Dental Lab Sops

SOP: Dental Prosthetic Fabrication & Quality Assurance

Document ID: TR-DENT-FAB-001
Effective Date: October 26, 2023
Version: 2.1
Review Cadence: Semi-Annual (Q2/Q4)
Target Audience: Lab Technicians, Quality Control Leads, Clinical Liaison Officers

---

1. Executive Summary & Scope

This SOP establishes the mandatory operational framework for the fabrication of custom dental prosthetics (crowns, bridges, and abutments) at Template Registry. This protocol ensures compliance with ISO 13485:2016 standards and FDA 21 CFR Part 820. All personnel are bound by these procedures to maintain mechanical integrity, marginal adaptation, and biological compatibility of all outgoing medical devices.

---

2. Prerequisites & Tool Requirements

• Equipment: Calibrated CAD/CAM milling unit (5-axis), sintering furnace (certified per batch), digital intraoral scanner interface, steam cleaner, ultrasonic bath.
• Software: Open-system design suite (exocad/3Shape) with validated libraries.
• Safety PPE: N95 particulate respirator (during milling/grinding), ANSI Z87.1-rated safety goggles, nitrile exam gloves, lab coat.
• Certifications: Active CQC/CDT credentialing for lead technicians.

---

3. Roles & Responsibilities (RACI Matrix)

---

4. Step-by-Step Operational Procedure

Phase 1: Intake & Digital Verification

• Verify digital prescription (Rx) completeness (Material, Shade, Margin depth).
• Confirm file integrity (STL/PLY mesh closure and non-manifold edge check).
• Cross-reference digital model with physical impressions (if applicable).

Phase 2: Design & CAD Engineering

• Apply margin line refinement (max deviation 10 microns).
• Verify occlusion clearance (minimum 1.5mm functional cusp).
• Execute virtual articulation to confirm excursive movement paths.

Phase 3: Fabrication & Post-Processing

• Initialize milling cycle; confirm tool life counter status.
• Execute sintering cycle according to material-specific thermal profile.
• Perform manual finishing: verify marginal fit on stone master cast.
• Implement ultrasonic cleaning (5-minute cycle) to remove processing debris.

---

5. Quality Assurance & Verification Criteria

• Marginal Gap Tolerance: Maximum 40μm; exceedance results in immediate scrap.
• Surface Texture: Ra < 0.2μm post-polishing.
• Shade Accuracy: Visual verification under D65 daylight-equivalent lighting vs. VITA Classical shade guide.
• Documentation: Digital sign-off in the Batch Production Record (BPR) required for all steps.

---

6. Practical Troubleshooting Scenarios

Scenario A: Marginal Incongruity post-milling

• Cause: STL file corruption or coordinate system shift during export.
• Correction: Recalibrate machine home-position; re-import raw scan data; check mesh integrity; do not attempt manual adjustment to bridge the gap.

Scenario B: Sintering Oven Error (Thermal Spike)

• Cause: Sensor drift or thermocouple degradation.
• Correction: Halt production immediately. Quarantine the entire sintering batch. Perform a dry-run calibration verification; if temperature variance exceeds +/- 5°C, log maintenance event and replace sensor before clearing quarantine.

Scenario C: Material Delamination/Fracture

• Cause: Incorrect milling feed rate or ceramic pre-heating failure.
• Correction: Verify tool wear; adjust feed speed in CAM software; check material certificate of conformity (CoC). Retrain operator on material-specific nesting depth.

---

Julian Vance
Chief Operations Architect, Template Registry
Approved for internal deployment.