Effect of simulated bur radius compensation on full-contour CAD crown morphology and trueness across tooth types. An in- silico study.

Abstract

To systematically investigate and quantify the influence of bur radius compensation size on the design parameters of full-contour computer-aided design (CAD) crowns. The study analyzes the deterministic trends in morphological characteristics, surface area, volume, and geometric trueness across varying tooth anatomies to provide data-driven guidelines for CAD protocols. This study utilized a deterministic computer simulation to generate idealized virtual crown designs for three distinct anatomical tooth types (molar [#3], premolar [#5], and central incisor [#8]). Because the computational algorithm yields identical outputs from identical inputs with zero variance, a sample size calculation was not applicable; instead, single standardized designs were analyzed. The crowns were processed with seven varying bur radius settings: a 0.00 mm baseline (representing an ideal design with no bur constraints) and six test radii ranging from 0.10 mm to 1.50 mm. The resulting standard tessellation language (STL) files were analyzed using a custom Python algorithm (Eyleen Code) by utilizing Trimesh and NumPy libraries, to calculate trend geometric deviation metrics Root Mean Squared Error (RMSE) and Hausdorff Distance (H.D) relative to the baseline. The simulation data revealed that increasing the bur radius from 0.10 mm to 1.50 mm resulted in progressive morphological changes across all tooth types. A marked trend of volumetric loss was observed; the molar volume decreased from a baseline of 160.60 mm³ down to 135.13 mm³ at the maximum radius. Conversely, surface area and roughness metrics showed a consistent upward trend. Geometric trueness deteriorated substantially with larger radii. While maximum localized deviations (H.D) peaked between the 0.75 mm and 1.00 mm settings, overall morphological deviation (RMSE) continued to climb, peaking at the 1.25 mm to 1.50 mm settings depending on the tooth type. Specifically, the RMSE for the central incisor rose from 0.049 at the minimal compensation to a peak of 0.184, indicating substantial volumetric and geometric distortion compared to the ideal baseline design. The selection of bur radius size directly dictates the morphological reliability of dental CAD. The data demonstrate that a minimal radius (0.10 mm) yields the highest trueness to the ideal baseline, whereas larger settings cause substantial volumetric reduction and geometric deviation, particularly in posterior teeth. To minimize anatomical discrepancies, digital laboratory workflows better to restrict bur radius compensation to the minimum technically feasible values, pending further validation in physical milling processes.