Simplifying the digital workflow of facial prostheses manufacturing using a three-dimensional (3D) database: setup, development, and aspects of virtual data validation for reproduction

Trueness and precision of skin surface reproduction in digital workflows for facial prosthesis fabrication

STATEMENT OF PROBLEM

How much skin surface details of facial prostheses can be transferred throughout the digital production chain has not been quantified.

PURPOSE

The purpose of this in vitro study was to quantify the amount of skin surface details transferred from the prosthesis virtual design through the prototype printing with various additive manufacturing (AM) methods to the definitive silicone prosthesis with an indirect mold-making approach.

MATERIAL AND METHODS

Twelve test blocks with embossed wrinkles of 0.05 to 0.8 mm and 12 test blocks with applied earlobe skin structures were printed with stereolithography (SLA), direct light processing (DLP), and PolyJet methods (n=4). DLP and SLA prototype specimens were duplicated in wax. All specimens were then transferred into medical-grade silicone. Rz values of the wrinkle test blocks and the root mean square error (RMSE) of the earlobe test blocks were evaluated by laser topography to determine the trueness and precision of each stage.

RESULTS

For the earlobe test blocks, the PolyJet method had superior trueness and precision of the final skin surface reproduction. The SLA method showed the poorest trueness, and the DLP method, the lowest precision. For the wrinkle test blocks, the PolyJet method had the best wrinkle profile reproduction level, followed by DLP and SLA.

CONCLUSIONS

The indirect mold-making approach of facial prostheses manufacturing may be associated with 7% of skin surface profile loss with SLA, up to 20% with DLP, and no detail loss with PolyJet.

A comparison of digital and conventional fabrication techniques for an esthetic maxillofacial prosthesis for the cheek and lip

Maxillofacial prostheses have traditionally been manufactured by pouring silicone into molds. However, the development of computer-aided design and computer-aided manufacturing (CAD-CAM) systems allows the virtual planning, design, and manufacture of maxillofacial prostheses through the direct 3-dimensional printing of silicone. This clinical report describes the digital workflow as an alternative to the conventional method of restoring a large midfacial defect in the right cheek and lip. In addition, the approaches were nonblinded evaluated in relation to outcomes and time efficiency, while marginal adaptation and esthetics, including patient satisfaction, were assessed for both prostheses fabricated. The digital prosthesis had acceptable esthetics and fit with improved patient satisfaction, especially in terms of efficiency, comfort, and speed of the digital workflow.

Accuracy of capturing nasal, orbital, and auricular defects with extra- and intraoral optical scanners and smartphone: An in vitro study

OBJECTIVES

This in vitro study compares the scanning accuracy of various stationary and portable as well as extra- and intraoral devices for capturing oncological defects.

METHODS

A 3D-printed model of a nasal, orbital, and auricular defect, as well as one of an intact auricle, were digitalized (n = 7 per device) with a stationary optical scanner (Pritiface), a portable extraoral optical scanner (Artec Space Spider), two intraoral scanners (Trios 4 and Primescan), and a smartphone (iPhone 11 Pro). For the reference data, the defect models were digitalized using a laboratory scanner (D2000). For quantitative analysis, the root mean square error value for trueness and precision and mean deviations in millimeters were obtained for each defect type. The data were statistically analyzed using two-way ANOVA and Tukey multiple comparison test. For qualitative analysis, a colorimetric map was generated to display the deviation within the defect area and adjacent tissue.

RESULTS

Statistically significant interactions were found in the trueness and precision for defect and scanner type.

CONCLUSION

The Primescan and Artec Space Spider scanners showed the highest accuracy for most defect types. Primescan and Trios 4 failed to capture the orbital defect. The iPhone 11 Pro showed clinically acceptable trueness but inferior precision.

CLINICAL SIGNIFICANCE

The scanning devices may demonstrate varying accuracy, depending on the defect type. A portable extraoral optical scanner is an universal tool for the digitization of oncological defects. Alternatively, an intraoral scanner may be employed in maxillofacial prosthetics with some restrictions. Utilizing a smartphone in maxillofacial rehabilitation should be considered with caution, because it provides inconsistent accuracy.

Bonding strength of 3D printed silicone and titanium retention magnets for maxillofacial prosthetics application

PURPOSE

To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses.

METHODS

The customized titanium retention magnets were embedded in conventional and additively produced silicone blocks without primer application (n = 20) and with two commercially available primers G611 (n = 20) and A304 (n = 20) applied onto the magnet surface. The pull out test was performed in the universal testing machine using 45° and 90° angulation and the pull out strength was measured for each group. Additionally the SEM images of the pulled out magnets' surface were obtained and the amount of residual silicone onto the magnet surface was quantified.

RESULTS

Significantly higher pull out strength values (p < 0.05) were revealed for 90° specimens (0.11 - 0.17 ± 0.01 N/mm²) compared to the 45° group (0.03 ± 0.02 N/mm²). The pull out test with primer revealed no significant differences between the G 611 and A 304 primers in the additive group. However, significantly (p < 0,05) higher values were observed for conventional specimens in the A304 group (1.10 ± 0.21 N/mm²) compared to the G611 group (0.59 ± 0.27 N/mm²).

CONCLUSION

The application of both used primers may be an acceptable technical option for the anchorage of retention titanium magnets in silicone facial prostheses, produced additively in a fully digital workflow.

A simplified CAD/CAM extraoral surgical guide for therapeutic injections

Therapeutic injections into the craniofacial region can be a complex procedure because of the nature of its anatomical structure. This technical note demonstrates a process for creating an extra-oral template to inject therapeutic substances into the temporomandibular joint and the lateral pterygoid muscle. The described process involves merging cone-beam computed tomography data and extra-oral facial scans obtained using a mobile device to establish a correlated data set for virtual planning. Virtual injection points were simulated using existing dental implant planning software to assist clinicians in precisely targeting specific anatomical structures. A template was designed and then 3D printed. The printed template showed adequate surface fit. This innovative process demonstrates a potential new clinical technique. However, further validation and in vivo trials are necessary to assess its full potential.

Three-Dimensional Printed Nasal Prostheses After Oncologic Rhinectomies: Workflow and Patients' Satisfaction

ABSTRACT

Reconstructions after oncologic full-thickness rhinectomies are often deferred from the ablative surgery. Definitive silicone prostheses are usually not used for transitional rehabilitation, and therefore, patients may deal with major facial defects for a long time before reconstruction. The aim was to develop a time- and cost-effective digital workflow to three-dimensional print temporary nasal prostheses and to assess patients' satisfaction. This prospective study enrolled all consecutive patients after full thickness ablative surgery and deferred reconstruction, from May 2018 to October 2019, at a tertiary care academic institution. With a dedicated software, the pre- and postoperative scans were three-dimensional processed to create the prosthesis and they were directly printed in elastic transparent resin. A cross-sectional survey was conducted 4 months after the rehabilitation to assess patients' satisfaction regarding comfort, aesthetics, and security of the retaining system. Seven patients were enrolled and they were all rehabilitated using this workflow. Mean time of design was 2h48 (SD 40 minutes), and mean printing time was 5h18 (SD 1 hour). Mean cost of production was 753 U.S. Dollars (SD 144 U.S. Dollars). Median scores of the visual analog scales were 8 out of 10 for each topic with interquartile range of 4 to 7 for aesthetics, 7 to 9 for comfort, and 7 to 10 for security of the retaining system. It has shown its feasibility in terms of costs and time of production. Patients were satisfied and it can be considered as a mean to help patients to deal with treatment sequelaes before definitive reconstruction.

Stereolithography vs. Direct Light Processing for Rapid Manufacturing of Complete Denture Bases: An In Vitro Accuracy Analysis

The topical literature lacks any comparison between stereolithography (SLA) and direct light processing (DLP) printing methods with regard to the accuracy of complete denture base fabrication, thereby utilizing materials certified for this purpose. In order to investigate this aspect, 15 denture bases were printed with SLA and DLP methods using three build angles: 0°, 45° and 90°. The dentures were digitalized using a laboratory scanner (D2000, 3Shape) and analyzed in analyzing software (Geomagic Control X, 3D systems). Differences between 3D datasets were measured using the root mean square (RMS) value for trueness and precision and mean and maximum deviations were obtained for each denture base. The data were statistically analyzed using two-way ANOVA and Tukey’s multiple comparison test. A heat map was generated to display the locations of the deviations within the intaglio surface. The overall tendency indicated that SLA denture bases had significantly higher trueness for most build angles compared to DLP (p < 0.001). The 90° build angle may provide the best trueness for both SLA and DLP. With regard to precision, statistically significant differences were found in the build angles only. Higher precision was revealed in the DLP angle of 0° in comparison to the 45° and 90° angles.

Osseointegrated implant-retained auricular prosthesis constructed using cone-beam computed tomography and a prosthetically driven digital workflow: a case report

Prosthetically driven workflows using CBCT, digital optical scanning, 3D-printed molds and frameworks, and dental implant component attachments to osseointegrated fixtures can produce anatomically accurate, esthetic, durable silicone ear replacements.

Accuracy Evaluation of a Three-Dimensional Model Generated from Patient-Specific Monocular Video Data for Maxillofacial Prosthetic Rehabilitation: A Pilot Study

PURPOSE

To evaluate if the combination of a monoscopic photogrammetry technique and smartphone-recorded monocular video data could be appropriately applied to maxillofacial prosthesis fabrication.

MATERIALS AND METHODS

Smartphone video and laser scanning data were recorded for five healthy volunteers (24.1 ± 0.7 years). Three-dimensional (3D) facial models were generated using photogrammetry software and a laser scanner. Smartphone-recorded video data were used to generate a photogrammetric 3D model. The videos were recorded at two resolutions: 1080 × 1920 (high resolution) and 720 × 1280 pixels (low resolution). The lengths of five nasal component parts (nose height, nasal dorsum length, nasal column length, nasal ala length, and nose breadth) were compared in the photogrammetric 3D models (as the test model) and the laser scanned 3D models (as the validation model) using reverse engineering software.

RESULTS

There was a significant difference in the nasal dorsum length between the test model and the validation model (high resolution; 95% confidence interval, 2.05-5.07, Low resolution; confidence interval, 2.19-5.69). In contrast to the nasal dorsum length, there were no significant differences in nose height, nose breadth, nasal ala length, and nasal column length.

CONCLUSION

Using smartphone-recorded video data and a photogrammetry technique may be a promising technique to apply in the maxillofacial prosthetic rehabilitation workflow.

Multimaterial 3D printing of a definitive silicone auricular prosthesis: An improved technique

Direct silicone printing has been reported for the manufacture of interim facial prostheses. The recent advancements in printing hardware have allowed for multimaterial simultaneous silicone printing with 4 nozzles. With this technology, an auricular prosthesis was printed with various grades of Shore hardness. A few analog steps, including polishing, sealing, coloring, and relining, resulted in an individualized prosthesis with a thin frontal margin and smooth transition into the adjacent tissue. It was considered a definitive treatment option.

Implementation of 3D technologies in the workflow of auricular prosthetics: A method using optical scanning and stereolithography 3D printing

The fabrication of auricular prostheses is traditionally time consuming, and the definitive esthetic appearance is highly skill dependent. A method of creating the wax pattern for an auricular prosthesis by using optical scanning and 3D printing is described. A digital scan of the unaffected ear is used for computer-aided design and manufacturing of a mold for casting the wax pattern of the prosthesis. The process is efficient and increases the predictability of the esthetic outcome.