Assessing an Offshore Dental Laboratory's Impression Tray and Restoration Type

Objective: The dental practitioner selects impression trays based on a variety of patient conditions.  Certain published guidelines recommend that dual-arch trays should be used for single crowns bounded anteriorly and posteriorly by teeth and with full opposing occlusion. This investigation surveyed impressions used to fabricate indirect fixed dental restorations. Method: Digital photographs of 3403 impression trays used in the fabrication of fixed indirect dental prostheses from an offshore commercial dental laboratory located in China were inspected for tray type and restoration(s) fabricated. The pictures were acquired over a 2-week period. Images were made with a high-resolution digital camera at 3072x2304 pixels.  The laboratory serves other dental laboratories and dentists in the USA, Europe, and Asia. There were no selection or rejection criteria; all impression images received were examined. Result: 3195 trays were plastic; No custom trays were noted. Of the trays examined, full single-arch trays accounted for 6.7%, 5.4% were partial single-arch trays, 87.9% were dual-arch trays. Among all trays counted, 64.9% were posterior plastic dual-arch trays. Among all dual-arch trays 1538 (51.4%) were judged as used according to proper guidelines. 192 anterior and full dual-arch trays were used to construct multiple anterior restorations in the absence of an anterior guide table. With respect to restoration type, 2512 impressions were used for tooth-supported single crowns, 36 for implant-supported restorations and 8 for veneers. 53 impressions were used to fabricate indirect posts, inlays, or onlays. All impression materials consisted of either polyvinyl siloxane or polyether. Conclusion: Within the limitations of this study, dual-arch impressions were the most commonly used tray. While no assessment of the quality of any of restorations was made, manufacturer recommendations were not followed in a substantial number of impressions.