CAD/CAM Technologies: Providing esthetic restorations with ease

By Jonathan L. Ferencz, DDS

Introduction

As CAD/CAM technology continues to be integrated into dental offices and laboratories, the benefits of its use cannot be overstated. Dental CAD/CAM systems and relevant materials allow clinicians to offer a variety of innovative dental services to many of their patients who otherwise may receive less than optimal care, or require multiple and time-consuming appointments. Digitally fabricated models and restorations have been shown to demonstrate greater accuracy when compared to those fabricated using conventional procedures. CAD/CAM technologies help to eliminate human errors that lead to inaccuracies and remakes, as well as alleviate concerns over material costs and manual handling.

With patient acceptance of the treatment plan, CAD technology can be used to design and fabricate both provisional and definitive restorations with great ease. The indirect restorative process becomes even more predictable when advanced materials such as lithium disilicate (IPS e.max, Ivoclar Vivadent) are selected. Comprised of metal-free materials with 70% needlelike crystals by volume in a glassy matrix, lithium disilicate demonstrates exceptional durability and strength, especially when compared to other all-ceramic materials. In addition to these qualities, lithium disilicate also exhibits higher translucency, monolithic strength, and higher edge strength than other glass ceramic materials, other metal, or metal-free restorations.

Yet lithium disilicate is not the only advanced material being used to expand dental CAD/CAM capabilities. Acrylate polymer blocks (Telio CAD, Ivoclar Vivadent) combined with digital processes reduce several obstacles affiliated with traditional temporization, including impression and mixing errors, polymerization shrinkage, and difficulties with cleaning. This allows accurate provisional restorations to be fabricated, which in turn benefit the overall restorative process.

Such provisional restorations serve as the basic template for the definitive restorations and work to ensure their predictability by aiding in the design of the occlusion, structure, and shape of the proposed restorations.

When CAD/CAM equipment is chairside, it improves both workflow and efficiency. The following case demonstrates the capabilities of CAD/CAM technologies for fabrication of provisional and definitive restorations.

Case Presentation

A 59-year-old female patient presented with crowded teeth and a desire to change the general appearance of her smile (Fig. 1). Her left lateral maxillary incisor was naturally positioned too far labially, casting a shadow on the left canine and creating a darkened appearance. Orthodontic treatment followed by an evaluation for veneers was proposed, but the patient declined orthodontic treatment at this point in her life.

Fig. 1 -- Close-up facial view of the patien's dentition.

An intraoral digital scan (Fig. 2) (Trios Color, 3Shape) was employed to capture an accurate view of the patien's dentition to assess the feasibility of correcting both the positional irregularity of the lateral incisor and the general appearance of the teeth with full-coverage restorations on the six maxillary anteriors. To further develop this treatment plan, proposed margins were outlined in the digital software. The stone view of the scan allowed the clinician to see the original contour of the patient's teeth and propose alterations (Fig. 3).

Fig. 2 -- Pre-treatment intraoral scan with the 3Shape Color Trios to evaluate the feasibility of correcting the positional irregularity with full coverage restorations on the six maxillary anteriors. The incisal view of the scan shows extreme crowding.

Fig. 3 -- (a) The "stone” view of the scan and identification of the six teeth that will be diagnostically "waxed.” (b) The anticipated crown margins are identified by the red line.

Since the right central incisor required the fewest changes, it served as a guide for the remainder of the design (Fig. 4). Viewing the proposed design from the incisal illustrated how the right canine would be placed slightly more labially, and the right lateral would have contour added to the mesial of the labial surface to ensure overall harmony (Fig. 5). The left central would have contour added to the labial, and the incisal edge would also be positioned more labially. The left lateral incisor was recontoured to the lingual, while the left canine was contoured to the labial to adjust for the shadow of the protruding lateral incisor.

Fig. 4 -- The completed diagnostic design. The gray shows the original contour of the patients teeth and the ivory color shows the alteration in contour that is anticipated. The right central incisor is going to be changed the least and will be the tooth that will guide the new design. Once that decision is made the left central incisor is altered by creating a mirror image of the right central. It is completely ivory in color to indicate that it is going to be positioned further forward to create the illusion of symmetry.

Fig. 5 -- The view from the incisal is even more dramatic. The right canine is going to be positioned slightly more labially. The right lateral will have contour added to the mesial of the labial surface to create the appearance of harmony with the canine and central. The left central is recontoured to have more material on the labial and its incisal edge is positioned more labially to create symmetry with the left central. The left lateral incisor is recontoured dramatically to move the entire tooth more to the lingual while the left canine has a slight amount of contour added to the labial to bring out of the shadow of the protruding lateral incisor.

The laboratory technician completed the digital proposed treatment plan, which was reviewed and approved by clinician and patient (Fig. 6). The provisional restorations, calculated to be 0.8 mm thick and fabricated using Telio CAD, were then designed in the CAD software (Fig. 7). Once the completed provisional restorations were returned to the office for the first clinical visit, the six maxillary teeth were prepared and the Telio CAD temporaries were then tried in (Fig. 8). This actually served as a guide to ensure adequate reduction. The temporaries were then relined and temporarily cemented. The patient was allowed to function with the provisional for several weeks.

Fig. 6 -- (a) The technician, acting as a true digital designer, shows me the completed proposal and we both show it to the patient. She likes the proposed change and approves of the plan: six e.max CAD crowns. (b) The completed design proposal (digital diagnostic wax-up) with the color turned back on.

Fig. 7 -- Once this plan has been completed by the technician, approved by the doctor and the patient, we have the software create the temporaries. They will be 0.8 mm thick and will be milled in Telio CAD by a milling center.

Fig. 8 -- (a) The completed temporaries which have been milled by Core 3D are returned to the office in a few days. (b) At the next visit all six teeth are prepared and the temporaries relined. The patient is asked to function with the temporaries for a few weeks and give us her feedback. This "test drive” allows her to evaluate the function and the esthetics of the new design. Changes can be made if necessary, but patient is thrilled with the change, as is her family.

Once approved by the patient, the provisionals were scanned during the second clinical visit for use in designing the definitive restorations and removed. The gingiva was then retracted, and the preparations, adjacent teeth, and bite registration were all scanned (Fig. 9). These scans were merged with the scans of the provisional restorations to develop the definitive restorations (Figs. 10-11). The restorations were milled from IPS e.max CAD Block HT B1 using a Planmeca- E4D mill.

Fig. 9 -- After the temporaries are scanned and the teeth are prepared, (a) the teeth are anesthetized and the gingiva retracted and scanned. (b) The opposite arch is scanned as well along with a bite registration to articulate the two arches. At this visit the final color is selected for her six crowns.

Fig. 10 -- The "stone view" of the scans.

Fig. 11 -- Now it is relatively simple to "morph" the scan of the temporaries onto the preparations. When the appearance of the six teeth is "marbled" showing both grey and ivory, the two scans are aligned. And the proposal can be sent to the mill. An E4D "wet" mill is used to mill six full-contour e.max CAD crowns.

A die model was also fabricated at the milling center using 3-D printing based on the scans (Fig. 12). The model was used to fit the IPS e.max CAD crowns and verify contacts and occlusion. Surface texture was carved in by hand, after which the crowns were stained, glazed, and hand polished.

Fig. 12 -- Die model, milling, blue block, and final steps.

They were then tried in, compared to photographs of the patie'’s original dentition, and approved by the patient (Fig. 13). The restorations were cemented using resin-reinforced glass ionomer cement (Fuji Plus, GC America) after a final comparison.

Fig. 13 -- Close-up facial view of the patient with definitive restorations tried in.

Conclusion

CAD/CAM technologies, when used with advanced materials such as lithium disilicate, are eliminating previous difficulties with indirect restorative dentistry and simplifying the overall process. It behooves clinicians and laboratories to earnestly consider the possibility of adding such a system to their workflow, both for their own and their patien'’ benefit.

Acknowledgments

Marisa Notturno and Pasquale Fanetti, technicians at NYC Prosthodontics, completed the laboratory procedures, including digital design.

Jonathan L. Ferencz, DDS, is a graduate of the New York University College of Dentistry with a specialty certification in prosthodontics. A clinical professor of prosthodontics, Dr. Ferencz also practices privately at NYC Prosthodontics in Manhattan. He is a diplomate of the American Board of Prosthodontics. Reach him at [email protected].