Evaluation of the color stability of three maxillofacial silicone materials after exposure to beverages: An in vitro study.

Purpose: Oral cancer often requires treatments like surgical intervention, involving surgical resection of lips and other facial parts. For those patients, prosthetic rehabilitation following surgery promotes social reintegration. This study explores the color stability of various commercially available silicone materials for facial prostheses when exposed to everyday beverages like coffee and tea. The hypothesis is that these beverages can induce color changes in silicones, simulating conditions of daily use. Material and methods: A total of 90 specimens were fabricated. There were 30 specimens deefor each of 3 nonpigmented silicone elastomers: Silfy, A-2186-F and VST-50 and were immersed in tea or coffee at drinking temperature and evaluated for color changes at time points of 0 h, 1 h, and 6 h. The color was measured with a colorimeter that used the CIE L*a*b* system and the color change ΔΕ was calculated to quantify the color change. Statistical analysis was performed by using the Kruskal-Wallis test, the Mann-Whitney U test, and the Wilcoxon signed-rank Test. The threshold for statistical significance was P < .05. Results: Color change was observed for each of the silicones exposed to the beverages (P < .05). The value of ΔE was significantly higher for A-2186-F compared with VST-50 and Silfy (P < .05 in all beverages at 6 h). The color of the elastomers progressively changed while immersed in the beverages over 6 h. The change in color was significantly greater for coffee compared with tea (P < .05). Conclusions: The color stability of nonpigmented silicone elastomers is inherently low, which contributes to the overall color change of silicone prostheses when they are exposed to beverages that contain pigments. The elastomer A-2186-F had greatest values of ΔE among the materials tested. Color changes of silicone prostheses can be lessened by selecting materials with consideration of color stability to improve their longevity and extend their period of use.

Digital design of open hollow obturator framework using existing dentures: A dental technique.

Computer-aided design and computer-aided manufacturing technology has been applied to the fabrication of maxillary obturator frameworks, both directly and indirectly. However, with earlier techniques, it was not possible to accurately determine the position of the framework conforming to the palate, an issue that has been resolved in current fabrication methods. Using the patient's existing denture, prosthodontists can determine where the framework should be positioned in the defect area. This allows the obturator bulb to be hollowed, thereby reducing weight and making adjustment easier. The most appropriate position for the finish line can be determined by accurately establishing the arrangement of the artificial teeth as well as the most appropriate polishing surface morphology. In maxillofacial prosthetics, restoring proper articulation and the swallowing function through rehabilitation is important, and determining the proper palatal morphology enables good tongue movement and facilitates the restoration of adequate function. The lighter weight contributes to protecting the remaining teeth and improves patient comfort.

A 20-year clinical survey of radiotherapy prostheses at the Clinic for Maxillofacial Prosthetics of Tokyo Medical and Dental University Hospital.

PURPOSE: To identify secular trends in the use of radiotherapy prostheses in the Clinic for Maxillofacial Prosthetics at Tokyo Medical and Dental University Hospital and to ascertain patient characteristics and future needs. METHODS: The study included all patients who visited the clinic between January 1, 2000, and December 31, 2019. Data on numbers of cases, gender and age, numbers and types of radiotherapy prostheses, primary cancer site, and time required for prosthesis fabrication during the study period were collected from medical records and retrospectively analyzed. RESULTS: During the 20-year study period, 1,066 prostheses were fabricated for 1,135 cases. In most years, at least 60% of cases were male. The mean age increased from 60.6 to 67.1 years during the study period, and the number of cases older than 70 years increased over time. The most common cancer site was the tongue, and the most common type of radiotherapy prosthesis was a spacer. The mean time for spacer fabrication was 11 days. CONCLUSION: During a recent 20-year period, mean age and the proportion of elderly patients requiring savers increased. When treating elderly patients, prosthodontists responsible for fabricating radiotherapy prostheses must collaborate effectively with radiation oncologists.

Custom-made radiotherapy prosthesis for external and internal radiotherapy in a patient with lip cancer.

Definitive radiotherapy is an effective treatment for early-stage lip cancer. The goal of radiotherapy is to irradiate the cancer site effectively while protecting healthy surrounding tissue from the adverse effects of radiation. To this end, radiotherapy prostheses have been widely and effectively used. A maxillofacial prosthodontist working in collaboration with a radiation oncologist can create a custom-made radiotherapy prosthesis that minimizes adverse effects. This report demonstrates the successful use of spacers in external beam radiotherapy and brachytherapy in consideration of the patient's radiation therapy treatment plan and wearing conditions, ensuring adequate availability and preventing radiation-related complications.

An indirect-direct technique with hot water for fabricating a cast metal crown under an existing removable partial denture.

Fracture or carious lesions in an abutment tooth may require the fabrication of a crown under an existing removable partial denture. Typically, once the crown has been fabricated, the prosthesis will need to be modified or refabricated. However, if the partial denture is in good clinical condition, special techniques may be applied to make the new crown fit the existing prosthesis. This article describes a straightforward indirect-direct technique for fabricating a cast metal crown under an existing removable partial denture with hot water. The technique does not require expertise or any special device and can be performed chairside by general dentists.

Radiation attenuation properties of materials used to fabricate radiotherapy prostheses in vitro study.

PURPOSE: This study investigates the attenuation of radiation doses by four materials, heat-polymerized, and self-polymerized polymethyl methacrylate (PMMA), putty-type, and injection-type polyvinyl siloxane (PVS) impression material. This in vitro study should aid in the selection of dental materials for radiotherapy prostheses, thereby minimizing the possibility of radiotherapy side effects. METHODS: Specimens of each type were fabricated as a 5 × 5 cm squares with a thickness of 10 mm. Heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS impression material, and injection-type PVS impression material were selected. A calibration curve was created to determine the association of radiation doses and grayscale value. A linear accelerator was used to irradiate the specimens. The radiation doses above and below the materials were measured using radiochromic film dosimetry. After film irradiation, the pixel scale of color change was used to determine the radiation dose based on the created calibration curve. The results were exported to find average doses to calculate the percentage of the attenuated dose for a comparison of the four materials. RESULTS: The average attenuated doses of heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS, and injection-type PVS were 10.8%, 6.2%, 17.2%, and 14.2% respectively. CONCLUSION: PVS showed higher attenuating radiation exposure compared with PMMA.

Two-piece detachable interlocking mold for low-dose-rate brachytherapy: A dental technique for radiotherapy prosthesis fabrication.

Brachytherapy is a type of radiotherapy used to eradicate malignancies in the head-and-neck region. Early-stage mucosal carcinomas, such as carcinomas of the hard palate and gingival mucosa, can be treated with low-dose-rate brachytherapy by using a radiotherapy prosthesis called a mold. Prosthodontists play a significant role in the design and fabrication of these molds, which deliver therapeutic doses to the primary lesion and protect adjacent tissues from radiation exposure. However, planning and observing ongoing treatment is difficult for radiation oncologists because the shield part cannot be removed from the carrier part or requires an attachment to do so. This article describes a technique for fabricating a 2-piece detachable interlocking mold without any special attachment for low-dose-rate brachytherapy.

A custom-made brachytherapy applicator for recurrent endometrial and vaginal cancer: A dental technique for prosthesis fabrication.

The role of the prosthodontist in radiation therapy includes fabrication of radiation therapy prosthetic applicators. Brachytherapy is a form of cancer treatment that involves direct insertion of radioactive implants into the tissue. In the case of vaginal cancer, brachytherapy requires the radiation oncologist to use a device called an applicator. Conventional applicators have limitations in terms of the number of radiation tubes that can be inserted, positioning of the tubes, applicator misfit, and pain when inserted. A well-fitted applicator is needed to improve the orientation of the radiation source toward the target area and to reduce the amount of scatter radiation and tissue irritation. Using an appropriate dental material to make an impression can serve to achieve these aims. This article describes a technique for fabricating an acrylic resin custom-made applicator by using techniques used in dentistry.