Effect of Simulated Socket Depth on Primary Stability of Different Dental Implant Macrogeometries: An In Vitro Torque-Time Curve and ISQ Study
This in vitro study demonstrates that progressive reduction of simulated coronal support significantly diminishes primary stability across various dental implant systems, revealing that while torque-time analysis and ISQ are strongly correlated, the magnitude of stability loss and system rankings vary by macrogeometry and measurement metric, indicating no single parameter fully characterizes stability under reduced support.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
When a dentist places a dental implant, the goal is to anchor a metal screw into the jawbone so firmly that it can eventually fuse with the living tissue and support a new tooth. This initial grip, known as primary stability, is the foundation for everything that follows. If the implant wobbles too much at the start, it may fail to integrate and be lost. This stability depends on several factors: how dense the bone is, how the surgeon prepares the hole, and the specific shape of the implant itself. In many real-world cases, such as when a tooth is removed and replaced immediately, there is less bone available to hold the top part of the implant. The bone around the neck of the screw is missing, leaving the implant to rely more heavily on the bone at the bottom and the sides. Understanding how different implant designs handle this lack of top support is crucial for predicting which ones will stay secure.
Researchers at Kagawa University and other institutions set out to test exactly this scenario. They wanted to see how six different commercially available dental implant systems performed when the amount of supporting bone around the top was gradually reduced. To do this, they created a controlled laboratory environment using blocks of rigid polyurethane foam, a material that mimics the density of human bone. They machined these blocks to have perfectly flat tops, and then created simulated holes in some of them to represent missing bone. They made these holes 2 millimeters, 4 millimeters, and 6 millimeters deep, creating a step-by-step reduction in support, while keeping the rest of the setup identical.
The team inserted six different types of implants into these foam blocks. Each implant had a unique design, ranging from straight-sided screws to those with tapered bodies or aggressive cutting threads. For every insertion, they measured two main things. First, they recorded the force required to twist the implant into the foam, known as insertion torque. They did not just look at the highest force reached; they analyzed the entire curve of how that force built up over time. Second, once the implant was in place, they measured its stiffness using a device that sends a vibration through the implant to determine how tightly it was held, a value called the Implant Stability Quotient.
The results showed a clear trend: as the simulated hole at the top got deeper, the stability of every single implant system dropped. The deeper the missing bone, the less force was needed to twist the implant in, and the looser the implant felt afterward. However, the story was not the same for every design. When the missing bone was at its deepest, 6 millimeters, the implants performed differently depending on how their stability was measured. Two of the systems, the BLX and the NobelActive, required the most force to twist in, suggesting they held the tightest in terms of raw rotational resistance. Yet, when the researchers measured the stiffness of the implant after it was placed, two other systems, the PrimeTaper and the EV Straight, showed the highest stability values.
This discrepancy revealed a key insight: the implant that feels the hardest to screw in is not necessarily the one that ends up the most stable once it is seated. The study found that the shape of the implant dictated how it lost its grip. Some designs held their peak strength longer as the support decreased, while others maintained a steady, cumulative resistance throughout the insertion process. One system, the EV Straight, demonstrated the most consistent resistance over time, even though it did not reach the highest peak force. This suggests that different implant shapes interact with the remaining bone in distinct ways, and a single measurement cannot tell the whole story.
The researchers concluded that when the bone around the top of an implant is compromised, the specific design of the implant matters significantly. No single metric, whether it is the force needed to insert the screw or the stiffness measured afterward, fully captures the stability of the implant in these difficult conditions. Instead, a complete picture requires looking at how the resistance builds up during the insertion and how the implant settles afterward. While this study was conducted in a laboratory using foam rather than living bone, the findings offer a detailed mechanical map of how different implant shapes behave when the supporting bone is reduced. This knowledge helps clarify that in situations where bone support is limited, the choice of implant design changes the way the implant secures itself, and different designs may offer different advantages depending on what aspect of stability is most critical.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.