Restoring a Discolored Central Incisor with CAD/CAM
Stump management and material selection is key for favorable outcome
Dhaval Patel, DDS
Restoring a single discolored maxillary central incisor to a near mirror image of the contralateral tooth is a very difficult task when considering the biological, functional, esthetic, and material dimensions of the procedure. The task gets more difficult if the dentist chooses to complete the restoration chairside with CAD/CAM and without the help of a lab technician and layered ceramics. Stump management and cement and restorative material choice becomes key in ensuring a favorable outcome.
Case Presentation
A 53-year-old man with a discolored maxillary left central incisor presented for treatment. He requested to make the tooth look as much as possible like his other front tooth (Figure 1). The maxillary left central incisor had been treated endodontically as a result of previous trauma when the patient was 16 years old. Further discoloration occurred as the patient grew older. The midline diastema was not a concern and the patient’s only desire was to have both the centrals match as close as possible. After discussing several treatment options that included orthodontia, composite bonding, and veneers, the patient chose to have the tooth restored with a porcelain crown that was fabricated with CAD/CAM same-day.
Tooth Preparation and Material Selection
An enameloplasty was completed on teeth Nos. 8 and 9 until the incisal edge length was acceptable to the patient (Figure 2). The left central incisor was prepped for a full coverage crown. The grayness around the cervical third and patches of discoloration in the middle third were noticeable at this point (Figure 3). Based on past experience, the options for what material to use in the final restoration were narrowed down to a few choices, including:
e.max® CAD LT (Ivoclar Vivadent, www.ivoclarvivadent.com): This would very easily block the dark stump but would not be able to give the incisor translucency to match the other central.
e.max CAD HT (Ivoclar Vivadent): This would look too gray, as it may not be able to block the dark stump but would get close enough for the incisal translucency.
IPS Empress® CAD Multi (Ivoclar Vivadent): If the dark stump could be masked with an opaque sealant, this material would achieve the best incisal translucency.
The IPS Empress was chosen, and while packable composite was used in the past to block stumps, it requires further preparation on the facial to prevent the composite layer from adding bulk. Therefore, Pink Opaque (Cosmedent®, www.cosmedent.com) was selected because it is easy to use and quickly neutralizes dark stains and unsightly dentition. It is indicated for unsightly dentition, such as non-vital teeth, tetracycline stained teeth, or teeth with metal posts and core. It gives you natural restorative results that are not overly opaque and can be used under composite or porcelain restorations. The facial surface of the preparation was etched for 15 seconds (35% phosphoric acid solution, Ultradent, www.ultradent.com), washed, and dried. The bonding agent was applied, air-dried, and light-cured. Pink Opaque was applied with a paintbrush all over the facial surface. It was then light-cured. This material blocked the gray and dark patches on the facial surface (Figure 4).
Scanning and Designing Process
The preparation, along with the adjacent teeth, was scanned in the upper arch folder using the Omnicam acquisition unit (Dentsply Sirona Dental, www.dentsplysirona.com) (Figure 5). The opposing lower anterior teeth were scanned in the lower arch folder. The patient was asked to bite in maximum intercuspation and the facial surfaces of the bite were scanned in the buccal bite folder. In the model phase, the left central incisor was marginated and the correct insertion axis was selected. The software then proposed a crown for the left central. This technique analyzes neighboring and adjacent teeth, and calculates and proposes a restoration design that fits the form and shapes of the other teeth in the arch—the more information available, the more successful the calculation. However, the restoration’s width, incisal edge position, and basic outline form designs did not match that of the right central. Several design tools, along with the grid, were used to make sure the left central matched the right central in terms of length, width, shape, and symmetry (Figure 6).
Milling and Try-in
IPS Empress CAD Multi shade A2 was chosen for the final restoration, which has a built-in shade gradient to match the contralateral central. It took approximately 7 minutes for the restoration to be milled with the inLab MC XL mill (Dentsply Sirona).
The sprue was removed and the restoration was tried in, checking for fit, esthetics, and marginal integrity (Figure 7). At this stage, desired refinements to the crown were done with a fine diamond bur. Once the final shape, emergence, line angles, and texture were satisfactory, the restoration was stained and glazed to match the appearance of the right central.
Cementation
Before cementation, the intaglio of the restoration were etched with 4.5% hydrofluoric acid etch (Ultradent) for 60 seconds, washed, dried, and silaned for 60 seconds. The enamel was selectively etched for 15 seconds, washed, and dried. The NX3 Nexus™ cementation system and OptiBond™ XTR bonding system (Kerr Corporation, www.kerrdental.com) were used to cement the restoration. The crown was carefully placed in the correct orientation. When the cement reached gel stage, the restoration was tack-cured for 2 seconds and the excess cement was removed with an explorer. All surfaces were then cured for 20 seconds each. The proximal surfaces were flossed and any remaining cement was cleaned up. Occlusion was checked and the margins were polished. The paste was rinsed and the immediate postoperative result was evaluated from the facial surface. The all-ceramic crown on the maxillary left central incisor was well received by the patient (Figure 8).
Final Thought
There are several ways to treat discolored teeth, which include neutralizing the stump with an opaque, using low translucency porcelain blocks, using high opaque cements, and increasing the spacer for the restorations. Clinicians must decide to use one or a combination of these techniques to ensure the best final outcome of masking the discolored tooth and creating the correct optical properties that match the contralateral tooth.
Additional Reading
• Ender A, Mehl A. Full arch scans: conventional versus digital impressions—an in-vitro study. Int J Comput Dent. 2011;14 (1):11-21.
• Fasbinder DJ. Clinical performance of chairside CAD/CAM restorations. J Am Dent Assoc. 2006;137 (suppl 1):22S-31sS
• Mehl A, Blanz V, Hickel R. A new mathematical process for the calculation of average forms of teeth. J Prosthet Dent. 2005;94(6):561-566.
• Poticny DJ, Klim J. CAD/CAM in-office technology: innovations after 25 years for predictable, esthetic outcomes. J Am Dent Assoc. 2010;141(suppl 2):5S-9S.
• Fasbinder DJ. Computerized technology for restorative dentistry. Am J Dent. 2013;26(3):115-120.
• Spear F. Restoring discolored endodontically treated teeth. Spear Education website. https://www.speareducation.com/spear-review/2014/02/restoring-discolored-endodontically-treated-teeth-case-1. Accessed March 1, 2016.
• Skramstad M. Choosing the correct block. Cerec doctors.com Magazine. 2014;54-59.
• Skramstad M. Taking anteriors to the next level. Cerecdoctors.com Magazine. 2013;30-31.
For more information, contact:
Pacific Dental Services
714-845-8500
http://pacificdentalservices.com
About the AUthor
Dhaval Patel, DDS
PDS®-Supported Owner Dentist
Roseville, California
