Biomedical subjects

Trakol Mekayarajjananonth

Publications and source records attributed to Trakol Mekayarajjananonth.

6 recordsLinked to original sources

PubMed2006

Interactions of pigments and opacifiers on color stability of MDX4-4210/type A maxillofacial elastomers subjected to artificial aging.

STATEMENT OF PROBLEM: The color instability and degradation of maxillofacial elastomers limit the function and cosmetic quality of facial prostheses. PURPOSE: The purpose of this study was to measure the interactions of oil pigments plus dry earth opacifiers at 5%, 10%, and 15% by volume in stabilizing the color of MDX4-4210/type A silicone elastomers before and after artificial aging. MATERIAL AND METHODS: In the first part of the study, each of 5 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, dry pigment titanium (Ti) white, or Ti white artists' oil color) at 10% concentrations were combined with each of 5 oil pigment types (no pigment, cadmium-barium red deep, yellow ochre, burnt sienna, or a mixture of the 3 pigments), for a total of 25 experimental groups of elastomers. In the second part of the study, 50 experimental groups of elastomers were made by combining 1 of 5 opacifiers at 5% and 15% concentrations with 1 of 5 oil pigments as in Part 1. Five specimens of each elastomer were tested, for a total of 375 specimens. In each part of the study, all specimens were aged in an artificial aging chamber. CIE L*a*b* values were measured by a spectrophotometer. The color differences (DeltaE*) were subjected to repeated-measures analysis of variance. Mean values were compared by Tukey-Kramer intervals (alpha = .05). RESULTS: In Part 1, when the opacifiers were tested at 10% concentration, Ti white oil color had the most color change, and dry pigment Ti white had the least; all other opacifiers were not significantly different from each other. In Part 2, at 5%, Ti white oil color had the most color change; all other opacifiers were not significantly different from the others. At 15%, Ti white oil color again had the most color change, followed by Artskin white, kaolin powder calcined, and Georgia kaolin; Ti white dry earth pigment had the least color change. Overall, 5% Artskin white had less color change than the 15%, whereas 15% dry pigment Ti white had less color change than the 5% (P < .001). The 5% and 15% of other opacifiers were not significantly different. CONCLUSIONS: At all 3 concentrations, oil pigments mixed with opacifiers helped protect the MDX4-4210/type A silicone elastomer from color degradation over time. Dry pigment Ti white remained the most color stable over time, followed by the pigments mixed with kaolin powder calcined, Georgia kaolin, Artskin white, and Ti white artists' oil color.

Barium Sulfate↗

PubMed2005

The influence of water storage on durometer hardness of 5 soft denture liners over time.

PURPOSE: This laboratory study investigated the influence of water storage on the durometer hardness of 2 RTV and 3 HTV soft denture liners over a 1-year period. MATERIALS AND METHODS: Five soft denture liners were used: 2 HTV silicone rubber (Luci-Sof and Molloplast-B), 1 RTV silicone rubber (Tokuyama), 1 HTV polyphosphazene (Novus), and an RTV plasticized acrylic (PermaSoft) that uses a surface sealer. They were processed following manufacturers' instructions, cured, and stored in tap water at 37 degrees C. The water was changed every 2 weeks. Five durometer A hardness measurements were made at logarithmically spaced intervals of 16.7 minutes, 27.8 hours, 11.6 days, 34.7 days, 115 days, and 347 days. Repeated measures analysis of variance (MANOVA), one-way analysis of variance (ANOVA), Pillai trace statistic, the difference scores (last-first) among the groups, and the Tamhane T2 multiple comparison test were used to compare the groups over time, all on SPSS V. 7.5 and 9.0. RESULTS: The order of highest initial indentation hardness was Luci-Sof, Molloplast-B, Novus (H(D)= 38 to 33). Tokuyama and PermaSoft as a group were softer (H(D)= 18 to 22). Tokuyama Soft Relining changed the least over 347 days, followed by Luci-Sof, Novus, Molloplast-B, and PermaSoft in that order (p < or = 0.05). Within the PermaSoft group, sealer applied only once changed the least over 347 days, followed by no sealer, and then sealer applied every month (p < 0.0005). CONCLUSIONS: After 347 days of water storage, Tokuyama had the lowest indentation hardness changes, followed by Luci-Sof, Novus, PermaSoft with sealer applied once; Molloplast-B, PermaSoft without sealer; and PermaSoft with sealer applied every month. All HTV soft denture liners had higher indentation hardness than RTV liners initially. After 347 days, PermaSoft without sealer and with sealer every month became the hardest.

Analysis of Variance↗

PubMed2005

The effect of compressive cyclic loading on retention of a temporary cement used with implants.

Masticatory forces cause fatigue to cement-retained crowns and abutments and may adversely effect retention. The relation between the number of load cycles and the retentive forces is important. This study evaluated the effect of compressive cyclic loading on the retentive forces of a temporary cement used to retain implant crowns and the relationship between load cycles and retentive forces. Ten castings and implant abutments were cemented with zinc oxide-eugenol temporary cement. The retentive force necessary to dislodge the casting from the abutment was determined before and after the application of 2 Hz of vertical off-axis 3-mm sinusoidal-type compressive cyclic loading between 20 and 130 N for 500000, 1000000, and 5000000 cycles. These forces were equivalent to approximately 6 months, 1 year, and 5 years of human mastication. Data before and after the applied loading were analyzed with a paired sample t test (alpha = 0.05). The retentive forces of the 3 groups were analyzed by 1-way analysis of variance and post hoc by Scheffé multiple comparison (alpha = 0.05). The relation of the loading and the altered retentive forces were analyzed with the Pearson correlation coefficient. Compressive cyclic loading reduced the retentive forces significantly in all groups (P = .000). The retentive forces were reduced 16.75%, 18.73%, and 19.68% during the applied loading cycles of 500000, 1000000, and 5000000. All reduced retentive forces were not significantly different (P = .792). Although cyclic loading reduced the retentive forces, the increased cycles had little relationship (R = 0.119) to the decreased retentive forces of the temporary cement. The relationship between occlusal loading and retentive force can influence the choice of a temporary cement for a particular clinical situation.

Compressive Strength↗

PubMed2003

A mold-making procedure for multiple orbital prostheses fabrication.

Traditional methods of fabricating orbital prostheses rely on the "lost wax" technique to produce a realistic representation of the sculpted pattern produced in the defect. The usual constituents of the mold that reproduces the subtleties of the palpebral fissure are often minute, making them prone to fracture and subsequent dissolution by repeated attempts at pressing each prosthesis. The following method provides a mold resistant to these problems with light-polymerized resin surrounding the palpebral part of the orbital mold.

Acrylic Resins↗

PubMed2002

Alternative retention for an implant-retained auricular prosthesis.

The introduction of intraoral endosseous implants was inevitably followed by their external use in maxillofacial prosthodontics. Bar and clip attachments provide satisfactory retention for auricular prostheses, although the bar may inhibit patient hygiene by limiting access to the defect area. A simple clinical and laboratory technique to enhance the retention of an implant-retained auricular prosthesis is described, with custom-made stud attachments used for retention. Improved access for hygiene is provided. A clinical case is presented.

Adult↗

PubMed2002

The functional and esthetic deficit replaced with an acrylic resin gingival veneer.

Periodontal attachment loss in the maxillary anterior region can often lead to esthetic and functional clinical problems including disproportional and elongated clinical crowns, visible interdental embrasures, and altered linguoalveolar-labiodental consonant production. Assuming fixed prosthetic reconstructions will be chosen to treat these areas, it becomes a hygienic compromise to fill these areas in with porcelain. In the presence of these problems, an acrylic resin gingival veneer is an easily constructed, inexpensive, and practical device to optimize the esthetic and functional outcome in these special situations while permitting cleansibility of the prosthesis and supporting tissues. This article presents a step-by-step technique for the fabrication of a gingival veneer.

Acrylic Resins↗