready for a tooth rest on a reading, not a feel.
When five threads aren’t available, which is common right after a tooth comes out because the socket is wider than the implant, the guideline points to a different plan: rebuild the site with a bone graft first, and place the implant once the bone has healed. That’s one reason we talk about the implant at the visit where we diagnose the extraction, not on the day of it. Sometimes the implant can go in the same day the tooth comes out, and sometimes it should wait. The 3D plan tells us which before surgery day.
To be fair to the evidence, the five-thread rule is a planning guideline, not a law of nature. Dr. Stanley’s paper builds it from engineering principles and stress studies and supports it with three patient cases, and it says the rule should be used alongside implant dentistry’s other established guidelines, not on its own. In softer bone, it recommends aiming for more than five threads or letting the bone mature first.
Then it has to heal
The five threads give an implant a stable start. Everything after that is biology: over the next few months, bone has to grow onto the implant, and then hold it while you chew, every day, for decades. Smoking, diabetes, vitamin D, diet and your overall health all play a part. We cover them, and what we do to help, in Are you a good healer?
Why we use BioHorizons
Planning matters more than the logo on the box, and the five-thread rule is a planning rule. But engineers also care about tolerances: how precisely parts fit together. An implant is a system of small parts made to fit each other: the implant in the bone, the abutment that connects it to the tooth, and the screw that holds them together.
We learned from Dr. Stanley why we use BioHorizons, a U.S.-engineered system; the company has manufactured its implants in the United States since it began in 1994. It costs us more than some other systems. We think the peace of mind is worth it.
We also use the system’s own parts, not cheaper “compatible” ones. A 2022 systematic review in the Journal of Prosthodontics found that original abutments gave more predictable results than non-original ones, and concluded that the clinical recommendation should be to use original abutments.
And everyone who gets an implant from us leaves with a card listing its brand, size and reference number, so any dentist, anywhere, can identify it and care for it years from now.
Why shopping implants on price is a loaded topic
An implant is built to carry load: every bite, for years. So the price question is loaded in more ways than one.
It’s fair to compare. An implant is a real investment, and you should know what you’re paying for. But two quotes for “an implant” are often not quotes for the same thing:
- The system. Who made it, what research stands behind it, and whether parts will still be available when you need a screw or a new crown years from now.
- The planning. Whether a 3D scan and a surgical guide are part of it, or the placement is planned on a flat X-ray.
- What’s included. The implant alone, or the abutment and crown too, plus any extraction or grafting the site needs.
- Who’s there afterward. An implant has to work for decades, not just for the week after it’s placed.
Some costs never appear on a quote. An implant placed in the wrong position, or one that fails, usually has to come out, and it takes bone with it. The next attempt starts with less.
For the money side, our guide to why implant quotes vary so much walks through how to compare two quotes line by line.
Questions worth asking any office
- Which implant system will you use, and why that one?
- Will you plan it on a 3D scan, and will you use a surgical guide?
- Will the abutment and screw come from the same system as the implant?
- Will I get a card with my implant’s brand, size and reference number?
- What exactly does the price include?
A good answer to each of these is short and specific. If you’d like to hear ours, ask us at your consultation.
So
An implant is engineering you’ll carry for decades. The five-thread rule helps it start out right, your healing decides how well it settles in, and the system we use makes sure it can be cared for later. The diagnosis makes the treatment plan, and the plan should come before the price.