All-on-4 Technique: Where is the Location of the Fulcrum Point on the Posterior Tilted Implants?

What a great question. In a case like that there is a decomposition of the forces applied to the implant/abutment that generate lateral torque following a simple rule called the Right hand rule. The fulcrum will change depending on the oclussion. If the compression point is in the anterior area (24/25) you will have compression in the mesial implants and and traction in the posterior ones and that will move the fulcrum of the superstructure to the mesial and generate torque to the left in the anterior implants and posteriors , on the other hand if the occlusion is in the last molar (one side) you will move the fulcrum of the structure to the distal compressing the distal implant and tractioning the mesial one and generating torque to the right on the ipsilateral mesial and distal implants and to the front on the contralateral implants. If the occlussion is between the two ipsilateral implants it will compress both implants and make traction in the cotralateral implants thus generating a mesial or to the front torque in the contralateral and ipsilateral implants. This is only the start because there is also decomposition of the force vectors in every implant in every diferent location of the occlussion point, but you catch the idea. I hope this helped Alex

Since the prothesis is splinted...and not single units...is there really a"fulcrum point" ? or are the forces of occlusion distributed over the entire prothesis?

Hi, Don. Yes implants are splinted but since bone has a small flex and every implant system has some degree of flex or movement, you do have fulcrum points that change with every point of contact during the occlusion. It would be very nice to believe that there is no movement or flex but there is and to tell you the truth, there is a lot and with some very famous systems thre is really a lot. Since there is compression and traction you will get fulcrum points and applyed torque situations. Cheers

Dr. Berg, that is exactly why " all on four" is a poor design! I don't know if you have noticed, but the acedemic lecture circuit, has almost collectively, "turned their backs" on this technique and rightfully so, in my opinion. Bv

I couldnt agree more, did it twice about 10/12 years ago and learned the lesson, i much rather graft so i can do what is right