Microwave disinfection of facial silicone prostheses, part 2: Mechanical properties.

STATEMENT OF PROBLEM: Part 1 of this 2-part study determined that microwave disinfection did not degrade the color stability of facial silicone prostheses. However, investigations on the effects of microwave disinfection on the mechanical properties of different silicone elastomers are lacking. PURPOSE: The purpose of this in vitro study was to examine the mechanical properties of commonly used colored facial silicone elastomers before and after microwave disinfection over a simulated 1.5-year period. MATERIAL AND METHODS: Six commonly used facial silicone elastomers: MDX4-4210, MDX4-4210/Type A, M511, A-2186, VST-50, and A-2000 were combined with functional intrinsic silicone pigments and opacifier (red, yellow, blue, and white). A total of 288 specimens were fabricated (n=12). Half of the specimens were tested for mechanical properties as the baseline, while the other specimens were tested after microwave disinfection. Microwave disinfection was performed with 660 W, 6 minutes of exposure time, and microwaved for 18 cycles to simulate 1.5 years of usage (one 6-minute exposure monthly). For mechanical property testing, all specimens were tested for tensile strength and percentage elongation (ASTM D412), tear strength (ASTM D624), and hardness (ASTM D2240). For each property, a 2-way ANOVA (silicone type and microwave disinfection factors) and Tukey multiple comparison test were performed using the R statistical software program (α=.05). RESULTS: Following microwave disinfection, tensile strength and percentage elongation of A-2000 increased significantly (P<.05). MDX4-4210, MDX4-4210/Type A, and A-2000 showed significant increases in their hardness (P<.001). Tear strength also increased significantly for MDX4-4210 and VST-50 (P<.05). Among the materials tested (ranked from highest to lowest value,=not statistically significant different), for tensile strength, VST-50>A-2186=A-2000>MDX4-4210/Type A=M511=MDX4-4210 (P<.05). For percentage elongation, VST-50>MDX4-4210/Type A>A-2186>M511=A-2000=MDX4-4210=M511 (P<.05). For hardness, A-2000=A-2186>M511=VST-50>MDX4-4210>MDX4-4210/Type A (P<.05). For tear strength, VST-50>A-2186>A-2000>M511>MDX4-4210/Type A=MDX4-4210 (P<.05). CONCLUSIONS: Overall, the mechanical properties of all the silicones tested were not adversely affected by microwave disinfection. VST-50 showed the best mechanical properties among the materials tested both before and after microwave disinfection. Microwave energy is a safe method of disinfecting the silicone elastomers tested in this study.

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.

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.

Effect of surface pretreatment and artificial aging on the retention of lithium disilicate crowns cemented to zirconia implant abutments.

STATEMENT OF PROBLEM: Recent advancements in restorative dentistry have seen an increase in the use of ceramic restorations and zirconia implant abutments. However, how the pretreatment of a zirconia abutment and different artificial aging protocols affect the bond strength of a cemented, monolithic lithium disilicate crown is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of surface pretreatment on the retentive strength of milled lithium disilicate crowns bonded to custom zirconia implant abutments with different resin cements after thermocycling and long-term aging. MATERIAL AND METHODS: A total of 144 crowns (n=8) were milled and bonded to 144 abutments. In the experimental groups, 72 abutments were airborne-particle abraded with 50-µm aluminum oxide before bonding. All specimens were stored at 37 °C in 100% humidity for 24 hours. Forty-eight specimens were subjected to thermocycling, and another 48 were subjected to aging for 6 months. Retentive strength was measured by using a pull-off test with a universal testing machine. Retentive strength values were calculated and compared with 3-way analysis of variance and a Tukey-Kramer post hoc test (α=.05). RESULTS: In the 24-hour aging group, retention for all experimental groups was significantly higher (P<.05) than for the control group, except for Panavia 21 with Clearfil Ceramic Primer. In the thermocycling and long-term aging groups, all cements in the experimental group displayed significantly higher retention than the control. The airborne-particle abrasion of custom zirconia implant abutments with 50-µm aluminum oxide before bonding to lithium disilicate crowns significantly increased the bond strength of the Multilink Hybrid Abutment with Monobond Plus and RelyX Ultimate with Scotchbond Universal cements after 24-hour aging, but not of Panavia 21 with Clearfil Ceramic Primer. CONCLUSIONS: Airborne-particle abrasion significantly increased the bond strength of all 3 cements after thermocycling and long-term aging.

Retentive strength of implant-supported CAD-CAM lithium disilicate crowns on zirconia custom abutments using 6 different cements.

STATEMENT OF PROBLEM: The optimal retention of implant-supported ceramic crowns on zirconia abutments is a goal of prosthodontic treatment. PURPOSE: The purpose of this in vitro study was to evaluate the retentive strength of implant-supported IPS e.max CAD-CAM (e.max) crowns bonded to custom zirconia implant abutments with different cements. MATERIAL AND METHODS: An optical scan of a zirconia custom abutment and a complete-coverage modified crown was designed using an intraoral E4D scanner. One hundred twenty lithium disilicate crowns (IPS e.max CAD) were cemented to 120 zirconia abutment replicas with 1 of 6 cements: Panavia 21 (P21), Multilink Hybrid Abutment (MHA), RelyX Unicem 2 (RXU), RelyX Luting Plus (RLP), Ketac Cem (KC), and Premier Implant (PI). The specimens were stored at 37°C in 100% humidity for 24 hours. Half of the specimens were thermocycled for 500 cycles. The retentive force was measured using a pull-out test with a universal testing machine. Mean retentive strengths (MRS) were calculated using 2-way ANOVA and the Tukey-Kramer test (α=.05). RESULTS: The MRS (MPa) after 24-hour storage were P21 (3.1), MHA (2.5), RXU (2.5), RLP (1.3), KC (0.9), and PI (0.5). The MRS after thermocycling were MHA (2.5), P21 (2.2), RLP (1.8), KC (1.4), RXU (1.1), and PI (0.3). P21 had the highest MRS after 24-hour storage (P<.001), but after thermocycling MHA had the highest MRS (P<.001). RXU showed a significant decrease in MRS after thermocycling (P<.05). Cement residue was mostly retained on the zirconia abutments for P21, while for the other cements' residue was retained on the lithium disilicate crowns. CONCLUSIONS: The cements tested presented a range of retentive strengths, providing the clinician with a choice of more or less retentive cements. MHA was the most retentive cement after thermocycling. Thermocycling significantly affected the retentive strengths of the P21 and RXU cements.

Color stability of denture teeth and acrylic base resin subjected daily to various consumer cleansers.

OBJECTIVE: This study evaluated color stability of acrylic denture teeth and base resins after 48 weeks of commercial denture cleanser simulation. MATERIALS AND METHODS: Two brands of denture teeth (Trubyte Portrait IPN, TP; SR Vivodent DCL, SR) in shades A1, B1, and C1 and three acrylic base resins (Lucitone, LU; Paragon, PA; Valplast, VA) prepared to manufacturer's specifications were exposed 10 hours daily to four cleansers (Clorox Bleach, CB; Polident 3 minute, PO3; Efferdent, EF; and Kleenite, KL) and distilled water control, approximating consumer overnight use. Color measurements used the standard Commision International de l'Eclairage (International Commission on Illumination, CIE L*a*b*) color space (0, 4, 12, 24, 36, and 48 weeks.) Color differences (ΔE*) at 48 weeks were subjected to four-way analysis of variance (ANOVA). Mean values were compared with Fisher's (protected least significant difference) intervals (0.05 significance level). RESULTS: Mean color differences (ΔE*) demonstrated color changes in each material. ANOVA-indicated color changes in teeth were significantly affected by both cleansers and teeth brand (p < 0.05), but not shade. Color changes in base resins were significantly affected by cleansers (p < 0.05), but not brand alone. Overall, KL produced the least color change while CB and PO3 produced the most for all materials. CONCLUSIONS: After 48 weeks of daily simulation, TP teeth were more color stable than SR in all cleansers except EF (p < 0.0001). Base resin VA was less color stable than LU and PA. Cleanser KL resulted in the lowest color changes. CLINICAL SIGNIFICANCE: All tested materials yield clinically acceptable color changes (ΔE* < 3.5); all cleansing methods tested can be recommended, although Kleenite demonstrated the least change after 48 weeks.

Effect of opacifiers and UV absorbers on pigmented maxillofacial silicone elastomer, part 1: color stability after artificial aging.

STATEMENT OF PROBLEM: Much dissatisfaction with the color instability and reduced lifetime of extraoral maxillofacial prostheses due to degradation has been reported. PURPOSE: The purpose of this study was to compare the effect of a UV mineral-based light protecting agent (LP) on the color stability of pigmented maxillofacial silicone elastomer MDX-4210/Type A after artificial aging to 2 widely used opacifiers. MATERIAL AND METHODS: Forty-five groups were established (n=225 total). Three different types of opacifiers (LP, titanium white dry pigment [TW], or silicone intrinsic white [SW]) were added to silicone MDX-4210/type A at 3 concentrations (5%, 10%, or 15%) and subsequently combined with each of 5 colors (no pigments [control], red, blue, yellow, or mixed pigments). Artists' oil pigment was used with LP and TW, while intrinsic silicone pigment was used to color SW. Before and after an energy exposure of 450 kJ/m(2), CIE L*a*b* values were measured with a spectrophotometer. The CIELAB 50:50% perceptibility (ΔE*=1.1) and acceptability threshold (ΔE*=3.0) were used to interpret color changes (ΔE*). Color differences after aging were subjected to 3-way ANOVA. Means were compared by the Fisher PLSD intervals at α=.05. RESULTS: The ΔE* values of all groups were below the acceptability threshold of ΔE*=3.0, except for the control group of SW at 10%, which showed the greatest color change (ΔE*=3.1). When mixed pigment groups were considered, at 5% concentration, LP showed the smallest color change, followed by SW and TW (P<.05); at 10%, no significant differences among the 3 opacifiers were noted (P>.05); at 15%, LP showed the smallest color change, followed by TW and SW (P<.05). CONCLUSIONS: All 3 opacifiers at all concentrations protected pigmented silicone MDX4-4210/Type A from color degradation. The LP group showed the smallest color changes.

Effect of opacifiers and UV absorbers on pigmented maxillofacial silicone elastomer, part 2: mechanical properties after artificial aging.

STATEMENT OF PROBLEM: There are reports of dissatisfaction with color instability and reduced lifetime of extraoral maxillofacial prostheses. Previous studies showed that UV mineral-based light-protecting agent (LP) improved color stability of MDX4-4210/Type A silicone elastomer. However, effects of this agent and opacifiers on mechanical properties of the elastomer are unknown. PURPOSE: The purpose of this study was to evaluate the effect of 2 commonly used opacifiers and LP, a new opacifier, when combined with pigments on the mechanical properties of MDX4-4210/Type A silicone elastomer before and after artificial aging. MATERIAL AND METHODS: Two commonly used opacifiers, titanium white dry pigment (TW) and silicone intrinsic white (SW) and LP were each combined with MDX4-4210/type A. Artists' oil pigment was then combined with the LP and TW groups, and silicone intrinsic pigments were combined with the SW group with 5 colors (no pigment=control, red, yellow, blue, or a combination of the 3 pigments). Ten dumbbell-shaped and 10 trouser-shaped specimens of each opacifier + pigment mixture, plus a control group with no opacifier and no pigment, were made for a total of 320 specimens. Half of the specimens (n=5) were aged in a chamber at 450 kJ/m(2). Specimens were tested for hardness (ASTM D2240), tensile strength (ASTM D412), tear strength (ASTM D624), and percentage elongation in a universal testing machine. A 3-way ANOVA and the Fisher PLSD test were performed (α=.05) for each mechanical property. RESULTS: After accelerated aging, values of Shore A hardness were the lowest for LP with all 5 pigments and the control, followed by SW and TW (P<.001). After accelerated aging, tear strength, tensile strength, and elongation decreased significantly (P<.001) for LP, whereas changes for SW and TW varied depending on the pigment. CONCLUSIONS: The mechanical properties of specimens with the light-protecting opacifier were adversely affected after being subjected to artificial aging. SW and TW preserved the mechanical properties of silicone in this study.

Extraoral Maxillofacial Prosthetic Materials: Results of the 2020 International Survey.

PURPOSE: To report the results of a 2020 international survey of the most commonly used materials and techniques for the fabrication of extraoral maxillofacial prosthetics, and to assess the use of 3D technology. MATERIALS AND METHODS: A 43-question survey was administered via Qualtrics to the members of the American Academy of Maxillofacial Prosthetics (AAMP), the International Anaplastology Association (IAA), and the International Society of Maxillofacial Rehabilitation (ISMR). The use of current 3D technology in the fabrication of maxillofacial prostheses as well as barriers to care such as patient cost and insurance coverage were also assessed. RESULTS: In total, 134 respondents (13%) completed the survey; 96 (73%) reported that they were currently fabricating maxillofacial prostheses and were thus included in the survey. The majority of respondents reported currently using Silastic MDX4-4210 BioMedical Grade Elastomer (DuPont) with either Silastic Medical Adhesive Silicone Type A or Silastic MDX4-4210 crosslinker. Incorporating the use of current CAD/CAM technology was reported by a majority of respondents (58%; 45/77); however, a small cohort (33%, 15/45) reported they were still experimenting how best to use technology. A total of 39 clinicians (49%) reported that facial prosthetics were most often paid for by the patient (fee for service), with the fees ranging from $10 to $5,500 USD. CONCLUSIONS: The results of this survey indicate that current CAD/CAM technology has been adopted and incorporated into the design and fabrication of maxillofacial prostheses. More research is needed to advance CAD/CAM technology as well as the physical and mechanical properties of materials in maxillofacial prosthetics and anaplastology clinical practice. Int J Prosthodont 2023;36:570-580.

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.

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.

Effect of imatinib on oral wound healing after extraction: A rare case report.

BACKGROUND: Proper tissue repair and healing after oral surgery are vital to achieve optimal outcomes. Certain medications may interfere with wound healing, but this debilitating adverse drug reaction is often not reported in the literature. It is unknown whether imatinib (Gleevec; Novartis Pharmaceuticals) interferes with gingival healing after oral surgery. CASE DESCRIPTION: A 58-year-old man with a dislodged crown and core buildup of tooth no. 19 sought treatment at a prosthodontic clinic. After examination, the patient consented to extraction, ridge preservation, and future implant placement. He had previous surgical resection of a gastrointestinal stromal tumor and was taking 400 mg of imatinib daily. After extraction and ridge preservation, delayed soft-tissue healing and loss of the coronal portion of bone graft were observed at 8 weeks after surgery. Delayed wound healing was observed again after revision surgery. After imatinib therapy was paused, the adverse effect subsided and the wound healed properly. On the basis of causality assessment and clinical judgment, the authors determined that imatinib was the probable cause of this adverse drug reaction. To their best knowledge, this is the first report of delayed gingival healing after oral surgery secondary to imatinib. PRACTICAL IMPLICATIONS: Dental practitioners should consider the possibility of impaired healing among their patients taking imatinib, especially before procedures that damage gingival tissue, although this adverse drug reaction is not reported in the drug's package insert. Consult with the patient's oncologist is advised before dental manipulations; temporary discontinuation (or dose reductions) of imatinib may be warranted until wounded tissue heals properly.

Impact strength of 3D printed and conventional heat-cured and cold-cured denture base acrylics.

PURPOSE: To evaluate and compare the impact strength of 3D-printed resin to conventionally fabricated denture bases of heat-cured and cold-cured acrylic resin. MATERIALS AND METHODS: Denture base materials were evenly divided into three groups (n = 25 each; N = 75): (1) 3Dprinted material (Denture Base LP, Formlabs); (2) Heat-cured acrylic resin (Lucitone 199, Dentsply Sirona); and (3) cold-cured acrylic resin (Lucitone HIPA, Dentsply Sirona). The 3Dprinted specimens were designed through computer-aided design (CAD) software (Autodesk Meshmixer) with the dimensions 64 mm long, 12.7 mm wide, and 3.2 mm thick, then printed with a desktop stereolithography printer (Form 2, Formlabs). Heat-cured and cold-cured acrylic resin specimens were fabricated through conventional (compression and pouring) methods. The impact energy was read directly from the impact tester in joules, and the cross-sectional area of each specimen was used to calculate the impact strength in kJ/m2. Analysis of variance, Tukey multiple comparisons test, and a likelihood ratio α = .05 were conducted. RESULTS: The average mean impact strength was 8.9 kJ/m2 for heat-cured acrylic resin, 11.2 kJ/m2 for 3D-printed resin, and 14.9 kJ/m2 for cold-cured acrylic resin. Tukey multiple comparisons test showed that the impact strength for the cold-cured group was significantly greater than the 3D-printed resin and heat-cured acrylic resin groups. CONCLUSION: Within the limitations of this study, the cold-cured acrylic (Lucitone HIPA) showed the greatest impact strength, followed by 3D-printed resin (Denture Base LP) and conventional heat-cured denture base materials (Lucitone 199), respectively.

Survey of Dental Implant and Restoration Selection by Prosthodontists in Dubai.

BACKGROUND: With various surgical and prosthetic component designs being introduced in dental implants, decisions have to be made when choosing a system and a certain prosthodontic protocol. A survey of implant prosthodontic specialists has not been previously performed in the Middle East. AIM: This study aimed to determine selection criteria and choice of dental implants and restorations by prosthodontic specialists in the Emirate of Dubai, United Arab Emirates. MATERIALS AND METHODS: A validated 16-item questionnaire was used in the survey which included demographic information, implant training and experience, implant treatment planning, implant restoration, and implant system preference. The research protocol was approved by the Research and Ethics Committees of Hamdan Bin Mohammed College of Dental Medicine and Dubai Health Authority. Prosthodontists were identified from regulatory authority websites and contacted by e-mail with the questionnaire attached. RESULTS: A total of 84.6% (77) of the registered prosthodontists in Dubai completed the questionnaire with 66.2% reported practicing implant dentistry. Out of which, 54.9% reported surgically placing dental implants and 45.1% restore them only prosthetically. Prefabricated metal abutments were the most commonly selected abutments for single crowns (76.0%) and for fixed dental prostheses (66.7%). Screw retention is preferred mostly for single crowns (68.0%) and fixed dental prostheses (74.0%). Locators were the most commonly selected type of attachment for implant-retained/supported overdentures (49.0%). Conventional loading was the most selected type of loading in all oral conditions. CONCLUSION: Within the limitations of this study, it can be concluded that most prosthodontists in Dubai practice implant dentistry and more than half surgically place dental implants. Prefabricated metal abutments are the most selected type of abutments. Most prosthodontists use screw-retained implant restorations and prefer locator attachments for implant-retained/supported overdentures. Conventional loading is the most preferred implant loading method in all oral conditions. Implant company/system selections are various and there is no major preference for a certain system. The majority of prosthodontists select implant systems based on implant features, literature review, and simplicity of restorative kit.

Color Stability and Mechanical Properties of Two Commonly Used Silicone Elastomers with e-Skin and Reality Coloring Systems.

PURPOSE: To evaluate the color stability and mechanical properties of two commonly used maxillofacial silicone elastomers after addition of pigments and opacifiers and before and after artificial aging. MATERIALS AND METHODS: This study evaluated two maxillofacial silicone elastomers: A-2000 and M511. Two different pigment and opacifier systems (e-Skin and Reality Series) were used with the elastomers. Control groups (no pigment or opacifier) and experimental groups (each with subgroups containing additional pigments and/ or opacifiers) were fabricated for each of the silicone elastomers. A total of 51 specimens were evaluated for color stability, and 100 for mechanical properties. A spectrophotometer was used to assess CIE L*a*b* values before and after aging. CIELAB 50:50% perceptibility threshold (ΔE* = 1.1) and acceptability threshold (ΔE* = 3.0) were used to interpret color changes. A durometer and universal testing machine were used to evaluate the mechanical properties. ANOVA and Fisher least significant difference (LSD) test were performed to determine the statistical significance of the results (P < .05). RESULTS: Significant differences in color measurements (ΔE*) were found for all silicone groups following artificial aging (P < .05). ΔE* values for the mixed pigment/opacifier subgroups of both elastomers were below the perceptibility threshold. Additionally, after aging, the hardness, tear strength, and tensile strength significantly increased for all silicone groups (P < .05), while percent elongation significantly decreased (P < .05). CONCLUSION: Artificial aging affected the color stability and mechanical properties of the pigmented silicone elastomers with added opacifier. Overall, A-2000 with e-Skin group displayed the most color stability, with its mechanical properties being the least affected by artificial aging.

Survey of currently used materials for fabrication of extraoral maxillofacial prostheses in North America, Europe, Asia, and Australia.

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

Color difference thresholds of maxillofacial skin replications.

PURPOSE: The purpose of this study was to determine perceptibility and acceptability thresholds for color differences in light and dark skin-colored maxillofacial elastomers. MATERIALS AND METHODS: A total of 15 pairs of light specimens (mimicking white, Asian, and Hispanic skin) and 15 pairs of dark specimens (mimicking African-American skin) were made using skin-colored maxillofacial silicone elastomers, combined with opacifiers and pigments. Color match/mismatch and acceptable/unacceptable mismatch of each pair of specimens were visually evaluated by 45 evaluators under controlled conditions of a viewing booth. Color differences were calculated using CIELAB and CIEDE2000 formulae. After calculating the model parameters, receiver operating characteristics (ROC) curves and area under the ROC curve (AUC) were analyzed. Repeated measures ANOVA and Tukey's HSD test were used in a statistical analysis (alpha= 0.05). RESULTS: CIELAB/CIEDE2000 perceptibility and acceptability thresholds for light specimens were 1.1/0.7 and 3.0/2.1, respectively. Corresponding values for dark specimens were 1.6/1.2 and 4.4/3.1, respectively. Differences in primary specimen color and type of threshold were found to be significant (p < 0.001). Only the primary specimen color effect was found to be significant in AUC comparisons. CONCLUSIONS: Within the limitations of this study, both main effects of threshold type (perceptibility and acceptability) and primary color (light and dark) on 50:50% color-difference thresholds of colored maxillofacial elastomers were found significant for both color-difference formulae used (CIELAB, CIEDE2000). In addition, significant interaction between the two main effects was found, indicating a stronger effect of skin type on acceptability than perceptibility thresholds. Primary specimen color (light vs. dark) was found to be the only significant main effect on the AUC of ROC curves constructed from logistic regression.

Microleakage of all-ceramic crowns using self-etching resin luting agents.

Self-etching adhesive systems are a new generation of materials that possess acidic methacrylates that can generate self-adhesion. There is limited data reported on the marginal leakage of ceramic restorations bonded with self-etching adhesive materials. This study assessed and compared the amount of microleakage of bonded ceramic crowns using three different types of self-etching adhesive systems with and without a die spacer. Eighteen human molars were prepared for all-ceramic IPS Empress crowns and the teeth were randomly assigned to each experimental group. The buccal side had the preparation finish line 1.5 mm below the CEJ, and the lingual finish line was 1.5 mm above the CEJ, creating margins in enamel and dentin. Two die-spacing techniques were used (three layers or no layer of die spacer). Each crown restoration was cemented with one of three self-etching resin luting agents (Panavia F 2.0, Multilink and RelyX Unicem). The specimens were thermally cycled for 1000 cycles, then immersed in a 5% methylene blue dye solution for 24 hours. The teeth were then rinsed, embedded in clear epoxy resin and sectioned. A total of 60 sections were evaluated for each type of resin luting agent using digital image analysis at 70x magnification. A novel formula, using mean percentage of microleakage, was developed by dividing the extent of dye penetration along the tooth/resin luting cement interphase and the total perimeter of the tooth crown surface. The data were analyzed using three-way analysis of variance at the 0.05 level of significance. Fisher's PLSD intervals were calculated for comparing significant means. Panavia F 2.0 showed a lower degree of microleakage than RelyX Unicem and Multilink at both the enamel and dentin margins. Interactions of the main effects (cement, margin and die spacer technique) were all highly significant (p< or =0.004). The degree of microleakage was higher on the dentin margins than on the enamel margins (p<0.0001). The degree of microleakage for the die spacer group was not significantly different from the group with no die spacer technique (p>0.1). Overall, Panavia F 2.0 showed the least microleakage, followed by RelyX Unicem and Multilink, respectively.

Effect of nano-oxide concentration on the mechanical properties of a maxillofacial silicone elastomer.

STATEMENT OF PROBLEM: Contemporary silicone-based elastomeric prostheses tend to degrade over time because of the effect of mechanical loading. Little has been reported on how the mechanical properties of a maxillofacial prosthetic elastomer may be affected by the addition of nanosized oxide particles used as an opacifier. PURPOSE: The purpose of this study was to evaluate the effect of different concentrations of nanosized oxides of various composition on the mechanical properties of a commercially available silicone elastomer. MATERIAL AND METHODS: Nanosized oxides (Ti, Zn, or Ce) were added in various concentrations (0.5%, 1.0%, 1.5%, 2.0%, 2.5%, or 3.0% by weight) to a commercial silicone elastomer (A-2186), commonly used for fabricating extraoral maxillofacial prostheses. Silicone elastomer A-2186 without nanosized oxides served as a control group. Specimens (n=5) were polymerized according to manufacturer's recommendations and tested for tensile strength (ASTM D412) and tear strength (ASTM D624), and percent elongation in a universal testing machine. Uniformity of particle dispersion within the processed elastomer was assessed using scanning electron microscopic imaging. For each property, a 2-way ANOVA was performed evaluating the effect of oxide type and strength, and Fisher's PLSD test was used for pairwise comparisons (alpha=.05). RESULTS: SEM examination indicated that all 3 nanosized oxides distribute evenly throughout the silicone specimens, except for the 3.0% group, which are partly agglomerated. The 2.0% and 2.5% groups of all nanosized oxides demonstrated significantly higher tensile and tear strengths and percent elongation (P<.001) than the control group. CeO(2) had significantly lower tensile strength than TiO2 and ZnO (P<.05). The ZnO group had significantly higher tear strength than TiO(2) and CeO(2) (P <.05). Most of specimens became somewhat harder when compared with the control group. CeO(2) group had significantly higher Shore A hardness than TiO(2) and ZnO (P<.001). There was no significant difference of percent elongation among the type of nanosized oxides. CONCLUSIONS: Incorporation of Ti, Zn, or Ce nano-oxides at concentrations of 2.0% and 2.5% improved the overall mechanical properties of the silicone A-2186 maxillofacial elastomer.