ROOT SUBMERGENCE TECHNIQUE (RST)

This article covers an alternative technique called root submergence whereby the crown is resected and covered with a buccal or buccolingual flap. Initially introduced to prevent alveolar resorption under complete dentures.

The term RST was proposed by Howell in 1970 and entails grinding the tooth level or below the alveolar crest with healed soft tissue coverage the result.  When submerged in this way, studies (on non-infected vital or endodontically treated roots) show the root maintains periodontal attachment thus preventing alveolar resorption associated with extraction [1,2].

The importance of a harmonious soft tissue profile with preservation or regeneration of the underlying alveolar bone is critical for long-term successful implant outcomes. Our other articles discuss ways to regenerate bone using a minimally invasive approach and methods for preserving the ridge with bone grafts at the time of extraction.

ROOT SUBMERGENCE TECHNIQUE AND MULTIPLE IMPLANT CASES Successful outcomes were reported by Salama et al [3]. and more recently by Mahesh and Bhasin in a case series with 7 years of follow-up of 32 vital and non-vital teeth in conjunction with the placement of Bioner TopDM Dental Implants

RST IN CONJUNCTION WITH TOP DM IMPLANT FROM BIONER (Barcelona, Spain)

The authors chose TopDM due to its unique design which lends itself to placement in areas of low bone density like the maxilla.

The authors cited the expanding cone-shaped core, the dual-pitched thread which increases in diameter from apical to coronal as key selection factors. 

TopDM shows quicker healing times and reduced time to loading due to the unique double acid etching treatment favoured by the Bioner company.   

SURGICAL TECHNIQUE

The tooth was first decoronated to the gingival level, with a tapered diamond. Then a diamond bur was used to trim a 2 mm sub crestal so as to facilitate soft tissue closure. Special care is taken to protect the gingiva at all times to avoid soft tissue perforations. The site can be covered with an Ora Aid self-adhesive dressing for protection.

Healing abutments were placed prior to closure with impressions at 10 days and a fixed prosthesis planned with the submerged roots. 

All roots were completely covered by soft tissue, after treatment and showed no change at the 7-year follow-up evaluation.

POST-OPERATIVE HEALING

The submerged roots helped in attaining an excellent soft tissue profile around the pontic site under the definitive metal-ceramic restoration, supported by TopDM implants on either side.

Histologic and radiographic studies on RST, reported positive results and concluded that the root submergence technique should be considered as an alternative to the extraction of key teeth to preserve alveolar bone. [5]

RISK FACTORS

RST should be avoided in teeth with large periapical infections, vertical fractures, high mobility and in those with internal or external resorption.  Risk factors include exposure of the coronal root through the tissue increasing the periodontal infection risk if left untreated.  In rare cases, root migration can occur.  The authors considered that all such complications ‘can be prevented with a thorough examination, case selection, and correct procedural steps, such as keeping the root completely submerged with all edges removed’.

CONCLUSION

RST supports the ridge tissues between multiple implants and maintains the alveolar ridge framework well over a 7-year period. The technique saves time and supports excellent long-term aesthetics in multiple implant cases.

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1. Casey DM and Lauciello FR. “A review of the submerged-root concept”. Journal of Prosthetic Dentistry 43 (1980): 128-132.
2. O’Neal RB., et al. “Submergence of roots for alveolar bone preservation. I. Endodontically treated roots”. Oral Surgery, Oral Medicine, Oral Pathology 45 (1978): 803-810.
3. Salama M., et al. “Advantages of root submergence technique for pontic site development in aesthetic implant therapy”. The International Journal of Periodontics and Restorative Dentistry 27.6 (2007): 521-527.
4. Mahesh and Bhasin. Root Submergence Technique, A Case Series with Follow-Up up to Seven Years. Acta Scientific Dental Sciences (ISSN: 2581-4893) Volume 6 Issue 9 September 2022.  
5. O’Neal RB., et al. “Submergence of roots for alveolar bone preservation. I. Endodontically treated roots”. Oral Surgery, Oral Medicine, Oral Pathology 45 (1978): 803-810.