Microbial biofilms on facial prostheses

In situ study of the effect of endogenous and exogenous agents on color stability, hardness, and surface roughness of an elastomer for facial prostheses

PURPOSE

To evaluate in situ the influence of sweat, oil, sunscreen, and disinfectant solution on the color stability, hardness, and roughness of elastomer for facial prostheses.

MATERIALS AND METHODS

Standardized and intrinsically pigmented specimens remained in contact with human skin from the same person for 30 days, considering exposures (n = 36 per group), absent of exposition (Control, C); sweat and oiliness contact (SO); sweat and oiliness associated with sunscreen (SOS); 0.12% chlorhexidine digluconate immersion (CD0.12%); and all agents exposed (SOSCD). The main variables were color change (CIELab and National Standard Bureau system, NBS), Shore A hardness, and surface roughness, measured at baseline and 30 days. Qualitative analyses were performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The data were analyzed by Kruskal-Wallis tests (color) and two-way ANOVA (hardness and roughness) with Sidak post-test (α = 0.05).

RESULTS

CD0.12% (1.54 ± 0.49) and SOSCD (2.10 ± 1.03) had similar effects and caused the smallest color changes, considered mild and noticeable (NBS), respectively. SOS promoted the greatest color change (6.99 ± 1.43, NBS: large) and hardness (17.97 ± 0.56); SOS promoted intermediate roughness (3.48 ± 1.05) between SOSCD (2.25 ± 0.53), and two similar groups: C (4.46 ± 0.95), and CD0.12% (4.39 ± 1.26). The qualitative analysis showed an irregular, dense, dry, and whitish layer on the surface of the specimens exposed to sunscreen, which was reduced when in contact with 0.12% chlorhexidine digluconate.

CONCLUSIONS

Endogenous and exogenous factors are capable of altering elastomer properties. The 0.12% chlorhexidine digluconate minimized the changes caused by sweat, oil, and sunscreen.

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.

Biocompatibility profile of aged pigmented and non-pigmented silicone elastomer for combined maxillofacial defects

PURPOSE

To assess the biocompatibility of platinum silicone elastomer A-2000 used in combined maxillofacial defects prosthesis, after being deteriorated by an accelerated aging process resembling both the extra and intraoral environment. This assessment was done indirectly on human-derived dermal and gingival tissues.

MATERIALS AND METHODS

One hundred eight samples of room-temperature vulcanized A-2000 platinum silicone were equally divided into extrinsically pigmented and non-pigmented groups to replicate combined maxillofacial defects. Accelerated aging was applied to pigmented samples to mimic extra- and intra-oral conditions, while non-aged counterparts served as controls. After isolating human cell lineages, dermal and gingival fibroblasts were indirectly exposed to silicone sample media. Cytotoxicity to cultured fibroblasts was assessed via MTT assay. Statistical significance was determined by repeated measures of one-way ANOVA (p < 0.01), evaluating cytotoxicity on dermal and gingival fibroblasts.

RESULTS

MTT assay showed increased cytotoxicity in pigmented silicon samples subjected to extraoral aging compared to non-aged counterparts (p < 0.01). Non-pigmented silicon, modeling intraoral conditions, exhibited cytotoxicity after 48 h (p < 0.05). Both aged and non-aged silicon extracts equally sensitized gingival fibroblasts at 72 h (p < 0.001). Negative correlations between pigmented and non-pigmented silicon were observed in dermal cell growth (p > 0.05, except at 24 h, r = 0.2), with accelerated aging showing minimal impact on the pigmentation effect (p > 0.05).

CONCLUSION

The retrieved diminished cellular metabolic activity of platinum silicone elastomer was in an acceptable clinical range, pointing out the importance of periodic assessments of the maxillofacial prosthesis for replacement depending on aging and cytotoxic harmful cellular responses.

Microwave disinfection of facial silicone prostheses, Part 1: Color stability

STATEMENT OF PROBLEM

The choice of cleaning method is an important consideration for lengthening the serviceable time of facial prostheses as microbial organisms and biofilms could degrade facial prostheses and cause skin irritation. Whether microwave disinfection is a suitable cleaning method without degradation of the properties of a prosthesis is unclear.

PURPOSE

The purpose of this in vitro study was to measure the color stability of 6 commonly used facial silicone elastomers after microwave disinfection over a simulated 1.5-year period.

MATERIAL AND METHODS

Six different facial silicone elastomers: MDX4-4210, MDX4-4210/Type A, M511, A-2186, VST-50, and A-2000 were mixed with intrinsic silicone white opacifier (except for the control group) and subsequently combined with 4 silicone intrinsic pigment color groups: red (R), yellow (Y), burnt sienna (B), and a mixture of R+Y+B (M). The control group was a silicone elastomer without opacifier or pigment. Each of the 30 experimental groups consisted of 5 specimens (N=150). Five specimens were placed in a 250-mL Erlenmeyer flask filled with 160 mL of tap water. Seven flasks were then placed in a 660-W microwave oven. An exposure of 6 minutes was used according to the antimicrobial efficacy of microwave disinfection protocol on facial silicone prostheses with a final water temperature of 60 °C for 18 times (simulating 1.5 years of microwave disinfection with one 6-minute exposure monthly). A spectrophotometer was used to measure reflectance color change values (∆E). Color differences were calculated following CIELab (∆E*ab) and CIEDE2000 (∆E00) formulae. ∆E*ab and ∆E00 were statistically analyzed by a linear mixed effects model with 3 factors (silicone type, color shade, and time) using the R Statistical software program (α=.05).

RESULTS

Both ∆E*ab and ∆E00 of all silicone elastomers studied were less than the visual perceptibility thresholds (∆E*ab<1.1 and E00<0.7) and were considered clinically acceptable (∆E*ab<3.0 and E00<2.1) after the 1.5-year simulation of microwave disinfection. Yellow and blue pigments had more effect on MDX4-4210 and M511, while red pigment had more effect on MDX4-4210, MDX4-4210/Type A, and M511 (P<.05). Nevertheless, the values were still below the perceptibility threshold (∆E*ab≤1.0 and E00<0.6).

CONCLUSIONS

All 6 facial silicone elastomers maintained clinically acceptable color after 18 months of exposure to microwave disinfection.

Evaluation of Mangifera indica, Anacardium occidentale leaf extracts and 0.2% Chlorhexidine gluconate on disinfection of maxillofacial silicone material surface contaminated with microorganisms - An invitro study

Maintenance of the quality and hygiene of maxillofacial prosthesis allows to maintain the health of the residual tissues. Sampling of the maxillofacial prostheses has relieved presence of microbial colonization on silicone surfaces. Cleaning procedures of maxillofacial silicones are done using mechanical means or using adjunctive with chemical means. Cleaning with a 2-4% chlorhexidine gluconate spray or dipping in solution for a minute and then washing under running water can sufficiently condition to reduce the amount of bacterial contamination. Due to rising microorganism resistance and fewer adverse effects, phytoextracts appear to be a viable option. Additionally, the use of excipients derived from plants is provides new opportunities for the pharmaceutical industry into the creation of innovative pharmaceutical products that are sustainable.

Aim

To evaluate and compare the leaf extracts of Mangifera indica (M.indica), Anacardium occidentale(A.occidentale) and 0.2% chlorhexidine gluconate (CHX) on disinfection of maxillofacial silicone material surface contaminated with Staphylococcus aureus (S.aureus) and Candida albicans (C.albicans).

Methods

Of the 150 maxillofacial silicone elastomer silicone samples, 75 samples were contaminated with S. aureus and 75 with C.albicans. The contaminated disc was rolled on blood agar and pre-disinfection Colony Forming Units (CFU) were evaluated followed by subjecting the discs to disinfection protocols. The contaminated discs with S. aureus and C.albicans were disinfected using M.indica leaf extracts, A.occidentale leaf extracts and 0.2% CHX for 10 min. Post-disinfection CFUs were evaluated by rolling the disc on blood agar. The results were tabulated and analysed using dependent t-test, one-way ANOVA and Tukeys multiple posthoc procedure.

Results

Pair-wise comparison of pre-and post-disinfection log CFU counts of S.aureus gave a statistical significance between 0.2% CHX and and M.indica leaf extract. No statistically significant results were found between 0.2% CHX and A.occidentale. Pair wise comparison of the log CFU from pre-disinfection to post-disinfection of C.albicans gave a statistical significance between all the three groups.

Conclusions

In the present study A.occidentale leaf extract and M.indica leaf extract have shown significant reduction in CFU of both the organisms. 0.2% CHX showed the most CFU reduction post disinfection of maxillofacial silicone material surface contaminated S.aureus and C.albicans followed by A.occidentale leaf extracts and M.indica leaf extracts. Given the limitations of the current research, A.occidentale leaf extract and M.indica leaf extract can be used as an alternative for disinfection of maxillofacial silicone prosthesis.

Ultraviolet C as a method of disinfecting medical silicone used in facial prostheses: An in vitro study - Part 2

STATEMENT OF PROBLEM

Disinfection is an important factor in preserving facial prostheses and maintaining tissue health. However, whether disinfection with ultraviolet C is an effective disinfection method is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the effectiveness of irradiation with different exposure durations of an ultraviolet-C light-emitting diode in the disinfection of the silicone (A-588-1; Factor II) used in facial prostheses.

MATERIAL AND METHODS

A total of 216 specimens were prepared, contaminated by multispecies biofilm, and divided into 9 groups (n=24) for different treatments: chlorhexidine 0.12% (G CHG), ultraviolet-C light-emitting diode for 5 minutes (G UVC5), ultraviolet-C light-emitting diode for 10 minutes (G UVC10), ultraviolet-C light-emitting diode for 20 minutes (G UVC20), their respective untreated controls (Gcontrol CHG, Gcontrol UVC5, Gcontrol UVC10, Gcontrol UVC20), and dimethyl sulfoxide (G DMSO) as the negative control. Cell viability was measured by using the methyl tetrazolium salt (MTT) method. Two statistical analyses were performed. First, a 2×3 ANOVA was carried out to compare the control groups (Gcontrol UVC5, Gcontrol UVC10, and Gcontrol UVC20) and the experimental groups of UV-C LED light with different exposure durations (G UVC5, G UVC10, and G UVC20). The second analysis was performed using generalized linear models to compare the optical density of the groups (G UVC5, G UVC10, G UVC20, G CHG, and G DMSO).

RESULTS

Cell viability results demonstrated a microbial reduction after exposure to the ultraviolet-C light-emitting diode for 20 minutes (G UVC20) compared with untreated controls (P<.05). The 5- and 10-minute exposures were statistically similar to their respective control groups (P>.05). The 20 minutes exposure had the lowest average optical density value, being statistically different from the 5-minute exposure (P<.05). A 20-minute exposure to the ultraviolet-C light-emitting diode (G UVC20) was similarly effective when compared with the standard disinfection treatment (G CHG) and dimethyl sulfoxide (G DMSO) (P>.05).

CONCLUSIONS

Irradiation with an ultraviolet-C light-emitting diode for 20 minutes decreased the in vitro microbial cell viability on the medical silicone used in facial prostheses.

Coloring Effects of Disinfectants on Pure or Nano-TiO2-Incorporated Maxillofacial Silicone Prostheses

Silicone elastomers play a crucial role in the field of maxillofacial prosthodontics. To maintain optimal hygiene, various disinfectants have been reported to clean silicone prostheses. Nevertheless, when selecting a disinfectant, it is important to consider not only its antimicrobial efficacy, but also its compatibility with the materials, to minimize any potential impact on the physical properties of the material surfaces. The coloring effect of such disinfectants on different types of silicone is of interest. A total of 144 silicone specimens (72 pure silicones, 72 nano-TiO2-incorporated silicones, from A-2000 and A-2006 silicones) were fabricated in this study. The spectrophotometric analysis was carried out, and the initial CIE L*a*b* color values were measured prior to disinfection. Specimens in each silicone group (with or without nano-TiO2) were subjected to a 30-h disinfection period simulating 1 year of disinfection with the following disinfectants: Control (tap water), 0.2% chlorhexidine gluconate, 4% chlorhexidine gluconate, 1% NaOCl, neutral soap, and effervescent. After the second color values were recorded, the color change (∆E*) was calculated. Significant differences were observed among the disinfectants for both the A-2000 and A-2006 silicone groups. Nano-TiO2 did not show a color protection effect in A-2000 silicone. In contrast, nano-TiO2 incorporation provided color protection against CHG 0.2%, CHG 4%, and NaOCl in A-2006 silicone. Most of the disinfectants did not show acceptable color stability over time. In pure A-2000 silicone, except for 0.2% chlorhexidine, all disinfectant groups demonstrated a color change within the acceptability threshold of 50:50% (∆E* = 3.0). On the other hand, in nano-TiO2-incorporated A-2006 silicone, only 0.2% and 4% chlorhexidine demonstrated an acceptable color change. Overall, chlorhexidine could be used as a suitable disinfectant in maxillofacial silicone prostheses.

Disinfectant effects of Brazilian green propolis alcohol solutions on the Staphylococcus aureus biofilm of maxillofacial prosthesis polymers

STATEMENT OF PROBLEM

Brazilian green propolis may be an alternative product that reduces the development of a microbial biofilm on the polymers used for maxillofacial prostheses. However, its effects as a disinfectant have not been fully established.

PURPOSE

The purpose of this in vitro study was to investigate the effects of Brazilian green propolis alcohol solutions against the Staphylococcus aureus biofilm on polymers used in maxillofacial prostheses, the maxillofacial silicone elastomer (MDX4-4210), and specific acrylic resins for ocular prostheses.

MATERIAL AND METHODS

A total of 324 disk-shaped specimens (3×10 mm) of each material were fabricated. All specimens were contaminated with S. aureus (10⁸ cells/mL) to assess the antibiofilm activity of immersion solutions and protocols. Thus, 162 specimens of each material were randomly distributed and equally divided into 5 groups of disinfectants and 1 control group: 3 separate groups of 2.5%, 5%, and 10% propolis alcohol solutions, 1 group of 5% propolis alcohol gel, a positive control group of 2% chlorhexidine gluconate, and a negative control group of distilled water. Specimens (n=9) were disinfected by immersion for 5, 10, and 15 minutes and immersed in culture medium for 24 hours. Any notable turgescence in the final medium was considered indicative of a biofilm. The effects of disinfectants were analyzed by a turbidity assay and by scanning electron microscopy. Data were analyzed descriptively.

RESULTS

The final medium with specimens disinfected with 10% propolis alcohol solution showed no turbidity, indicating constant efficacy against the S. aureus biofilm. Similarly, these findings were observed in the 2% chlorhexidine gluconate group. Scanning electron microscopy images demonstrated that the surface of the polymers treated with 10% propolis alcohol solution did not show bacterial colonies.

CONCLUSIONS

Disinfection with 10% green propolis alcohol solution was effective in eliminating the S. aureus biofilm from specimens of maxillofacial elastomer and N1 acrylic resin specific to ocular prostheses by immersion for 5 minutes.

Antimicrobial adhesive polyurethane gel sheet with cetylpyridinium chloride-montmorillonite for facial and somato prosthesis fastening

PURPOSE

Existing options for attaching facial and somato prostheses, such as skin adhesives, are problematic because of microbial colonization and skin irritation. This study aims to evaluate the suitability of adhesive polyurethane gel sheets containing cetylpyridinium chloride (CPC)-montmorillonite (Mont) for prosthesis fastening.

METHODS

Adhesive gel sheets were fabricated as mixtures of base resin (99.6 wt% polyol) and hardening agent at a ratio of 3:1 with 0 (control), 2, 5, 10, or 15 wt% CPC-Mont. The controlled release of CPC, antimicrobial activity, in vitro skin irritation, and adhesive force against silicone and human skin at different blending ratios were determined. Statistical analyses of the data were performed using one-way analysis of variance (ANOVA), analysis of covariance (ANCOVA), Tukey's test, or single regression analysis, as appropriate.

RESULTS

The amount of CPC released increased with the CPC-Mont blending ratio and was linearly proportional to the surface occupation area ratio of CPC-Mont. The samples with >5 wt% CPC-Mont exhibited antimicrobial activity against Staphylococcus aureus at an exposure time of 0 d, and samples with >2 wt% CPC-Mont exhibited antimicrobial activity against Candida albicans at an exposure time of 1 d. All samples were classified as non-irritant based on an in vitro skin irritation test. The adhesive force on the silicone material and human skin decreased with increasing CPC-Mont blending ratio.

CONCLUSION

Samples with 5 wt% CPC-Mont are potential candidates as antimicrobial adhesive polyurethane gel sheets for fastening facial and somato prostheses.

Fungicidal Effect of Lemongrass Essential Oil on Candida albicans Biofilm Pre-established on Maxillofacial Silicone Specimens

Aims:

This in-vitro study aimed to evaluate the efficacy of lemongrass (Cymbopogon citratus) essential oil in eradicating Candida albicans biofilm pre-established on the maxillofacial silicone specimens.

Materials and Methods:

Two maxillofacial silicones, namely, MDX4-4210 and Multisil Epithetik, were used for the fabrication of 6 mm diameter disks (n = 21 for each brand of silicone). A 48-h mature C. albicans ATCC 10231 biofilm was pre-established on sterile silicone specimen. These disks were then exposed to various concentrations of lemongrass essential oil ranging from 0.31% to 5% (v/v), 20% (v/v) nystatin, and RPMI-1640 medium for 18–20 h. After exposure, the remaining viable fungal biofilm was examined by the XTT [2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide]-reduction assay. All data were analyzed by using a regression coefficient and a post hoc Tukey HSD multiple comparisons test (α = 0.05).

Results:

Different brands of silicone used for fabrication did not significantly affect the formation of mature C. albicans biofilm (P =0.302). A 5% (v/v) lemongrass essential oil significantly eliminated fungal biofilm by approximately 95% (P =0.031). However, less than 50% of the fungal biofilm was eliminated by the tested oil at a concentration as low as 0.31% (v/v). Furthermore, the fungicidal efficacy against C. albicans biofilm of lemongrass essential oil at 2.5% (v/v) was as potent as that of 20% (v/v) nystatin suspension (P = 0.99).

Conclusion:

Lemongrass essential oil expressed fungicidal effect on C. albicans biofilm pre-established on the disks fabricated from different brands of silicone. Additionally, the fungicidal effectiveness of the oil against the mature fungal biofilm was dose-dependent.

A Literature Review on Biofilm Formation on Silicone and Poymethyl Methacrylate Used for Maxillofacial Prostheses

Silicone elastomers are considered the most suitable maxillofacial materials for extraoral prostheses to date due to their superior physicochemical properties. The aim of this review was to describe the characteristics of biofilm formation on silicone and polymethyl methacrylate used for maxillofacial prostheses and review different strategies of biofilm management for silicone maxillofacial prosthesis. A structured literature search was conducted using the following databases - PubMed, Google Scholar, ScienceDirect, LILACS, IndeMED, OVID, EMBASE, NIH Clinical Trials - for reports related to the biofilms. English language articles were only included in the study. Biofilms induced various systemic infections if they are not treated at an early stage. Biofilms are formed due to various reasons like fungal, bacterial and mixed infections of the patient and also due to prosthetic appliances. The manual or mechanical pressure physically removes the biofilm and most biofilm molecules from surfaces. Treatment must be given with utmost caution and concern irrespective of the presence or absence of biofilm. With regards to the materials used for fabricating maxillofacial substitutes, it has been defined that both acrylic resin and silicone may harbour microorganisms, however, the larger porosities in silicone make it vulnerable to microbial adhesion. The major limitations of these materials are that they have numerous porosities on their surface and, along with the modification of the anatomy of the facial tissues as a result of the lesion, may compromise the natural balance of the microbial flora, favouring microbial colonization and formation of biofilms.

Ultraviolet C as a method of disinfecting medical silicone used in facial prostheses: An in vitro study

STATEMENT OF PROBLEM

Hygiene and disinfection are important factors for preserving facial prostheses and supporting tissue health. However, a method that does not accelerate degradation or color change is necessary.

PURPOSE

The purpose of this in vitro study was to evaluate the effectiveness of irradiation with ultraviolet C light-emitting diode (UV-C LED) light in the disinfection and initial color stability of the silicone (A-588-1; Factor II) used in facial prostheses.

MATERIAL AND METHODS

One hundred and twenty specimens were made, contaminated by multispecies biofilm, and divided into 5 groups (n = 24) with different treatments: control, distilled water, 0.12% chlorhexidine, UV-C LED light, and dimethyl sulfoxide (DMSO) as the negative control. Cell viability was measured by the methyl tetrazolium salt method. Statistical analysis was performed by generalized linear models. Additional descriptive analysis was performed for color analysis by using 16 silicone specimens made with light and dark intrinsic coloring in 4 groups (controls and treatments n=4) submitted to UV-C LED light. The ΔE of the specimens was obtained by CIEDE200.

RESULTS

The results of cell viability demonstrated a statistically significant difference among the groups (P<.001), with a microbial reduction after UVC-LED exposure compared with the control group. Regarding the color, the groups presented an average ΔE (light 0.205 and dark 0.308) compatible with visually imperceptible changes (light < 0.7 and dark < 1.2).

CONCLUSIONS

Irradiation with UV-C LED light decreased the in vitro microbial cell viability of the medical silicone used in facial prostheses, demonstrating initial color stability.

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.

Efficacy of incorporating silver nanoparticles into maxillofacial silicone against Staphylococcus aureus, Candida albicans, and polymicrobial biofilms

STATEMENT OF PROBLEM

The presence of biofilms on maxillofacial silicone increases the risk of infections and reduces durability. Whether silver nanoparticles (AgNPs) with potent antimicrobial effects help reduce biofilm formation is unclear.

PURPOSE

The purpose of this in vitro study was to assess the antimicrobial effect of sub 10-nm AgNPs in maxillofacial silicone against Staphylococcus aureus, Candida albicans, and mixed species biofilms containing both and to test the effectiveness of different AgNP concentrations against all 3 biofilms in vitro.

MATERIAL AND METHODS

Silicone disks (M511; Technovent Ltd) containing 0.0% (control), 0.1%, and 0.5% AgNPs were fabricated and treated with S. aureus, C. albicans, and mixed species strains of both in 24-well culture plates containing appropriate media. Each well received a 0.1-mL aliquot of the standardized suspension of microorganisms. The plates were incubated for 21 consecutive days, and colony-forming units per milliliter (CFU/mL) were measured on the first, third, fifth, seventh, fifteenth, and twenty-first day with the Miles and Misra method. Data were analyzed by 2-way ANOVA and the paired t test to evaluate the relationship between AgNP concentration, microbial strain, and time (α=.05). Mean CFU/mL differences for each time and for each biofilm category were assessed by repeated measure ANOVA.

RESULTS

AgNPs decreased the mean CFU/mL in both concentrations compared with the control. The 0.1% concentration showed sustained efficacy throughout the test, while the 0.5% concentration had high efficacy initially with a gradual decrease. However, the results were inconsistent for the mixed biofilm. The paired sample t test at day 3 and 15 and day 3 and 21 showed statistically significantly different results (P<.001) in all but 1 group in the 0.5% concentration. The 2-way mixed ANOVA showed statistically significant (P<.001) interaction between AgNP concentration and time in all groups. The 1-way ANOVA of AgNP concentrations was statistically significantly different (P<.001) for all time points. A statistically significant (P<.001) effect of time on CFU/mL was found for all the AgNP concentration groups in all 3 biofilms.

CONCLUSIONS

Silicone elastomers with sub 10-nm AgNPs displayed antimicrobial properties in vitro against S. aureus, C. albicans, and mixed species strains. AgNPs (0.1%) were effective against both microbial strains and can provide a baseline for further long-term studies regarding antimicrobial efficacy, silver ion leaching, and cellular internalization. Mixed species biofilm needs further exploration with standardized study parameters.

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.

Biofilm Growth Causes Damage to Silicone Voice Prostheses in Patients after Surgical Treatment of Locally Advanced Laryngeal Cancer

Voice prosthesis implantation with the creation of a tracheoesophageal fistula is the gold standard procedure for voice rehabilitation in patients after a total laryngectomy. All patients implanted with a voice prosthesis (VP) have biofilms of fungi and bacteria grow on their surface. Biofilm colonization is one of the main reasons for VP degradation that can lead to VP dysfunction, which increases the high risk of pneumonia. In a 20-month evaluation period, 129 cases of prostheses after replacement procedures were investigated. Microbiological examination of the biofilms revealed that there were four of the most common fungi species (Candida spp.) and a large variety of bacterial species present. We studied the relationship between the time of proper function of Provox VP, the microorganism composition of the biofilm present on it, and the degradation level of the silicone material. Evaluation of the surface of the removed VP using an atomic force microscope (AFM) has demonstrated that biofilm growth might drastically change the silicone's mechanical properties. Changes in silicone stiffness and thermal properties might contribute to the failure of VP function. Our data can serve in future studies for the development of methods to prevent or inhibit biofilm formation on the VP surface that would translate to an increase in their durability and safety.

Advancements in Soft-Tissue Prosthetics Part B: The Chemistry of Imitating Life

Each year, congenital defects, trauma or cancer often results in considerable physical disfigurement for many people worldwide. This adversely impacts their psychological, social and economic outlook, leading to poor life experiences and negative health outcomes. In many cases of soft tissue disfigurement, highly personalized prostheses are available to restore both aesthetics and function. As discussed in part A of this review, key to the success of any soft tissue prosthetic is the fundamental properties of the materials. This determines the maximum attainable level of aesthetics, attachment mechanisms, fabrication complexity, cost, and robustness. Since the early-mid 20th century, polymers have completely replaced natural materials in prosthetics, with advances in both material properties and fabrication techniques leading to significantly improved capabilities. In part A, we discussed the history of polymers in prosthetics, their ideal properties, and the application of polymers in prostheses for the ear, nose, eye, breast and finger. We also reviewed the latest developments in advanced manufacturing and 3D printing, including different fabrication technologies and new and upcoming materials. In this review, Part B, we detail the chemistry of the most commonly used synthetic polymers in soft tissue prosthetics; silicone, acrylic resin, vinyl polymer, and polyurethane elastomer. For each polymer, we briefly discuss their history before detailing their chemistry and fabrication processes. We also discuss degradation of the polymer in the context of their application in prosthetics, including time and weathering, the impact of skin secretions, microbial growth and cleaning and disinfecting. Although advanced manufacturing promises new fabrication capabilities using exotic synthetic polymers with programmable material properties, silicones and acrylics remain the most commonly used materials in prosthetics today. As research in this field progresses, development of new variations and fabrication techniques based on these synthetic polymers will lead to even better and more robust soft tissue prosthetics, with improved life-like aesthetics and lower cost manufacturing.

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.

Mechanical and Morphological Effect of Plant Based Antimicrobial Solutions on Maxillofacial Silicone Elastomer

The objective of this study was to determine the effect of plant based antimicrobial solutions specifically tea tree and Manuka oil on facial silicone elastomers. The purpose of this in vitro study was to evaluate the effect of disinfection with plant extract solution on mechanical properties and morphology on the silicone elastomer. Test specimens were subjected to disinfection using tea tree oil, Manuka oil and the staphylococcus epidermidis bacteria. Furthermore, a procedure duration was used in the disinfection process to simulate up to one year of usage. Over 500 test specimens were fabricated for all tests performed namely hardness, elongation, tensile, tear strength tests, visual inspection and lastly surface characterization using SEM. A repeated measures ANOVA revealed that hardness and elongation at break varied significantly over the time period, whereas this was not observed in the tear and tensile strength parameters of the test samples.

Genomic identification of microbial species adhering to maxillofacial prostheses and susceptibility to different hygiene protocols

This study investigated the microbial colonization of maxillofacial prostheses and support tissues using the Checkerboard DNA-DNA hybridization method, and the efficacy of 0.12% chlorhexidine gluconate, 10% Ricinus communis solutions, or brushing, on colony forming unit (CFU) reduction in monospecies biofilms (Candida glabrata, Staphylococcus aureus, Streptococcus mutans, Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa) formed on two silicones (MDX 4-4210 and Bio-Skin). Biofilm was harvested from 43 maxillofacial prosthesis wearers for detection of 38 species of microorganisms. The CFU counts of the six above mentioned species were recorded after using the hygiene protocols. All 38 investigated species were identified in prostheses and tissues, with a higher prevalence in the prostheses. 0.12% chlorhexidine gluconate immersion showed the greatest antimicrobial effectiveness, followed by mechanical brushing protocols. MDX 4-4210 silicone produced lower CFU counts than Bio-Skin.

Treatment of a chronically infected nasal silicone prosthesis with continuous antibiotic irrigation and gentamicin-impregnated polymethylmethacrylate beads

Infected nasal alloplasts in revision rhinoplasty can be a complex problem, as timing between implant removal and reconstruction is the major limiting factor. Delaying reconstruction can result in loss of mechanical support, a constricted nose, and in severe cases, complete nasal airway collapse and respiratory compromise. In this case report, we describe a novel surgical approach for the management of a chronically infected nasal implant combining techniques used to treat biomaterial-associated infections: antibiotic-impregnated polymethymethacrylate beads and a continuous catheter-based antibiotic irrigation system.

We report a case of a chronic alloplastic-associated infection following nasal reconstruction using a silicone implant. We utilized a two-staged approach. The involved nasal implant was removed and replaced temporarily with gentamicin-impregnated polymethymethacrylate beads and a continuous closed irrigation and drainage system with local and parenteral delivery of antibiotics. Both modalities allowed for complete eradication of the infection. In addition, the gentamicin beads provided sufficient mechanical support in order to minimize the risk of skin contracture. Twelve days after her initial surgery, nasal reconstruction was performed using a cadaver bone graft. The patient was followed for two years postoperatively and has shown good results with no evidence of skin contracture or recurrent infection. This technique may allow for shorter delay in revision surgery and reduce the risk of long-term complications without compromising functional and aesthetic outcomes.

Combination prosthetic design providing a superior retention for mid-facial defect rehabilitation: A Case Report

Large maxillofacial defects from malignant tumor treatment are rarely rehabilitated by surgical reconstruction alone. Ameloblastic carcinoma, a rare aggressive odontogenic malignant tumor, requires wide surgical excision to gain a tumor-free margin. In the post-surgical defect, prosthetic rehabilitation is the treatment of choice to restore function and esthetics. Moreover, an intra-oral prosthesis such as an obturator restores speech, mastication and deglutition. Retention of the obturator is a major problem while rehabilitating large defects. The existing anatomical structures from the defect with the help of magnet attachments are suitable to enhance retention, stability and support of the prostheses. This case report presents a patient with an intraoral and extra-oral combination defect following surgical resection of ameloblastic carcinoma and describes the prosthetic techniques and design considerations for a magnet-retained obturator and mid-facial prosthesis. An implant-retained mid-facial prosthesis was fabricated. The retention of combined prostheses was obtained from the remaining right posterior teeth only. The patient had an unfavorable defect due to the large size and presence of scar contracture that vertically tends to dislodge the obturator. Magnet attachments were used to combine the facial and oral prosthesis, minimize the vertical dislodging forces and enhance retention. In addition, the retention was also gained from the scar band at lower border of mid-facial defect that avoided the need for more implants surgery. Magnet attachment with anatomical structure of the mid-facial defect provides an acceptable means of retention in large extraoral-intraoral combinations defects, improving the function, esthetic and the patients' quality of life. Key words:Mid-facial prosthesis, obturator, magnet attachment, maxillectomy.

Identification of proteins involved in the adhesionof Candida species to different medical devices

Adhesion is the first step for Candida species to form biofilms on medical devices implanted in the human host. Both the physicochemical nature of the biomaterial and cell wall proteins (CWP) of the pathogen play a determinant role in the process. While it is true that some CWP have been identified in vitro, little is known about the CWP of pathogenic species of Candida involved in adhesion. On this background, we considered it important to investigate the potential role of CWP of C. albicans, C. glabrata, C. krusei and C. parapsilosis in adhesion to different medical devices. Our results indicate that the four species strongly adher to polyvinyl chloride (PVC) devices, followed by polyurethane and finally by silicone. It was interesting to identify fructose-bisphosphate aldolase (Fba1) and enolase 1 (Eno1) as the CWP involved in adhesion of C. albicans, C. glabrata and C. krusei to PVC devices whereas phosphoglycerate kinase (Pgk) and Eno1 allow C. parapsilosis to adher to silicone-made implants. Results presented here suggest that these CWP participate in the initial event of adhesion and are probably followed by other proteins that covalently bind to the biomaterial thus providing conditions for biofilm formation and eventually the onset of infection.

The clinical importance of fungal biofilms

Fungal biofilms have become an increasingly important clinical problem. The widespread use of antibiotics, frequent use of indwelling medical devices, and a trend toward increased patient immunosuppression have resulted in a creation of opportunity for clinically important yeasts and molds to form biofilms. This review will discuss the diversity and importance of fungal biofilms in the context of clinical medicine, provide novel insights into the clinical management of fungal biofilm infection, present evidence why these structures are recalcitrant to antifungal therapy, and discuss how our knowledge and understanding may lead to novel therapeutic intervention.

Recommendations for implant-retained nasal prostheses after ablative tumor surgery: Minimal surgical aftercare, high implant survival, and satisfied patients

BACKGROUND

Nasal defects resulting from tumor resection are preferably rehabilitated with implant-retained nasal prostheses. Aftercare, clinical outcome of the implants, and patients' satisfaction with implant-retained nasal prostheses were assessed.

METHODS

Twenty-eight consecutive patients needing total rhinectomy because of tumor resection between 1998 and 2013 were treated according to a standardized protocol with 2 implants in the nasal floor. Surgical and prosthetic aftercare was scored using patient records. Finally in 2014, skin reaction, peri-implant bone loss, and patients' satisfaction were assessed in all 13 still living patients.

RESULTS

In total, 56 implants were inserted (median follow-up, 35.1 months; interquartile range [IQR], 8.9-63.3). Implant survival was 96.4%. Implant survival was independent of radiotherapy. Peri-implant skin was healthy and patients' satisfaction high. Longevity of the prostheses was limited.

CONCLUSION

Rehabilitation of nasal defects resulting from total rhinectomy with implant-retained nasal prostheses, according to our protocol, resulted in high patient satisfaction and favorable treatment outcome. © 2015 Wiley Periodicals, Inc. Head Neck 38: E-E, 2016.

Efficacy of cleansing agents in killing microorganisms in mixed species biofilms present on silicone facial prostheses--an in vitro study

OBJECTIVES

The purpose of this study was to assess the efficacy of different cleansing agents in killing mixed species biofilms on silicone facial prostheses.

MATERIALS AND METHODS

Two bacterial and three yeast strains, isolated from silicone facial prostheses, were selected for the mixed species biofilms. A variety of agents used to clean facial prostheses were employed, viz., antibacterial soap, essential-oil-containing mouth rinse, ethanol 27 %, chlorhexidine mouth rinse, and buttermilk. Colony forming units (CFUs) and live/dead staining were analyzed to assess the efficacy of these cleansing agents against 24-h and 2-week biofilms and regrown biofilms on silicone samples.

RESULTS

Chlorhexidine was the most effective cleansing agent. Chlorhexidine killed 8 log unit CFUs (>99.99 % killing) in a 24-h biofilm and 5 log unit CFUs (>99.99 % killing) in 2-week biofilms. Also, after regrowth and repeated treatment of the biofilm, chlorhexidine was the most effective cleansing agent showing no detectable CFUs. The essential-oil-containing mouth rinse (containing 26.9 % ethanol) showed a similar efficacy as ethanol (27 %) alone. Antibacterial soap and buttermilk were the least effective agents tested.

CONCLUSIONS

Chlorhexidine showed the highest reduction in CFUs in 24-h, 2-week, and regrown mixed species biofilm of microorganisms isolated from silicone facial prostheses.

CLINICAL RELEVANCE

Chlorhexidine mouth rinse (easy obtainable and relatively cheap) is very effective in killing bacteria and yeast present in biofilms on silicone facial prostheses. When applied on a regular basis, cleansing a facial prosthesis with chlorhexidine will presumably increase its lifetime and reduce skin irritations.

In-vitro Analysis of Antifungal Activity of Epigallocatechin-Gallate: Preliminary Study

Oral candisosis is an heterogeneous group of diseases, caused by different species of Candida fungus. The incidence of drug-resistant species is increasing dramatically; furthermore, in recent years higher incidences of non-albicans and antimycotic-resistant species of Candida have been reported, thus increasing necessity of a non-antibiotic agent, which should be both highly effective and safe. It has been showed that the main polyphenols component of green tea, epigallocatechin-gallate (EGCG), has antibacterial activity; recently, it has been reported its antifungal activity too. We tested the effectiveness of a 0.20% EGCG (TEAVIGO®) gel, a non-pharmaceutical product suitable for oral in vivo use, on four species of Candida yeast (C.albicans, Cparapsilosis, C.tropicalis, C.glabrata), evaluating its antifungal activity and its capacity to inhibit biofilm formation. The EGCG gel showed a remarkable activity against C. parapsilosis and C. tropicalis. This preliminary study confirms EGCG effectiveness on fungi; for this reason, a product with such a low concentration of EGCG could be used with no side-effect for every-day oral hygiene. Anyway, mechanisms of antifungal activity of EGCG are not comprehended and need further studies to better understand the reasons of some Candida species' resistance.

Antibiotic susceptibility and resistance of Staphylococcus aureus isolated from fresh porcine skin xenografts: risk to recipients with thermal injury

The previous use of fresh porcine xenografts at the Prague Burn Centre had raised concerns over the transmission of zoonotic pathogens. This study examines the risk of zoonotic Staphylococcus aureus colonisation of burn patients from fresh porcine skin xenografts. Samples were collected from the nares, skin and perineum of commercial pigs (n=101) and were screened for methicillin sensitive S. aureus (MSSA) and resistant S. aureus (MRSA). The efficacy of the antibiotic wash used in decontamination of the pigskin was tested against planktonic- and biofilm-grown isolates. The spa type of each isolate was also confirmed. All pig swabs were negative for MRSA but 86% positive for MSSA. All planktonic-grown isolates of MSSA were sensitive to chloramphenicol and nitrofurantoin and 44% of isolates were resistant to streptomycin. Isolates grown as biofilm exhibited higher rates of antimicrobial resistance. Sequence analysis revealed three distinct spa types of the MRSA ST398 clonal type. This finding demonstrates the existence of a MSSA reservoir containing spa types resembling those of well-known MRSA strains. These MSSA exhibit resistance to antibiotics used for decontamination of the pigskin prior to xenograft. Amended use of procurement could allow the use of fresh pigskin xenografts to be reinstated.