4.1.2.1 Step‐by‐Step Procedures: Dental Implant Impressions

Although the intraoral scanner software will guide the user through a scanning sequence, the information gathered is similar among different scanner brands. Therefore, correct use of an intraoral scanner is a powerful and fast method for the acquisition of dental implant and oral tissue data including implant tridimensional location, noncompressive impression of soft tissues, gingival emergence profiles, previous prosthesis contours, occlusion/bite and vertical dimension, opposing arch, and oral tissue colors and textures.

• Previous prostheses scan: information on a previous restoration is generally useful, sometimes even without being perfect, because it helps the designer with more visual references. Sometimes if restorations such as ceramics are present in the mouth, scanning powder can be applied to oral tissues and restorations to diminish light reflexion and provide a faster scan.
• Implant tridimensional position: positioning a dental implant scanbody intraorally can be as simple as installing any other component, but to ensure precision of the procedure it is mandatory to double‐check the coupling interface to avoid misfits (Figure 4.3). To access the fit of the scanbody onto the implant in subgingival cases, the user can take oral radiographs. However, some intraoral scanbodies are fabricated with polymers such as PEEK, that impair radiographic verification. Additionally, polymer‐based scanbodies may have a limited time of use because the coupling interface may be distorted more easily than metallic interfaces. When taking the digital dental implant impression, the scanner locates and registers surface reliefs indistinctly, in order to construct a tridimensional mesh (Figure 4.4). Most scanners are not able to automatically determine the dental implant and scanbody position. In subsequent steps, the location of the dental implant as well as other dental structures must be marked by the user. However, more recent dental scanner systems and new scanbody versions contain graphical patterns that can be automatically recognized by the software. As a result, the dental implant position will appear aligned to the other dental structures in the CAD software, allowing the design of the final restoration, including the hexagonal position when the antirotational effect is desired (Figure 4.5).
• Soft tissue impression: intraoral scanning is a fast technique to record soft tissue contours, which is a challenging task in conventional impressions. The user can record delicate structures such as the gingival profile emergence for a restoration after tissue conditioning, with high accuracy and virtually no distortions. For this purpose, a scan of the implant/abutment without the scanbody should also be performed.
• Opposing arch, occlusion and vertical dimension: while scanning, the user will be prompted to record the opposing arch, and subsequently both arches are aligned while the patient occludes in the desired position (maximum intercuspation or centric relation [CR]). The interlocking between the dental arches enables the use of a virtual articulator within the CAD software and provides important references for the creation of a correct restoration, such as the vertical dimension, predicted occlusion, and behavior during mandibular movements.
• Additional information: intraoral cameras and software are continuously evolving to enable a faster and more precise procedure. Additional information can be gathered by the system that can be useful for the CAD designer and clinician, such as dental and gingival shades and textures.

4.1.2.2 Stereophotogrammetry: An Accurate and Fast Alternative

One alternative to the intraoral scans of dental implants is stereophotogrammetry, which is a method of making precise measurements by using reference points within photographs without any contact with the measured object. A recent stereophotogrammetric system has been developed for capturing implant positions, called precise implant capture (PIC). To perform the PiC method, the professional needs a stereoscopic camera (PIC camera; PIC Dental) to record the implant positions. First, the code of each PIC abutment (PIC transfer) must be entered into a software program and then placed on each abutment. Then, the PIC camera is placed 15–30 cm away from the dental arch with a maximum angle of 45° in relation to the transfers. The information captured from the photogrammetric abutments in the camera (PIC file) can then be processed by the software program (PIC Cam Soft v1.1). This software calculates the average distances and angles between implants shown in the photographs, which leads to an accurate relative position of each implant platform in vector format. The resulting 3D images can be saved and exported as STL files.

4.2.2.1 Step‐by‐Step Procedure for Using a Virtual Articulator in a Digital Workflow

• Import the intraoral scans into the software. In this step, the maxillomandibular relationship obtained with the occlusion record will be automatically rearticulated according to the facial arch (Figure 4.6).
• Scan the facebow along with the transfer index. This step is performed with the intraoral scanner and the resulting 3D image exported along with the arches scans. The registration of the facebow with the index is brought into Exocad as a generic mesh, as well as the virtual index that will orientate the correct position of the facebow. After importing the aforementioned 3D meshes, the facebow should be lined up with the placeholder (Figure 4.7).
• Align the mesh of the maxilla with the facebow. As with the traditional set‐up, the maxillary scan can be aligned with the mesh of the occlusal registration of the facial arch. Thus, the digitized upper arch migrates to the position registered in the patient’s mouth (Figure 4.8).
• Import the reference of the maxillomandibular relationship to assemble the lower scan in the articulated set‐up. In this step, the virtual record of the articulation of the arcades is imported. Instead of bringing the bite record files, the associated arcades are brought in a single file. Thus, the alignment of the meshes becomes more precise and predictable due to the greater amount of similar information between the three‐dimensional meshes. After aligning the occlusion record file, the bottom scan is finally aligned, proceeding to the last step of articulating the models (Figure 4.9).
• Final check of the assembly and adjustments of the articulator. With the models in position, it is possible to open the articulator module and select the desired model, in this case the standardized BIOART A7 PLUS. By activating the visualization of the extra meshes, you can validate the index and facebow assembly and fits, as well as the models in position. After this step, measurements of the condylar and Bennett angles are made, and finally the simulation of movements that will be registered and used in all stages of the design process of the previously proposed work (Figure 4.10).

Multidisciplinary assessment in dentistry allows for a more comprehensive and assertive diagnosis, a more rationalized planning and the construction of a workflow that achieves success, fulfilling the goals established at the treatment planning. For this purpose, several technological methods have been developed to allow the professional to use a digital workflow to increase predictability of outcomes [1]. In this context, knowledge of the work protocol and techniques to be used is essential.

4.2.3.1 Esthetic Analyses

There are several aspects to be considered by the professional performing digital esthetic analyses in dentistry. The project of a new smile will be created based on the patient’s diagnosis and conditions. For this purpose, a series of facially driven analyses with photographs and reference lines are performed, aiming at correction of any asymmetries or discrepancies.

Esthetic facially driven analyses usually follow proportions defined by different points of interest and lines of reference. In this context, several facial reference points have been used in dentofacial esthetic analyses (Figure 4.12). Since digital dentistry offers tools for basically the same concepts, general dental esthetic guidelines [4] applicable in conventional workflows should also be taken into consideration. Similarly, discrepancy points should also be identified and carefully considered during treatment planning.

Dentolabial esthetic principles should also be applied along with dentofacial analysis. Among the main objectives of dentolabial esthetic analyses are establishing the proper parallelism between the occlusal plane and horizontal reference lines, the correct inclination and disposition of the teeth with the vertical reference lines, establishing the ideal height of the lower third of the face, and establishing the correct dominance (Figure 4.13).

4.2.3.2 Two‐Dimensional Digital Design of the Smile

Several techniques and graphic manipulation tools in digital clinical photography have been proposed in recent years to perform a two‐dimensional (2D) digital design of the smile. Among the main techniques are the Photoshop® Smile Design (PSD) [5, 6], and the Digital Smile Design (DSD) [7]. These 2D methods enable measurement of proportions between the dental elements and correction of location and size to obtain harmony between facial compositions, facial tooth, and gingival tooth. The major disadvantage of these methods is the parallax effect. For instance, in the analysis of frontal records, the distance of a structure can vary in size and depth, such as in the case of retrusive jaws. One advantage, however, is that several 2D methods of smile design use popular software programs, such as PowerPoint® (Microsoft) or Keynote® (Apple). Some studies have also described the use of 2D photogrammetry, which uses frontal and profile photographs to obtain photogrammetric measurements. However, these are still 2D images that are a snapshot of a 3D dynamic object. Evidence in the literature shows that such techniques still require patient cooperation during acquisition [8]. Furthermore, magnification and distortion may still occur, while no volumetric measurements can be performed. One acceptable method, however, is the association of 2D and 3D dentofacial esthetic analyses [[9], [10]].

4.2.3.3 3D Image‐Obtaining Methods for Esthetic Analysis

Most of the limitations of 2D analyses can be overcome by using 3D photogrammetry or facial scans (see Chapter 2). Such methods will create 3D images as OBJ files, which can be superimposed and integrated with the intraoral scans. The following step‐by‐step procedure was conducted with the NemoSmile® software (Nemotec) and can be performed after obtaining a clinical history and examination, as well as intraoral and facial scans of the patient.

4.2.3.4 Step‐by‐Step Procedure for 3D Dentofacial Esthetic Analyses

• Import the maxillary intraoral scan of the patient into the software.
• Align the intraoral scan with the photograph of the patient. This is done to perform an initial 2D dentofacial analysis of the patient with dentofacial reference lines (Figure 4.14).
• Design a digital mock‐up of the case, based on the resulting position of the reference lines (Figure 4.15).
• Align the resulting digital mock‐up with the facial scan of the patient (Figure 4.16).
• Based on the ideal teeth shapes that resulted from the analyses and on the patient’s needs and expectations, select a digital teeth library. This library will be used in the process of virtual waxing (further discussed later in the chapter). Alternatively, teeth shapes can be taken from an intraoral scan of another patient, for instance, a relative of the patient [11]. This technique has been called “the smile donation concept.” Finally, it is also possible to use artificial intelligence‐based dental software programs, such as Smilecloud®, to select the teeth library and contribute to the digital design of the patient’s smile.

4.2.4.1 Step‐by‐Step Procedure for Dynamic Smile Analysis

• Obtain a facial scan in a stereophotogrammetry cabin: position the patient in a natural head position with the aid of laser‐projected reference lines. Sixteen synchronized cameras capture images in 0.5 seconds. The photographs are taken in maximum smile and rest and exported together in JPG format (Figure 4.17).
• Create the 3D mesh: import the photographs into a 3D modeling software program. Apply the point georeferencing tactic to process the data and create the 3D mesh (Figure 4.18). Save the file in OBJ format.
• Intraoral scan: obtain an intraoral scan of the maxilla, mandible, and intermaxillary relationships. Save data in STL format (Figure 4.19).
• Merge intraoral scan and facial scan: perform file alignment in a CAD software/app using common reference points in both scans.
• Smile animation: develop the smile dynamic path from the rest position to the maximum smile with the help of animation software. Render data and generate a video of the smile to create the 4D virtual patient (three dimensions with lip movements) and allow dynamic analysis of the smile (Figure 4.20).

4.3.1.1 Tooth‐Supported Single Crowns

As mentioned above, the first step in performing a basic digital wax pattern of a single crown is to import the STL files of the digital impressions and bite registration to a CAD software program. The initial screen of most dental CAD software programs contains the project details. The procedure of digital waxing is similar in most of the dental CAD software programs available. For this basic step‐by‐step procedure, intraoral scans of a dental study model were taken with a TRIOS® 4 (3Shape A/S). The dental CAD software program chosen in this case was DentalCAD® (Exocad GmbH) since it contains one of best known software interfaces for digital waxing. The intraoral scans were imported to DentalCAD to design the single crown, as explained below.

Step‐by‐Step Procedure Using Commercial Dental CAD Software

• Open the CAD software program.
• Input patient data.
• Select the tooth that will receive the single crown.
• Select adjacent and antagonist teeth (Figure 4.21).
• Select “Anatomic crown.”
• Select the material chosen to fabricate the crown.
• Select additional parameters if needed (Figure 4.22).
• Click on “OK.”
• Click on “Design” to open the actual DentalCAD software program.
• Select the STL file corresponding to the intraoral scan of the main arch in the file browser that will automatically open (Figure 4.23).
• Select the STL file of the antagonist arch.
• Using the mouse buttons, position the main arch scan in an occlusal view, leaving all margins of the preparation visible, and click to set current view as the orientation axis (Figure 4.24).
• Click on “Next.”
• Click on “Antagonist” (top left of the screen) to show the antagonist arch in the screen (Figure 4.25). If a digital bite registration is desired to articulate the main and antagonist models, import the STL file of the bite registration in the same tridimensional coordinates of the models by clicking on “Expert mode” → Tools → Add/remove meshes.
• Align the virtual mesh of the bite registration with the models by selecting points in common locations on both meshes (Figure 4.26).
• Click on “Align” and select the best fit option to superimpose the meshes properly (Figure 4.27).
• Click to change back to the “Wizard” mode.
• Proceed with the autodetection of the preparation margin by clicking on two different points at the edge of the preparation margin. This will allow the software to automatically detect the location of the finish line of the preparation (Figure 4.28).
• Switch to “Manual” mode to correct and perform fine adjustments to the optimal location of the preparation margins (Figure 4.29).
• Select the magic lantern (available in the “Tools” menu) to change the light direction in the 3D space (Figure 4.30). This allows determination of the optimal location of the preparation margin with higher precision. After adjusting the margin, go to the next step.
• The next step is to check and confirm the insertion axis of the crown. Note that if the axis orientation is not satisfactory, retentive parts will show in red color (Figure 4.31a). Make sure that the preparation margins are visible and that there are no retentive areas in the preparation (Figure 4.31b).
• Click on the “Next” button.
• Select the desired parameters of the crown bottoms (intaglio surface) such as the cement gap thickness (Figure 4.32).
• Click on the “Next” button. A new mesh corresponding to the minimum thickness will be created (Figure 4.33). This will vary among the different materials. In addition, a crown shape will be given by the software to be positioned onto the preparation (Figure 4.34).
• To select a crown shape from the library, choose the desired library or switch back to the “Expert” mode to see a full drop‐down menu of all available libraries (Figure 4.35).
• Adjust the crown dimensions and orientation digitally. This should be done taking into consideration the positions of antagonist and adjacent teeth (Figure 4.36).
• When the optimal position is established, click on the “Next” button. The crown shape will automatically adapt to the preparation margins that were previously outlined.
• Use the brushes to adjust and smooth the surface of the crown (Figure 4.37).
• Perform a final check to make sure that the crown position is satisfactory (Figure 4.38).
• Finally, click on the “Next” button. This will export and save the resulting digital crown design as an STL file (Figure 4.39). The crown is ready to be fabricated (Figure 4.40).

Editor’s note: The basics of dentistry are still the same! However, digital dentistry gives us new tools and methodologies to enhance the predictability of our treatments.

Step‐by‐Step Procedure of Virtual Waxing of Single Crowns Using Nondental CAD Software

Meshmixer® (Autodesk Inc.) is the most used program within free nondental software. It is used by several dental clinics and laboratories to design parts, plates, and models. However, as a nondental software, it has the limitations discussed in Chapter 2. As a result, virtual waxing with Meshmixer takes considerably longer and requires more training than dental commercial CAD software programs. For this reason, an appropriate tooth library should be selected and downloaded prior to commencing the procedure. Teeth libraries compatible with Meshmixer are currently available for free on some webpages. The following step‐by‐step procedure was used to perform the digital waxing of tooth 46 (mandibular right first molar).

• Import the tooth file and library into Meshmixer. Open the program and click on “Import” and add the intraoral scans of upper and lower arches. Once this is done, an object browser will automatically open. This window is essential to identify how many objects and which objects are to be imported into the software. Click on “Import” in the upper left corner, and click on “Append” to import an additional object to the same virtual space in which the intraoral scans were imported. Then, select the tooth to be waxed. The “Object browser” list will show the scans and the crown to be used in digital waxing (Figure 4.49).
• After importing, the crown will need to be positioned on the tooth preparation in the virtual space. To do this, press the “T” key to transform the object and position it. The arrows indicate how to move the plans: the semi‐circle rotates the object; the triangle moves between all axes; the squares of each arrow with different colors will increase or decrease the size of the object; the white square will proportionally change the object’s dimensions (Figure 4.50).
• Make sure that the position of the crown on the preparation covers the entire finish line and slightly exceeds the limits of antagonist (Figure 4.51a) and adjacent teeth (Figure 4.51b). Since there is no way to measure the proximal or occlusal contact depth, the software does not show with colors or densities how much one object is entering into another.
• Use sculpting tools for adjusting and smoothing any areas of the crown, as desired. To do this, click on “Sculpt,” select “Brushes” and choose the brush that suits the requirements of the area to be smoothed.
• Use the “Select” tool to carefully outline the preparation margins. To make it easier and more accurate, decrease the size of the area to be selected (Figure 4.52a). To remove any undesirable areas that were selected by mistake, press CTRL (for Windows systems) or “Command” (for Apple Mac systems) and unselect the extra areas. Once the margin is selected/outlined, use the tool “Smooth boundary” to give a flattened aspect to the mesh of the margins (Figure 4.52b).
• A new “Selection” will be created and identified with another random color. Then, click twice on the region with different color and click twice on the inner border of the area of the selected tooth. This will select/outline the margins and the entire crown (Figure 4.53).
• Click on “Edit” → Extract. Change the offset to 0.05 and accept the change (Figure 4.54). The rationale of this step is to create the cement gap of the crown.
• The extracted object will be still selected. Click twice in the border with different color and press “Y,” which will separate the selected preparation from the model, assuming an aspect similar to a die (Figure 4.55a). Then, press “W” to see the mesh structure of the object. Click twice in the most external triangle of the extracted mesh and twice in the most external triangle of the original mesh. Then, click on “Edit” → Join (or press “J”). The resulting area will be a digital die where the professional will adapt the virtual wax pattern to the margins and perform adjustments (Figure 4.55b).
• After adjusting the crown on the preparation, the professional needs to remove excessive areas (i.e., areas extending further than the actual preparation) and add areas of material that are lacking between preparation and crown. To remove excessive areas, first press “S” to select the desired region (Figure 4.56a). Then press “B” and accept. This will smooth the borders of the region. Then, exclude the region with “X.” Repeat the procedure until all preparation margins are clearly visible (Figure 4.56b).
• The next step is to merge the meshes of preparation and crown. To do that, use the “Select” tool and click twice on all areas containing the preparation (including all areas with different colors). Then, click on “Edit” → Flip normals (Figure 4.57a). Then, click on the crown, hold “Shift” and click on the preparation. Select the option “Combine” to merge the meshes (Figure 4.57b and 4.58).
• To finalize, press “W” to visualize the mesh structure again. Click on “Select” and click twice on the most external triangle of the crown mesh. Then, press “J” and accept.
• The new digitally designed crown is ready. Click on “Sculpt” →Brushes and select the brush type “ShrinkSmooth” to smooth the entire border of the crown (Figure 4.59).

4.3.1.2 Working with Dies

As commonly seen in cases of tooth‐supported crowns conducted with conventional workflows, digital dies can be designed in CAD software programs to facilitate visualization and access to the preparation margins and tooth shape (Figure 4.60). Digital dies can also be 3D printed as removable dies to fit in 3D‐printed dental casts. The presence of the 3D‐printed cast and dies is therefore useful to try in and perform adjustments on CAD‐CAM crowns.

4.3.1.3 Implant‐Supported Crowns

Implant positions need to be transferred to a cast set‐up for the prosthesis to be manufactured. Using conventional workflow, this is done by screwing a transfer abutment to the dental implant to perform conventional impressions with either open or closed trays. Nowadays, several CAD‐CAM techniques are available to plan implant therapy by creating a 3D virtual patient, as explained in Chapter 2. In this context, implant‐supported CAD‐CAM prostheses are the first part of implant therapy to be planned, in order to achieve a prosthetically driven implant rehabilitation (see also Chapter 6 on digital implant dentistry).

Implant‐supported crowns can be digitally designed in a procedure similar to that for single crowns over tooth preparations. The resulting STL files of the crowns can be either 3D printed or milled as CAD‐CAM copings or crowns. For this purpose, either an implant scanbody can be intraorally scanned to digitally transfer the implant position to the CAD software, or an implant stock abutment can be directly scanned as if it was a regular tooth preparation, which eliminates the need for an intraoral scan with the scanbody in position. On the other hand, implant scanbodies are simple to use and are considered satisfactory to ensure accurate location of the abutment margins and implant position. For this purpose, a compatible digital abutment or implant analogue available in the library of the implant system should be installed to be recognized by the software.

The following step‐by‐step procedure was designed for DentalCAD software. Several procedures are similar to the virtual waxing of tooth‐supported single crowns. Therefore, the following list of steps is focused on the aspects that are particular to CAD‐CAM implant‐supported crowns.

Step‐by‐Step Procedure for Implant‐Supported Single Crowns

• At the initial screen, it is usually possible to input data on the material to be used and type of prostheses (e.g., screw‐retained lithium disilicate crown).
• Import the four intraoral scans into the CAD software.
• Select the scanbody of the implant system used in the correct library.
• Match the image of the selected scanbody with the intraoral scan of the scanbody on the model. Click on “Best Fit” to make this procedure easier (Figure 4.61).
• This will make the digital analogue of the implant available in the virtual space (Figure 4.62). Proceed with the normal virtual waxing technique (Figure 4.63), as described in section 4.3.1.1.