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Results for “Maxillofacial Prosthesis”

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At least 595 records · Page 33Linked to original sources
PubMed2003

Facial moulage: the effect of a retarder on compressive strength and working and setting times of irreversible hydrocolloid impression material.

STATEMENT OF PROBLEM: Irreversible hydrocolloid is widely used as an impression material for fabrication of extraoral maxillofacial impressions. A disadvantage of irreversible hydrocolloid, however, is its limited working time. PURPOSE: This study tested the compression strength (elastic recovery) and working and setting times for an irreversible hydrocolloid impression material after a retarder was added. MATERIAL AND METHODS: The irreversible hydrocolloid (Jeltrate) was mixed with water in a standard water/powder mixture of 18 mL (1 unit) of water and 7 g (1 unit) of the impression material. Test specimens (n = 3) were prepared by adding 2, 4, 6, and 8 drops of monobasic sodium phosphate (the retarder) to each. Three other specimens, to which no retarder was added, served as the control. Specimens were prepared according to the American National Standards Institute/American Dental Association's specification no.18 guidelines for irreversible hydrocolloid impression material. Immediately after the specimens were prepared, the flat end of a polished rod of poly(methyl methacrylate) was placed in contact with its exposed surface and quickly withdrawn. The working-time experiment was a pass/fail test conducted 30 seconds before the initial setting time. The initial setting time was established as extending from the start of the mix to the time when the impression material no longer adhered to the end of the rod. To determine how the compressive strength of the modified irreversible hydrocolloid (with retarder added) compared with that of the control, the mean stress at maximum load (Mpa) was analyzed. The compressive strength (MPa) was calculated. Statistical analysis consisted of descriptive statistics and regression analyses. RESULTS: The results of this experiment demonstrated that the elastic recovery of the irreversible hydrocolloid did not change with the addition of sodium phosphate (2 to 8 drops). The percent recovery with was 95.95% +/-.42%, 96.33% +/-.82%, and 96.28% +/-.53% for 0 (control), 2 and 8 drops, respectively. Average setting times for control specimens were 2 minutes 20 seconds +/- 0 seconds for the control specimen (0 drops) to 11 minutes 20 seconds +/- 1 minute 50 seconds for the test specimen with 8 drops. There was a direct relationship (R(2) = 0.85) between the number of drops added and the setting time. All control specimens and test specimens containing 2, 4, 6, and 8 drops of monobasic sodium phosphate produced acceptable levels of elastic recovery (> or =95%). CONCLUSION: Within the limitations of this study, predictable longer working and setting times were demonstrated for the irreversible hydrocolloid specimens with 1 to 8 drops of the sodium phosphate solution tested. The specimens with 8 drops of retarder solution exhibited variable setting times and would not be suitable for clinical use. The compressive strength of the modified irreversible hydrocolloid material tested was compromised because of the addition of sodium phosphate solution; however, recovery from deformation remained satisfactory as retarder solution was added.

Alginates↗
PubMed1995

Practice and malpractice expenses in maxillofacial prosthetics.

Recent changes in Medicare reimbursement methods have made the estimation of specific practice and malpractice expenses in maxillofacial prosthetics more important. New reimbursement models such as the resource-based relative value scale used by Medicare and an increasing number of private carriers require accurate and specialty-specific values for these parameters. The Health Care Financing Administration's estimates of practice expense values in all specialties of medicine are significantly lower than those suspected in maxillofacial prosthetics. There is concern that the assignment of erroneous values in maxillofacial prosthetics could lead to inadequate reimbursement. Because the American Dental Association provides only aggregate specialty values, a survey of the general membership of the Academy of Maxillofacial Prosthetics was undertaken to determine these values more accurately. Practice expense values were found to be significantly higher than those in medicine, whereas malpractice expense values were lower. In addition, practice expense values in the survey were found to be greater than the ADA's aggregate specialty calculations.

American Dental Association↗
PubMed1995

Technique for magnet replacement in silicone facial prostheses.

Magnets are often used in silicone facial prostheses for retention. However, these magnets may need to be replaced or repositioned as a result of loss, wear, or poor initial placement. Replacement can be easily accomplished by use of a nylon mesh material and a simple laboratory technique.

Humans↗
PubMed1995

Synthetic casting tape as a facial impression tray material.

A procedure is described that uses thermoplastic synthetic casting tape for fabrication of facial impression trays. Once used, these trays can be disinfected without degradation of the tray material, which allows for storage and later use.

Alginates↗
PubMed1995

Attachments used for implant-supported facial prostheses: a survey of United States, Canadian, and Swedish centers.

A survey was conducted of one Swedish, three Canadian, and 24 United States centers that provide implant-supported facial prosthetic treatment. All centers responded to the survey. A total of 357 patients began treatment. Of those, 338 completed treatment: 165 in Sweden, 131 in the United States, and 42 in Canada. The incidence of facial sites treated with implant-supported prostheses indicated that the auricular (72%) region was the most common site, followed by the orbital (20%), nasal (6%), and combination (2%). Clips were the predominant mechanism used to retain auricular prostheses. Orbital prostheses were fabricated with a wider variety and combination of attachments. Nasal and combination prostheses were too few to elicit any specific trends of attachment use. A variety of manufacturers' attachments were used for clip, magnet, and miscellaneous attachments to retain implant-supported facial prostheses. Results of this survey indicate a need for further investigation regarding the most efficacious attachment method to serve patients treated with implant-supported facial prostheses.

Canada↗
PubMed1995

Color stability of facial prostheses.

The limited service of facial prostheses is the result of degradation of the elastomer and color instability. Deterioration may be caused by many factors, which include environmental exposure and changes in humidity. This investigation assessed the efficacy of an additive, intrinsic, broad-spectrum ultraviolet light absorber on the color stability of a pigmented facial elastomer. Samples were weathered artificially and outdoors at exposure levels of radiant energy of 150 to 450 kJ/m2. The samples changed color slightly but perceptibly. Artificial aging caused a greater change than outdoor aging. The ultraviolet light absorber UV-5411 did not protect the samples from color changes.

Absorption↗
PubMed1975

Dynamic orificial resin adjustable nasal stents.

A technique is described for use of intranasal acrylic resin stents with finger springs and/or orthodontic jackscrew expanders for initiating and maintaining a desired amount of opening in the presence of scar tissue or grafts.

Acrylic Resins↗
PubMed1978

Vinyl chloride concentrations in maxillofacial prosthetics laboratories.

Air sampling was conducted in three maxillofacial laboratories to determine whether vinyl chloride, a carcinogen, was released during the formulation of polyvinylchloride facial prostheses. Results show that time-weighted average exposures of technicians were less than 0.1 ppm, a concentration meeting current U.S. Department of Labor standards.

Air↗
PubMed1978

Physical and mechanical behavior of polyurethane elastomer formulations used for facial prostheses.

The initial results of this study of the physical and mechanical behavior of polyurethanes used for facial prostheses are presented. The parameters studied were surface hardness, modulus of elasticity (M), strength (S), percentage of elongation, and S/M ratio. Results showed that the physical and mechanical behavior of the polyurethanes can be altered by variations in the basic composition of the material accomplished through changes in the ratio of Part A to Part B and by the addition of catalysts. Properties of compositions with low quantities of Part B (isocyanate) and no catalyst reached or approximated those parameters proposed as ideal goals to simulate living tissue. When preparing polyurethane material, proper mixing is essential to avoid entrapment of air and phase separation of the catalyst. These conditions, which may render the prostheses less durable, are masked by the addition of colorants in the prearation of a sample for clinical application.

Chemical Phenomena↗
PubMed1989

Fabrication of facial prostheses by applying the osseointegration concept for retention.

Initial clinical studies applying the osseointegration concept for retention of facial prostheses have been encouraging. The results of these preliminary investigations indicate new treatment possibilities with facial prostheses anchored to the cranial skeleton by osseointegrated implants. Osseointegrated rehabilitation of the maxillofacial prosthetic patient presents the potential for overcoming many of the disadvantages associated with conventional retentive methods. Fabrication and support for facial prostheses by using osseointegrated implants for retention are described.

Facial Bones↗
PubMed1996

The effect of primers and surface characteristics on the adhesion-in-peel force of silicone elastomers bonded to resin materials.

Facial prostheses, when used in conjunction with craniofacial implants, require a retentive matrix to hold attachments and/or magnets. The retentive matrix is usually fabricated with autopolymerizing acrylic resin or a visible light-polymerized resin. The purpose of this study was to compare the adhesion-in-peel force of a silicone adhesive to autopolymerizing polymethyl methacrylate and light-polymerizing urethane dimethacrylate gel with two surface textures: (1) pumice polish only or (2) pumice polish and bead retention, and two surface primers: (1) Dow Corning 1205 primer or (2) Dow Corning S-2260 primer. The 1205 primer produced an adhesion-in-peel force that was statistically significantly stronger (p < 0.05) regardless of which type of resin or surface preparation was used.

Adhesiveness↗