Root Coverage Limitations: Cairo Classifications & Anatomical Ceilings

In 2011, Dr. Francesco Cairo and colleagues introduced a modern recession classification system based on objective Clinical Attachment Level (CAL) measurements. This system replaced the older 1985 Miller classification, which relied on the mucogingival junction and was difficult to apply reliably.

Under the Cairo system, recession is divided into three distinct biological categories: Recession Type 1 (RT1) with no interdental attachment loss; Recession Type 2 (RT2) where interdental attachment loss is present but less than or equal to buccal attachment loss; and Recession Type 3 (RT3) where interdental attachment loss is greater than buccal loss.

Interproximal papilla integrity establishes the biological blood supply network required to sustain an advanced surgical flap over avascular denuded root surfaces. When interdental bone and soft tissue are lost, complete coverage cannot be physiologically sustained.

To understand why complete coverage cannot be achieved in RT2 or RT3 defects, think of interdental bone and papillae as tent poles. When a periodontal flap and connective tissue graft are sutured over a denuded root, the graft receives blood supply from three sides: the apical bed and the two lateral interdental papillae.

If the interdental bone has resorbed due to periodontitis, the "tent poles" are lower. The transplanted tissue cannot survive suspended over an avascular root surface higher than the lateral blood supply that feeds it. As a result, the graft can only heal up to the level of the existing interdental attachment.

Orthodontic torque correction may be required prior to soft-tissue grafting if roots protrude significantly beyond the alveolar housing. Bringing the root back into the cancellous envelope improves the recipient vascular bed and maximizes surgical predictability.

When patients with RT2 defects undergo grafting, clinicians re-frame the goals of surgery. While covering 100% of the exposed root may be impossible, grafting still achieves vital structural benefits: creating a thick band of attached keratinized tissue, stopping progressive root exposure, reducing severe hypersensitivity, and facilitating plaque control.

Halting recession and stabilizing the tooth within thick, resilient tissue prevents future tooth loss. Patients should appreciate that a graft that covers 60% to 70% of a root while stabilizing the attachment apparatus is an outstanding clinical outcome in compromised anatomy.

Extensive cervical restorations or deep non-carious cervical lesions must be meticulously smoothed or partially removed before flap advancement. Composite resin margins located subgingivally can inhibit hemidesmosomal epithelial attachment and compromise long-term graft stability.

The primary biological determinant of root coverage predictability is the height of the interproximal bone crest and soft-tissue papilla adjacent to the recession defect. Cairo RT1 defects exhibit intact interdental attachment; because the interdental bone provides a rich vascular bed, 100% root coverage is achievable.

In Cairo RT2 defects, interproximal attachment loss is present but remains less than or equal to the buccal recession depth. In these cases, complete coverage cannot be achieved; the interproximal bone height establishes the biological ceiling up to which the tissue margin can predictably heal.

Cairo RT3 defects exhibit severe interproximal bone loss exceeding the buccal attachment loss. In RT3 sites, root coverage surgery is generally unpredictable and contraindicated for aesthetic purposes; treatment focuses instead on halting ongoing breakdown and preserving tooth longevity through hygiene and maintenance.

Gingival recession frequently coincides with Non-Carious Cervical Lesions (NCCLs)—deep wedge-shaped cervical defects resulting from abfraction, toothbrush abrasion, and chemical erosion. When an NCCL extends deep into root dentin, surgical planning requires an integrated restorative-periodontal approach.

Soft-tissue grafts cannot bridge deep hollowed notches without collapsing into the defect, which impairs blood supply and causes graft necrosis. To resolve this dilemma, clinicians perform combined restorative-periodontal therapy.

The deep apical portion of the notch is smoothed or restored with a micro-hybrid composite or resin-modified glass ionomer flush with the original root contour, leaving a shallow, flat, clean root plane over which the connective tissue graft can safely be advanced and vascularized.