Following another weekend at the Misch Institute, I noticed Dr. Misch is becoming increasingly concerned with the chain dental clinics' marketing of the all-on-4 dental implant system as a one size fits all procedure for everyone. Misch's comments in an interview with Glidewell Laboratory, illustrates his fear:
"We know that the majority of complications in implant dentistry are based on biomechanics, whether it’s bone loss, abutment screw loosening, prosthesis fracture, or restorations becoming uncemented. If you list all the complications that you see in an implant practice, from once the implant heals to after it’s loaded with the prosthesis and the next five to 10 years, the majority of the complications are related to biomechanics. Wound healing is very predictable for the body. We’ve had teeth for seven million years and the body has learned how to heal a socket. I’ll tell the residents, “If the patient doesn’t die in the next three to four months, they’ll heal!” The patient is going to die or heal. And they heal! So wound healing for the body, the biologic science of wound healing, is a surgical application of what we do. But once the body heals, the thing that maintains what’s going on is more related to biomechanics.
In its simplest form, one of the easiest things for dentists to understand is that stress equals force divided by area. The higher the force, the higher the stress. The greater the area, the lower the stress. Your intuition knows that. No one puts one implant in and puts 14 teeth on one implant. That’s not enough! Why? Because there would be too much force and too much stress and the implant would fail. So as soon as the guy puts in a second implant, he has already proven to me that he understands biomechanics. If bacteria and hygiene were the only things you had to worry about, you’d just put one implant right in front. But as soon as you put a second one in, you know biomechanics is important. Now, we can discuss how important you think it is and what our studies show. So because stress equals force divided by area, four implants instead of six would have higher stress. All-on-4 really means “None-on-3.”
I’m not saying that it always fails. If it always failed, you’d be pretty stupid to do it. The fact is that it works sometimes. So where does it work? Where bone is good and the forces are less. Where are the forces less? An upper denture against natural teeth, female patient, preferably old.... So I go through my five patient factors that affect how much force there is. Then you get into the area part of the equation. How do you affect the area? The number of implants is the greatest way to affect area. What are the secondary ways? Well, the diameter of the implant. Quantity is more important than diameter, but it’s part of the equation. Then it’s the length of the implant. Well, it’s part of area, but it’s not as important as diameter. So there’s an order of importance relative to it. Part of it is, what is the strength of the bone?"