Modern smile rehabilitation has been made more predictable with digital workflows. The main objective is to achieve a result that is in harmony with the face and is minimally invasive. The understanding of function is key to longevity in each case. The new digital approach will provide precise planning allowing dentistry to be fully guided. A new generation of monolithic materials for direct and indirect restorations have amazing physical and optical properties, added to this the libraries of natural teeth allow dentists to achieve superior results that can focus on aesthetics, function and biology.
The issues associated with this case included failed composite restorations, the need to close spaces, and the request to improve color. It is essential to remember the patient’s main complaint was to improve his smile, so the case needs to be facially driven in order to achieve the ideal result. Treatment planning needs to start with the face.
When analyzing the face it is important to realize that the smile is dynamic. We require a series of photos or possibly a video. This will allow correct decisions regarding, central incisor edge position, tooth proportion, and most importantly the required smile curve. An ideal smile curve should follow the curvature of the lower lip.
START WITH 2D
Digital Smile Design (DSD) should be the starting point of all smile rehabilitations. The process of orofacial analysis usually involves mathematical rules and straight lines, however, it is evident that in many cases facial asymmetries exist, so the understanding of how rather develop smiles that are in harmony with the face and not symmetrical is vital. Facial flow concept suggested by Bruno Perera and Christian Coachman, utilizes landmarks, glabella, the tip of the nose, the philtrum, and the center of the chin we can see our patient has a slight deviation/flow to the right. Understanding how this affects the treatment will allow us to get aesthetic results that are more organic and balanced as the teeth, gums, and face work together. The smile frame will then determine the central incisal edge position, ideal tooth proportions, and the smile curve. With the help of libraries of natural teeth and artificial intelligence, it is possible to choose teeth that will provide ideal facial harmony.
2D TO 3D
The 2D design is then moved to a 3D design, creating a digital “wax up”. The software used here is Smilefy, and the 3D design is facially driven. Once the ideal treatment has been finalized, with the patient accepting the proposed treatment, the 3D design will be used to guide the treatment. The final result will be assessed by digital quality control to ensure the treatment copied exactly the 3D design.
DSD I this case shows that it was required to lengthen the upper incisors, it was also important to adjust the form of the canines in order to provide canine guidance and complete the smile curve.
The 3D (digital design) STL file is used to print a 3D model which will be used for the mock-up. The mock-up or “test drive” will confirm the aesthetics, and function, and provide information regarding the amount of tooth preparation, color, and ceramic choice for the CAM restorations.
All restorative dentistry should be minimally invasive. When choosing indirect restorations we should work additively, as this allows for conservative tooth preparation to obtain the final substrate to be enamel wherever possible.
The mock-up will be the starting point for the guided tooth preparation.
Guided tooth preparation, through the mock-up, creates perfect space for ceramic restorations, it also gives control over the amount of tooth preparation. We use specific depth-cut burs to ensure the space is controlled. As a rule, the most gingival cut is 0.3mm, the remaining facial cuts will be 0.5mm – 0.7mm and the incisal 1mm – 1.5mm. Once the depth cuts have been done the mock-up is removed to show where facial and incisal tooth reduction is required, this will ensure ideal space for the fabrication of the CAD CAM ceramic restorations to copy exactly the 3D design/mock-up.
After the guided tooth preparation protocol we found that the case was entirely additive. However, when closing spaces, it is essential the sub-gingival margins are prepared inter proximally allowing for the correct emergence profile of the ceramic. Tooth preparation is also required for the ideal path of insertion and to ensure the future embrasures copy the 3D design/mock-up. The preparation is still limited to enamel with entirely rounded edges.
It is essential to use silicone stents to confirm adequate tooth preparation as well as the portion for the intended new embrasures determined by the 3D design/mock-up.
For the ceramic restorations we need to communicate to the laboratory the shade of the final tooth preparation (stump shade). One of the most common is the Natural Die Material Shade Guide from Ivoclar. The shade nomenclature uses ND and then a number from one to nine. One of the advantages of this system is the technician can actually fabricate the die from the stone that matches the stump shade you chose. This better allows the technician to see a similar color and light effect that you will see with the restoration in the mouth. We also provide the laboratory with the intended shade of the new restorations.
It is essential to take a digital impression (IOS) with the entire margins exposed this is done with the double chord technique. An additional scan is made of the tissue and the preparations before the chord is placed. This pre-chord IOS is vital to allow the technician to create ceramic restorations with the ideal emergence profile and place the contact point in the perfect place. This is a big advantage of using digital impressions.
The combination of the 2 IOS’s one with chord and the other without, allows the technician/CAD to create the ideal emergence profile of ceramic restorations as well as placing the contact point so that no black triangles are present or if it is placed too apically, so causing biological problems.
Restoration of the incisors will be monolithic milled e.max, of course in smile rehabilitation we need to address both aesthetic and functional needs. It was vital in this case to include the canines to provide canine guidance and ensure the longevity of the restorations. Canines can be extremely difficult to prepare for veneers due to the loss of enamel through abrasion, enamel as a substrate is vital to the long-term prognosis of modern adhesive restorative dentistry. As a result, it was decided to restore the canines with composite, using the injection moulding technique. This technique allows for a nonpreparation so preserving the residual enamel.
A separate 3D-printed model is provided with the design for the canines with the tooth preparation of 12-22, this was used to fabricate a clear silicone stent (GC Exaclear) for the injection moulding. It is important when combining injection moulding with indirect ceramic restorations to complete the composite before the ceramic is fitted.
In this case GC Genial injectable was used due to its superior physical and optical properties. The shape of the canines was determined in the initial 3D design to ensure ideal canine guidance to protect the occlusion. An Optragate from Ivoclar was used to help with isolation during the bonding.
For isolation for cementation of e.max restorations, a split dam was used with a chord to retract the gingiva giving better moisture control and removal of residual cement. With all adhesive dentistry, the substrate surface is pre-cleaned with 29-micron aluminum oxide sandblasting (Aquacare).
Immediately post cementation, we can be 100% confident that the papilla will fill between 11 and 21 due to the information supplied with the IOS scan done without a chord. E.max BL1 multi block was used to mill the ceramic restorations, AO1 (opaque/dentine) shade for the composite injection moulding restorations. Pre-treatment home tooth whitening was carried out with White Dental Beauty 10% carbide peroxide in trays as the patient.
2 weeks post-op we can see the beautiful pink-and-white integration, as well as the optical integration of the ceramic and composite monolithic restorations.
Beautiful facial integration due to correct value and naturally shaped ceramic. Correction of the smile curve is vital in smile rehabilitation.
The success of this was a result of precise planning (DSD), digital workflow allows for guided dentistry so coping exactly the 3D plan. Controlling the tooth preparation allowed us to keep all bonding substrates to the enamel, this has a positive effect on the longevity of the restorations. The combination of milling (indirect) and injection moulding (direct), both part of a fully digital workflow guarantees an ideal aesthetic outcome.
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