October 2016
Volume 7, Issue 10

What to Choose: Conventional Methods or CAD/CAM

Comparing the advantages and disadvantages of physical models versus digital design

By Cristian Ioan Petri, CDT

Times have changed and most laboratories use technology every day. Many procedures that were previously performed by conventional methods now utilize CAD/CAM. At the same time, some materials that were used for those conventional methods still can be used with newer technology.

Whether a laboratory fabricates its own frameworks in-house, sends an STL file to a milling center, or sends models to a milling center, it is important that the 3D design of the framework meets the necessary standards. Regardless of who handles the digital design, the 3D reality on the screen is slightly different compared with the physical reality.

This article demonstrates how classical methods and CAD/CAM technology can be utilized to obtain a high-quality finished product, and it presents a parallel between the two procedures, with advantages and disadvantages.

The first important step is to transfer the implant position from the mouth to the model and to create a perfect model using Primotec’s Primopoly (Figure 1 and Figure 2). To preview the final work and interact with the patient, the author created a diagnostic waxup according to the patient’s wishes (Figure 3). After fulfilling all the requirements for the waxup, the author moved on to making the prototype. As previously mentioned, the prototype can be fabricated conventionally or via 3D design.

Conventional

First, a flask was used and the technician duplicated the waxup using a transparent silicone (Figure 4). After removal of the waxup, Primotec’s Primopattern resin was injected, followed by light polymerization. This allowed the technician to obtain a perfect copy of the waxup. Using burs and a micro-motor, the technician started to grind the setup, guided by the silicone index, as necessary (Figure 5). This produced the prototype. Primopattern flowable gel was used for necessary adjustments and additions (Figure 6). Using the silicone index, the technician checked the available space for the esthetic parts, which would be individual crowns (Figure 7 and Figure 8).

At that point, the model and prototype were sent to the milling center, where they could recreate it with the necessary materials (Figure 9). Laboratories that have scanners can send an STL file instead of a model.

Advantages: The technician can be sure that the final result is what is needed. It is also cost-efficient.

Disadvantages: The process is time-consuming, so labor costs must be considered versus the potential investment in a CAD/CAM system.

CAD/CAM

With a diagnostic waxup, the laboratory has a guide for all phases of the CAD/CAM process, which is very important for the scanning and 3D modeling protocol. The first step was to prepare the CAD command file, with which all types of prosthetic work can be done. At this stage, each type of prosthetic work has specific parameters set in the system, but they can be modified as necessary in both the file and design phases.

The milled work’s precision depends equally on the milling machine and the scanner. If the scan is imprecise, the milling result will be the same, as the machine will execute the given parameters, and it is unable to check or compare.

The 3D model was obtained by overlapping the 2-dimensional pictures and choosing commonalities, image-transforming algorithms in 3D, calibration devices, and the way in which the information and the advanced thermal compensation structural algorithms would be processed to build this “puzzle” (Figure 10).

Once the 3D model and setup were ready, digital tools were utilized to create the prototype of the final framework. Adding, cutting, and making other changes is easy using all the solutions that are available in CAD software (Figure 11). The technician was then able to virtually check the available space for esthetic aspects. The digital frame was prepared and milled out of a red Primopattern disc by Primotec (Figure 12).

Advantages: This process is very efficient. It is easy to change the digital framework. The process is fast and predictable. It is also easy to mill the prototype from different materials without repeating each step.

Disadvantages: The technician needs to master a new technique, and major monetary investments are necessary.

Conclusion

Technology and new materials have revolutionized the way we provide health care services and develop our businesses, as well as the way we make prosthetic restorations. In dental laboratories that utilize CAD/CAM technology, 90% of fixed prosthetic restorations are now made digitally, with only the esthetic aspects being handled via classical methods in many cases. Indeed, the touch of an experienced technician is decisive when using CAD/CAM, but not for 100% of cases. The time required for fixed restorations when combining different types of materials using classical methods is significant, thus increasing production time and cost. Even though technology and new materials require major investments, significantly less time is needed to make prosthetic restorations with CAD/CAM, and they are more precise and consistent. The most important factor is the time savings, from which everyone benefits: the patient, physician, and technician.

Cristian Ioan Petri, CDT, owns ARTCHRYS Laboratory in Cluj-Napoca, Romania, specializing in complex rehabilitations, esthetics, and function.

Disclaimer: The statements and opinions contained in the preceding material are not of the editors, publisher, or the Editorial Board of Inside Dental Technology.

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