In this lecture, we will go through the difference between the tooth and the implant from a prosthodontic point of view in order to explain why technical complications are more frequent in implant supported reconstructions compared to tooth supported. Let's compare the tooth with the implant. In teeth, within five years, around 16% of the reconstruction have some complications. On implant supported, it's about twice as much. The most frequent complications on the tooth side is caries and apical lesions. And on the implant side, chipping is most frequent. The main difference is that the tooth has a periodontium, the implant is ankylotic. One of the functions of the periodontium is that it works as a shock absorber. Everywhere around us we have shock absorbing constructions. The periodontium protects the crown from rapid and heavy forces. The dentin also works as a shock absorber. The clinical implication is never to do ceramic reconstructions on both jaws. Do a composite reconstruction in at least one jaw instead. The composite has a shock absorbing function. Compare when hitting two glasses seen to each other. If they are ceramic, they will break easier than hitting one ceramic and one plastic glass. The next difference is that the periodontium allows the teeth to elongate, intrude, rotate and tilt. It allows movements. This can be exemplified with the patients that often say that they feel tension or it feels tight when trying a large framework on the teeth but after around 10 minutes, the spanning has disappeared. The framework has worked as an orthodontic device and move the teeth to a more favourable position depending on the small misfit of the framework. After checking the framework, taking it off also feels easier many times. The implant is ankylotic and will not move. Neither would it follow the growth of the jaws. The clinical implication is that on teeth, the reconstruction will always be strain-free, while on implant there will always, more or less, be a misfit. The bridge will be slightly bent giving unfavourable tension to the ceramics, leading to chip offs or unfavourable loads on the screw. If we take an even closer look to the periodontium, we will find different receptors in the periodontium. Two of these were studied by Trulsson et al., “the saturated and the unsaturated”. In one of many studies, he examined how two of the receptors signal while holding and biting through a peanut. In the bite phase, the saturated receptors trigger at maximum, as soon as, the biting phase started. But they got quickly saturated and stopped triggering, while the non-saturated receptors follow the bite force. He compared natural teeth with complete denture and the implants. In this slide we see the hold and biting force. The patients with dentures and implants lack the receptors. Meaning that they will not feel where the peanut is and have another interception than patients with teeth. It will give a different pattern in the holding and biting phase, so it's not so much about the biting force as it is about the precision. The periodontal receptors signals very detailed information about position, direction and intensity of chew and bite forces. This information is utilized by the brain to regulate the jaws movements during normal operation. Patients with implants which lack this information, demonstrate clear disturbances in the fine motor control of jaw regulations. Also, implant doesn't feel interferences in the same way as teeth. The clinical implication for this is that with teeth, the jaws will automatically try to chew in a cusp fossa relation giving a load through the root. While with implants, the patient can chew a little on the side without knowing it giving bending forces to the reconstructions. So in patients with implants, the reconstruction should have more flat cusps and more narrow occlusal table in order to avoid the bending forces. One of the anatomical difference between the tooth and implant is the fibres supporting the surrounding tissues. In this slide, we can see the fibres that are the same for the teeth and implants. The small dots represent the circumferential fibres surrounding the tooth like a rubber band. But the tooth also have cement in certain fibers or Sharpey's fibres originating from the cement to the bone and the gingival tissues. The clinical implication for this is that the cement can penetrate much easier and deeper when cementing a crown on an implant compared to a tooth. It is sometimes hard to see that there is cement excess and many times you can't see it on the X-ray at all. This can give you fistulas and bone loss. In summary, we do have the differences between tooth and implants is the shock absorbing effect, the movements of the teeth. We have the perception and finally, we have the anatomical differences.