Marta Revilla Leon M.S.D.

Revilla-León, M., M. Sadeghpour and M. Özcan (2020). “A Review of the Applications of Additive Manufacturing Technologies Used to Fabricate Metals in Implant Dentistry.” J Prosthodont Jun 16. [Epub ahead of print.].

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PURPOSE: To review the primary additive manufacturing (AM) technologies used to fabricate metals in implant dentistry and compare them to conventional casting and subtractive methods. METHODS: The literature on metal AM technologies was reviewed, and the AM procedures and their current applications in implant dentistry were collated and described. Collection of published articles about metal AM in dental field data sources: MEDLINE, EMBASE, EBSCO, and Web of Science searched. All studies related to AM technology description, analysis, and evaluation of applications in implant dentistry, including AM titanium (Ti) dental implants, customized Ti mesh for bone grafting techniques, cobalt-chromium (Co-Cr) frameworks for implant impression procedures, and Co-Cr and Ti frameworks for dental implant-supported prostheses were reviewed. RESULTS: Literature has demonstrated the potential of AM technologies to fabricate dental implants, root-analog implants, and functionally graded implants; as well as the ability to fabricate customized meshes for bone grafting procedures. Metal AM technologies provide a reliable method to manufacture frameworks for implant impression procedures. Co-Cr and Ti AM frameworks for implant-supported prostheses provide a clinically acceptable discrepancy at the implant-prostheses interface. CONCLUSIONS: Additional clinical studies are required to assess the long-term clinical performance, biological and mechanical complications, and prosthetic restoration capabilities of additively manufactured dental implants. Moreover, further studies are needed to evaluate their long-term success and survival rates and biological and mechanical complications of AM implant-supported prostheses.

Revilla-León, M., S. G. Subramanian, M. Özcan and V. R. Krishnamurthy (2020). “Clinical Study of the Influence of Ambient Lighting Conditions on the Mesh Quality of an Intraoral Scanner.” J Prosthodont May 28. [Epub ahead of print.].

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PURPOSE: To compute the effect of ambient light illuminance settings on the mesh quality of the digital scans accomplished in a subject. MATERIAL AND METHODS: A subject was recruited. The maxillary dentition did not present any dental restoration. A prosthodontist recorded different complete-arch maxillary digital scans by using an IOS (TRIOS 3; 3Shape) under 4 different illuminance light conditions namely chair light at 10 000-lux illuminance (CL group), room light at 1000-lux illuminance (RL group), natural light at 500-lux illuminance (NL group), and no light at 0-lux luminosity (ZL group). Ten digital scans for each group were consecutively obtained. Mesh quality was examined using the iso2mesh MATLAB package. Shapiro-Wilk test revealed a non-normally distributed data. Kruskal-Wallis one-way ANOVA, and pair-wise comparison were selected to evaluate the data (α = .05). RESULTS: Significant differences in mesh quality values were measured among the groups (P<.001). Pair-wise comparisons revealed that significant difference was found across all pairs of lighting groups, except for the RL-NL comparison (P = .279). However, the CL condition obtained the highest mean values, followed by RL and NL groups, and the lowest mean values were obtained on the ZL lighting condition. CONCLUSIONS: Chair light at 10 000-lux illuminance condition is recommended to maximize the quality mesh values of the IOS system tested (TRIOS 3; 3Shape).

Revilla-León, M., Z. Smith, M. M. Methani, A. Zandinejad and M. Özcan (2020). “Influence of scan body design on accuracy of the implant position as transferred to a virtual definitive implant cast.” J Prosthet Dent May 31;S0022-3913(20)30237-7. [Epub ahead of print.].

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STATEMENT OF PROBLEM: Previous studies have analyzed factors influencing intraoral scanner accuracy; however, how the intraoral scan body design affects the implant position on the virtual definitive cast is unclear. PURPOSE: The purpose of this in vitro study was to measure the discrepancies of the implant replica positions of the virtual definitive implant cast obtained by using 3 different scan body designs when performing a digital scan. MATERIAL AND METHODS: A partially edentulous typodont with 3 implant replicas (Implant Replica RP Branemark system; Nobel Biocare Services AG) was prepared. Three groups were determined based on the scan body system evaluated: SB-1 (Elos Accurate Nobel Biocare), SB-2 (NT Digital Implant Technology), and SB-3 (Dynamic Abutment). Each scan body was positioned on each implant replica of the typodont, and was digitized by using an intraoral scanner (iTero Element; Cadent) as per the manufacturer’s scanning protocol at 1000 lux illuminance. A standard tessellation language (STL) file was obtained. Before the scan bodies were removed from the typodont, a coordinate measuring machine (CMM Contura G2 10/16/06 RDS; Carl Zeiss Industrielle Messtechnik GmbH) was used to measure the scan body positions on the x-, y-, and z-axis. The linear and angular discrepancies between the position of the scan bodies on the typodont and STL file were calculated by using the best fit technique with a specific program (Calypso; Carl Zeiss Industrielle Messtechnik GmbH). The procedure was repeated until 10 STL files were obtained per group. The Shapiro-Wilk test revealed that the data were not normally distributed. The data were analyzed by using the Mann-Whitney U test (α=.05). RESULTS: The coordinate measuring machine was unable to measure the scan body positions of the magnetically retained SB-3 group because of its mobility when palpating at the smallest pressure possible. Therefore, this group was excluded. No significant differences were found in the linear discrepancies between the SB-1 and SB-2 groups (P>.05). The most accurate scan body position was obtained on the z-axis. However, the SB-1 group revealed a significantly higher XZ angular discrepancy than the SB-2 group (P<.001). CONCLUSIONS: The scan body systems tested (SB-1 and SB-2 groups) accurately transferred the linear implant positions to the virtual definitive implant cast. However, significant differences were observed in the XZ angular implant positions between the scan body systems analyzed.

Revilla-León, M., J. L. Sánchez-Rubio, J. Pérez-López, J. Rubenstein and M. Özcan (2020). “Discrepancy at the implant abutment-prosthesis interface of complete-arch cobalt-chromium implant frameworks fabricated by additive and subtractive technologies before and after ceramic veneering.” J Prosthet Dent May 24;S0022-3913(20)30236-5. [Epub ahead of print.].

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STATEMENT OF PROBLEM: Selective laser melting additive manufacturing (AM) technologies can be used to fabricate complete-arch cobalt-chromium (Co-Cr) implant-supported prostheses. However, the discrepancy at the implant-prosthesis interface with these fabrication techniques and after ceramic veneering remains unclear. PURPOSE: The purpose of the present in vitro investigation was to measure the discrepancy at the implant abutment-prosthesis interface before and after the ceramic veneering of frameworks fabricated by using subtractive and selective laser melting AM technologies. MATERIAL AND METHODS: A completely edentulous cast with 6 implant abutment replicas (Multi-unit Abutment RP Replicas; Nobel Biocare Services AG) was prepared. A total of 20 Co-Cr frameworks were fabricated using subtractive or computer numerical control milling (CNC group) and additive (AM group) technologies (n=10). A coordinate measurement machine was used to measure the linear and angular discrepancy at the implant abutment-prosthesis interface. Subsequently, a ceramic veneer was applied to each framework following the same standardized protocol. A bonding layer (Chromium-Cobalt Bonding; Bredent), 2 opaquer layers (Powder opaque and liquid UF; Creation CC), a layer of dentin ceramic (Dentine A3; Creation CC), a layer of enamel ceramic (Enamel S-59; Creation CC), and a glaze layer (Glaze paste and Liquid GL; Creation CC) were applied following the manufacturer’s firing protocol. Coordinate measurement machine assessment was repeated to measure the linear and angular discrepancies after ceramic veneering procedures. Data were analyzed by using the Wilcoxon signedrank and Mann-Whitney U tests (α=.05). RESULTS: No statistically significant differences (P>.05) were demonstrated in assessing the discrepancies at the implant abutment-prosthesis interface between the groups except for the XZ angle of the CNC group (P<.05). Ceramic techniques produced significantly higher linear and angular discrepancies in both groups (P<.001) with a mean ±standard deviation increase in the 3-dimensional gap of 36.9 ±15.6 μm in the CNC group and 38.9 ±16.6 μm in the AM group. The AM group presented significantly higher discrepancy in the x-axis than the CNC group (P<.001). CONCLUSIONS: Manufacturing procedures did not significantly influence the discrepancy at the implant abutment-prosthesis interface, which was significantly increased after ceramic veneering, except for the XZ angle of the CNC group. The differences between the discrepancies at the implant abutment-prosthesis interface before and after ceramic application revealed no significant discrepancies among the groups, except in the AM group that presented a significantly higher discrepancy on the x-axis compared with the CNC group.

Revilla-Leon, M., D. Jordan, M. M. Methani, W. Piedra-Cascon, M. Ozcan and A. Zandinejad (2020). “Influence of printing angulation on the surface roughness of additive manufactured clear silicone indices: An in vitro study.” J Prosthet Dent Apr 22;S0022-3913(20)30143-8. [Epub ahead of print].

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STATEMENT OF PROBLEM: Vat-polymerization additive manufacturing (AM) technologies can be used to fabricate clear silicone indices for diagnostic trial restorations, interim restorations, and direct composite resin restorations. Different support parameters, including print orientation of the virtual design of the silicone index, need to be determined when a dental device is fabricated with AM. However, the optimal printing angulation for minimal surface texture remains unclear. PURPOSE: The purpose of this in vitro study was to measure the surface roughness of the AM clear silicone indices manufactured by using a vat-polymerization 3D printer with different print orientations. MATERIAL AND METHODS: A virtual design of a facial silicone index was obtained, and the standard tessellation language file was exported and used to manufacture all the specimens using a vat-polymerization 3D printer. All the specimens were placed on the build platform with the same parameters, except for the print orientation which was selected as the only manufacturing variable. Therefore, the 5 different groups were 0, 25, 45, 75, and 90 degrees. To minimize variation in the procedure, all the specimens (N=50) were manufactured at the same time in the selected printer at a constant room temperature of 23 degrees C. The printer had been previously calibrated following the manufacturer’s recommendations. Surface roughness was measured in the intaglio of the left central maxillary incisor using an optical profilometer with a magnification of x20 and an array size of 640×480. Three measurements per specimen were recorded. The Shapiro-Wilk test revealed that the data were normally distributed, and the data were analyzed by using 1-way ANOVA, followed by the post hoc Sidak test (alpha=.05). RESULTS: The 0-degree angulation printing group reported the least mean +/-standard deviation surface roughness (0.9 +/-0.3 mum), followed by the 90-degree group (3.0 +/-0.6 mum), the 75-degree group (12.4 +/-1.0 mum), the 25-degree group (13.1 +/-0.9 mum), and the 45-degree group (13.5 +/-1.0 mum). However, no statistically significant difference was found in the surface roughness between the 25-degree and 45-degree print orientation groups (P=.296). CONCLUSIONS: Print orientation significantly influenced the surface roughness measured on the intaglio of the facial AM silicone indices tested.