Prosthetics Base Plates Construction

Base Plates

• Base plates are temporary acrylic structures representing the foundation for future prostheses.
• Key features: rigid, stable, easy to cut and polish, must extend and settle correctly on the model.
• Constructed from self-curing acrylic resin, with a rigid tray and a secure handle that doesn't interfere with the tongue or lips.

Construction Steps

• Design the individual tray extension on the model using a pencil, extending to the vestibular depth and retromolar papilla.
• Lubricate the model's surface with petroleum jelly.
• Mix immediate acrylic for the tray following the manufacturer's powder-liquid ratio.
• Once the resin reaches a paste-like consistency, fashion the upper tray: lightly coat fingers and rolling pin with petroleum jelly, shape the resin into a flattened ball, and apply it to the model.
• Adapt the material gently to avoid thinning it, trimming excess with a sharp knife. Allow for initial polymerization by quickly smoothing the surface with fingertip pressure.

Lower Tray Construction

• Follow similar procedures as the upper tray but form the resin into a "hot dog" shape before molding.

Trimming Base Plates

• Excess material is removed using abrasive bands, followed by refined shaping with acrylic burs.
• Smooth the exterior surface with pumice stone.
• Prevent direct contact between acrylic mixture and gypsum model to avoid polymerization issues and property alteration due to water absorption.

Occlusion Rims

• The occlusion-contour rim is made of wax on the base plate to establish facial support, occlusal plane level, vertical dimension, and arch shape.
• Procedures for the upper maxillary rim include marking incisal edges and establishing midlines and canine positions using precise measuring and tracing techniques on the model.

Maxillary Rim Steps

• Define key anatomical points (papillae, tuberosities) to determine the contour of the rim.
• Adjust height measurements to achieve desired anterior (22 mm) and posterior (20 mm) occlusal heights.
• Gradually shape the rim to ensure proper thickness (5 mm anterior, 8 mm posterior).

Mandibular Rim Procedure

• Establish midline and mark retromolar papillae for defining the posterior occlusal height.
• Create a U-shaped wax cylinder to reshape on the base plate.
• Adjust heights similarly to the maxillary rim, ensuring anterior (18 mm) and posterior heights align with marked projections.
• Maintain gradual thickness control to follow the alveolar contour.

Finalization

• Ensure smooth surfaces are maintained on both vestibular and palatal sides, forming sharp angles with the occlusal surface.
• Clean and polish the wax surface before final use.

This quiz focuses on the construction of base plates used in prosthetics. It explores the key features, materials, and specific construction steps necessary for creating stable and effective base plates. Test your understanding of these essential components in prosthetic development.