Welcome to B4D Crown & Bridge
Crown & Bridge User Manual
Full Contour Crowns
1. Before you begin - making your first crown.
There are some basic requirements before starting your crown & bridge work. Some of these procedures are common to most crown and bridge work cases. For example, for most cases, you will need to first align the scans/models into the centre of Blender's 3D work environment, then place the dies, the antagonist and the future restoration (tooth/teeth from the tooth library) into the correct collections. These steps are broken down into small videos in this manual, and are covered in more detail in the module learning tutorials. The crown and bridge module has a level of assumed dental knowledge and practical Blender skills. This step by step manual is also designed to help you along the way.
2. Sectioning Scans Sub-menu
Intra-oral scans, scans without sectioned dies, or virtual dental models will need to be sectioned first. This is done so the tooth margins can be clearly marked without neighbouring teeth causing interference.
3. Drawing the Surfaces - Using margins derived from the Model Designer Module
If you've outlined the tooth margins with the Model Designer module you already have margins stored in your outliner window. If you are working with scans that do not involve ditched models, refer to the next video. Your Model Designer margins will now be used to generate 'Surfaces'. Surfaces overlay the green segments and ultimately play a large role in the creation of the fitting surface for the crown. Before you begin, select the dental model together with all the dies, then place these into the Working model collection. Press the 'Working Models to Collection' button.
4. Drawing Surfaces - Outlining new margins from the intra-oral scan.
If you did not create margins in the Model Designer stage, you can work with open mesh scans. You will still need to ensure you have followed the first couple of steps. These were aligning the scans into Blender's centre, followed by placing the objects into their correct collections.
In this section, you will create fitting surfaces. After outlining the tooth margin a green 'segment' model is generated. A 'Surface ' is then created, which in turn is used to make the fitting surface for the crown. Green 'Surfaces' for lower crowns, yellow 'Surfaces' for upper crowns.
5. Drill Compensation - Blocking out to access sharp and pointy areas.
Some tooth preparations include sharp and pointy areas. In order for the milling machine drill to get access into these areas it is important to create some additional space. This is referred to as the 'Drill Compensation'.
6. Surveying and blocking out - Common to all procedures
Surveying is an important part of Crown & Bridge work. Blocking out undercuts is done separately for upper and for the lower teeth. The menus are colour coded and follow the same system as the Surfaces - yellow for upper and green for lower.
7. Contacts & Margins
At this stage it is important for the software to distinguish between the abutment surfaces and the contact surfaces. We have already identified the contact surfaces in the previous step. In this step we will identify between the contact points and the abutments, and then make margins for the abutments.
8. Spacer and Zone
A die spacer is a crucial space between the fitting surface of the crown and the tooth preparation for the cement. This feature requires some user input because of the different material requirements. A safety zone is also an integral part of the crown making procedure because it prevents the final restoration from becoming too thin. The green safety zone is an indicative shell only and the mesh of the final restoration needs to cover it. You can create a die spacer and a safety zone by using the Auto Spacer button.
This sets a default for the safety zone of 0.5mm. The value on the slider will show 1mm. You will need to double any safety zone and die spacer value on the slider that you are wishing to alter.
9. Occlusion & Mesh Editing
The occlusion can be carefully calibrated by adding a tiny offset to the antagonist model. This means you are incomplete control over how much occlusal contact you want to have. For example, no occlusal contact, light occlusal contact or hard occlusal contact. A live cutting tool is used to view the cut before it is made. The anatomy of the crown can therefore be preserved as the restoration is lifted higher or lower in the bite. Some areas can also be thickened which are too close to the safety zone.
10. Generating Crowns
In this step we will generate the crown. The mesh of the restoration will need to be pulled over the tooth margin. This is done so the mesh of the restoration can adapt itself to the margin. A thickness map can be used to visualise the thickness of the crown.
Creating precise contacts is key to fitting the crown into the patient's mouth. The contact areas were previously included in the surveying procedure, which means the path of insertion has already been determined.
Multiple Crown Design
When designing multiple crowns follow the same first steps as outlined with single crowns. With multiple crowns you will need to work with an interproximal cutting tool to individualise the crowns. To recap, first align the scan into Blender's centre, sort the working model, the antagonist and the teeth into their collections, section the scan into Segments, then create the Surfaces on the Segments. This includes contact areas. Following this, look for sharp pointy areas and block these out with the Drill Compensation submenu. Survey the Surfaces next, this will create the blue abutments. The Contacts will need to be separated out from the blue abutments, go to the Contacts and Margins submenu. Select the contact areas and name these. The Contacts will turn pink.
Articulation & Dynamic Adjustments - Process 1
This two part guide will show you how to include the articulator in your crown & bridge work. It is often necessary to consider lateral and protrusive excursions when adjusting the bite, especially when designing multiple crowns. Since the lower jaw can be fully animated, the articulator is used to dynamically cut all of those movements. A basic working understanding of the Articulator & Virtual Facebow module is a prerequisite when working with this module.
Articulator & Dynamic Adjustments - Process 2
In this second part we will describe how to create the dynamic cut on the occlusion of the lower crown. At this stage ensure the articulator animation is fully functional. This was described in the previous part. You would have then followed the general procedure for making a crown. These involved placing all relevant objects into their collections, surfaces have been constructed, surveyed and blocked out, and the all contact areas have been selected and turned pink. The support margin is now also in place. Under static occlusal adjustments you would now follow the Occlusal Adjustment submenu, as was previously described. The workflow deviates away from this submenu since we will perform the dynamic cut within the articulator module.