April 1, 2014
by Robert A. Lowe, DDS, FAGD, FICD, FADI, FACD, FIADE, FASDA
With advancing technologies in ceramics, computerized shade matching, and digital photography, matching a single maxillary central incisor with any restorative material is still one of the most difficult clinical challenges that most dentists face. Coupled with increased expectations in this “age of dental aesthetics” and also, with aid from external marketing through media and the internet, patients are less willing to accept a clinical result that is less than perfect (if there is such a thing!) Aesthetic/restorative dentists and dental ceramists can do marvelous things with dental materials today, but at what cost? And also, how many remakes and adjustments does it take to achieve the result? In a “real world” dental practice, many dentists cannot charge the patient enough to attain such a level of perfection … hence the dilemma. The following case documenting the replacement of a missing maxillary central incisor for a young patient is an example of how much work is done on both the dentists’ and ceramists’ side to try and attain perfection.
THE CLINICAL CHALLENGE!
This 16-year-old female patient shown in Figure 1 presented with a missing maxillary right central incisor that was avulsed due to a soccer accident at school. An incisal view of the anterior portion of the maxillary arch (Fig. 2) reveals that a large, concave defect exists with the facial plate in the area of the avulsed tooth missing. Figure 3 is a view of the flipper partial that the patient has been wearing since losing her front tooth. Treatment options including bone and soft tissue grafting with eventual placement of an implant in the tooth number 8 position were discussed with the patient and her parent. At her present age and level of activity in school sports, it was decided to wait until the patient was older before undertaking a treatment process that will take a year or more to stage and complete to a definitive restoration. She is presently wearing a removable “flipper” appliance that is not very aesthetic and the patient is very self-conscious of this fact. So, after reviewing options with her and her mother, an all-ceramic resin bonded bridge was decided upon to be a good intermediate to long-term option to get her to the point where placing an implant would be more feasible. From an aesthetic viewpoint, the lack of facial alveolar bone and depth of the concavity would present a problem in creating a pontic with emergence profile. The lack of marginal gingival would make it a challenge for the ceramist to get the cervical area of the pontic bright enough to match the value of the same areas of the adjacent teeth. It is important to discuss these limitations with the patient so that realistic expectations can be developed. Note … this does not guarantee that the patient will remember these limitations when the definitive restoration is delivered!
FIGURE 3. A facial view of the flipper partial in place. The patient, a young teen, does not have much self-confidence wearing this type of appliance long term. She is too young at this point to consider bone grafting and implant placement.
No tooth preparation was necessary on the lingual surfaces of the abutment teeth since the patient had deep palatal concavities and with 2-3 millimeter overjet, occlusion would not be an issue with the added thickness as long as marginal ridge contact on the maxillary incisors was maintained during protrusive excursions. A shade is taken (Fig. 4) with the Vita 3D Linear Shade Guide (Vident) since the value match is critical. This over-the-patient superior facial angle also greatly reduces or eliminates flash on the facial surfaces so the ceramist can get a more accurate picture of the characterization that exists on the natural abutment teeth. The facial defect allows for placement of the shade tab in an anatomically correct position, which will give a more accurate representation of the shade. When taking pictures of shade tabs next to natural teeth, if the facial surface of the plane is not in the same plane as the subject tooth, it is often hard to get an accurate photograph of the real shade of the tooth. Master impressions of the maxillary and mandibular teeth are made using polyvinyl siloxane impression material (Affinity: Clinical Research Dental). A facebow transfer and centric bite registration are also taken. The patients’ flipper partial is then replaced and the patient is dismissed.
FIGURE 4. A facial view of the flipper partial in place. The patient, a young teen, does not have much self-confidence wearing this type of appliance long term. She is too young at this point to consider bone grafting and implant placement.
Figure 5 shows the definitive restoration prior to cementation. Lithium disilicate (E.max: Ivoclar Vivadent) was chosen because of the added strength as compared to feldspathic or pressed ceramics. When the restoration is held in place to evaluate the shade prior to cementation (Fig. 6), it can be seen that the value is too low and it does not match the adjacent teeth. It is important to note the characterization and surface texture of the abutment teeth create a difficult job for the ceramist to match even if the base shade is correct. A photo is taken of an OM2 shade tab that is slightly higher in value than the original shade chosen (Fig. 7). This oblique facial view shifts the flash of the reflective line angle on the abutment tooth toward the midline and the shade of the tooth in that area, that has little characterization, appears to be a perfect match with the OM2 shade tab. After correction in the lab, the restoration is tried in a second time (Fig. 8). The value is definitely better, but the tooth still looks “dead” with not enough characterization. Using some provisional stains (Fig.
9), (George Taub Minute Stains: George Taub Fusion Company, Jersey City, NJ) the shade tab is color corrected to add cervical warmth and surface hypocalcification. When held up to the incisal edges of the restoration and adjacent maxillary central incisor (Fig. 10), the blend of color looks much better. This color corrected tab can now be sent to the ceramist to aid in the characterization of the ceramic restoration. After yet another lab correction, the restoration still does not have enough “warmth” in the cervical third. After a light application of cervical blend (Taub Minute Stain) to the restoration, the restoration looks warmer and the value is slightly reduced (Fig. 11). Once again, the restoration is sent back to the ceramist for some “make up”.
FIGURE 5. A facial view of the completed “porcelain pontic with wings”. This restoration (E.max: Ivoclar Vivadent) will be bonded to the palatal surfaces of the teeth adjacent to the edentulous space giving the patient a fixed restorative option.
FIGURE 6. The first try in of the resin bonded bridge. The overall value is too low, so after taking digital photos of the bridge tried to place, it is sent back to the dental laboratory for shade adjustment.
FIGURE 8. A view of the second try in. The value is better, but the tooth still has no “vitality”. OM2 looks like a better base shade, but the restoration still lacks internal warmth and surface enamel “white wash”.
FIGURE 11. At the third try in, Taub minute stain (Cervical Blend) is added directly onto the restoration and a photo is taken from an oblique angle to capture the degree of cervical warmth in the restoration and adjacent tooth. The porcelain pontic is still not quite a match to the adjacent central.
With the surface staining completed, the restoration is tried in for a third time. Figure 12 is a photograph of the completed restoration prior to delivery. The first step in the cementation process is to use micro abrasion (Prep Start: Danville Materials) to “pre-etch” the palatal surfaces of the abutment teeth (Fig. 13). Next, using 37 percent phosphoric acid, the same surfaces are etched for 15 seconds, then thoroughly rinsed and air-dried (Fig. 14). The bonding agent is placed (Fig. 15) (All Bond Universal: Bisco) and the restoration is cemented using resin cement (Duo Link: Bisco). The cemented restoration is shown in Figure 16. Note that the value of the restoration is still slightly too bright. Prior to cementation, it was decided that with some chairside whitening (Zoom! WhiteSpeed Chairside Whitening: Philips) after delivery, the final result would be acceptable to the patient avoiding yet another trip to the lab (Fig. 17). Zoom WhiteSpeed light and whitening gel (Philips) is used for 3, fifteen-minute sessions on medium setting to decrease the chance for postoperative tooth sensitivity. The shade was evaluated after each session prior to proceeding (Fig. 8). Figures 19 and 20 show the postoperative result after final delivery of the restoration and Zoom Whitening. The patient was pleased with the final result and chairside whitening helped with the final blending of the ceramic restoration.
FIGURE 12. A view of the restoration prior to the fourth try in after the addition of more internal “warmth”. Although the overall value was slightly high, it was determined rather than try to lower the value slightly and risk starting again from scratch, chairside whitening would be used after cementation to slightly raise the value of the natural teeth to match the porcelain.
FIGURE 17. Chairside whitening gel is applied to the adjacent teeth after the proper isolation is in place. The patient goes through three, 20-minute sessions at a medium setting on the WhiteSpeed lamp (Philips) to limit the chance of postoperative sensitivity.
FIGURE 20 . A smile view of the completed restoration. When compared to Figure 3, the ceramic resin bonded bridge is a much better aesthetic match than the flipper partial. But even more important at this time in her life, the ceramic bonded restoration provides her with the necessary self confidence at this formative time in her life.
Many clinicians will agree that matching the shade and characterization of a single maxillary central incisor is the hardest clinical task we perform. A resin bonded bridge with a single pontic, which in some clinical cases can be considered a conservative option to a three-unit bridge or implant crown, may be even harder to match because the entire tooth is missing and also because of the lack of marginal bone and soft tissue around the pontic. In this case, the facial plate defect was indented so far palatally that it was hard to deal with the emergence profile of the restoration and the lack of root structure underneath the soft tissue envelope that could reflect light and brighten up the gingival area. After several attempts to match the existing teeth, the last attempt was so close that chairside tooth whitening was chosen to raise the value of the remaining teeth to better match the restoration. Tooth whitening was not done prior to the fabrication of the restoration because at that time the tooth color was considered to be satisfactory to the patient. The fact is that regardless of whether the whitening is done before restoration fabrication or after, as in this case, patients with teeth that have a lot of characterization may benefit from chairside tooth whitening in two ways; 1) reducing the visual effect of internal characterization and, 2) making shade matching easier for complex aesthetic matches. This restoration will serve the patient well until she decides later in her twenties, if she wants to pursue bone grafting and implant restoration. OH
Dr. Robert A. Lowe maintains a private practice in Charlotte, North Carolina. He can be reached at 704-450-3321 or at firstname.lastname@example.org. Oral Health welcomes this original article.