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

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

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.

Synthesis of Schiff Bases and Secondary Amines with Indane Skeleton; Evaluation of Their Antioxidant, Antibiotic, and Antifungal Activities.

In this study, Schiff bases were synthesized by utilizing the reaction of 4- and 5-aminoindane with substituted benzaldehydes. After the reduction of isolated Schiff bases with NaBH4 , the corresponding secondary amine derivatives were obtained. The structures of all synthesized molecules were confirmed by 1 H-NMR, 13 C-NMR, FT-IR, and ESI-MS. Antioxidant activities of all synthesized molecules were investigated by DPPH method, and IC50 values were calculated. In addition, antibacterial activities of targets were investigated by the well diffusion method, and then MIC99 values were calculated. While only four of the sixteen synthesized molecules showed a high level of antioxidant activity, all of the molecules exhibited biological activity against Gram-positive and Gram-negative bacteria to varying degrees. In addition, all the synthesized molecules showed high antifungal activity. In antioxidant capacity studies, the IC50 values of 2-(((2,3-dihydro-1H-inden-5-yl)amino)methyl)-6-methoxyphenol (4 d) and 2-(((2,3-dihydro-1H-inden-4-yl)amino)methyl)-6-methoxyphenol (7 d) were determined to be 18.1 µg and 35.1 µg, respectively, and these values are much stronger than BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole) used as positive controls. The fact that targets have the same core structure with different substituents has revealed a good structure-activity relationship.

Shear Bond Strength between Orthodontic Brackets and Monolithic 4Y-TZP: An In Vitro Study.

The aim of this study was to evaluate the effect of different surface treatments on the shear bond strength (SBS) between metal orthodontic brackets and monolithic zirconia surfaces bonded with resin composite. Fifty monolithic zirconia (4Y-TZP) disks were sintered and glazed. Specimens were divided into five groups (n = 10) for different surface treatments: control, nano second fiber laser, sandblasting, grinding and tribochemical coating (CoJet Sand 30-µm). Metal orthodontic brackets were bonded to monolithic zirconia surface by two-component orthodontic adhesive. After 500 cycles of thermocycling, shear bond strength values were measured by a universal testing machine at a cross head speed of 0.5 mm/min. The data was recorded as MPa and statistically analyzed with One-way ANOVA, Levene's LSD tests with Bonferroni corrections. The significance level was α = 0.05. The surface topography of one specimen of each group was evaluated by scanning electron microscopy (SEM). Statistically significant difference was observed among study groups (p = 0.018). The lowest shear bond strength was observed in the control group (3.92 ± 1.9). Tribochemical coating showed the highest bond strength (7.44 ± 2.9), which was statistically different from the control and nano second laser (4.3 ± 1.4) groups but not statistically different from grinding (6.15 ± 3.1) or sandblasting (6.47 ± 3.3). SEM images showed comprehensive results of each surface treatment on monolithic zirconia. All failure modes were recorded as adhesive between the composite resin and monolithic zirconia. Based on the findings of this study, it can be concluded that grinding, sandblasting and tribochemical coating techniques showed clinically acceptable bond strength within the range of 6-8 MPa. These surface treatments can be considered suitable for achieving a durable bond between metal orthodontic brackets and monolithic 4Y-TZP ceramic surfaces.

Using Peek as a Framework Material for Maxillofacial Silicone Prosthesis: An In Vitro Study.

There are often bonding problems between acrylic resins and silicone. PEEK (polyetheretherketone), which is a high-performance polymer, has great potential for the implant, and fixed or removable prosthodontics. The aim of this study was to evaluate the effect of different surface treatments on PEEK to be bonded to maxillofacial silicone elastomers. A total of 48 specimens were fabricated from either PEEK or PMMA (Polymethylmethacrylate) (n = 8). PMMA specimens acted as a positive control group. PEEK specimens were divided into five study groups as surface treatments as control PEEK, silica-coating, plasma etching, grinding, or nano-second fiber laser. Surface topographies were evaluated by scanning electron microscopy (SEM). A platinum-primer was used on top of all specimens including control groups prior to silicone polymerization. The peel bond strength of the specimens to a platinum-type silicone elastomer was tested at a cross-head speed of 5 mm/min. The data were statistically analyzed (α = 0.05). The control PEEK group showed the highest bond strength (p < 0.05) among the groups. No statistical difference was found between control PEEK, grinding, or plasma etching groups (p > 0.05). The lowest bond strength was seen in the laser group, which was not statistically different from silica-coating (p > 0.05), and statistically different from control PEEK, grinding, or plasma groups (p < 0.05). Positive control PMMA specimens had statistically lower bond strength than either control PEEK or plasma etching groups (p < 0.05). All specimens exhibited adhesive failure after a peel test. The study results indicate that PEEK could serve as a potential alternative substructure for implant-retained silicone prostheses.

Antimicrobial effects of nano titanium dioxide and disinfectants on maxillofacial silicones.

STATEMENT OF PROBLEM: Deficient hygiene of maxillofacial prostheses can be a source of infection, and various disinfectants, including nano-oxides, have been suggested for the disinfection of silicone prostheses. While maxillofacial silicones involving nano-oxides at different sizes and concentrations have been evaluated in terms of their mechanical and physical properties, reports are lacking on the antimicrobial effect of nano titanium dioxide (TiO2) incorporated into maxillofacial silicones contaminated by different biofilms. PURPOSE: The purpose of this in vitro study was to evaluate the antimicrobial effects of 6 different disinfectants and nano TiO2 incorporation into maxillofacial silicone contaminated with Staphylococcus aureus, Escherichia coli, and Candida albicans biofilms. MATERIAL AND METHODS: A total of 258 silicone specimens (129 pure silicones and 129 nano TiO2-incorporated silicones) were fabricated. Specimens in each silicone group (with or without nano TiO2) were divided into 7 disinfectant groups (control, 0.2% chlorhexidine gluconate, 4% chlorhexidine gluconate, 1% sodium hypochlorite, neutral soap, 100% white vinegar, and effervescent) in each biofilm group. Contaminated specimens were disinfected, and the suspension of each specimen was incubated at 37 °C for 24 hours. Proliferated colonies were recorded in colony-forming units per mL (CFU/mL). The differences in microbial levels among specimens were evaluated to test the effect of the type of silicone and the disinfectant (α=.05). RESULTS: Significant difference was found among disinfectants regardless of the silicone type (P<.05). Nano TiO2 incorporation showed an antimicrobial effect on S aureus, E coli, and C albicans biofilms. Nano TiO2 incorporated silicone cleaned with 4% chlorhexidine gluconate had statistically less C albicans than pure silicone. Using white vinegar or 4% chlorhexidine gluconate led to no E coli on either silicone. Nano TiO2 incorporated silicone cleaned with effervescent had fewer S aureus or C albicans biofilms. CONCLUSIONS: The tested disinfectants and nano TiO2 incorporation into silicone were effective against most of the microorganisms used in this study.

Using Kubelka-Munk reflectance theory to predict optimal pink composite thickness and shade with an opaqued PEEK background for a final gingival color: An in vitro study.

OBJECTIVES: The aims of this study were to demonstrate and evaluate how Kubelka-Munk (K-M) reflectance theory is used to adjust the color of the opaqued PEEK backing and the color and thickness of the resin composite layers in different thicknesses in order to minimize the color difference from a target gingival color. METHODS: PEEK specimens were opaqued with either a dark or a light opaquer. Composite resin layers in 3 different colors were fabricated in varying thicknesses. Reflectance of opaqued PEEK and composite layers was determined using a spectroradiometer. Kubelka-Munk (K-M) absorption (K) and scattering (S) coefficients were derived for each material and then K-M reflectance theory was then used to predict the reflectance of each composite disk as layered on each backing. The color of the opaqued PEEK backings alone and the color of 12 pink composite layers on opaqued PEEK backings was calculated for the CIE D65 Illuminant. Composite resins in 3 different color were then bonded to the opaqued PEEK specimens and color differences of these specimens from the theoretical colors were determined. RESULTS: The ∆E00 values ranged from 0.45 to 1.29 units for the bonded pink specimens and the K-M theory. K-M theory was validated as a viable predictor of gingival color using pink composite bonded to opaqued PEEK background. SIGNIFICANCE: Using K-M theory to predict the gingival color of pink composite bonded to opaqued PEEK eliminates the need to make many specimens of different thicknesses that would otherwise be required to find an acceptable color match.

New generation CAD-CAM materials for implant-supported definitive frameworks fabricated by using subtractive technologies.

Innovations in digital manufacturing enabled the fabrication of implant-supported fixed dental prostheses (ISFDPs) in a wide variety of recently introduced materials. Computer-aided design and computer-aided manufacturing (CAD-CAM) milling allows the fabrication of ISFDPs with high accuracy by reducing the fabrication steps of large-span frameworks. The longevity of ISFDPs depends on the overall mechanical properties of the framework material including its fit, and the physical properties of the veneering material and its bond with the framework. This comprehensive review summarizes the recent information on millable CAD-CAM framework materials such as pre-sintered soft alloys, fiber-reinforced composite resins, PEEK, and PEKK in high-performance polymer family, and 4Y-TZP. Even though promising results have been obtained with the use of new generation millable CAD-CAM materials for ISFDPs, clinical studies are lacking and future research should focus on the overall performance of these millable materials in both static and dynamic conditions.

Effect of argon plasma and Er:YAG laser on tensile bond strength between denture liner and acrylic resin.

STATEMENT OF PROBLEM: The separation of a denture liner from the denture base can be a clinical problem. Different surface treatments to increase the bond have been evaluated, but studies comparing the effect of argon plasma and erbium-doped yttrium aluminum garnet (Er:YAG) laser on the bond between acrylic resin and a denture liner are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of argon plasma and Er:YAG laser treatments on the bond strengths of acrylic resin to 2 denture liners. MATERIALS AND METHODS: Heat-polymerized acrylic resin (Acron Duo) was bonded to silicone soft-liner materials (Molloplast B, n=30; Mollosil, n=30) to create control specimens (n=10), argon plasma treatment (n=10), and Er:YAG laser treatment (n=10). Silicone liners were polymerized on resin specimens. The tensile bond strength test was performed with a crosshead speed of 10 mm/min with a 10-N load until failure. Data were analyzed by using the Kruskal-Wallis test and unpaired t test (α=.05). RESULTS: The laser group showed significantly higher bond strength than the argon plasma group for both Molloplast-B (P=.001) and Mollosil (P<.001). The highest tensile bond strength values were determined in the laser-treated Molloplast-B group (1.325 ±0.119 MPa) while the lowest bond strength values were determined in the Mollosil control group (0.384 ±0.018 MPa). CONCLUSIONS: Argon plasma and Er:YAG laser applications increases the tensile bond strength between soft-liner material and resin. Er:YAG laser treatment results in higher bond strength values than treatment with argon plasma for 1 minute.

Three-dimensional printing technologies in the fabrication of maxillofacial prosthesis: A case report.

PURPOSE: Patients with maxillofacial deformities always seek for aesthetic prosthesis. Recently, three-dimensional printing technologies have been used for dental treatments on such patients. CASE REPORT: A 24-year-old man reported to the Department of Prosthodontics for replacement of his missing right ear induced by a trauma. A magnet-retained auricular prosthesis was planned for the patient. Three-dimensional scanning was performed on the healthy side by using a three-dimensional optical scanner and the data were mirrored. The mirrored image was then imported to a software and a virtual model of the future prosthesis was obtained for the defect side. A three-dimensional printer was used to fabricate a negative mold for the mirrored image by using additive manufacturing. Initially, an impression of the defect side was made; then, the cast model was obtained in a dental flask. Magnets of the prosthesis were inserted to the acrylic resin framework on the cast model. Room temperature vulcanized silicone elastomer was mixed and poured into the three-dimensionally fabricated mold. Then, the flask was placed over the negative mold firmly. After polymerization of the silicone, the auricular prosthesis was delivered to the patient and the patient was instructed to clean the prosthesis daily. CONCLUSIONS: Three-dimensional printing technology was used for the fabrication of the patient's missing ear. This method eliminated the conventional laboratory steps and reduced the number of stages of the fabrication of a silicone prosthesis. The negative mold of the defect side allowed us a direct fabrication of the silicone prosthesis without a need for waxing or flasking procedures.

Microtensile Bond Strength and Failure Type Analysis of Self-Etch Adhesive Systems on Superficial and Deep Dentin After Long-term Water Storage / Análise de resistência de adesão à microtração e tipo de falha de sistemas adesivos autocondicionantes em dentina superficial e profunda após armazenamento longitudinal em água

Objective: The aim of this study was to evaluate and compare the microtensile bond strengths of four current adhesive materials that contain different monomers at deep and superficial dentin. Material and Methods: Forty non-carious human third molars (n=5) were used in the study. Specimens were divided into two main groups according to dentin thickness as superficial and deep dentin. Groups were further divided into four subgroups in terms of the adhesive systems used: Nova Compo B Plus (NCBP), Nova Compo B (NCB), Futurabond M (FB) and Clearfil S3 Bond Plus (CS3). All specimens were bonded to resin composite and stored in 37 °C water for 9-months. Teeth were sectioned into 3 x 3 mm thick beams. Microtensile bond strength test was carried out by using a universal testing device (1 mm/min). After fracture, failure types were observed using an optical microscope and the fractured dentin surfaces were observed by a scanning electron microscopy (SEM). One-way ANOVA and Tukey tests were used to compare the adhesive system in each dentin group. An unpaired T-test was used to compare the dentin thickness in each adhesive material. Results: As compared to deep dentin, superficial dentin showed higher µTBS values in groups NCBP, FB and CS, as opposed to group NCB. Only NCB revealed higher bond strength at deep dentin layers when compared to superficial dentin. In the superficial dentin group, NCBP showed the highest bond strength value while NCB showed the lowest bond strength. In the deep dentin group, while NCB showed the highest bond strength value, NCBP revealed the lowest bond strength value after 9-months storage. While 4-META and 10-MDP monomer combination (NCBP) resulted in the highest bond strength value among the adhesive systems in the superficial dentin group, the GPDMA and 4-META monomer combination (NCB) resulted in the highest bond strength in deep dentin group. Conclusions: Microtensile bond strength performance are affected by both the type of monomer in the adhesive combination and the depth of the dentin. (AU)

Objetivo: o objetivo deste estudo foi avaliar e comparar a resistência de união à microtração de quatro materiais adesivos atuais que contêm monômeros diferentes na dentina profunda e superficial. Material e Métodos: Quarenta terceiros molares humanos não cariados (n = 5) foram usados no estudo. Os espécimes foram divididos em dois grupos principais de acordo com a espessura da dentina em superficial e profunda. Os grupos foram subdivididos em quatro subgrupos quanto aos sistemas adesivos usados: Nova Compo B Plus (NCBP), Nova Compo B (NCB), Futurabond M (FB) e Clearfil S3 Bond Plus (CS3). Todos os espécimes foram aderidos à resina composta e armazenados em água a 37 ° C por 9 meses. Os dentes foram seccionados em palitos de 3 x 3 mm de espessura. O teste de microtração foi realizado com o uso de um dispositivo de teste universal (1 mm / min). Após a fratura, os tipos de falha foram observados em microscópio óptico e as superfícies de dentina fraturadas por microscopia eletrônica de varredura (MEV). Os testes ANOVA e Tukey um fator foram usados para comparar o sistema adesivo em cada grupo de dentina. Um teste T não pareado foi usado para comparar a espessura da dentina em cada material adesivo. Resultados: Em comparação com a dentina profunda, a dentina superficial apresentou maiores valores de µTBS nos grupos NCBP, FB e CS, ao contrário do grupo NCB. Apenas NCB revelou maior resistência de união na dentina profunda quando comparada à dentina superficial. No grupo de dentina superficial, NCBP apresentou o maior valor de resistência de união, enquanto NCB apresentou a menor resistência de união. No grupo de dentina profunda, enquanto NCB apresentou o valor de resistência de união mais alto, NCBP revelou o valor de resistência de união mais baixo após 9 meses de armazenamento. Enquanto a combinação de monômero 4-META e 10-MDP (NCBP) resultou no maior valor de resistência de união entre os sistemas adesivos no grupo de dentina superficial, a combinação de monômero (NCB) resultou na maior força de união no grupo de dentina profunda. Conclusões: O desempenho da resistência de união à microtração é afetado tanto pelo tipo de monômero na combinação adesiva quanto pela profundidade da dentina. (AU)

Shear bond strength of ceramic brackets bonded to surface-treated feldspathic porcelain after thermocycling.

PURPOSE: The aim of this study was to evaluate the effect of six different surface conditioning methods on the shear bond strength of ceramic brackets bonded to feldspathic porcelain. MATERIALS AND METHODS: A total of 60 feldspathic porcelain disks were fabricated and divided into six subgroups including 10 specimens in each. Specimens were first treated one of the following surface conditioning methods, namely, 37% phosphoric acid (G-H3PO4), 9.4% hydrofluoric acid (G-HF), grinding with diamond burs (G-Grinding), Nd:YAG laser (G-Nd:YAG), Airborne-particle abrasion (G-Abrasion). Specimens were also coated with silane without surface treatment for comparison (G-Untreated). A total of 60 ceramic brackets were bonded to porcelain surfaces with a composite resin and then subjected to thermocycling 2500× between 5°C and 55°C. The shear bond strength test was carried out using a universal testing device at a crosshead speed of 0.5 mm/min. Failure types were classified according to the adhesive remnant index. Analysis of variance and Tukey tests were used for statistical analysis (α = 0.05). Microstructure of untreated and surface-treated specimens was investigated by scanning electron microscopy. RESULTS: Using G-Abrasion specimens resulted in the highest shear bond strength value of 8.58 MPa for feldspathic porcelain. However, the other specimens showed lower values: G-Grinding (6.51 MPa), G-Nd:YAG laser (3.37 MPa), G-HF (2.71 MPa), G-H3PO4 (1.17 MPa), and G-Untreated (0.93 MPa). CONCLUSION: Airborne-particle abrasion and grinding can be used as surface treatment techniques on the porcelain surface for a durable bond strength. Hydrofluoric acid and phosphoric acid etching methods were not convenient as surface treatment methods for the feldspathic porcelain.

In Vitro Cytotoxicity of Maxillofacial Silicone Elastomers: Effect of Nano-particles.

PURPOSE: Silicone elastomers are generally used for maxillofacial extraoral prostheses. The purpose of this in vitro study was to evaluate the cytotoxicity of different kinds of nanoparticles added to two types of maxillofacial elastomers. MATERIALS AND METHODS: A-2000 and A-2006 silicone elastomers were used. The silicone specimens were divided into eight groups according to the presence of additional nanoparticles (n = 18). The following represents the groups in the study: Group A: A-2000 silicone (control group); Group B: A-2006 silicone (control group); Group C: A-2000 silicone and the addition of titanium dioxide (TiO2 ); Group D: A-2006 silicone and the addition of TiO2 ; Group E: A-2000 silicone and the addition of fumed silica; Group F: A-2006 silicone and the addition of fumed silica; Group G: A-2000 silicone and the addition of silaned silica; Group H: A-2006 silicone and the addition of silaned silica. A paired sample t-test was used to analyze the cytotoxicity of each group after 24, 48, and 72 hours. RESULTS: Based on the results of the 24-hour analysis, the biocompatibility values of the (A-2006) fumed silica group were higher than those of the control groups. There was no statistically significant difference in A-2006 and A-2000 groups. The cytotoxicity values of the control groups and TiO2 (A-2000 silicone) elastomer groups increased at all test times; however, the cytotoxicity values of the TiO2 (A-2006), fumed silica (A-2006), silaned silica (A-2006), fumed silica (A-2000), and silaned silica (A-2000) groups increased significantly only from 24 to 48 hours. CONCLUSION: Nanoparticles of TiO2 , fumed silica, and silaned silica added to a commercial silicone-based elastomer used for fabrication of maxillofacial prostheses are nontoxic.

The Effect of Silica and Prepolymer Nanoparticles on the Mechanical Properties of Denture Base Acrylic Resin.

PURPOSE: To evaluate how hydrophobic nanoparticle silica and prepolymer affect the flexural strength, surface hardness, surface roughness, and resilience of a denture base acrylic resin. MATERIALS AND METHODS: A total of 40 denture base acrylic resin specimens with dimensions 65 × 10 × 3 mm3 were fabricated in this study. Specimens were divided into five experimental groups (n = 8) according to surface-treated silica and prepolymer concentration incorporated into the acrylic resin (weight %) prior to polymerization: G1 acted as control, no fillers were used in this group. G2: 1 wt% 12 nm silica nanoparticles; G3: 5 wt% 12 nm silica nanoparticles; G4: 1 wt% 12 nm prepolymer nanoparticles; G5: 5 wt% 12 nm prepolymer nanoparticles were added into the acrylic mixture. Acrylic specimens were polymerized according to the manufacturer's instructions. Three-point bending test was performed to evaluate the flexural strength and the resilience of the specimens. Then, a digital profilometer was used to determine the surface roughness of the specimens. Surface hardness was conducted by a digital Shore D hardness testing machine. Surface analysis of one specimen in each group was performed with a scanning electron microscopy (SEM) to observe the fracture surfaces of specimens. ANOVA and Tukey tests were used for the statistical analysis (p < 0.05). RESULTS: Statistical analysis revealed significant differences among the groups. All groups showed poor flexural strength as compared with the control (p < 0.05). Regarding resilience, silica 5% showed the highest value whereas silica 1% showed the lowest value. Regarding Shore D hardness, silica 1% had the lowest hardness whereas polymer addition did not significantly influence the hardness of the acrylic resin (p < 0.05). Furthermore, silica 1% presented the highest roughness as compared with the other groups (p < 0.05). SEM images indicated some porosity and voids on fracture surfaces. CONCLUSIONS: Both the silica and prepolymer incorporation into acrylic resin adversely affected the flexural strength of the acrylic resin compared to control group. In all concentrations, prepolymer incorporation resulted in increased flexural strength of acrylic resins compared to silica addition. The greater concentrations of the fillers resulted in increased mechanical properties of the acrylic resin.

Evaluation of Shore A hardness of maxillofacial silicones: the effect of dark storage and nanoparticles.

PURPOSE: Little has been reported how the addition of nanoparticles could affect the hardness of maxillofacial silicones. The purpose of this study was to evaluate the effects of different types of nanoparticle additives and dark storage for 2-years on the Shore A hardness of two types of maxillofacial silicone elastomers. MATERIALS AND METHODS: A-2000 and A-2006 Room Temperature Vulcanized (RTV) silicone elastomers were tested in this study. Silaned silica, fumed silica and titanium dioxide nanoparticles at concentrations of 10% by volume were used as fillers for the maxillofacial silicone elastomers. A total of 64 silicone specimens were fabricated, which includes 8 samples, 30 × 10 mm in size, from each silicone elastomers for each subgroup and also controls. After the initial Shore A hardness measurements, specimens were kept in dark conditions at room temperature for 2 years. The final measurements were then taken from the silicone specimens. All data were statistically analyzed. RESULTS: For both types of silicones, there was statistically significant differences among study groups (p<0.001). Fumed silica group showed the lowest hardness values in A-2000 after storage. However, no significant difference was observed between control and fumed silica groups. Control group showed the lowest hardness values in A-2006, while the highest hardness values were found in fumed silica group; there was no significant difference between silica and silane groups. CONCLUSION: Shore A values of the specimens were within the acceptable range for the maxillofacial silicones after aging. Nanoparticle addition did not prevent hardening of the silicone elastomers with time.

Effect of different types of disinfection solution and aging on the hardness and colour stability of maxillofacial silicone elastomers.

INTRODUCTION: Understanding the effect of aging and different disinfecting agents on the physical properties of pigmented maxillofacial silicones may help eliminate the current uncertainty as to the best follow-up suggestions for the patients treated with silicone prostheses. METHODS: One hundred fifty specimens (14 × 2 mm) were evaluated for colour and 75 specimens (30 × 10 mm) for hardness (total, 225 specimens). Five specimens were used for hardness testing in each disinfecting solution while 10 silicone specimens were used for colour evaluation. The samples were separated into 5 groups and the initial hardness and colour evaluations were performed and placed in disinfectant solution (neutral soap, effervescent tablet, 0.2% chlorhexidine, 4% chlorhexidine, sodium hypochlorite). A second set of colour and hardness measurements was taken after 48 hours of disinfection and 1,008 hours of artificial aging in a QUV-accelerated weathering tester. Two-way and 1-way analysis of variance with Tukey tests and paired t-test were used for statistical analysis (α = 0.05). RESULTS: Before artificial aging, the hardness value of the red pigment group was found to be significantly lower than that of the brown pigment group. After aging, the lowest Shore A value was seen in the neutral soap group, while the highest was seen in the effervescent tablet. CONCLUSIONS: Based on the results of this study, chlorohexidine 0.2% was found to be most suitable agent for disinfection of the prostheses. Washing with neutral soap caused loss of pigment from the surface of the silicones. Sodium hypochlorite was found to have a colour-fading effect on silicone specimens.

Effects of the Addition of Titanium Dioxide and Silaned Silica Nanoparticles on the Mechanical Properties of Maxillofacial Silicones.

PURPOSE: Silicone-based elastomeric materials are commonly used to fabricate maxillofacial prostheses. The aim of this study was to evaluate the effect of different types of silica and nanosized titanium dioxide addition on the mechanical properties of two RTV silicone elastomers. MATERIALS AND METHODS: A-2000 and A-2006 silicone elastomers were used, and each was divided into four subgroups (n = 5). The first group was the control without additives. Other groups were titanium dioxide, fumed silica, and silaned silica. Each specimen was prepared in compliance with the manufacturer's instructions for the tensile strength, percent elongation, tear resistance, and the hardness tests according to ISO and ASTM standards. A factorial ANOVA with pairwise interaction indicated that the pattern for all four outcomes of the materials was different for A-2000 and A-2006 (p < 0.05). Therefore, the average outcome values for the materials within silicone elastomers were then analyzed by Tukey HSD. For the hardness test results, Kruskal-Wallis and Mann-Whitney U test methods were used. The level of statistical significance was p < 0.05. RESULTS: There was a statistically significant interaction (p < 0.05) between materials and silicone type for all four tests (tensile strength, tear, hardness, percent elongation). The hydrophobic silica group had significantly higher tensile strength than TiO2 for A-2000. The fumed hydrophilic silica group had significantly higher tensile strength than TiO2 for A-2006. Most of silica specimens had higher tensile strength when compared with the control and TiO2 groups for A-2000 and A-2006 silicones. The TiO2 group had the highest hardness value for A-2000 while the lowest hardness value for A-2006 (p < 0.05). There was no significant difference of tear strength among the type of additives (p > 0.05) for A-2000. The fumed silica and TiO2 groups had significantly higher tear strength than the control group for A-2006. The fumed silica and the hydrophobic silica groups had significantly higher percent elongation than the control group (p < 0.05) for A-2000. The TiO2 group had the lowest percent elongation for A-2006. CONCLUSIONS: Results in this in vitro study may clarify future studies about the effect of different additives on the physical and mechanical properties of maxillofacial elastomers. There is a great interest in the effect of a new-generation hydrophobic silica incorporation into A-2000 silicone as well as the effect of fumed hydrophilic silica incorporation into A-2006 silicone. Future research should be supported with more in vitro trials in different percentages of such additives used in this study.

A different wax sculpture technique for implant-retained auricular prosthesis.

Replacement of missing ears is a challenging task in which extensive array of materials and techniques have been employed. This article describes a different and simplified procedure for fabricating auricular prostheses very similar to the intact left ear of the patient. A 65-year-old male patient was referred to the Department of Prosthodontics with the loss of the right ear. In this case, the impression was made using hydrocolloid material (alginate) from the both defected and the opposite side. After hardening of the stone casts, a custom-made transparent splint plate was designed for the left auricular side. The splint was reversed and a cast model of the right auricular side was obtained as pouring the dental stone into transparent orthodontic splint. After getting the impression from cast model, conventional wax pattern and try on process was done. Finally, silicone elastomer was polymerized and the retention of the prosthesis acquired with the magnetic attachments. The technique described is economical, conventional, and time-saving. Furthermore, the prosthesis imitates the patient's intact auricular tissue.

Different techniques in fabrication of ocular prosthesis.

INTRODUCTION: Loss of an eye caused by cancer, trauma, or congenital defect creates a deep psychological impact on an individual's life especially social and professional life. Custom-made prosthesis, compared to stock prosthesis, provides a better fit to the eye socket, better cosmetic results, and less discomfort to the patient in the long term. The main objective of this article was to describe 3 different alternative and practical techniques of fabricating custom-made ocular prosthesis. CASE REPORT: An impression of anophthalmic socket was made with the addition of cured silicone-based precision impression material in all techniques. A master cast was prepared and duplicated with condensation silicone. A self-cure acrylic resin was polymerized in the silicone model and was fitted into the patient's eye socket. A digital photograph of the patient's iris was made using a digital camera and printed on good-quality photo paper in various shades and sizes in the first and the second techniques. Then the photo paper was coated with PVC so as not to allow any color flowing. The proper iris was then inserted to the acrylic base. The prosthesis was final processed using orthodontic heat polymerizing clear acrylic resin.In the other technique, after the trying-in process with wax pattern, an acrylic base was fabricated using heat polymerizing scleral acrylic resin. The prosthetic iris was fabricated from a transparent contact lens by painting the lens with watercolor paints and attaching it to an acrylic resin with tissue conditioner. The final process was made with heat polymerizing transparent acrylic resin. CONCLUSIONS: Custom-made prosthesis allows better esthetic and functional results to the patient in comparison to stock prosthesis. Further follow-up is necessary to check the condition and fit of the ocular prosthesis in such patients.