Sudarat Kiat-amnuay

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 manufacturers 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 Fishers 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.

Facial prosthetic rehabilitation: Preprosthetic surgical techniques and biomaterials

Purpose of reviewAttention to detail ensuring a successful facial prosthetic rehabilitation must be considered a priority at the time of presurgery, surgery, and at every stage in fabricating the prosthesis. Teamwork between the surgeon and maxillofacial prosthodontist will ensure an optimal surgical preparation and definitive prosthesis. Recent findingsEvidence of interaction between team members can most certainly be encouraging to the patient. During the prosthetic phase of treatment, focusing on tissue assessment, impression making, sculpting, mold fabrication, familiarity with materials, appreciation of color, delivery of instructions, and patient education will ensure a satisfactory outcome. With the desire, determination, and encouragement from the restorative team to make the most of this artificial replacement, a patient can have a higher quality of life and a more normalized lifestyle. SummaryThis review presents current concepts regarding facial prosthetic rehabilitation of patients with head and neck cancer and facial prosthetic biomaterials.

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. Fishers 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.

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 Tukeys 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.

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 artists 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.

Adhesive retention of silicone and chlorinated polyethylene for maxillofacial prostheses

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

Color stability of pigmented maxillofacial silicone elastomer: Effects of nano-oxides as opacifiers

OBJECTIVES This study evaluated the effects of nano-oxides on the color stability of pigmented silicone A-2186 maxillofacial prosthetic elastomers before and after artificial aging. METHODS Each of three widely used UV-shielding nano-sized particle oxides (TiO(2), ZnO, CeO(2)), based on recent survey of the industry at 1%, 2%, 2.5% concentrations were combined with each of five intrinsic silicone pigment types (no pigments, red, yellow, blue, and a mixture of the three pigments). Silicone A-2186 without nano-oxides or pigments served as control, for a total of 46 experimental groups of elastomers. In each group of the study, all specimens were aged in an artificial aging chamber for an energy exposure of 450kJ/m(2). CIE L*a*b* values were measured by a spectrophotometer. The 50:50% perceptibility (ΔE*=1.1) and acceptability threshold (ΔE*=3.0) were used in interpretation of recorded color differences. Color differences after aging were subjected to three-way analysis of variance. Means were compared by Fishers PLSD intervals at the 0.05 level of significance. RESULTS Yellow pigments mixed with all three nano-oxides at all intervals increased ΔE* values significantly from 3.7 up to 8.4. When mixed pigment groups were considered, TiO(2) at 2%, and 2.5% exhibited the smallest color changes, followed by ZnO and CeO(2), respectively (p<0.001). At 1%, CeO(2) exhibited the smallest color changes, followed by TiO(2) and ZnO, respectively (p<0.001). The smallest color differences, observed for nano-oxides groups, were recorded for CeO(2) at 1%, and TiO(2) at 2% and 2.5%. When the nano-oxides were tested at all concentrations, CeO(2) groups overall had the most color changes, and TiO(2) groups had the least. All ΔE* values of the mixed pigment groups were below the 50:50% acceptability threshold (ΔE*=1.2-2.3, below 3.0) except 2% CeO(2) (ΔE*=4.2). CONCLUSION 1% nano-CeO(2) and 2% and 2.5% nano-TiO(2) used as opacifiers for silicone A-2186 maxillofacial prostheses with mixed pigments exhibited the least color changes when subjected to artificial aging at 450kJ/m(2). Yellow silicone pigment mixed with all three nano-oxides significantly affected color stability of A-2186 silicone elastomer.

Influence of pigments and opacifiers on color stability of silicone maxillofacial elastomer

OBJECTIVES To determine the effects of opacifiers and silicone pigments on the color stability of silicone A-2000 maxillofacial prosthetic elastomers subjected to artificial aging. METHODS Seventy-five groups (n=5) were made by various combinations (5%, 10%, and 15%) of four dry earth opacifiers (Georgia kaolin, Gk; calcined kaolin, Ck; Artskin white, Aw; titanium white dry pigment, Td); and 1 silicone pigment white (Sw) with one of 5 silicone pigments (no pigment (control), red (Pr), yellow (Py), burnt sienna (Po), and a mixture of Pr+Py+Po). A reflection spectrophotometer was used for color measurements. Color differences (DeltaE*) between baseline and after an energy exposure of 450kJ/m(2) in an artificial aging chamber were calculated. A DeltaE*=3.0 was used as 50:50% acceptability threshold in result interpretation, while DeltaE*=1.1 was used as 50:50% perceptibility threshold. Means were compared by Fishers PLSD intervals at the 0.05 level of significance. Color differences after aging were subjected to three-way analysis of variance. RESULTS Yellow ochre mixed with all opacifiers at all intervals had increased DeltaE* values significantly from 0.7-2.1 up to 3.8-10.3. When mixed groups were considered, at 5%, Gk exhibited the smallest color changes, followed by Td0.05). The smallest color differences, observed for opacifier groups, were recorded for Gk at 5%, and Td and Aw at 10% and 15%. Overall, 15% Td exhibited the smallest, whereas 5% Ck exhibited the most pronounced color change after artificial aging. All DeltaE* values were below the 50:50% acceptability threshold, indicating acceptable color stability. Color differences for 10% and 15% of Aw and Td were below 50:50% perceptibility thresholds, indicating excellent color stability. CONCLUSION Silicone pigments mixed with 10% and 15% Artskin white and titanium white dry pigment opacifiers protected silicone A-2000 from color degradation over time. Yellow silicone pigment significantly affected color stability of all opacifiers especially silicone pigment white and calcined kaolin.

An occlusal guard for preventing and treating self-inflicted tongue trauma in a comatose patient: A clinical report

This clinical report describes the treatment of a 48-year-old patient who demonstrated neuropathologic and reflex mastication of her tongue after an intracerebral hemorrhage. Standard medical interventions failed to address the oral condition, and the attending neurosurgeon consulted the dental team. A provisional soft occlusal guard was initially placed, followed by fabrication of a heat-polymerized, acrylic resin occlusal guard. The tongue injury improved after placement of the oral device and administration of systemic hydrocortisone.

Survey of currently selected dental implants and restorations by prosthodontists

PURPOSE The purpose of this study was to survey the prosthodontists of the American College of Prosthodontists (ACP) and the American Academy of Maxillofacial Prosthetics (AAMP) to identify the most commonly used implant both during their training and currently in practice, and to evaluate overall restorative preference. Participants were asked to rank criteria that make an implant company desirable and important features when selecting an implant. MATERIALS AND METHODS An electronic survey was emailed to 1,739 members of the ACP and AAMP. RESULTS The majority of respondents (79%) were trained using Nobel Biocare brand implants, which was also the brand most often selected by participants for use in all regions of the oral cavity (34% to 39%, location dependent). Abutment preferences varied by area: incisors and canines (29%) and highly esthetic areas (53%) were more likely to be restored with custom milled zirconia abutments, while prefabricated titanium abutments were preferred for premolars and molar areas. Conventional loading was most often applied, ranging from 95% in medically compromised patients to 55% in esthetic areas. The majority of participants (86%) used Locator attachments for complete overdenture restorations. Also, respondents selected an implant company based on features and literature support versus cost and customer service. The implant features deemed most important were the design of the internal connection and ease of finding replacement parts; thread design and variety of abutments were deemed least important. Respondents reported that while implant planning software was used, they rarely/never order the concurrent surgical guide. CONCLUSION Within the studys limitations, the majority of prosthodontists select implants based on training, features, and literature support.