Treatment Planning, Selection of Restorative Materials and Techniques of Restoration in Subgingivally Extended Lesions/Defects

CONTENTS

1. Introduction and Definition
2. Etiology / Causes of Subgingival Extension of a Lesion
3. Clinical Problems Created by Subgingival Margins
4. Diagnosis and Pre-operative Assessment
5. Treatment Planning — Objectives and Decision Tree
6. Techniques of Management
   • 6.1 Non-surgical / Isolation-based approach
   • 6.2 Soft tissue management (gingival displacement)
   • 6.3 Deep Margin Elevation (Cervical Margin Relocation)
   • 6.4 Surgical Crown Lengthening
   • 6.5 Orthodontic Extrusion
7. Selection of Restorative Materials
8. Step-by-Step Restorative Protocol
9. Complications and Their Management
10. Recent Advances and Evidence-Based Update
11. Conclusion
12. References

1. INTRODUCTION AND DEFINITION

2. ETIOLOGY / CAUSES

• Proximal (interproximal) caries progressing cervically below the contact point
• Cervical abrasion, erosion, abfraction extending subgingivally
• Fracture of a cusp/wall extending below the gingiva
• Failed/leaking old restorations with recurrent caries at the gingival floor
• Root caries in periodontally compromised or geriatric patients
• Need for ferrule/retention in endodontically treated teeth requiring subgingival crown margins
• External cervical resorption

3. CLINICAL PROBLEMS CREATED

4. DIAGNOSIS AND PRE-OPERATIVE ASSESSMENT

1. Clinical examination — depth of margin relative to gingival crest, sounding under LA to locate the crestal bone and measure biologic width.
2. Radiographic assessment (IOPA/bitewing, and CBCT if extensive) to gauge proximity to crest, root morphology, furcation risk.
3. Pulpal and periodontal status — vitality tests, pocket depth, attachment level, plaque/bleeding index.
4. Assessment of remaining tooth structure, occlusal load, and whether the tooth will be direct-restored or need an indirect (inlay/onlay/crown) restoration.
5. Patient factors — oral hygiene motivation, caries risk, esthetic zone or not, systemic contraindications to periodontal surgery.

5. TREATMENT PLANNING — OBJECTIVES AND DECISION TREE

• Achieve a margin that can be predictably isolated, finished, and polished
• Preserve/re-establish biologic width (≥2-3 mm from restoration margin to bone crest)
• Conserve tooth structure and vitality
• Provide a durable, well-sealed, esthetic and biocompatible restoration
• Prevent iatrogenic periodontal damage

1. Can the margin be reliably isolated with rubber dam + wedge/matrix/retraction cord alone? → Direct restoration with isolation aids.
2. Is isolation possible but the margin still too deep/subgingival for a good indirect impression or connective-tissue-space is not invaded? → Deep Margin Elevation (DME)/Cervical Margin Relocation, then proceed with direct or indirect restoration.
3. Is there true biologic width violation, inadequate ferrule, or isolation impossible even after DME? → Surgical crown lengthening (osseous resection ± apically repositioned flap) or orthodontic extrusion (especially single teeth, esthetic zone, minimal bone loss) followed by restoration after healing (6-12 weeks for soft tissue, longer for bone remodeling).
4. Non-restorable/poor prognosis → extraction and prosthetic replacement.

6. TECHNIQUES OF MANAGEMENT

6.1 Isolation-based (first-line) approach

• Rubber dam with a retentive/winged clamp seated apical to the margin — gold standard for moisture control.
• Wedges (anatomic, light-reflecting) placed firmly to depress the rubber dam/gingival tissue and provide separation.
• Teflon (PTFE) tape or copper band adapted circumferentially to aid isolation of very deep boxes.

6.2 Soft Tissue Management (Gingival Displacement)

• Retraction cord (plain or with astringent, e.g., aluminium chloride) packed for a few minutes.
• Electrosurgery or diode laser gingivectomy/troughing to remove a small collar of tissue when access is limited by hyperplastic or excess gingiva — provides hemostasis and a dry field simultaneously.
• Gingivectomy/gingivoplasty when a permanent minor recontouring is acceptable and there is adequate biologic width (no bone involvement).

6.3 Deep Margin Elevation (DME) / Cervical Margin Relocation (CMR)

1. Rubber dam isolation, caries excavation, and cavity disinfection.
2. Adhesive protocol (selective/total-etch + bonding agent) applied to the deep dentin margin only.
3. A thin sectional matrix or Teflon strip adapted to the deep margin; a flowable or packable composite is placed incrementally (≤2 mm increments) and light-cured to relocate the margin coronally (typically 2-4 mm elevation).
4. Matrix removed, elevated margin finished/checked for cervical seal (no overhang, positive marginal seal).
5. A second matrix band/ring is then placed for the definitive restoration (direct composite) or the tooth is prepared/impressed for an indirect restoration with the new, accessible supragingival margin.

6.4 Surgical Crown Lengthening (SCL)

• Indicated when isolation is impossible, biologic width is violated, or ferrule is inadequate.
• Involves flap reflection with osteotomy/osteoplasty to re-establish 2-3 mm of sound tooth structure coronal to bone crest, followed by 6-8 weeks (soft tissue) to 3-6 months (if osseous recontouring near esthetic zone) healing before final restoration.
• Risks: furcation exposure, altered crown : root ratio, esthetic gingival asymmetry, root sensitivity.

6.5 Orthodontic Extrusion

• Slow (or, less commonly, rapid) extrusive orthodontic force on the affected tooth to bring the subgingival defect coronally along with the attachment apparatus.
• Useful in single-rooted anterior teeth, minimizes bone removal, but requires longer treatment time (weeks to months) and orthodontic co-ordination; often combined with fiberotomy to prevent coronal migration of the crestal bone.

7. SELECTION OF RESTORATIVE MATERIALS

• Moisture control feasibility dictates material choice — the less predictable the isolation, the more forgiving (GIC/RMGIC) the material should be.
• The sandwich/laminate technique (GIC or RMGIC base + composite overlay) is widely favored for deep subgingival boxes: the GIC seals the deepest, most contamination-prone floor while composite provides strength and esthetics coronally.
• For indirect restorations (onlay/CAD-CAM), DME with a bonded composite base is now standard prior to impression/scanning, converting an inaccessible subgingival margin into an accessible supragingival one.
• Bulk-fill flowables are preferred as the DME elevation material because of their flow into undercuts and lower shrinkage stress.

8. STEP-BY-STEP RESTORATIVE PROTOCOL (Typical Class II subgingival box)

1. Local anesthesia and rubber dam isolation (clamp seated beyond the deepest margin).
2. Gingival troughing/retraction cord or electrosurgical recontouring if the dam clamp alone cannot expose the margin.
3. Complete caries excavation; assess residual margin depth relative to gingival crest/bone.
4. If margin is still subgingival but isolable and connective tissue is not invaded → perform DME: selective/total-etch, bonding agent, Teflon strip/sectional matrix, incremental flowable/packable composite to elevate margin 2-4 mm.
5. Re-evaluate: if margin now accessible and supra/equigingival → place sectional matrix + ring + wedge, complete adhesive protocol, and restore in composite increments (≤2 mm) with proper contact/contour, cure each increment.
6. Finish and polish; check proximal contact, marginal integrity, occlusion (articulating paper), and floss contact.
7. If margin still not manageable after DME/troughing → refer for surgical crown lengthening or orthodontic extrusion, then restore after healing.
8. Post-operative instructions and periodic recall to monitor periodontal health at the restored margin.

9. COMPLICATIONS AND THEIR MANAGEMENT

10. RECENT ADVANCES AND EVIDENCE-BASED UPDATE

• Deep Margin Elevation (DME) has largely replaced routine surgical crown lengthening for isolated, non-attachment-invading subgingival proximal defects, driven by adhesive dentistry and the decline of amalgam use.
• Meta-analytic evidence (Sadeghnezhad et al. 2024, PMID 38907025) supports DME's benefit in reducing microleakage at elevated margins.
• Multiple 2023-2024 systematic reviews (PMID 38003997, 38978303, 36446028) conclude DME does not significantly worsen periodontal or pulpal parameters in the short-to-medium term when the connective tissue attachment is not invaded and isolation is strict — but caution that evidence is largely from small clinical trials/in-vitro studies, so long-term prospective data are still awaited.
• Bioactive/bulk-fill materials and universal adhesives with improved gingival-margin adaptation (dentin etching protocols) are active areas of ongoing research to further reduce technique sensitivity in these defects.
• CAD/CAM inlay/onlay workflows increasingly incorporate DME as a pre-restorative step to allow intraoral scanning at an accessible margin instead of a subgingival one.

11. CONCLUSION

12. REFERENCES

1. Sadeghnezhad P, Sarraf Shirazi A, Borouziniat A, Majidinia S, Soltaninezhad P, Nejat AH. Enhancing subgingival margin restoration: a comprehensive review and meta-analysis of deep margin elevation's impact on microleakage. Evidence-Based Dentistry. 2024. PMID: 38907025.
2. Srirama S, Jain S, Arul B. Effect of Deep Margin Elevation on the Pulpal and Periodontal Health of Teeth: A Systematic Review. Operative Dentistry. 2024. PMID: 38978303.
3. Felemban MF, Khattak O, Alsharari T, et al. Relationship between Deep Marginal Elevation and Periodontal Parameters: A Systematic Review. Medicina (Kaunas). 2023. PMID: 38003997.
4. Chun EP, de Andrade GS, Grassi EDA, et al. Impact of Deep Margin Elevation Procedures Upon Periodontal Parameters: A Systematic Review. European Journal of Prosthodontics and Restorative Dentistry. 2023. PMID: 36446028.
5. Taylor A, Burns L. Deep margin elevation in restorative dentistry: A scoping review. Journal of Dentistry. 2024. (ScienceDirect, S0300571224002355).
6. Standard operative dentistry principles on isolation, matrix systems, gingival retraction, crown lengthening, and orthodontic extrusion (course-standard operative/periodontics textbooks — e.g., Sturdevant's Art and Science of Operative Dentistry; Carranza's Clinical Periodontology) — cited from general professional knowledge as the departmental medical-textbook library used for this response does not include a dedicated dentistry title.