The conventional complete denture fabrication process involves several steps that require the clinician to communicate specific instructions to the laboratory via prescription slips.
Here is an outline of what the clinician should write on the laboratory prescription slip following the necessary clinical procedures:
Laboratory Prescriptions for Complete Denture Fabrication
1. Prescription Following Primary Impressions (Visit 1)
(Laboratory task: Diagnostic casts & special trays)
The clinician provides the primary impressions to the laboratory. The prescription outlines the requirement for diagnostic casts and, crucially, the fabrication of custom/special trays.
The clinician should provide details that determine the design of the custom tray, which involves marking the necessary anatomical boundaries and relief areas on the anatomical models:
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Request: Fabrication of diagnostic casts (maxillary and mandibular) and custom/special trays.
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Design Outline: Produce the tray outline to full extension.
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Border Requirements: Specify the cut-back requirements. The border extensions should be designed to be 1 mm short of the vestibule when tissues are at rest and 1 mm short of the frenula when they are active.
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Relief Areas: Identify areas on the cast that require wax relief. Examples include blocking out undercuts on the labial of the alveolar ridge, or outlining wax relief for the incisive papilla and central palate.
2. Prescription Following Secondary Impressions (Visit 2)
(Laboratory task: Bead & box, master casts, base & rims)
The clinician provides the secondary (functional) impressions to the laboratory. The prescription details the creation of master casts, baseplates, and occlusal rims.
The primary instructions concern the dimensions and construction of the occlusal rims:
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Request: Pouring of master casts (using bead and box method) and fabrication of baseplates and wax occlusal rims.
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Undercut Management: Instruct the lab to block out undercuts on the master casts (if needed).
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Maxillary Rim Specifications:
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Width: 8 mm anteriorly, 10 mm posteriorly.
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Position: 2/3 of the width Buccal and Labial to the survey line on the cast.
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Height: 15 mm high anteriorly, tapering to 13 mm posteriorly.
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Mandibular Rim Specifications:
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Width: 8 mm anteriorly, 10 mm posteriorly.
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Position: Buccal width should equal lingual width.
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Height: 14 mm high anteriorly and parallel to the crest of the residual ridge.
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3. Prescription Following Maxillo-Mandibular Relations (MMR) Appointment (Visit 3)
(Laboratory task: Articulation & tooth setting)
After contouring the rims, determining the Occlusal Vertical Dimension (OVD), and recording the Maxillo-Mandibular Relations (MMR), the clinician must transmit all functional and aesthetic parameters to the laboratory for articulation and tooth setting.
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Request: Mounting of casts onto the articulator and setting of artificial teeth (for wax try-in).
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Jaw Relation Records: Specify the MMR (Centric Relation) record achieved and provide the facebow record.
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Articulator Settings (if required): Note the settings to be used for condylar guidance (e.g., 25°) and Bennett angle (e.g., 0°) if applicable to the articulator type.
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Aesthetic & Positional Guidance: Provide the following markings recorded on the maxillary rim:
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Midline.
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Smile line.
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Canine line (inter-canine width).
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Tooth Selection:
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Shade: Specify the selected shade (e.g., from IPN Shade Guide).
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Mould (Form & Size): Specify the selected mould numbers for the upper and lower anterior and posterior teeth. (E.g., Anterior: 21E Square Tapering, Posterior: 33° or 10° cuspal inclination).
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Anterior Overlap: Instruct the lab regarding the required vertical overlap (overbite) and horizontal overlap (overjet) to ensure appropriate aesthetics, phonetics, and function.
4. Prescription Following Wax Try-in (Visit 4)
(Laboratory task: Finalisation & processing)
After the clinician performs the clinical check (covering occlusion, aesthetics, phonetics, etc.) and gains patient acceptance, the final step is authorizing the laboratory to process the dentures.
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Request: Finalisation, processing, polymerization, and finishing of the complete dentures.
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Confirmation: Confirm that the wax try-in was satisfactory (or list any minor changes approved during the try-in).
Note: The treatment schedule lists an initial step for the laboratory after Visit 1 to produce “Diagnostic casts & special trays”. However, the detailed instructions for formulating a lab prescription regarding design outline, cut-back, and relief are specifically described in the source material related to designing the special tray for the secondary impression stage.