Quantitative analysis of substance removal during tooth preparation for full ceramic restorations using digitally generated preparation designs.

Abstract

Objectives: This study aimed to determine which factors most strongly affect volumetric tooth substance removal during preparation for full ceramic restorations and how these parameters interact. A novel digital method was used to design preparation geometries using three-dimensional (3D) graphic software.

Materials and methods: A digital workflow involving Boolean operations was applied to an STL dataset of a maxillary first molar to generate 720 preparation designs. Each design varied by preparation angle, chamfer depth, finish line distance from the cementoenamel junction (CEJ), and occlusal reduction. Volumetric tooth removal was evaluated for each parameter, as well as for their combined effects.

Results: All preparation parameters influenced tooth substance removal. The finish line distance from the CEJ showed the greatest effect, followed by chamfer depth. Preparation angle and occlusal reduction had less pronounced effects.

Conclusions: Increasing the vertical finish line distance and minimizing chamfer depth substantially reduce tooth substance removal. While adequate occlusal clearance is essential, its effect on total volume loss is relatively minor. The influence of the preparation angle was more relevant for full crowns than for partial restorations.

Clinical relevance: Clinicians are encouraged to favor partial restorations whenever possible, as they result in less invasive preparations, even when compared to full crowns made from high-strength materials with reduced thickness requirements such as monolithic zirconia. To preserve tooth structure, both the material's minimum thickness and the vertical position of the finish line should be carefully considered. These findings support a conservative preparation approach tailored to material properties and clinical requirements.