Take home messages

  • Current measures of primary stability in the clinical setting are the insertion torque (IT) and the implant stability quotient (ISQ). Both are "static" measures, as they assess primary stability at a single moment of placement (IT) or when the implant is already inserted (ISQ).
  • Some researchers had previously suggested using "dynamic" stability measures, such as the amount of energy exchanged between the implant and bone during its descent into the implant tunnel
  • IDI Evolution has defined a dynamic parameter, the integral of the torque-depth curve, and has enabled its measurement through the TMM3 micromotor, thus making it possible to dynamically measure primary stability in the clinical setting.
  • IDI Evolution validated this dynamic measure of primary stability through multiple studies, demonstrating that the Integral also measures the mechanical stress experienced by bone during insertion, paving the way for rational study of cortical preparation in relation to early and late marginal bone loss (MBL).

The insertion torque (IT) and the implant stability quotient (ISQ) are the two parameters used in clinical practice to measure implant primary stability. While relevant, they suffer from a weakness: they are static parameters. Insertion torque, IT, is in fact the maximum torque required to insert the implant: this value is recorded at a single moment during the implant's descent into the implant tunnel, which can be misleading (consider, for example, an implant inserted into D4 bone stabilized only by an apical cortical layer). The ISQ can be recorded only when the implant is fully positioned: it measures, in simple terms, how much the implant can "oscillate" laterally, but its magnitude reflects a stationary condition, the final one with the implant inserted.

In the past some researchers wondered if dynamic measures – capable of taking into account all the interactions the implant has had with the bone tissue while descending into the tunnel – could provide more information regarding implant stability, discerning situations that are substantially different but not distinguishable in terms of IT or ISQ. An excellent candidate for a dynamic parameter of primary stability is insertion energy, IE, which is the amount of energy exchanged between the implant and bone during its placement.

This parameter can be calculated by mathematically integrating the torque-time or torque-depth curve, two interchangeable quantities. IDI Evolution introduced into their TMM3 motor the capability to measure, at each implant insertion, the integral of the torque-depth curve and demonstrated in 2018, in a study on model systems (synthetic blocks), conducted in collaboration with the Vita-Salute San Raffaele University of Milan, not only that this parameter effectively measures implant primary stability but that is is even  way more sensitive to bone density variations than IT and ISQ. The same result was achieved in 2019 on equine bone, obtaining independent confirmation on a different experimental model.

But there's more: a further study conducted in 2018 on photoelastic resins showed that the Integral is also a measure of the mechanical stress experienced by the bone tissue, both along the entire implant tunnel and, more importantly, in the coronal portion, paving the way for the possibility of objectively measuring one of the parameters that could influence both early and late marginal bone loss. These results could allow for an objective evaluation of the role of cortical bone (and, therefore, its preparation) in achieving the desired primary stability.

References

Di Stefano DA, Arosio P, Gastaldi G, Gherlone E. The insertion torque-depth curve integral as a measure of implant primary stability: An in vitro study on polyurethane foam blocks. J Prosthet Dent. 2018 Nov;120(5):706-714. doi: 10.1016/j.prosdent.2017.04.012.
Link to the article
IF: 5,600 (2025)

Orlando F, Arosio F, Arosio P, Di Stefano DA. Bone Density and Implant Primary Stability. A Study on Equine Bone Blocks. Dent J (Basel). 2019 Jul 1;7(3):73. doi: 10.3390/dj7030073.
Link to the article
IF: 3,400 (2025)

Andreasi Bassi M, Arosio P, Di Stefano DA. Evaluation of Peri-implant Bone Stress on D1 Bone Using a Computerized Torque-Measuring Implant Motor: A Study on Photoelastic Resin Blocks. Int J Oral Maxillofac Implants. 2018 July/August;33(4):770–778. doi: 10.11607/jomi.6079.
Link to the article
IF: 2,000 (2025)

 


The left image show how the Integral (the upper line) varies more significantly (the line is steeper) with density changes compared to IT and reverse torque (the other two lines in the same plot, less steep) or ISQ (the line in the other graph, less steep). The central figure shows how, by employing photoelastic resins, it is literally possible to "visualize" the mechanical stress the bone undergoes around the implant: stress is measurable, and its magnitude is perfectly correlated (right figure, the points align with the line) with the Integral values measured during placement: the Integral not only measures primary stability but also the mechanical stress around the implant. This opens the possibility for a rational analysis of stress on the cortical portion alone and, therefore, investigating the link between cortical preparation and early or late marginal bone loss.

What is the importance for clinical research?

  • Thanks to IDI Evolution, researchers can now measure primary stability through a dynamic parameter. This allows for more refined research than that that could be conducted using only IT or ISQ and may lead to a better understanding concerning how implant tunnel preparation or macro- or micro-implant morphology can affect the bone-implant dynamic energy exchange.
  • Additionally, the possibility of measuring mechanical stress on the cortical portion of bone tissue paves the road to investigating the relationship between cortical tunnel preparation and early or late marginal bone loss.

What is the impact on everyday operations?

  • Exploiting the Integral to measure of primary stability reaches its full potential when a fully characterized implant system, such as those by IDI Evolution, is being used.
  • IDI Evolution implants are, in fact, fully characterized: given a site-specific bone density and an IDI Evolution implant having given diameter, appropriate mathematical algorithms can predict its behavior in terms of Integral, or primary stability, relative to the preparation of the implant site. This can be thus modulated based on the intended load (immediate, early, deferred) to be applied.
  • Even when not using IDI Evolution implants, however, the oral surgeon will benefit from the ability to measure primary stability in a way that is more sensitive to bone density variations and provides information concerning all the interactions the implant has had with bone tissue. Surgeons, moreover, can also exploit the information provided by  the torque-depth curve TMM3 plots on its display, and assess if the stability achieved is consistent with that expected according to the site preparation protocol that had been applied. 

In support of IDI Evolution devices

TMM3 provides, in a single device, everything necessary to achieve truly predictable implantology: it allows site-specific measurement of bone density, providing the surgeon with precise information about bone quality at the exact point where the implant will be placed, complementing what is already known from CBCT scans; it thus provides the basis for modulating the implant tunnel preparation, especially if the implant has been adequately characterized by the manufacturer, as is the case for all IDI Evolution implants; it allows verification in terms of Integral, more sensitive to bone density variations, of the primary stability achieved, thus confirming in real time the validity of the clinical choice made. Each step is precise, rational, measurable, and contributes to increase the predictability of implant placement and, therefore, the success of the entire prosthetic rehabilitation.

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We have paved the way to provide objective protocols for undersizing the cortical layer, making the clinical procedure reproducible, and the outcome predictable in terms of MBL

The relationship between the extent of cortical undersizing, the primary stability it allows to achieve, the early and late marginal bone resorption it may induce has still not been clarified: studies on this matter are contradictory and inconclusive.
However, IDI Evolution systems are the only ones capable of site-specific discrimination and operator-independent assessment of different combinations of cortical thickness and cancellous density, providing a measure of implant primary stability, the Torque-Depth Integral, which also evaluates the mechanical stress exerted on the cortical thickness.

Read moreabout We have paved the way to provide objective protocols for undersizing the cortical layer, making the clinical procedure reproducible, and the outcome predictable in terms of MBL

We have demonstrated that the IDI bone density diagnosis system can distinguish between different cortical-trabecular combinations, paving the way for a new objective bone classification

The research carried out by IDI Evolution shows that TMM3 measures even bone quality, that is the combination of a given cortical layer thickness and a given trabecular density.

Read moreabout We have demonstrated that the IDI bone density diagnosis system can distinguish between different cortical-trabecular combinations, paving the way for a new objective bone classification

We have defined an objective method for rationally choosing both the protocol for preparing the implant site and the shape and dimensions of the implant to be used

The Integral of the torque-depth curve, measured by TMM3 during implant insertions, varies predictably in relation to how underprepared the implant tunnel is.
The variation of the Integral is also predictable when altering the implant geometry, both in terms of shape (conical, cylindrical, etc.) and dimensions (diameter/length).
The mathematical algorithms describing these variations are also influenced by bone density.

Read moreabout We have defined an objective method for rationally choosing both the protocol for preparing the implant site and the shape and dimensions of the implant to be used