Agurne Uribarri1, Eneritz Bilbao-Uriarte1, Aiora Segurola1, Done Ugarte2, Fernando Verdugo3. 1. Department of Stomatology II, School of Medicine and Dentistry, University of Basque Country, Leioa, Spain. 2. Department of Mechanics and Industrial Production, Higher Polytechnic School, Mondragon University, Arrasate Mondragon, Spain. 3. Department of Periodontics, VA Hospital, Greater Los Angeles Healthcare, Los Angeles, California.
Abstract
BACKGROUND: Despite computer-aided design and computer-aided manufacturing (CAD/CAM) technology improving prosthesis fit, errors inherent to digital workflow still exist. PURPOSE: To measure scanning/milling errors, and identify factors influencing marginal (MD) and internal discrepancy (ID). MATERIALS AND METHODS: After scanning, 22 conical abutments in 5 master casts, 6 suprastructures with more than 2 implants (3, 4, and 6) were CAD designed. Angular deviation and errors in the vertical/horizontal planes were analyzed using a coordinate measuring machine (CMM). CAD suprastructures were milled and MD/ID evaluated with micro-computed tomography (CT) and optic microscopy (OM) at one screw test (OST) and final fit test (FFT). RESULTS: Mean scanning errors, at the vertical/horizontal planes, and angulation error were 3 μm ± 13, 44 μm ± 34, 0.3° ± 0.2°, respectively. Angulation errors nearly double in structures >3 abutments (0.26°vs 0.4°). OM MD in FFT/OST was 57.7 μm ± 13.9/100.7 μm ± 34.6, respectively. Micro-CT FFT-MD was 38.9 μm ± 12.8. Lineal/perimetral ID was 49.6 μm ± 11.9 and 108.2° ± 41.8, respectively. Structures >3-implants were 2.3 times more likely to present higher MD (CI95%:0.4-13.6). Nearly all the internal horizontal gap was due to scanning errors (44 of 49.6 μm). Horizontal scanning errors were three times more likely to present greater ID (CI95%:0.5-17.4). CONCLUSION: Horizontal plane scanning errors are greater than vertical errors. Scanning angulation/milling errors are higher for suprastructures>3implants. Scanning/milling errors are associated with ID/MD, respectively, leading to micro-gap formation. A CMM reduces scanning errors in >3-implant-frameworks before milling the final piece.
BACKGROUND: Despite computer-aided design and computer-aided manufacturing (CAD/CAM) technology improving prosthesis fit, errors inherent to digital workflow still exist. PURPOSE: To measure scanning/milling errors, and identify factors influencing marginal (MD) and internal discrepancy (ID). MATERIALS AND METHODS: After scanning, 22 conical abutments in 5 master casts, 6 suprastructures with more than 2 implants (3, 4, and 6) were CAD designed. Angular deviation and errors in the vertical/horizontal planes were analyzed using a coordinate measuring machine (CMM). CAD suprastructures were milled and MD/ID evaluated with micro-computed tomography (CT) and optic microscopy (OM) at one screw test (OST) and final fit test (FFT). RESULTS: Mean scanning errors, at the vertical/horizontal planes, and angulation error were 3 μm ± 13, 44 μm ± 34, 0.3° ± 0.2°, respectively. Angulation errors nearly double in structures >3 abutments (0.26°vs 0.4°). OM MD in FFT/OST was 57.7 μm ± 13.9/100.7 μm ± 34.6, respectively. Micro-CT FFT-MD was 38.9 μm ± 12.8. Lineal/perimetral ID was 49.6 μm ± 11.9 and 108.2° ± 41.8, respectively. Structures >3-implants were 2.3 times more likely to present higher MD (CI95%:0.4-13.6). Nearly all the internal horizontal gap was due to scanning errors (44 of 49.6 μm). Horizontal scanning errors were three times more likely to present greater ID (CI95%:0.5-17.4). CONCLUSION: Horizontal plane scanning errors are greater than vertical errors. Scanning angulation/milling errors are higher for suprastructures>3implants. Scanning/milling errors are associated with ID/MD, respectively, leading to micro-gap formation. A CMM reduces scanning errors in >3-implant-frameworks before milling the final piece.