Bone Elastic Modulus in Carl Misch Text: Explanation?

ummm - ok I think your getting mixed up with concepts - elastic modulus relates to a property of bone when described in this book the reference to this property is related to the material behaviour of bone whilst osteotomy creation - i. e use of drills, more so relevant when using condensation of bone and manipulating it to create a osteotomy. On the other hand you then relate this elastic modulus with the physiological behaviour of integrated implants under different loading forces. The modulus of elasticity of the bone has no relationship with the physical effects of specific directional forces placed upon an implant - those effects are due to a cellular level response of bone to lateral forces and axial forces that + stimulates osteoblastic / clastic activity - One is a physical measurement i.e modulus of elasticity of bone and the other a physiological response to forces applied - the 2 dont really relate - hope this makes sense

Hi, I will try to help you with this.... you quoted the book correctly but you are mixing bone elasticity concepts with osseointegration and Im sory but they are not the same. Bone elasticity is not really stiffness its the force under it will bend before breaking or become permanently deformed(plastic deformation). I wish we could use those kinds of lateral loads but as I said before osseointegration is a different game. Achieving osseointegration is one thing and preserving it is another. Remember that we dont have a pdl and so if you load the implant in the wrong way(to much or to laterally.. etc) you will not get the normal remodelling that you would obtain on a natural tooth (orthodontics) you will get bone loss... bone compression (specially towards buccal) is in the long run pretty much a sinonim of bone loss(bone resorbtion)and this is valid for, I would say, every screw implant out there. There are other kinds of implants that use the lateral and oclusal loads to preserve the bone(i.e. endopore) but they have limits also.I hope this was clear enough.

Dr. Berg is correct. Modulus of elasticity refers to the ability of a substance to bend, deform or flex before breaking or fracturing. The higher the number, the MORE elastic, MORE flexible the substance is. The MORE COMPACT a substance is, the MORE STIFF it is, the LESS FLEXIBLE. Titanium has 97 MOE therefore, it is MORE COMPACT, MORE BRITTLE, MORE STIFF and LESS FLEXIBLE than bone. The deeper one goes occluso-apically, the more compact the bone becomes, the more resistance it will exert against masticatory forces. Off-axial forces are more destructive to the bone and the implant because structural dimensions are THINNER in those directions, thereby offering LESS resistance. It all boils down to ratio and proportion.

n Dear Doc, The figures you quote (verbatim from Dr Misch) are a reflection of the ability of the bone in those spatial axes to deform/not deform under load (as already pointed out by previous posts here). If you look at it this way - Orthodontists have the greatest trouble intruding teeth rather than bodily moving them or tipping them. Therefore, the lateral movement or antero-posterior (bucco-lingual) movement obviously is much less resisted by the bone surrounding the tooth/implant. The MOE of bone being greatest (of the 3-dimensions in question)in the Mesio -distal plane(910) and least in the Occlusal-apical plane (114) (as quoted by you), is a reflection of the same point. This most certainly pertains to the arrangement of the bony trabeculae along three specific axes and their ability therefore, to dissipate occlusal load along those planes according to the orientation of the trabecular axes (ref: John Brunski). This also explains why Long bones such as the Tibia, femur etc resist torsional load much less and can take on Vertical(Compressive loads)so as to be called weight bearing bones (owing to their endochondral origin and formative mechanisms)whereas, facial, skull and jaw bones (being membranous in their origin)take on torsional (non-axial loads) much better than they do Compressive loads. However, in the case of the Implant, the insistence on Axial loading comes from the fact that, bone gives way under Non-axial load( on the side of Orthodontic movement), but the absence of PDL attachment to the Implant surface does not facilitate its continued presence in the bone like it would in the case of a natural tooth. Hope I didn't complicate things further. But I liked this post ! Thanks everyone. Cheers Dr jeevan Aiyappa