PubMed Health⌕ Search

Biomedical subjects

James C Lemon

Publications and source records attributed to James C Lemon.

17 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↗
PubMed2006

Digital imaging in the fabrication of ocular prostheses.

Several ocular and orbital disorders require surgical intervention that may result in ocular defects. The associated psychological effect of these defects on the patient requires immediate management and rehabilitation intervention by a team of specialists. The role of the maxillofacial prosthodontist in fabricating an ocular prosthesis with acceptable esthetics to restore facial symmetry and normal appearance for the anophthalmic patient becomes essential. This article presents a technique for fabricating ocular prostheses using the advantages of digital photography.

Eye, Artificial↗
PubMed2006

Stent fabrication for graft immobilization following wide surgical excision of myofibroblastic sarcoma of the buccal mucosa: a clinical report.

Sarcomas of the head and neck are rare tumors derived from cells of mesenchymal origin. This article briefly discusses the epidemiology, etiology, and classification of head and neck sarcomas. Emphasis is placed on myofibrosarcoma, a malignant tumor of the myofibroblasts. Histologic criteria, prognostic factors, and the multidisciplinary management of these tumors are reviewed. A situation of a surgically excised myofibrosarcoma of the buccal mucosa is reported. In this patient, a stent was fabricated to stabilize a split-thickness skin graft used for the buccal mucosa reconstruction.

Adult↗
PubMed2005

Mutans streptococci in xerostomic cancer patients after pilocarpine therapy: a pilot study.

OBJECTIVES: Opiod- and/or radiation-induced xerostomia in cancer patients is frequently associated with elevated levels of cariogenic mutans streptococci (MS). STUDY DESIGN: In a single-center, single blind 8-week clinical trial at The University of Texas M. D. Anderson Cancer Center, and from an initial sample of 32 patients, we evaluated MS counts in 28 cancer patients receiving chronic analgesic treatment for cancer pain. All patients received escalating doses of pilocarpine (Salagen) tablets, either 2.5 mg to 5 mg or 5 mg to 7.5 mg qid for 6 weeks, followed by placebo qid for a 2-week washout period. Whole resting saliva flow rates (g/5 min) and MS counts were evaluated at pretreatment, 3 weeks, 6 weeks, and 8 weeks. MS samples were obtained by 5-mL saline rinse (15 sec) at each visit prior to sialometry. RESULTS: In 19 patients (59%), MS counts exceeded 10(5) CFU/mL. At the end of the 6-week trial, 96% of patients showed a positive response to pilocarpine following a 30-minute postdosing evaluation (P=.001). MS counts were lower in 17 patients, higher in 6 patients, and nondetectable before and after pilocarpine in 5 patients (P=.03). CONCLUSION: The reduced MS counts associated with improved saliva flow rates following pilocarpine therapy in this short-term pilot study are encouraging, but further investigation in a larger group of patients over a longer study period is indicated.

Analgesics, Opioid↗
PubMed2005

Facial prosthetic rehabilitation: preprosthetic surgical techniques and biomaterials.

PURPOSE OF REVIEW: Attention 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 FINDINGS: Evidence 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. SUMMARY: This review presents current concepts regarding facial prosthetic rehabilitation of patients with head and neck cancer and facial prosthetic biomaterials.

Biocompatible Materials↗
PubMed2004

Obturation of the partial soft palate defect.

A partially resected soft palate represents a more significant challenge for effective prosthodontic obturation than for complete soft palate resections. In fact, for some patients it may not be possible to prosthetically rehabilitate with partial soft palate resections, resulting in velopharyngeal dysfunction, which could include hypernasal voice quality and nasal regurgitation of food and liquids. This article presents a technique for recording the contours of a partial soft-palate defect for prosthetic obturation.

Denture Bases↗
PubMed2004

In vitro effect of microwave irradiation on the retentive force of magnets.

STATEMENT OF PROBLEM: Few studies have addressed the possible effect(s) of microwave irradiation on the magnetic properties of "permanent" magnets during the fabrication of dental and maxillofacial prostheses. PURPOSE: The objective of this study was to investigate the influence of microwave irradiation energy on the retentive force of a magnetic attachment system used in maxillofacial prosthetic rehabilitation. MATERIAL AND METHODS: A heat-polymerized PMMA disk (6 cm in diameter) was fabricated. Seven magnets were placed around the wafer in a circumferential fashion: 1 in the center and 6 surrounding it. The 7 magnets were spaced 2 cm from their respective centers. Seven heat-polymerized PMMA cylinders were also used, and a magnet (counter-magnet) was placed in the center of each even with the cylinder's surface. Once the investment had set (45 minutes after mixing), the 7 counter-magnets in the cylinders were placed against the 7 magnets in the acrylic wafer. A second mixture of investment material was added. The flasks were separated, and the acrylic wafer was removed to accommodate the 7 counter-magnets in the base mold in the same geometric configuration and to serve as a "spacer" for the silicone material. A 1:1 mixture of medical grade elastomer (MDX4-4210) and medical adhesive silicone (type A) was packed and compressed, the molds were reclamped, and the excess silicone was removed. The elastomer/silicone wafer was packed and compressed into the test and base molds, the molds were reclamped, and excess silicone was removed. The first group of magnets, designated Group A, received microwave irradiation for 5 minutes at low power (112 W). This procedure was repeated for each group of magnets at the following polymerizing times (n=14): Group B, 10 minutes; Group C, 15 minutes; Group D, 20 minutes; Group E, 25 minutes; Group F, 30 minutes; and Group G, 35 minutes. Measurements of retentive force (N) at 10 mm/min ramp rate of speed of separation was conducted. The specimen rate read 5.0 points/second. Data were analyzed using a 1-way analysis of variance (alpha=.05); individual mean values were compared using the Tukey test (alpha=.05). RESULTS: There were no statistical differences in retentive force between groups D, E, and F (20, 25, and 30 minutes, respectively) or between groups A, B, C, D, F, and G (5, 10, 15, 20, 30, and 35 minutes, respectively). When the microwave-irradiated groups A through G were compared with the control group, there was a significant difference (P<.05) in retentive force (N). Group E (25 minutes) showed the largest reduction of retentive force (0.3 N, a reduction of 12%). CONCLUSION: If a prosthesis is processed using a microwave and contains samarium cobalt magnets, the retentive force may be reduced up to 12% under specific conditions.

Cobalt↗
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↗
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↗
PubMed2003

Custom modification of the Blom-Singer tracheostoma valve housing.

A technique is presented for modifying the Blom-Singer tracheostoma valve housing to improve peristomal skin adherence for hands-free tracheoesophageal speech production following total laryngectomy. The finished product is thin, flexible, and maintains enhanced tear strength. The edges of a standard housing device for the Blom-Singer valve are trimmed to allow for better accommodation to the tissue surface without distortion. A punch biopsy instrument is used to cut uniform holes around the housing device to allow for permeation of the silicone mixture for better mechanical adherence of the materials.

Adhesives↗
PubMed2003

How I do it: a technique for oral wound irrigation following maxillectomy and mandibulectomy.

BACKGROUND: Numerous devices have been recommended for ensuring appropriate hygiene and care of wounds resulting from maxillectomy and mandibulectomy. This article describes an irrigation device for use in the oral cavity after these procedures. METHODS: The system consists of: a prepackaged, disposable, 50-cc piston syringe; a nonconductive connecting tube; and, a saliva ejector that can be assembled for oral irrigation. RESULTS: The modified piston syringe allows physicians, nurses, and patients to efficiently irrigate mucosal wounds, maxillary or mandibular defects, and oropharyngeal or oral and pharyngeal wounds. CONCLUSION: This system is efficacious, more adaptable, and less expensive than other self-irrigating gravimetic instruments and is thus recommended for use in patients who have undergone maxillectomy or other ablative procedures in the oral cavity.

Humans↗
PubMed2002

Modification of the Barton button for tracheoesophageal speech: an innovative maxillofacial prosthetic technique.

Laryngectomized, tracheoesophageal speakers who achieve hands-free speech wear a special breathing valve to automatically shunt air into the pharyngoesophagus for speech production. The standard method of attachment is adherence to the peristomal skin with glues and adhesives. The Barton button is a simpler, more efficient alternative that provides intraluminal attachment within the trachea. Although the device is appealing, constraints in standard design and dimensions have limited its success. This article presents a technique for modification of the Barton button to increase its successful use by tracheoesophageal speakers.

Equipment Design↗
PubMed2002

Anterior key method for indexing orbital prostheses.

This article describes a predictable method for indexing the ocular portion of an orbital prosthesis. Because indexing is performed from the anterior aspect of the cast, damage is minimized, fewer modifications are required, and the mold can be preserved for repeated use.

Acrylic Resins↗
PubMed2002

Effect of opacifiers on color stability of pigmented maxillofacial silicone A-2186 subjected to artificial aging.

PURPOSE: This study was designed to determine the effect of opacifiers used at different ratios on the color stability of pigmented A-2186 silicone maxillofacial elastomers and to evaluate the color spectrophotometrically before and after artificial aging. MATERIALS AND METHODS: Sixty experimental groups of elastomers were made using various concentrations (5%, 10%, and 15%) of 4 opacifiers (Georgia kaolin powder neutral, kaolin powder calcined, Artskin white, and dry pigment titanium white) with 1 of 5 dry earth cosmetic pigment groups (no pigment [control], red, yellow ochre, burnt sienna, and a mixture of all pigments). Five specimens of each elastomer were tested, for a total of 300 specimens. All specimens were placed in an aging chamber and artificially aged by exposure to light, water spray, fluctuating temperatures, and humidity. CIE L*a*b* values were measured by spectrophotometer. The color differences (Delta E*) at various exposure energies (150, 300, and 450 kJ/m(2)) were subjected to 4-way analysis of variance with repeated measures (super ANOVA). Mean values were compared with Tukey-Kramer intervals calculated at the 0.05 significance level. RESULTS: The trained human eye can detect color changes (Delta E*) greater than 1.0. Adding all pigments to any of the kaolin groups did not protect silicone A-2186 from color degradation over time. Mixing red pigment in all groups at all times drastically increased DeltaE* values ranging from 0.1 to 1.3 up to 16.6 to 49.6. Yellow ochre had an effect only with 10% and 15% concentrations of kaolin powder calcined, increasing the value of Delta E* to greater than 1.0. Burnt sienna had an effect only with a 15% concentration of kaolin powder calcined, increasing the value of Delta E* at 300 and 450 kJ/m(2) to greater than 11.0. At the 5% concentration, kaolin powder calcined had the smallest color changes, followed by, in order, dry pigment titanium white, Artskin white, and Georgia kaolin. At the 10% concentration, Artskin white had the smallest color changes, followed by, in order, dry pigment titanium white, kaolin powder calcined, and Georgia kaolin. At the 15% concentration, Artskin white again had the smallest color changes, followed by, in order, dry pigment titanium white, Georgia kaolin, and the kaolin powder calcined. The smallest color changes in each kaolin group were at the 10% concentration for Artskin white, dry pigment titanium white, and kaolin powder calcined and at the 5% concentration for Georgia kaolin. CONCLUSIONS: Mixing dry earth cosmetic pigments with opacifiers did not protect silicone A-2186 from color degradation over time, especially in the case of red pigment. The group in which pigments were mixed with 10% Artskin white had the smallest color changes over time, followed by, in order, the groups in which pigments were mixed with 10% dry pigment titanium white, 10% kaolin powder calcined, and 5% Georgia kaolin. Red pigment had a significant effect on all opacifiers, especially Georgia kaolin and kaolin powder calcined. Yellow ochre and burnt sienna had an effect only on 15% kaolin powder calcined. Among all the pigment groups tested, yellow ochre remained the most color stable over time.

Analysis of Variance↗