Surveying in Prosthodontics

Surveying in Prosthodontics

• Surveying is an important part of Removable Partial Denture (RPD) fabrication, analyzing dental casts to determine how best to insert and remove the prosthesis
• This process uses a dental surveyor to identify undercuts on teeth for retention, and areas needing modification
• Surveying helps plan the design and placement of clasps and other components

Path of Insertion

• A surveyor establishes a consistent path for inserting and removing the denture, crucial for retention and stability
• Surveying helps to identify undercuts on teeth that can be used for clasp retention
• Creates parallel surfaces on teeth which guide the prosthesis during insertion and removal

Surveying Tools

• Analyzing Rod: Used to assess undercuts and evaluate parallelism
• Carbon Marker: Marks survey lines on teeth to identify retention areas
• Undercut Gauge: Measures the depth and location of undercuts for clasp design
• Wax Trimmer: Used to trim excess wax and prevent overcontouring of the cast

Tilting the Cast

• Tilting the cast is essential during surveying to find the most advantageous path of insertion and optimize undercuts for retention
• Tilting the cast ensures the denture can be inserted and removed smoothly, increases desirable undercuts, minimizes undesirable ones and helps to conceal metal components
• There are three types of tilt: Anterior, Posterior and Lateral

Steps for Tilting the Cast

• Start by tilting the cast horizontally, where the occlusal surfaces of teeth parallel to the horizontal plane
• Analyze the proximal surfaces of abutment teeth to determine if any adjustments are needed to achieve parallelism between guiding planes
• Anterior Tilt: Tilting the cast forward increases mesial undercuts
• Posterior Tilt: Lowering the posterior region of the cast increases distal undercuts and decreases mesial ones
• Lateral Tilt: Adjust laterally to equalize undercuts on both sides of the arch, ensuring uniform retention across the arch.
• Identify hard or soft tissue interferences such as palatal tori or exostoses, as they may hinder the path of insertion
• Use the analyzing rod to confirm the desired path of insertion and retention areas are achieved with each tilt adjustment
• Mark survey lines using a carbon marker to delineate undercut areas
• Preserve the tilt using tripoding, which is a technique where three points are marked on the cast, allowing for precise repositioning in future surveys

Blockout in Surveying

• Parallel Blockout: Ensures guiding planes are parallel
• Shaped/Ledge Blockout: Creates ledges for clasp arms
• Arbitrary Blockout: Covers non-essential areas to prevent interference

Application of Surveying in RPD Design

• Clasp Design: Surveying informs the design and placement of clasps by identifying suitable undercut areas for retention
• Framework Design: Ensures all components of the RPD framework are properly aligned with oral structures
• Mouth Preparations: Guides necessary tooth modifications to create optimal guide planes and ensure proper fit

Tripoding

• Tripoding is a technique used to ensure that the cast can be repositioned in the same orientation on the surveyor after removal
• Three points are marked on the cast, typically in stable areas that are not susceptible to change or wear
• The marked points act as a reference for precise repositioning

Benefits of Surveying

• Enhances the precision of RPD design, providing a clear reference for component placement.
• Streamlines the design process by providing guidelines for framework construction.
• Allows for personalized prosthesis design tailored to individual anatomical variations.