Marta Revilla Leon M.S.D.

Revilla-Leon, M., R. Fogarty, J. J. Barrington, A. Zandinejad and M. Ozcan (2019). “Influence of scan body design and digital implant analogs on implant replica position in additively manufactured casts.” J Prosthet Dent Nov 28. pii: S0022-3913(19)30487-1. [Epub ahead of print].

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STATEMENT OF PROBLEM: Additive manufacturing (AM) technologies can be used to fabricate definitive casts for implant-supported restorations. However, information regarding the accuracy of the implant replica position on the polymeric AM cast generated with different scan bodies and digital implant replica systems is lacking. PURPOSE: The purpose of this in vitro study was to compare with a conventional stone cast the linear and angular discrepancies of the implant analog positions in a polymeric AM cast obtained from 3 different scan body and digital implant replica systems. MATERIAL AND METHODS: A partially edentulous maxillary typodont with 3 implant replicas (Implant replica RP Branemark system; Nobel Biocare) was prepared. Two duplicating methods were evaluated: conventional (CNV group) and AM (AM group) procedures. For the CNV group, polyvinyl siloxane open-tray implant impressions (CNV) were made at room temperature (23 degrees C). The AM group was further divided into the subgroups Elos Medtech, Nt-Trading, and Dynamic Abutment. For the Elos Medtech subgroup, the corresponding scan bodies were placed on each implant, and the typodont was digitized by using a laboratory scanner (E3 scanner; 3Shape). The same procedure was repeated with the remaining subgroups. All the AM polymer casts were fabricated at once by using the same 3D printer (Eden 500V; Stratasys). Ten specimens of each group were obtained (n=10). A coordinate-measuring machine (CMM) was used to measure the position of each implant replica, and distortion was calculated for each system at the x-, y-, and z-axes and 3D distortion measurement (3D=x(2)+y(2)+z(2)). The Shapiro-Wilk test revealed that the data were not normally distributed. The Kruskal-Wallis and pairwise Mann-Whitney U tests (alpha=.05) were used for the analysis. RESULTS: The CNV group presented significantly higher linear discrepancy than the Dynamic Abutment group on the x- and y-axes. On the z-axis, however, the CNV group showed significantly lower linear discrepancy than the Nt-Trading and Dynamic Abutment groups. The 3D linear discrepancy was 12 +/-12 mum for the CNV group, 4 +/-100 mum for the Elos Medtech group, 8 +/-52 mum for the Nt-Trading group, and 5 +/-19 mum for the Dynamic Abutment. The CNV group demonstrated a significantly higher angle than the Nt-Trading group but a significantly smaller angle than the Elos Medtech and Dynamic Abutment groups. CONCLUSIONS: The AM groups had lower 3D discrepancies than the CNV group. The Dynamic Abutment group had significantly better accuracy for the mesiodistal and buccolingual implant replica positions than the CNV group, but the conventional procedures had significantly better results for the apicocoronal implant replica position. Scan body and digital implant replica design systems only influenced the accuracy of the angular implant replica position on the AM casts.

Methani, M. M., M. Revilla-Leon and A. Zandinejad (2019). “The potential of additive manufacturing technologies and their processing parameters for the fabrication of all-ceramic crowns: A review.” J Esthet Restor Dent Nov 7. [Epub ahead of print].

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OBJECTIVE: This article aims to provide a review of the additive manufacturing technologies and the processing parameters that have been investigated for the fabrication of all ceramic crowns. OVERVIEW: Additive manufacturing has crept its way into the field of dentistry for the fabrication of resin and metal prosthesis. To evaluate the current status of additive manufacturing for the fabrication of all ceramic crowns, literature review was targeted to include publications pertaining to the fabrication of dental ceramics and all ceramic crowns. With respect to the additive manufacturing of dental ceramics, five technologies have been investigated to date: stereolithography, material extrusion, powder based fusion, direct inkjet printing, and binder jetting. The processing parameters and experimental outcomes were collated and described for each of the aforementioned technologies. CONCLUSION: Additive manufacturing has demonstrated promising experimental outcomes and corroborated to the fabrication all ceramic crowns. However, the technology is yet to witness a commercial breakthrough within this domain. CLINICAL SIGNIFICANCE: Additive manufacturing mitigates raw material wastage and tooling stresses that are associated with milling of ceramics. Continued research and development can lead to its approbation as an alternate technology for manufacturing all ceramic restorations.

Revilla-Leon, M., M. Umorin, M. Ozcan and W. Piedra-Cascon (2019). “Color dimensions of additive manufactured interim restorative dental material.” J Prosthet Dent Oct 22. pii: S0022-3913(18)30841-2. [Epub ahead of print].

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STATEMENT OF PROBLEM: Interim dental restorations can be fabricated by using additive manufacturing (AM) technologies. Although dental restoration contours can be easily and accurately fabricated by using computer-aided design (CAD) procedures, protocols for creating predictable color dimensions of AM interim restorations are lacking. PURPOSE: The purpose of this in vitro study was to measure and compare color dimensions of different AM and conventional interim restorative materials. MATERIAL AND METHODS: Disks (N=420) were fabricated by using either conventionally (CNV group) or additively manufactured (AM group) materials. The CNV group was further divided into the subgroups CNV-1 (Protemp 4; 3M ESPE) and CNV-2 (Anaxdent new outline dentin; Anaxdent). AM subgroups included AM-1 (FreePrint temp; Detax), AM-2 (E-Dent 400; Envisiontec), AM-3 (NextDent C&B; NextDent), AM-4 (NextDent C&B MFH; NextDent), and AM-5 (Med620 VEROGlaze; Stratasys). Color measurements in the CIELab coordinates were made by using a spectrophotometer (VITA EasyShade Advance 4.0; VITA) with a standardized photography gray card as a background under room light conditions (1003 lux). Color difference (DeltaE*) values were calculated by using the CIE76 and CIEDE2000 formulas. The data were analyzed by using the Kruskal-Wallis test with nonparametric pairwise comparisons. RESULTS: Owing to a software error, the spectrophotometer was unable to measure the color of any specimens in the AM-5 subgroup, which was consequently excluded from further analysis. Significant differences (P=.001) between 2 manufacturing groups were found based on the L* variable. All subgroups were significantly different from each other for all 3 variables (P<.001). Pairwise comparisons revealed that all groups were significantly different from each other, except for the AM-1 and AM-2 subgroups, compared with the CNV-1 subgroup for the L* color dimension. The DeltaE* values calculated by using the CIE76 formula varied from 6.63 to 23.1 and by using the CIEDE2000 formula from 3.43 to 10.21, suggesting a perceptible and unacceptable color mismatch between the CNV and AM groups. CONCLUSIONS: None of the additively manufactured interim materials tested matched the conventional interim materials in all 3 CIELab color dimensions.

Revilla-Leon, M., M. J. Meyer, J. J. Barrington, A. Sones, M. P. Umorin, M. Taleghani and A. Zandinejad (2019). “Perception of occlusal plane that is nonparallel to interpupillary and commissural lines but with the maxillary dental midline ideally positioned.” J Prosthet Dent 122(5): 482-490.

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STATEMENT OF PROBLEM: How disparities in parallelism between the occlusal plane and the interpupillary (IP) or commissural facial front lines are perceived is unclear. PURPOSE: The purpose of this observational study was to examine the perceptions of laypersons, dental students, and dentists regarding disparities of the anterior occlusal plane (AOP) and posterior occlusal plane (POP) with respect to the IP and commissural line (CL) with the maxillary dental midline ideally positioned. MATERIAL AND METHODS: A model of a symmetric female face was digitally created with the IP and CL parallel and the facial midline coincident with the maxillary dental midline. Two groups of images were created, one with the POP modified in 1-degree increments, in which both the maxillary dental midline and the position of the maxillary central incisors were not manipulated, and the other with the POP modified in the same increments but with the position of both maxillary central incisors lengthened to follow the inclination of the occlusal plane. Participants (N=312) were asked to rate the images on a 1-to-6 scale. The Kruskal-Wallis medians test and ordinal logistic regression were used to analyze the ratings. RESULTS: Group median ratings for different occupations gradually decreased with increased inclination of the occlusal plane. Significant differences were found for inclinations from 2 to 5 degrees. Significant odd ratios were found for age and sex. CONCLUSIONS: Dental professionals detected smaller POP disparities. The dentist and dental student groups gave lower ratings in proportion to the amount of POP inclination. Laypersons gave lower ratings only after 3 degrees of POP inclination but still graded all the images as esthetically pleasant. Older people and men tended to give higher ratings to the same image.