CATEGORY 46 AUSTRALASIAN DENTIST and secondary implant stability. A number of studies have demonstrated this very elegantly indicating lower primary stabilities and ISQ values where there is poor quality trabecula bone typically in the maxilla. Higher primary values most commonly occur in the mandible. As time passes and there is bone remodelling and new bone formation at the implant bone interface; osseointegration there is a change and an increase in primary implant stability to a point of equilibrium some 12 to 20 months following implant placement. This has been demonstrated in a number of studies. This is commonly seen in the maxilla but is not so obvious in the mandible and can be explained quite simply because the bone to implant contact in the mandible is much higher because of the ratio of cortical to trabecula bone. Maxillary bone typically has a thinner cortical plate with a more open trabecula network but it may be argued that the high level of vascularity of this bone structure contributes to more bone formation and at a faster rate (Figure 7.). A study by Glauser was one of the first to demonstrate the ability of RFA to be able to discriminate between successful and potentially failing implants. In this study within two to three weeks of implant placement. A decrease in RFA and ISQ values can be measured before any physical or radiographic signs or potential failure. Where there is a decrease in ISQ following implant placement prudent action such as the removal of a temporary crown, transition from a healing abutment to a cover screw may have the potential to rescue and save a potentially failing implant. Osstell first became a commercial product from Integration Diagnostics in 1989 and this utilised an elegant instrument produced from a milled aluminium enclosure of high aesthetic appeal. However, the device still used the beam transducer albeit produced to a much more aesthetic level then it’s earlier research siblings (Figure 8.). An important parameter became evident in the measurements of implant stability; the stability of an implant in bone is not axi-symmetrical i.e. the same all the way around. This can be mapped in the mandible for example where the stiffness is much less mesio-distally than it is bucco-lingually. (Figure 6.) Measurements indicated that in many cases the stability was the same or very similar in all directions. However, in important situations such as extraction sites, proximity to the maxillary sinus, grafted sites and the use of maxillofacial implants the stability profile could be quite complex. The RFA transducer is able to deduce and resolve the main Principle stiffness is or stabilities of the implant in two directions perpendicular to each other. This gives a measurement of effectively the maximum and minimum Principle stiffness. This was rather difficult to isolate with the beam transducer that had previously used. Development continued in transducer design and a breakthrough was made in the evolution of the smart peg. This is a simple passive aluminium beam which could be screwed into an implant or into an abutment and which carried a small magnet. The smart peg can be excited remotely and in any non-contacting manner without any connected wires (Figure 9.). The Osstell handheld probe contains a series of coils that alternately excite and measure the response of the vibrating beam by using a frequency sweep and an analysis method called a fast fourier transform (Figure 10.). From this it is possible to isolate and identify the 1st and 2nd mode ISQ values. Thus, it became very straightforward and easy to measure ISQ values in extraction sockets and grafted sites. Electronic technology has evolved rapidly in the last 10 years especially with the introduction of Digital Signal Processing technology which has overtaken more traditional analogue methods. The CD, web streaming and mobile phones are perfect examples of this evolution. Osstell has continued to be developed in recent years with the introduction of progressively simpler, faster and more friendly to use instruments including Ostell Mentor and Osstell IDX. It is important to know however the accuracy, repeatability and INNOVATIONS Figure 7 Figure 9 Figure 11 Figure 8 Figure 10 Figure 12 Figure 6
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