Simulation of tissue-prosthesis margin interface by using surface scanning and digital design for auricular prostheses

Digital workflow for auricular prosthesis fabrication with a negative mold

A prosthesis for a patient with a complete auricle defect can be fabricated with computer-aided design and computer-aided manufacturing, significantly reducing the number of patient visits and improving the efficiency of the production process. This technique provides a digital workflow for designing virtual patterns and negative molds for an auricular prosthesis.

Polymers in 3D printing of external maxillofacial prostheses and in their retention systems

Maxillofacial defects, arising from trauma, oncological disease or congenital abnormalities, detrimentally affect daily life. Prosthetic repair offers the aesthetic and functional reconstruction with the help of materials mimicking natural tissues. 3D polymer printing enables the design of patient-specific prostheses with high structural complexity, as well as rapid and low-cost fabrication on-demand. However, 3D printing for prosthetics is still in the early stage of development and faces various challenges for widespread use. This is because the most suitable polymers for maxillofacial restoration are soft materials that do not have the required printability, mechanical strength of the printed parts, as well as functionality. This review focuses on the challenges and opportunities of 3D printing techniques for production of polymer maxillofacial prostheses using computer-aided design and modeling software. Review discusses the widely used polymers, as well as their blends and composites, which meet the most important assessment criteria, such as the physicochemical, biological, aesthetic properties and processability in 3D printing. In addition, strategies for improving the polymer properties, such as their printability, mechanical strength, and their ability to print multimaterial and architectural structures are highlighted. The current state of the prosthetic retention system is presented with a focus on actively used polymer adhesives and the recently implemented prosthesis-supporting osseointegrated implants, with an emphasis on their creation from 3D-printed polymers. The successful prosthetics is discussed in terms of the specificity of polymer materials at the restoration site. The approaches and technological prospects are also explored through the examples of the nasal, auricle and ocular prostheses, ranging from prototypes to end-use products.

Applications of CAD/CAM Technology for Craniofacial Implants Placement and Manufacturing of Auricular Prostheses-Systematic Review

This systematic review was aimed at gathering the clinical and technical applications of CAD/CAM technology for craniofacial implant placement and processing of auricular prostheses based on clinical cases. According to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, an electronic data search was performed. Human clinical studies utilizing digital planning, designing, and printing systems for craniofacial implant placement and processing of auricular prostheses for prosthetic rehabilitation of auricular defects were included. Following a data search, a total of 36 clinical human studies were included, which were digitally planned and executed through various virtual software to rehabilitate auricular defects. Preoperative data were collected mainly through computed tomography scans (CT scans) (55 cases); meanwhile, the most common laser scanners were the 3dMDface System (3dMD LLC, Atlanta, Georgia, USA) (6 cases) and the 3 Shape scanner (3 Shape, Copenhagen, Denmark) (6 cases). The most common digital design software are Mimics Software (Mimics Innovation Suite, Materialize, Leuven, Belgium) (18 cases), Freeform software (Freeform, NC, USA) (13 cases), and 3 Shape software (3 Shape, Copenhagen, Denmark) (12 cases). Surgical templates were designed and utilized in 35 cases to place 88 craniofacial implants in auricular defect areas. The most common craniofacial implants were Vistafix craniofacial implants (Entific Medical Systems, Goteborg, Sweden) in 22 cases. A surgical navigation system was used to place 20 craniofacial implants in the mastoid bone. Digital applications of CAD/CAM technology include, but are not limited to, study models, mirrored replicas of intact ears, molds, retentive attachments, customized implants, substructures, and silicone prostheses. The included studies demonstrated a predictable clinical outcome, reduced the patient's visits, and completed the prosthetic rehabilitation in reasonable time and at reasonable cost. However, equipment costs and trained technical staff were highlighted as possible limitations to the use of CAD/CAM systems.

Effect of cut-out rescan procedures on the accuracy of an intraoral scanner used for digitizing an ear model: An in vitro study

PURPOSE

The purpose of this study was to evaluate the impact of the rescanning of mesh holes of different diameters on the accuracy of an intraoral scanner (IOS) used to digitize an ear model.

MATERIALS AND METHODS

An ear model was digitized using an intraoral scanner (Medit i500) to obtain a reference mesh. A baseline experimental scan was created by editing a duplicate of the reference mesh using the cut-out tool of the IOS software. Three equal groups were created based on the diameter of the cut-out areas: 2-mm (G1), 5mm (G2), and 8-mm (G3) (n = 15). The cut-out areas were rescanned and a total of 45 digital files were exported. The discrepancy between the reference and the experimental digital scans was measured using the root mean square calculation (RMS). The data were analyzed by a Kruskal-Wallis test followed by a post hoc Dunn's test with Bonferroni correction.

RESULTS

The trueness values ranged from 19.53 to 27.13 μm. There were significant differences in the RMS error values among the groups tested (p<.001) and post hoc multiple comparisons showed significant differences between the G1 and G2 groups (p = .04), G1 and G3 groups (p<.001), and G2 and G3 groups (p = .004). Overall, the precision values ranged from 4.93 to 7.73 μm and significant differences in the RMS values were only found between the G1 and G2 groups (p = .014).

CONCLUSIONS

Mesh hole rescanning affected the scanning accuracy (trueness and precision) of the IOS tested. The larger the diameter of the mesh holes, the less the trueness of the IOS tested. The precision values seemed to be less affected compared with the trueness by the cut-out and rescanning procedures. This article is protected by copyright. All rights reserved.

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.

Digital Workflow in Maxillofacial Prosthodontics—An Update on Defect Data Acquisition, Editing and Design Using Open-Source and Commercial Available Software

Background: A maxillofacial prosthesis, an alternative to surgery for the rehabilitation of patients with facial disabilities (congenital or acquired due to malignant disease or trauma), are meant to replace parts of the face or missing areas of bone and soft tissue and restore oral functions such as swallowing, speech and chewing, with the main goal being to improve the quality of life of the patients. The conventional procedures for maxillofacial prosthesis manufacturing involve several complex steps, are very traumatic for the patient and rely on the skills of the maxillofacial team. Computer-aided design and computer-aided manufacturing have opened a new approach to the fabrication of maxillofacial prostheses. Our review aimed to perform an update on the digital design of a maxillofacial prosthesis, emphasizing the available methods of data acquisition for the extraoral, intraoral and complex defects in the maxillofacial region and assessing the software used for data processing and part design. Methods: A search in the PubMed and Scopus databases was done using the predefined MeSH terms. Results: Partially and complete digital workflows were successfully applied for extraoral and intraoral prosthesis manufacturing. Conclusions: To date, the software and interface used to process and design maxillofacial prostheses are expensive, not typical for this purpose and accessible only to very skilled dental professionals or to computer-aided design (CAD) engineers. As the demand for a digital approach to maxillofacial rehabilitation increases, more support from the software designer or manufacturer will be necessary to create user-friendly and accessible modules similar to those used in dental laboratories.