Standardized Ex Vivo Photographic Assessment of Milled PMMA and DLP-Printed Single Crowns: A Comparative Study of Human Ratings and Computer-Assisted Image Analysis

Abstract

 Background/Objectives: Standardized photography may support the visual assessment of digitally manufactured provisional restorations, although evidence regarding its feasibility in exploratory comparisons remains limited. This ex vivo pilot study evaluated a photographic protocol for comparing a milled polymethyl methacrylate (PMMA) crown with a digital light processing (DLP)-printed provisional-resin crown.  Methods: One crown was produced by each manufacturing workflow from the same mandibular first-molar digital design. Following workflow-specific post-processing, the specimens were coded and photographed under standardized positioning, illumination, exposure, white balance, magnification, and cross-polarization. Blinded evaluators assessed overall appearance, naturalness, anatomical form, morphological detail, symmetry/harmony, and photograph-based clinical acceptability. Exploratory computer-assisted image descriptors were also used to assess edge definition and surface-texture uniformity.  Results: Descriptive human ratings showed a preference for the milled specimen, particularly regarding morphological detail and surface uniformity. Computer-assisted descriptors indicated a similar direction. Because only one crown represented each manufacturing workflow, inferential comparisons and generalization to the respective manufacturing methods were not considered appropriate.  Conclusions: The standardized photographic protocol was feasible for identifying visual differences between the investigated specimens. The findings are hypothesis-generating and require confirmation using independently manufactured crowns, multiple production batches, blinded assessment, and prespecified statistical analysis.

Keywords: CAD/CAM; dental photography; digital light processing; exploratory pilot study; polymethyl methacrylate; provisional Crown; subtractive manufacturing.