Mold Fabrication Techniques and Materials

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Questions and Answers

What is the purpose of applying foil substitute in the mold fabrication process?

The foil substitute is applied to prevent contamination of the platinum catalyst of the silicone prosthesis material.

Describe the indexing method used during the mold fabrication process.

The indexing method involves placing horizontal and vertical pyramids on the ocular segment's surface to maintain its orientation when positioned back into the mold.

What materials are used to duplicate the ocular segment after its removal from the wax pattern?

The ocular segment is duplicated using alginate impression and then poured in dental stone.

What are the main characteristics of the prosthesis that may not be accurately reproduced?

The contours of the prosthesis and the skin texture may not exactly duplicate the contralateral structures. Signup and view all the answers

Name two techniques practiced for coloration of the prosthesis material.

Micro air-spray techniques and brush-in technique are two methods used for coloring the prosthesis. Signup and view all the answers

What is the purpose of using cotton balls tied with dental floss during the moulage impression process?

Cotton balls are used to plug the nostrils to prevent distortion while allowing the patient to breathe comfortably through an evacuator tube. Signup and view all the answers

What is the recommended water/powder ratio for mixing alginate in the moulage impression process?

The recommended water/powder ratio is 1.25 to 1.50 times the normal amount of water. Signup and view all the answers

What steps are taken to ensure the alginate impression does not trap air?

Alginate is applied to the skin surface with a round-end mixing spatula, taking care to avoid air entrapment. Signup and view all the answers

Why is a rigid plaster backing applied over the alginate impression?

A rigid plaster backing is applied to ensure the removal of the impression without distortion. Signup and view all the answers

What is checked with a blunt instrument to assess the setting of the plaster used in the impression process?

The surface of the plaster is checked for tapping sound to determine if it has set properly. Signup and view all the answers

What should a patient do to assist in the removal of the impression from their face?

The patient should wiggle or produce wrinkles on their face to help free the impression from the skin. Signup and view all the answers

What condition may a patient exhibit during the impression process due to heat and moisture, and how quickly does it return to normal?

The patient may appear flushed, but their skin color and temperature will rapidly return to normal afterward. Signup and view all the answers

What steps are taken if small defects or voids are found in the impression after inspection?

Small defects or voids not associated with the margin area may be filled in or chipped off the cast. Signup and view all the answers

What is the role of impression materials in the fabrication of an orbital prosthesis?

Impression materials are essential for obtaining facial moulage, which ensures a well-fitting and well-fabricated prosthesis. Signup and view all the answers

Name two reversible impression materials used for obtaining facial moulage.

Reversible hydrocolloid and impression compound are two reversible impression materials. Signup and view all the answers

What is one advantage of using modelling clay in the fabrication of an orbital prosthesis?

Modelling clay is water-based and can be shaped easily; once dried, it becomes a hard, stone-like substance. Signup and view all the answers

Describe the importance of patient preparation before taking impressions for an orbital prosthesis.

Patient preparation ensures that the face is free from distractions like makeup and glasses, which aids in achieving accurate impressions. Signup and view all the answers

What materials are commonly used for modeling in the fabrication of an orbital prosthesis?

Common materials include sculptor’s clay, plaster, and waxes. Signup and view all the answers

What is the significance of using silicone elastomer in the prosthetic material for orbital defects?

Silicone elastomer is flexible and can mimic the texture and movement of natural tissues, contributing to a more lifelike prosthesis. Signup and view all the answers

Identify one step in the prosthetic procedure for orbital defects.

One step is the careful alteration at surgery to optimize the prosthetic prognosis. Signup and view all the answers

What is the potential impact of exenteration on future prosthetic rehabilitation?

Exenteration, involving the removal of the eye and surrounding structures, significantly complicates prosthetic rehabilitation due to the absence of supporting tissues. Signup and view all the answers

Study Notes

Prosthetic Dental Sciences Department (Removable Prosthodontics Division)

Mission: Develop and graduate competent dental professionals for community service and scientific research, fostering education and knowledge dissemination in oral health.
Vision: Be a pioneering dental college nationally and internationally in dental education and scientific research.
Extra-oral maxillofacial prosthesis fabrication techniques - Orbital Defects: This division focuses on techniques related to extra-oral prostheses for orbital defects.

Introduction: Discusses maxillofacial prostheses that restore the eye, eyelids, and surrounding hard and soft tissues. The specific mention of GPT 9 suggests a particular type or version of this prosthetic approach. Orbital prostheses are among the most challenging facial prostheses to construct due to the inherent mobility of the eye and the static nature of a prosthesis.
Unfavorable Orbital Defects: Different scenarios of orbital defects and their impact on prosthetic fabrication possibilities. Specific concerns include eyebrow positioning, lid retention, and the space available (or lack thereof) for a prosthesis.
Steps in the Fabrication of Orbital Prosthesis: Details a series of steps involved in creating orbital prostheses; including impression procedures, fabrication of molds, and creation of the prosthesis pattern. Material choices for the overall process, including wax choices and specific materials for the finished mold and prosthesis are also mentioned.
Digital Impression: A device used for phase measuring profilometry (3D photography) in acquiring accurate three-dimensional images for creating detailed digital models of an individual's orbital defect. It's described as being fast, safe, and suitable for use with the patient's eyes open. Despite its accuracy, digital impressions are sometimes not suitable for extensive undercuts.
Fabrication of Orbital Prosthesis: Describes materials used in creating facial restorations including impression compounds, reversible and irreversible hydrocolloids, plaster of Paris, and room-temperature vulcanizing materials.
Modelling Materials: Specific materials like modeling clay (a water-based clay that hardens), plaster, and a variety of waxes are discussed.
Material for Prosthesis: These materials are used in creating the actual prosthesis--including differing types of methyl methacrylate, polyurethane elastomers, silicone elastomers, and urethane-backed medical-grade silicone.
Extraoral Impression: Procedures for patient preparation including positioning, draping, and preventing interference with makeup and eyeglasses are detailed. Important pre-impression precautions such as lash and eyebrow protection and blocking of undercuts with gauze or cotton are also discussed.
Points to be remembered: The importance of meticulous attention to detail, specifically regarding packing an area of orbital defect and the nasal or oral cavity communication closure in the region, is highlighted.
Sculpture and Formation of the Prosthesis Pattern (wax): Wax is preferred over clay to avoid mold contamination. The wax formula, including baseplate wax and various coloring agents, is described.
Positioning the Prosthetic Eye: Different methods, and anatomical reference points are needed to ensure the correct positioning. Instruments, like vernier calipers and pupillometers, are used.
Steps of Fabrication of the Mold: Detailed steps for making the mold from stone, the material used for the final prosthesis, and ensuring it doesn't contaminate the catalyst found in the silicone.
Processing of the Prosthesis Material: Strategies to match the color of the prosthesis to the patient's complexion and techniques for color application, such as micro-air spray and brush-in techniques are discussed.
Insertion of Eye Lashes: Natural human hair are curved and processed, and trimmed according to specific lengths for natural aesthetic appearance.
Maintenance of the Prosthesis: Routine care is crucial-- including daily cleaning using a mild soap and removing adhesive on the prosthesis.
Instructions to the Patient: Importance of proper visual adaptation and maintaining hygiene of the area, the location of the prosthesis, and application techniques is stressed.
Implant Supported Prosthesis: This option may not be suitable for all patients due to the presence of specific tissues such as cartilaginous peripheral tissue or thick skin layers. Additionally, the orbital rim and superior maxilla location may not be possible implant sites.
Retention of the Prosthesis: Different retention mechanisms are covered. Anatomic retention involves using the patient's tissues; mechanical retention, using specific attachments and attachments such as magnets and clips are discussed.
Conclusion: The general goal of prosthetic treatment is to restore the patient to society with a natural appearance. Advances in prosthetic treatment and ophthalmic or eye-related surgery have greatly impacted the successful rehabilitation of these patients.
Attachments used in Facial Prostheses: This section details commonly employed methods and materials to affix prostheses. Methods include clips, magnets, and other accessories.
References: Citations to various clinical dental and prosthetic medicine texts for further study are listed.

Additional Information

Digital impression: Use of computer imaging (Adobe Photoshop) techniques for accurate ocular positioning and lid opening
Impressions: Impression procedures and associated materials (alginate and various other materials) to create accurate models needed to construct the actual prosthesis
Fabrication of Mold: Detailed steps for making molds from a variety of materials

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Description

This quiz explores key aspects of mold fabrication processes, including the use of foil substitutes and alginate impressions. It covers various materials, techniques for coloration, and important characteristics of prostheses. Test your knowledge on the methods and tools essential for successful mold fabrication.