Miniscrews in Orthodontics

In orthodontics, miniscrews are often described as a simple solution. They are small, minimally invasive, and widely used to provide stable anchorage. But in reality, their
success depends on something extremely precise:

how they are inserted into the bone.

Not just where, but at what angle. A 3D finite element study analyzed this exact variable, comparing different insertion angles across three types of miniscrews and revealing a key insight:

there is no universal rule, each system behaves differently .

The Hidden Variable Most People Overlook

When miniscrews are placed, clinicians typically consider:

• bone quality
• anatomical position
• screw length and diameter

However, the insertion angle directly affects:

• stress distribution in bone
• mechanical stability
• risk of loosening

The study simulated insertion at:

• 15°, 30°, 45°, 60°, 75°, and 90°

and applied a standard orthodontic force of 200 grams to evaluate how stress spreads through the bone .

What Actually Happens Inside the Bone

The 3D models highlight an important concept:

• forces are not distributed evenly
• stress concentrates at specific points around the screw
• different angles shift these stress patterns

This matters because:

• excessive stress increases the risk of instability
• optimal stress improves anchorage and predictability

In practical terms, the wrong angle can compromise the entire system.

Key Insight 1: 90° Is Often the Most Stable

For two miniscrew types, Jeil and Storm, the study found that:

• the lowest stress in bone occurs at 90° insertion
• deformation is minimized
• overall stability improves

For example:

• Jeil showed the lowest stress values in both cortical and cancellous bone at 90°
• it also recorded the lowest deformation, around 4.5 micrometres

This confirms that perpendicular insertion can offer excellent stability in many cases.

Key Insight 2: Not All Miniscrews Behave the Same

The Thunder miniscrew showed a completely different pattern:

• its optimal angle was 15°
• higher angles increased stress in the surrounding bone

This highlights a crucial principle:

• the same technique cannot be applied to every system
• design, diameter, and geometry influence biomechanics

Each miniscrew has its own ideal insertion angle .

Key Insight 3: Stress Distribution Is What Really Matters

The study evaluates von Mises stress, a key parameter used to understand how forces are distributed.

Why this is important:

• when stress stays below the bone’s tolerance, stability is maintained
• when stress concentrates excessively, the risk of failure increases

The data shows that:

• all configurations remained within safe limits
• some angles significantly reduced stress compared to others

This is not just about safety, but about optimization.

Clinical Implications

In real-world orthodontics, this translates into a more precise approach:

• miniscrew success depends on how accurately they are positioned
• angle selection should be tailored to the specific system
• biomechanical planning is as important as clinical execution

This also explains why:

• similar treatments can produce different results
• some miniscrews fail despite correct placement

A Key Biomechanical Balance

There is an important balance to consider:

• lower angles increase bone contact
• perpendicular angles improve stress distribution

More contact does not always mean more stability.
In many cases, controlled stress distribution plays a bigger role.

What This Means for Patients

For patients, this level of precision results in:

• more stable orthodontic anchorage
• fewer complications
• more predictable tooth movement
• reduced need for repositioning

It reflects a more advanced approach based on data and biomechanics, not approximation.

Conclusion

Miniscrews are a powerful tool in modern orthodontics, but their effectiveness depends on precise biomechanical control.

Clinical evidence shows that:

• insertion angle significantly affects stress distribution
• 90° is often optimal, but not in every case
• each miniscrew design requires a specific approach
• stability depends on how forces are transmitted to bone

In orthodontics, small technical details can make a significant clinical difference.