Development of a 3D printable maxillofacial silicone: Part I. Optimization of polydimethylsiloxane chains and cross-linker concentration

Effect of Thixotropic Agent on the Color Stability of Platinum-Based Silicone Maxillofacial Elastomers after Artificial Aging

Maxillofacial prostheses are essential for restoring natural appearance and function in individuals with defects in the head and neck regions. Thixotropic agents, as liquid additives, are known to increase the viscosity of silicone elastomers. However, color deterioration remains a challenge in facial prostheses, leading to the need for refabrication. Despite this, there is limited research on the effect of thixotropic agents on the color stability of silicone maxillofacial elastomers. This study aims to investigate the impact of different thixotropic agent amounts on the color degradation of various maxillofacial silicone elastomers. Three elastomers (A-2000, A-2006, and A-2186) were combined with five pigments (no pigment as control, red, yellow, blue, and a mixture of red, yellow, and blue), and mixed with six thixotropic agent quantities (0, 1, 2, 3, 4, and 5 drops). A total of 450 specimens were fabricated (n = 5) and aged in an artificial aging chamber. L*, a*, b* readings were obtained before and after aging using a digital spectrophotometer. Color difference (ΔE*) means and standard deviations for 150 kj/m2, 300 kj/m2, and 450 kj/m2 were calculated. Statistical analyses, including four-way ANOVA and Fisher's PLSD test, were conducted to determine any significant differences (p < 0.05) among the groups. A comprehensive analysis revealed significant four-way interactions among the groups. In the mixed-pigmentation group, adding 4 drops of thixotropic agent resulted in ΔE* above 3 only in A-2186 silicone at 300 and 450 kj/m2 energy levels. However, the color stability of mixed-pigmented A-2000 and A-2006 remained within the acceptable thresholds of 3 ΔE* at all irradiance levels in this study. At each energy level, A-2006 exhibited the highest color stability with an increasing thixotropic agent quantity among all the silicones. Conversely, A-2186 was more affected by the increased number of thixotropic agent drops in each pigmentation group, including the control group at 450 kj/m2. The quantity of thixotropic agent plays a crucial role in determining the color stability of different silicone elastomers pigmented with various intrinsic pigments. The thixotropic agent amount has a more significant impact on color stability than the type of pigment used in the silicone elastomers. A key overarching insight from this investigation is the identification of a safety threshold for the thixotropic agent quantity of 3 drops for each silicone type, pigmentation, and energy level. These findings highlight the importance of considering the proper combination of thixotropic agents, pigments, and silicone materials to achieve optimal color stability in maxillofacial prosthetic applications.

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.

Viscoelastic Properties of Human Facial Skin and Comparisons with Facial Prosthetic Elastomers

Prosthesis discomfort and a lack of skin-like quality is a source of patient dissatisfaction with facial prostheses. To engineer skin-like replacements, knowledge of the differences between facial skin properties and those for prosthetic materials is essential. This project measured six viscoelastic properties (percent laxity, stiffness, elastic deformation, creep, absorbed energy, and percent elasticity) at six facial locations with a suction device in a human adult population equally stratified for age, sex, and race. The same properties were measured for eight facial prosthetic elastomers currently available for clinical usage. The results showed that the prosthetic materials were 1.8 to 6.4 times higher in stiffness, 2 to 4 times lower in absorbed energy, and 2.75 to 9 times lower in viscous creep than facial skin (p < 0.001). Clustering analyses determined that facial skin properties fell into three groups-those associated with body of ear, cheek, and remaining locations. This provides baseline information for designing future replacements for missing facial tissues.

Evaluation of additive manufacturing processes in the production of oculo-palpebral prosthesis

Background: Prosthetic restorations are made to adapt or attach missing human parts in order to restore function and appearance. Maxillofacial defects connote a greater impact on patients, since the face cannot be concealed, and all the senses of the human body are expressed in it. Therefore, in order to restore the patient's quality of life, they are the ones that require the best possible adaptation to the characteristics of the patients. Methods: For the maxillofacial prostheses to fit patients, they must be personalized for each patient. The NGO "Mais Identidade" is a multidisciplinary team that specializes in the rehabilitation of patients with maxillofacial trauma. They use digital manufacturing as a tool to manufacture personalized maxillofacial prostheses for patients. With the help of the NGO, the following research is conducted with the purpose of evaluating different methods of additive manufacturing, 3D printing, in order to select the equipment that suits the needs of the method used in the manufacture of maxillofacial prostheses. To this end, eyelid models will be manufactured in different additive manufacturing equipment, and these will be evaluated according to their economic, physical, and aesthetic characteristics.

[Manufacture of facial prosthesis by three-dimensional printing]

The objective of the literature review was to study and analyze literature sources on the methods and means of facial prosthesis manufacture by three-dimensional printing.

MATERIALS AND METHODS

An analysis of information sources covering the last 15 years was carried out, in search sources as PubMed, Elsiver and eLIBRARY and on the website of the Federal Institute of Industrial Property.

RESULTS

The technology of direct production of prostheses by volumetric printing from silicone materials is the object of research for its development. Most of the materials used for the manufacture of facial prostheses using 3D printing need technical improvements, often requiring expensive equipment, which in turn does not allow the method of manufacturing face prostheses by direct method in everyday clinical practice.

CONCLUSION

Based on the obtained data there is a need to develop a new structural material for the manufacture of facial prostheses by 3D printing using laser stereolithography and digital LED projection technologies.

Present and future of extraoral maxillofacial prosthodontics: Cancer rehabilitation

Historically, facial prosthetics have successfully rehabilitated individuals with acquired or congenital anatomical deficiencies of the face. This history includes extensive efforts in research and development to explore best practices in materials, methods, and artisanal techniques. Presently, extraoral maxillofacial rehabilitation is managed by a multiprofessional team that has evolved with a broadened scope of knowledge, skills, and responsibility. This includes the mandatory integration of different professional specialists to cover the bio-psycho-social needs of the patient, systemic health and pathology surveillance, and advanced restorative techniques, which may include 3D technologies. In addition, recent digital workflows allow us to optimize this multidisciplinary integration and reduce the active time of both patients and clinicians, as well as improve the cost-efficiency of the care system, promoting its access to both patients and health systems. This paper discusses factors that affect extraoral maxillofacial rehabilitation's present and future opportunities from teamwork consolidation, techniques utilizing technology, and health systems opportunities.

Color translation from monoscopic photogrammetry +ID Methodology into a Polyjet final 3D printed facial prosthesis

Background: The artistic techniques necessary to fabricate facial prostheses mainly depend on individual skill and are not a resource easily reproduced. Digital technology has contributed to improved outcomes, often combining analog and new digital techniques in the same workflow. Methods: This article aims to present an innovative workflow to produce a final colored 3D printed and facial prosthesis by UV-map color translation into colored resin 3D printing. A modified +ID Methodology was used to obtain 3D models with the calibrated 3D printable patient's skin color. No hands-on physical molding, manual sculpture, or intrinsic silicone coloration was used. Results: The outcome resulted in acceptable aesthetics, adaptation, and an approximate color match after extrinsic coloration. The patient reported good comfort and acceptance. Conclusions: A direct resin 3D printed prosthesis may be a viable alternative, especially for rapid delivery as an immediate prosthesis or an option when there is no experienced anaplastogist to manufacture a conventional prosthesis.

Are Nano TiO2 Inclusions Improving Biocompatibility of Photocurable Polydimethylsiloxane for Maxillofacial Prosthesis Manufacturing?

(1) Background: The development of a biocompatible material for direct additive manufacturing of maxillofacial extraoral prosthesis is still a challenging task. The aim of the present study was to obtain a photocurable PDMS, with nano TiO2 inclusions, for directly 3D printing of extraoral, maxillofacial prosthesis. The biocompatibility of the newly obtained nanocomposite was also investigated; (2) Methods: 2.5% (m/m) titania nanoparticles (TiO2) oxide anatase and a photoinitiator, benzophenone (BF) 4.5% were added to commercially available PDMS for maxillofacial soft prostheses manufacturing. The three different samples (PDMS, PDMS-BF and PDMS-BF-TiO2) were assessed by dielectric curing analysis (DEA) based on their viscosities and curing times. In vitro micronucleus test (MNvit) was performed for genotoxicity assessment and three concentrations of each compounds (2 mg/L, 4 mg/L and 8 mg/L) were tested in duplicate and compared to a control; (3) Results: The nanocomposite PDMS-BP-TiO2 was fully reticulated within a few minutes under UV radiation, according to the dielectric analysis. PDMS-BF-TiO2 nanocomposite showed the lowest degree of cyto- and genotoxicity; (4) Conclusions: In the limits of the present study, the proposed ex situ preparation of a PDMS-BP-TiO2 offers an easy, simple, and promising technique that could be successfully used for 3D printing medical applications.

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.

Systematic Review of Clinical Applications of CAD/CAM Technology for Craniofacial Implants Placement and Manufacturing of Nasal Prostheses

The aim of this systematic review was to gather the clinical and laboratory applications of CAD/CAM technology for preoperative planning, designing of an attachment system, and manufacturing of nasal prostheses. According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, an electronic search was carried out. Only human clinical studies involving digital planning for the rehabilitation of facial defects were included. A total of 21 studies were included with 23 patients, which were virtually planned through different planning software. The most common preoperative data for digital planning were CT scans in nine cases, CBCT in six cases, and laser scans in six cases. The reported planning softwares were Mimics in six cases, Geomagic Studio software in six cases, ZBrush in four cases, and Freeform plus software in four cases. Ten surgical templates were designed and printed to place 36 implants after digital planning, while post-operative assessment was done in two cases to check the accuracy of planned implants. Digital 3D planning software was reported for presurgical planning and craniofacial implants placement, fabrication of molds, designing of implants, designing of retentive attachments, and printing of silicone prostheses. Digital technology has been claimed to reduce the clinical and laboratory time; however, the equipment cost is still one of the limitations.

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.

Laser-Facilitated Additive Manufacturing Enables Fabrication of Biocompatible Neural Devices

Current personalized treatment of neurological diseases is limited by availability of appropriate manufacturing methods suitable for long term sensors for neural electrical activities in the brain. An additive manufacturing process for polymer-based biocompatible neural sensors for chronic application towards individualized implants is here presented. To process thermal crosslinking polymers, the developed extrusion process enables, in combination with an infrared (IR)-Laser, accelerated curing directly after passing the outlet of the nozzle. As a result, no additional curing steps are necessary during the build-up. Furthermore, the minimal structure size can be achieved using the laser and, in combination with the extrusion parameters, provide structural resolutions desired. Active implant components fabricated using biocompatible materials for both conductive pathways and insulating cladding keep their biocompatible properties even after the additive manufacturing process. In addition, first characterization of the electric properties in terms of impedance towards application in neural tissues are shown. The printing toolkit developed enables processing of low-viscous, flexible polymeric thermal curing materials for fabrication of individualized neural implants.

Past, Present, and Future of Soft-Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing

Millions of people worldwide experience disfigurement due to cancers, congenital defects, or trauma, leading to significant psychological, social, and economic disadvantage. Prosthetics aim to reduce their suffering by restoring aesthetics and function using synthetic materials that mimic the characteristics of native tissue. In the 1900s, natural materials used for thousands of years in prosthetics were replaced by synthetic polymers bringing about significant improvements in fabrication and greater realism and utility. These traditional methods have now been disrupted by the advanced manufacturing revolution, radically changing the materials, methods, and nature of prosthetics. In this report, traditional synthetic polymers and advanced prosthetic materials and manufacturing techniques are discussed, including a focus on prosthetic material degradation. New manufacturing approaches and future technological developments are also discussed in the context of specific tissues requiring aesthetic restoration, such as ear, nose, face, eye, breast, and hand. As advanced manufacturing moves from research into clinical practice, prosthetics can begin new age to significantly improve the quality of life for those suffering tissue loss or disfigurement.

An advanced prosthetic manufacturing framework for economic personalised ear prostheses

Craniofacial prostheses are commonly used to restore aesthetics for those suffering from malformed, damaged, or missing tissue. Traditional fabrication is costly, uncomfortable for the patient, and laborious; involving several hours of hand-crafting by a prosthetist, with the results highly dependent on their skill level. In this paper, we present an advanced manufacturing framework employing three-dimensional scanning, computer-aided design, and computer-aided manufacturing to efficiently fabricate patient-specific ear prostheses. Three-dimensional scans were taken of ears of six participants using a structured light scanner. These were processed using software to model the prostheses and 3-part negative moulds, which were fabricated on a low-cost desktop 3D printer, and cast with silicone to produce ear prostheses. The average cost was approximately $3 for consumables and $116 for 2 h of labour. An injection method with smoothed 3D printed ABS moulds was also developed at a cost of approximately $155 for consumables and labour. This contrasts with traditional hand-crafted prostheses which range from $2,000 to $7,000 and take around 14 to 15 h of labour. This advanced manufacturing framework provides potential for non-invasive, low cost, and high-accuracy alternative to current techniques, is easily translatable to other prostheses, and has potential for further cost reduction.

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

STATEMENT OF PROBLEM

One of the most challenging aspects of auricular prosthesis design and fabrication is ensuring that the prosthesis fits the patient through a range of head and facial movements. Techniques used in conventional prosthetic treatment pathways account for issues of prosthesis fit, but this challenge has not been fully addressed in emerging treatment pathways that use digital technology.

PURPOSE

The purpose of this clinical study was to develop and evaluate a digital workflow by using surface scan data and incorporating the simulation of tissue movement into the design of auricular prostheses that fit the participant through a range of facial movements. An iterative design process was used to develop a design workflow through a sequential case series of participants with auricular prostheses.

MATERIAL AND METHODS

Scan data were acquired from a case series of 5 participants with existing implant-retained auricular prostheses. An iterative design process was used to digitally design auricular prostheses that fit the participants through a range of jaw and facial movements. The fit, shape, and retention of the digitally designed and conventionally made prostheses were assessed and compared. Design considerations were identified and documented through the iterative design process.

RESULTS

A final design workflow was iteratively developed based on the 5 participants. The shapes of the digitally designed prostheses were well matched to nontreatment anatomy overall. Prosthesis fit was variable: Some digitally designed prostheses fit the participant intimately through a range of movements, and others experienced significant gaps between the margins and the tissues.

CONCLUSIONS

An iterative design process provided a method of working toward quality improvement. Although the final design workflow provides a generally successful method of manipulating scan data in the design of auricular prostheses, the prosthesis fit at the anterior margin during facial movements remains variable and requires further development to achieve a consistently acceptable solution.

Advancements in Soft-Tissue Prosthetics Part A: The Art of Imitating Life

Physical disfigurement due to congenital defects, trauma, or cancer causes considerable distress and physical impairment for millions of people worldwide; impacting their economic, psychological and social wellbeing. Since 3000 B.C., prosthetic devices have been used to address these issues by restoring both aesthetics and utility to those with disfigurement. Internationally, academic and industry researchers are constantly developing new materials and manufacturing techniques to provide higher quality and lower cost prostheses to those people who need them. New advanced technologies including 3D imaging, modeling, and printing are revolutionizing the way prostheses are now made. These new approaches are disrupting the traditional and manual art form of prosthetic production which are laborious and costly and are being replaced by more precise and quantitative processes which enable the rapid, low cost production of patient-specific prostheses. In this two part review, we provide a comprehensive report of past, present and emerging soft-tissue prosthetic materials and manufacturing techniques. In this review, part A, we examine, historically, the ideal properts of a polymeric material when applied in soft-tissue prosthetics. We also detail new research approaches to target specific tissues which commonly require aesthetic restoration (e.g. ear, nose and eyes) and discuss both traditional and advanced fabrication methods, from hand-crafted impression based approaches to advanced manufactured prosthetics. We discuss the chemistry and related details of most significant synthetic polymers used in soft-tissue prosthetics in Part B. As advanced manufacturing transitions from research into practice, the five millennia history of prosthetics enters a new age of economic, personalized, advanced soft tissue prosthetics and with this comes significantly improved quality of life for the people affected by tissue loss.

A Pristine Approach for the Prominent Premaxilla in Bilateral Cleft Lip and Palate (BCLP) Cases

OBJECTIVE

The neonate premaxilla in bilateral cleft lip and palate is often protruding and displaced laterally. Surgeons prefer the premaxilla to be repositioned and centralized to allow a tension-free primary lip repair. This report describes the fabrication of a premaxillary bonnet appliance with silicone material and its successful use in 2 cases of bilateral cleft lip and palate (BCLP).

PATIENTS, PARTICIPANTS

Two male BCLP patients of ages 34 days and 10 days, respectively.

INTERVENTIONS

Nonsurgical repositioning of the premaxillary segment using silicone cup-bonnet appliance.

RESULTS

The duration of active treatment by silicone appliance was 36 days in case 1 and 75 days in case 2. The retention period was 2 months and 3 months, respectively. The appliance made of room temperature vulcanizing (RTV) silicone is flexible and softer in comparison to the rigid conventional acrylic appliance and is therefore almost atraumatic. A gentler appliance resulted in enhanced compliance and acceptance by the neonates. There was a noticeable change in the position of the discernible asymmetric premaxilla. Analysis of frontal facial photographs revealed an angular change in the position of the premaxilla (C) by 12° in case 1 and 6° in case 2 in reference to the midfacial plane.

CONCLUSION

This silicone appliance provides enhanced compliance and improved retention compared to acrylic appliance since it is a more gentle, flexible, and less traumatic alternative to a rigid acrylic appliance. Further, the RTV silicone appliance can be 3-dimensionally printed for better accuracy following intraoral scanning and thus eliminating the need for impression making in cleft newborns.

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

PURPOSE

To set up the digital database (DDB) of various anatomical parts, skin details and retention elements in order to simplify the digital workflow of facial prostheses manufacturing; and to quantify the reproduction of skin wrinkles on the prostheses prototypes with stereolithography (SLA) and direct light processing (DLP) methods.

METHODS

Two structured light scanners were used to obtain the nasal and auricle forms of 50 probands. Furthermore, the ala nasi and scapha areas were captured with the digital single lens reflex camera and saved in jpeg format. The four magnetic retention elements were remodeled in computer aided design (CAD) software. The 14 test blocks with embossed wrinkles of 0.05-0.8mm were printed with SLA and DLP methods and afterwards analyzed by means of profilometry and confocal microscopy.

RESULTS

The introduced DDB allows for production of customized facial prosthesis and makes it possible to consider the integration of concrete retention elements on the CAD stage, which makes the prosthesis modelling more predictable and efficient. The obtained skin structures can be applied onto the prosthesis surface for customization. The reproduction of wrinkles from 0.1 to 0.8mm in depth may be associated with the loss of 4.5%-11% of its profile with SLA or DLP respectively. Besides, the reproduction of 0.05mm wrinkles may be met with up to 40% profile increasement.

CONCLUSIONS

The utilization of DDB may simplify the digital workflow of facial prostheses manufacturing. The transfer of digitally applied skin wrinkles till the prostheses' prototypes may be associated with deviations from 11 to 40%.

Direct 3D printing of silicone facial prostheses: A preliminary experience in digital workflow

Direct silicone printing may be applied to the fabrication of maxillofacial prostheses, although its clinical feasibility is unknown. The present clinical report shows an early application of a directly printed silicone prosthesis for the rehabilitation of a nasal defect. Two extraoral scanning systems were used to capture the face and the defect. The virtual construction of the nasal prosthesis was performed with free-form software. Two prostheses were printed in silicone and post-processed by manual sealing and coloring. The clinical outcome was acceptable for an interim prosthesis; however, the marginal adaptation and color match were not satisfactory without further individualization.

Additive Manufacturing: A Comparative Analysis of Dimensional Accuracy and Skin Texture Reproduction of Auricular Prostheses Replicas

PURPOSE

The use of computer-aided design/computer-aided manufacturing (CAD/CAM) and additive manufacturing in maxillofacial prosthetics has been widely acknowledged. Rapid prototyping can be considered for manufacturing of auricular prostheses. Therefore, so-called prostheses replicas can be fabricated by digital means. The objective of this study was to identify a superior additive manufacturing method to fabricate auricular prosthesis replicas (APRs) within a digital workflow.

MATERIALS AND METHODS

Auricles of 23 healthy subjects (mean age of 37.8 years) were measured in vivo with respect to an anthropometrical protocol. Landmarks were volumized with fiducial balls for 3D scanning using a handheld structured light scanner. The 3D CAD dataset was postprocessed, and the same anthropometrical measurements were made in the CAD software with the digital lineal. Each CAD dataset was materialized using fused deposition modeling (FDM), selective laser sintering (SLS), and stereolithography (SL), constituting 53 APR samples. All distances between the landmarks were measured on the APRs. After the determination of the measurement error within the five data groups (in vivo, CAD, FDM, SLS, and SL), the mean values were compared using matched pairs method. To this, the in vivo and CAD dataset were set as references. Finally, the surface structure of the APRs was qualitatively evaluated with stereomicroscopy and profilometry to ascertain the level of skin detail reproduction.

RESULTS

The anthropometrical approach showed drawbacks in measuring the protrusion of the ear's helix. The measurement error within all groups of measurements was calculated between 0.20 and 0.28 mm, implying a high reproducibility. The lowest mean differences of 53 produced APRs were found in FDM (0.43%) followed by SLS (0.54%) and SL (0.59%)--compared to in vivo, and again in FDM (0.20%) followed by SL (0.36%) and SLS (0.39%)--compared to CAD. None of these values exceed the threshold of clinical relevance (1.5%); however, the qualitative evaluation revealed slight shortcomings in skin reproduction for all methods: reproduction of skin details exceeding 0.192 mm in depth was feasible.

CONCLUSION

FDM showed the superior dimensional accuracy and best skin surface reproduction. Moreover, digital acquisition and CAD postprocessing seem to play a more important role in the outcome than the additive manufacturing method used.

Maxillofacial prostheses challenges in resource constrained regions

BACKGROUND

This study reviewed the current state of maxillofacial rehabilitation in resource-limited nations.

METHOD

A rigorous literature review was undertaken using several technical and clinical databases using a variety of key words pertinent to maxillofacial prosthetic rehabilitation and resource-limited areas. In addition, interviews were conducted with researchers, clinicians and prosthetists that had direct experience of volunteering or working in resource-limited countries.

RESULTS

Results from the review and interviews suggest rehabilitating patients in resource-limited countries remains challenging and efforts to improve the situation requires a multifactorial approach.

CONCLUSIONS

In conclusion, public health awareness programmes to reduce the causation of injuries and bespoke maxillofacial prosthetics training programmes to suit these countries, as opposed to attempting to replicate Western training programmes. It is also possible that usage of locally sourced and cheaper materials and the use of low-cost technologies could greatly improve maxillofacial rehabilitation efforts in these localities. Implications for Rehabilitation More information and support needs to be provided to maxillofacial defect/injuries patients and to their families or guardians in a culturally sensitive manner by governments. The health needs, economic and psychological needs of the patients need to be taken into account during the rehabilitation process by clinicians and healthcare organizations. The possibility of developing training programs to suit these resource limited countries and not necessarily follow conventional fabrication methods must be looked into further by educational entities.

Three-dimensional printing in contemporary fixed prosthodontics: A technique article

Digital dentistry has gained in popularity among clinicians and laboratory technicians because of its versatile applications. Three-dimensional (3D) printing has been applied in many areas of dentistry as it offers efficiency, affordability, accessibility, reproducibility, speed, and accuracy. This article describes a technique where 3D printing is used to fabricate a die-trimmed cast and to replicate gingival tissue and implant analogs. The digital workflow that replaces the conventional laboratory procedure is outlined.

Development of a 3D printable maxillofacial silicone: Part II. Optimization of moderator and thixotropic agent

STATEMENT OF PROBLEM

Conventionally, maxillofacial prostheses are fabricated by hand carving the missing anatomic defect in wax and creating a mold into which pigmented silicone elastomer is placed. Digital technologies such as computer numerical control milling and 3-dimensional (3D) printing have been used to prepare molds, directly or indirectly, into which a biocompatible pigmented silicone elastomer can be placed.

PURPOSE

The purpose of this in vitro study was to develop a silicone elastomer that could be 3D printed directly without a mold to create facial or body prostheses by varying its composition.

MATERIAL AND METHODS

The room temperature vulcanizing silicone composition was divided into 2 components which were mixed 1:1 to initiate polymerization in the printer before printing began. Different types of moderators and thixotropic agents were used, and the base composition was varied to obtain 11 formulations. The specimens were printed and polymerized from these formulations and tested for tear and tensile strength and hardness. Ten readings of the specimens were recorded for tear and tensile strength and 6 for hardness. Results were analyzed using ANOVA (α=.05). Visual assessment of uncured printed specimens was undertaken for 5 formulations to assess any differences in their ability to hold their shape after printing.

RESULTS

The tear and tensile strength of the 11 formulations with varying moderators, thixotropic agents, and base compositions were statistically similar to each other (P>.05). Five of 11 formulations were chosen for the visual assessment as they had sufficient thixotropic agent to avoid slumping while printing. The specimens showed varied slumping behavior until they polymerized. The filler content was increased in the selected formulation, and the tear and tensile strength of the formulation was increased to 6.138 kNm^-1 and 3.836 MPa; these increases were comparable to those of commercial silicones currently used for the fabrication of facial prostheses.

CONCLUSIONS

The optimum combination of mechanical properties implies the use of one of the formulations as a suitable material for the 3D printing of facial prostheses.