Removable Partial Denture Workflow: Removable Prosthodontics Protocol
Initial Diagnostic Phase and Mouth Preparation
The fabrication sequence for cobalt-chromium (Co-Cr) removable partial dentures begins with comprehensive planning on primary casts before performing any irreversible mouth preparation.
Primary Impressions and Study Casts
- Make preliminary impressions of the maxillary and mandibular arches using alginate.
- Pour the impressions to produce diagnostic study casts.
- Request the dental laboratory to fabricate custom (special) trays for the definitive impressions.
Surveying and Framework Design
- Perform surveying on the primary diagnostic casts—not on master models—to establish the path of insertion, identify undercut locations, and determine clasp placement.
- Plan and mark all framework components, including occlusal rest seats and guide planes, prior to preparing the patient’s teeth.
- Execute the required mouth preparations (rest seat preparation, axial contouring, and guide planes) directly on the patient based on the pre-determined survey design.
Definitive Impressions and Master Cast Fabrication
Following mouth preparation, the secondary (definitive) stage captures tooth preparations and edentulous anatomy:
- Obtain definitive impressions using the custom trays and appropriate elastomeric impression material (such as polyvinyl siloxane or polyether).
- Pour the master casts.
- Depending on the occlusal scheme and stability of remaining tooth contacts, decide whether the master casts require mounting prior to framework fabrication.
Articulation Strategy and Maxillomandibular Registration (MMR)
Master cast mounting prior to metal framework fabrication depends on occlusal clearance, arch stability, and saddle configuration.
Definitive Master Casts
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Stable / Well-Supported Unstable / High-Risk
(e.g., Kennedy Class III) - Free-end saddles (Class I/II)
| - Tight dynamic occlusion
Hand-articulate directly - Deep bite / Class II div 2
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Proceed directly to framework Fabricate record base & wax rim
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Record MMR on the patient
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==Mount master models before framework fabrication==
Indications for Mounting Before Framework Fabrication
- Tight Occlusal Clearance: In patients with minimal interocclusal space, unmounted casts force laboratory technicians to wax rest seats blindly. This frequently results in an overcontoured, high rest seat that interferes with maximum intercuspation (MIP).
- Deep Bite / Angle Class II Division 2: In cases where lower incisors occlude directly on the palatal gingival margin or cingula of upper anterior teeth, unmounted fabrication risks placing a thick palatal major connector into direct occlusal contact, inadvertently increasing the vertical dimension of occlusion (VDO).
- Distal Extension / Free-End Saddles (Kennedy Class I and II): Edentulous spaces lacking posterior tooth stops prevent accurate hand articulation and require base rims to establish vertical and horizontal orientation.
Clinical Registration Protocol
- Fabricate a rigid baseplate with a wax occlusal rim on the master model.
- Register the MMR at the correct VDO and MIP directly in the mouth.
- Mount the master models on a simple hinge (Class I) articulator.
- Send the articulated assembly to the laboratory so the technician can wax and cast the framework directly to the opposing clearance.
Lecturer — Articulator Choice
Semi-adjustable articulators with facebow transfers and protrusive records are standard within post-graduate prosthodontic training (DCD), but simple hinge articulation to Maximum Intercuspation (MIP) is routine for standard undergraduate clinics and commercial laboratory workflows due to time and cost constraints.
Digital and Photographic Occlusal Assessment
When mechanical articulation or digital model delivery is unavailable, occlusal clearance can be evaluated using alternative chairside methods:
- Intraoral Scanning: Capture digital scans including buccal bite registrations. Review the digitized models from the palatal and lingual aspects to evaluate clearance at rest seat sites.
- Intraoral Photography and Articulating Media: Dry the teeth and mark the dynamic and static contacts intraorally using articulating paper. Take clear, multi-angle clinical photographs showing the occlusal markings in MIP and lateral excursions. This informs the laboratory technician where clearance is restricted.
Framework Try-in and Teeth Setup
Once the framework is cast, verify its clinical fit before proceeding to the definitive wax try-in:
- Framework Try-In: Insert the bare metal framework intraorally. Check the seating of all rests, minor connectors, and reciprocal arms.
- Fit Assessment Media: Identify binding areas and framework pressure spots using specialized indicator paste (e.g., Fit Checker) or liquid aerosol sprays on the fitting surfaces. Relieve interferences with appropriate metal-finishing burs.
- Subsequent Tooth Arrangement:
- If the master cast was mounted with an accurate MMR prior to casting, send the tried-in framework back to the laboratory for immediate tooth arrangement on the articulated models.
- If the case was not mounted previously (or if posterior saddle stability was uncertain), attach a wax rim directly to the framework saddle mesh, record the MMR at the framework try-in appointment, and mount the framework assembly prior to tooth setting.
- Trial Insertion (Wax Try-in): Assess the trial dentures intraorally for esthetics, occlusal contact distribution, peripheral extension, and stability prior to definitive acrylic processing.