Chris Brown, Business Manager, Apex Dental Milling

Model scanners, CAD software and milling equipment were once only found in the largest laboratories and milling centers. However, today they can be found in even one- to two-person laboratories. There is little doubt that technology is allowing laboratories to become more efficient, more productive and have more control and consistency in their work.

Traditional technician workstations with waxing tools, brushes or handpieces are being replaced with 

 on desks with high speed microprocessors, 24” monitors, and a 3D CAD mouse.

Interestingly, even with all of the recent technology advances, the model room is one area that hasn’t yet been significantly impacted by the digital workflow. 

 systems are definitely more common today than 5 years ago, but model rooms are not shutting down.

The $25-30 cost of milled or printed models from the digital impression manufacturer is a tough pill to swallow for laboratories that are used to poured models costing $10-15 once materials and labor costs are added up.

Even more change is on the horizon. Laboratory model scanners with impression scanning options are now available. These scanners and a number of new digital impression systems coming to the market with limited or non-existent model solutions may provide new motivation to re-evaluate 

Model building software modules are now available from 3Shape and Dental Wings, and 3D printers are within the financial reach of laboratories and milling centers. Model printing from impression scans and digital impressions are becoming a viable option.

Apex Dental Milling provides digital workflow services for dental laboratories. In the following case, a traditional PVS impression has been received, and the laboratory has ordered a stained and glazed full contour zirconia crown. The impression will be scanned using a 

 Identica scanner. The model will be virtually created with 

’s Model Builder Module, and printed in the Stratasys, Ltd.'s Eden 260V printer. The restoration will be designed with ApexCAD design software.

 A quadrant PVS impression is received from the laboratory. The impression is sterilized and prepared for scanning. Excess impression material is trimmed to provide maximum viewing angles for the scanner 

 Grooves are cut into the impression tray to assist in scan alignment 

 Scans are taken of both the maxillary and mandibular arches using the Identica Scanner. Alignment of one arch scan to the other is done by placing reference dots on each arch 

 and using the scanning software tool to ‘snap’ the arches together 

 Excess material is trimmed away from the scans. The area in red will be removed 

. Total scan and edit time is approximately 10 minutes.

 The completed and saved impression scan provides crisp and accurate detail 

 The impression scan is then imported into 

 Model Builder to virtually fabricate the model. The first step is to set the insertion path/plane of occlusion. 

 The model parameters are adjustable. Typically model height is reduced to keep production costs and times low 

 Dies can be made removable. For this particular case, because the restoration is full contour zirconia, margin trimming usually isn’t necessary. Instead of printing a working model, a solid model will be printed 

 Model arches are loaded into the Objet Studio CAM software program for printing with other models 

. Print time is function of number of models to be printed, and the height of those models.

With the other models in the project, print time in the Eden 260V was approximately 2 hours and 15 minutes. Printing can be done during regular business hours or overnight.

 Once the print job is complete, the models can be removed from the printer (Fig. K). The Eden 260V printer has two print finish options; Matte and Glossy. We’ve found the matte to provide the most consistent dimensional results. However, the matte finish leaves ‘support’ material around the entire model that has to be removed. Figure L shows the models with the support material still intact.

 High pressure water spray is used to remove the support material from the printed model. The process takes approximately 15-30 seconds to do per model (Fig. M).

 While the model is printing, the case is imported into CAD software and a 

 After milling, the restoration is stained and glazed using 

. Interproximal and occlusal contacts are checked on the printed model 

Material costs of printed models can range from $3 to $8 depending on the size of the model. The time required to virtually build models is about 3-5 minutes.

If a case is coming from a doctor’s chairside digital impression, only a few seconds are required to import the data. If the case is a scan of a traditional impression, plan on 10-14 minutes for scanning and editing. Most impression scanning programs and model building programs have editing tools to fill in holes. Some will even have advanced editing tools that can add surfaces for bridging holes, fix bad scan data or modifying arch position.

 may never totally shut down. However, with more digital impression systems on the market and in use, with the improved impression scanning systems available, and capable 

 such as the Stratasys, Ltd.'s Eden 260V, we may see a lot less dust in dental laboratories.

Chris Brown, Business Manager, Apex Dental Milling

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