CAD/CAM technologies today is the work foundation: orthopedists and orthodontists. Direct digital scanning of imprints or mouth cavity allows the creation of an exact jaw model, manufacture individual abutment, save time and expenses. However, in many clinics specialists are used to make silicone imprints and working models of gypsum.
Why is that so? Probably, dentists think 3D printing to be inexact and unprofitable. What is really better for the dental implantation and prosthetics: gypsum models or 3D printing with the digital imprint?
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| Fig. 1 – Gypsum jaw model | Fig. 2 – Jaw model, printed with the 3D printer based on the digital intraoral imprint |
Comparison of 3D printing and gypsum when creating a jaw model
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3D printing based on the direct digital imprint |
Gypsum model based on the silicone, gypsum or combined imprint |
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1. Getting the image in the real time, i.e. all the defects are detected either on the spot or after the analysis of the acquired data (Fig. 4). |
1. Disadvantages of a gypsum model can be noticed only after its casting, that is why the procedure often must be conducted several times. |
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2. Simplicity of the procedure. |
2. Blood leakages, retraction thread can disturb the imprint material; other factors can also lead to the repetition of the procedure. |
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3. When scanning abutments and mucosa, there is no risk of transfer overturning.
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3. High probability of moving transfers with the silicone imprint. |
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| Fig. 3. Combining CT and intraoral digital imprint in a computer program | Fig. 4 – Digital imprint allows the detailed analysis of the margin |
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4. Quickness of getting a real model due to the fast scanning even with the necessity of repetition of the procedure because of the low image quality. |
4. Additional procedures delay the creation of the model and require material expenses. |
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5. Possibility to get a range of sequential images of separate segments. |
5. Tongue and ramus bone impede of getting an exact imprint of the distal area. |
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6. Possibility to scan only individual segments on the long areas. |
6. Possibility to get an imprint of the whole jaw. |
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| Fig. 5. The process of getting dental technique model: intraoral scanning, digital imprint and 3D printing |
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7. Digital storing of patient’s data, quick renewal of the model when needed. |
7. Gypsum model can be easily broken. |
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8. With a computer program it is easily possible to plan a sequential set of orthodontic constructions for treating with a high exactness of their slope angle and size. |
8. It is quite hard to fixate the blocks of a gypsum model under a right angle for the further manufacturing of an orthopedic construction, what can cause sensation of pain. |
Advantages of the digital imprint for creating a model
The main difference of the digital imprint if the high exactness and quickness of the working with a clinical case.
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| Fig. 6. Silicone imprint | Fig. 7. Digital imprint of the patient’s mouth cavity |
Digital imprints are created with the help of the equipment for optical or laser scanning. It allows to send the model for printing via mail and save time for the preparative stage. In comparison with gypsum models, this technology is more exact and quicker.
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| Fig. 8. Dental technical model based on the digital lab scan | Fig. 9. 3D printing based on the digital mouth cavity scan |
However, digital imprint also has its disadvantages:
Getting a digital imprint is impossible when making a full removable prosthetics. Because of the full or almost full adentia, mucosa on the mandible becomes loose and mobile, go it is difficult to get an imprint with the help of digital scanner. In this case, it is more reasonably to use the technique of silicone imprint: press and get the imprint.
It is also difficult to make a digital imprint, if the ledge of the tooth is lower than the gingival margin to solve the clinical case. Retraction thread must be used to lower the gingiva to the ledge and make a scan.
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| Fig. 10. Use of retraction thread before intraoral scanning (tooth ledge is lower than the gingival margin). |
Once more about CAD/CAM systems
Developing the method of CT has made an input to the automation of projecting and planning the medical practice or CAD (Computer-Aided Design). Also, it contributed to the automation manufacture system with the help of computer or CAM (Computer-Aided Manufacturing).
In general, CAD/CAM are used in medicine and dentistry for creating:
- 3D models and diagnosing and planning operations;
- virtual surgical intervention for forecasting the consequents;
- creating exact virtual models of dento-facial and dental implants etc.;
- creating models of restorations and implants (with the help of CAD/CAM cutting or 3D printing).
For example, a model on the photo below was printed with this technology. It can be used several times for a log-time period, as 3D printing is characterized by higher firmness.
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| Fig. 11, 12. Working jaw model, printed with the help of 3D printer (photo: can-touch) | Fig. 11, 12. Working jaw model, printed with the help of 3D printer (photo: can-touch) |
Digital imprint – foundation of CAD/CAM
Digital optical scanning is a leading technology, with the help of which we get the whole computer model of patient’s mouth cavity. Its advantage is the combination of hard and soft tissues in the virtual space, what is impossible when using CT without an intraoral scanner.
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| Fig. 13. A model, printed on the base of digital lab scan without gingival mucosa | Fig. 14. A model, printed on the base of digital lab scan with the gingival mucosa |
Digital imprint allows not only predicting the implantation, but also creating the right individual abutment for a patient with the help of CAD/CAM technologies.
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| Fig. 15. Digital imprint of the mouth cavity | Fig. 16. Digital scanning of the lab model |
The process of manufacturing an individual abutment is conducted in the following way:
- Intraoral scanning without gingival former.
- Checking the scan of the abutment and placing it on the implant in the mouth cavity or in the working model.
- Scanning the scan-abutment.
- Creating the virtual dental-technique model.
- Designing the future abutment in the computer program.
- Printing 3D working model.
- Manufacturing an individual abutment with the help of cutting. Pre-milled abutments and titanic platforms are used.
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| Fig. 17. Pre-mill abutments FreeForm | Fig. 18. Titanic platforms for CAD/CAM |
With this technology, we can create an abutment with a screw-retained or cement-retained fixation. Using a digital imprint, 3D-printed model and scan-abutments let us reach the perfect outcomes of restorations.
Conclusion
Yes, many specialists discuss the effectiveness of using the digital imprint and 3D-printed models in the dental practice because of the high costs. However, taking into account its obvious advantages such as momentary getting of the working model within the one procedure, high exactness and simplified work of the dental technician, one could argue with it. Digital imprint and 3D models with the use of scan-abutments give better outcomes in the dental implantation, where the exactness of a prognosis determines sometimes not only aesthetical, but also clinical problems of the patient.