Implant stability is considered crucial for the maintenance of osseointegration1 that could be de?ned at the primary and secondary level. Primary stability is defined at the time of placement as it re?ects the degree of mechanical interlocking between the implant and the surrounding bone.2 It is often related to the degree of bone compression and could therefore be in?uenced by bone quality and quantity, the surgical technique, and implant design and characteristics3. Secondary stability, on the other hand, is a biologically induced dynamic mechanism4 involving bone formation, maturation and remodelling at the implant–bone interface5. Subsequently, in the past, implant stability had been assessed using several methods at different clinical time points.6
The new magnetic Resonance Frequency Analysis device has a transducer also referred to as smartpeg; a metallic rod with a magnet on top, which is screwed onto an implant or abutment. The magnet is excited by a magnetic pulse from a wireless probe. The pulse duration is about 1 millisecond. The smartpeg vibrates freely after excitation and the magnet induces an electric voltage in the probe coil. That voltage is the measurement signal sampled by the resonance frequency analyzer. With this method, implant stability is measured either by determining the resonance frequency of the implant-bone complex or by reading an ISQ value given by the Osstell apparatus (Integration Diagnostics AB, Gothenburg, Sweden). Classically, the ISQ has been found to vary between 0 to 100, the higher the ISQ, the higher the implant stability.3 The factors believed to influence the ISQ score are implant parameters i.e. implant length, diameter and surface characteristics, and implant bed condition.
Extensive research has been carried out to determine the correlation between these factors and RFA measurements. The ?ndings, however, were highly variable. For example, Some authors7, suggest that using longer and wider implants increases primary stability due to the increased bone-implant contact surface area. However, studies conducted by Lopez et al, Balleri et al. and Zix et al, the RFA does not confirm this clinical supposition, since no statistically significant differences were found with regard to length or diameter in relation to the ISQ.8 Also Alsabeeha et al has concluded in her research that host-site-related variables such as age and gender of participants or bone volume and quality have no signi?cant impact on the primary stability measurements of the implants using RFA.9
Several authors 10 showed that implant stability quotient (ISQ) values correlated well with bone quality as de?ned by Lekholm & Zarb (1985). Others demonstrated a weak correlation between bone quality and operator received primary stability on the one hand and ISQ values on the other. Lack of signi?cant correlation between ISQ values and microcomputer tomographic analysis of bone volume density or trabecular connectivity was also observed11. Clinically, RFA could be more useful in monitoring implant stability over a period starting from the time of implant placement and throughout the healing phase. Repeated measurements at separate intervals following implant insertion were thought to determine the appropriate time of loading 12 and to predict early signs of clinical failure. 13
The overall objective of this study was to quantify and compare the stability of dental implant obtained at different time intervals during the healing period placed in 4 different densities of bone. Specifically, 96 implants in different bone types were evaluated and compared for over a period of 3 months. The Osstell device (Integration Diagnostics, Goteburg, Sweden), which is essentially identical to the RFA developed by Meredith, was able to measure the overall stiffness of the implant/tissue system. The Osstell also served as a sensitive tool for clinically monitoring implant stability in bone of varying density. This finding is in agreement with earlier work.