Digital dentistry has transformed restorative workflows.
Today, clinicians routinely focus on the accuracy of intraoral scanners, the capabilities of design software, and the properties of restorative materials. Yet once a restoration enters the milling machine, many assume the process is largely standardized.
A recent study challenges that assumption.
Researchers investigated whether different CAD/CAM milling protocols influence the adaptation, marginal quality, and occlusal anatomy of monolithic zirconia crowns. Their findings suggest that the answer is yes.
The study evaluated 39 monolithic zirconia crowns fabricated using three different milling protocols:
Slow milling Normal milling Fast milling
All crowns were designed using the same digital workflow and fabricated from the same zirconia material. The only variable that changed was the milling protocol.
The researchers then assessed:
Internal adaptation
Marginal quality
Occlusal anatomy
Dimensional discrepancies
The objective was to determine whether milling speed influences the final quality of the restoration.
When adaptation was evaluated, the normal milling protocol consistently demonstrated the smallest gaps in critical regions such as the axio-occlusal angle and occlusal surfaces.
Interestingly, no significant differences were observed at the crown margins, gingival-axial angles, or axial walls.
This suggests that while all protocols produced clinically acceptable marginal adaptation, differences became more evident in areas where geometry was more complex.
For clinicians, these findings are important because occlusal and internal discrepancies may influence seating, occlusal adjustment requirements, and long-term restorative performance.
Perhaps the most clinically interesting finding involved occlusal morphology.
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