Jonathan L. Ferencz, DDS, FACP

	Digital intraoral scanners, as well as stand-alone and complete computer-assisted design (CAD)/computer-aided manufacturing (CAM) equipment are powerful and efficient tools in today’s dental practices. They eliminate the need for traditional analog impressions and wax-ups, as well as the conventional hands-on fabrication processes associated with all-ceramic restorations.

	As a result, in one digitally centered workflow that could be implemented, impressions are taken with an 

, not conventional materials and trays. Computer software is used to digitize, analyze and manipulate the scanned images, instead of pouring models. Restorations are designed with CAD software, not by hand-waxing models, after which they are milled through a CAM process, rather than by pressing and/or layering. 

Related article: How is digital technology REALLY being used?

	A male patient in his mid-60s presented with a chief complaint about the esthetics of his anterior maxillary and mandibular teeth (crowding, severe tetracycline staining) (Figs. 1 and 2). Orthodontic treatment was suggested. However, because the patient had fairly significant sleep apnea requiring nighttime wear of a custom-molded device, he declined this option.

	An initial scan of the patient’s preoperative condition was completed using a digital intraoral scanner (

) (Figs. 3-6). This eliminated the need for traditional analog impressions.

	Up next: The complete technique and the amazing results

), the scans were manipulated to virtually alter the patient’s existing dentition into the final restorative state, create a digital diagnostic wax-up, and demonstrate treatment options to the patient (Fig. 7), all without patient discomfort or the time-consuming steps involved with traditional impressions and models.The proposed treatment involved placing milled monolithic lithium disilicate (

) full-coverage crown restorations on seven maxillary teeth (#6 through #12) and six mandibular teeth (#22 through #27). The patient approved the treatment plan.

	The initial assessment indicated that the treatment was too extensive to complete in one day. However, the digital diagnostic wax-up enabled more efficient tooth preparation and provisionalization. Based on the digital wax-up, 

 were milled in the practice prior to the second appointment from PMMA blocks (

), which eliminated the challenges associated with traditional temporization processes (e.g., polymerization shrinkage, clean up, impression and mixing errors).

 created provisionals also contributed to an ideal fit, strength, and durability.

	During the second appointment, the teeth were prepared (Figs. 8 and 9) and digital scans taken (Figs. 10 and 11). The milled provisionals were relined, cemented and customized, enabling the patient to “test-drive” the proposed treatment and share his desired alterations prior to fabricating the permanent restorations. The patient completed a one-week trial period and, upon returning, requested modifications to the maxillary provisionals, which were made.

	He returned again two weeks later, at which time he approved the provisionals for comfort, proper occlusion and esthetics. The provisionals were digitally scanned to serve as templates for the final restorations and enhance their predictability by facilitating the design of their shape and occlusion (Figs 12 and 13).

	Final restoration design and fabrication

Even when provisionals are required, complete CAD/CAM workflows achieve a fast turn-around and efficiency for designing and fabricating temporary and permanent restorations,

 which was essential to allow the patient to return to wearing his apnea device as soon as possible. The final crowns were designed based on the scanned provisionals (Fig. 14), then wet-milled (

) in the practice from medium opacity monolithic lithium disilicate blocks (

) in shade A3.5. The selected material contributed to high esthetics, eliminated the challenge of working with different materials and masked the patient’s underlying tetracycline stained tooth color.

	A 3D model was designed and printed for use in controlling contact points, occlusion, and surface texture after milling and while characterizing, staining, and glazing the restorations. Based on the same digital information previously obtained, 3D models have been accurate and reproducible.

	Two weeks after the patient approved the provisionals, the definitive crowns were placed, and the patient was thrilled with the outcome (Figs. 15 and 16).

	This case demonstrates that digital dental techniques like intraoral scanning, digital diagnostic wax-ups and CAD/CAM milling are changing the way dentists provide quality treatments. The workflow model here did not require any traditional impressions or models, but relied exclusively on digitally obtained and transferred clinical patient information.

	1.     Miyazaki T, Hotta Y, Kunii J, et al. A review of dental CAD/CAM: current status and future perspectives from 20 years of experience. 

	2.     Fasbinder DJ. Digital dentistry: innovation for restorative treatment. 

	3.     Telio CS, Telio CAD Instructions for Use. Ivoclar Vivadent AG, Schaan / Liechtenstein; 2010:1-36.

	4.     Beuer F, Schweiger J, Edelhoff D, et al. Reconstruction of esthetics with a digital approach. 

	5.     Zimmermann R, Seitz S, Evans J, et al. CAD/CAM and lithium disilicate: an anterior esthetic case study. 

	6.     Fasbinder DJ, Dennison JB, Heys D, et al. A clinical evaluation of chairside lithium disilicate CAD/CAM crowns: a two-year report. 

	7.     McLaren EA, Phong TC. Ceramics in dentistry: classes of materials. 

	8.     Sousa MV, Vasconcelos EC, Janson G. Accuracy and reproducibility of 3-dimensional digital model measurements. 

Articles

A technique showcasing the latest digital tools and how they helped create a satisfied patient.

Technique: Using digital diagnostic design to achieve great results

	Computer-aided design/computer-assisted manufacturing (CAD/CAM) systems and machinable all-ceramic materials (e.g., zirconia, lithium disilicate) represent exciting new ways for dentists to deliver prosthodontic care to patients.

	CAD software enables virtual smile design, drives the restorative process and ultimate CAM fabrication, and facilitates engaging patient education about the clinical, functional and esthetic rationale for proposed treatments.

 Cases can be treated in one dental appointment or, when more complex, in a more efficient and accurate manner when CAD/CAM processes (e.g., printed models, milled provisionals) are used.

Read more: How is dental technology REALLY being used?

	The cornerstones of a CAD/CAM based workflow are digitally scanned intraoral images that replace analog impressions and form the basis of virtually and digitally designed CAD representations of proposed restorations.

 Digital diagnostic “waxups” can be used to assess the treatment plan, and once patients approve the design, the teeth can be prepared and digital intraoral impression scans can be taken.

	Digital diagnostic “waxups” based on CAD designs can also be used to create CAM-fabricated provisionals that demonstrate the anticipated contours, shape, length, function and esthetics of the final restorations. After the patient approves the provisional restorations, those can also be digitally scanned for designing the final restorations, including shade determination, and the CAD software used to finalize the proposed restorations.

Read more: Top 10 tech trends that will define 2017

	Contributing to increasing applications of dental CAD/CAM has been the introduction of material advances (e.g., lithium disilicate, zirconia) specifically designed to produce esthetic, functional and cost-effective alternatives for prosthodontic cases.

 In fact, monolithic zirconia restorations (e.g., 

, Ivoclar Vivadent) that can be individually characterized are now possible with CAD/CAM to help dentists realize greater efficiency and patient comfort when treating multiple-unit cases.

An 88-year-old man presented for restoration of tooth #25, which was fractured and had been endodontically treated (Fig. 1). A thorough intraoral and radiographic examination was performed, which revealed damage to the remaining anterior mandibular teeth incurred over the years as a result of scaling and curettage (Fig. 2). This damage to the

 root surface of the lower incisors-which was visible on the radiograph (Fig. 3)-is known as “Riffle-ization.” Described by Dr. Riffle as a technique for removing every last bit of calculus during repeated root scaling, what is now known as “Riffle-izing," ultimately-over the years-changes the shape of the neck of the tooth to resemble an hour glass.

	Therefore, based on the clinical and visual evaluation, the preferred treatment would be to restore the fractured #25 with a post and crown and four splinted crowns to restore the anatomy of the four incisors and increase their resistance to both mobility and fracture.

However, four treatment options were presented and discussed with the patient:

			Extraction and replacement with an implant,

			Extraction and replacement with a six-unit fixed partial denture,

			Post/core and individual crown for tooth #25, and

			Post/core for tooth #25 and four splinted crowns for teeth #23 through #26.

	Because the patient was concerned about undergoing lengthy implant treatment and preferred to avoid extraction if possible, the fourth option was selected. 

	In the past, the splinted crowns required for this case had to be constructed with porcelain-fused-to-metal (PFM).

 Today, the use of zirconia allows for a stronger, more esthetic fixed construction.

 Therefore, after analyzing all of the case information, it was decided with the patient that the final treatment would consist of splinted monolithic zirconia (Zenostar/Wieland, Ivoclar Vivadent) crown restorations.	 

Treatment began by taking an intraoral 3D impression scan (

) (Fig. 4), after which a digital diagnostic “waxup” was created using Dental Designer (Fig. 5). Using digital intraoral scanning and digital “waxups” eliminated the need for time-consuming conventional impression taking, saving the patient time and eliminating discomfort. Additionally, proper shading, tooth size and contouring could be determined by examining and manipulating the digital impression/model images and 

discussing the proposed changes with the patient.

	The diagnostic design, as approved by the patient, was then used to create dry-milled provisionals from PMMA using the Zenotec select Hybrid (Fig. 6).

Additionally, a pattern was created for the post/core for tooth #25, cast in gold, and cemented with 

. The lower incisors were prepared for all-ceramic crowns, and the milled provisionals were relined and cemented. There was no need for the dentist to hand-fabricate the provisionals, or for the patient to undergo impression-taking for creating matrices for provisional fabrication.

The patient returned a week later and expressed his satisfaction with the esthetic design of the four provisional units. During this appointment, the provisionals were now scanned with the intraoral scanner, and this “Pre-prep scan” was used to design the final restorations (Fig. 7). Once appropriately anesthetized, the provisionals were

 then removed and the preparations cleaned with chlorohexidine 2%, after which they were also scanned (Fig. 8). Prior to a digital workflow, these impression processes would have required the use of trays and elastomeric impression materials, pouring of models and considerable chair time. In this case, the digital scans were used to create digital 

		The pre-prep scan was modified slightly to close the spaces between the lateral incisors and the canines, and then used to create the final design of the monolithic zirconia construction (Fig. 9). The software was simply instructed to morph the provisionals as necessary, margins were set using the CAD tools, and the software automatically

 ensured adequate space and thickness for the restorations.

		The file was sent to the Zenotec mill, and a Zenostar MT zirconia puck was selected, after which the design file was nested in the puck (Fig. 10). However, at the same time that the restoration CAD .stl file was sent to the laboratory for milling, the file was also used to enable production of a 3D-printed model with removable dies for verifying the proximal and occlusal contacts of the final 

restorations. Then, when the milled restorations were completed, they could be tried and characterized on the printed model, then glazed and hand polished.

		Prior to milling, the software created a simulation of the milled construction. This allowed the user to check for undercuts and preview the tool path (Figs. 11 and 11a). The Zenotec Hybrid Select then completed the milling of the zirconia construction (Fig. 12). 

After milling, the frame was removed from the puck and prepared for coloring in the “green stage”, prior to sintering (Fig. 13). The Zenostar Color Zirconia was then used to color the zirconia. Coloring in the pre-sintered green stage allows penetration of the colors, thereby improving the esthetics (Fig. 14).

First, the dentin color was applied (Fig. 15), followed by the orange modifier to color the root area of the crowns (Fig. 16).

		The next step was applying the incisal coloring 

(Fig. 17). The now colored green stage zirconia construction was then sintered using a sintering furnace (e.g. 

) on Program #5, which took approximately three hours and reached a temperature of 1530° C.

		As previously described, a 3D-printed model was obtained using the CAD software (e.g., 

3Shape Model Builder) module and a 3D printer (BEGO VARSEO). This model was used for the final check of contacts, occlusion, and surface texture (Figs. 18 and 19). To complete the surface coloration of the restorations, stains and glazes (e.g. 

		The patient then returned for final try-in and cementation of the definitive CAD/CAM restorations. Because the patient was directly involved in the diagnosis, evaluation, smile design, treatment planning and provisionalization evaluation-and because the final restorations were designed based on digital replicas of the approved 

provisionals-there were no unanticipated results. In fact, no adjustments were needed to the contacts or occlusion, and the patient approved the esthetics. The splinted crowns were then cemented with resin reinforced glass ionomer cement (Figs. 21 and 22).

		Dental CAD/CAM systems and machinable all-ceramic materials have changed the face of dentistry and made the prosthodontic process easier and more efficient. Higher-quality and more esthetic restorations can 

be produced in far less time than would be with conventional, hands-on fabrication techniques, and the possibility of errors and discrepancies are greatly reduced. As demonstrated in the multiple-unit case presented here, CAD/CAM techniques enabled virtual smile design, drove the restorative process and ultimate CAM 

fabrication, and allowed the patient to actively participate in decision and evaluation processes.

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		2.     Gtith JF, Keul C, Stimmelmayr M, et al. Accuracy of digital models obtained by direct and indirect data capturing. 

		3.     Beuer F, Schweiger J, Edelhoff D, et al. Reconstruction of esthetics with a digital approach. 

		4.     Fasbinder DJ, Dennison JB, Heys D, et al. A clinical evaluation of chairside lithium disilicate CAD/CAM crowns: a two-year report. 

		5.     Larsson C, Wennerberg A. The clinical success of zirconia-based crowns: a systematic review. 

The Zenostar Concept: Guidelines for dental technicians/clinicians.

		7.     Thalji GN, Cooper LF. Implant-supported fixed dental rehabilitation with monolithic zirconia: a clinical case report. 

		8.     Beur F, Stimmelmayr M, Gueth JF, et al. In vitro performance of full-contour zirconia single crowns. 

. Emergency direct fabrication of a resin fixed partial denture by using a ceramometal crown with reinforcing woven polyethylene ribbon as a pontic. 

A look at creating monolithic zirconia splinted crowns utilizing CAD/CAM techniques.