Influence of opacifiers on dimensional stability and detail reproduction of maxillofacial silicone elastomer

Frequently used extraoral maxillofacial prosthetic materials and their longevity - A comprehensive review

The longevity of an extraoral prosthesis depends on its physical and mechanical properties and user maintenance. Faced with multiple outcome measures, researchers find it difficult to determine the most appropriate extraoral prosthetic material. This comprehensive review evaluates the most used extraoral prosthesis materials and qualitatively assesses their longevity and function. The study aims to identify and interpret the results of current updates on the factors that affect longevity and functionality. This comprehensive review summarizes and evaluates differences in the properties of commonly used extraoral maxillofacial prosthetic materials. The review was planned to focus on all factors related to the longevity and function of the extraoral maxillofacial prosthetics. An electronic search covered English articles in PubMed, Scopus, Google Scholar, Web of Science, and grey literature. Manual searching was also performed. Six authors participated in the screening. Search engines extracted 1107 records, and 88 studies were included for qualitative and bias assessments. Silicones are the most frequently used extraoral maxillofacial prosthetic materials. Heat-cured silicones are more color-stable than those cured at room temperature. Additional ingredients and processing techniques affect prosthesis longevity.

Efficacy of an impression disinfectant solution after repeated use: An in vitro study

Statement of problem

There are very few studies using Benzalkonium Chloride (BAC) as an active disinfection agent for immersion techniques and there are no studies investigating the efficacy of repeated use of a disinfectant solution.

Purpose

This study evaluated an impression disinfectant by testing bacterial contamination of disinfectant batches used in a clinical setting after repeated use.

Materials and methods

Liquid samples were collected from impression disinfectant solutions used to disinfect dental impressions taken at a university dental clinic. The experimental samples (500 ml from 1 L of solution) were collected from teaching and professional clinics and the in-house commercial processing laboratory and stored at room temperature each day of clinic operation over five weeks. To determine to what extent the disinfectant efficacy of the active product decreased over time, the following tests were carried out: a. Inoculation b. Gram staining technique c. Matrix Assisted Laser Desorption/Ionization Mass spectrometry (MALDI- MS). Microbial growth was monitored and photographed. A culture revival was made from colonies grown on sheep blood agar, to isolate pure colonies incubated for 24 h at 37 °C. Each morphologically distinct type of colony was gram stained and MALDI spectrometry analysis was performed using the VITEK MS (BioMerieux Inc.).

Results

Evidence of growth of bacteria was detected in teaching clinics' samples, and no growth from the professional clinic or the commercial laboratory.

Conclusions

The study demonstrated that impression disinfectanat solution tested is effective against common oral bacteria, despite some rare species such as Bacillus circulans, Bacillus horneckiae, Bacillus altitudinis/pumilus and Bacillus cereus showing evidence of survival in solutions used for disinfection of impressions. However, in a high use teaching clinic environment its efficacy deteriorated. Though a second level disinfection protocol in the commercial laboratory-maintained impression disinfection.

Evaluation of the Mechanical and Physical Properties of Maxillofacial Silicone Type A-2186 Impregnated with a Hybrid Chitosan-TiO2 Nanocomposite Subjected to Different Accelerated Aging Conditions

The effects of incorporating a pioneer chitosan-TiO2 nanocomposite on the mechanical and physical properties of room-temperature vulcanization (RTV) maxillofacial A-2186 silicone under accelerated aging protocols were rigorously examined. This investigation utilized 450 samples distributed across five distinct silicone classifications and assessed their attributes, such as tensile strength, elongation, tear strength, hardness, and surface roughness, before and after various accelerated aging processes. Statistical methodologies, including a one-way ANOVA, Tukey's HSD, and Dunnett's T3, were employed based on the homogeneity of variance, and several key results were obtained. Silicones infused with 1 wt.% chitosan-TiO2 showed enhanced tensile strength across various aging procedures. Moreover, the 1 wt.% TiO2/Chitosan noncombination (TC) and 2 wt.% TiO2 compositions exhibited pronounced improvements in the elongation percentage. A consistent rise was evident across all silicone categories regarding tear strength, with the 1 wt.% chitosan-TiO2 variant being prominent under certain conditions. Variations in hardness were observed, with the 1 wt.% TC and 3 wt.% chitosan samples showing distinctive responses to certain conditions. Although most samples displayed a decreased surface roughness upon aging, the 1 wt.% chitosan-TiO2 variant frequently countered this trend. This investigation provides insights into the potential of the chitosan-TiO2 nanocomposite to influence silicone properties under aging conditions.

Effect of Extrinsic Pigmentation on Dimensional Stability, Hardness, Detail Reproduction, and Color of a Silicone

OBJECTIVE

 The aim of the study is to evaluate the effect of extrinsic pigmentation on the dimensional stability, hardness, detail reproduction, and color of a silicone after thermocycling.

MATERIALS AND METHODS

 Sixty samples of MDX4-4210 silicone (Dow Corning Corporation Medical Products) with intrinsic pink pigment (H-109-P, Factor II) and intrinsic opacifier (TiO) were fabricated. Two groups were created: Group 1-only intrinsic pigmentation (H-109P, Factor II + TiO) (Control); and Group 2-intrinsic (H-109P, Factor II + TiO) and extrinsic (Tan FE - 215, Factor II) pigmentation. The following tests were performed for each group: dimensional stability, Shore A hardness, detail reproduction, and color. Readings for the tests were taken before and after thermocycling (2,000 cycles). For dimensional stability and hardness, two-way analysis of variance (ANOVA) was used. One-way ANOVA was used for the color test. In case of significant statistical difference, the Tukey test was applied (p <0.05). All samples achieved the same detail reproduction score, therefore, no statistical evaluation was performed.

RESULTS

 For the dimensional stability test, comparing the initial time with the final time, there was a significant contraction in both groups after thermocycling. For the hardness test, comparing the time points, only group 1 showed a significant reduction in hardness after thermocycling. Groups 1 and 2 scored 2 for the detail reproduction test, before and after thermocycling. Comparing group 1 with group 2, there was no significant difference for color change.

CONCLUSION

 Based on the tests performed, extrinsic pigmentation did not show a negative effect on silicone, and therefore it can be indicated. The results of the dimensional, hardness, detail reproduction and color evaluations of the MDX4-4210 silicone were clinically acceptable in all cases in the groups with and without extrinsic pigmentation.

Investigation of the effects of different nanoparticle additionals on the mechanical properties of silicone elastomer used in maxillofacial prosthesis

Objective: The aim of this study is to evaluate the change in the mechanical properties of silicone elastomer used in the production of maxillofacial prostheses with the addition of 3 different nanoparticles (TiO2-SiO2-ZnO). Material and Method: TiO2-SiO2-ZnO nanoparticles were added to the A part of the M511 Platinum (Technovent Ltd., England) silicone elastomer at a rate of 2% by weight. Test specimens were produced in sizes by ASTM D412 standards for tensile strength and percent elongation, ASTM D624 for tear strength, and ASTM D2240-68 for hardness testing. For each mechanical test, 4 groups were formed together with the control group and 3 other groups to which nanoparticles were added, and a total of 132 samples were produced, 11 samples for each group (n=11), (N=132). The data of tensile strength, elongation percentage, and tear strength tests were analyzed by Shapiro Wilk's and/or Kolmogorov Smirnov/Mann Whitney U, Kruskal Wallis-H tests; for the hardness test, the values ​​in each group showed a normal distribution within themselves, hardness test was analyzed with Oneway ANOVA/Tukey HSD tests. Results: The addition of TiO2 and SiO2 to the silicone elastomer significantly increased the tensile strength compared to the other groups (p

Effect of Superhydrophobic Coating and Nanofiller Loading on Facial Elastomer Physical Properties

Facial prosthetics are currently constructed of materials that are far from optimal; superior materials with a “skin-like” feel are required. In this study, the property changes brought about by the consecutive additions of hydrophobic- and uncoated nano-SiO2 to polydimethylsiloxane (PDMS) are assessed, and the alterations are compared with those observed for conventional submicron SiO2-filled materials. In sequence, 0%, 0.5%, 5%, 10%, and 15% by weight of each filler type were successively added to vinyl-terminated PDMS. Tensile, tear, Durometer hardness, translucency, and viscoelastic properties were assessed, and hardness and translucency were further measured after 3000 h of outdoor weathering. The results showed that 15% coated nano- SiO2-filled PDMS materials given the highest tensile strength, elastic modulus, storage modulus, loss modulus, tear strength, and durometer hardness (p < 0.05), whereas 15% submicron coated SiO2-filled materials displayed the highest failure strain and translucency parameter (p < 0.05). Only 10%- and 15%-filled submicron SiO2 PDMS materials were altered by outdoor weathering; nevertheless, the increases were assessed to be too small to be clinically perceptible. As increased filler levels provided protection against solar radiation, heat, and moisture, only unfilled and 0.5%-filled PDMS formulations discolored from weathering. 15%-filled superhydrophobic-coated nano- SiO2-filled PDMS was found to produce the strongest, most tear-resistant, and least translucent materials, but it also produced materials with limited stretchability and high hardness, which were regarded to be downsides for creating a “skin-like” feel.

Chlorhexidine as a Disinfectant in the Prosthodontic Practice: A Comprehensive Review

INTRODUCTION

Controlling the cross-contamination between the dental clinic and laboratory is of utmost importance to maintain the health of dental healthcare personnel (DHCP) and patients. The aim of this paper was to review the current literature with regard to the use of chlorhexidine as a prosthetic disinfectant in prosthodontic practice.

MATERIALS AND METHODS

A scoping review of the literature was performed in Medline/PubMed, Ovid Embase, and the Cochrane Library. A search for all literature published from 1980 to 2021 was based on the following keywords: ['Chlorhexidine/gluconate' OR 'chlorhexidine', OR 'gluconate', OR 'denture disinfectants', OR 'antimicrobial', OR 'disinfectant', OR 'impression disinfectants, OR prosthesis' OR 'biofilm, microbiology'] OR [teeth]. We reviewed the disinfectant in terms of its mechanism of action, antimicrobial effectiveness, disinfection techniques, clinical applications, corrosiveness/damage to the structure of prostheses, and reasonable shelf life.

RESULTS

Chlorhexidine was tested under different concentrations ranging from 0.2 to 5%. It provided a significant reduction in biofilm viability but had a minimum effect on Candida albicans with a variable effect result that showed no significant differences in the dimensional changes by immersion of alginate dental impressions for no more than 10 minutes and no clinically significant dimensional differences on aluwax, polyether, condensation siloxane, and polyvinyl siloxane were noticed. Nonetheless, chlorhexidine altered the surface of the silicone and acrylic resins and affected the long-term hardness of the relining material.

CONCLUSION

Within the limitations of this review, the use of chlorhexidine disinfectant demonstrates a good measure in the reduction of contamination and cross-infection and has a minimal effect on the dimensional stability of most impression materials. Further studies with in-vitro testing are required to confirm these findings.

Effects of Disinfection Methods on the Color Stability of Precolored and Hand-Colored Maxillofacial Silicone: An In Vitro Study

Maxillofacial prostheses are used in rehabilitation of patients with facial defects. Typically, these prostheses are fabricated with medical grade silicone and are tinted corresponding to the patients' natural skin color. However, exposure to environment and disinfectants can result in color changes. This study aimed to evaluate the effects of four different disinfection methods on the color stability of precolored and hand-colored maxillofacial silicones. Forty specimens each of precolored and hand-colored silicone were prepared. The specimens were randomly divided into eight groups (n = 10) and cleansed with four different disinfection methods. Disinfection was carried out six times/day for 60 days, simulating once-a-day disinfection for a year. Color evaluation was carried out at day 0 and day 60 using a UV-vis spectrophotometer. Color alterations were calculated by the CIE L ^∗ a ^∗ b ^∗ system. Data were analyzed by two-way ANOVA with post hoc Tukey HSD and t-tests (α = 0.05). Disinfectants can affect the color stability of maxillofacial silicone. In our study, chlorhexidine solution and liquid soap resulted in the highest color change. Precolored silicone showed higher color stability than its hand-colored counterpart.

Influence of Different Pigmentations and Accelerated Aging on the Hardness and Tear Strength of the A-2186 and MDX4-4210 Silicones

Objective

To evaluate the influence of different pigmentations and accelerated aging on the hardness and tear strength of the A-2186 and MDX4-4210 silicones.

Materials and Methods

The samples A-2186 and MDX4-4210 were manufactured without and with pigmentations (black, bronze, and pink). For the Shore A hardness test, 80 samples of each silicone were fabricated, and for the tear strength test, 320 samples of each silicone were fabricated. Eight groups were created for each test (n = 10). These tests were performed before and after 252, 504, and 1008 hours of aging. Three-way repeated-measures analysis of variance and the Tukey test were performed (α = 0.05).

Results

The A-2186 silicone showed higher hardness and tear strength when compared with the MDX4-4210 silicone (p < 0.05), except in the hardness of the A-2186 and MDX4-4210 groups without pigmentation after 1008 hours (p > 0.05). All hardness values were between 25 and 35 units, regardless of the silicone type, period, and pigmentation (or no pigmentation). In most situations, the hardness of silicones used increased after 252 hours (p < 0.05). The nonpigmented MDX4-4210 group and all A-2186 groups showed an increase in tear strength after 252 hours (p < 0.05). For the nonpigmented MDX4-4210 group, from 252 to 1008 hours, there was no change in tear strength (p > 0.05). All pigmented MDX4-4210 groups showed no change in tear strength from 0 (initial) to 1008 hours of aging (p > 0.05). In all A-2186 groups, from 252 to 504 hours, there was a reduction in tear strength (p < 0.05), and from 504 to 1008 hours, there was an increase in tear strength (p < 0.05), except in the bronze A-2186 group (p > 0.05).

Conclusion

In most situations, the A-2186 silicone showed significantly higher values of hardness and tear strength than the MDX4-4210 silicone. All hardness values were considered clinically acceptable. Accelerated aging could increase, decrease, or not significantly change the hardness and tear strength of the silicones used. The results of hardness and tear strength suggest that MDX4-4210 was more influenced by the presence of pigmentation after aging.

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.

Influence of Different Pigment Incorporation Methods on Color, Dimensional Stability, and Detail Reproduction of Silicones

Objective  To analyze the influence of three pigment incorporation methods on color change, dimensional stability, and detail reproduction of the MDX4–4210 and A-2186 silicones.

Materials and Methods  The A-2186 and MDX4–4210 silicones were used for preparation of samples, with the incorporation of bronze, black and pink pigments, usingconventional, mechanical, and industrial incorporation methods. Samples were submitted to the initial readings of color ( n = 10; 22-mm diameter × 2-mm thickness), detail reproduction, and dimensional stability ( n = 10; 30-mm diameter × 3-mm thickness). Readings were also taken at the end of 252, 504 and 1,008 hours of aging cycles.

Results  Quantitative data were evaluated by ANOVA and Tukey test, with a level of significance of 5%. The mechanical and industrial methods caused smaller color changes of all samples compared with the conventional method ( p < 0.05). In most cases, the mechanical and industrial methods caused less samples’ contraction than the conventional method after aging ( p < 0.05). The color change values increased progressively in each aging period for all samples ( p < 0.05). The contraction values increased progressively in each aging period for all samples ( p < 0.05). In the qualitative analysis of detail reproduction, all samples presented full reproduction of the three grooves, with accurate angles, initially and after the aging periods.

Conclusions  The industrial and mechanical methods showed the best results for color and dimensional stability. Despite the statistical differences, all pigment incorporation methods generated acceptable dimensional and color changes of the MDX4-4210 and A-2186 silicones, regardless of the pigment and aging. In addition, the detail reproduction was satisfactory after aging periods in all cases of this study, showing the excellent quality of the A-2186 and MDX4–4210 silicones.

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.

Influence of adding nanoparticles on the hardness, tear strength, and permanent deformation of facial silicone subjected to accelerated aging

STATEMENT OF PROBLEM

The efficiency of adding nanoparticles to silicone protection has proven to prevent color degradation. However, reports of other physical property changes in facial silicone are scarce.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of adding nanoparticles on the hardness, tear strength, and permanent deformation of a facial silicone.

MATERIAL AND METHODS

Specimens were made for each test, with 140 for the hardness test, 140 for the permanent deformation test, but 280 for the rupture test. This higher number was due to the fact that the first 140 specimens were ruptured and unusable after the initial reading. ZnO, BaSO₄, and TiO₂ nanoparticles at concentrations of 1% and 2% of silicone were used, as well as specimens without nanoparticles that consisted of only oil paint and of only silicone. Outcomes were measured before and after 1008 hours of accelerated aging. Data were analyzed by nested analysis of variance (ANOVA) and Tukey honest significant differences test (α=.05).

RESULTS

Results showed that the presence of nanoparticles influenced the properties of the assessed groups. The nanoparticles decreased hardness values. The highest values of tear strength were observed for the groups with addition of BaSO₄. The 1% ZnO group without oil paint showed the lowest values of permanent deformation.

CONCLUSIONS

Based on the findings of this in vitro study, the use of ZnO nanoparticles is recommended, since they did not negatively affect the properties of the materials evaluated.

Antimicrobial activity of conventional and plant-extract disinfectant solutions on microbial biofilms on a maxillofacial polymer surface

STATEMENT OF PROBLEM

Dentists often note problems with infection in patients with maxillofacial prostheses. Conventional disinfection protocols are not always effective and may alter the properties of the polymer used in the prosthesis. Thus, the search for improved disinfection methods is important.

PURPOSE

The purpose of this in vitro study was to evaluate and compare the antimicrobial activity of conventional disinfectant solutions (water and neutral soap and 4% chlorhexidine) and plant extracts (Cymbopogon nardus and Hydrastis canadensis) on specimens of maxillofacial silicone contaminated with Candida albicans and Staphylococcus aureus biofilms.

MATERIAL AND METHODS

Seventy-two silicone (MDX4-4210) specimens were fabricated (5×2 mm) and sterilized. Thirty-six were contaminated with C albicans (10(6) cells/mL) and 36 with S aureus (10(8) cells/mL) to evaluate the antimicrobial activity of the cleaning protocols. After incubation (37°C/72 hours), the specimens were divided into 5 groups: not disinfected (positive control), soaking in saline solution for 10 minutes, soaking in 4% chlorhexidine for 10 minutes, soaking in C nardus for 10 minutes, soaking in H canadensis for 10 minutes, and washing by hand with water and neutral soap for 30 seconds. The viability of cells was evaluated by XTT (2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide) assay and by scanning electron microscope analysis. The results were analyzed by ANOVA and the Tukey HSD test (α=.05).

RESULTS

All disinfection solutions provided a statistically significant reduction in biofilm viability compared with the control group for both microorganisms (P<.05). Washing with water and neutral soap was significantly more effective in reducing biofilm viability than immersion in the disinfection solutions, with persistence of viable microorganisms between 1.05% for C albicans and 0.62% for S aureus after this cleaning protocol. Photomicrographs revealed that 4% chlorhexidine altered the surface of the polymer.

CONCLUSIONS

Within the limitations of this in vitro study, it was concluded that the cleaning protocols with different disinfectant solutions produced a significant reduction in the viability of C albicans and S aureus biofilms on the silicone polymer. Washing with water and neutral soap was the most effective protocol against both microorganisms.

Influence of nanoparticles on color stability, microhardness, and flexural strength of acrylic resins specific for ocular prosthesis

The aim of this study was to assess the effect of adding nanoparticles to N1 acrylic resin intended for artificial sclera, in terms of the color stability, microhardness, and flexural strength of the resin. Three hundred samples of N1 acrylic resin were used: 100 samples for color stability and microhardness tests (each test was performed on the opposite side of each sample), and 200 samples for flexural strength testing (100 samples before and after 1,008 hours of accelerated aging). Samples for each test were separated into ten groups (n=10), ie, without nanoparticles (control group) or with nanoparticles of zinc oxide, titanium dioxide (TiO₂), and barium sulfate at weight concentrations of 1%, 2%, and 2.5% (nanoparticle groups). Data were subjected to statistical analysis with nested analysis of variance and Tukey’s test (P<0.05 significance level). Among the nanoparticle groups, the TiO₂ groups showed better color stability at all concentrations. Microhardness values increased after artificial aging, except for the control and zinc oxide groups. After aging, the 1%–2% TiO₂ groups had significantly higher microhardness values compared with the other nanoparticle groups. Before aging, there was a significant difference in flexural strength between the control and nanoparticle groups. After aging, the control and TiO₂ groups, regardless of concentration, showed the lowest flexural strength values. Incorporation of nanoparticles directly influenced the acrylic resin properties, with TiO₂ being the most influential nanoparticle in terms of the evaluated properties.

Effect of surface treated silicon dioxide nanoparticles on some mechanical properties of maxillofacial silicone elastomer

Current materials used for maxillofacial prostheses are far from ideal and there is a need for novel improved materials which mimic as close as possible the natural behavior of facial soft tissues. This study aimed to evaluate the effect of adding different concentrations of surface treated silicon dioxide nanoparticles (SiO2) on clinically important mechanical properties of a maxillofacial silicone elastomer. 147 specimens of the silicone elastomer were prepared and divided into seven groups (n = 21). One control group was prepared without nanoparticles and six study groups with different concentrations of nanoparticles, from 0.5% to 3% by weight. Specimens were tested for tear strength (ASTM D624), tensile strength (ASTM D412), percent elongation, and shore A hardness. SEM was used to assess the dispersion of nano-SiO2 within the elastomer matrix. Data were analyzed by one-way ANOVA and Scheffe test (α = 0.05). Results revealed significant improvement in all mechanical properties tested, as the concentration of the nanoparticles increased. This was supported by the results of the SEM. Hence, it can be concluded that the incorporation of surface treated SiO2 nanoparticles at concentration of 3% enhanced the overall mechanical properties of A-2186 silicone elastomer.

Effect of different disinfecting procedures on the hardness and color stability of two maxillofacial elastomers over time

OBJECTIVE

Disinfection procedures often cause deterioration in a maxillofacial prosthesis. Color and hardness alterations could lead to a replacement of the prosthesis.

MATERIAL AND METHODS

An experimental chlorinated polyethylene (CPE) and a commercial polydimethyl siloxane (PDMS) sample were treated with four different disinfection procedures for a period which simulates 1 year of clinical service. The applied disinfection procedures included microwave exposure and immersion in three solutions, sodium hypochlorite, neutral soap and a commercial disinfecting soap. Shore A hardness (∆H) and color differences (∆E) were determined before and after each procedure. All data were analyzed by Two Way Analysis of Variance (ANOVA) and Tukey's post hoc tests at a level of α=0.05.

RESULTS

The samples presented significant alterations in color and hardness after the different disinfection treatments. The color differences (∆E) were at least eye detectable in all cases and clinically unacceptable in most of the cases, with values ranging from 1.51 to 4.15 and from 1.54 to 5.92 for the PDMS and CPE material, respectively. Hardness was decreased after all the disinfection procedures in the PDMS, while for the CPE, a decrement was observed after disinfection with sodium hypochlorite and neutral soap and an increment after microwave exposure and the disinfection with a commercial antimicrobial agent. The PDMS samples presented greater alterations in color and hardness after disinfection with sodium hypochlorite solution, while the microwave exposure caused negligible effects. The CPE samples were affected most after disinfection when treated with neutral soap, and more slightly when disinfected with sodium hypochlorite solution.

CONCLUSIONS

The disinfection procedures caused alterations in color and hardness of the examined materials. The most suitable disinfection procedure for the PDMS material is microwave exposure, while disinfection with sodium hypochlorite solution is not recommended. The CPE material is suggested to be disinfected with sodium hypochlorite solution and the use of neutral soap is not recommended. Comparing the two materials, the PDMS material is most color stable, while the CPE material presented fewer changes in hardness.

The effect of different storage conditions on the physical properties of pigmented medical grade I silicone maxillofacial material

Objective. This study aimed to evaluate the effect of different storage solutions that simulate acidic, alkaline, and sebum conditiions on the physical properties of pigmented (colorant elastomer) cosmesil M511 maxillofacial prosthetic material. Materials and Methods. Sixty specimens were prepared according to the manufacturer's instructions and were tested before and after immersion of different storage conditions for six months at 37 °C. The following tests were performed: color changes (group I), solution absorption (group II), surface roughness (group III), and scanning electron microscopy (group IV). Results. There were no significant changes observed in the color and solution absorption tests while surface roughness revealed significant difference between control group and other testing storage medium groups, and this result was supported by SEM analysis that revealed limited surface changes. Conclusions. Cosmaseil material is an acceptable cross-linked formulation that withstands storage in different solutions with variable pH. The addition of pigment cannot vary the physical properties of these materials. Surface roughness test as well as SEM microscopic study showed moderate changes indicating a limited effect on the surface of the material.