Maxillofacial Prosthetic Materials Research Articles

Survey of Currently Used Materials for Fabrication of Extraoral Maxillofacial Prostheses in North America, Europe, Asia, and Australia

The purpose of this survey was to review the extraoral maxillofacial materials currently used as well as the advantages and disadvantages of the materials in the fabrication of facial prostheses. Results of this survey will enhance scientific knowledge, generate research study ideas, and possibly lead to production of alternative or new maxillofacial materials. A 47-question survey was delivered via e-mail to all members (combined total of 260 members) of the American Anaplastology Association (AAA) and American Academy of Maxillofacial Prosthetics (AAMP) for evaluation of personal preference involving maxillofacial prosthetic materials (intrinsic/extrinsic silicone elastomers and pigments/colorants used, polymerization/curing process, advantages and disadvantages of the most often used materials, most important characteristic of material/technique used). The views of 43 (16%) respondents indicated that the majority surveyed were using room temperature-vulcanized (RTV) silicone products. Silicone pigments for intrinsic and silicone pastes for extrinsic coloring were favored over artist's oil colors and dry earth pigments. The polymerization process and/or curing times and temperatures for the same silicone material varied between users. The top five advantages of most often used materials were good esthetics, ease of coloring, easy manipulation, thin margins possible, and adhesive compatibility. The top five disadvantages were discoloration over time, technique-sensitivity, lack of repairability, extrinsic colors peel/fade, and lack of longevity. Nontoxic/nonallergenic materials with high edge strength and color stability were the most important features when choosing a maxillofacial prosthetic material/technique. The responses to this survey indicate that the majority of AAA and AAMP members are using or have used a variety of RTV silicones, pigments, and colorants in the quest to provide the best possible facial prosthetic service. Further research is needed to further refine and improve extraoral maxillofacial materials/techniques based on the results of this study.

Teaching of color in predoctoral and postdoctoral dental education in 2009

Objectives The goal of the study was to determine the current status of the teaching of color in dental education at both the predoctoral (Pre-D) and postdoctoral (Post-D) levels. Methods A cross-sectional web-based survey, containing 27 multiple choice, multiple best and single best answers was created. Upon receiving the administrative approval, dental faculty involved in the teaching of color to Pre-D or Post-D dental students from around the world ( N = 205), were administered a survey. Statistical analysis of differences between Pre-D and Post-D was performed using Chi-square test ( α = 0.05). Results A total of 130 responses were received (response rate 63.4%); there were 70 responses from North America, 40 from Europe, 10 from South America, nine from Asia and one from Africa. A course on “color” or “color in dentistry” was included in the dental curriculum of 80% of Pre-D programs and 82% of Post-D programs. The number of hours dedicated to color-related topics was 4.0 ± 2.4 for Pre-D and 5.5 ± 2.9 for Post-D, respectively ( p < 0.01). Topics associated with tooth color, shade matching method, tooth whitening, and teaching of appearance parameters other than color, were frequently taught. Conclusions Significant differences were recorded between the number of hours dedicated to teaching of color at predoctoral and postdoctoral level. The same is true for the prosthodontics and restorative courses, teaching on negative after images; color rendering index, Bleachedguide 3D-Master shade guide, digital camera and lens selection, composite resins, and maxillofacial prosthetic materials. Except for the restorative courses and composite resins, significantly higher results were recorded for Post-D programs. Vitapan Classical and 3D-Master were the most frequently taught shade guides.

Dynamic visco-elastic analysis of silicone maxillo-facial prosthetic material using custom-made dynamic visco-elastometer and LASER measuring device

Purpose : The dynamic mechanical properties of silicone maxillo-facial prosthetic material are very important for the successful rehabilitation of patients with facial defects. Moreover, it is equally important to determine these properties under conditions similar to those observed in the natural movement of facial tissues. This study evaluates the dynamic mechanical properties of silicone maxillo-facial prosthetic material using the classical Torsional pendulum method and high precision laser based measurement system. Materials and Methods : Five commercially available silicone maxillofacial prosthetic materials A-2002, A-2186, A-VST-50, A-588V-1and MDX4-4210 were taken as sample in the form of cylinders measuring 8X80 mm. A custom-made dynamic visco-elastometer was used to determine the Storage modulus, Loss modulus and Loss tangent over a frequency range of 0.5 to 1.0 Hertz at 37΀Celsius. Results : A-VST-50, A-588V-1 had low loss tangent (P less than 0.05), further they had lower storage modulus than other tested material, which is an added advantage over MDX4-4210 and A-2186. At all test frequencies A-2002 was found to have the highest loss modulus as well as the highest loss tangent (damping factor) among all the five kinds of material tested (P less than 0.05) which indicates its slow response to load but large capacity to absorb energy. Conclusion : Custom-made dynamic visco-elastometer has proved to be reliable, low cost and a convenient instrument to evaluate silicone maxillo-facial prosthetic material. No single material was found to have all the desirable dynamic mechanical properties necessary for maxillo-facial prosthesis applications. Therefore, layering of two or more such kind of materials is recommended to achieve desirable properties.

Adhesive retention of silicone and chlorinated polyethylene for maxillofacial prostheses

A key factor of a successful facial prosthesis is the retention of the prosthesis to the patient's skin, especially when there is no mechanical means and the retention depends primarily on medical skin adhesives. Studies determining which medical adhesives provide the best bond strength for maxillofacial prostheses are needed. The purpose of this study was to quantify the force required to detach strips of Silastic Adhesive A/MDX4-4,210 silicone elastomer with a urethane liner (A/M-U) and experimental chlorinated polyethylene elastomer (CPE) from the skin of human subjects coated with a protective dressing using 1 of 2 medical adhesives. With IRB approval, 8 A/M-U and CPE rubber strips (total of 208) were applied in a predetermined random order to the left and right ventral forearms of 26 human subjects. Skin-Prep Protective Dressing (SP) was applied to half of the sites just before Epithane-3 (E3) and Secure(2) Medical Adhesive (SMA) were used to adhere the strips. Strips were peeled 6 hours later in a universal testing machine at 10 cm/min. Data are reported in newton/meter (N/m). The data was compared using a 3-way, within-groups, multivariate analysis of variance (MANOVA) and the Fisher exact test (alpha=.05). Values for N/m under various conditions relating to the subjects were compared by the Tukey HSD Test for unequal N (alpha=.05). Data are reported as mean (SD). Statistical analysis revealed no differences (mean (SD)) and no significant interactions between the independent variables (A/M-U = 94.6 (62.1) and CPE = 98.4 (69.6) N/m, SP = 93.0 (58.8) and no SP = 99.8 (72.1) N/m, E3 = 97.6 (69.8) and SMA = 95.3 (61.8) N/m; P=.984). Debonding occurred at the skin interface for both adhesives, as evidenced by residue on prosthetic materials (Fisher exact test; P<.005). The adhesive bond strengths of both SMA and E3, with and without the presence of SP, were not significantly different between A/M-U and CPE maxillofacial prosthetic materials. Adhesive failure occurred at the skin interface.

Advance in maxillofacial prosthetic materials

综述了目前口腔颌面赝复材料种类、性能要求及各种颌面赝复材料的组成、性能和应用过程,探讨了各种颌面赝复材料的优势及不足,指出目前临床应用的颌面赝复材料以硅橡胶类为主,其中又以中温硫化硅橡胶和室温硫化硅橡胶综合性能较好,应用最为广泛。

Surface modification of an experimental silicone rubber maxillofacial material to improve wettability

Objectives. Good wettability of maxillofacial prosthetic materials is important so that a lubricating layer is formed with supporting tissues thus reducing patient discomfort. The purpose of the study was to surface modify an experimental silicone rubber material in order to improve wettability. Methods. Samples of experimental silicone rubber were surface modified by first argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes. These were compared with the same silicone rubber which had ethyleneoxy functional surfactants incorporated into the polymer matrix. In all cases contact angles, tear strength and water uptake were measured. Results. Surface modified materials had comparable contact angles to surfactant modified silicone rubber all being significantly lower than the unmodified material. Surface modified materials, however, had a significantly higher tear strength and lower water uptake in comparison to surfactant modified materials. Conclusions. Argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes proved an effective way of improving the wettability of an experimental silicone rubber maxillofacial prosthetic material without altering bulk properties.

Surface modification of an experimental silicone rubber maxillofacial material to improve wettability

Objectives. Good wettability of maxillofacial prosthetic materials is important so that a lubricating layer is formed with supporting tissues thus reducing patient discomfort. The purpose of the study was to surface modify an experimental silicone rubber material in order to improve wettability. Methods. Samples of experimental silicone rubber were surface modified by first argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes. These were compared with the same silicone rubber which had ethyleneoxy functional surfactants incorporated into the polymer matrix. In all cases contact angles, tear strength and water uptake were measured. Results. Surface modified materials had comparable contact angles to surfactant modified silicone rubber all being significantly lower than the unmodified material. Surface modified materials, however, had a significantly higher tear strength and lower water uptake in comparison to surfactant modified materials. Conclusions. Argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes proved an effective way of improving the wettability of an experimental silicone rubber maxillofacial prosthetic material without altering bulk properties.

Analysis of the properties of silicone rubber maxillofacial prosthetic materials

Objectives. Maxillofacial prosthetic materials are used to replace facial parts lost through disease or trauma. Silicone rubbers are the materials of choice, however it is widely accepted that these materials do not possess ideal properties. The objective of this study was to assess the properties of a range of commercially available silicone rubber maxillofacial materials and make recommendations for improvements. Methods. Specimens of five commonly used maxillofacial materials were prepared in dental flasks according manufacturers instructions. Tear strength, tensile strength, percentage elongation, hardness, water absorption and water contact angles were determined for each material. Results. The tear strength of Factor II, Cosmesil HC and Nusil were all comparable and significantly higher than Cosmesil St and Prestige ( p<0.001). Nusil had a significantly higher tensile strength and elongation in comparison to the other materials ( p<0.001) and Cosmesil St and Cosmesil HC were significantly harder ( p<0.001). Factor II was significantly less wetted and Prestige and Cosmsesil St had a significantly higher water absorption in comparison to the other materials. Conclusions. None of the commercially available silicone rubber materials possessed ideal properties for use as a maxillofacial prosthetic material. Factor II, however, showed more favourable properties due to it's high tear strength, softness and ease of manipulation.

New organosilicon maxillofacial prosthetic materials

Objectives: The silicone elastomer A-2186 is a widely used maxillofacial prosthetic material. It is a pourable two-component silicone rubber cured by a platinum catalyst. Used as a prosthetic material, A-2186 has short working time and because of its hydrophobic nature, poor adhesion to non-silicone based adhesives. The purpose of this study is to evaluate the physical properties of new prosthetic materials based on methacryloxypropyl-terminated polydimethylsiloxane (MPDS-MF), and to compare the properties with those of A-2186. Methods: Hardness, tensile strength, ultimate elongation, tear strength and adhesive bonding strength of MPDS-MF and A-2186 with and without additives were determined and compared. The bonding strengths of the extrinsic colorant carrier with the prosthetic materials were also determined. Statistical analyses were done using a two-way analysis of variance (ANOVA). For significant effects, post-hoc tests were done using the Bonferroni correction. Results: The hardness of MPDS-MF is similar to A-2186. However, tensile strength, tear strength, ultimate elongation, and adhesive bonding strength of MPDS-MF are higher than those of A-2186. Significance: MPDS-MF is cured by free radical thermal polymerization and crosslinking. The working time of MPDS-MF, unlike A-2186, is long. The presence of methacrylate groups in MPDS-MF enhances its adhesion to non-silicone based adhesive. Based on the present study, it appears that MPDS-MF is suitable for use in fabricating of clinical prostheses.

The Leicester radiotherapy bite block: an aid to head andneck radiotherapy

We describe the construction of a custom-made bite block to be used during external beam radiotherapy to the oral cavity. The bite block is made with standard maxillofacial prosthetic techniques and materials. The design allows accurate and reproducible positioning of the perioral tissues to aid planning of radiotherapy and treatment. The compressibility of this device improves comfort for the patient, while it is in use.

Effects of processing parameters on physical properties of the silicone maxillofacial prosthetic materials

Objectives: Maxillofacial prostheses are commonly fabricated using dental stone molds. However, for evaluating physical properties, maxillofacial materials are most often cured in metal molds. A-2186 is a silicone-based maxillofacial prosthetic material. Because its cure may be inhibited by traces of impurities, its physical properties may be different when it contains additives and is cured in dental stone molds, compared to when it is cured in metal molds without additives. This study's purpose is to determine and compare the physical properties of A-2186 cured in stainless steel molds and stone molds. The effects of additives and cure conditions on the physical properties were also studied. Methods: Hardness, tensile strength, ultimate elongation, and tear strength of A-2186 cured in dental stone molds, stainless steel molds, and with and without additives were determined. The bonding strength of A-2186 to four adhesives was determined by the peel test. All comparisons were made using analysis of variance (ANOVA). Results: Hardness, tensile strength and ultimate elongation of A-2186 cured in stainless steel molds are significantly higher than those cured in stone molds. Adding a small amount of a pigment, a kaolin and a fiber reduces hardness, tensile strength, ultimate elongation and tear strength. Except for Hydrobond, the bond strength of the adhesives to A-2186 was not significantly affected by the cure conditions and additives. Significance: Physical properties of A-2186 are affected by the additives commonly used in fabricating maxillofacial prostheses, and use of stone molds for curing degrades A-2186’s mechanical properties. In fabricating clinical prostheses, special attention should be exercised to avoid contamination of A-2186 with impurities that could inhibit curing and produce inferior prostheses.

Wettability of silicone rubber maxillofacial prosthetic materials

Maxillofacial prosthetic materials that contact skin or mucosa should have good wettability. A material that is easily wetted will form a superior lubricating layer between the supporting tissues and, thus, reduce friction and patient discomfort. The surface energy of a maxillofacial prosthetic material will give an indication of the amount of energy available for adhesion and of the susceptibility of the material to bacterial adhesion. This study evaluated the wettability and surface energies of a range of commercially available silicone rubber maxillofacial prosthetic materials. Contact angles and surface energies were measured by using a dynamic contact angle measuring technique. Four commonly used silicone maxillofacial materials were tested and their properties compared with those of an acrylic resin denture base material and a widely used denture soft lining material. There were no significant differences in the wettability of the silicone rubber materials. All materials were significantly less wetted than the denture acrylic resin material. There were no significant differences in the surface energies of the silicone rubber materials, but all were significantly lower than denture acrylic resin material. The Cahn dynamic contact angle analyzer was a quick and reproducible method for determining the contact angles and surface energies of maxillofacial materials. Further work is needed to improve the wettability of silicone rubber materials used for maxillofacial prostheses, thus, reducing their potential to produce friction with tissues.

Dynamic mechanical thermal analysis of maxillofacial elastomers

Maxillofacial prosthetic materials should simulate the oral tissues as much as possible and therefore have a similar flexibility and resilience. In light of the oral tissues constantly moving, the dynamic deformation properties of maxillofacial materials would seem the most relevant. In this study, dynamic mechanical thermal analysis was used to evaluate the deformation properties of five silicone rubber materials used to construct facial prostheses. The technique involves the application of a sinusoidally oscillating stress to a material and analyzes how the material elastically or viscoelastically responds to the stress. The dynamic mechanical thermal analysis can operate at a fixed frequency or range of frequencies over a specific temperature range and also isothermally as a function of time. Cosmesil and A-2186 materials were the most resilient materials and Silbione had the greater energy absorption capacity, which was particularly noticeable at the higher frequencies. Silbione also had a lower shear modulus (G'), which indicated it was more flexible than the other materials. The dynamic mechanical thermal analysis proved to be a rapid, reliable, and convenient method for the determination of viscoelastic properties of maxillofacial materials.

Effects of RTC-silicone maxillofacial prosthetic elastomers on cell cultures

The use of a wide variety of materials in the construction of maxillofacial prostheses makes biocompatibility testing a necessity. However, the dental literature contains few reports of biocompatibility testing of maxillofacial prosthetic materials. The cytotoxic profiles of five room-temperature cross-linking (RTC)-silicone elastomers were investigated by means of two in vitro cell culture techniques. Mouse fibroblast cells (L929) were used, and the results indicated that RTC-silicone elastomers adversely affected cells in culture and that storage of samples for 1 week in saline solution did not alter this effect. Clinical follow-up of patients wearing prostheses made of these silicone materials is warranted to evaluate host reactions in long-term contact with human mucous membrane and skin tissue.

Frictional properties of maxillofacial prosthetic elastomers

An investigation was made of the surface characteristics of two silicone base maxillofacial prosthetic materials, in terms of surface roughness and coefficient of friction, in order to compare these characteristics with those of human skin. Both elastomers were found to display lower frictional coefficient than the human skin and their surface texture did not seem to have an effect on these results. Oxidative treatment of the silicon surface increases the value of the frictional coefficient, probably due to the adsorption of atmospheric moisture.

Effects of environmental factors on maxillofacial elastomers: Part IV—Optical properties

The optical properties of four currently used and two recently introduced maxillofacial prosthetic materials were evaluated after the materials were subjected to the following seven environmental variables: natural weathering; normal aging; two types of adhesives; two types of cleaning agents; and cosmetics. Optical density and color changes were evaluated. The currently used silicones Silastic 4-4210 and Silastic 4-4515, Medical Adhesive type A material, and Polyurethane all showed more changes in color and optical density than the newly introduced silicone A-102 material.

Effects of environmental factors on maxillofacial elastomers: Part III—Physical properties

The physical properties of four currently used and two recently introduced maxillofacial prosthetic materials were evaluated after the materials were subjected to the following seven environmental variables: natural weathering, normal aging, two types of adhesives, two types of cleaning agents and cosmetics. Ultimate tensile strength, percent elongation, tear strength, and Shore A hardness were evaluated. The physical properties recorded for the currently used materials were consistent with previous studies. Although the properties of the recently introduced materials were similar to those currently in use, one of the new materials, A-2186, showed high strength values, although it was one of the softest materials tested. Unfortunately, this new material lost these advantageous characteristics as it was weakened and made harder by most of the tested environmental variables.

Biocompatibility testing of a silicone maxillofacial prosthetic elastomer: Soft tissue study in primates

Little information exists on the biocompatibility of maxillofacial prosthetic materials. Cosmesil material is a purpose-designed facial prosthetic elastomer that has an established clinical profile in humans but results of biocompatibility testing have not been published. Cosmesil, acrylic resin (positive control), black surgical gutta-percha (negative control), and Silastic 382 material (Dow Corning, Midland, Mich.) (reference control) were processed as custom-designed implants. The implants were inserted into five chacma baboons for a 12-week period in intraosseous, subperiosteal, submucosal, and intramuscular sites. The histologic assessment was based on a modified form of the PDI-ISO Technical Report 7405 for subcutaneous implants. An evaluation was made of capsule formation and inflammatory response. The statistical analysis involved a three-way ANOVA and a Tukey-Kramer Student range test. The critical level of statistical significance chosen was p < 0.05. The study found that gutta-percha provoked a statistically significatly thicker capsule and a severe inflammatory response. Acrylic resin, Cosmesil material, and Silastic 382 material produced capsule formations and an inflammatory response that did not differ significantly. Cosmesil material is not manufactured as an implant material, but from the present findings it is considered acceptably biocompatible for its intended use where there may be contact with internal tissue spaces that are contiguous to external surfaces.

Physical properties of maxillofacial elastomers under conditions of accelerated aging.

The stability of the physical properties of various commercially available maxillofacial prosthetic materials was evaluated with the use of an accelerated aging chamber. The tensile strength, maximum percent elongation, shear strength, tear energy, and Shore A hardness were determined before and after accelerated aging. Results indicate that silicone 44210, a RTV rubber, is a promising elastomer for maxillofacial application.

Maxillofacial prostheses of chlorinated polyethylene.

There is clearly a need for maxillofacial prosthetic materials with improved properties. The chlorinated polyethylenes are thermoplastic elastomers which have particularly promising properties, and were used by us to prepare improved maxillofacial prostheses. Suitable CPE resins were compounded with other polymers and with pigments on a heated rubber mill to form thin sheets in a variety of shades. These were heated at 190 degrees C for 10 min and placed between heated linotype mold halves. The prosthesis was formed in a hand press. Sometimes heating and pressing were repeated. After cooling in water, the prosthesis was removed and hand-shaded with oil-soluble dyes. Physical properties were evaluated using standard techniques; skin irritation studies were conducted by 14-day insult patch tests on rabbits. Clinical evaluations were conducted on human volunteers. Parallel evaluations were conducted on commerically available materials for comparison. The CPE was superior to all of the three commerical materials in most properties, and comparable to the better of the three in the remaining properties. On balance, CPE was significantly superior. Early results indicate that the materials and techniques required are easily handled in the dental lab and that the final prosthesis has excellent aesthetic and patient acceptability.