Inaccurate occlusal scans lead to significant complications during the seating of restorations, resulting in tedious chairside adjustments or costly laboratory remakes. Achieving precise intermaxillary relations requires a combination of proper clinical technique and a thorough understanding of the software’s optimization tools.
Best Practices for Occlusal Accuracy
Mandatory Check: Before dismissing the patient, always verify that the digital occlusal contact points match the clinical presentation.
Common Causes of Inaccurate Occlusion and Solutions
1. Surface Contamination (Saliva, Blood, or Debris)
Issue: If the occlusal surfaces are not dried, the software may interpret liquid or debris as tooth structure. This "add-on" data prevents the arches from sitting together correctly, resulting in an "open bite" or elevated occlusion in the digital model.
Solution: Clear all foreign objects from the mouth. Use an air syringe to thoroughly blow-dry the occlusal and buccal surfaces immediately before scanning.
2. Unstable Anterior Scanning
Issue: Scanning only the anterior region for full-arch or anterior restorations often provides unstable data, as the patient may not have consistent posterior stops, leading to "propped" or tilted occlusion.
Solution: Focus the bite registration on stable, posterior contact areas. Avoid scanning edentulous spaces. Capture approximately 2–3 teeth per quadrant; scanning too long a segment can introduce rotational errors.
3. Patient Positioning (Supine vs. Upright)
Issue: When a patient is in a fully reclined (supine) position, the mandible can shift posteriorly due to gravity, leading to a "centric relation" mismatch.
Solution: For the most accurate "habitual" occlusion, adjust the dental chair to a more upright position. Support the patient's chin lightly to ensure the mandible does not drift during the scan.
4. Muscle Tension and Guarding
Issue: If the patient is tense, they may bite harder on one side or prematurely shift their jaw, resulting in an asymmetrical or canted bite.
Solution: Before activating the scanner, have the patient practice swallowing and biting together several times to find their natural, relaxed maximum intercuspation (MIP).
5. Premature Scan Activation
Issue: Starting the scan while the scanner is still entering the mouth or before the patient has fully closed can capture "motion artifacts" or transitional data, causing the software to misalign the arches.
Solution: Position the scanner intraorally while in Pause mode. Retract the buccal mucosa, instruct the patient to bite down firmly, and only click the Start button once the patient is in a stable, stationary occlusion.
Utilizing the Occlusion Check Module
Standard protocol requires capturing bite registrations on both the left and right sides. While the software’s "Optimized Bite" is the default and is suitable for most cases, you can manually override the alignment if the result is unsatisfactory.
Alternative Alignment Options
If the initial optimization does not look correct, navigate to the Occlusion Check module to choose from four alternative relationships:
Bite 1: Raw data from the first side scanned.
Bite 2: Raw data from the second side scanned.
Optimized Bite (Default): The software’s weighted average of both sides.
Auto Bite: An algorithmic alignment based on tooth morphology.
Note: After selecting an alternative (e.g., "Bite 1"), you must click OK and allow the Optimization Check to finish. The changes are not finalized until the calculation stage is complete. If none of the four options align correctly, delete the occlusal data and rescan.