ABSTRACT
STATEMENT OF PROBLEM: Maxillofacial prostheses require frequent replacement because the elastomer and its color additives undergo changes. PURPOSE: This study attempted to determine whether predictable color changes occur when 3 pigments are individually incorporated into a specific silicone elastomer. MATERIAL AND METHODS: The materials included an RTV elastomer; 1 natural inorganic pigment, burnt sienna; and 2 synthetic organic pigments, Hansa yellow and alizarin red. Eight test groups of 10 polymerized specimens were established. Groups 1 and 2, acting as the control, involved only the elastomer. Groups 3 and 4 were composed of elastomer and burnt sienna. Groups 5 and 6 consisted of elastomer and Hansa yellow. Groups 7 and 8 comprised elastomer and alizarin red. Odd-numbered groups were assigned to a test site in Miami, Fla., whereas the even numbered groups went to Phoenix, Ariz. Specimens weathered in Miami and Phoenix received sunlight exposures of 1305.7 MJ/m2 and 1310.2 MJ/m2, respectively, over time. Before and after weathering, the L* a* b* color parameter (DeltaE*) of each specimen was determined spectrophotometrically. RESULTS: Mean color changes that occurred in Arizona were larger than those produced in Florida. Specifically, these differences ranged from 0.4 (alizarin red groups) to 2.36 units for the 2 unpigmented control groups. Other differences showed significance for the unpigmented (P=.001), burnt sienna (P=.006), and Hansa yellow groups (P=.001). CONCLUSION: Outdoor weathering tests in which documented ASTM methods were used provided a valid baseline for future research on color changes in maxillofacial prostheses.
Subject(s)
Pigments, Biological/chemistry , Silicone Elastomers/chemistry , Analysis of Variance , Anthraquinones/chemistry , Anthraquinones/radiation effects , Color , Forecasting , Humans , Materials Testing , Maxillofacial Prosthesis , Pigments, Biological/radiation effects , Polymers/chemistry , Polymers/radiation effects , Prosthesis Coloring , Silicone Elastomers/radiation effects , Spectrophotometry , SunlightABSTRACT
PURPOSE: Effective taper criteria must define a realistic, measurable goal that the student can visualize and achieve. Six degrees is widely accepted as the taper criterion for the full veneer crown preparation. However, studies show the actual taper of most preparations to be greater than 12 degrees. The purpose of this study was to determine whether 12 degrees is an effective taper criterion for the full veneer crown preparation in preclinical prosthodontics instruction. MATERIALS AND METHODS: A group of 191 full veneer crown preparations with 6 degrees as the taper criterion, and a group of 130 full veneer crown preparations with 12 degrees as the taper criterion were evaluated. All preparations were accomplished by preclinical dental students working on typodonts under examination conditions. RESULTS: The overall mean taper for each group exceeded the targeted criterion. The overall mean taper for the 6 degrees group was 14,490. When 12 degrees was the criterion, the overall mean taper was 15,580. The t test results indicate significant differences (p < .0001) between the targeted criterion and the actual preparation mean taper in all samples except one: the faciolingual measurements in the 12 degrees group. The faciolingual measurement of 12,920 was not statistically significantly different (.0542) from the targeted criterion of 12 degrees. CONCLUSION: The use of a 12 degrees taper criterion did not result in preclinical students achieving the goal of a 12 degrees taper. However, a 12 degrees criterion is more realistic than a 6 degrees criterion for full veneer crown preparations.
Subject(s)
Crowns , Dental Veneers , Tooth Preparation, Prosthodontic/methods , Humans , Reference StandardsABSTRACT
PURPOSE: This literature review provides information about pigments used for facial and somatoprostheses. MATERIAL: This information includes common pigment and index names and numbers, lightfastness categories, chemical type and class, and the chemical formulas of the common pigments used in maxillofacial prosthetics. CONCLUSION: It can be deduced from this review that the pigments used with silicone elastomers do exhibit a color change, and that a color change is to be expected.
Subject(s)
Maxillofacial Prosthesis , Pigments, Biological/chemistry , Prosthesis Coloring , Silicone Elastomers/chemistry , Humans , Light , Pigments, Biological/classification , Pigments, Biological/radiation effects , Silicone Elastomers/radiation effects , SunlightABSTRACT
A facial prosthesis can be retained by bone-anchored implants and by a retentive bar. Because tissue response is critical around the abutments, the retentive bar should be constructed so that it is comfortable, conveniently hygienic, and designed without compromising the contours of the prosthesis.
Subject(s)
Ear, External , Nose , Orbit , Prostheses and Implants , Humans , Internal Fixators , Osseointegration , Prosthesis Design , Prosthesis FittingABSTRACT
Osseointegrated implants can be positioned on the nondefect side of a midline maxillary resection if there is sufficient residual bone. Axial loading of the implants is difficult because the axis of rotation for an obturator prosthesis is located along the palatal margin of the defect. Rotation of the prosthesis due to a class I lever will encourage stresses within the implants and the bone surrounding the implants on the nondefect side, and this may be detrimental. Placement of implants within the defect will prevent rotation of the prosthesis and encourage axial loading of the implants.
Subject(s)
Bone Transplantation , Dental Implantation, Endosseous , Dental Implants , Jaw, Edentulous/surgery , Maxilla/surgery , Bone Transplantation/methods , Denture Design , Denture, Complete, Upper , Humans , Palatal Obturators , Prosthesis Design , TitaniumABSTRACT
Certain swallowing disorders characteristically may follow head and neck surgeries and neurologic disorders. Aspiration is one of the possible symptoms of dysphagia. Since aspiration can be life-threatening, prosthodontists should help to identify patients who aspirate. This article describes the normal swallowing physiology, the pathophysiology of swallowing disorders, and the prosthetic role in the treatment of patients experiencing head and neck surgical operations and neurologic disorders that may cause aspiration.
Subject(s)
Deglutition Disorders/physiopathology , Inhalation/physiology , Deglutition/physiology , Deglutition Disorders/etiology , Deglutition Disorders/therapy , Humans , ProsthodonticsABSTRACT
An in vivo study using 48 disease-free male Lewis rats was conducted to determine the histologic difference between an alloplastic cranial prosthesis made with a monomer directly from the manufacturer and a triple-distilled monomer. The histologic difference in the tissue reaction between a cranial prosthesis sterilized with ethylene oxide and one sterilized with cobalt-60 irradiation was also evaluated. Histologic tissue biopsies of the cranium and brain tissues were obtained at 1, 3, 6, and 12 weeks. Tissue biopsies after the third week showed minimal inflammation and the microscopic findings were consistent with the reparative stage of wound healing. The findings also suggest that distillation of the monomer in heat-polymerized methyl-methacrylate is unnecessary for cranial prostheses. Cobalt-60 irradiation was found to be an effective alternative method of sterilization for such prostheses.
