Deep margin elevation: managing deep margins on non-vital teeth

Clinical challenges of subgingival margins: the case of the 47

The restoration of endodontically treated teeth with deep subgingival proximal margins represents a major technical challenge. This case report documents the situation of a 38-year-old female patient whose mandibular second molar (tooth 47) presented repeated failures of indirect restoration. After the removal of recurrent caries, the practitioner identified a deep occluso-proximal defect extending below the cemento-enamel junction. In this area, the absence of enamel and the proximity of the periodontium make rubber dam isolation, fluid control, and the management of adhesive cement excess particularly complex.

The precise objective of this clinical case is to describe the implementation of Deep Margin Elevation (DME) as a conservative alternative to invasive methods such as surgical crown lengthening or orthodontic extrusion. The protocol aims to reposition the cervical margin supragingivally using a bulk-fill composite resin. The hypothesis tested here is that DME allows for an isolated and dry operative field, necessary for the reliability of the digital impression and the final bonding of a lithium disilicate overlay, while preserving the supracrestal tissue attachment of tooth 47.

Methodology

This case report details the clinical management of a 38-year-old female patient presenting a right mandibular second molar (tooth 47). The tooth, previously endodontically treated, showed repetitive failures of partial indirect restorations due to deep subgingival margins.

The therapeutic protocol followed these steps:

• Occlusal preparation: Selective ameloplasty of the extruded antagonist tooth to restore a harmonious occlusal plane.
• Excision and isolation: Removal of carious tissues using low-speed carbide burs under rubber dam. Isolation of the mesial proximal box was optimized using a sectional metal matrix and the insertion of polytetrafluoroethylene (PTFE) tape to ensure cervical sealing.
• Adhesive protocol: Selective dentin etching with phosphoric acid (37.5%) limited to 5 seconds to prevent over-etching of the dentin/cementum. Active application of a 10-MDP-enriched universal adhesive for 20 seconds, followed by light-curing for 20 seconds.
• Deep Margin Elevation (DME): Use of a bulk-fill composite resin to reposition the cervical margin to a supra-gingival position.

The initial evaluation was based on a clinical examination and radiographic analysis confirming the absence of periapical lesion and the compliance of the existing root canal filling.

Deep Margin Elevation (DME) procedure results

The study of this clinical case on tooth 47 highlights the effectiveness of the Deep Margin Elevation (DME) technique for managing subgingival cervical margins. After caries removal, the proximal box margin extended beyond the cemento-enamel junction, making conventional adhesive isolation impossible.

The dentin surface preparation protocol followed precise parameters to optimize adhesion in this critical area:

• Phosphoric acid etching (37.5%): Limited to 5 seconds to avoid any excessive demineralization of the subgingival dentin and cementum.
• Application of the universal adhesive (containing 10-MDP): Active scrubbing for 20 seconds.
• Light-curing: 20 seconds, in accordance with the manufacturer's recommendations.

The margin relocation was performed using a "bulk-fill" composite resin. The reported clinical observations are summarized below:

The procedure allowed for the transformation of a complex cavity into an isolable preparation, providing a stable base for the subsequent restorative treatment. The use of bulk-fill composite facilitated the management of the proximal box depth while ensuring efficient polymerization of the cervical increment.

Analysis of clinical relevance and limitations

The results of this clinical case demonstrate that Deep Margin Elevation (DME) transforms a complex clinical situation into a predictable restorative protocol. For this mandibular second molar (47), the use of a bulk-fill resin allowed for the relocation of the cervical margin to a supragingival position, facilitating rubber dam isolation and digital impression taking. This approach offers a direct alternative to invasive procedures such as surgical crown lengthening, which can compromise the crown-to-root ratio of teeth already weakened by endodontic treatment.

Technical success here relies on precise choices: the use of PTFE tape to perfect the seal of the sectional matrix and a reduced etching time of 5 seconds on the cervical dentin to prevent alteration of this fragile substrate. By moving the restoration margin rather than the periodontium, the practitioner preserves the epithelial-connective attachment while radically simplifying the management of excess cement during the placement of the lithium disilicate overlay.

However, the limitations of this case report lie in its single sample size (n=1) and the lack of long-term clinical follow-up presented. While current data suggest good periodontal health, the durability of the adhesive interface in the subgingival environment remains dependent on rigorous implementation. Compared to orthodontic extrusion options, which are slower and more costly, DME stands out as an immediate and conservative solution for tissue preservation in the dental practice.

Rehabilitation of the 47: DME as an alternative to invasive surgery

This case report of a 38-year-old patient demonstrates the efficacy of Deep Margin Elevation (DME) for managing a subgingival margin on a molar (47) following bonding failures. By using a 2 mm increment of bulk-fill composite, the technique allowed for the relocation of the margin to a supragingival position, making isolation and digital impression possible for the final placement of a lithium disilicate overlay.

In concrete terms, for the practitioner:

• Optimize cervical sealing: Insert PTFE tape (Teflon) to perfect the adaptation of the sectional matrix against the deep margin and prevent any interposition of the rubber dam during bonding.
• Master dentin etching: On these enamel-free margins, reduce the application of phosphoric acid to 5 seconds to avoid excessive demineralization of the cementum and dentin, promoting the effectiveness of the universal adhesive (10-MDP).
• Prioritize tissue preservation: DME avoids invasive crown lengthening on an already weakened tooth, while ensuring rigorous visual control during the removal of excess cement from the indirect restoration.

Technical lexicon of the study

Deep Margin Elevation (DME): A conservative technique consisting of coronally repositioning a subgingival cervical margin using a composite resin base, thus allowing the margin of the final restoration to be located in a supra-gingival position.

10-MDP: Functional monomer (10-methacryloyloxydecyl dihydrogen phosphate) present in the universal adhesive used, ensuring a stable chemical bond with dental tissues, particularly in the dentin and cementum.

Bulk-fill (composite): Resin restoration material allowing the placement of thick increments (here 2 mm for the cervical floor) thanks to optimized polymerization kinetics throughout the entire depth of the layer.

Surgical crown lengthening: Invasive surgical crown lengthening procedure aimed at exposing the cavity margins by apically displacing the periodontium, often at the expense of the crown-to-root ratio.

Lithium disilicate: High-strength glass-ceramic used in this case for the fabrication of the overlay, offering mechanical and aesthetic properties suitable for bonded indirect restorations.

PTFE tape: Polytetrafluoroethylene tape used clinically to improve the cervical adaptation of the metal matrix and ensure the sealing of the operative field during margin elevation.

Supracrestal tissue attachment: Biological structure (formerly known as biological width) that the DME technique aims to preserve by avoiding invasive surgical maneuvers at the level of the gingival attachment.

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