Truss Access Cavities: Practical Advantage or Clinical Compromise?

There has been a clear shift in endodontics over the last few years.

Preserve more dentine. Keep access cavities smaller. Make treatment more “conservative.”

But here’s the question that comes up chairside:

Are we trading off disinfection for dentine preservation?

A recent randomized controlled trial looked directly at this — comparing traditional access cavities (TEC) with truss access cavities (TREC) in mandibular molars.

What the Study Looked At

Patients were randomly assigned to either:

• Traditional Endodontic Cavity (TEC)

• Truss Endodontic Cavity (TREC)

Bacterial samples were taken before and after chemo-mechanical preparation using RT-qPCR analysis. Postoperative pain was recorded daily over 7 days using a visual analogue scale.

What Changed Clinically

Both groups showed a significant reduction in bacterial load after instrumentation.

However, the extent of reduction differed:

• TEC: ~96% bacterial reduction

• TREC: ~92% bacterial reduction

This difference was statistically significant.

In contrast, postoperative pain levels were similar in both groups, with no meaningful differences observed at any time point.

The findings suggest that access cavity design does influence disinfection.

With a traditional access:

• Instrumentation is more direct

• Irrigant penetration is more effective

• Debridement tends to be more complete

With a truss design:

• Access is more restricted

• Instrumentation becomes more technique-sensitive

• Certain areas of the canal system may be less accessible

While the numerical difference in bacterial reduction may appear modest, it becomes clinically relevant in cases where complete disinfection is already challenging.

TREC is designed to preserve dentine and potentially improve fracture resistance. That benefit is appealing, especially in structurally compromised teeth.

However, current evidence—including findings from this trial—suggests that:

• The improvement in fracture resistance may not always be significant

• The reduction in access can make cleaning more difficult

• The technique demands greater precision and operator experience

Importantly, the study also reinforces that access design does not influence postoperative pain, suggesting that patient comfort is unlikely to be affected by the choice of cavity design alone.

In a controlled setting, conservative access designs may be executed predictably.

In routine clinical practice, outcomes are influenced by: