Root Submergence Technique

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Root Submergence Technique - A Case Report Lanka Mahesh, Gregori M. Kurtzman, Praful Bali and Sagrika Shukla

Dental implants along with providing health and function to the patient also provide esthetics. However, implants will never surpass the natural tooth’s ability to preserve the surrounding bone and soft tissue height. Root submergence technique (RST) is one such procedure which provides maximum preservation of the surrounding alveolar bone and soft tissue. Introduction Over the past 35 years, field of implantology has proven to become a predictable method in restoring functions in the oral cavity1,2. And as the awareness of this treatment has increased, restoration of missing anterior teeth with implants has become a preferred treatment modality, despite the fact that it remains one of the most aesthetically difficult and challenging of all implant restorations3. The challenge in placement of implants in esthetic zone lies in establishing soft tissue contours and maintaining aesthetics along with functional stability. Soon after tooth extraction a cascade of healing process starts which results in 25% bone resorption4,5. This healing process hampers implant placement and esthetics due to hard and soft tissue loss6. For the very same reason, several techniques have been

Figure 1: Panoramic radiograph pretreatment following failure of a natural tooth fixed bridge in the left quadrant.

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developed such as the socket seal surgery (SSS), scalloped implant7, platform switching8 and the most common of all, immediate implant placement in an attempt to control alveolar bone resorption, preserve crestal bone height around implants and maintain soft tissues in esthetic zone9. In the process of immediate placement it is difficult to achieve soft tissue coverage especially in patients having thin gingival biotype10. Periosteal-releasing incisions, as well as palatal rotational flaps have been introduced for complete flap closure and improve soft tissue countours, however these procedures may alter the continuity of the keratinized tissue band, further if the flap is closed under tension, it may increase the chance of eventual bone graft, membrane and bone loss11. To overcome these clinical difficulties a technique for developing keratinized tissue on top of the

Figure 2: Clinical view of the arch following failure of the fixed bridge in the left quadrant demonstrating the residual root at the left central incisor.

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socket orifice was introduced in11 second half of the 1960s, known as the Root Submerged Technique (RST)12, to prevent alveolar bone resorption after extraction of teeth, where the crown was resected and was covered with a buccal or buccolingual flap, submerging the root of the patient12. In most cases, dental pulps were vitally preserved or root canal treatments were performed before or during the procedure9. This method entails grinding the failing tooth 2 mm below the free gingival margin to make it level with the alveolar crest and then leaving it in the socket for 3-4 weeks so that surrounding tissue can proliferate over the remaining root11. Howell12 observered that alveolar bone under complete dentures for more than 10 years did not resorb when treated with the help of endodontically treated submerged roots. In 1975, Guyer13 submerged human vital roots for the first time and reported that the two roots displayed radiographically normal conditions and the alveolar ridge did not resorb clinically for 27 months. In 1976, Plata et al14 performed a 12-week histologic evaluation of 12 vital submerged roots that were cut at 2 mm below the bone edge. They reported that eight of the roots had complete bone coverage on the cut surfaces, and all pulps were vitally retained.

Material and Method: A 60 year old lady reported to the dental office with a desire to replace her missing upper left posterior teeth. She had undergone implant therapy on the upper right side with a tooth and implant supported prosthesis 9 prior which was in good clinical and radiographic appearance, except for a chipped ceramic crown in relation to upper right 1st molar. (Figure 1) On intraoral examination a fractured central incisor at the gingival margin in the upper left quadrant, with a thick

Figure 3: The residual root at the left central has been reduced to level with the crestal bone, posterior failed tooth extracted and implants placed in the quadrant.

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gingival bio type with excessive tissue reducing the crown height space (CHS), in the posterior quadrant (Figure 2) The options were to place an immediate implant in relation to the left central incisor, canine and 1st molar. A gingivectomy would also be needed to remove the excess gingival tissue and create more interarch space. The second treatment option presented to the patient was to submerge the tooth root of the left central incisor and implant placement in the canine, 2nd premolar and 1st molar sites. Implant placement would be slightly subcrestal to allow a screw retained prosthesis at the restoration phase. The patient selected the second treatment option and Alpha-Bio Tec (Tel Aviv, Israel ) implants were selected for the case with dimensions of 3.75 x11.5 mm to fit the available bone at the sites seelcted. The residual tooth in the central incisor location was reduced with a large round bur until the root was 2 mm sub crestal to facilitate soft tissue closure. The posterior root was extracted and osteotomies created as planned and the implants were inserted with recorded insertion torque of 35 Ncm or greater. A resorbable suture was placed to achieve soft tissue closure at the residual root site. (Figure 3 and 4) Healing abutments were placed into the three implants that were level with the superior aspect of the soft tissue crest. (Figure 5) Following an uneventful healing period of 4 months the healing abutments were removed and open tray impression heads were inserted. (Figure 6) A full arch stock tray was modified to allow the long impression pins to exit the tray and an impression was taken with a heavy body VPS impression material (3M ESPE, St. Paul, MN), a counter impression wasd recorded and the healing abutments reinserted. (Figure 7) The impressions were sent to the lab and models created and mounted. (Figure 8 and 9) Soft tissue was noted to reduce the available interarch space

Figure 4: Upper left quadrant with suture at the retained residual root to get soft tissue closure and implants placed into the quadrant.

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Figure 5: Occlusal view with suture at the anterior maintained residual root and healing abutments at the implants that have been placed in this quadrant.

between the posterior two implants and would require reduction at the metal frame try-in. A screw retained metal framework was created with a cantilever over the anterior buried residual root. (Figure 10) The patient returned and local anesthetic was administered where the crestal soft tissue would need to be reduced and tissue was removed using a scalpel. The healing abutments were removed. The screw retained metal fixed prosthesis frame was inserted to verify passive fit. (Figure 11) Fit was confirmed clinically and verified with intraoral radiographs. An interarch record was recorded (Imprint Bite, 3m ESPE) to allow the laboratory to place the ceramic and the prosthesis framework was removed. (Figure 12) Healing abutments were reinserted and the prosthesis returned to the lab for completion. Ceramic was applied to the fixed prosthesis framework and returned for insertion. The final prosthesis was inserted and the abutment screws were torqued to 40Ncm with a torque wrench. (Figure 13 and 14)

Results: Postoperative healing was uneventful. Patient did not report any pain or swelling. She was instructed in proper oral hygiene home care. The patient was satisfied with the final esthetics and occlusion was checked for any interferences. (Figure 15) The patient was followed on recall and reported no issues during a 3 year period. A panoramic radiograph was taken at 3 years post case completion demonstrating stable bone with no crestal loss at the implants or apical pathology at the residual root. (Figure 16)

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Figure 6: Following 4 months of healing to allow integration healing abutments were removed and open tray impression heads were placed for an impression.

Discussion: Esthetic implant treatment is more difficult for multipletooth defect sites than for single-tooth defects, due to absence of an ideal soft tissue frame with intact interdental papillae9. This problem is further accentuated by placement of dental implants in thin gingival biotype because it is difficult to achieve symmetrical soft tissue contours. Recession and bone resorbtion leave a flat profile between the roots with marginal exposure of the restoration and subsequent loss of interproximal papilla15. For such patients socket seal surgery or flapless implant placement should be considered, provided labial plate is intact. However, marginal ridge resorption and graft related complications make it difficult for the soft tissue profile to emerge around dental implants16. The gingival tissues around dental implant component should be enhanced, influenced and developed to acquire the same dimensions and configurations of the original tissues around natural dentition10. In the process of attaining such esthetic considerations, sufficient keratinized mucosa should be present around dental implants for maintaining and stabilizing peri-implant tissue margins11. By grinding roots and making soft tissue proliferate over it, sufficient keratinized tissue is made available simulating natural dentition, since the presence of root holds the bone and the soft tissue component in place and removes the complications related with the bone resorption. Salama et al17 suggested that from a prosthetic viewpoint, mixed environment of natural teeth and implants is difficult to control, and establishment of exact occlusion which remains stable becomes challenging. In such cases, sometimes the SPECTRUM Implants — Vol. 7 No. 1 — Spring 2016

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Figure 7: Open tray impression with impression heads embedded into the VPS material.

Figure 8: Articulated models demonstrating limited interarch clearance with arrow indicating where soft tissue will require trimming to provide better clearance for the fixed prosthetic.

Figure 10: Screw retained metal framework for the PFM fixed prosthesis with cantilever over the submerged residual root.

Figure 11: Try-in of the metal screw retained frame to verify fit.

remaining tooth is replaced by a pontic. Thus he stated that considering the predictability and ability of RST to maintain and preserve the vertical height of alveolar bone, extracting the remaining tooth should not be considered as the only option. In a study by Bowers et al18 RST of vital teeth with infrabony defects in nine patients was performed, where 30 regions with bone graft (demineralized freeze-dried bone allograft) and 13 regions without bone graft were submerged. A histologic evaluation was performed on all 43 regions after 6 months which showed that epithelial exclusion with bone grafts and root submergence could treat infrabony defects with a higher level of predictability.

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Figure 9: Soft tissue master cast after alteration of the cast where gingival tissue will require alteration intraorally.

Harper19 submerged an endodontically treated root in the anterior maxilla and successfully followed up, over a 6-year period, a combined “submerged root/pontic” site. Salama et al9 postulated that the RST should be recognized as a very effective technique for maximum tissue preservation and esthetics for pontic sites in the esthetic zone. Advantages of this technique include complete primary coverage of the implant at stage-one surgery, reduced treatment time and decreased cost to the patient. Disadvantage includes complications such as gingival tissue perforation, cyst formation, necrotic and infected dental pulps, however these complications have seldom been reported9.

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Figure 12: VPS bite with the screw retained metal fixed prosthesis framework intraorally.

Conclusion: The field of implant dentistry and esthetics is always improving with the advent of new materials which give an illusion of natural teeth; however, implants will never surpass the natural tooth’s ability to preserve the surrounding bone and soft tissue height9. Thus there is always a need of

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Figure 13: Finished PFM screw retained fixed prosthesis inserted intraorally.

improvising; RST is one such technique which not only eliminates the risk of caries and periodontitis, but more important, the retention of a natural tooth root allows for maximum preservation of the surrounding alveolar bone and soft tissues.

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Figure 14: Occlusal view of the screw retained fixed prosthesis.

Figure 15: Facial view of the finished screw retained fixed PFM prosthesis in the upper left quadrant demonstrating the lip line.

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7. 8.

9.

Figure 16: Panoramic radiograph at 3 years post completion of the completed screw retained fixed prosthesis in the upper left quadrant.

10. 11. 12.

The RST was introduced to preserve the alveolar ridge; later it was used to prevent down growth of epithelium during the regeneration of periodontal tissues9. Today in spite of many advancements in our field, scope of RST is limited, however every effort should be made to make RST a more common practice9. ■

References 1.

2. 3. 4. 5.

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