Occlusal Interferences during Eccentric Movements — How to Detect and Eliminate Them

An occlusal interference is a contact between antagonists that occurs only during mandibular movement—not in centric occlusion. These contacts are the most frequent cause of ceramic fractures, loosening of implant screws, and temporomandibular joint pain.

What is Occlusal Interference and Why Does It Damage Prosthetic Restorations

In eccentric movements, the mandible moves forward (protrusion) or sideways (laterotrusion). Teeth should not collide during these movements—with the exception of guiding teeth (canines during laterotrusion, incisors during protrusion).

An interference is a contact that appears where it shouldn't. Consequences:

• Ceramic fracture—the contact point acts as a wedge, concentrating stress
• Implant screw loosening—lateral forces exceed the tolerance of the connection
• TMJ pain—the joint compensates for the abnormal mandibular movement path
• Root fracture—a natural tooth loaded laterally beyond its strength

Types of Interferences

Working side interferences—occur on the side to which the mandible moves. E.g., during right movement, contact on the right premolar which should be free.

Non-working side interferences—occur on the side opposite to the movement. This is the most dangerous type: forces act horizontally on teeth not adapted for such loads.

Protrusive interferences—contacts on posterior teeth when the mandible is brought forward. Only incisors should guide in protrusion.

How to Detect Interferences in the Clinic

40 µm articulating paper—the patient bites in CR, then performs eccentric movements. Marks that appear only during movements (not in bite) are potential interferences.

Two-color articulating paper—one color for CR (e.g., blue), the second for movements (e.g., red). Points where both colors overlap are dynamic contacts requiring analysis.

T-scan (digital analysis)—precise mapping of forces and contact sequences over time. Allows seeing not only where, but when and with what force contact occurs.

How to Eliminate Interferences

On a natural tooth—selective grinding of enamel at the contact point. Check with articulating paper after each grinding. Goal: no contact during eccentric movements, maintain contact in CR.

On a ceramic crown—gentle adjustment with re-polishing if the contact is minimal (up to 0.2 mm). For deeper adjustments—remake the crown with corrected occlusion in CAD.

On an implant—interferences with implants are more destructive because the implant lacks a periodontal ligament (no proprioception and micromovement). Adjustment must be precise—preferably on an articulator before seating.

The Role of the Lab in Eliminating Interferences

At deltalabs., dynamic occlusion is verified on a semi-adjustable articulator before sending out the restoration. We check:

• Contacts in CR
• Canine guidance during laterotrusion
• Incisal guidance during protrusion
• Absence of non-working side contacts

If the clinician provides a CR bite registration + a protrusive registration, we can program the articulator individually and eliminate interferences already at the CAD design stage.

1. How to distinguish an interference from a correct contact?

A correct contact is present in centric occlusion (CR or MIP). An interference appears only during jaw movement—and causes deviation in the movement path or blocking.

2. Does every interference require correction?

Not every one. Minimal contacts that do not cause clinical symptoms and do not threaten the prosthetic restoration can be monitored. But non-working side contacts and interferences on implants should always be eliminated.

3. How can I help the lab detect interferences?

Provide a CR bite registration (not MIP), a protrusive registration, and occlusal photos with articulating paper. The more data the lab receives, the more precisely it can design the occlusion.