INTRODUCTION
One of the biggest challenges we have as dentists is treating dental alveolar trauma. Not only are the patients often in pain, but they are emotional over the fracture and/or loss of teeth. From a dentist’s perspective, the most difficult part is often treatment planning the best long-term solution for the patient. There is a need to balance the immediate expectations of the patients with what is in his or her best long-term interests.
When evaluating the trauma, the number of teeth involved can play a significant role in how the clinician treatment plans the case. If only one tooth is involved, there are many options available to restore the teeth both functionally and aesthetically. Even if the tooth needs to be extracted, single-tooth implants have a very good chance for success. The difficulty level increases substantially if there is a multi-tooth defect that needs to be restored with implants.
When an extraction is necessary, it is well documented that the loss of the tooth causes resorption of the alveolar ridge. Schropp et al1 reported that the ridge width can be resorbed up to 50% in the first 12 months post tooth extraction, with two-thirds of that happening in the first 3 months. Vertical bone loss of 11% to 22% has also been shown at 6 months following tooth extraction.2 Loss of the periodontal membrane, which is responsible for bone formation, not only causes ridge resorption but also the eventual apical migration of soft tissues. These undesirable consequences can create significant aesthetic challenges when restoring the anterior teeth. For this reason, many techniques have been developed in an attempt to reduce this resorption, such as bone grafting, tissue regeneration, and immediate implant placement. Preservation of bone is of utmost importance in delivering an aesthetic outcome.
The Root Submergence Technique
One method of preserving this bone in multi-site defects is the root submergence technique (RST), often referred to as “root banking.” The RST maintains the periodontal attachment surrounding the root, preventing the resorption of alveolar bone and maintaining the dimension of the ridge and surrounding tissues. The technique was first reported in the literature in 1961 by Bjorn3 as a way to prevent residual ridge resorption in complete denture patients. These long edentulous regions can be difficult with the RST due to the potential of ridge perforation. However, when done under pontics, these complications are minimized because the natural teeth help maintain the bony architecture and the occlusal forces are not directed to the gingiva.4 One of the biggest benefits of the RST is with pontic site development. Salama et al5 reported these advantages to alleviate the difficulties restoring multiple-tooth defects. By maintaining the root, more bone and tissue can be maintained compared to socket preservation procedures following tooth loss. This will allow the dentist to deliver a more aesthetic result to these patients.
CASE REPORT
Diagnosis and Treatment Planning
A 23-year-old, healthy male professional hockey player presented with significant fractures into the pulps on teeth Nos. 9 and 10 (Figure 1). He reported getting hit in the face with a stick during practice. Emergency pulpectomy treatment was performed by another dentist to alleviate pain.
The patient’s initial request was to extract the teeth and restore his smile with a removable provisional appliance. In hockey culture, a “flipper” has been a common treatment and one that is socially accepted. He stated that he did not want to spend a lot of his time, effort, and money doing final restorations on his teeth until he was done playing hockey. He saw the risk of getting hit again as too great to spend much effort or money on the treatment. While his request was understandable, it was explained to him that the biological consequences of removing both teeth at age 23 and potentially waiting more than 10 years to restore those teeth was overwhelmingly not in his best interest. For that reason, a treatment plan needed to be created that restored his smile aesthetically, maintained his bone and soft tissue, and also gave options in the future if the initial treatment failed.
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| Figure 1. The initial fracture of teeth Nos. 9 and 10. | Figure 2. The initial radiograph, showing the extent of the fractures. |
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| Figure 3. Endodontic treatment was completed on both teeth. |
Figure 4. The initial composite buildup on tooth No. 9. |
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| Figure 5. Crown preparation No. 9, and root submergence No. 10. | Figure 6. The root submergence was completed and prepared for imaging. |
A comprehensive exam and radiographs revealed that there was no alveolar damage or fracture in the trauma. It was determined that tooth No. 10 was not restorable (Figure 2). The lingual fracture was at the alveolar crest, and the root length was not sufficient to extrude the tooth the necessary 4.0 mm to establish a proper lingual ferrule. Tooth No. 9 was also fractured extensively down the lingual, but it was likely that it could be restored.
Since the patient was not interested in implants until after his career was over, a treatment plan was created to not only address his immediate concerns but to also provide options for the future. The decision was made for endodontics to be performed on both teeth. Tooth No. 10 would be “banked” with the RST, tooth No. 9 would be built up and prepared for a full-coverage crown, and a cantilever bridge would be made to restore the sites. This was the best possible plan, as it would allow for options in the future. If the root bank was successful and tooth No. 9 failed, a single-tooth implant could be placed in the site and another cantilever bridge could be made. If the root bank failed, the tooth could be extracted and connective-tissue grafting could be done in the site, and another cantilever could then be made off either the natural tooth on No. 9 or an implant on No. 9. By using the RST, both the alveolar bone and surrounding tissues would be maintained, allowing both immediate and future options for an aesthetic prosthesis for this patient. The proposed treatment plan was accepted and informed consent granted.
Clinical Protocol
Endodontics were performed on both teeth Nos. 9 and 10 using the Brasseler EndoSequence Technique (EndoSequence [Brasseler USA]) (Figure 3). Before definitive treatment was done, it was determined that healing needed to happen first. For that reason, tooth No. 9 was built up using composite resin and tooth No. 10 was left alone. This allowed for restoration of some of the aesthetic concerns and guidance for final incisal position. Tooth No. 9 was isolated with a rubber dam (Isodam [HEDY CANADA]) and cleaned with 29-µm aluminum oxide (AquaCare [Veloplex International]). The tooth was etched with 35% phosphoric acid gel (Ultra-Etch [Ultradent Products]), a universal adhesive (Scotchbond Universal [3M]) was applied, and then a composite resin (Tetric EvoCeram [Ivoclar Vivadent]) buildup was completed (Figure 4).
After one month of healing, the patient was ready to start the next phase of treatment. Prior to preparing tooth No. 9, a preoperative (Biocopy) scan was taken using the CEREC Omnicam (Dentsply Sirona) to preserve the shape and incisal position of the buildup. Tooth No. 9 was then prepared for a full-coverage restoration with a 1.0-mm multi-radius “Winter Shoulder” with the CAD/CAM Anterior Preparation System (Brasseler USA). Tooth No. 10 was decoronated to the level of the alveolar crest (Figure 5). After the root was submerged, a very fine layer of glass ionomer (GC Fuji IX GP [GC America]) was placed to protect the root and provide fluoride release.
When performing the RST for pontic site development, a 2.0-mm distance needs to be present from the root to the base of the pontic. To predictably accomplish this, and to maintain isolation and tissue architecture for scanning, Fermit-N (Ivoclar Vivadent) was placed over the banked root (Figure 6). You can measure the depth with a periodontal probe to ensure that you will have proper distance from the pontic to the root surface.
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| Figure 7. The immediate provisional bridge was milled from a PMMA block (Telio CAD [Ivoclar Vivadent]). | Figure 8. A radiograph of root banking and the provisional bridge. |
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| Figure 9. The final, healed provisional bridge at 4 months. | Figure 10. The final bridge design was done with CEREC Software V4.6 (Dentsply Sirona). |
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| Figure 11. The final connector dimension of the lithium disilicate (IPS e.max CAD [Ivoclar Vivadent]) bridge. | Figure 12. The IPS e.max CAD bridge (2 months postoperative). |
Digital imaging and the design of the case were done using the Omnicam and CEREC Software V4.6 (Dentsply Sirona). The design mode was Biogeneric Copy for tooth No. 9 (copied from the original mockup) and Copy and Mirror for tooth No. 10 (copied and mirrored from tooth No. 7). After the design was complete, the cantilever bridge provisional restoration was milled out of a PMMA block (Telio CAD [Ivoclar Vivadent]) and cemented with a resin-reinforced glass ionomer (GC Fuji PLUS [GC America]) (Figures 7 and 8). Permanent cement was chosen because the provisional was going to be worn for 4 months and, in addition, it is very easy to clean up. This will maximize retention and gingival health for the patient.
After 4 months of healing, the patient presented for evaluation and final treatment. The tissue had healed sufficiently around the submerged root, and the surrounding soft-tissue architecture remained in place (Figure 9). Prior to removing the provisional restoration, another Biocopy scan was taken with the CEREC Omnicam to replicate the shape of the provisional to the final restoration as closely as possible. The final design was completed with CEREC Software V4.6 (Figure 10) and prepared to be milled with full-contour lithium disilicate (IPS e.max CAD [Ivoclar Vivadent]). This high-strength all-ceramic was chosen as the final restorative material due to its track record of excellent aesthetics and long-term success. The success of this material application is dependent on proper connector dimensions and a healthy occlusion. The literature has shown that if the connector dimension is at least 12.0 mm2 in the anterior, IPS e.max bridges have a 10-year success rate of 100% after 5 years and 87.9% after 10 years.6 In this case, the connector dimension was designed to 14.92 mm2 (Figure 11).
The final IPS e.max CAD MT cantilever bridge was milled, contoured, and glazed chairside and bonded into place with 35% phosphoric acid gel (Ultra-Etch), a universal adhesive (Adhese [Ivoclar Vivadent]), and light-cure resin (Variolink Esthetic LC Neutral [Ivoclar Vivadent]). A 2-month postoperative visit showed a nice aesthetic result and, more importantly, maintenance of the soft-tissue architecture around the pontic area (Figure 12).
CLOSING COMMENTS
The RST, an often-underutilized procedure, is an excellent way to prevent the biological resorption of alveolar bone. It can help maintain the dimension of the alveolar ridge and surrounding tissues. It is especially effective in association with pontic site development, preventing resorption under the prosthesis, which can create unaesthetic spaces and uneven gingival architecture. Another great benefit of the RST is that it provides future treatment options. Once a tooth is extracted, it is unpredictable (even with socket preservation techniques or immediate implant placement) how the ridge will respond. Banking the root allows for excellent predictability and aesthetic outcomes while also providing a plan for the future if the treatment is not successful in the long term. Some failures will always be a part of dentistry, but minimizing the consequences of those failures is an important key to better patient outcomes and better patient care.
References
- Schropp L, Wenzel A, Kostopoulos L, et al. Bone healing and soft tissue contour changes following single-tooth extraction: a clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent. 2003;23:313-323.
- Tan WL, Wong TL, Wong MC, et al. A systematic review of post-extractional alveolar hard and soft tissue dimensional changes in humans. Clin Oral Implants Res. 2012;23(suppl 5):1-21.
- Bjorn H. Experimental studies on reattachment. Dent Pract. 1961;11:451-454.
- Mittal N, Arora S. Root banking—a case report. Clinical Dentistry. 2009;3:20-24.
- Salama M, Ishikawa T, Salama H, et al. Advantages of the root submergence technique for pontic site development in esthetic implant therapy. Int J Periodontics Restorative Dent. 2007;27:521-527.
- Kern M, Sasse M, Wolfart S. Ten-year outcome of three-unit fixed dental prostheses made from monolithic lithium disilicate ceramic. J Am Dent Assoc. 2012;143:234-240.
Dr. Skramstad received his DDS degree from the University of Minnesota in 2000. He is an internationally recognized educator on technology, implantology, and digital dentistry and has published numerous articles on innovations in these fields. He is currently a resident faculty at Spear Education and cerecdoctors.com in Scottsdale, Ariz, and also maintains a private practice in Orono, Minn. Dr. Skramstad can be reached via email at mike@cerecdoctors.com.
Disclosure: Dr. Skramstad is a resident faculty member at Spear Education and cerecdoctors.com. He has received no compensation for writing this article.
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