Implant Minute | Implant Stability: The Science of ISQ Explained

Understanding Implant Stability: The Science of ISQ

Old Ways to Check Stability: Why They Fall Short

For a long time, dentists used older methods to check if an implant was stable. These methods tried to feel or hear if the implant was loose. However, these methods had some problems. They were not always accurate or objective.

Here are some older methods that were used:

• Reverse Torquing: This method involved trying to unscrew the implant slightly. If the implant moved or came out, it meant it was not stable. But this test could also disturb the healing process.

• Percussion Test: With this method, the dentist would gently tap on the implant. They would listen to the sound. A duller sound might mean the implant was well-integrated. A ringing sound could suggest a problem. The challenge with this test is that what one person hears as "dull" another might not. It relies too much on what the dentist perceives.

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These traditional tests are not always reliable. They depend heavily on the dentist's personal experience and judgment. This can make it hard to get consistent results. For example, one dentist might feel an implant is stable, while another might not. This is why a more objective and consistent way to measure stability was needed.

Introducing ISQ: A Modern Approach

Today, dentists use a more scientific method called Implant Stability Quotient (ISQ). This method offers a clear, measurable way to check implant stability. ISQ provides an objective reading that does not depend on a dentist's personal opinion or feel. It uses special tools to measure how much an implant moves when a small vibration is applied.

What is ISQ?

The ISQ scale helps dentists understand how stable an implant is. It measures the lateral stability of an implant. Lateral stability refers to how much an implant resists sideways forces. This is important because chewing puts a lot of sideways pressure on teeth.

The ISQ scale ranges from 1 to 100. A higher number means the implant is more stable. A lower number means it has less stability. The ISQ value has a direct link to how much an implant can move, called micromobility. A higher ISQ means less micromobility, which is good.

Understanding ISQ Scores

The ISQ numbers help guide dentists. They show how well the bone is growing around the implant.

Here's how to understand the ISQ scores:

• Above 70: This range means the implant has very high stability. The bone has likely grown very well around the implant. It is strong and ready.

• Between 60 and 69: This range shows medium stability. The implant is integrating well, but might need a little more time to become fully strong.

• Under 60: This indicates low stability. This score is a sign for concern. It suggests the implant may not be integrating properly with the bone.

These numbers give dentists a clear picture. They can use this information to make the best decisions for your treatment plan.

ISQ Versus Torque: Why They Are Different

Sometimes, people confuse ISQ with the torque used when placing an implant. When a dentist places an implant, they use a certain amount of force, or torque, to screw it into the bone. High insertion torque means the implant felt very tight when it went in. But high initial torque does not always mean long-term stability.

What Torque Measures

Torque mainly measures the friction between the implant threads and the bone as the implant is placed. It also measures how the implant threads cut into the bone. Think of it like screwing a screw into wood. The initial tightness (torque) might be high. However, if the wood around the screw is weak or has voids, the screw might not be truly secure over time.

Why Torque Can Be Misleading

There are times when an implant can have high initial torque, but its stability drops later. This often happens with immediate implants.

Imagine an implant placed into a molar site where a tooth was just removed. The socket left by the tooth can be quite large. The implant might feel tight because it is engaging the very bottom, or apical, bone. This means the bottom 2 or 3 millimeters of the implant might have good contact with bone. However, the sides of the implant might have large gaps or voids. These voids mean there is not much bone contact on the sides.

In this situation:

• The initial torque could be very high. This makes the dentist think the implant is very stable.

• But the lateral stability would be low. This is because the implant is not supported well on its sides.

• If a temporary crown were placed on such an implant, it would likely loosen. The ISQ scores for this implant would reflect this low lateral stability.

This example shows that while high torque is good during placement, it does not guarantee long-term stability. ISQ gives a more complete picture by focusing on the lateral stability that an implant needs to last.

How Dentists Measure ISQ

Dentists use special tools to measure ISQ. These tools are designed to give accurate and objective readings. Two common devices are the Penguin and Ostell units.

The Measurement Process

Measuring ISQ is simple and non-invasive. It does not hurt and takes only a few seconds.

Here is how the process works:

1. At Implant Placement: The dentist takes the first ISQ measurement right after the implant is placed. This gives a baseline reading. It shows the initial stability of the implant.

2. During Healing: After 2 to 3 months, or sometimes longer, the dentist takes a second ISQ measurement. This second reading shows how the implant's stability has changed during healing.

The device works by attaching a small sensor to the implant. This sensor sends tiny vibrations to the implant. The way the implant responds to these vibrations tells the device its stability. The device then displays an ISQ score.

Tracking Stability Trends

The real power of ISQ comes from comparing the measurements over time. Dentists look at the trend of the ISQ values:

• Increasing Values: If the ISQ score goes up from the first measurement to the second, this is a positive sign. It means the bone is growing well around the implant. The implant is becoming more stable. This indicates successful osseointegration.

• Decreasing Values (or "Dip"): If the ISQ score starts high (for example, in the 60s or 70s) and then drops significantly (for example, into the 50s), this is a sign for concern. A drop in ISQ values suggests that the implant might not be integrating properly.

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What a Drop in ISQ Means

A drop in ISQ values could indicate several issues:

• Non-integrated implant: The bone has not grown around the implant at all.

• Partially integrated implant: Only some bone has grown around the implant, not enough for full strength.

• Fibrous encapsulated implant: Instead of bone, soft fibrous tissue has grown around the implant. This means the implant is not strong enough.

When a dentist sees a concerning drop in ISQ, they do not just rely on this one test. They use this information along with other checks. These include:

• Radiographs: X-rays help them look at the bone level and implant position.

• Tissue Health: They check the gums around the implant for signs of infection or inflammation.

• Other Information: They review your overall health and how the healing is progressing.

By looking at all this information together, your dentist can make an informed decision. They can decide if it is safe to place the crown on your implant or if more time or treatment is needed.

Conclusion

Implant stability is key to a successful dental implant. Older methods of checking stability were not always accurate. The ISQ method provides a consistent and objective way to measure how well an implant has integrated with your bone. It helps dentists make smart choices about your treatment. By using ISQ along with other checks, your dentist ensures your implant is truly ready for its new tooth. This helps you enjoy a healthy, strong, and lasting smile.