Part 1: The Single Central Dilemma
Overcoming variables that challenge successful single central restorations
For many in dentistry, the restoration of the maxillary single central is probably the most dreaded procedure and poses a challenge for the restorative team. The loss of or damage to a central incisor is usually attributed to trauma, and with the trauma come many variables that need to be taken into consideration when restoring the patient’s smile. The damage associated with the incurred trauma can range from complete loss of the tooth or a large fracture, to tissue loss and extreme discoloration of the underlying abutment. Trying to meticulously color match a single central crown is difficult enough in a perfect nontraumatized intraoral environment; however, when trauma is the culprit, the job of restorative team becomes even more challenging and every detail must be taken into consideration prior to treatment. The goal of discussing the following cases in this two-part series is to show scenarios associated with damage to a single central incisor and the solutions the restorative team devised to mimic nature.
Shade and Gingival Challenges
Rarely is the first attempt at matching nature a success. A high percentage of single central crowns are not permanently cemented at the initial appointment. Most often that appointment is used as an opportunity to try-in the first attempt at restoring the natural form and shade before the final shade attempt (Figure 1). This try-in will yield much more information than the traditional shade guide image. It can provide information on exact details the technician needs to alter the final crown, whether it be shade (darker or lighter), texture, or form. This is the surest way to achieving a successful restoration. When the restorative team is working in a nontraumatized environment with the tooth and tissue contours and surrounding dentition still intact, it is merely a matter of matching the color, value, texture, and form to surrounding natural dentition (Figure 2 and Figure 3). The restoration should be observed at different angles and under various lighting environments to check the accuracy. Figure 4 and Figure 5 show the restoration under polarized lighting to assess shade and in black and white to examine the value.
The dental team does not typically address tissue damage. Figure 6 shows a patient with a previous restoration who attempted to solve his dental trauma, but he had an unsatisfactory result. On examining the restoration more closely, it was obvious that the tissue heights of the two centrals were different, which made the restoration appear to have a completely different form. Figure 7 shows the removal of the previous restoration and the obvious discrepancy between tissue heights. Prior to the surgical procedure to achieve the desired tissue height, the tissue was marked to visualize the ideal outcome (Figure 8). Once the tissue was trimmed to the desired height, a custom temporary abutment was placed to preserve the new tissue contour (Figure 9). A PMMA temporary was then placed on the temporary abutment (Figure 10). At recall the dental team can examine the progress of the tissue recontouring; it is important to check with the patient on any esthetic concerns he or she may have before moving to the final ceramic restoration. The final ceramic crown was placed and checked meticulously under polarized light conditions to determine if any color corrections would need to be applied (Figure 11). Once the crown was cemented in place, it was easy to see that the driving variable in the success of this case treatment was the recontouring of the gingiva to allow for adequate form of the tooth being restored (Figure 12). The restoration was a harmonious match under many lighting conditions, particularly fluorescent, due to the high-fluorescent ceramic (GC Initial™ Zr-FS, gcamerica.com) that was used to layer the restoration (Figure 13). Using the same fluorescent ceramic on the shoulder of the abutment also yielded a nice tissue response to light (Figure 14).
Tooth Form Challenge
In many situations tooth form can also become an issue for the success of a case. In implant cases in which a tooth has been knocked out, the surrounding dentition often shifts toward the open space, leaving less room for the final restoration. Figure 15 shows a patient temporized and ready for a final restoration to be fabricated. The surgical team members did a great job preserving the tissue; however, they left the restoring dentist with unequal proportions on the central incisors. The shade was then taken for the ceramic layering under polarized light (Figure 16). The restorative team then digitally mocked up an exact copy of the natural incisor for the patient to understand that in order to have intraoral harmony, a slight overlap may be required in the final restoration. The final restoration was then taken to completion and tried in. At the try-in appointment the patient was not satisfied with the black triangle at the cervical. The dentist used temporary cement (NoGenol™, GC America) to monitor the tissue response. At recall the tissue filled the space nicely, and the crown could be cemented permanently (Figure 17). The seated restoration was checked under polarized light (Figure 18), regular light, and fluorescent light (Figure 19) to determine if it blended successfully with adjacent dentition (Figure 20).
Stump Color Challenge
In veneering single central incisors, it is of the utmost importance to understand the underlying color of the restoration and how it can either help or hurt the final restoration. Figure 21 shows a patient with an old composite restoration. After the composite was removed, the dentist used a conservative facial preparation, which yielded a nice value match that could be used in the final color outcome of the veneer. The only consideration the technician had to take into account was blocking out the demarcation line from preparation to veneer (Figure 22). At shade selection under polarized lighting, the desired ceramic was chosen using visual_eyes (Emulation, emulation.gr) and fluoro_eyes (Emulation) (Figure 23 and Figure 24). visual_eyes allows the technician to see the color of wet unfired ceramic on sight to best choose the proper colors for layering, and fluoro_eyes enables the dentist to choose the right composite to use when bonding the veneer. An image of the final veneer shows how the feldspathic veneer was layered to take advantage of the underlying tooth color while blocking out the demarcation line. The final restoration under standard lighting, polarized light, and bounced light demonstrates a successful outcome (Figure 25 and Figure 26). The restoration can then be observed from different angles to check the details of the veneer in the intraoral environment. The final veneer can also be checked under fluorescent light to observe that the restoration exhibits the same fluorescent properties as the surrounding natural dentition (Figure 27). Looking at the before and after, it is clear that the underlying tooth color helped the restorative team achieve a successful outcome with minimal removal of natural dentition (Figure 28).
Part 2 of this series will appear in the next issue of Inside Dental Technology.
Dentistry was performed by Dr. Barry Polansky, Dr. Mike Monokian, Dr. Devon Conklin, and Dr. Ben Ross.