April 12, 2021
by Sunny Virdi, DMD; Murad Zaman, DMD; Amarjit Rihal, DDS
New opportunities are one of the many reasons people immigrate from Canada from all over the world. The same is true for our patient who arrived in Winnipeg in 2013 from Adama (formerly Nazareth), Ethiopia. This 37-year-old female was seen as a new patient during an initial hygiene appointment. What immediately struck us was the severe discolouration and mottling throughout her dentition. She informed us that in her city, this presentation was very common, and most people had varying levels of tooth discolouration. Even though she was not experiencing any issues with her dentition she told us she wanted to have white teeth and a “normal” smile.
Photographs, radiographs and models were taken. (Fig. 1) 1.1 appears lighter as there is composite bonded to the surface, verifying if adhesive techniques will work on this level of fluorosis. (Fig. 2) Masking teeth with severe discolouration will always be a challenge. We have to balance the health and preservation of tooth structure with the aesthetic expectation of the patient. Pulp vitality, enamel preservation, and tissue health all have to be respected when completing aesthetic treatment. The more minimal our approach today, the more tooth structure we have to work with in the future.
There are times we have no choice but to prepare the teeth and place full crown restorations. A major advantage of full crowns is the ability to be mechanically retained, which does not rely on enamel preservation for success. For all the reasons discussed above, we wanted to use an adhesive approach in order to conserve tooth structure, but maintaining enamel in these severely discoloured teeth is a major challenge.
Two key parameters that will aid us in masking severely discoloured teeth are: 1. Ceramic thickness and 2. Buccal-Lingual position of the teeth relative to the lips. Of course, the thicker the restoration fabricated, the better we can block underlying colours. However, there is a limit to how thick restorations can be made before compromising pulpal vitality and the longevity of the restoration. This is where the buccal-lingual position becomes critical. Theoretically, the more we can upright the maxillary anterior teeth and reduce their protrusive angle, in combination with adding volume to the vestibular surface, we can increase our ceramic thickness while minimizing tooth structure removal.
The start of any esthetic case begins with a well-designed project with the final result in mind. A simple overlay of proper tooth proportions over the patient’s current situation highlights the improvements and changes we need to make. It is our opinion that clinicians should always entertain the idea of pre-restorative orthodontics before placing veneers.
Our treatment plan started with an orthodontic assessment and an understanding of where the ideal final positions of the anterior teeth should be. An Itero digital scan was taken, and the STL digital files were uploaded to the SureSmile platform. (Fig. 3) As stated earlier, we knew that the teeth needed to be uprighted to allow for minimal preparations, and adequate thickness of the restorative material to ensure the ideal buccal-lingual positioning of teeth.
After aligning the teeth into their correct position, the software divided the motions into a series of steps, each representing an individual aligner. We tried to maintain the arch forms and inclinations of the teeth with the prosthetics in mind, and as a result, a small amount of interproximal reduction (IPR) was prescribed for the maxilla.
Since we chose the DIY option in SureSmile, all STL 3D models were downloaded, 3D printed on a Formlabs 2 printer, and then aligners were vacuformed over the models using a Durformat. Following 15 aligners on the maxilla and 21 aligners on the mandible, Meron’s orthodontic phase was complete.
After completing the Orthodontic phase, some small discrepancies were noted from the simulated outcome, but were not significant since the teeth were going to still be prepared. Overall we achieved our orthodontic goals of derotating the teeth and some degree of uprighting. Next, we began to formulate a digital design for Meron’s new smile. This process started with superimposing a 2D image with an ideal proportions template to see where Meron’s discrepancies lie. (Fig. 3)
The next phase of treatment was converting this 2D digital smile design to a 3D digital wax-up and producing a 3D printed model, along with a copyplast matrix to verify the length and symmetry of the 2D design. This matrix will also be used to create temporaries and our first functional prototype. To begin, the final iTero digital scans were brought into Autocad’s Meshmixer program. Using Christian Brenes’s tooth morphologies, an overlay model was created using the same relative tooth proportions and incisal positions. (Fig. 4) After the design was finalized, it was exported as a digital 3D model and 3D printed using an Asiga ProMAX 3D printer. A flexible copyplast material was vacuformed over the model.
Once the orthodontic movement was completed, the final restorative plan was easily verified intraorally by placing Structure temporary acrylic material in a copyplast tray as a mockup. As advanced as digital dentistry has become, the mockup remains the gold standard for ensuring the planning has been done correctly and the patient can truly understand what our end goal is.
With the mockup in place, the teeth were prepared with the final restoration thickness approaching 0.7-1.0 mm in mind. This is a very useful step with veneer preparation, as it allows the clinician to provide the appropriate reduction while minimizing the damage to enamel, without having to guess how much natural tooth to reduce. Various guides were used to verify the reduction of the facial surface as well as the incisal edge. The interproximal was prepared as well, given the risk of severe discolouration that could be visible from certain views.
Preparations were kept mostly in enamel, with the exception of some interproximal zones. We elected to proceed without immediate dentin sealing covering these areas as they are small enough to be inconsequential to the longevity of the final restorations. A stump shade was taken to best plan for the final restoration. (Fig. 5)
The CEREC Primescan intraoral scanner was utilized to capture a digital impression of the preparations. A single piece of 00 cord was used to retract the soft tissue and expose the margins. This method gives us an opportunity to view our final preparations at a magnified scale and make any adjustments as necessary. The final scan time was clocked to be under 2 minutes. Capturing 10 veneer preps simultaneously is no easy task for any final analog impression material. Digital impressions offer a major advantage for larger cases, when suitable, given the ability to focus on one area at a time. Soft tissue challenges, clinician error, and time are all factors that contribute to making analog impression techniques difficult as case complexity increases.
After scanning, photographs of the preps were taken that will be utilized later in the design process. Temporaries were fabricated with a bisacryl temporary material, using the copyplast matrix as a guide, (Structur 2, VOCO) and cemented with temporary cement. (Fig. 6)
After the case was digitally scanned, it was imported into Dentsply Sirona’s inLab system for final design and manufacturing. One of the main advantages to inLab is the ability to design the placement of your restorations with the facial landmarks. The software will ask you to verify some anatomic features based on an avatar (e.g., the canthi of the eyes).
After the anatomic points were identified, the photo is scaled to the digital model by measuring the patient’s intercanthal width. (Fig. 7)
This smile design feature’s main advantage is that it also dimensionally recreates Meron’s face and allows it to move in any direction with your design. All preparations were then marginated in the software and more detailed tooth morphology was selected to finalize the design. Another advantage of the software was making the design transparent, so we were able to measure the thickness and overall form of the proposed restorations. (Fig. 8)
The final verification was the superimposing of the scanned temporary veneers that we originally based our 2D to 3D treatment plan on. As you can see, we accurately reproduced the basic form and placement of our temporaries, while giving the restorations an enhanced and softened aesthetic design in the software. The designs were then milled using Ivoclar’s e.max LT blocks with the SironaDentsply MXCL mill.
Once milled and crystallized, the veneers were stained and glazed using the Miyo liquid porcelain system. (Fig. 9) A variety of different effects were used to create the natural looking incisal translucency and halo effect.
The patient arrived after wearing the temporaries for 2 weeks and provided feedback of her experience. The patient was able to function within normal limits and was happy with the length and buccal corridor spaces remaining.
The restorations were silanated before the try in process, immediately after etching and removing any debris from the intaglio surface. We used water instead of a try-in paste to assess the visual blocking potential of the restorations. (Fig. 10)
Rubber dam use is always a hot topic for controversy in our profession. Some dentists advocate for its use religiously, some dentists show success without ever using it for restorative procedures, and many dentists used a mixed approach. We believe strongly in using rubber dam to deliver our restorations whenever possible. The freedom to work in a field of absolute isolation in a reliable, predictable way is invaluable.
The prepared teeth were isolated two at a time, so the restorations could be bonded in pairs. (Fig. 11) This allowed us to ensure the midline and two central incisors were placed in the most ideal position, followed by the laterals, canines and finally premolars. This method allows us to maximize our efficiency and reduce the delivery time, while ensuring the final esthetic result will match the try in process. The centrals being delivered together prevents the issue of mis-seating a single central and affecting the midline along with the seating of the second central incisor.
Each tooth was cleaned of plaque and biofilm with air abrasion (PrepStart, Zest Dental Solutions) using 27μm aluminum oxide particles. The preparations were then etched with 37% phosphoric acid for 25–30 seconds on enamel, and 10-15 seconds on exposed dentin. A 4th generation bonding system (Optibond FL, Kerr) was used as an adhesive, but not cured before seating the restorations. Heated composite (AP-X, Kuraray Co.) was used as a cement in this case. Heated composite provides many advantages over conventional cements, allowing for an extended working time and excellent sealing of margins with a resilient material. Margins were finished with a scalpel blade after light curing with a final glycerin layer (LiquidStrip from Ivoclar Vivadent). Rubber dam was removed and occlusion adjusted wherever necessary. (Fig. 12)
The Final Result
Ultimately, we achieved a dramatic change in a very conservative fashion. The patient had to train herself to smile again, as she had avoided smiling for so long. It is clear in the before and after photos, how much more the patient enjoys her new smile. (Fig. 13) It is a special feeling hearing that you changed someone’s life. Dentistry as a profession has the ability to make a difference for so many people and this case demonstrated that to the fullest. The final photos were taken 1 week post-operatively and we see excellent integration of the restorations with the natural dentition. Also, the tissue also rebounded well on 1.2, and will continue to do so. The digital revolution that is rapidly being implemented into dentistry, allows for treatments such as this, to be completed entirely in a single clinic. The ability of digital technology was on full display and we are excited to see the progress it will make in the coming years.
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About the Author
Dr. Sunny Virdi, born and raised in Winnipeg, MB, graduated from the University of Manitoba in 2016. He maintains a full-time ownership role in a group private practice in Winnipeg. Dr. Virdi received postgraduate training in the latest techniques regarding isolation, adhesion, materials science and aesthetic dentistry and is a member of the Canadian Dental Association and the Manitoba Dental Association. Reach him at email@example.com or on Instagram @dmdsunny.
Dr. Murad Zaman obtained his doctor of dental medicine from the University of Manitoba in 2014. Dr. Zaman has since practiced in both Winnipeg and Pine Falls, near Sagkeeng First Nation as well as in Winkler, MB. These experiences have helped to expand his knowledge of dentistry, particularly the surgical aspects. He can be reached on instagram at @dmdzaman or firstname.lastname@example.org
Dr. Rihal obtained his DMD degree from the University of Manitoba, Faculty of Dentistry, in 1995. Dr. Rihal has acquired expertise in CAD/CAM based prosthetic dentistry, involving numerous CAD systems and materials. He is the owner of his own digital lab called Rihal Digital Designs and is a principle partner in a large group practice in Winnipeg.