Solving a Shade Dilemma
Esthetic challenges of a dark anterior tooth
Thomas E. Dudney, DMD
As the years have passed, dentists have been able to predictably achieve better outcomes with most esthetic procedures. A better understanding of smile-design principles, an increase in using an interdisciplinary team approach, and the availability of improved materials and techniques are some of the factors contributing to the highly successful results. However, one clinical situation that continues to present challenges is dark/discolored anterior teeth.
More Translucent All-Ceramics: Esthetic Challenges and Solutions
It is well understood that the more translucent a restorative material is, the more esthetic it will be, and the more it will be able to mimic the desirable characteristics of natural teeth as long as the color of the tooth is acceptable.1 However, a restorative material with higher translucency will allow a dark underlying color to show through, adversely affecting the final restoration. Conversely, a more opaque restorative material may be better at masking a dark tooth or substrate but may lack the esthetic qualities desired for anterior teeth unless it can be successfully layered with a more translucent ceramic.2,3 Therefore, when faced with the clinical situation of restoring a dark anterior tooth (or teeth), it is desirable to either improve the color of the tooth or to somehow mask it.
Endodontically-treated discolored teeth, tetracycline-stained teeth, metal post-and-cores, and titanium abutments are some examples of clinical situations that present a challenge in achieving acceptable esthetics with translucent restorative materials. Internal and external bleaching, replacing metal posts (when possible) and titanium abutments with dentin-shade materials, and placing tints and composites are some of the options for improving the underlying color. Using layered core restorations (ie, porcelain-fused-to-metal, -gold, or -zirconia) can also be used for masking dark teeth and substructures, sometimes with underlying composites or tints in an attempt to idealize the stump shade. While internal bleaching of endodontically-treated discolored teeth can be successful in improving the color of a dark tooth, the likelihood of relapse could adversely affect the shade of a more translucent all-ceramic restoration. The same would hold true for external bleaching of tetracycline-stained teeth where long-term results are also unpredictable.4 However, if the shade of the prepared tooth (stump) can be improved satisfactorily with opaque composites and tints, it will be more color-stable in the long term and would not require the ceramist to mask it with the restoration. In cases where enough room exists without having to sacrifice healthy tooth structure, the ceramist can successfully mask a dark substrate or discolored tooth with a layered restoration if necessary, as long as the core (coping) material chosen is opaque enough and adequately thick for the task at hand.2,3 It is important that the restorative dentist and the dental laboratory technician fully and properly communicate with one another to determine which option offers the best chance for clinical success.
Diagnosis and Treatment Plan
A 36-year-old man presented with a complaint about a discolored right central incisor (tooth No. 8) (Figure 1 and Figure 2). According to the patient, this tooth had undergone root canal therapy several years prior and had progressively become darker. The clinical examination revealed that the access opening still had a temporary filling in place that, most likely, had contributed to the extreme discoloration over time. In addition, it was noted that the maxillary anterior teeth (teeth Nos. 5 through 12) had significant lingual erosion (Figure 3). Most of the enamel had been eroded from lingual surfaces, resulting in shorter anterior teeth, a slight open bite, and a reverse smile line (Figure 4). The characteristic wear pattern was indicative of intrinsic erosion caused by regurgitated stomach acids. Upon gentle questioning, the patient confirmed the diagnosis but stated that he had not had the problem for several years. (The scope of this article does not allow for a discussion of acid erosion, but suffice it to say that the long-term prognosis of both direct and indirect restorations is good for these types of cases when the source of acid can be prevented or eliminated.) Restorative options were presented to the patient and the agreed upon treatment plan was to prepare for, and place, porcelain veneer crowns on teeth Nos. 5 through 12. These would improve the color match of the central incisor (tooth No. 8) to the other teeth, restore the eroded lingual surfaces of teeth Nos. 5 through 12, and optimize his overall esthetics and function.
The endodontically-treated discolored central incisor presented the biggest esthetic challenge in this case. As stated earlier, there are two options when treating discolored teeth: improve the color or mask it with the restoration. Even though internal bleaching with a walking bleach technique would most likely be successful in improving the color of the tooth in this case, it would also have a high probability for relapse that could result in a darkening or “shade shift” of a more translucent overlying all-ceramic restoration with time. Instead of bleaching, the author elected to improve the underlying color as much as possible with composite resin, and then to mask it with a definitive restoration.
The temporary filling material was removed from tooth No. 8 and the access opening was thoroughly cleansed and filled with a shade A20 nanohybrid composite (Beautifil II, Shofu Dental, www.shofu.com). Teeth Nos. 5 through 12 were prepared with 0.5-mm facial reduction, and little-to-no lingual reduction with a 360° equigingival chamfer margin placed in enamel. Additionally, the facial surface of tooth No. 8 was reduced slightly more and a shade A20 nanohybrid composite (Beautifil II) was bonded on in an attempt to further improve the color (Figure 5). After the preparations were completed, digital photographs were taken with the appropriate foundation shade tabs. Although there was some improvement in the color noted, the preparation shade for tooth No. 8 was ND8, compared to ND1 for the other teeth (Figure 6). In addition to photographs of the prepared teeth, the additional information sent to the lab team included a preoperative series of photographs, a full-arch maxillary polyether impression (Impregum™ Soft, 3M, www.3m.com), a vinyl polysiloxane (VPS) bite registration (Vanilla Bite, DenMat, www.denmat.com), a stick bite, an opposing-arch mandibular model, the length of the centrals, a digital photographic series, an impression of the provisionals (fabricated with Tuff-Temp™ Plus Shade B1, Pulpdent, www.pulpdent.com) (Figure 7), and a written prescription detailing the goals of treatment.