Research Spotlight

McAdams-DeMarco, M. A., S. E. Van Pilsum Rasmussen, N. M. Chu, D. Agoons, R. F. Parsons, T. Alhamad, K. L. Johansen, S. G. Tullius, R. Lynch, M. N. Harhay, M. K. Rao, J. Berger, M. Cooper, J. C. Tan, X. S. Cheng, K. J. Woodside, S. Parajuli, K. L. Lentine, B. Kaplan, D. L. Segev, J. A. Kobashigawa and D. Dadhania (2020). “Perceptions and Practices Regarding Frailty in Kidney Transplantation: Results of a National Survey.” Transplantation 104(2): 349-356.

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BACKGROUND: Given the potential utility of frailty, a clinical phenotype of decreased physiologic reserve and resistance to stressors, to predict postkidney transplant (KT) outcomes, we sought to understand the perceptions and practices regarding frailty measurement in US KT programs. METHODS: Surveys were emailed to American Society of Transplantation Kidney/Pancreas Community of Practice members and 202 US transplant programs (November 2017 to April 2018). Program characteristics were gleaned from Scientific Registry of Transplant Recipients. RESULTS: The 133 responding programs (response rate = 66%) represented 77% of adult KTs and 79% of adult KT candidates in the United States. Respondents considered frailty to be a useful concept in evaluating candidacy (99%) and endorsed a need to develop a frailty measurement specific to KT (92%). Frailty measurement was more common during candidacy evaluation (69%) than during KT admission (28%). Of the 202 programs, 38% performed frailty assessments in all candidates while 23% performed assessments only for older candidates. There was heterogeneity in the frailty assessment method; 18 different tools were utilized to measure frailty. The most common tool was a timed walk test (19%); 67% reported performing >1 tool. Among programs that measure frailty, 53% reported being less likely to list frail patients for KT. CONCLUSIONS: Among US KT programs, frailty is recognized as a clinically relevant construct and is commonly measured at evaluation. However, there is considerable heterogeneity in the tools used to measure frailty. Efforts to identify optimal measurement of frailty using either an existing or a novel tool and subsequent standardization of its measurement and application across KT programs should be considered.

Tong, Z., Silo-Suh, L. A., Kalalah, A., Dawson, P., Chin, B. A. and Suh, S. J. (2020). “Efficient affinity-tagging of M13 phage capsid protein IX for immobilization of protein III-displayed oligopeptide probes on abiotic platforms.” Appl Microbiol Biotechnol 104(3): 1201-1209.

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We developed a genetic approach to efficiently add an affinity tag to every copy of protein IX (pIX) of M13 filamentous bacteriophage in a population. Affinity-tagged phages can be immobilized on a surface in a uniform monolayer in order to position the pIII-displayed peptides or proteins for optimal interaction with ligands. The tagging consists of two major steps. First, gene IX (gIX) of M13 phage is mutated in Escherichia coli via genetic recombineering with the gIX::aacCI insertion allele. Second, a plasmid that co-produces the affinity-tagged pIX and native pVIII is transformed into the strain carrying the defective M13 gIX. This genetic complementation allows the formation of infective phage particles that carry a full complement (five copies per virion) of the affinity-tagged pIX. To demonstrate the efficacy of our method, we tagged a M13 derivative phage, M13KE, with Strep-tag II. In order to tag pIX with Strep-tag II, the phage genes for pIX and pVIII were cloned and expressed from pASG-IBA4 which contains the E. coli OmpA signal sequence and Strep-Tag II under control of the tetracycline promoter/operator system. We achieved the maximum phage production of 3 x 10(11) pfu/ml when Strep-Tag II-pIX-pVIII fusion was induced with 10 ng/ml of anhydrotetracycline. The complete process of affinity tagging a phage probe takes less than 5 days and can be utilized to tag any M13 or fd pIII-displayed oligopeptide probes to improve their performance.

Revilla-Leon, M., Methani, M. M., Morton, D. and Zandinejad, A. (2020). “Internal and marginal discrepancies associated with stereolithography (SLA) additively manufactured zirconia crowns.” J Prosthet Dent Jan 21. [Epub ahead of print].

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STATEMENT OF PROBLEM: Stereolithography (SLA) additive manufacturing (AM) technologies can be selected to fabricate zirconia crowns; however, the internal and marginal discrepancies associated with these new technologies remain unclear. PURPOSE: The purpose of this in vitro study was to measure and compare the marginal and internal discrepancies of milled and AM zirconia crowns by using the silicone replica technique. MATERIAL AND METHODS: An implant custom abutment was manufactured and scanned by using a laboratory scanner (CARES Software; Straumann). An anatomic contour crown was digitally designed, and the standard tessellation language (STLC) file was obtained. The STLC file was splinted into 2 pieces, simulating the parts of the crown that would replace the enamel (STLG1 file) and dentin (STLG2 file) structures. Three groups were determined: anatomic contour zirconia milled (CNC group), AM anatomic contour zirconia (AM group), and AM splinted zirconia (SAM group). For the CNC group, the STLC file was used to manufacture milled (CARES zirconium-dioxide crown; Straumann) zirconia specimens. For the AM group, the STLC file was used to additively fabricate (CERAMAKER 900; 3DCeram Co) the zirconia (3DMix ZrO2 paste; 3DCeram Co) specimens. For the SAM group, the STLG2 file was selected to AM (CERAMAKER 900; 3DCeram Co) the zirconia (3DMix ZrO2 paste; 3DCeram Co) specimens. Ten specimens per group were manufactured. The silicone replica technique was used to measure the marginal and internal discrepancies. The cement gap was measured on images captured by using a digital microscope at x100 magnification. For the internal gap, 50 measurements were made for each specimen, and for the marginal gap, 25 measurements were made for each specimen. The normality test, Shapiro-Wilk test, was conducted. The results indicated that the distributions were not normal; therefore, nonparametric Kruskal-Wallis H and pairwise Mann-Whitney U-tests were used to analyze the data. The Spearman correlation coefficient was used to determine the correlation between marginal and internal discrepancies in all 3 groups. RESULTS: Significant differences were found in marginal and internal discrepancies among the groups. The CNC group had the least marginal and internal discrepancies compared with the AM and SAM groups. The SAM group had significantly lower values for marginal and internal discrepancies than the AM group. The AM group showed the highest marginal and internal discrepancies. The CNC group had a weak correlation coefficient of 0.13 (P=.046), the AM group had a moderate correlation coefficient of 0.32 (P<.001), and the SAM group had a nonsignificant correlation coefficient of 0.12 (P=.051). CONCLUSIONS: CNC and SAM groups had clinically acceptable marginal and internal discrepancies, while the AM group had a clinically unacceptable marginal and internal crown discrepancies. Furthermore, a weak correlation was encountered between the marginal and internal discrepancies measured in all groups.

Revilla-Leon, M., Campbell, H. E., Meyer, M. J., Umorin, M., Sones, A. and Zandinejad, A. (2020). “Esthetic dental perception comparisons between 2D- and 3D-simulated dental discrepancies.” J Prosthet Dent Jan 22. [Epub ahead of print].

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STATEMENT OF PROBLEM: Intraoral scanners (IOSs), facial scanners (FSs), and computer-aided design (CAD) software programs have become powerful tools for treatment planning. However, discrepancies in perception regarding 2-dimensional (2D) or 3-dimensional (3D) simulations by dentists, dental students, and laypeople have not been analyzed. PURPOSE: The purpose of this observational study was to analyze the perceptions of laypersons, dental students, and dentists regarding disparities of the maxillary dental midline and the occlusal plane when analyzing the dental discrepancies on 2D- and 3D-clinical simulations. MATERIAL AND METHODS: A female model was digitized by using an FS, IOS, and a full-face smile photograph. Dental discrepancies were simulated by using a 2D photograph (2D group) and 3D scan (3D group) of the model. In both simulation groups, 2 subgroups were produced. The occlusal plane of the first subgroup was modified in 1-degree increments without changing the dental midline or the position of the maxillary dental incisors. In the second subgroup, the occlusal plane was modified by using the same increments, but the maxillary central incisors and dental midline were altered to match the inclination of the occlusal plane. A total of 300 participants (N=300) were asked to rate the 2D images (N=12) and 3D videos (N=12) on a 1-to-6 scale and answer a questionnaire. Ordinal logistic regression was used to analyze the ratings. RESULTS: The ratings decreased with the increased tilt of the occlusal plane, and the layperson group gave consistently higher ratings than the other 2 groups. For dentists, the odds of giving a higher versus lower rating decreased by almost a half for each degree of tilt. However, for students, that effect was diminished by a positive interaction term, and for laypersons, the effect was even less. Students gave similar ratings to dentists, but laypersons gave higher ratings. As the age of the participants increased, however, the ratings also increased. The use of 3D versus 2D images had a positive effect on the ratings, but the effect decreased for the student observers and decreased even further for laypersons. Furthermore, midline alteration led to higher ratings but also resulted in worsening of the odds ratio for the tilt. Seventy percent of the dentists, 57% of the dental students, and 52% of the laypersons preferred 2D simulations to 3D simulations. CONCLUSIONS: Dentists, dental students, and laypersons decreased their ratings with increased inclination of the occlusal plane; however, laypersons still graded all the 2D and 3D images as esthetically pleasant, giving consistently higher ratings than the dentists and dental students. Overall, 3D simulations obtained higher ratings than 2D images, but the positive effect decreased for the student observers and decreased even further for laypersons.

Piedra-Cascon, W., Meyer, M. J., Methani, M. M. and Revilla-Leon, M. (2020). “Accuracy (trueness and precision) of a dual-structured light facial scanner and interexaminer reliability.” J Prosthet Dent Jan 6. [Epub ahead of print].

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STATEMENT OF PROBLEM: Digital waxing procedures should be guided by facial references to improve the esthetic outcome of a restoration. The development of facial scanners has allowed the digitalization of the extraoral soft tissues of the patient’s face. However, the reliability of facial digitizers is questionable. PURPOSE: The purpose of this study was to evaluate the accuracy (trueness and precision) of extraoral 3D facial reconstructions performed by using a dual-structured light facial scanner and to measure the interexaminer variability. MATERIAL AND METHODS: Ten participants were included. Six soft-tissue landmarks were determined on each participant, specifically reference (Ref), glabella (Gb), subnasal (Sn), menton (Me), chelion right (ChR), and chelion left (ChL). Interlandmark distances Ref-Sn, Sn-Gb, Ref-Gb, Sn-Me, and ChR-ChL (intercommissural) were measured by 2 different operators by using 2 different methods: directly on the participant’ face (manual group) and digitally (digital group) on the 3D facial reconstruction of the participant (n=20). For the manual group, interlandmark measurements were made by using digital calipers. For the digital group, 10 three-dimensional facial reconstructions were acquired for each participant by using a dual-structured light facial scanner (Face Camera Pro Bellus; Bellus3D). Interlandmark measurements were made by using an open-source software program (Meshlab; Meshlab). Both operators were used to note 10 measurements for each manual and digital interlandmark distance per participant. The intraclass correlation coefficient between the 2 operators was calculated. The Shapiro-Wilk test revealed that the data were not normally distributed. The data were analyzed by using the Mann-Whitney U test. RESULTS: Significant differences were found between manual and digital interlandmark measurements in all participants. The mean value of the manual and digital group discrepancy was 0.91 +/-0.32 mm. The dual-structured light facial scanner tested obtained a trueness mean value of 0.91 mm and a precision mean value of 0.32 mm. Trueness values were always higher than precision mean values, indicating that precision was relatively high. The intraclass correlation coefficient between the 2 operators was 0.99. CONCLUSIONS: The facial digitizing procedure evaluated produced clinically acceptable outcomes for virtual treatment planning. The interexaminer reliability between the 2 operators was rated as excellent, suggesting that the type of facial landmark used in this study provides reproducible results among different examiners.