Research Spotlight

Wang, C. I., S. H. Cho, D. Cho, C. Ducote, L. V. Reddy and N. Sinada (2019). “A 3d-Printed Guide to Assist in Sinus Slot Preparation for the Optimization of Zygomatic Implant Axis Trajectory.” J Prosthodont Dec 31. [Epub ahead of print].

Full text of this article.

Zygomatic implants have become a predictable treatment modality for the rehabilitation of the severely atrophic maxilla. Due to differing anatomic variations, proximity to vital anatomic structures and limited intraoperative visibility, the placement of zygomatic implants can be a difficult task; compromised implant positioning may ultimately lead to post-operative surgical and prosthetic complications. The purpose of this report is to demonstrate a technique that allows for the transfer of the sinus slot position. Ultimately, this optimizes zygomatic implant axis trajectory from preoperative prosthetic planning by using cone beam computed tomography (CBCT) and 3-dimensional (3D) planning software to fabricate a stereolithographic 3D-printed surgical guide.

Tong, Z., L. A. Silo-Suh, A. Kalalah, P. Dawson, B. A. Chin and S. J. Suh (2020). “Efficient affinity-tagging of M13 phage capsid protein IX for immobilization of protein III-displayed oligopeptide probes on abiotic platforms.” Appl Microbiol Biotechnol Jan 4. [Epub ahead of print].

Full text of this article.

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., S. G. Subramanian, M. Ozcan and V. R. Krishnamurthy (2019). “Clinical Study of the Influence of Ambient Light Scanning Conditions on the Accuracy (Trueness and Precision) of an Intraoral Scanner.” J Prosthodont Dec 20. [Epub ahead of print].

Full text of this article.

PURPOSE: To quantify the impact of ambient lighting conditions on the accuracy (trueness and precision) of an intraoral scanner (IOS) when maxillary complete-arch and maxillary right quadrant digital scans were performed in a patient. MATERIAL AND METHODS: One complete dentate patient was selected. A complete maxillary arch vinyl polysiloxane impression was obtained and poured using Type IV dental stone. The working cast was digitized using a laboratory scanner (E4 Dental Scanner; 3Shape) and the reference standard tessellation language (STL file) was obtained. Two groups were created based on the extension of the maxillary digital scans performed namely complete-arch (CA group) and right quadrant (RQ) groups. The CA and RQ digital scans of the patient were performed using an IOS (TRIOS 3; 3Shape) with 4 lighting conditions chair light (CL), 10 000 lux, room light (RL), 1003 lux, natural light (NL), 500 lux, and no light (ZL), 0 lux. Ten digital scans per group at each ambient light settings (CL, RL, NL, and ZL) were consecutively obtained (n = 10). The STLR file was used to analyze the discrepancy between the digitized working cast and digital scans using MeshLab software. Kruskal-Wallis, one-way ANOVA, and pair-wise comparison were used to analyze the data. RESULTS: Significant difference in the trueness and precision values were found across different lighting conditions where RL condition obtained the lowest absolute error compared with the other lighting conditions tested followed by CL, NL, and ZL. On the CA group, RL condition also obtained the best accuracy values, CL and NL conditions performed closely and under ZL condition the mean error presented the highest values. On the RQ group, CL condition presented the lowest absolute error when compared with the other lighting conditions evaluated. A pair-wise multicomparison showed no significant difference between NL and ZL conditions. In all groups, the standard deviation was higher than the mean errors from the control mesh, indicating that the relative precision was low. CONCLUSIONS: Light conditions significantly influenced on the scanning accuracy of the IOS evaluated. RL condition obtained the lowest absolute error value of the digital scans performed. The extension of the digital scan was a scanning accuracy influencing factor. The higher the extension of the digital scan performed, the lower the accuracy values obtained. Furthermore, ambient light scanning conditions influenced differently depending on the extension of the digital scans made.

Revilla-Leon, M., P. Jiang, M. Sadeghpour, W. Piedra-Cascon, A. Zandinejad, M. Ozcan and V. R. Krishnamurthy (2019). “Intraoral digital scans: Part 2-influence of ambient scanning light conditions on the mesh quality of different intraoral scanners.” J Prosthet Dent Dec 20. pii: S0022-3913(18)30995-8. [Epub ahead of print].

Full text of this article.

STATEMENT OF PROBLEM: Digital scans should be able to accurately reproduce the different complex geometries of the patient’s mouth. Mesh quality of the digitized mouth is an important factor that influences the capabilities of the geometry reproduction of an intraoral scanner (IOS). However, the mesh quality capabilities of IOSs and the relationship with different ambient light scanning conditions are unclear. PURPOSE: The purpose of this in vitro study was to measure the impact of various light conditions on the mesh quality of different IOSs. MATERIAL AND METHODS: Three IOSs were evaluated-iTero Element, CEREC Omnicam, and TRIOS 3-with 4 lighting conditions-chair light, 10 000 lux; room light, 1003 lux; natural light, 500 lux; and no light, 0 lux. Ten digital scans per group were made of a mandibular typodont. The mesh quality of digital scans was analyzed by using the iso2mesh MATLAB package. Two-way ANOVA and Kruskal-Wallis 1-way ANOVA statistical tests were used to analyze the data (a=.05). RESULTS: Significant differences in mesh quality values were found among the different IOSs under the same lighting conditions and among the different lighting conditions using the same IOS. TRIOS 3 showed the highest consistency and mesh quality mean values across all scanning lighting conditions tested. CEREC Omnicam had the lowest mean mesh quality values across all scanning lighting conditions. iTero Element displayed some consistency in the mesh quality values depending on the scanning lighting conditions: chair light and room light conditions presented good consistency in mesh quality, indicating better mesh quality, and natural light and no light conditions displayed differing consistency in mesh quality values. Nevertheless, no light condition led to the minimal mean mesh quality across all IOS groups. CONCLUSIONS: Differences in the mesh quality between different IOSs should be expected. The photographic scanning techniques evaluated presented higher mesh quality mean values than the video-based scanning technology tested. Moreover, changes in lighting condition significantly affect mesh quality. TRIOS 3 showed the highest consistency in terms of the mean mesh quality, indicating better photographic system in comparison with iTero Element.

Revilla-Leon, M., P. Jiang, M. Sadeghpour, W. Piedra-Cascon, A. Zandinejad, M. Ozcan and V. R. Krishnamurthy (2019). “Intraoral digital scans-Part 1: Influence of ambient scanning light conditions on the accuracy (trueness and precision) of different intraoral scanners.” J Prosthet Dent Dec 18. pii: S0022-3913(18)30992-2. [Epub ahead of print].

Full text of this article.

STATEMENT OF PROBLEM: Digital scans have increasingly become an alternative to conventional impressions. Although previous studies have analyzed the accuracy of the available intraoral scanners (IOSs), the effect of the light scanning conditions on the accuracy of those IOS systems remains unclear. PURPOSE: The purpose of this in vitro study was to measure the impact of lighting conditions on the accuracy (trueness and precision) of different IOSs. MATERIAL AND METHODS: A typodont was digitized by using an extraoral scanner (L2i; Imetric) to obtain a reference standard tessellation language (STL) file. Three IOSs were evaluated-iTero Element, CEREC Omnicam, and TRIOS 3-with 4 lighting conditions-chair light 10 000 lux, room light 1003 lux, natural light 500 lux, and no light 0 lux. Ten digital scans per group were recorded. The STL file was used as a reference to measure the discrepancy between the digitized typodont and digital scans by using the MeshLab software. The Kruskal-Wallis, 1-way ANOVA, and pairwise comparison were used to analyze the data. RESULTS: Significant differences for trueness and precision mean values were observed across different IOSs tested with the same lighting conditions and across different lighting conditions for a given IOS. In all groups, precision mean values were higher than their trueness values, indicating low relative precision. CONCLUSIONS: Ambient lighting conditions influenced the accuracy (trueness and precision) of the IOSs tested. The recommended lighting conditions depend on the IOS selected. For iTero Element, chair and room light conditions resulted in better accuracy mean values. For CEREC Omnicam, zero light resulted in better accuracy, and for TRIOS 3, room light resulted in better accuracy.