Fit of complete-arch implant-supported prostheses produced from an intraoral scan by using an auxiliary device and from an elastomeric impression: A pilot clinical trial.

STATEMENT OF PROBLEM: The accuracy of impressions for implant-supported prostheses is essential to ensure a passive fit of the definitive prosthesis. Intraoral scanners (IOSs) have been developed as an alternative to complete-arch implant-supported restorations; however, whether they are sufficiently accurate when more than 3 nonaligned implants are involved is unclear. PURPOSE: The purpose of this pilot clinical study was to determine whether the fit of complete-arch zirconia implant-supported frameworks processed on a cast obtained with an IOS and adjusted with an auxiliary device is equivalent to a prosthesis obtained from an elastomeric impression. MATERIAL AND METHODS: Twelve consecutive participants who were ready for complete-arch restorations on already osseointegrated implants were enrolled. Two records were made, one open-tray with polyether and splinted impression copings and the second with an IOS. A verification gypsum device was used for the elastomeric impression, and a prefabricated auxiliary device was used to adjust the intraoral scans. Two zirconia frameworks with the same design were processed and evaluated intraorally by 2 independent calibrated observers. RESULTS: In 11 of the 12 participants, the digitally processed prosthesis was preferred over the conventionally processed prosthesis. The clinical fit of the prostheses obtained with the completely digital workflow was better than that of those obtained with the conventional workflow. CONCLUSIONS: The use of a prefabricated auxiliary device after intraoral scanning allowed delivery of complete-arch implant-supported monolithic zirconia prostheses with a fit better than those fabricated from conventional impressions.

In vitro comparison of the accuracy of four intraoral scanners and three conventional impression methods for two neighboring implants.

PURPOSE: To determine whether the accuracy of two-implant model impressions taken with optical scanners was inferior to that of those taken with elastomeric materials. MATERIALS AND METHODS: Impressions of a resin reference model with two almost parallel implants were taken using three elastomeric impressions (closed tray technique, open tray nonsplinted technique and open tray splinted technique) and scanned with four optical scanners (CEREC Omnicam, 3M True Definition Scanner, 3Shape TRIOS3 and Carestream CS 3600). STL files of the different methods were superimposed and analyzed with control software (Geomagic Control X, 3D systems) to determine the mean deviation between scans. RESULTS: Compared to elastomeric impressions, optical impressions showed a significantly improved mean precision. TRIOS3 and CS3600 showed a significantly improved mean trueness compared to that of closed tray, CEREC Omnicam and TrueDefinition. All methods showed a certain degree of implant rotation over their axes, which was significantly higher in the closed tray and the open tray nonsplinted techniques. CONCLUSIONS: Optical impressions, taken under these in vitro conditions, showed improved accuracy compared with that of elastomeric impressions.

Impact of design and length on the accuracy of closed tray transfer copings.

BACKGROUND: The aim of this study was to evaluate the accuracy of two closed-tray transfer copings for implant impressions (a new design vs. an old design) in two different lengths (short and long). MATERIAL AND METHODS: Four groups of transfer copings (NS - new short, NL - new long, OS - old short and OL - old long) were tested. An epoxy resin model was prepared of missing teeth 1.4, 1.5 and 1.6. Two Alpha-Bio analogues were placed in position of teeth 1.4 and 1.6, at a 10o angulation. Two calibrated operators took 10 closed-tray impressions for each group with polyether in a Rim-Lock impression tray. RESULTS: After measuring and comparing impressions, a significant difference was found between the two new transfer copings and the old short transfer coping. CONCLUSIONS: The new transfer coping design significantly improved impression accuracy. An adequate transfer coping design for the closed-tray impression technique can help to achieve clinically acceptable impressions for two-unit implant supported bridges. Key words:Closed tray, impression coping, transfer coping, implant impression.