RESUMEN
PURPOSE: The goal of this study was to assess the accuracy and reliability of a low-cost portable scanner (Scanify) for imaging facial casts compared to a previously validated portable digital stereophotogrammetry device (Vectra H1). This in vitro study was performed using 2 facial casts obtained by recording impressions of the authors, at King's College London Academic Centre of Reconstructive Science. MATERIALS AND METHODS: The casts were marked with anthropometric landmarks, then digitised using Scanify and Vectra H1. Computed tomography (CT) scans of the same casts were performed to verify the validation of Vectra H1. The 3-dimensional (3D) images acquired with each device were compared using linear measurements and 3D surface analysis software. RESULTS: Overall, 91% of the linear Scanify measurements were within 1 mm of the corresponding reference values. The mean overall surface difference between the Scanify and Vectra images was <0.3 mm. Significant differences were detected in depth measurements. Merging multiple Scanify images produced significantly greater registration error. CONCLUSION: Scanify is a very low-cost device that could have clinical applications for facial imaging if imaging errors could be corrected by a future software update or hardware revision.
RESUMEN
STATEMENT OF PROBLEM: Heat-polymerized polymethyl methacrylate denture bases deform during and after polymerization, and this deformation may affect the clinical performance of complete dentures. PURPOSE: The purpose of this study was to investigate the processing deformation of 3 denture base materials on a standardized anatomic model by using a contact scanner and surface matching software. MATERIAL AND METHODS: Maxillary reproductions of a definitive cast were digitized by using a contact scanner. The casts were allocated to 4 groups, depending on the denture base material: compression molded (heat polymerized, polymethyl methacrylate based); injection molded (heat polymerized, polymethyl methacrylate based); manually adapted and light-polymerized (urethane dimethacrylate based); and manually adapted, compression molded, and light-polymerized (urethane dimethacrylate-based). The intaglio surfaces of denture bases fabricated on each replicate cast also were digitized by using the contact scanner. Surface-matching software was used to measure dimensional changes between each cast and its corresponding denture base. The Kruskal-Wallis analysis of variance based on ranks was used to assess differences in contraction, expansion, and overall change among groups. The Mann-Whitney U test was performed to determine differences among individual groups. Statistical significance was inferred when P<.01 to compensate for multiple group comparisons. RESULTS: Statistically significant differences in processing deformations were observed among polymethyl methacrylate-based resins and urethane dimethacrylate-based resin. No differences were observed between compression molding and injection molding or between manual adaptation alone and the combination of manual adaptation and compression molding. CONCLUSIONS: Urethane dimethacrylate-based resin showed greater processing deformation compared with polymethyl methacrylate-based resins. Compression molding and injection molding techniques produced similar results for the polymethyl methacrylate-based resins. The methodology used showed patterns of deformation that were too complex to be accurately analyzed by linear measurements.